Biology › Checklist

A-level Biology revision checklist

All 608 objectives in the curriculum, taken straight from the lessons that teach them. Open a unit and tap the dot beside an objective to rate how confident you are.

Jump to: Scientific method and quantitative biology · Cells, microscopy and biological organisation · Biological molecules, water and inorganic ions · Enzymes and metabolic control · Membranes and transport across cells · Nucleic acids, genomes and protein synthesis · Cell cycles, reproduction and development · Exchange surfaces and gas exchange · Plant transport and mineral nutrition · Animal transport and cardiovascular biology · Nutrition, digestion and health evidence · Pathogens, disease and immunity · Respiration and cellular energy · Photosynthesis and primary productivity · Nervous coordination, receptors and muscles · Hormonal communication, plant responses and homeostasis · Inheritance and population genetics · Gene regulation, genomics and biotechnology · Classification, biodiversity and conservation · Evolution and speciation · Ecology, populations and environmental change

not started!needs work~partly confident✓confident

Scientific method and quantitative biology

Variables and controls: what an experiment can show AQA Practical skills PS 1.1-1.2, PS 2.1-2.4, PS 3.1-3.3 · OCR A Module 1.1.1-1.1.3 · CAIE Paper 3 and Paper 5 (planning, analysis and evaluation) · Edexcel A 1.8, 1.9, 1.17, 5.14, 5.20, 7.13

  • Name the independent, dependent and controlled variables in an investigation you have not seen before, and justify the levels chosen.
  • Distinguish a control variable from a control experiment, and say which of the two a question is asking about.
  • Explain what a negative control rules out and what a positive control rules out, and why those are different jobs.
  • Identify a confounding variable and explain why repeating the measurement does not deal with it.
  • Set out the evidence that would raise a correlation to a causal claim.
  • Use validity, accuracy, precision, repeatability and reproducibility to mean five different things.
  • Plan an investigation on a living animal, such as the effect of caffeine on Daphnia heart rate, with its controls and a risk assessment.
  • Discuss the ethical issues in using invertebrates in research, using the 3Rs and what is known about sentience, and reach a judgement.

Handling data: units, scales, rates and uncertainty AQA MS 0.1-0.5, MS 1.1, MS 1.3, MS 1.8, MS 1.11, MS 2.2, MS 2.5, MS 3.1, MS 3.5, MS 3.6 · OCR A Module 1.1.3-1.1.4; mathematical requirements · CAIE Papers 3 and 5; mathematical requirements · Edexcel A 1.8, 5.14

  • Convert between units across the prefixes biology uses, and write very large and very small quantities in standard form.
  • Give an answer to a number of significant figures justified by the measurements it came from.
  • Calculate a percentage change and a percentage change relative to a stated reference value, and say which one a question requires.
  • Find a rate as a gradient, including by drawing a tangent to a curve, and state its units.
  • Explain why a logarithmic scale is used for population size and for pH, and read a value off one.
  • Find the percentage uncertainty in a measurement and combine uncertainties through a calculation.

Averages, spread and the null hypothesis AQA MS 1.2, MS 1.3, MS 1.5-1.7, MS 1.9-1.11 · OCR A Module 1.1.4; mathematical requirements (statistics) · CAIE Paper 5 (analysis, conclusions and evaluation) · Edexcel A 1.9 · Edexcel B 10.1 vi

  • Choose between a mean, a median and a mode for a given set of biological data, and say why.
  • Calculate a standard deviation and explain what it shows that a range does not.
  • Interpret error bars, including what non-overlapping bars do and do not prove.
  • State a null hypothesis naming both variables and the populations.

Choosing, carrying out and concluding a statistical test AQA 3.6.1.1 (taxes and kineses), 3.7.1 (chi-squared against a predicted ratio), MS 1.2, MS 1.3, MS 1.5-1.7, MS 1.9-1.11 · OCR A Module 1.1.4; mathematical requirements (statistics) · CAIE 16.2 (chi-squared), 17.1 (the t-test), 18.2 (Spearman and Pearson), Paper 5 (analysis, conclusions and evaluation) · Edexcel A Mathematical skills appendix (statistics) · Edexcel B 8.2 vi, 10.1 vi

  • Choose between chi-squared, a t-test and Spearman's rank for a given question, and find the degrees of freedom.
  • Compare a calculated value with a critical value and write a conclusion containing all four required elements.
  • Name the condition each test assumes, and say what to do when the data do not meet it.
  • Choose between Spearman's rank and Pearson's linear correlation coefficient for a given set of paired data, and justify the choice.
Cells, microscopy and biological organisation

Eukaryotic cell structure and organelles AQA 3.2.1.1 · OCR A 2.1.1 (g)-(j) · CAIE 1.2 · Edexcel A 3.1, 3.2, 3.3, 3.5, 4.7, 4.8 · Edexcel B 2.1 iii, 2.1 v, 5.4 i, 5.4 v, 5.7 i

  • Describe the ultrastructure of an animal cell and of a plant cell, and say which structures belong to which.
  • Link the structure of the nucleus, mitochondrion, chloroplast, Golgi apparatus, lysosome and both kinds of endoplasmic reticulum to what each does.
  • Put the organelles of the secretory pathway in the order a protein meets them.
  • State where 80S and 70S ribosomes are found, and what a ribosome is made of.
  • Name the structures a plant cell has and an animal cell does not, and give a function for each.
  • Name the three fibre types of the cytoskeleton with a role for each, and describe how motor proteins, cilia and flagella produce movement.
  • Describe amyloplasts, pits and the middle lamella, and tell an amyloplast from a chloroplast in an electron micrograph.

Microscopy, magnification and resolution AQA 3.2.1.3 · OCR A 2.1.1 (a) and (b), 2.1.1 (e) and (f) · CAIE 1.1 · Edexcel A 3.5, 4.8 · Edexcel B 2.1 vi, 2.1 vii

  • Define magnification and resolution and explain why they are not the same thing.
  • Explain why an electron microscope resolves finer detail than a light microscope.
  • Compare a light microscope, a TEM and an SEM by beam, resolution, specimen and the kind of image each produces.
  • Rearrange and use magnification = image size ÷ actual size, converting units correctly.
  • Describe how an eyepiece graticule is calibrated with a stage micrometer, and explain why artefacts appear in electron micrographs.
  • Describe cell fractionation and ultracentrifugation, and justify the cold, isotonic, buffered solution and the order the organelles pellet in.

