The keyword library.

The dark band of a sarcomere, equal to the length of the myosin filaments.

It does not change length during contraction.

Describes non-living physical or chemical components of an environment.

Examples include temperature and pH.

A non-living factor that affects organisms, such as temperature, light, water or pH.

Usually density-independent.

The first part of the refractory period, about 1 ms, when no new action potential can be generated whatever the stimulus.

Sodium channels cannot reopen.

A graph showing how much light a pigment absorbs at each wavelength.

Compare with the action spectrum at the same wavelengths.

The number of individuals of a species in an area.

Measured as density, percentage cover or frequency.

A pigment other than chlorophyll a that absorbs light and passes the energy to chlorophyll a.

Accessory pigments widen the range of wavelengths absorbed.

The two-carbon acetyl group attached to coenzyme A, which enters the Krebs cycle.

Formed from pyruvate, fatty acids and some amino acids.

The addition of acetyl groups to histones, which loosens DNA packing and switches genes on.

Removing acetyl groups switches genes off.

The neurotransmitter released by parasympathetic neurones at target organs.

Slows the sinoatrial node.

The enzyme in the synaptic cleft that hydrolyses acetylcholine into choline and ethanoic acid.

Inhibited by organophosphates.

A vesicle at the tip of a sperm head containing hydrolytic enzymes.

The enzymes digest the corona radiata and the zona pellucida.

The globular protein that makes up most of the thin filaments, with binding sites for myosin.

Actin slides; it does not shorten.

A brief reversal of the potential difference across the membrane of a neurone, from about −70 mV to about +40 mV.

All or nothing.

A graph showing the rate of photosynthesis at each wavelength of light.

Peaks match the absorption peaks of the pigments.

The minimum energy that reacting particles need for a reaction to occur.

Enzymes lower this energy barrier.

Immunity in which your own immune system makes antibodies and memory cells.

Long-lasting.

Region of an enzyme where a substrate binds and catalysis takes place.

Its shape and chemical properties matter.

Movement of substances across a membrane against a concentration gradient, using energy from ATP or another source.

Proton pumps carry out active transport of protons.

The evolution of many species from one ancestral species, each adapted to a different way of life.

The Galápagos finches are the classic example.

Adenosine diphosphate: the molecule left when one phosphate group is removed from ATP.

ADP + Pᵢ are joined by ATP synthetase to make ATP.

A hormone released by the anterior pituitary that makes the adrenal glands release cortisol.

Abbreviated to ACTH.

Respiration that uses oxygen and breaks glucose down completely to carbon dioxide and water, making a large amount of ATP.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.

The wider arteriole that carries blood into the glomerulus.

Wider than the efferent arteriole.

A polysaccharide from seaweed used to make the gel for DNA electrophoresis.

It forms a mesh of pores.

The clumping together of cells or particles by antibodies.

Each antibody has two binding sites.

The layer of protein-rich cells just inside the testa of a cereal grain, which makes the hydrolytic enzymes at germination.

Gibberellin from the embryo acts on the aleurone layer.

A rapid growth of algae at the surface of water, usually caused by extra nitrate and phosphate.

Blocks light from plants below.

An action potential is either produced at full size or not produced at all.

Stimulus strength is coded by frequency.

One of the different forms of the same gene, differing slightly in base sequence.

Define dominant and recessive in terms of alleles, not genes.

The proportion of all copies of a gene in a gene pool that are one particular allele.

p and q in the Hardy-Weinberg equation are allele frequencies.

The formation of new species from populations separated by a geographical barrier.

Allo means other: other places.

A very toxic, very soluble nitrogenous waste product.

Needs a lot of water to excrete.

The release of ammonium ions from proteins, urea and nucleic acids by decomposers.

Also called putrefaction.

Taking a sample of the fluid around a foetus, at about 15 to 20 weeks, to test foetal cells.

It carries a small risk of miscarriage.

The enzyme that hydrolyses starch to maltose.

Maltase, not amylase, then gives glucose.

Respiration without oxygen, in which only glycolysis makes ATP and pyruvate is converted to lactate or ethanol.

Net 2 ATP per glucose.

Having one or a few chromosomes more or fewer than normal.

Trisomy 21 is an example.

In PCR, cooling to about 55 °C so primers bind to complementary sequences.

Primers bind at the 3′ end of each strand.

Having opposite effects on the same organ.

The two divisions of the autonomic nervous system are antagonistic.

Two muscles that move a joint in opposite directions, one contracting while the other relaxes.

Biceps and triceps at the elbow.

An array of protein and pigment molecules in the thylakoid membrane that transfers energy from light of a range of wavelengths to chlorophyll a at the reaction centre.

Energy, not electrons, is passed through it.

The part of a stamen that contains the four pollen sacs, in which pollen grains are made.

Two lobes, each with two pollen sacs, gives four in all.

A substance, first made by microorganisms, that kills bacteria or stops them growing without harming human cells.

Antibiotics do not affect viruses.

A protein (immunoglobulin) made by plasma cells that binds to one specific antigen.

Antibodies have two heavy and two light chains.

A peptide hormone that makes the walls of the DCT and collecting duct more permeable to water.

ADH for short.

A molecule, usually a protein on a cell surface, that triggers an immune response and the production of antibodies.

Antigens are on the pathogen; antibodies are made by you.

The display of a pathogen's antigens on the surface of a cell, such as a macrophage, so that lymphocytes can recognise them.

Starts the specific immune response.

Small, gradual changes in a virus's surface antigens caused by mutation.

Causes seasonal flu and the need for a yearly vaccine.

A sudden major change in a virus's antigens when two subtypes mix their genetic material in one cell.

Can cause pandemics.

Forms of the same pathogen that have different surface antigens.

Many antigenic types make a vaccine harder to design.

One of the three nuclei at the end of the embryo sac furthest from the micropyle.

They take no part in fertilisation.

A short nucleic acid complementary to a section of mRNA or pre-mRNA, which binds to it.

Also called a molecular patch.

The fluid-filled space that forms inside a developing ovarian follicle.

Its presence distinguishes a maturing follicle from a primary follicle.

Loss of the ability to produce or understand language, caused by brain damage.

Broca's aphasia and Wernicke's aphasia.

Programmed cell death.

p53 triggers apoptosis when DNA damage cannot be repaired.

The girdles and limbs attached to the axial skeleton.

Pectoral girdle and forelimb; pelvic girdle and hind limb.

The farming of fish and other aquatic organisms in ponds, enclosures or cages.

Also called fish farming.

A channel protein in a cell membrane that lets water molecules through.

Inserted in response to ADH.

A layer of rock underground that holds water.

Pumped faster than rain can refill it in many regions.

A group of single-celled prokaryotes that are different from bacteria, for example in having no peptidoglycan in their cell walls.

Archaea are not stained by the Gram stain in the same way as bacteria.

A bundle of nerve fibres linking Wernicke's area and Broca's area.

Damage stops a person repeating words.

The hyaline cartilage covering the ends of bones in a synovial joint.

It reduces friction and absorbs shock.

A dye that accepts hydrogen (electrons) from dehydrogenases in place of the natural coenzymes, changing colour when reduced.

Examples: methylene blue, DCPIP and TTC.

Working methods that prevent contamination of cultures and of the person working.

Needed for every antibiotic test.

An area of cortex that interprets information, links it with memories and plans responses.

Most of the cortex is association area.

A microscopic particle suspended in the atmosphere, produced by combustion and by dust from digging and quarrying.

No boundary has been quantified for aerosols.

Adenosine triphosphate, the molecule that supplies energy in small amounts for reactions in cells.

Hydrolysis of ATP releases 30.6 kJ mol⁻¹.

An enzyme in the inner mitochondrial membrane through which protons flow down their gradient, using their energy to make ATP.

Also called ATP synthase.

Weakened, so that a live pathogen in a vaccine does not cause disease.

MMR and BCG are live attenuated vaccines.

The area on the upper edge of the temporal lobe that receives impulses from the ears.

Taken over for signing in people deaf from birth.

A sealed container that sterilises equipment using steam under pressure, usually at 121 °C for 15 minutes.

It kills all microorganisms, including spores.

A disease in which the immune system attacks the body's own tissues.

Rheumatoid arthritis is autoimmune; osteoarthritis is not.

Taken from the same person who will receive them.

Autologous cells are less likely to be rejected.

The part of the peripheral nervous system that controls internal organs without conscious control.

It has sympathetic and parasympathetic divisions.

Any chromosome that is not a sex chromosome.

Humans have 22 pairs of autosomes. Autosomal means on an autosome.

The skull, vertebral column, ribs and sternum.

It runs down the midline of the body.

The long process of a neurone that carries impulses away from the cell body.

Can be over a metre long.

A rod shaped bacterium. The plural is bacilli.

Describe bacilli as rod shaped, not cylinders.

The normal rate at which species become extinct without human influence, about one species in a million each year.

Written as 10⁻⁶ per year.

Describing an antibiotic that kills bacteria.

Penicillin is bactericidal.

Describing an antibiotic that stops bacteria growing and dividing without killing them.

Tetracycline is bacteriostatic.

The fibrous waste left after sugar or starch crops have been crushed.

Burned to provide heat for distillation.

A thin layer of protein fibres between the capillary endothelium and the podocytes that acts as the main filter.

Holds back large proteins.

A vaccine against TB made from a weakened strain of Mycobacterium bovis.

Less effective in adults than in children.

Separation of populations whose courtship behaviour is not recognised by each other.

Grasshopper songs are an example.

An enzyme made by some resistant bacteria that breaks down penicillin.

Also called penicillinase.

Having two peaks.

A bimodal distribution suggests disruptive selection.

Asexual reproduction in which one bacterial cell copies its DNA and divides into two identical cells.

In ideal conditions some bacteria divide about every 20 minutes.

A fuel made by reacting vegetable oils with an alcohol, commonly methanol, to produce methyl esters.

Usually blended with fossil diesel.

Ethanol made by fermenting the carbohydrates of sugar or starch crops, and mixed with petrol.

Distilled using heat from burning bagasse.

A fuel made by a biological process, such as anaerobic digestion, rather than by geological processes.

Its carbon was removed from the air recently.

A mixture of roughly 60% methane and 40% carbon dioxide, produced by bacterial digestion of biodegradable waste.

The last stage is methanogenesis.

The planetary boundary concerned with the cycling of elements such as nitrogen and phosphorus.

Crossed for both cycles because of fertiliser use.

The mass of living material, usually measured as dry mass per unit area.

Dried to constant mass.

The planetary boundary concerned with how ecosystems function, previously called biodiversity loss and species extinction.

A core boundary that has been crossed.

Describes living components of an environment or influences arising from organisms.

Competition and predation are biotic influences.

A living factor that affects organisms, such as competition, predation or disease.

Usually density-dependent.

The number of new individuals produced in a population in a given time.

Stable population: birth rate + immigration = death rate + emigration.

The fluid-filled cavity inside a blastocyst.

Its formation turns a morula into a blastocyst.

A hollow ball of cells with an outer trophoblast, an inner cell mass and a fluid-filled blastocoele.

It is the stage that implants in the endometrium.

A further dose of a vaccine that causes a secondary response and makes more memory cells.

Raises antibody levels again.

The cup-shaped start of the nephron that surrounds the glomerulus and collects filtrate.

Its inner wall is made of podocytes.

The concentrated sodium chloride solution left after desalination.

Denser than sea water, so it sinks and damages the seabed.

An inherited disorder in which a collagen gene mutation makes bones fracture very easily.

Also called osteogenesis imperfecta.

Describing an antibiotic that works against many kinds of bacteria.

Tetracycline is broad spectrum.

A motor area in the frontal lobe of the left hemisphere that plans speech.

Damage causes slow, effortful speech.

The fuzzy edge formed by many microvilli on the cells lining the PCT.

Seen in light micrographs.

A crop containing a gene from Bacillus thuringiensis for a protein toxic to insects.

Examples are Bt maize, Bt cotton and Bt tomatoes.

A solution that resists changes in pH.

Used because carbon dioxide lowers pH.

The cycle of reactions in the stroma in which carbon dioxide is fixed, GP is reduced and RuBP is regenerated.

Named after Melvin Calvin.

The outermost whorl of a flower, made up of the sepals.

Its job is to protect the flower while it is in bud.

Tiny channels in bone linking lacunae with each other and with the Haversian canal, containing tissue fluid.

Substances diffuse to bone cells through them.

Changes to the sperm's cell membrane in the female tract that allow the acrosome reaction to happen.

Cholesterol and glycoproteins are removed and the tail beats harder.

The protein coat around the nucleic acid of a virus.

Capsid proteins are made by the host cell's ribosomes.

Breeding endangered species in zoos or botanic gardens, with records of matings so that parents can be chosen.

Choosing parents keeps genetic diversity high.

The incorporation of carbon from carbon dioxide into an organic molecule.

In the Calvin cycle, CO₂ + RuBP → 2 GP.

The total greenhouse gas emissions caused by an activity, expressed as carbon dioxide.

Fish farming has a lower carbon footprint than farming mammals.

An agent that causes cancer.

Many carcinogens are mutagens.

A yellow or orange accessory pigment, such as β-carotene or a xanthophyll, that absorbs blue and blue-green light.

Carotenoids absorb no red light.

The female part of a flower: stigma, style and ovary.

It is the whole female structure, not just the ovary.

An infected person or animal that shows no symptoms but can pass the pathogen on.

Do not confuse with vector.

The largest population that an environment can support for a long time.

Set by biotic and abiotic factors.

A firm, flexible connective tissue of chondrocytes in a matrix containing collagen and, in some types, elastic fibres.

It has no blood vessels, so it heals slowly.

A group within an insect colony that carries out particular tasks.

Queen, drones and workers in honeybees.

Describes reactions that break large molecules down into smaller ones, releasing energy.

Anabolic reactions build large molecules.

A substance that increases reaction rate without being used up overall.

It does not supply the reaction’s energy.

The part of a neurone that contains the nucleus.

Contains Nissl granules.

The part of the specific immune response carried out by T cells through direct contact with target cells.

Destroys infected and cancerous cells.

The narrow channel in the centre of the spinal cord, filled with cerebrospinal fluid.

Found in the middle of the grey matter.

The brain and spinal cord.

Abbreviated to CNS.

The deep groove between the frontal and parietal lobes; the motor cortex is in front of it and the sensory cortex behind it.

Use it to locate the motor and sensory strips.

The part of the hindbrain that coordinates voluntary movement, balance and posture.

It makes movements smooth and precise.

The folded outer layer of grey matter of the cerebrum, 2 to 4 mm thick.

Folding increases its surface area.

One of the two halves of the cerebrum, each controlling the opposite side of the body.

Language is usually in the left hemisphere.

Fluid in the ventricles and around the brain and spinal cord that cushions them and supplies nutrients.

Made by cells lining the ventricles.

The largest part of the brain, made of two hemispheres, responsible for conscious thought, voluntary actions, learning, memory, language and personality.

Do not confuse it with the cerebellum.

The ring of muscle at the neck of the uterus, opening into the vagina.

Stretching of the cervix triggers oxytocin release at birth.

A modified nucleotide that stops DNA synthesis when it is added; in sequencing each carries a coloured label.

It is what makes fragments of every possible length.

The flow of protons down their electrochemical gradient through ATP synthetase, coupled to ATP synthesis.

Protons flow from the intermembrane space into the matrix.

A chemical released by the ovule that a pollen tube grows towards.

The tube grows down the concentration gradient of the chemoattractant to the micropyle.

A statistical test that compares observed counts in categories with the counts expected from a hypothesis.

Use raw counts, never percentages.

A point where chromatids of homologous chromosomes cross and exchange material during meiosis.

The plural is chiasmata.

A halogenated hydrocarbon once used as a propellant, solvent and refrigerant, which releases chlorine free radicals in the stratosphere.

Manufacture banned by international agreement in 1987.

The main photosynthetic pigment, which absorbs blue-violet and red light and is found at every reaction centre.

Only reaction centre chlorophyll a releases electrons.

An accessory pigment that absorbs blue and orange-red light.

Found in the antenna complex.

The organelle in which photosynthesis takes place, surrounded by a double membrane and containing thylakoids and stroma.

Chloroplasts are transducers.

Yellowing of leaves because not enough chlorophyll is made.

Caused by lack of nitrate or magnesium, among other things.

A container divided into areas with different conditions, used to see where small animals go.

Gauze keeps animals off the chemicals.

A disease of the small intestine caused by the bacterium Vibrio cholerae, spread in contaminated water.

Treat with rehydration; prevent with clean water.

A synapse that uses acetylcholine as its neurotransmitter.

The standard example in exams.

A cartilage cell, found in a lacuna in the matrix it secretes.

Chondrocytes are nourished by diffusion.

The membrane formed from the trophoblast that makes the foetal part of the placenta.

Its villi project into the mother's blood.

A finger-like projection of the chorion that contains foetal capillaries and is bathed in maternal blood.

Its wall is one cell thick.

Taking a small sample of placental tissue, at about 10 weeks, to test foetal DNA.

Earlier than amniocentesis.

DNA and associated proteins that form chromosomes in a eukaryotic cell.

It can be more or less condensed.

A technique that separates the substances in a mixture as a solvent moves through a stationary phase such as paper.

Used to separate chloroplast pigments.

A change in the structure of a chromosome or in the number of chromosomes.

Down's syndrome is the example named in the specification.

Learning to associate a neutral stimulus with an unconditioned stimulus, so the neutral stimulus alone produces the response.

Pavlov's dogs.

The series of mitotic divisions of a zygote in which the cells divide but do not grow in between.

The ball of cells stays the same size as the zygote.

Long-term changes in temperature, rainfall and weather patterns.

Shifts species distribution and can cause extinction.

The stable final community of succession, in equilibrium with its environment.

Oak woodland in much of lowland Britain.

Repeated mitosis of a selected lymphocyte to make a clone of identical cells.

Much faster in a secondary response.

The activation of the one lymphocyte whose receptors are complementary to a particular antigen.

Followed by clonal expansion.

A period of the year when fishing for a species is prohibited so that it can breed.

Raises the rate at which the stock is replaced.

When colonies on a crowded plate grow into each other so individual colonies cannot be counted.

Clumping leads to an underestimate of numbers.

A member of the Cnidaria, simple aquatic animals such as Hydra, jellyfish and sea anemones.

They have a nerve net and no brain.

Movement of one substance across a membrane coupled to another, such as glucose moving in with sodium ions.

Driven by the sodium gradient.

A spherical bacterium. The plural is cocci.

Describe cocci as spherical, not round or circular.

A relationship between two alleles in which both are expressed in the heterozygote.

It gives a 1 : 2 : 1 phenotype ratio in the F2.

Describing alleles that are both expressed in the heterozygote.

With codominant alleles, count allele frequencies directly.

A small organic molecule that helps an enzyme work, often by carrying atoms such as hydrogen between reactions.

NAD, FAD and coenzyme A are coenzymes.

A coenzyme that carries the two-carbon acetyl group into the Krebs cycle.

Released and reused when acetyl CoA enters the cycle.

The protective sheath around the plumule of a cereal seedling.

It does the job that the hook does in a broad bean.

A fibrous structural protein with high tensile strength.

In bone it forms about 30% of the matrix and gives flexibility.

The tube that receives filtrate from several nephrons and carries it through the medulla to the pelvis.

Main target of ADH.

A visible group of genetically identical cells that grew from a single bacterium or fungal spore.

Viable counts assume each colony came from one living cell.

An instrument that measures how much light of a particular colour passes through, or is absorbed by, a solution.

Removes the subjectivity of judging a colour change by eye.

An ancestral species from which two or more later species are descended.

Similar structures suggest a common ancestor.

All the populations of different species living and interacting in the same place at the same time.

Living organisms only.

Dense bone forming the outer layer of bones, built of Haversian systems.

Contrast spongy bone, a lattice of struts.

The light intensity at which the rate of photosynthesis equals the rate of respiration, so there is no net gas exchange.

Lower in shade plants than in sun plants.

Inhibition involving competition with substrate for an enzyme’s active site.

Increasing substrate concentration can reduce its effect.

A molecule with a similar shape to the substrate that binds to the active site and blocks it.

Malonic acid inhibits a Krebs cycle dehydrogenase.

DNA made from an mRNA template by reverse transcriptase.

It has no introns. Abbreviated to cDNA.

A culture medium that contains all the chemicals needed to support growth.

Nutrient agar is a complete medium for many common bacteria.

Imaging that combines many X-ray images into cross-sectional slices.

Abbreviated to CT; shows structure.

A difference in the concentration of a substance between two regions.

State which substance you mean.

A variable that changes alongside the one being investigated and could explain the result.

Reduces confidence in a conclusion.

The block of parenchyma joining the two lobes of an anther, containing the vascular strand.

It carries sucrose, mineral ions and water to the developing pollen.

A tissue of cells spread out in a matrix of protein fibres and ground substance that the cells secrete.

Cartilage and bone are both connective tissues.

The sensible management of the biosphere to maintain habitats and enhance biodiversity while allowing human activity.

Its biological aim is to maintain genetic diversity.

Dialysis that uses the patient's own peritoneum as the membrane, with fluid run into the abdomen.

CAPD for short.

Variation in which individuals show a complete range of values between two extremes.

Polygenic and strongly affected by the environment; shown as a histogram.

A separate test set up in the same way but without the factor thought to cause the effect.

Boiled and cooled milk should produce no colonies.

A factor kept the same so that it cannot affect the results.

Incubation temperature and time are controlled variables in the milk practical.

The part of a control system that compares information with the set point and sends instructions to effectors.

For example, the hypothalamus.

Cutting a tree close to the ground and leaving the stool so that new poles grow from it.

A long rotation time increases sustainability.

The loss of colour from corals when the zooxanthellae leave them.

The coral is not dead until the zooxanthellae fail to return.

A planetary boundary whose crossing would drive the Earth into a new and unpredictable state.

Climate change and biosphere integrity.

The whorl of petals inside the calyx.

In an insect-pollinated flower the corolla is the part that attracts the pollinator.

The layer of follicle cells that surrounds a secondary oocyte after ovulation.

It lies outside the zona pellucida.

A thick band of nerve fibres (white matter) that joins the two cerebral hemispheres.

It lets the hemispheres communicate.

The structure that forms from the remains of a follicle after ovulation and secretes progesterone.

It degenerates if there is no pregnancy.

The outer region of the kidney, containing the glomeruli and convoluted tubules.

Site of ultrafiltration.

A small vesicle just under the cell membrane of a secondary oocyte, containing enzymes.

The granules rupture in the cortical reaction.

The release of enzymes from cortical granules, which hardens the zona pellucida into a fertilisation membrane.

It prevents polyspermy.

A hormone released by the hypothalamus that makes the anterior pituitary release ACTH.

Abbreviated to CRH.

A stress hormone released by the adrenal glands that raises blood glucose.

Controlled by negative feedback through the hippocampus.

A seed leaf. In a non-endospermic seed it holds the food store.

Broad bean has two; maize has one, the scutellum.

The arrangement of the two limbs of the loop of Henle, with flow in opposite directions, that builds a large solute gradient in the medulla.

Needs active transport in the ascending limb.

Behaviour by which animals attract and choose a mate of the same species.

Ensures fertile offspring.

A store in muscle that passes phosphate to ADP to make ATP quickly without oxygen.

The specification calls it creatinine phosphate.

A gene editing tool in which the enzyme Cas9, guided by RNA, cuts DNA at a chosen sequence.

Used to correct faulty alleles.

The folds of the inner mitochondrial membrane, which hold the electron transport chain and ATP synthetase.

Folding gives a large surface area.

A window of time when the brain needs a particular stimulus to develop a skill normally.

Language, especially grammar, is roughly 0 to 5 years.

The value of a test statistic at a chosen probability, used to decide whether to accept or reject the null hypothesis.

For a t test with 38 degrees of freedom at p = 0.05 it is 2.02.

Growing different crops in a field in successive years, often including legumes.

Legumes add fixed nitrogen.

The link formed when a myosin head binds to actin.

ATP is needed to break it.

Pollen carried to the stigma of a different plant of the same species.

It increases genetic variation and widens the gene pool.

The exchange of lengths of DNA between chromatids of homologous chromosomes in prophase I of meiosis.

It makes new combinations of alleles, not new alleles.

A tumour-like swelling on a plant caused by Agrobacterium tumefaciens.

Caused by genes from the Ti plasmid.

The purple primary stain used first in the Gram stain. It stains all bacteria purple.

Gram-negative bacteria lose this stain during decolourising.

A liquid or solid mixture that provides the nutrients and conditions microorganisms need to grow.

The plural is media.

A solution of mineral ions in which plants are grown to test the effect of each nutrient.

A complete solution is the control.

A poison that stops cytochrome oxidase passing electrons to oxygen, so the electron transport chain stops.

Fatal because too little ATP is made.

Making ATP as excited electrons from PSI pass along carriers and return to PSI.

Produces ATP only; no reduced NADP or oxygen.

An autosomal recessive disorder in which faulty CFTR channels cause thick, sticky mucus.

Treated experimentally by gene therapy with liposomes.

A signalling molecule released by cells such as T helper cells that stimulates other immune cells.

Cytokines activate B cells and phagocytes.

The fluid component of cytoplasm in which cellular structures are suspended.

Cytoplasm also includes structures outside the nucleus.

A blue dye that becomes colourless when reduced, used as an artificial electron acceptor.

Used in the Hill reaction with isolated chloroplasts.

The removal of the amino group from an excess amino acid, as ammonia, in the liver.

Produces ammonia, which becomes urea.

The phase when numbers fall because death rate exceeds birth rate, for example when nutrients run out and toxic waste builds up.

Seen in closed cultures.

An enzyme that catalyses decarboxylation, releasing carbon dioxide.

Named for the reaction it catalyses.

The removal of a carboxyl group from a molecule, releasing carbon dioxide.

Happens in the link reaction and twice in the Krebs cycle.

A solvent, such as alcohol or acetone-alcohol, that removes crystal violet from Gram-negative bacteria in the Gram stain.

This is the stage at which the two types first look different.

A bacterium or fungus that breaks down dead organic matter by secreting enzymes and absorbing the products.

Saprotrophic nutrition.

A culture medium in which every ingredient and its amount is known.

Contrast with undefined media containing extracts.

The large-scale removal of forest.

Causes soil erosion, flooding, loss of habitat and a rise in carbon dioxide.

The feature of the genetic code that most amino acids are coded for by more than one triplet.

It is why some substitutions are silent.

For a t test comparing two samples, n₁ + n₂ − 2.

Use it to find the critical value.

The splitting open of a mature anther to release its pollen.

It happens because the fibrous layer dries and shrinks, putting the wall under tension.

An enzyme that removes hydrogen atoms from a substrate.

One of the two enzyme names you need in respiration.

The removal of hydrogen atoms from a molecule, catalysed by a dehydrogenase.

The substrate is oxidised and the hydrogen acceptor is reduced.

A local group of interbreeding individuals within a species.

Isolated demes can become separate species.

Damage to or loss of the myelin sheath.

Slows conduction and increases oxygen use.

In PCR, heating DNA to 95 °C so the hydrogen bonds break and the strands separate.

Only hydrogen bonds between bases break.

A short branch of a neurone that carries impulses towards the cell body.

Axons carry impulses away.

The conversion of nitrate to nitrogen gas by anaerobic bacteria in waterlogged soil.

Removes nitrate, so the soil loses fertility.

A factor whose effect on a population increases as population density increases.

Competition, predation, disease.

A factor that affects the same proportion of a population whatever its density.

Floods, fire, frost.

The factor measured to see the effect of the independent variable.

In the milk practical it is the number of bacteria per cm³.

The change in potential difference as Na⁺ enter the axon and the inside becomes positive.

Na⁺ into the axon, not into the membrane.

The removal of minerals from saline water to produce fresh water.

Does not depend on rainfall, but uses a lot of energy.

Darwin's phrase for the idea that species change over generations from their ancestors.

Explained by natural selection.

The process by which land becomes desert, often after vegetation is removed and rainfall decreases.

Follows deforestation because transpiration stops.

An animal, such as an earthworm, that eats small pieces of dead organic matter.

Increases surface area for decomposers.

A low-dose X-ray scan that measures bone mineral density.

Results are given as a T-score.

A condition in which too little ADH is released or the kidneys do not respond to it, producing large volumes of dilute urine.

Different from diabetes mellitus.

A solution with normal plasma concentrations of glucose and ions but no urea.

Stops glucose being lost.

The ripening of the anthers and the stigma of one flower at different times.

Protandry is anthers first; protogyny is stigma first.

A flowering plant whose seeds have two cotyledons.

Broad bean is a dicotyledon.