Prokaryotic cells and viruses AQA 3.2.1.2, 3.2.2 · OCR A 2.1.1 (k) · CAIE 1.2 · Edexcel A 3.1, 3.4, 4.14, 6.5, 6.6 · Edexcel B 2.1 iii, 2.1 iv, 2.2 i, 2.2 ii, 2.2 iii, 6.3 i, 6.4 i

  • Describe the structure of a prokaryotic cell and give a function for each part.
  • Compare prokaryotic and eukaryotic cells, including DNA, ribosomes and cell wall.
  • Explain what a plasmid is and why it is not part of the main chromosome.
  • Describe binary fission and calculate numbers of bacteria after a given time.
  • Describe the structure of a virus, using HIV, and justify the claim that viruses are not living.
  • Describe the lytic cycle and latency, using lambda phage, and explain why antiviral drugs must act on a stage of virus replication.

Cell specialisation and biological organisation AQA 3.2.1.1, 3.8.2.1 · OCR A 2.1.6 (h)-(m) · CAIE 1.2, 5.1, 7.1 · Edexcel A 3.11, 3.12, 3.13, 4.11 · Edexcel B 2.1 i, 2.1 ii, 4.7 i, 7.3 i

  • Explain how cells with identical DNA come to differ, in terms of gene expression.
  • Define totipotent, pluripotent and multipotent, and give a source of each.
  • Describe the levels of organisation from cell to organ system, with examples.
  • Relate the structure of squamous epithelium, ciliated epithelium, cartilage, xylem and phloem to their functions.
  • Explain why differentiated cells cannot usually be converted back into other cell types.
  • Explain how xylem vessels and sieve tubes both arise from one meristem, the procambium in a young stem and the vascular cambium in a thickening one.
  • State the three parts of cell theory and explain why it is a unifying concept in biology.

Plan diagrams and tissue sections OCR A 3.1.3, 4.1.1 · CAIE 7.1, 8.1, 9.1 · Edexcel B 2.1 vii, 4.4 vi

  • State the rules of the low-power plan diagram convention, and say what a plan diagram deliberately leaves out.
  • Draw the distribution of xylem and phloem in cross-sections of a root, a stem and a leaf of a herbaceous dicot.
  • Predict what transverse and longitudinal cuts through a stem will each show, and explain why one cut is not enough.
  • Describe the wall of the trachea and of a bronchus as layers in plan, and use the cartilage to tell the two apart.
  • Identify an erythrocyte, a neutrophil, a lymphocyte and a monocyte on a stained blood smear from size and nucleus alone.
Biological molecules, water and inorganic ions

Carbohydrate structure and function AQA 3.1.1, 3.1.2 · OCR A 2.1.2 · CAIE 2.1, 2.2 · Edexcel A 1.12, 1.13, 4.9, 4.10 · Edexcel B 1.1 i, 1.1 ii, 1.1 iii, 1.1 iv

  • Draw or recognise alpha and beta glucose, and say where the two differ.
  • Explain how a glycosidic bond forms, and say what is released when it does.
  • Name the two monosaccharides in maltose, sucrose and lactose.
  • Relate the structure of amylose, amylopectin, glycogen and cellulose to what each one does.
  • Carry out and interpret the Benedict's and iodine tests, including a quantitative Benedict's method.
  • Explain how the arrangement of microfibrils and lignin makes plant fibres strong, and measure and calculate the tensile strength of a fibre.
  • Evaluate the use of plant fibres and starch in place of oil-based plastics as a contribution to sustainability.

Lipids: triglycerides, phospholipids and ester bonds AQA 3.1.3 · OCR A 2.1.2 · CAIE 2.2 · Edexcel A 1.14 · Edexcel B 1.2 i, 1.2 ii, 1.2 iii, 1.2 iv, 9.9 v

  • Name the components of a triglyceride and the bond that joins them.
  • Explain how an ester bond forms, and count the water released.
  • Distinguish saturated from unsaturated fatty acids, and say what the double bond does.
  • Relate the structure of a triglyceride to its use as an energy store.
  • Explain why a phospholipid behaves differently in water from a triglyceride, and carry out the emulsion test.

Water and inorganic ions AQA 3.1.7, 3.1.8 · OCR A 2.1.2 · CAIE 2.4 · Edexcel A 1.2, 4.12 · Edexcel B 1.6 i, 1.7 i

  • Explain why a water molecule is polar, and how a hydrogen bond forms between two of them.
  • Derive each property of water from its hydrogen bonding rather than listing the properties.
  • Give a biological consequence of each property, naming an organism or a process.
  • Explain why ice floats, and what that means for life in a pond in winter.
  • State the role of hydrogen, iron, sodium, potassium, phosphate, calcium and nitrate ions, and of ammonium, chloride, hydrogencarbonate and hydroxide.

Protein structure and function AQA 3.1.4.1 · OCR A 2.1.2 (k)-(o) · CAIE 2.3.1-2.3.8 · Edexcel A 2.9 · Edexcel B 1.3 i, 1.3 ii, 1.3 iii, 1.3 iv, 1.3 v, 1.5 i

  • Draw the general structure of an amino acid and say what varies between the twenty.
  • Explain how a peptide bond forms, and what is released when it does.
  • Name the four levels of protein structure and the bond holding each one together.
  • Account for the difference between a globular and a fibrous protein using haemoglobin and collagen.
  • Explain denaturation in terms of bonds rather than in terms of the protein being 'killed'.
Enzymes and metabolic control

Enzyme action and specificity AQA 3.1.4.2 · OCR A 2.1.4 (a) and (c) · CAIE 3.1 · Edexcel A 2.10 · Edexcel B 1.5 i, 1.5 ii, 1.5 iii

  • State what an enzyme does to the activation energy of a reaction, and what it leaves alone.
  • Describe the active site as a product of tertiary structure rather than of any one amino acid.
  • Set out the lock-and-key and induced fit models, and give the evidence that decided between them.
  • Use 'enzyme-substrate complex' and 'complementary' correctly in an explanation of specificity.
  • Explain why changing one amino acid far from the active site can still stop an enzyme working.

Factors affecting enzyme rate: temperature, pH and concentration AQA 3.1.4.2 · OCR A 2.1.4 (d) · CAIE 3.2 · Edexcel A 2.10, 5.16 · Edexcel B 1.5 iv, 1.5 v, 9.1 ii

  • Explain why the rate of an enzyme-catalysed reaction falls during a run, and why initial rate is the only fair comparison between conditions.
  • Account for the shape of the temperature curve as the sum of two opposing effects, and calculate a Q10.
  • Explain the effect of pH in terms of charge on R groups and the bonds that depend on it.
  • Interpret a substrate-concentration curve, naming what is limiting the rate in each part of it.
  • Draw all four curves with the right shape, including the asymmetry of the temperature curve.
  • Measure the initial rate of an enzyme-controlled reaction with a buffer, separate equilibration and controls, and calculate Q10 from two of your own runs.

Enzyme inhibition and metabolic control AQA 3.1.4.2 · OCR A 2.1.4 (f), 6.2.1 (i) · CAIE 3.2 · Edexcel A not examined as a topic · Edexcel B 1.5 vi

  • Distinguish competitive from non-competitive inhibition by where the inhibitor binds and what it does to the active site.
  • State the effect of each type on Vmax and on Km, and explain both effects in words rather than by quoting the graph.
  • Explain why raising the substrate concentration relieves one kind of inhibition and not the other.
  • Describe end-product inhibition and say why acting on the enzyme catalysing the first committed step of a pathway is the efficient choice.
  • Give the advantages of immobilising an enzyme for an industrial process, and one disadvantage.

Cofactors, coenzymes and where enzymes work OCR A 2.1.4 (b) and (e) · CAIE 3.1, 3.2 · Edexcel A 2.10, 3.3 · Edexcel B 1.5 vii

  • Describe how a coenzyme works, and distinguish a cofactor ion, a coenzyme and a prosthetic group with a named example of each.
  • Explain why a vitamin shortage slows enzyme-controlled reactions, using NAD and coenzyme A as the examples.
  • Classify enzymes as intracellular or extracellular, placing catalase, amylase and trypsin correctly.
  • Explain why the digestion of food has to be carried out by secreted, extracellular enzymes.
  • Use Km to compare the affinity of two enzymes for the same substrate, and predict which one matters when the substrate is scarce.
Membranes and transport across cells

Membrane structure and the fluid mosaic model AQA 3.2.3 · OCR A 2.1.5 (a)-(c) · CAIE 4.1 · Edexcel A 2.2 · Edexcel B 1.2 iv, 4.2 i, 4.2 iii, 4.2 iv

  • Explain why a phospholipid bilayer forms without anything assembling it.
  • Label a fluid mosaic membrane and give the job of every component on it.
  • Distinguish intrinsic from extrinsic proteins, and channel from carrier proteins.
  • Outline cell signalling at the membrane: a ligand secreted, transported and bound by a complementary receptor on a target cell.
  • Describe what cholesterol does at high temperature and at low temperature, and say why those two effects are not contradictory.
  • Explain how temperature and organic solvents change permeability, and describe the beetroot investigation that measures it.

Diffusion and osmosis AQA 3.2.3 · OCR A 2.1.5 (d)-(f) · CAIE 4.2 · Edexcel A 2.1, 2.3, 2.4 · Edexcel B 4.2 ii, 4.2 iii, 4.2 iv

  • Define simple and facilitated diffusion and say what distinguishes them.
  • State how rate of diffusion depends on surface area, concentration difference and thickness, and apply that to a named exchange surface.
  • Define osmosis using water potential, and use the relationship between water potential, solute potential and pressure potential.
  • Explain what happens to a plant cell and to an animal cell placed in a solution of lower water potential than their contents.
  • Describe how a dilution series of sucrose is used to find the water potential of potato tissue.
  • Describe how Visking tubing and agar model diffusion and osmosis, and how agar blocks of different sizes show what surface area to volume ratio does to exchange.

Active transport, co-transport and bulk transport AQA 3.2.3, 3.3.3 · OCR A 2.1.5 (g)-(h) · CAIE 4.2 · Edexcel A 2.4 · Edexcel B 4.2 iv, 4.2 v

  • Explain how a carrier protein moves a substance against its concentration gradient, and where the energy comes from.
  • Describe the sodium-potassium pump, quoting what moves in each direction for each ATP hydrolysed.
  • Work through co-transport of glucose in the ileum as an ordered sequence, and say which step uses ATP.
  • Distinguish endocytosis from exocytosis and give a named example of each.
  • Compare all the transport mechanisms by direction, proteins used and energy required.
Nucleic acids, genomes and protein synthesis

DNA and RNA structure AQA 3.1.5.1, 3.4.1 · OCR A 2.1.3 · CAIE 6.1 · Edexcel A 2.5 · Edexcel B 1.4 i, 1.4 iv, 1.4 v

  • Draw a nucleotide and name its three components.
  • Explain how the sugar-phosphate backbone is built and what is released as it forms.
  • State which bases pair, how many hydrogen bonds hold each pair, and why the pairing cannot be swapped around.
  • Say what 5′ and 3′ mean, and why the two strands are called antiparallel.
  • Account for four features of DNA structure in terms of the job the molecule does.
  • Compare DNA with mRNA, tRNA and rRNA, and give each kind of RNA its role.

DNA replication AQA 3.1.5.2 · OCR A 2.1.3 · CAIE 6.1 · Edexcel A 2.11, 2.12 · Edexcel B 1.4 ii, 1.4 viii, 1.4 ix

  • Explain what semi-conservative replication means, in terms of what happens to the original strands.
  • Describe the roles of helicase and DNA polymerase, naming the bonds each one deals with.
  • Explain why one new strand is made continuously and the other in fragments.
  • Describe the Meselson-Stahl experiment and explain how its results eliminated two competing models.
  • Explain how a replication error becomes a mutation, and why most cause no harm.
  • Describe how DNA is extracted and precipitated from tissue, giving the job of the detergent, the salt, the protease and the ice-cold ethanol.

The genetic code and transcription AQA 3.4.1, 3.4.2 · OCR A 2.1.3, 6.1.1 · CAIE 6.2 · Edexcel A 2.6, 2.7, 2.8, 6.10 · Edexcel B 1.4 iii, 1.4 vi, 1.4 vii, 7.1 i, 7.2 iii

  • State the four properties of the genetic code and explain a consequence of each.
  • Explain, with numbers, why the code has to be read in threes rather than ones or twos.
  • Distinguish exons from introns, and a gene from the genome.
  • Describe transcription in sequence, naming the enzyme, the strand used and the bonds involved.
  • Explain what splicing does and why one gene can give rise to more than one polypeptide.
  • Explain why many base substitutions change nothing about the protein.

Translation and protein synthesis AQA 3.4.2 · OCR A 2.1.3 · CAIE 6.2 · Edexcel A 2.6 · Edexcel B 1.4 iv, 1.4 v, 1.4 vi

  • Describe the structure of a ribosome and say what its two binding sites hold.
  • Explain the relationship between a codon and an anticodon, and say which molecule carries which.
  • Describe initiation, elongation and termination in order.
  • Explain where the energy for protein synthesis comes from and roughly how much is needed.
  • Describe what happens to a polypeptide after it leaves the ribosome.
  • Work from a given DNA sequence to the amino acid sequence it specifies.
Cell cycles, reproduction and development

The cell cycle and mitosis AQA 3.2.2 · OCR A 2.1.6 · CAIE 5.1, 5.2 · Edexcel A 3.10 · Edexcel B 2.1 vii, 2.3 i, 2.3 ii, 2.3 iii

  • Describe what happens in each phase of the cell cycle, and say which phase takes longest.
  • State what each of the three checkpoints checks, and what becomes of a cell that fails one.
  • Explain why a chromosome has two chromatids before mitosis and one after it.
  • Explain why replication leaves the end of the lagging strand uncopied, and say what a telomere therefore protects and what telomerase does about it.
  • Put the four stages of mitosis in order and say what defines each one, including what the spindle does.
  • Calculate a mitotic index from a count of cells and interpret what it means.
  • Describe binary fission in a prokaryote and set it against mitosis in a eukaryote.
  • Explain how uncontrolled cell division leads to a tumour, using the cycle's checkpoints.
  • Prepare a stained root tip squash, count its cells by fixed rules, and work out how long each stage of mitosis lasts from the counts.