The process by which a cell becomes specialised for a particular function.

Stem cells differentiate.

Net movement of particles down their concentration gradient due to random motion.

Particles still move at equilibrium.

A genetic cross that follows the inheritance of two genes at once.

Two double heterozygotes give 9 : 3 : 3 : 1 if the genes are unlinked.

How many times a sample has been diluted, for example 10⁴ for a 10⁻⁴ dilution.

Number per cm³ = colonies ÷ (dilution × volume plated).

Spherical bacteria arranged in pairs.

Diplo means two.

Having two sets of chromosomes, written 2n.

Human body cells are diploid, with 46 chromosomes.

Selection for one extreme, so the mean shifts.

Happens when the environment changes.

Variation in which individuals fall into a few distinct categories with no intermediates.

Usually controlled by one gene, little affected by the environment, shown as a bar chart.

A long-term host of a pathogen, usually with few or no symptoms, that is a constant source of infection.

Birds and pigs are reservoirs of influenza.

The movement of seeds or fruits away from the parent plant.

Dispersal is not pollination. Do not write about anthers in a dispersal question.

A fracture in which the broken ends have moved out of line.

Often needs surgery with metal plates, screws or rods.

Selection for both extremes and against the middle, so the distribution becomes bimodal.

Can lead to sympatric speciation.

The coiled part of the tubule after the loop of Henle, in the cortex.

DCT for short; responds to ADH.

Where individuals of a species are found within a habitat.

Shown by transects and kite diagrams.

A mixture of DNA fragments of known lengths run on a gel to estimate the size of other fragments.

Also called a size marker.

An enzyme that joins DNA fragments by forming phosphodiester bonds in the sugar-phosphate backbone.

It seals the gene into the plasmid.

The addition of methyl groups to cytosine in DNA, which usually switches genes off.

Methylation of a promoter blocks transcription.

A social ranking in which higher-ranking individuals are dominant over lower-ranking ones.

Needs individual recognition.

Describing an allele that is expressed in the phenotype whenever it is present.

A dominant allele is not necessarily the most common one.

A neurotransmitter used in the brain, including in reward pathways.

Reuptake is blocked by cocaine.

A period in which a seed is alive but not growing, with a very low rate of metabolism.

A dormant seed is waiting for a trigger, not unable to germinate.

The root of a spinal nerve that enters the back of the spinal cord and carries sensory neurones.

Has the dorsal root ganglion.

A swelling on the dorsal root containing the cell bodies of sensory neurones.

A ganglion is a group of cell bodies outside the CNS.

The fusion of one male gamete with the oosphere to give a zygote, and of the second male gamete with the polar nucleus to give the primary endosperm nucleus.

Two gametes, each used once.

A condition caused by an extra copy of chromosome 21, usually as a result of non-disjunction.

Its chance rises steeply with the age of the mother.

Fishing with nets suspended from floats to catch fish that live in surface waters.

Traps non-target species such as dolphins and turtles.

Delivering water, with fertiliser, directly to the roots of individual plants.

Uses far less water than spraying.

The mass of a tissue after all its water has been driven off.

Dry mass falls early in germination because respiration loses carbon dioxide.

An X-linked recessive disorder in which no working dystrophin is made, so muscles waste away.

Abbreviated to DMD.

A small floating flowering plant (Lemna) that grows by producing new fronds.

Growth is measured by counting fronds.

A state in which a factor fluctuates slightly but stays within narrow limits around a set point.

Not perfectly constant.

A large protein that holds the membranes of muscle fibres steady.

Absent in Duchenne muscular dystrophy.

A community of organisms interacting with each other and with their abiotic environment.

Can be as small as a rock pool.

The processes carried out by communities of organisms on which the biosphere depends, such as recycling minerals and absorbing carbon dioxide.

The reason biosphere integrity matters.

Responsible travel to natural areas that conserves the environment and improves the well-being of local people.

Funds conservation and gives communities a reason to protect species.

The change in conditions near the boundary of a habitat, which is windier, brighter, warmer and drier than the interior.

Small fragments are mostly edge, so little core habitat remains.

A muscle or gland that brings about a response.

Name the specific muscle or gland if you can.

The narrower arteriole that carries blood out of the glomerulus.

Creates high pressure in the glomerulus.

The percentage of the energy in a substrate that is transferred to ATP.

Efficiency = energy in ATP ÷ energy in glucose × 100.

Example: Aerobic respiration: 40.4%.

The percentage of the energy at one trophic level that is passed to the next.

Energy transferred ÷ energy in previous level × 100.

A difference in both concentration and electrical charge across a membrane.

The proton gradient is an electrochemical gradient and a store of potential energy.

Recording the electrical activity of the brain with electrodes on the scalp.

Abbreviated to EEG.

A molecule that accepts excited electrons from a reaction centre.

Electrons pass from it to the electron transport chain.

A protein in the electron transport chain that accepts electrons (is reduced) and passes them on (is oxidised).

Names of the carriers are not required.

A series of electron carriers and proton pumps in the inner mitochondrial membrane that passes electrons along and uses their energy to pump protons.

Found on the cristae.

A test that uses antibodies linked to an enzyme to detect a particular antigen or antibody by a colour change.

A false negative can occur before antibodies are made.

The large cell inside an ovule that contains eight haploid nuclei, including the female gamete.

It is one cell with many nuclei, not a group of cells.

The movement of individuals out of a population.

Removes individuals, like deaths.

Describes a species with so few individuals remaining that it is in danger of becoming extinct.

The idea of being at risk of extinction must be in the answer.

Always present in an area or population at a steady, predictable level.

Malaria is endemic in parts of Africa.

A gland that secretes hormones directly into the blood.

No ducts.

The lining of the uterus, which thickens each cycle and is shed if there is no pregnancy.

The blastocyst implants in it.

The triploid food store of a seed, formed from the primary endosperm nucleus.

Say food store, not just that it provides nutrients.

Describing a seed in which the endosperm is still present as a separate food store at maturity.

Maize is endospermic; broad bean is non-endospermic.

A count of the ATP made at each stage of respiration from one glucose molecule.

38 ATP in theory for aerobic respiration.

A gradual change in an abiotic factor from one place to another in a habitat.

Down a rocky shore, time exposed to air increases towards the top.

A document predicting the environmental effects of a proposed project before it is built.

Must include the mitigation planned.

Repeated measurement of the quality of the environment, to establish its status and identify trends.

Provides the evidence on which decisions are based.

All the biotic and abiotic factors that limit the growth of a population.

Increases as a population grows.

A biological catalyst, usually a protein, that accelerates a reaction by lowering its activation energy.

Use substrate-specific explanations where relevant.

The temporary association formed when a substrate binds to an enzyme.

The enzyme is released after catalysis.

A large, rapid increase in the usual number of cases of a disease in an area.

Compare it with the usual level of cases.

The coiled tube on the outside of each testis in which sperm mature and are stored.

Sperm gain the ability to swim here.

Changes in gene expression that do not alter the base sequence, such as DNA methylation and histone acetylation.

Can be caused by the environment.

The two-carbon compound formed when pyruvate is decarboxylated in yeast and plants.

Accepts hydrogen from reduced NAD.

The two-carbon product of anaerobic respiration in yeast and plants, formed when ethanal is reduced.

The pathway cannot be reversed.

Describes cells with a membrane-bound nucleus and other membrane-bound organelles.

Animals, plants and fungi are eukaryotes.

Describes a colony with care of others' young, overlapping generations and division of labour into castes.

Ants, bees, wasps and termites.

An increase in the concentration of nutrients in water, leading to algal blooms, decomposition and loss of oxygen.

The decomposers respiring remove the oxygen.

A change in the allele frequencies of a population over generations.

Individuals do not evolve; populations do.

Conservation of individuals, gametes or seeds away from the natural habitat, for example in a zoo or seed bank.

Ex situ means out of that place.

An electron that has been raised to a higher energy level, so it carries potential energy.

Light excites electrons in chloroplasts; reduced coenzymes supply them in mitochondria.

An area where fishing is prohibited, monitored by satellite and enforced with fines.

Acts as a reserve where fish breed and grow.

The removal from the body of waste products of metabolism.

Not the same as egestion.

The tough, sculptured outer wall of a pollen grain, made of sporopollenin.

Describe it as rough or sculptured, never as sticky.

Release of substances from a cell when a vesicle fuses with the cell surface membrane.

How acetylcholine is released.

A section of a gene that is kept in the mature mRNA and codes for part of the protein.

The dystrophin gene has 79 exons.

A treatment in which an antisense oligonucleotide makes a chosen exon be left out of the mRNA, restoring the reading frame.

Gives a shorter, partly working protein.

The phase of growth when numbers increase faster and faster because resources are plentiful and birth rate far exceeds death rate.

Appears as a straight line on a log scale.

The permanent loss of a species, when no individuals of it are alive anywhere in the world.

Say 'none left anywhere', not just 'very few left'.

A scale on a glass disc placed in the eyepiece of a microscope, used to measure a specimen.

Its divisions are eyepiece units and mean nothing until it is calibrated.

The first generation of offspring from a cross between two parents.

The F2 comes from crossing F1 individuals with each other.

Passive movement down a concentration or electrochemical gradient through a membrane protein.

No direct ATP input is required.

A blood clotting protein whose gene is on the X chromosome.

A faulty allele causes haemophilia.

A microorganism that grows best with oxygen but can survive and grow without it.

E. coli is a facultative anaerobe.

A coenzyme that accepts hydrogen atoms in the Krebs cycle, becoming reduced FAD.

Only reduced in the Krebs cycle.

A bundle of muscle fibres wrapped in connective tissue.

Many fascicles make up a muscle.

Muscle fibres that contract quickly and powerfully but fatigue fast, relying on anaerobic respiration.

Rich in glycogen and creatine phosphate.

A long hydrocarbon chain with a carboxyl group, split into two-carbon fragments that form acetyl CoA.

Rich in hydrogen, so it releases a lot of energy.

Pores in the endothelium of the glomerular capillaries.

Let plasma through but not blood cells.

Able to produce viable gametes and so to reproduce.

A mule is viable but not fertile.

The hardened zona pellucida formed by the cortical reaction, which no other sperm can penetrate.

The formation of this membrane is the block to polyspermy.

A substance added to soil to supply mineral ions such as nitrate and phosphate.

Excess can cause eutrophication.

The layer of thickened cells just inside the epidermis of an anther, whose drying opens the anther.

Drying, not growth, is what opens the anther.

The response to a threat, produced by the sympathetic nervous system and adrenaline, that prepares the body for action.

Heart rate and ventilation rate rise.

The stalk that holds an anther in position and carries sucrose and water to it.

In a wind-pollinated flower the filament is long and flexible.

A narrow gap between the foot processes of podocytes through which filtrate passes.

Too small for albumin.

The finger-like projections at the funnel of an oviduct that sweep a released oocyte into the tube.

They surround the opening next to the ovary.

The substance that accepts electrons at the end of the electron transport chain; in aerobic respiration it is oxygen, which forms water.

Without it, the chain stops.

When an allele reaches a frequency of 1, so every individual carries only that allele.

Drift can fix or lose alleles in small populations.

An innate, stereotyped sequence of movements triggered by a sign stimulus and usually completed once started.

Abbreviated to FAP.

A radioactive glucose tracer used in PET scans; active cells take up more of it.

Abbreviated to FDG.

A ball of cells in the ovary containing a developing oocyte.

Primary follicle, then a follicle with an antrum, then a Graafian follicle.

A hormone from the anterior pituitary that stimulates follicles to develop and to secrete oestrogen.

It stimulates follicle development; it does not make eggs.

The preserved remains or traces of an organism from the distant past.

Fossil series show gradual change.

Coal, oil or natural gas, formed over millions of years from organisms that did not fully decay.

Combustion releases carbon dioxide.

The unusual allele frequencies of a new population started by a few individuals carrying a chance sample of alleles.

Say: by chance, the founders' alleles differed, and there was no gene flow.

A break in a bone.

Describe it by its shape, whether it is displaced, and whether the skin is broken.

A change in the reading frame caused by adding or deleting bases, so every later triplet is read differently.

Additions and deletions cause frame shifts; substitutions do not.

A highly reactive species with an unpaired electron.

One chlorine free radical destroys about 100 000 ozone molecules.

The percentage of quadrats in which a species is present.

Says nothing about how many individuals.

Water with a low concentration of dissolved salts, below 0.05% by mass.

Fresh is not the same as drinkable.

The front lobe of each hemisphere, for reasoning, planning, personality and movement; contains the motor cortex and Broca's area.

In front of the central sulcus.

The fixed point about which a lever turns; in the body, a joint.

Find the fulcrum first when naming the order of a lever.

MRI that detects changes in blood oxygenation to show which brain areas are active.

Abbreviated to fMRI.

The stalk that attaches an ovule to the ovary wall.

It leaves the hilum scar on the seed.

A haploid sex cell or nucleus that fuses with another gamete at fertilisation.

In a flowering plant both gametes are nuclei, not whole cells.

Separation of species whose gametes cannot fuse.

Common in animals that release gametes into water.

The stage of Plasmodium in human blood that forms gametes once taken in by a mosquito.

Sexual reproduction happens in the mosquito.

A graduated syringe that collects gas so that its volume can be read.

More accurate than counting bubbles.

A method that separates DNA fragments by size by moving them through a gel with an electric current.

Small fragments move furthest.

A length of DNA at a particular locus on a chromosome that codes for a polypeptide.

Do not use gene when the question is about the different forms; those are alleles.

A store of genetic material, such as a zoo population, a sperm bank or a seed bank, kept so that alleles are not lost.

All gene banks are ex situ conservation.

The movement of alleles between populations when individuals or gametes move.

Gene flow keeps gene pools similar; isolation stops it.

All the alleles of all the genes in a population at a given time.

A gene pool belongs to a population, not an individual.

A short labelled single strand of DNA that binds to a complementary sequence so it can be found.

Labels may be fluorescent or radioactive.

Treating a genetic disorder by inserting a functional allele into cells or correcting the faulty one.

Somatic or germ line.

The time between one division of a bacterial cell and the next, which is the time taken for a population in the log phase to double. It is also called the doubling time.

Number of generations = change in log₁₀ number ÷ 0.301, then generation time = time taken ÷ number of generations.

The nucleus of a pollen grain that divides by mitosis into the two male gametes.

One generative nucleus gives two male gametes.

Advice to people about the risk of a genetic condition in themselves or their children.