Stem cells and cell potency AQA 3.8.2.1 · OCR A 2.1.6 · CAIE 5.1 · Edexcel A 3.11, 8.14 · Edexcel B 7.2 v, 7.3 i, 7.3 ii, 7.3 iii, 7.3 iv, 7.3 v

  • Define a stem cell, and say what self-renewal adds to being unspecialised.
  • Place a named cell at the right level of potency and justify the placement.
  • Give a real example of a totipotent, a pluripotent, a multipotent and a unipotent cell.
  • State where stem cells are obtained from, and what potency each source gives.
  • Explain why a specialised cell still carries every gene it will never use.
  • Set out the positions people hold on using embryos as a source, and the reasoning behind each.

Gametes, fertilisation and early development Edexcel A 3.6, 3.7 · Edexcel B 2.4 i, 2.4 ii, 2.4 iii, 7.3 iii

  • Describe spermatogenesis and oogenesis, and give three ways in which they differ.
  • Relate each structure of a sperm and of an egg to the job that structure does.
  • Describe the acrosome reaction in the order the events happen.
  • Explain how the cortical reaction prevents polyspermy, and why polyspermy has to be prevented.
  • Describe what happens between fertilisation and implantation, and state where each takes place.

Sexual reproduction in flowering plants Edexcel B 2.5 i, 2.5 ii, 2.5 iii

  • Name the parts of a flower and give the job of each, including the parts of the stamen and of the carpel.
  • Describe how a pollen grain forms in the anther, naming each division as meiosis or mitosis.
  • Describe how the embryo sac forms in the ovule, and give the position of each of its eight nuclei.
  • Explain how the male nuclei reach the embryo sac, including the roles of the tube nucleus, the pollen tube and the enzymes it secretes.
  • Describe double fertilisation, and state the number of chromosome sets in the zygote and in the endosperm.
  • Plan and explain an investigation into the effect of sucrose concentration on pollen tube growth or germination.

Homeobox genes, Hox genes and apoptosis OCR A 6.1.1

  • State what the homeobox is, how long it is, and what the homeodomain it codes for does.
  • Explain why a homeobox gene can change a whole body region although it codes for only one protein.
  • Describe the colinear arrangement of a Hox cluster, and say what colinearity means.
  • Describe the stages of apoptosis in order, and give the signals that control it.
  • Explain how mitosis and apoptosis together produce a structure, using the separation of the digits.
  • Explain what follows when the balance between mitosis and apoptosis is lost, in either direction.

Cloning in plants and animals OCR A 6.2.1 · Edexcel A 8.18 · Edexcel B 2.3 iii

  • Define a clone, and explain why every cell produced by mitosis from one parent belongs to one.
  • Describe natural vegetative propagation, with named structures and named plants.
  • Describe how a cutting is taken and how micropropagation is carried out, step by step.
  • Argue the case for and against micropropagation as a commercial method.
  • Describe embryo splitting and somatic cell nuclear transfer, and say what each product inherits and from whom.
  • Evaluate reproductive cloning against therapeutic cloning, using what potency means.
Exchange surfaces and gas exchange

Surface area to volume ratio: why size limits diffusion AQA 3.3.1 · OCR A 3.1.1 · CAIE 4.2 · Edexcel A 1.1, 2.1 · Edexcel B 4.1 i, 4.1 ii, 4.3 i

  • Calculate a surface area to volume ratio for a cube, a sphere and a flattened body, and say what happens to it as the body gets bigger.
  • Explain why shape changes the ratio even when the volume is fixed.
  • State Fick's law as a proportionality and use it to predict how a change in area, gradient or thickness changes the rate.
  • Explain why diffusion works over micrometres and fails over millimetres.
  • List the features shared by specialised exchange surfaces and account for each one in terms of Fick's law.

Gas exchange in mammals: lungs and ventilation AQA 3.3.2 · OCR A 3.1.1 · CAIE 9.1 · Edexcel A 2.1, 7.1, 7.9 · Edexcel B 4.3 i

  • Trace air from the trachea to an alveolus and name the tissues in the wall at each level.
  • Recognise trachea, bronchus, bronchiole and alveolus in a section, and justify the identification from what is in the wall.
  • Describe inspiration and expiration in the correct causal order: muscles, then volume, then pressure, then air.
  • Explain why quiet expiration costs almost nothing while inspiration always costs energy.
  • Calculate pulmonary ventilation rate, and read tidal volume, vital capacity and breathing rate off a spirometer trace.
  • Read FEV₁ and FVC off a forced breath out, and use them to explain how pulmonary fibrosis, tuberculosis, asthma and emphysema affect ventilation and gas exchange.
  • Evaluate the evidence linking smoking, pollution and dust to lung disease, separating correlation from cause, and explain how it led to laws such as the ban on smoking in enclosed public places.
  • Use spirometer traces taken at rest and after exercise to find tidal volume, breathing rate, respiratory minute ventilation and oxygen consumption.

Gas exchange in insects, fish and plants AQA 3.3.2 · OCR A 3.1.1, 3.1.3 · CAIE 7.2 · Edexcel B 4.3 i, 4.3 ii

  • Trace the path of oxygen from a spiracle to an insect's muscle cell and say why its blood plays little or no part.
  • Explain how tracheal fluid moves during activity and why that speeds up gas exchange.
  • Describe the structure of a bony fish gill from arch to lamella, and the buccal pump that drives water over it.
  • Explain why counter-current flow extracts far more oxygen than parallel flow would, using the gradient along the lamella.
  • Describe how a leaf exchanges gases and explain the trade-off that forces xerophyte adaptations.
  • Dissect an insect's tracheal system and a fish gill safely, and record each in a labelled biological drawing with a scale.
Plant transport and mineral nutrition

Xylem and the transpiration stream AQA 3.3.4.2 · OCR A 3.1.3 · CAIE 7.1, 7.2 · Edexcel A 4.10, 4.11, 4.12 · Edexcel B 1.6 i, 4.7 i, 4.7 ii, 4.7 iii

  • Describe how a root hair cell is built for absorbing water and mineral ions.
  • Trace water across the root cortex by the apoplast and symplast routes, and say where each one has to cross a membrane.
  • Explain what the Casparian strip does and why it hands the plant control over what reaches the xylem.
  • Account for every feature of a xylem vessel in terms of the job the tissue does.
  • State the cohesion-tension theory and name the property of water each step depends on.
  • Set up a potometer, and say exactly which quantity the reading is.
  • Name the ions a plant takes up and what a shortage of each one looks like.
  • Compare sclerenchyma fibres, xylem vessels and phloem in structure, position in the stem and function, and find each one in a stained stem section.
  • Investigate a plant mineral deficiency with culture solutions, and explain the symptoms from the ion that is missing.