It helps people make informed decisions.

The variety of alleles present in a population.

Low genetic diversity means a population cannot adapt to change.

Random change in allele frequencies from one generation to the next, strongest in small populations.

Drift is chance, not selection.

A pattern of DNA bands, based on repeated sequences, that is unique to a person apart from identical twins.

Also called a DNA profile.

Testing people, foetuses or embryos for alleles linked to disease.

Includes carrier screening and prenatal testing.

Having DNA changed by gene technology.

A GM organism is transgenic only if the gene comes from another species.

All the DNA in one set of an organism's chromosomes.

The human genome is about 3 billion base pairs.

The silencing of a gene in the gametes of one parent, so only the other parent's copy is expressed.

It is an epigenetic effect that passes between generations.

The study of the structure and function of whole genomes.

Leads to personalised medicine.

The alleles an organism has for a particular gene or genes.

Two organisms with the same genotype can still differ because of the environment.

Separation of populations by a physical barrier such as a mountain, river or sea.

Leads to allopatric speciation.

Gene therapy on gametes or an early embryo, so the change is inherited.

Not allowed in humans in the UK.

The layer of dividing cells that gives rise to gametes: the outer wall of a seminiferous tubule, or the surface layer of an ovary.

It is where multiplication by mitosis happens.

The resumption of growth by the embryo of a seed, up to the point where the seedling can photosynthesise.

It needs water, oxygen and a suitable temperature.

A plant growth substance, also called gibberellic acid, that starts germination and promotes stem elongation.

It is a signal, not an enzyme.

The rise in the Earth's average temperature caused by increased greenhouse gases.

Leads to climate change.

The fluid in the Bowman's capsule, like plasma without the large proteins.

About 180 dm³ per day.

A knot of capillaries inside the Bowman's capsule where blood is filtered.

Plural: glomeruli.

A receptor that binds cortisol; in the hippocampus it triggers negative feedback on cortisol release.

Fewer receptors mean poorer feedback.

A three-carbon compound formed when carbon dioxide is fixed by RuBP.

Abbreviated GP; reduced to triose phosphate.

A three-carbon molecule released when triglycerides are hydrolysed; it is converted to triose phosphate.

Enters glycolysis.

The branched polysaccharide of glucose stored in muscle and liver.

Muscle glycogen is used only by the muscle itself.

The first stage of respiration, in the cytoplasm, in which glucose is split into two pyruvate, with a net gain of 2 ATP and 2 reduced NAD.

Does not need oxygen.

A hormone from the hypothalamus that stimulates the anterior pituitary to secrete FSH and LH.

It sits above FSH and LH in the control chain.

A mature ovarian follicle with a large fluid-filled antrum and the oocyte to one side.

It bulges from the surface of the ovary before ovulation.

A staining technique that colours bacteria purple (Gram-positive) or pink (Gram-negative) depending on their cell wall structure.

Stages: crystal violet, iodine, alcohol decolouriser, safranin counter-stain.

Describing bacteria with a thin peptidoglycan layer and an outer membrane, which stain red in the Gram stain.

The outer membrane keeps out many antibiotics.

Describing bacteria with a thick peptidoglycan wall and no outer membrane, which stain purple in the Gram stain.

More easily reached by penicillin.

A stack of thylakoids in a chloroplast.

The plural is grana.

The warming of the Earth because greenhouse gases absorb and re-radiate infrared radiation.

Natural; the enhanced effect causes global warming.

A gas that absorbs and re-radiates infrared radiation, warming the Earth.

Carbon dioxide, methane and oxides of nitrogen.

A fracture in which the bone bends and cracks on one side only, common in children.

Children's bones are more flexible.

Nervous tissue made mainly of neurone cell bodies, without myelin.

In the cerebrum it is on the outside.

The rate at which producers convert light energy into chemical energy in organic molecules.

GPP = NPP + R.

Substances such as vitamins and mineral ions that bacteria need in small amounts for growth.

Examples include biotin and ions such as Mg²⁺ and PO₄³⁻.

The central region of the A band containing only myosin.

It shortens and may disappear during contraction.

The place where an organism lives.

Not the same as an ecosystem.

The division of a large habitat into smaller, separated pieces by roads, fields or development.

Fragments hold small, isolated populations.

The destruction or degradation of the place where a species lives, so that food, shelter and breeding sites are removed.

The most important cause of species becoming endangered.

Learning to ignore a repeated stimulus that is followed by neither reward nor punishment.

Saves energy.

A surface antigen of the flu virus that lets it enter host cells.

The H in names such as H1N1.

Removing urea and excess ions and water by passing the blood through a machine with a partially permeable membrane.

Counter-current flow of dialysis fluid.

An X-linked recessive condition in which a clotting protein, factor VIII, is missing or faulty, so blood clots very slowly.

Affected males are XʰY.

Having one set of chromosomes, written n.

Pollen grains and the embryo sac are haploid.

p² + 2pq + q² = 1, giving genotype frequencies from allele frequencies p and q, where p + q = 1.

Start from q², the recessive phenotype.

The idea that allele and genotype frequencies stay constant from generation to generation if certain conditions are met.

Its conditions are the opposite of the causes of evolution.

The central channel of a Haversian system, containing an arteriole, a venule, lymph vessels and nerves.

Do not confuse it with the tiny canaliculi.

The unit of compact bone: rings of lamellae around a central Haversian canal carrying blood vessels and nerves.

Also called an osteon.

Passing a dried smear of bacteria through a flame to kill the cells and stick them to the slide.

It stops bacteria washing off during staining.

A line of shrubs and trees between fields, which provides habitat and acts as a wildlife corridor.

Removed to make fields large enough for machinery.

An anticoagulant added to blood during haemodialysis to stop it clotting.

Added before the dialyser.

Protection of a whole population when so many people are immune that a pathogen cannot spread.

About 95% for measles.

Variation caused by differences in alleles, which can be passed to offspring.

Only heritable variation can be selected.

The sex that makes two kinds of gamete for the sex chromosomes; in humans the male.

The female is the homogametic sex.

A situation in which heterozygotes survive and reproduce better than either homozygote, keeping both alleles in the gene pool.

Sickle cell trait in malarial regions is the example.

Having two different alleles of a gene.

A heterozygote shows the dominant phenotype unless the alleles are codominant.

Having six sets of chromosomes, written 6n.

Bread wheat is hexaploid, 6n = 42.

A six-carbon sugar with two phosphate groups, formed when glucose is phosphorylated by two ATP in glycolysis.

More reactive than glucose.

The release of oxygen and reduction of an electron acceptor, such as DCPIP, by isolated chloroplasts in light.

Shows that the light-dependent stage does not need carbon dioxide.

The scar on the edge of a seed where the funicle was attached.

The micropyle is the tiny pore beside it.

A curved structure on the inner side of each temporal lobe, involved in learning, spatial memory and consolidating memories.

Say it consolidates short-term memories into long-term memory.

A chemical released by damaged cells that widens blood vessels and makes capillaries leaky.

Causes the redness and swelling of inflammation.

A graph of continuous data grouped into classes, with no gaps between the bars.

Use a bar chart with gaps for categories.

One of the proteins around which DNA is wound to form nucleosomes.

Histone modification changes how tightly DNA is packed.

The maintenance of a constant internal environment within narrow limits.

Conditions fluctuate around a set point.

A pair of chromosomes with the same genes in the same order, one from each parent.

In a hybrid the two sets are not homologous, so they cannot pair.

Having two identical alleles of a gene.

Homozygous dominant is BB; homozygous recessive is bb.

A drawing or model of the body in which each part is shown in proportion to the area of cortex serving it.

Plural homunculi.

An organism that other organisms live in or on.

The human body is host to gut bacteria, skin flora and parasites.

The hypothalamus, pituitary and adrenal glands acting together to control cortisol release.

Stands for hypothalamus, pituitary, adrenal.

A hormone secreted by the trophoblast and then the placenta, which maintains the corpus luteum in early pregnancy.

It is what a pregnancy test detects.

The international project, completed in 2003, that sequenced the human genome and located its genes.

Its aims included improving the diagnosis and treatment of genetic disorders.

The part of the specific immune response carried out by antibodies in the blood and tissue fluid.

Involves B cells and plasma cells.

Dark organic material in soil formed from decomposed dead organisms.

Holds water and mineral ions.

An autosomal dominant disorder in which brain cells degenerate, usually from middle age.

One allele is enough to cause it.

The commonest cartilage, with fine collagen fibres in a smooth, glassy matrix.

It forms articular cartilage and the rings of the trachea.

The offspring of a cross between two different species.

Most animal hybrids are sterile.

When first-generation hybrids are fertile but their offspring are weak or sterile.

Known in cotton and rice.

The death of a hybrid embryo before it can grow and breed.

A post-zygotic mechanism.

The inability of a healthy hybrid to make viable gametes, because its chromosomes cannot pair in meiosis.

The mule is the classic example.

The breakdown of a large molecule into smaller ones by the addition of water.

Amylase hydrolyses starch to maltose, not to glucose.

The pressure exerted by a fluid, here the blood pressure in the glomerular capillaries.

Forces filtrate out.

The calcium phosphate mineral that forms about 70% of the bone matrix.

It makes bone hard and resistant to compression.

A brief overshoot in which the inside becomes more negative than the resting potential.

Potassium channels are slow to close.

Describes a solution that causes a cell to lose water compared with the solution inside it.

It is a comparison, not an absolute property.

A small region of the forebrain below the thalamus that controls homeostasis, the autonomic nervous system and the pituitary gland.

It links the nervous and endocrine systems.

The light band of a sarcomere containing only actin.

It shortens during contraction.

The rapid physical uptake of water by the dry tissues of a seed.

It happens even in a dead seed, because it does not need living cells.

Learning by copying the behaviour of another individual.

Spreads behaviour without genetic change.

The movement of individuals into a population from elsewhere.

Adds to population size, like births.

Able to cause a strong immune response.

A good vaccine is highly immunogenic.

A drug that reduces the activity of the immune system.

Reduces the risk of transplant rejection.

The embedding of a blastocyst in the endometrium of the uterus.

It happens about seven days after fertilisation.

Rapid learning in a critical period soon after hatching or birth, by which young animals attach to a parent.

Studied by Konrad Lorenz in geese.

Conservation of a species in its natural habitat, for example in a nature reserve.

In situ means in the original place.

Fertilisation of oocytes by sperm outside the body.

The embryos made can be screened.

A relationship in which the heterozygote has a phenotype intermediate between the two homozygotes.

Pink flowers from red and white parents are the classic example.

Keeping cultures at a controlled temperature for a set time so microorganisms can grow.

Schools incubate at 25 °C with plates upside down.

The random lining up of homologous pairs at metaphase I, and of chromatids at metaphase II, so gametes get different combinations of chromosomes.

A source of variation in sexual reproduction.

The factor deliberately changed in an investigation.

In the milk practical it is the age of the milk.

A species whose presence, absence or abundance shows the conditions in a habitat.

Lichens indicate air quality; mayfly larvae indicate clean water.

A change in enzyme shape associated with substrate binding that supports catalysis.

The active site is not completely rigid.

An adult cell reprogrammed by adding genes so that it becomes pluripotent.

Abbreviated to iPS cell.

Able to be passed from one individual to another.

Say how it passes, for example in droplets or water.

A local response to damage or infection in which blood flow increases and capillaries leak, bringing phagocytes.

Started by chemicals such as histamine.

A disease of the airways caused by an RNA virus with haemagglutinin and neuraminidase antigens.

A new vaccine is needed every year.

Behaviour that is inborn and instinctive, performed without learning.

Do not define it as inherited.

The clump of cells inside a blastocyst that becomes the embryo and the amnion.

The rest of the blastocyst becomes the placenta.

A wire or plastic loop used to transfer microorganisms. Wire loops are flamed until red hot and cooled before use.

Cooling stops the loop killing the bacteria being transferred.

A phosphate ion that is not part of an organic molecule, written Pᵢ.

Released when ATP is hydrolysed and used when ATP is made.

Solving a new problem suddenly, using previous experience, without trial and error.

Köhler's chimpanzees.

One of the two layers that wrap around an ovule and later harden into the testa.

The gap the two integuments leave is the micropyle.

Sexual selection by one sex, usually females, choosing mates.

Peacocks and bowerbirds.

The narrow space between the outer and inner mitochondrial membranes, into which protons are pumped.

It has a high proton concentration and low pH.

The blood plasma and tissue fluid that surround the body's cells.

Homeostasis keeps its conditions steady.

Competition between individuals of different species.

Two plant species competing for light is interspecific.

A cell in the tissue between seminiferous tubules that secretes testosterone.

Also called a Leydig cell. It is outside the tubule, which is how it differs from a Sertoli cell.

A pad of white fibrous cartilage between the bodies of two vertebrae.

It absorbs shock.

The space in the endometrium, filled with maternal blood, into which the chorionic villi project.

Also called a lacuna.

The thin inner wall of a pollen grain, made of cellulose.

The pollen tube grows out through a pore in the exine, carrying the intine with it.

Sexual selection by competition between members of one sex, usually males.

Elephant seals and red deer.

Competition between individuals of the same species.

Usually the most intense, because they need exactly the same resources.

A species brought by humans to an area where it does not occur naturally, which may outcompete native species.

Also called an alien or invasive species.

A non-coding section of a eukaryotic gene that is removed from the mRNA before translation.

Bacteria cannot remove introns.

The relationship in which light intensity is proportional to 1 ÷ distance² from a small light source.

Halving the distance multiplies light intensity by four.

Radiation, such as X-rays and gamma rays, that can damage DNA and slightly increase cancer risk.

Used in CT and PET, not MRI.

Describes conditions in which a cell has no sustained net gain or loss of water by osmosis.

Water molecules continue moving both ways.

The International Union for Conservation of Nature, which assesses species and places them in threat categories.

Its assessments are published in Red Data Lists.

A nephron with its glomerulus near the medulla and a long loop of Henle.

Common in desert mammals.

The chromosomes of a cell photographed and arranged in pairs in order of size.

It shows a missing or extra chromosome.

A condition in which the kidneys can no longer filter the blood or control water and ions properly.

Treated by dialysis or transplant.

A non-directional response in which an animal's speed or rate of turning changes with the intensity of a stimulus.

Plural kineses.

A diagram showing the abundance of each species at each point along a transect by the width of a shape.

Shows distribution and relative abundance.

A cycle of reactions in the mitochondrial matrix that releases carbon dioxide and makes reduced NAD, reduced FAD and ATP from acetyl CoA.