Transpiration and stomatal control AQA 3.3.2, 3.3.4.2 · OCR A 3.1.3 · CAIE 7.2, 14.2 · Edexcel A not examined as a topic · Edexcel B 4.3 ii, 4.7 iv

  • Define transpiration and explain why a photosynthesising plant cannot avoid it.
  • Predict and explain the effect of light, temperature, humidity and air movement on the rate, saying whether each acts through the water potential gradient or through stomatal aperture.
  • Describe how a guard cell opens a stoma, from the proton pump to the turgor.
  • Explain why the daily cycle of stomatal opening is called a rhythm rather than a response, using the result of keeping a plant in constant conditions.
  • Describe how abscisic acid closes a stoma, naming calcium ions as the second messenger that opens the anion channels.
  • Explain why the shape and wall thickness of a guard cell turn turgor into an open pore rather than a fatter cell.
  • Account for xerophyte and hydrophyte adaptations by saying what each does to the water potential gradient.
  • Process potometer data: calculate rates, compare conditions and state what was controlled.

Phloem translocation and the mass-flow hypothesis AQA 3.3.4.2 · OCR A 3.1.3 · CAIE 7.1, 7.2 · Edexcel A 4.11 · Edexcel B 4.7 i, 4.7 v

  • Describe a sieve tube element and a companion cell, and relate each feature to the job it does.
  • Explain how sucrose is loaded into a sieve tube at a source, naming the pump and the co-transporter.
  • Explain how loading and unloading create the pressure gradient that mass flow depends on.
  • Identify sources and sinks, including an organ that is both at different times of year.
  • Describe ringing, aphid stylet and tracer experiments and say what each one does and does not establish.
  • Evaluate the mass flow hypothesis, giving evidence on both sides.
Animal transport and cardiovascular biology

The heart and cardiac cycle AQA 3.3.4.1, 3.6.1.3 · OCR A 3.1.2 (a) and (b), 3.1.2 (e)-(h), 5.1.5 (k) · CAIE 8.1, 8.3 · Edexcel A 1.1, 1.4, 7.8, 7.9 · Edexcel B 4.1 ii, 4.4 i, 4.4 ii, 4.4 iii, 4.4 iv, 4.4 v, 9.5 iv, 9.8 i, 9.8 ii

  • Explain why a large, active animal needs a mass transport system when a flatworm does not.
  • Say what double circulation gives a mammal that single circulation cannot.
  • Label the mammalian heart and account for the thickness of the left ventricle wall in terms of the pressure it generates.
  • Describe the three stages of the cardiac cycle, giving the pressure change responsible for every valve movement.
  • Read a pressure-against-time graph: identify each curve and mark where each valve opens and shuts.
  • Calculate cardiac output, stroke volume or heart rate from the other two.
  • Trace an impulse from the SAN to the ventricle walls and explain why the delay at the AVN matters.
  • Say what an electrocardiogram measures, and state which part of the conduction pathway each of the P wave, QRS complex and T wave records.
  • Calculate a heart rate from the interval between R peaks on a trace, and identify tachycardia, bradycardia, atrial fibrillation and an ectopic beat from what the trace looks like.
  • Explain how chemoreceptors and pressure receptors, the medulla and the autonomic nerves change heart rate, as a negative feedback loop.

Blood vessels, tissue fluid and lymph AQA 3.3.4.1 · OCR A 3.1.2 (b)-(d) · CAIE 8.1 · Edexcel A 1.3 · Edexcel B 4.4 i, 4.4 vi, 4.4 vii, 4.6 i, 4.6 ii

  • Compare an open circulatory system with a closed one, and say what a closed system gives an animal in delivery rate and in control.
  • Relate the structure of an artery, arteriole, capillary, venule and vein to its function and to the pressure it carries.
  • Distinguish an elastic artery from a muscular artery by the composition of its wall, its distance from the heart and the job it does.
  • Explain why a capillary wall is one cell thick and why the blood moves through it slowly.
  • Account for the formation of tissue fluid at the arteriole end of a capillary bed using hydrostatic and oncotic pressure.
  • Account, in the A-level examination model, for the return of most of that fluid at the venule end using the same two pressures.
  • Describe what the lymphatic system does with the fluid that is not returned.
  • Explain three different causes of oedema using nothing but hydrostatic and oncotic pressure.

Haemoglobin and oxygen dissociation curves AQA 3.3.4.1 · OCR A 3.1.2 (i)-(j) · CAIE 2.3, 8.2 · Edexcel A 2.9 · Edexcel B 4.4 vii, 4.5 i, 4.5 ii, 4.5 iii, 4.5 iv

  • Describe haemoglobin as a conjugated globular protein and say how many oxygen molecules one molecule carries.
  • Explain cooperative binding and use it to account for the sigmoid shape of the dissociation curve.
  • Read percentage saturation off a dissociation curve and calculate how much oxygen is unloaded between two partial pressures.
  • Explain the Bohr shift and why it is useful in exercising muscle.
  • Interpret a curve that lies to the left or to the right of the human adult curve, including fetal, high-altitude and small-mammal haemoglobins.
  • Describe how carbon dioxide is carried, including the role of carbonic anhydrase and the chloride shift.
Nutrition, digestion and health evidence

Digestion and absorption in the human gut AQA 3.3.3 · OCR A 2.1.4, 2.1.5 (the enzymes and the membrane transport only) · CAIE 4.2 (membrane transport only) · Edexcel A not examined as a topic · Edexcel B 1.1 iii, 1.5 vii

  • Describe digestion as hydrolysis, and say what physical digestion contributes to it.
  • Name the enzymes acting on carbohydrate, protein and lipid, and state where each works.
  • Explain why endopeptidases are needed before exopeptidases can work quickly.
  • Explain emulsification as an argument about surface area, and calculate the change.
  • Describe the role of micelles in lipid absorption, and say what is and is not absorbed.
  • Explain the co-transport of glucose and amino acids with sodium ions, and say where the ATP is spent.