One turn: 2 CO₂, 3 reduced NAD, 1 reduced FAD, 1 ATP.

An excessive outward curve of the thoracic spine, causing a hunched back.

Scheuermann's kyphosis develops in adolescence.

The product of anaerobic respiration in muscle, formed by reducing pyruvate.

Its formation regenerates NAD so glycolysis continues.

A small space in the matrix of cartilage or bone in which a cell sits.

The plural is lacunae.

The early phase of growth, when numbers rise slowly because there are few individuals and they are adjusting to the environment.

Growth is slow, not zero.

One ring of bone matrix in a Haversian system.

The plural is lamellae.

The planetary boundary measuring the conversion of land to human use, particularly where little food is produced.

Crossed, largely through deforestation.

Learning without reward, by exploring, which is used later.

Tolman's rats in a maze.

The delay between exposure to an antigen and the appearance of antibodies.

Short in a secondary response.

Control of a function, such as language, mainly by one hemisphere.

Language is usually in the left hemisphere.

Mendel's first law: the two alleles of a gene separate when gametes form, so each gamete receives only one.

It is explained by homologous chromosomes separating at anaphase I.

The washing of soluble ions, such as nitrate, out of soil by water.

Carries fertiliser into rivers.

A relatively permanent change in behaviour as a result of past experience.

Includes habituation, imprinting and conditioning.

A pink protein in root nodules that binds oxygen and keeps its concentration low.

Protects nitrogenase.

A plant of the pea family, such as clover, peas or beans, with root nodules.

Used in crop rotation.

A place where males gather to display or fight while females choose mates.

Black grouse form leks.

An allele that causes death, usually when homozygous.

A lethal homozygote removes one class, so 1 : 2 : 1 becomes 1 : 2.

A rigid bar that turns about a fixed point, the fulcrum, when an effort moves a load.

In the body: bone, joint, muscle, body part.

A tough band of connective tissue joining bone to bone across a joint.

Tendons join muscle to bone.

A molecule or ion that binds to a particular site on another molecule.

In signalling, it can bind a receptor.

The stage of photosynthesis on the thylakoid membranes that uses light to split water and make ATP and reduced NADP.

Releases oxygen.

The stage of photosynthesis in the stroma that uses ATP and reduced NADP to fix carbon dioxide and make triose phosphate.

Also called the Calvin cycle.

A group of structures around the thalamus, including the hippocampus, involved in emotion, learning and memory.

The hippocampus is part of it.

The factor in shortest supply, which limits the rate of a process; increasing it increases the rate.

A levelling-off graph means another factor has become limiting.

The reaction in the mitochondrial matrix that converts pyruvate to acetyl CoA, releasing carbon dioxide and reducing NAD.

Happens twice per glucose; no ATP made.

The inheritance of genes together because they are on the same chromosome.

Autosomal linkage is on an autosome; sex linkage is on a sex chromosome.

An enzyme that hydrolyses lipid to fatty acids and glycerol.

Oily seeds rely heavily on lipases at germination.

A molecule of lipid joined to polysaccharide chains, found in the outer membrane of Gram-negative bacteria.

Part of the protective outer layer.

A tiny hollow sphere of phospholipid used to carry DNA into cells.

It fuses with the cell membrane.

A drug that blocks sodium ion channels in sensory neurones so that pain is not felt in one area.

For example lidocaine.

Movements of ions along the axon from a depolarised region to the neighbouring resting region.

They depolarise the next region to threshold.

The fixed position of a gene on a chromosome.

The same locus is found on both chromosomes of a homologous pair.

The phase of a growth curve when bacteria divide at their fastest rate, also called the exponential phase.

Nutrients are plentiful and waste is low.

The power to which 10 must be raised to give a number. log₁₀ of 1000 is 3.

Each increase of 1 on a log₁₀ scale means ten times more.

A scale on which each equal step represents multiplying by the same factor, such as ten.

Convert log values back before calculating.

The hairpin part of the nephron in the medulla that creates a high solute concentration there.

Descending and ascending limbs.

An excessive inward curve of the lumbar spine, giving a hollow back.

Linked to obesity, pregnancy and weak core muscles.

A drawing showing the outlines and positions of tissues, with no individual cells drawn.

A high power drawing shows a few individual cells instead.

A hormone from the anterior pituitary. A surge of LH triggers ovulation and forms the corpus luteum.

The surge is caused by very high oestrogen.

A white blood cell of the specific immune response: a B cell or a T cell.

B cells mature in bone marrow, T cells in the thymus.

The bursting of a cell, for example when water enters a bacterium whose cell wall has been weakened.

Penicillin causes lysis by weakening the peptidoglycan wall.

Virus reproduction in which viral DNA is inserted into a host chromosome and copied with it, without symptoms.

Herpes viruses and HIV can stay hidden like this.

An enzyme in tears, saliva and mucus that breaks down peptidoglycan in bacterial cell walls.

Not the same as a lysosome.

Virus reproduction in which new particles are made at once and released, often by bursting the cell.

Symptoms appear during the lytic cycle.

A large phagocyte that engulfs pathogens and presents their antigens to lymphocytes.

An antigen-presenting cell.

A mineral ion (Mg²⁺) needed to make chlorophyll and to activate enzymes such as ATPase.

Deficiency causes yellowing between the veins of older leaves.

Imaging that uses a strong magnetic field and radio waves to show soft tissue in detail.

Abbreviated to MRI; no ionising radiation.

How many times larger an image is than the real object: magnification = image size ÷ actual size.

Give the answer as ×number, with no units.

A disease caused by the protoctist Plasmodium and carried by the female Anopheles mosquito.

The pathogen is Plasmodium; the mosquito is the vector.

The idea that costly ornaments are honest signals of quality because only fit males can survive with them.

The peacock's tail.

The disaccharide produced when amylase hydrolyses starch.

Examiners report candidates writing glucose here and losing the mark.

The gland in the breast that secretes milk under the control of prolactin.

Oestrogen makes it develop during pregnancy.

A method of estimating the size of a population of mobile animals by marking a sample and recording how many are recaptured.

Population = (n₁ × n₂) ÷ m.

A gene on a vector, such as antibiotic resistance, that shows which cells have taken up the vector.

Insertion into a marker gene inactivates it.

An event in which the great majority of species are lost in a short period of geological time.

Five have happened; a sixth is thought to be under way.

The fluid inside the inner mitochondrial membrane, containing the enzymes of the link reaction and Krebs cycle.

Write 'matrix of the mitochondrion'.

The sum of the values divided by the number of values.

The t test compares two means.

The middle value when the values are put in order.

With an even number of values, average the middle two.

The inner region of the kidney, made of pyramids containing loops of Henle and collecting ducts.

No glomeruli.

The lowest part of the brain stem, containing the centres that control breathing, heart rate and blood pressure.

Contains the cardiovascular and ventilation centres.

Very large animals, many of which became extinct as humans spread across the world.

Examples include a giant flightless bird and a giant ground sloth.

A diploid cell in the nucellus that divides by meiosis, only one of whose four products survives.

The survivor then divides by mitosis three times.

A long-lived B or T lymphocyte that divides rapidly if the same antigen enters the body again.

The basis of long-term immunity.

The three membranes that surround and protect the brain and spinal cord.

Inflammation of them is meningitis.

The cycle of about 28 days in which a follicle matures, an oocyte is released and the endometrium is prepared and then shed.

Day 1 is the first day of bleeding.

The breakdown and loss of the endometrium at the start of a menstrual cycle.

It happens because progesterone falls.

The stage of Plasmodium that infects red blood cells and reproduces asexually inside them.

Released each time infected red cells burst.

The size of the holes in a fishing net, which determines the size of fish caught.

A larger mesh lets immature fish escape and breed.

A series of enzyme-controlled reactions in which the product of one reaction is the substrate for the next.

Respiration is a catabolic pathway.

Water produced by aerobic respiration.

The kangaroo rat's main water source.

The anaerobic stage of biogas production in which methane is produced.

C₆H₁₂O₆ → 3CH₄ + 3CO₂.

Adding methyl groups to DNA, which usually switches genes off.

Less methylation, more expression.

A dye that is blue when oxidised and colourless when reduced, used as an artificial hydrogen acceptor.

Oxygen re-oxidises it, so do not shake the tube.

A living thing too small to be seen clearly without a microscope, including bacteria, Archaea, fungi, protoctists and viruses.

This topic mainly deals with bacteria.

The narrow canal through the integuments of an ovule, through which the pollen tube enters and, later, water is taken in.

It is a gap in the integuments, not a hole in the ovary wall.

Tiny finger-like folds of the cell surface membrane that increase surface area.

Form the brush border.

The lowest concentration of an antibiotic that stops the growth of a bacterium.

Read where the clear zone meets a gradient strip.

The ways in which the negative effects of a project will be avoided or reduced.

Evidence must show it has been considered.

The organelle, surrounded by a double membrane, where the link reaction, Krebs cycle and electron transport chain take place.

Cells with high ATP demand have many.

The value or class that occurs most often.

On a histogram, the modal class is the tallest bar.

A flowering plant whose seeds have one cotyledon.

Maize is a monocotyledon; the scutellum is its single cotyledon.

The agricultural practice of growing a single crop, breed or variety over a large area.

Provides only one habitat, so it reduces species diversity.

Controlled by a single gene.

Monogenic characteristics usually show discontinuous variation.

A genetic cross that follows the inheritance of one gene.

Two heterozygotes give a 3 : 1 phenotype ratio.

A substance that fixes a stain more firmly to cells. In the Gram stain, iodine is the mordant.

Iodine does not change the colour; it helps hold crystal violet in the wall.

Separation of populations whose body or flower structures prevent mating or pollination; also called mechanical isolation.

Left- and right-coiling snails cannot mate.

The solid ball of cells formed by cleavage of a zygote.

It becomes a blastocyst once a cavity forms.

The area of cortex in front of the central sulcus that sends impulses to skeletal muscles.

Controls the opposite side of the body.

A neurone that carries impulses from the CNS to an effector.

Its cell body is in the ventral horn.

Methicillin-resistant Staphylococcus aureus, a bacterium resistant to penicillin and related antibiotics.

Often spread in hospitals.

Able to become only a few related cell types.

Adult bone marrow stem cells are multipotent.

A fall in the force a muscle can produce during activity.

Link it to anaerobic respiration, lactate and lack of ATP.

A single long skeletal muscle cell with many nuclei, formed by the fusion of cells.

A fibre is a cell, not a protein fibre.

An agent that increases the rate of mutation, such as ionising radiation, ultraviolet light or certain chemicals.

Name the mutagen and say what it does to DNA.

A change in the base sequence or structure of DNA, and the only source of new alleles.

Mutations are random; they do not happen because they are needed.

A close relationship between two species in which both benefit.

Rhizobium and legumes.

A lipid-rich insulating layer around an axon, formed by Schwann cells.

Causes saltatory conduction.

A long bundle of thick and thin myofilaments inside a muscle fibre.

Myofibrils give muscle its stripes.

A red protein in muscle that stores oxygen and releases it at low oxygen levels.

Abundant in slow twitch fibres.

The thick layer of smooth muscle in the wall of the uterus.

It contracts during birth.

The protein of the thick filaments, whose heads bind to actin and hydrolyse ATP.

The A band is the length of the myosin filaments.

A coenzyme that accepts hydrogen atoms from substrates in respiration, becoming reduced NAD.

Do not confuse with NADP, used in photosynthesis.

A coenzyme that accepts electrons and protons in the light-dependent stage.

Do not confuse with NAD, used in respiration.

Describing an antibiotic that works against only a small range of bacteria.

Penicillin G mainly affects Gram-positive bacteria.

The process by which individuals with better-suited phenotypes survive and reproduce more, so their alleles increase in frequency.

Link survival to passing on alleles and a change in allele frequency.

A sugary solution secreted by a nectary that attracts and rewards animal pollinators.

Nectar and scent are attractants that a photograph cannot show.

A gland, usually at the base of the petals, that secretes nectar as a reward for pollinators.

Wind-pollinated flowers have no nectaries.

A mechanism in which a change triggers a response that reverses the change.

Keeps cortisol within limits.

The functional unit of the kidney: a tubule that filters blood and adjusts the filtrate to form urine.

About a million per kidney.

A bundle of many neurones surrounded by connective tissue.

Not the same as a neurone.

A simple network of short, branched, non-myelinated neurones spread through the body wall of a cnidarian.

Not 'nervous net'.

The chemical energy in producers' biomass after their respiration; it is available to the next trophic level.

NPP = GPP − R.

A surface antigen of the flu virus that lets new virus particles leave the host cell.

The N in names such as H1N1.

A synapse between a motor neurone and a muscle fibre.

Uses acetylcholine.

A nerve cell, specialised to carry electrical impulses.

Spelt 'neurone' in WJEC papers.

Changes in neural pathways that enable the brain to respond to the environment and compensate for injury or disease.

Explains recovery after a stroke.

A neurone that releases a hormone into the blood, such as ADH from the posterior pituitary.

Links nervous and endocrine systems.

A chemical that carries a signal across a synapse.

For example acetylcholine or dopamine.

The most common phagocyte in the blood.

Arrives first at a site of infection.

Sequencing methods that read millions of short DNA fragments in parallel.

Faster and cheaper than Sanger sequencing.

The role of a species in an ecosystem, including what it eats and the conditions it needs.

More niches support more species.

Groups of ribosomes and rough endoplasmic reticulum in the cell body of a neurone.

Make proteins.

An ion (NO₃⁻) absorbed by plant roots as their main source of nitrogen.

Used to make amino acids, proteins, nucleic acids and chlorophyll.

The oxidation of ammonium to nitrite by Nitrosomonas and then nitrite to nitrate by Nitrobacter.

Needs aerobic conditions.

The conversion of nitrogen gas into ammonium ions, by bacteria such as Rhizobium and Azotobacter.

Produces ammonium, not nitrate.

The enzyme in nitrogen-fixing bacteria that reduces nitrogen gas to ammonium.

Inhibited by oxygen.

A gap in the myelin sheath between neighbouring Schwann cells, where the axon membrane is exposed.

Depolarisation happens only here.

Inhibition where binding away from the active site reduces catalytic activity.

Extra substrate does not overcome the simple model.

Populations of one species that are no longer joined, so individuals cannot interbreed.

Total numbers may look healthy while each group is genetically small.

Making ATP as electrons pass in one direction from water, through PSII and PSI, to NADP.