Diet, energy and how to read a health claim AQA 3.3.4.1 (evaluating risk-factor data) · OCR A 2.1.2 (the molecules a diet supplies) · CAIE not examined as a topic · Edexcel A 1.7, 1.8, 1.9, 1.10, 1.11, 1.16, 4.13, 5.20, 7.13 · Edexcel B 4.4 ix

  • Define basal metabolic rate and state what a person's BMR mostly depends on.
  • Calculate an energy balance and explain why a small daily surplus does not extrapolate.
  • State what a diet must supply beyond energy, and give a named consequence of each shortfall.
  • Distinguish a cohort study, a case-control study and a randomised controlled trial by what each starts with.
  • Name the confounder, the reverse causation or the measurement problem in a given dietary study.
  • Convert a relative risk into an absolute risk, and say which one a reader needs.
  • Weigh two studies that disagree by their design, sample size and selection, control of confounding, measurement and funding, and say what would resolve the conflict.
  • Measure the vitamin C content of a food or drink with DCPIP against a standard of known concentration, and calculate it from the volumes.

Cholesterol, atheroma and what a risk factor means AQA 3.3.4.1 (risk factors and cardiovascular disease) · OCR A 2.1.2 (cholesterol as a lipid and what it is for) · CAIE not examined as a topic · Edexcel A 1.5, 1.6, 1.7, 1.15, 1.16, 1.18, 5.20, 7.13 · Edexcel B 4.4 viii, 4.4 ix

  • Describe cholesterol as a sterol and state four things the body needs it for.
  • Explain what a lipoprotein is and distinguish LDL from HDL by composition and function.
  • Describe the formation of an atheroma in sequence, from endothelial damage to a fibrous plaque.
  • Explain how a plaque leads to angina, to a myocardial infarction and to an aneurysm.
  • State precisely what the term 'risk factor' licenses you to claim, and what it does not.
  • Account for why the evidence on LDL is regarded as causal while the evidence on HDL is not.
Pathogens, disease and immunity

Pathogens and non-specific defences AQA 3.2.4 · OCR A 4.1.1 · CAIE 11.1 · Edexcel A 6.6, 6.7, 6.8, 6.11 · Edexcel B 6.2 i, 6.2 ii, 6.5 i, 6.7 i

  • Name the four groups of pathogen and give a disease caused by each.
  • Explain how a pathogen damages its host, using toxins and cell lysis as the two standard exam routes.
  • Distinguish a physical barrier from a chemical one, with named examples of both.
  • Describe phagocytosis as an ordered sequence, ending with antigen presentation.
  • Explain why an antibiotic that cures tuberculosis does nothing whatever for influenza.
  • Distinguish an exotoxin from an endotoxin, with Staphylococcus and Salmonella as the examples, and set both beside invasion of tissue by Mycobacterium tuberculosis.
  • Describe the transmission, mode of infection and pathogenic effect of the stem rust fungus, Puccinia graminis, on wheat.
  • Explain how interferon released by a virus-infected cell protects the cells around it.

The specific immune response AQA 3.2.4 · OCR A 4.1.1 · CAIE 11.1 · Edexcel A 6.8, 6.9 · Edexcel B 4.4 vii, 6.7 i, 6.7 ii, 6.7 iii, 6.7 iv

  • Explain what an antigen is and how a lymphocyte distinguishes self from non-self.
  • Describe clonal selection and clonal expansion, and say which cell does which.
  • Set out the roles of T-helper cells, T-killer cells, B cells, plasma cells and memory cells without confusing any two of them.
  • Put the events from infection to circulating antibody into the right order.
  • Account for the secondary response being faster, larger and longer-lasting than the primary one.
  • Name cytokines as the signal by which an activated T-helper cell stimulates B cells in the humoral response and T-killer cells in the cell-mediated response.

Antibodies, vaccination and the four kinds of immunity AQA 3.2.4 · OCR A 4.1.1 · CAIE 11.2 · Edexcel A 4.13, 6.8, 6.12, 6.13 · Edexcel B 2.2 v, 6.7 v, 6.7 vi, 6.7 vii

  • Describe the structure of an antibody and relate each feature to what it does.
  • Explain agglutination, neutralisation and opsonisation without claiming that antibodies destroy pathogens.
  • Classify an example of immunity as active or passive and natural or artificial, and justify the classification.
  • Explain how vaccination protects an unvaccinated person, and why a threshold coverage exists.
  • Explain why the influenza vaccine changes annually and the measles vaccine does not.
  • Describe how a monoclonal antibody is produced, from immunising a mouse to harvesting the antibody, and say what each of the two fused cells contributes.
  • Set out both sides of an ethical question about vaccine trials without asserting a conclusion.
  • Compare William Withering's testing of digitalis with a modern protocol of placebo-controlled, double-blind trials in three phases.
  • Evaluate the ethics of using an untested drug during an epidemic, with the 2014 Ebola outbreak as the case.

Infectious disease: transmission and control AQA not examined as a topic · OCR A 4.1.1 · CAIE 10.1 · Edexcel A 6.6, 6.11, 6.13 · Edexcel B 2.2 iv, 3.2 iv, 6.4 ii, 6.5 i, 6.6 i

  • Name the pathogen behind cholera, malaria, tuberculosis and HIV, down to the four Plasmodium species and the two mycobacteria.
  • State the route each of the four takes between hosts, and classify transmission routes in general.
  • Match a control measure to the step of transmission it interrupts.
  • Sort the controls for a named disease onto biological, social and economic axes, with an example of each.
  • Explain why tuberculosis has a vaccine and HIV, so far, does not.
  • Explain how the evasion mechanisms of pathogens support the theory of an evolutionary race between pathogens and their hosts.
  • Evaluate the ethical implications of methods of controlling endemic malaria, and describe how the scientific community validates a control method.

Plant disease and plant defences AQA not examined as a topic · OCR A 4.1.1, 5.1.5 · CAIE 15.2 · Edexcel A not examined as a topic

  • Name a bacterial and a viral plant disease, and describe the damage and the spread of each.
  • Explain containment: callose and lignin sealing plasmodesmata and sieve plates, with the timescale of each.
  • Give named chemical defences and state what each acts against.
  • Describe defences against herbivory: alkaloids, tannins, pheromone signalling and the Mimosa touch response.
  • Work through the Venus flytrap mechanism in order, and explain why the trap counts to two before it closes.
Respiration and cellular energy

Glycolysis, ATP and the link reaction AQA 3.1.6, 3.5.2 · OCR A 2.1.3, 5.2.2 · CAIE 12.1, 12.2 · Edexcel A 5.6, 7.3, 7.4, 7.5 · Edexcel B 4.2 vi, 5.1 i, 5.1 ii, 5.2 i, 5.3 i, 5.3 ii

  • Describe the structure of ATP and explain what its hydrolysis releases, with a figure.
  • Give three reasons ATP suits a cell better than releasing a glucose molecule's energy in one go.
  • State where each of the four stages of respiration happens, and why glycolysis needs no oxygen.
  • Describe glycolysis as phosphorylation, lysis and oxidation, with the net yield per glucose.
  • Describe the link reaction, naming the decarboxylation and the dehydrogenation.
  • Keep a running tally of ATP, reduced NAD and carbon dioxide per molecule of glucose.

The Krebs cycle and oxidative phosphorylation AQA 3.5.2 · OCR A 5.2.2 · CAIE 12.2 · Edexcel A 5.6, 7.3, 7.5, 7.6 · Edexcel B 5.1 ii, 5.3 i, 5.3 ii, 5.4 i, 5.4 ii, 5.4 iii, 5.4 iv, 5.4 v

  • Describe one turn of the Krebs cycle and account for all of the carbon that enters it.
  • State the products of the cycle per turn and per molecule of glucose.
  • Explain how electron transfer along the chain produces a proton gradient across the inner membrane.
  • Explain how the gradient is used to make ATP, naming the enzyme and the direction of proton movement.
  • State the role of oxygen precisely, and say what happens to the chain without it.
  • Explain why a measured ATP yield falls short of the theoretical 38.

Anaerobic respiration and the respiratory quotient AQA 3.5.2 · OCR A 5.2.2 · CAIE 12.1, 12.2 · Edexcel A 7.4, 7.7 · Edexcel B 5.5 i, 5.5 ii, 5.5 iii, 5.5 iv

  • Explain why glycolysis can continue without oxygen and what must be regenerated for it to do so.
  • Describe lactate fermentation and explain what happens to the lactate afterwards.
  • Describe ethanol fermentation in yeast and compare it with the animal route.
  • Compare anaerobic and aerobic yields per molecule of glucose.
  • Explain how lipids and proteins enter respiration and why lipid yields more energy per gram.
  • Calculate a respiratory quotient and interpret values of 0.7, 1.0 and above 1.0.
  • Describe how a respirometer is used, including its controls.
  • Describe the yeast and methylene blue investigation, saying what is mixed, what is varied and what is timed, and explain why boiled yeast is the control it needs.
  • Describe how to compare the rate of respiration of yeast in aerobic and anaerobic conditions, and explain why a gas syringe alone shows little change for the aerobic flask.

Exercise, sports medicine and performance-enhancing drugs Edexcel A 7.13, 7.14, 7.15

  • Explain how exercising too little increases the risk of obesity, cardiovascular disease and type 2 diabetes.
  • Describe the possible disadvantages of exercising too much, including wear and tear on joints and suppression of the immune system.
  • Interpret data on exercise and health, and say whether they show a correlation or a causal relationship.
  • Explain how keyhole surgery and prostheses enable people with injuries and disabilities to take part in sport.
  • Explain how anabolic steroids and EPO improve performance, and state the health risks of each.
  • Discuss the different ethical positions on whether athletes should be allowed to use performance-enhancing substances.
Photosynthesis and primary productivity

Chloroplast structure and the light-dependent reactions AQA 3.5.1 · OCR A 5.2.1 · CAIE 12.1, 13.1, 13.2 · Edexcel A 5.5, 5.7, 5.9 · Edexcel B 5.6 i, 5.6 ii, 5.7 i, 5.7 ii, 5.7 iii

  • Name the parts of a chloroplast and give each one a job it does in photosynthesis.
  • Explain why a leaf looks green, using the absorption spectrum of chlorophyll.
  • Say what an action spectrum measures and why it resembles an absorption spectrum.
  • Separate leaf pigments by chromatography and calculate an Rf value from your own chromatogram.
  • Describe the light-dependent reactions in order, from a photon to reduced NADP.
  • Distinguish non-cyclic from cyclic photophosphorylation by their products.
  • Isolate chloroplasts in cold, buffered, isotonic medium and use DCPIP to measure how a named factor changes the rate of the light-dependent reactions.

The Calvin cycle AQA 3.5.1 · OCR A 5.2.1 · CAIE 13.1 · Edexcel A 5.5, 5.8 · Edexcel B 5.7 iv, 5.7 v, 5.7 vi, 5.7 vii

  • Describe the three stages of the Calvin cycle and say where each takes place.
  • State what rubisco does and how many molecules of GP one turn produces.
  • Explain what reduced NADP and ATP each contribute to the reduction of GP.
  • Work out how many turns, how many TP and how much ATP a molecule of glucose costs.
  • Predict and explain the changes in GP, TP and RuBP when light or carbon dioxide is withdrawn.
  • Say what the sugars from the cycle become, nucleic acids included, and what else each product needs.
  • Predict and explain the effect of a change in temperature on the rate of the cycle and on the levels of GP, TP and RuBP.

Limiting factors and primary productivity AQA 3.5.1, 3.5.3 · OCR A 5.2.1, 6.3.1 · CAIE 13.2 · Edexcel A 5.10, 5.11 · Edexcel B 5.7 viii, 10.1 ii, 10.1 iii, 10.2 i, 10.2 ii

  • Identify the limiting factor from any region of a rate graph and justify the choice.
  • Explain what changes the gradient of such a graph and what changes the height of the plateau.
  • Use the principle of limiting factors to explain what a commercial grower controls, and why.
  • Define the compensation point and explain what it means for a plant's carbon balance.
  • Distinguish gross from net primary productivity and quote productivity in the correct units.
  • Calculate the percentage of energy transferred between trophic levels and explain why it is small.
  • Describe how biomass is measured as dry mass and its energy found by calorimetry, and use N = I − (F + R) for the net production of a consumer.
  • Describe how to measure the rate of photosynthesis of a whole plant, and how light intensity, carbon dioxide, temperature and wavelength are each varied.
  • Use the inverse square law to compare the light intensity from a lamp at different distances.
  • Compare pyramids of numbers, biomass and energy, with an advantage and a disadvantage of each.
  • Explain how farming raises the efficiency of energy transfer, by simplifying food webs to reduce energy losses to non-human food chains and by reducing respiratory losses within a human food chain.
Nervous coordination, receptors and muscles

Organisation of the nervous system AQA 3.6.1.3 (context) · OCR A 5.1.3, 5.1.5 · CAIE 15.1 (context) · Edexcel A 7.9, 7.12, 8.1, 8.2, 8.7, 8.8 · Edexcel B 4.4 iv, 9.4 i, 9.4 ii, 9.4 iii, 9.4 iv, 9.4 v, 9.5 iv, 9.8 i

  • Divide the nervous system into central and peripheral, and the peripheral system into somatic and autonomic.
  • Set sympathetic against parasympathetic, with the effects of each on the same named organs.
  • Locate the cerebrum, cerebellum, medulla oblongata, hypothalamus and pituitary, and give one function of each.
  • Distinguish sensory, relay and motor neurones by their structure: where the cell body sits, and dendron against axon.
  • Compare skeletal, involuntary and cardiac muscle as tissues, including which division of the nervous system controls each.
  • Explain how the circular and radial muscles of the iris constrict and dilate the pupil, and name the autonomic division that drives each.
  • Label a cross-section of the spinal cord, and trace a reflex arc through its dorsal root, grey matter and ventral root.