Produces ATP, reduced NADP and oxygen.

The failure of homologous chromosomes or sister chromatids to separate at anaphase of meiosis.

One gamete then has an extra chromosome and another has none.

Variation caused only by the environment, which is not passed on in gametes.

A scar or trained muscle is non-heritable.

The neurotransmitter released by sympathetic neurones at target organs.

Not adrenaline, which is a hormone.

A symmetrical, bell-shaped distribution in which the mean, median and mode are equal.

About 95% of values lie within two standard deviations of the mean.

The planetary boundary covering manufactured chemicals, radioactive materials, nanomaterials and micro-plastics.

Previously called the chemical pollution boundary.

The layer of cells inside the integuments of an ovule that supplies nutrients to the embryo sac.

It lies between the integuments and the embryo sac.

A length of DNA wound round a core of histone proteins.

Tightly packed nucleosomes keep genes switched off.

A membrane-bound cell compartment containing the main chromosomes of a eukaryotic cell.

Mitochondria and chloroplasts also contain DNA.

The statement that there is no difference or no effect, tested by a statistical test.

Reject it if the calculated value exceeds the critical value.

A culture medium made solid with agar, a jelly from seaweed, used in Petri dishes or as slopes.

Each living bacterium on agar grows into a colony.

A liquid culture medium.

Used for growing bacteria and making dilutions.

A microorganism that must have oxygen to grow.

In a tube of medium it grows only at the surface.

A microorganism that cannot grow when oxygen is present, because oxygen is toxic to it.

In a tube of medium it grows only at the bottom.

The lobe at the back of each hemisphere, for vision.

Contains the visual cortex.

The fall in the pH of the oceans as dissolved carbon dioxide releases hydrogen ions.

pH has fallen from about 8.16 to about 8.03.

Swelling caused by excess fluid building up in the tissues.

A result of kidney failure.

A hormone from the follicle cells, and later the placenta, that rebuilds the endometrium and controls FSH and LH by feedback.

Low levels inhibit FSH; very high levels stimulate the LH surge.

The equivalent of the menstrual cycle in mammals other than humans, in which the lining is reabsorbed rather than shed.

Only the words differ; the hormones are the same.

A mutated proto-oncogene that is switched on permanently and causes uncontrolled cell division.

Oncogenes cause cancer by being switched on.

The production of secondary oocytes in the ovary.

One primary oocyte gives one ovum and two polar bodies.

A diploid cell in the germinal epithelium of the ovary that divides by mitosis before birth.

All oogonia are formed before birth.

The female gamete of a flowering plant, one of the eight nuclei of the embryo sac.

It lies at the micropylar end, flanked by the two synergids.

Learning by trial and error to associate a behaviour with a reward or punishment.

Skinner's rats.

A specialised structure within a cell that carries out a particular function.

Not every organelle has a membrane.

A chemical, used in some insecticides, that inhibits acetylcholinesterase.

Causes over-stimulation, spasms and paralysis.

The end of a muscle attached to a bone that does not move; the insertion is the end on the bone that moves.

The biceps inserts on the radius.

The pencil line on which the mixture is spotted at the start of chromatography.

Must be above the solvent level.

An instrument that displays changes in potential difference over time as a trace.

Read axes carefully: mV and ms.

A receptor cell in the hypothalamus that detects changes in the water potential of the blood.

Shrinks when water potential falls.

The control of the water potential of the body fluids.

Uses ADH.

Net movement of water through a partially permeable membrane from higher to lower water potential.

Water moves, not the dissolved solute.

A degenerative joint disease in which articular cartilage wears away faster than it is repaired.

X-rays show a narrowed joint space.

A bone cell that builds bone by secreting collagen and laying down hydroxyapatite.

Osteoblasts build: both contain b.

A large bone cell with several nuclei that breaks bone down, releasing calcium and phosphate.

Drugs for osteoporosis often reduce osteoclast activity.

Softening of the bones in adults caused by a lack of vitamin D or calcium.

The adult form of rickets.

An abnormal loss of bone mass and density, making bones fragile and likely to fracture.

Most common in older women after the menopause.

The closed base of a carpel, which contains the ovules and becomes the fruit.

The ovary becomes the fruit; the ovule becomes the seed.

Harvesting fish at a rate that exceeds the rate at which they reproduce.

Define it as a comparison of two rates.

Keeping so many grazing animals on land that the vegetation and soil are damaged.

Hooves compact the soil so water cannot drain through it.

The ciliated tube that carries a secondary oocyte from the ovary to the uterus, and the usual site of fertilisation.

Also called the Fallopian tube.

The release of a secondary oocyte from a mature follicle at the surface of the ovary.

Caused by the LH surge, usually on day 14.

The structure inside an ovary that contains the embryo sac, and which becomes a seed after fertilisation.

Each ovule can give one seed, so the ovule count sets the maximum number of seeds.

The mature female gamete, formed only after a sperm has entered and meiosis II has been completed.

Do not use ovum for the cell released at ovulation.

Loss of electrons or hydrogen, or gain of oxygen.

A substrate is oxidised when a dehydrogenase removes hydrogen from it.

Making ATP using energy from electrons passing along the electron transport chain, with oxygen as the final electron acceptor.

Makes most of the ATP in aerobic respiration.

The extra oxygen needed after exercise to break down the lactate made in anaerobic respiration.

Lactate is converted back to pyruvate in the liver.

A hormone from the posterior pituitary that makes the myometrium contract at birth and ejects milk during suckling.

Its release at birth is positive feedback.

The thinning of the ozone layer in the stratosphere, caused by halogenated hydrocarbons.

The only boundary whose crossing was deliberately avoided.

The layer of tall, closely packed cells just below the upper epidermis of a leaf, containing the most chloroplasts.

Describe chloroplast distribution relative to this layer.

An epidemic that spreads across many countries or continents.

The 1918 influenza outbreak was a pandemic.

The ring of fine hairs on a wind-dispersed fruit that acts as a parachute.

It increases air resistance so the fruit falls slowly.

The division of the autonomic nervous system that conserves energy; its neurones release acetylcholine.

Decreases heart rate.

The lobe behind the central sulcus, containing the sensory cortex.

Touch, temperature, pain.

A membrane that allows some substances to cross more readily than others.

Permeability depends on both membrane and substance.

Solid particles in the air, classified by diameter as PM10 or PM2.5.

PM2.5 passes into the capillaries and raises cardiovascular deaths.

Immunity from antibodies made by another individual.

Immediate but short-lived.

An organism that causes disease.

Pathogenic means able to cause disease.

The scapula and clavicle, which attach the forelimb to the axial skeleton.

The pelvic girdle attaches the hind limb.

A family tree showing which members have an inherited condition.

Squares are males, circles are females, shaded symbols are affected.

The funnel-shaped cavity in the kidney where urine collects before entering the ureter.

Also called the renal pelvis.

An antibiotic that stops cross-links forming in peptidoglycan, weakening the cell wall so bacteria burst.

It is ineffective against Gram-negative bacteria because the outer membrane protects the peptidoglycan.

The polymer of sugar chains cross-linked by short amino acid chains that forms bacterial cell walls.

Also called murein.

The percentage of a quadrat's area covered by a species.

Used for plants and seaweeds that are hard to count.

A protein released by T killer cells that makes holes in the membrane of the target cell.

The target cell then dies.

The fruit wall, formed from the ovary wall.

In a maize grain the pericarp is fused to the testa.

The thin outer covering of the uterus.

It is the outermost of the three layers of the uterus wall.

All the nerves outside the brain and spinal cord.

Links receptors and effectors to the CNS.

The membrane lining the abdominal cavity.

Acts as the dialysis membrane in CAPD.

One of the parts of the corolla, often large and coloured in insect-pollinated flowers.

Say that petals attract pollinators, not that they look attractive.

The engulfing and digestion of a microorganism or particle by a phagocyte.

Lysosomes fuse with the phagosome.

Using a person's genes to choose drugs and doses that suit them.

For example, dosing warfarin.

The characteristics an organism expresses, produced by its genotype and its environment.

Selection acts on phenotypes, which changes allele frequencies.

A chemical released by an animal that affects the behaviour of others of the same species.

Ants lay pheromone trails.

One of the distinct sounds that make up the words of a language.

Babies can distinguish the phonemes of all languages.

Adding a phosphate group to a molecule.

Joining ADP and Pᵢ to form ATP is phosphorylation.

The splitting of water in the light-dependent stage, producing electrons, protons and oxygen: H₂O → 2H⁺ + 2e⁻ + ½O₂.

Takes place in the thylakoid space; supplies electrons to PSII.

A packet of light energy.

Photons excite electrons in pigment molecules.

Making ATP from ADP and inorganic phosphate using energy that came from light.

Happens on the thylakoid membranes by chemiosmosis.

The process in which plants, algae and some bacteria use light energy to make organic molecules from carbon dioxide and water, releasing oxygen.

Overall equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Apparatus that collects the gas released by an aquatic plant in a capillary tube so its volume can be measured.

Volume = πr² × bubble length.

A group of pigment and protein molecules in the thylakoid membrane, made of an antenna complex and a reaction centre.

There are two: photosystem I and photosystem II.

The photosystem whose reaction centre chlorophyll absorbs best at 700 nm (P700).

Used in both cyclic and non-cyclic photophosphorylation.

The photosystem whose reaction centre chlorophyll absorbs best at 680 nm (P680), receiving electrons from photolysis.

Used only in non-cyclic photophosphorylation.

A molecule that absorbs certain wavelengths of light and reflects others.

Chloroplast pigments are chlorophylls and carotenoids.

The first organisms to colonise bare ground, such as lichens.

Tolerate harsh conditions and start soil formation.

An endocrine gland below the hypothalamus with anterior and posterior lobes.

The anterior lobe releases ACTH.

The ridge of tissue inside an ovary to which the ovules are attached by their funicles.

In a plant this word means an attachment ridge, not an organ of exchange.

A limit within which a global system must operate to prevent abrupt and irreversible environmental change.

Nine have been identified.

A cell formed from an activated B cell that secretes large amounts of one antibody.

B cells themselves do not secrete antibodies.

A small ring of DNA in a bacterium, separate from its chromosome, that can pass between bacteria.

Resistance alleles often spread on plasmids.

The young shoot of an embryo plant.

In a broad bean it is bent into a hook so that soil is pushed aside by the bend.

Able to become any cell type in the body, but not the placenta.

Embryonic stem cells are pluripotent.

A cell of the inner wall of the Bowman's capsule with foot processes that wrap round the capillaries.

Gaps between feet are filtration slits.

A gene mutation that changes one or a few bases in the DNA.

Also called a gene mutation.

A small cell with almost no cytoplasm produced by the unequal divisions of oogenesis.

Polar bodies cannot be fertilised and break down.

The diploid nucleus in the middle of the embryo sac, formed when two haploid nuclei fuse.

It is already diploid before fertilisation, which is why the endosperm nucleus is triploid.

A small structure made in a pollen sac that contains the tube nucleus and the generative nucleus, and carries the male gametes between flowers.

The grain carries the gametes. It is not itself a gamete.

A diploid cell in a pollen sac that divides by meiosis to give a tetrad of four haploid cells.

One pollen mother cell gives four pollen grains.

One of the four cavities inside an anther in which pollen grains develop.

Four sacs in one anther: two lobes, two sacs each.

The outgrowth of a germinating pollen grain that carries the male gametes down the style to the ovule.

It digests a path with hydrolytic enzymes rather than pushing through.

The transfer of pollen from an anther to a stigma.

Pollination is a journey. Fertilisation is a fusion, and happens later.

Controlled by many genes.

Mental illnesses are polygenic.

A technique that makes millions of copies of a section of DNA using repeated cycles of heating and cooling.

Steps: 95 °C, about 55 °C, about 70 °C.

Having more than two complete sets of chromosomes.

Doubling can make a sterile hybrid fertile and create a species in one step.

The entry of more than one sperm into a secondary oocyte.

It would give a triploid cell, which cannot develop.

All the organisms of one species living in the same place at the same time, which can interbreed.

Only one species.

A sharp fall in population size that leaves few individuals and little genetic variation.

Northern elephant seals are an example.

The number of individuals per unit area or volume.

Units such as individuals per m².

A protein channel in the outer membrane of Gram-negative bacteria.

Resistant bacteria may have fewer porins.

Control in which the response increases the original change.

Very high oestrogen causing the LH surge, and oxytocin during birth, are both positive feedback.

Imaging that detects gamma rays from a radioactive tracer, such as labelled glucose, to show active areas.

Abbreviated to PET.

Isolation that acts after a zygote forms, such as hybrid inviability or sterility.

The hybrid's genes cannot pass on.

The back lobe of the pituitary gland, which stores and releases ADH.

Not the anterior pituitary.

The tilting of a bound myosin head that pulls the actin filament towards the centre of the sarcomere.

It happens as ADP and phosphate are released.

Testing a cell from an IVF embryo for a genetic disorder before the embryo is placed in the uterus.

Only unaffected embryos are implanted.

Isolation that stops gametes fusing, so no zygote forms.

Geographical, seasonal, behavioural, morphological and gametic.

The triploid nucleus formed when a male gamete fuses with the diploid polar nucleus.

It divides to give the endosperm.

A diploid cell that has begun meiosis I and is held at prophase I until puberty.

Every primary oocyte is already present at birth.

The slow, small immune response the first time an antigen is met.

Has a long latent period.

The enlarged diploid cell that enters meiosis I in spermatogenesis.

One primary spermatocyte gives four spermatozoa.

Succession that starts on bare ground with no soil, such as bare rock.

Slow.

A short single strand of DNA complementary to the start of the section to be copied.

It lets DNA polymerase attach and begin copying.

An organism that makes organic molecules from inorganic ones using light energy, such as a plant or alga.

The first trophic level.

A hormone from the corpus luteum, and later the placenta, that maintains the endometrium and stops the myometrium contracting.

It also inhibits FSH, LH and prolactin.

An organism whose cells have no nucleus or membrane-bound organelles. Bacteria and Archaea are prokaryotes.

Bacterial cell walls contain peptidoglycan; Archaea do not.

A hormone from the anterior pituitary that stimulates the mammary glands to secrete milk and inhibits FSH.

It stimulates secretion; it does not make the milk itself.

The region at the start of a gene where RNA polymerase and transcription factors bind.

A methylated promoter cannot be used.

A gland below the bladder that secretes an alkaline fluid into the urethra.

The alkali neutralises acid in the vagina and in the urethra.

An enzyme that hydrolyses protein to amino acids.

Proteases work alongside amylase in a germinating seed.

A normal gene that stimulates cell division when needed.

It can mutate to an oncogene.

A positively charged particle; in biology, a hydrogen ion, H⁺.

A hydrogen atom is one proton plus one electron.

A difference in proton concentration across a membrane, which stores potential energy.

Kept because the inner membrane is impermeable to protons.

A protein in the electron transport chain that uses energy from electrons to actively transport protons across the membrane.

Pumps move protons into the intermembrane space.

The coiled first part of the tubule, in the cortex, where most reabsorption happens.

PCT for short.

A drug that acts on the brain and changes mood, perception or behaviour.

Many act at synapses.

A grid showing every possible fusion of the gametes of two parents, and the resulting genotypes.

Put one parent's gametes along the top and the other's down the side.

A diagram showing the dry mass of organisms at each trophic level at one time.

Can be inverted.

A diagram showing the energy flowing through each trophic level per unit area per year.

Never inverted.

The three-carbon product of glycolysis.

With oxygen it forms acetyl CoA; without oxygen it forms lactate or ethanol.

A square frame marking a known area, used to sample organisms.

Often 0.25 m² or 1 m².

A limit on the mass of a species that may be landed.

Can lead to discards, where excess fish are thrown back dead.

A fatal viral disease of the nervous system, usually spread by the bite of an infected animal.

Treated at once with antibodies and vaccine.

The young root of an embryo plant, which emerges first at germination.

It anchors the seedling and takes up water and mineral ions.

Choosing individuals to measure using random numbers, so that every individual has an equal chance and bias is avoided.

A random sample is representative.

The largest value minus the smallest value.

A single extreme value changes the range.

An organisation that maintains older, less commercial breeds of domesticated animals.

Keeps useful characteristics such as hardiness.

The part of a photosystem containing a pair of chlorophyll a molecules that release excited electrons.

PSI reaction centre is P700; PSII is P680.

The way the bases of mRNA are grouped into codons of three.

A deletion that is not a multiple of three shifts it.

The swollen end of the flower stalk to which all four whorls are attached.

It is the base of the flower, not part of any whorl.

A cell or group of cells that detects a particular stimulus and converts its energy into nerve impulses.

Receptors act as transducers.

Describing an allele that is only expressed in the phenotype when no dominant allele is present.

Say expressed, not found: recessive alleles are present in heterozygotes.

The specific base sequence at which a restriction enzyme cuts.

Often a palindrome such as GAATTC.

A gamete or offspring with a combination of alleles different from either parental chromosome, produced by crossing over.

Recombinants are always less common than parental types for linked genes.

DNA made by joining DNA from two different sources, often two species.

A plasmid containing a human gene is recombinant DNA.

The percentage of offspring that are recombinant.

It rises the further apart two linked genes are.

A published list of species with their IUCN threat category.

Ratings depend on numbers, rate of decline and distribution.

A reaction in which one substance is oxidised and another is reduced at the same time.

Each transfer of electrons along the electron transport chain is a redox reaction.

FAD that has accepted hydrogen; it delivers electrons and protons to the electron transport chain at the second proton pump.

Each gives 2 ATP (theoretical).

NAD that has accepted hydrogen; it carries electrons and protons to the electron transport chain.

Each gives 3 ATP (theoretical).

NADP that has accepted electrons and protons; it supplies reducing power to the Calvin cycle.

Used to reduce GP to triose phosphate.

Gain of electrons or hydrogen, or loss of oxygen.

NAD is reduced when it accepts hydrogen.

A rapid, automatic response to a stimulus.

Escape reflexes protect animals.

The pathway of neurones involved in a reflex action.

Receptor, sensory, relay, motor, effector.

A short time after an action potential when that part of the membrane cannot produce another.

Makes impulses one-way.

Returning a species to a habitat it formerly occupied, after captive breeding.

Animals may need training to avoid predators and to forage.

The later part of the refractory period, when a new action potential can be generated only by a stronger than normal stimulus.

The membrane is hyperpolarised.

A short neurone in the CNS that links sensory and motor neurones.

Found in the grey matter.

The artery that brings blood to a kidney.

A branch of the aorta.

The vein that carries blood away from a kidney.

Drains to the vena cava.

Pressing colonies from one plate on to another with a sterile pad, to copy their positions exactly.

Used to find colonies that die on a second antibiotic.

The return of the potential difference towards negative as K⁺ leave the axon.

Potassium channels open.

The prevention of interbreeding, and so of gene flow, between groups of a species.

Pre-zygotic or post-zygotic.

When a pathogen is no longer affected by a drug that used to kill it or stop its growth.

Bacteria become resistant; people do not.

The process in all living cells that releases chemical energy from organic molecules, such as glucose, and transfers it to ATP.

Say respiration releases energy; never say it produces energy.

A substance that blocks an enzyme or protein in respiration, reducing ATP production.

Examples: cyanide, oligomycin, malonic acid.

The volume of carbon dioxide produced divided by the volume of oxygen consumed in respiration.

Not in the specification; the formula is given if needed.

Apparatus that measures the rate of oxygen uptake by small organisms, using a solution that absorbs carbon dioxide.

Volume of oxygen = πr² × distance moved.

The potential difference across the membrane of a neurone that is not conducting an impulse, about −70 mV.

The membrane is polarised.

A bacterial enzyme that cuts DNA at a specific base sequence called its recognition site.

Also called a restriction endonuclease.

The transport of a neurotransmitter back into the presynaptic neurone.

Blocking it increases transmission.

Forcing water across a partially permeable membrane against its water potential gradient by applying pressure.

The phrase 'against its water potential gradient' earns the mark.

An enzyme from retroviruses that makes DNA using RNA as a template.

Used to make cDNA from mRNA.

The distance moved by a substance divided by the distance moved by the solvent front.

No units; always between 0 and 1.

An autoimmune disease in which the immune system attacks the synovial membrane, then cartilage and bone.

Often affects small joints of both hands.

A structure made of ribosomal RNA and proteins where polypeptides are assembled during translation.

It is not membrane-bound.

A five-carbon compound that accepts carbon dioxide in the Calvin cycle.

Abbreviated RuBP; regenerated from triose phosphate using ATP.

A disorder in children in which too little calcium is laid down in growing bones, so they are soft and bend.

Caused by a lack of vitamin D or calcium.

Threat displays, postures and calls used instead of fighting.

Reduces the risk of injury.

A swelling on the root of a legume containing nitrogen-fixing Rhizobium bacteria.

Contains leghaemoglobin.

A mild viral disease (German measles) that can seriously harm a foetus if caught in early pregnancy.

Prevented by the MMR vaccine.

Ribulose bisphosphate carboxylase, the enzyme that catalyses the reaction of carbon dioxide with RuBP.

Often the rate-limiting enzyme of the Calvin cycle.

The region in which planetary systems are stable, changes are reversible and there is no detrimental impact on global systems.

Shown by the central circle of the diagram.

A red counter-stain used last in the Gram stain, which colours Gram-negative bacteria pink or red.

Gram-positive bacteria stay purple.

Conduction in a myelinated axon in which the action potential jumps from node to node.

Faster and uses less ATP.

A DNA sequencing method using chain terminator nucleotides to make fragments of every length, sorted by electrophoresis.

Also called the chain termination method.

An organism that feeds by extracellular digestion of dead organic matter.

Most decomposers.

The cell surface membrane of a muscle fibre.

It folds in to form T tubules.

The repeating unit of a myofibril, from one Z line to the next.

Sarcomeres shorten when muscle contracts.

Specialised endoplasmic reticulum in muscle fibres that stores and releases calcium ions.

Calcium is pumped back into it for relaxation.

A porous, biodegradable 3D framework on which cells are grown in tissue engineering.

It breaks down as new tissue forms.

A cell that wraps around an axon to form the myelin sheath.

Each has its own nucleus.

A sideways curve of the spine.

Often treated with a brace while the skeleton grows.

The single, shield-shaped cotyledon of a cereal grain, which absorbs the digested food from the endosperm.

It is a cotyledon, not part of the endosperm.

Separation of populations that breed or flower at different times of year; also called temporal isolation.

Different flowering times stop cross-pollination.

The haploid cell released at ovulation, held at metaphase II until a sperm enters.

It is not an ovum until meiosis II is completed.

The rate at which consumers make new biomass.

About 10% of the energy they eat.

The fast, large immune response when an antigen is met again, caused by memory cells.

Usually no symptoms.

One of the two haploid cells formed by meiosis I in spermatogenesis.

Each then divides by meiosis II into two spermatids.

Succession that starts where soil is already present after a community has been removed.

Faster than primary succession.

A store of seeds in highly controlled conditions, often at very low temperature.

Samples are periodically germinated because seeds degrade.

An environmental factor that makes some phenotypes more likely than others to survive and reproduce.

Also called a selective agency; name it in the context.

A characteristic that makes an individual more likely to survive and reproduce in its environment.

Examiners want this exact term.

Felling only some trees and leaving the others in place.

Reduces soil erosion and keeps nutrients in the forest.

A culture medium that allows only certain microorganisms to grow.

For example, a medium containing an antibiotic allows only resistant bacteria to grow.

The uptake of particular useful substances from the filtrate back into the blood, using specific carrier proteins.

Mainly in the PCT.

Pollen landing on the stigma of the same flower, or of another flower on the same plant.

It guarantees seed but gives little new genetic variation.

Spermatozoa suspended in the fluids secreted by the seminal vesicles and the prostate gland.

Most of the volume is gland secretion, not sperm.

A gland that secretes a fluid containing fructose and mucus into the vas deferens.

The fructose is a respiratory substrate for the sperm.

One of the long coiled tubes inside a testis in which spermatozoa are made.

A section of testis shows many circles because the tubules are coiled.

The area of cortex behind the central sulcus that receives impulses from receptors in the skin.

Also called the somatosensory cortex.

A neurone that carries impulses from a receptor to the CNS.

Its cell body is in the dorsal root ganglion.

One of the small, usually green parts that make up the calyx.

Sepals form the outside of an unopened bud.

Each community in the sequence of succession.

Replaced by the next stage.

The whole sequence of communities in succession.

Not the final community.

A series of step-by-step dilutions, each diluting the previous one by the same factor, such as tenfold.

1 cm³ into 9 cm³ gives a tenfold dilution at each step.

A tall cell inside the wall of a seminiferous tubule that nourishes and protects the developing sperm cells.

Also called a sustentacular cell.

The value of a factor that a homeostatic system tries to maintain.

Body temperature about 37 °C.

The pair of chromosomes that determines sex: XX in a human female and XY in a male.

All other chromosomes are autosomes.

The inheritance of a gene carried on a sex chromosome, usually on the part of the X with no partner on the Y.

Write the allele as a superscript on the X, never on the Y.

A clear difference in appearance between males and females of a species.

Produced by sexual selection.

Selection for characteristics that increase an individual's success in getting mates.

Intra-sexual or inter-sexual.

A short base sequence repeated many times in a row in non-coding DNA; the number of repeats varies between people.

Abbreviated to STR.

An inherited condition in people homozygous for the Hbˢ allele, whose red cells become sickle-shaped.

Heterozygotes have sickle cell trait and are protected from severe malaria.

A specific signal from one animal that triggers a fixed action pattern in another.

The red belly of a male stickleback.

The steps that convert detection of a signal into changes within a cell.

The signal molecule need not enter the cell.

The probability used as the cut-off for deciding whether a result could be due to chance, usually 5 % or p = 0.05.

Below 0.05 the difference is significant.

Describing a difference unlikely to be due to chance, usually at a probability of less than 0.05.

Always say what is significant: the difference between the means.

The pacemaker of the heart, which starts each heartbeat.

Abbreviated to SAN.

An area given legal protection in the UK because of its wildlife, geology or landforms.

One of several designations, along with special areas of conservation.

Describing a distribution with a longer tail on one side.

A shift of the peak between years can show selection.

Cutting and burning a small area of forest and growing crops on the soil fertilised by the ash.

Sustainable on a small scale only.

The explanation of contraction in which actin filaments slide between myosin filaments, shortening the sarcomere without the filaments changing length.

Filaments slide; they do not shorten.

Muscle fibres that contract slowly and resist fatigue, using aerobic respiration.

Rich in mitochondria, capillaries and myoglobin.

A disease caused by the variola virus, spread by droplets and contact, and eradicated by 1980.

The only human disease wiped out by vaccination.

Interactions between individuals of the same species that form structured social groups.

Include same species and structured group.

A carrier protein that uses ATP to actively transport 3 Na⁺ out of the cell for every 2 K⁺ in.

Give the numbers.

The removal of topsoil, which contains most of the nutrients, usually by rain or wind.

Tree roots bind the soil and prevent it.

The furthest point reached by the solvent on a chromatogram.

Mark it in pencil as soon as the chromatogram is removed.

Gene therapy on body cells; the change is not inherited.

Often has to be repeated.

A mutation in a body cell, which cannot be passed to offspring.

Only mutations in gamete-forming cells are inherited.

Transferring DNA fragments from a gel to a nylon membrane so they can be located with probes.

Used in the original fingerprinting method.

Summation of impulses arriving at the same time from several neurones.

Several neurones, one moment.

The formation of a new species from an existing one.

It needs reproductive isolation.

A group of organisms with similar features that can interbreed to produce fertile offspring.

Both parts are needed: interbreed and fertile offspring.

A store of frozen gametes from threatened or economically important animals.

Samples can be sent worldwide instead of moving the animals.

A haploid cell formed by meiosis II that matures into a spermatozoon.

Four spermatids come from one primary spermatocyte.

The production of spermatozoa in the seminiferous tubules of the testis.

One primary spermatocyte gives four spermatozoa.

A diploid cell in the germinal epithelium of a seminiferous tubule that divides by mitosis.

Some keep dividing so that the supply of cells never runs out.

The male gamete: a small motile cell with an acrosome, a haploid nucleus, a middle piece and a tail.

Plural spermatozoa. About 60 µm long.

A mixed nerve, containing sensory and motor neurones, that joins the spinal cord.

There are 31 pairs.

A rigid, spiral shaped bacterium. The plural is spirilla.

A spirochaete is also spiral but thinner and flexible.

A thin, flexible, corkscrew shaped bacterium.

Spirochaetes and spirilla are both spiral shaped bacteria.

Bone made of a lattice of thin struts with spaces holding marrow, found at the ends of long bones and in vertebrae.

Also called cancellous bone.

The layer of loosely packed leaf cells with large air spaces, below the palisade mesophyll.

Contains chloroplasts, but fewer than palisade cells.

The extremely resistant polymer that makes up the exine of a pollen grain.

It resists decay, which is why pollen survives in peat for thousands of years.

The stage of Plasmodium injected by the mosquito, which infects liver cells.

Sporozoites form in the mosquito's salivary glands.

A gene on the Y chromosome that switches on the development of testes and male characteristics.

It is the reason one Y makes an embryo male.

Selection against both extremes, so the mean stays the same and the spread narrows.

Human birth mass is the classic example.

A microscope slide with a scale of known length engraved on it, used to calibrate an eyepiece graticule.

Usually divided into 0.01 mm divisions.

The male part of a flower: an anther on a filament.

The stamen is the whole structure; the anther alone is not a stamen.

A measure of how spread out values are around the mean.

Its square, s², is used in the t test.

Spherical bacteria arranged in irregular clusters, like bunches of grapes.

Staphylococcus aureus is a Gram-positive coccus.

The phase when population size stays roughly constant because birth rate equals death rate.

The population is at the carrying capacity.

An undifferentiated cell that can divide repeatedly and differentiate into specialised cells.

Give both parts: divide and differentiate.

A short single-stranded overhang left by a staggered cut, which pairs with a complementary sticky end.

Same enzyme, complementary sticky ends.

The receptive surface at the top of a carpel that catches pollen.

Small and sticky in insect-pollinated flowers, large and feathery in wind-pollinated ones.

A change in the internal or external environment that an organism can detect.

Plural: stimuli.

The line of weakness between the two pollen sacs of an anther lobe, along which the anther splits.

The groove you see on the outside of a lobe marks the stomium.

Spherical bacteria arranged in chains.

Do not confuse with staphylococci, which form clusters.

Harvesting a narrow band of forest and leaving it uncut for decades so that it regenerates.

Seeds arrive from neighbouring trees and succession follows.

An interruption of the blood supply to part of the brain, so neurones there die.

Ischaemic (clot) or haemorrhagic (bleed).

The connective tissue that makes up the bulk of an ovary and holds the follicles.

It lies beneath the germinal epithelium.

A statistical test that decides whether the difference between the means of two sets of continuous data is significant.

The null hypothesis is no significant difference between the means.

The stalk of a carpel, joining the stigma to the ovary, through which the pollen tube grows.

The tube digests its way down the style rather than pushing through it.

A point mutation in which one base is replaced by another.

It changes at most one amino acid.

A reactant on which an enzyme acts.

It is converted into one or more products.

Making ATP by transferring a phosphate group directly to ADP, using energy from a reaction, without an electron transport chain.

Happens in glycolysis and the Krebs cycle.

The gradual, directional change in the community living in an area over time.

Each stage alters conditions for the next.

The adding together of small depolarisations so that threshold is reached.

Temporal or spatial.

Using resources so that present needs are met without preventing future generations from meeting theirs.

The rate of use must not exceed the rate of replacement.

The division of the autonomic nervous system that prepares the body for activity; its neurones release noradrenaline.

Increases heart rate and ventilation rate.

The formation of new species from populations living in the same area.

Isolated by behaviour, season, structure or polyploidy.

A junction between two neurones, or between a neurone and an effector cell.

Makes transmission one-way.

The gap, about 20 nm wide, between the presynaptic and postsynaptic membranes.

Too small for a light microscope.

The swollen end of an axon terminal at a synapse.

Also called synaptic bulb.

The ability of a synapse to become stronger or weaker with use.

Underlies learning and memory.

The removal of unused synapses, mainly between early childhood and adolescence.

Use it or lose it.

A small membrane sac in the synaptic knob containing neurotransmitter.

Fuses with the presynaptic membrane.

One of the two nuclei beside the oosphere at the micropylar end of the embryo sac.

The synergids guide the pollen tube in and then break down.

Fluid secreted by the synovial membrane that lubricates a joint and nourishes the cartilage.

The synovial membrane makes it.

A freely movable joint with articular cartilage, a fluid-filled cavity lined by synovial membrane, a capsule and ligaments.

Hinge, gliding and ball and socket joints are synovial.

A T lymphocyte that binds a presented antigen and releases cytokines that activate other immune cells.

Destroyed by HIV.

A cytotoxic T lymphocyte that binds to and destroys infected or cancerous body cells.

It releases perforin.

Infoldings of the sarcolemma that carry depolarisation deep into the muscle fibre.

T stands for transverse.

The number of standard deviations a person's bone density is above or below the mean for a healthy young adult.

A T-score of −2.5 or lower means osteoporosis.

The layer of cells lining each pollen sac, which nourishes the developing pollen grains and supplies material for the exine.

It does not divide to form the pollen grains.

A thermostable DNA polymerase from the bacterium Thermus aquaticus.

It does not denature at 95 °C.

A cell able to respond to a signal because it has the appropriate receptor and response machinery.

Receptor specificity helps determine the response.

A directional movement of a whole organism towards or away from a stimulus.

Plural taxes; for example negative phototaxis.

The lobe at the side of each hemisphere, for hearing, language comprehension and memory.

Contains Wernicke's area and the auditory cortex.

Summation of several impulses arriving in quick succession at one synapse.

One neurone, repeated impulses.

An inelastic band of collagen joining a muscle to a bone.

It transmits the full force of contraction.

An area defended by an animal against other members of its species.

Provides food, nest sites and mates.

A cross between an organism with the dominant phenotype and a homozygous recessive organism, to find its genotype.

Also called a back cross.

The tough seed coat, formed from the integuments of the ovule.

It protects the seed and keeps it dry until germination.

The male sex hormone, secreted by the interstitial cells of the testis.

It stimulates spermatogenesis and maintains the male reproductive system.

A group of four haploid cells produced by the meiosis of one pollen mother cell, still held inside its wall.

A tetrad is the clearest evidence in a slide that meiosis has happened.

A structure in the centre of the forebrain that relays sensory impulses to the cerebral cortex.

The hypothalamus is below it.

An autosomal recessive blood disorder in which too little of one haemoglobin chain is made.

Causes severe anaemia.

Making an early embryo from a patient's body cell nucleus to obtain matching stem cells.

Allowed under licence in the UK; reproductive cloning is not.

A machine that changes the temperature of PCR tubes quickly and precisely.

Also called a thermocycler.

The potential difference, about −55 mV, that must be reached for an action potential to be generated.

Below it, no action potential.

A flattened membrane sac inside a chloroplast, whose membrane holds the pigments, photosystems and electron transport chain.

The light-dependent stage takes place on the thylakoid membranes.

The space inside a thylakoid, also called the lumen, where protons build up.

Photolysis happens here.

The tumour-inducing plasmid of Agrobacterium tumefaciens, used as a vector to put genes into plants.

Its tumour genes are removed first.

A seal between neighbouring epithelial cells that stops fluid leaking between them.

Forces substances through the cells.

The point at which a small further change produces a very large and unpredictable effect.

The response of the system is not linear.

Growing new tissue from cells on a scaffold outside the body, to replace damaged tissue.

Uses a biodegradable scaffold.

A count that includes both living and dead cells, for example from turbidity measurements.

Total counts are higher than viable counts once cells begin to die.

Able to become any cell, including the cells of the placenta.

The zygote is totipotent.

A molecule made by a pathogen that damages cells or causes disease.

Cholera toxin makes gut cells lose chloride ions.

Something that converts one form of energy into another; receptors convert stimulus energy into electrical impulses.

Use it when describing receptors.

A line laid across a habitat along an environmental gradient, used to sample changes in the distribution of organisms.

Always mention the environmental gradient.

Describes a cell that has taken up and kept new DNA, such as a plasmid.

Calcium ions and heat shock help transformation.

An organism that contains a gene from another species.

Bt maize is transgenic.

The bacterial enzyme that forms cross-links between peptidoglycan chains.

Penicillin binds to its active site.

Dragging a large net through the water to catch fish in mid water or near the bottom.

Heavy equipment damages seabed habitats.

A lipid made of glycerol joined to three fatty acids.

Hydrolysed before being respired.

A three-carbon sugar phosphate formed when hexose bisphosphate splits in glycolysis.

Glycerol from lipids is converted to triose phosphate.

Having three complete sets of chromosomes, written 3n.

Do not confuse with trisomy.

Having three copies of one chromosome instead of two.

Trisomy 21 causes Down's syndrome.

A feeding level in a food chain.

Producers are the first trophic level.

The outer layer of cells of a blastocyst, which becomes the chorion and then the placenta.

Its villi grow into the endometrium at implantation.

A long protein lying along the actin filament that covers the myosin binding sites at rest.

It is moved when calcium binds to troponin.

A protein on the thin filament that binds calcium ions and then moves tropomyosin.

Calcium binds to troponin, not tropomyosin.

Describing a line of organisms that always produces offspring like themselves, because they are homozygous.

Mendel started every cross with true-breeding plants.

Triphenyl tetrazolium chloride: a tetrazolium compound that is colourless when oxidised and red when reduced.

The red product is not re-oxidised by air, so it suits a colorimeter.

The nucleus at the tip of a growing pollen tube that controls its growth and codes for its enzymes.

It controls the tube and codes for the enzymes; it does not make, contain or secrete them.

A disease, mainly of the lungs, caused by Mycobacterium tuberculosis and spread in airborne droplets.

Treated with several antibiotics for at least six months.

A mass of cells formed by uncontrolled cell division.

Cancer begins when control of the cell cycle breaks down.

A gene whose protein stops the cell cycle when DNA is damaged and can trigger cell death.

Tumour suppressor genes cause cancer by being switched off.

The cloudiness of a liquid culture, which increases as the number of cells increases.

Measured with a colorimeter; gives a total count.

Filtration under high pressure, in which small molecules are forced out of the blood in the glomerulus into the Bowman's capsule.

Separates by size.

The cord joining the foetus to the placenta, containing two umbilical arteries and one umbilical vein.

The artery carries blood away from the foetus.

A chemical that makes a membrane leaky to protons, so electron transport continues without ATP being made.

DNP is an uncoupler; the energy is released as heat.

A culture medium containing ingredients whose exact chemical make-up is unknown, such as yeast extract.

Any extract, peptone or egg ingredient makes a medium undefined.

A description of ATP: it is used by all organisms as the immediate energy source for most energy-requiring reactions.

Give both ideas: all organisms and most reactions.

The main nitrogenous excretory product of mammals, made in the liver from ammonia.

Less toxic than ammonia.

The tube that carries urine from a kidney to the bladder.

Not the urethra.

An almost insoluble, non-toxic nitrogenous waste excreted by birds, reptiles and insects.

Needs very little water.

Ultraviolet radiation of wavelength 280 to 315 nm, which is absorbed by ozone and by DNA.

More UVB means more skin cancers and cataracts.

A preparation of weakened or killed pathogens, antigens or inactivated toxins that stimulates an immune response and memory cells without causing disease.

Name what it contains and that it produces memory cells.

The part of an antibody at the tips of its arms whose amino acid sequence differs between antibodies, forming the antigen binding site.

Explains why antibodies are specific.

The differences between individuals of the same species.

Name both causes: genotype and environment.

The muscular tube that carries sperm from the epididymis to the urethra.

Also called the sperm duct.

Capillaries that run alongside the loop of Henle in the medulla.

Branch from the efferent arteriole.

An organism that transmits a pathogen to another organism.

The female Anopheles mosquito is the vector of malaria.

The root of a spinal nerve that leaves the front of the spinal cord and carries motor neurones.

No ganglion.

One of the bones of the vertebral column.

The plural is vertebrae.

The hole in a vertebra, enclosed by the vertebral arch, through which the spinal cord passes.

Transverse foramina are separate holes found in cervical vertebrae.

Able to survive and live normally.

Viable is not the same as fertile.

A count of living cells only, made by plating dilutions and counting the colonies that grow.

Dead cells do not form colonies.

A curved, comma shaped rod bacterium, such as Vibrio cholerae.

Vibrio cholerae is Gram-negative and causes cholera.

The area of the occipital lobe that receives impulses from the eyes.

Name it rather than saying the seeing area.

A vitamin made in the skin in sunlight and found in oily fish, needed to absorb calcium from the gut.

Link it to calcium absorption in every answer.

A channel running across compact bone that carries blood vessels between Haversian canals and the bone surface.

Also spelt Volkmann's canal.

An ion channel that opens or closes when the potential difference across the membrane changes.

Sodium and potassium channels in axons.

A honeybee dance that shows the direction and distance of food more than about 100 m away.

Angle from vertical equals angle from the sun.

The tendency of water to move out of a solution; water moves from higher to lower water potential by osmosis.

Pure water is 0; solutions are negative.

The distance between successive peaks of a wave; for light it determines colour and is measured in nanometres (nm).

Visible light is about 400 to 700 nm.

An association area in the temporal lobe of the left hemisphere that is needed to understand language.

Damage causes fluent but meaningless speech.

The strongest cartilage, with thick parallel bundles of collagen fibres.

It forms the intervertebral discs.

Nervous tissue made mainly of myelinated axons.

It is white because of the myelin.

A ring of similar parts attached at the same level on the receptacle of a flower.

There are four: calyx, corolla, stamens and carpel.

A strip of habitat, such as a hedgerow or a tunnel under a road, that joins two areas and allows organisms to move between them.

Restores gene flow between fragments.

The switching off of one X chromosome in each cell of a female mammal.

It is random but stays fixed in the cells descended from each cell.

Cartilage containing a dense network of elastic fibres, so it bends and springs back.

Found in the pinna of the ear and the epiglottis.

An energy diagram showing the path of electrons in non-cyclic photophosphorylation.

Electrons are raised twice by light, at PSII and PSI.

The glycoprotein coat immediately around a secondary oocyte.

It is digested by acrosomal enzymes and then hardened by the cortical reaction.

The arrangement of species in bands, or zones, along an environmental gradient.

Seaweeds on a rocky shore show zonation.

The clear area around an antibiotic disc where bacteria cannot grow.

Larger zone, more effective antibiotic.

The region between the boundary and the high risk area, where risk is increasing.

Lies between the inner and outer circles.

Photosynthetic organisms living inside corals, which give them their colour and supply them with food.

They leave in warm water, causing bleaching.

The diploid cell formed when a male gamete fuses with the oosphere.

It divides by mitosis to give the embryo.