Receptors: transduction and the reflex arc AQA 3.6.1.1, 3.6.1.2 · OCR A 5.1.3, 5.1.5 · CAIE 15.1.3-15.1.5 · Edexcel A 8.2, 8.5 · Edexcel B 9.7 i, 9.7 ii, 9.7 iii

  • Put the stages from stimulus to response in order, and name the three neurones in a spinal reflex arc.
  • Explain what makes a reflex fast, and what it protects you from.
  • Describe how pressure on a Pacinian corpuscle produces a generator potential.
  • Distinguish a generator potential from an action potential, using the word graded correctly.
  • Describe how a taste bud chemoreceptor turns a dissolved chemical into an action potential in the sensory neurone at its base.
  • Compare rods and cones on sensitivity, acuity, pigment and distribution, and explain the first two using convergence.
  • Distinguish a taxis from a kinesis, and explain how each keeps a mobile organism in a favourable environment.
  • Describe the layers of the retina from the ganglion cells to the rods and cones, and explain why there is a blind spot.
  • Describe how to use a choice chamber or maze to investigate an animal's response to light or humidity, with its controls, and test the counts with chi-squared.

The action potential and its propagation AQA 3.6.2.1 · OCR A 5.1.3 · CAIE 15.1.6-15.1.8 · Edexcel A 8.1, 8.3 · Edexcel B 9.5 i, 9.5 ii, 9.5 iii, 9.6 i

  • Explain how the sodium-potassium pump and the membrane's permeability produce a resting potential of about −70 mV.
  • Describe depolarisation, repolarisation and hyperpolarisation in terms of which gates are open.
  • Explain how local currents carry an impulse along an unmyelinated axon.
  • State the all-or-nothing principle and say what does vary with stimulus strength.
  • Explain the refractory period and give its three consequences.
  • Account for conduction speed using myelination, axon diameter and temperature.
  • Explain how lidocaine acts as a local anaesthetic by blocking voltage-gated sodium channels.

The synapse: transmission, and why it runs one way AQA 3.6.2.2 · OCR A 5.1.3 · CAIE 15.1.9 · Edexcel A 8.4, 8.14, 8.15 · Edexcel B 9.5 iv, 9.5 v, 9.6 i

  • Label a cholinergic synapse and say what each part does.
  • Describe transmission across it in the right order, from arriving impulse to enzyme clearing the cleft.
  • Explain why transmission is unidirectional, using the position of vesicles and receptors.
  • Distinguish spatial from temporal summation, and explain what an inhibitory synapse does.
  • Compare a neuromuscular junction with a synapse between two neurones.
  • Explain how a named drug produces its effect at a synapse.
  • Explain how too little dopamine contributes to Parkinson's disease and too little serotonin to depression, and how L-Dopa, SSRIs and MDMA change transmission.

Muscles and movement: the sliding-filament model AQA 3.6.2.2, 3.6.3 · OCR A 5.1.5 · CAIE 15.1.10-15.1.12 · Edexcel A 6.1, 7.1, 7.2, 7.10 · Edexcel B 4.5 iii

  • Describe the structure of skeletal muscle from whole muscle down to the sarcomere.
  • Explain how an impulse at the neuromuscular junction leads to calcium release inside the fibre.
  • Describe the sliding filament mechanism, including the roles of calcium, tropomyosin, ATP and the myosin head.
  • State what happens to the A band, I band and H zone during contraction, and why.
  • Compare slow and fast twitch fibres, and explain how ATP is supplied to a working muscle.

Brain imaging, development and learning Edexcel A 8.9, 8.10, 8.11, 8.12, 8.13, 8.19

  • Describe what MRI, fMRI, PET and CT scans each detect, and say whether each shows the structure or the function of the brain.
  • Explain what happens in the visual cortex during the critical period, using Hubel and Wiesel's experiments with kittens and monkeys.
  • Explain why animal models have been used in research into brain development and function, and the limits of what they show.
  • Discuss the use of animals in medical research from two ethical standpoints.
  • Explain how habituation happens at a synapse, and describe how to investigate habituation to a stimulus.
  • Evaluate the methods used to investigate nature and nurture in brain development: new-born babies, animal experiments, damaged brain areas, twin studies and cross-cultural studies.
Hormonal communication, plant responses and homeostasis

Hormonal communication and negative feedback AQA 3.6.4.1 · OCR A 5.1.1, 5.1.4 · CAIE 14.1, 15.1 · Edexcel A 7.11, 7.12, 7.16, 8.7 · Edexcel B 9.1 i, 9.1 ii, 9.1 iii, 9.2 i, 9.2 ii, 9.8 ii, 9.9 iv

  • Distinguish an exocrine gland from an endocrine gland by where its secretion goes.
  • Describe the relationship between the hypothalamus and the two lobes of the pituitary.
  • Explain why a peptide hormone needs a second messenger and a steroid hormone does not.
  • Describe the adrenaline cascade in order, from binding to glucose leaving the liver cell.
  • Explain negative feedback using receptor, coordinator and effector, and say what positive feedback does instead.
  • Compare nervous and hormonal coordination on speed, route, duration and target.

Regulation of blood glucose and diabetes mellitus AQA 3.6.4.2 · OCR A 5.1.4 · CAIE 14.1 · Edexcel A 1.11, 7.13

  • State the normal blood glucose concentration and name the three places glucose in the blood comes from.
  • Describe the effects of insulin and of glucagon, naming the cells that secrete each.
  • Use glycogenesis, glycogenolysis and gluconeogenesis correctly.
  • Describe how a beta cell secretes insulin, from glucose entering to vesicles fusing.
  • Distinguish type 1 from type 2 diabetes by cause, and say how each is managed.
  • Explain how a glucose test strip and a biosensor work, naming glucose oxidase and peroxidase.
  • Read a glucose tolerance test curve and justify a diagnosis from it.

Osmoregulation and kidney function AQA 3.6.4.3 · OCR A 5.1.2 · CAIE 14.1 · Edexcel B 9.1 ii, 9.9 i, 9.9 ii, 9.9 iii, 9.9 iv, 9.9 v

  • Label a kidney in section, from the fibrous capsule to the renal pelvis.
  • Label a nephron and name the parts in the order the filtrate meets them.
  • Explain ultrafiltration in terms of hydrostatic pressure and the three layers of the barrier.
  • Describe selective reabsorption at the proximal convoluted tubule, including co-transport.
  • Explain how the loop of Henle builds a concentration gradient in the medulla.
  • Describe the control of water potential by osmoreceptors, ADH and aquaporins.
  • State what a dialysis fluid must contain, and justify each component.

The liver: detoxification, deamination and the making of urea OCR A 5.1.2 · CAIE 14.1 · Edexcel B 9.9 ii

  • Define excretion, name the two waste products it mainly deals with, and say which organ removes each.
  • Name the liver's three blood vessels and state what the blood in each of them is carrying.
  • Describe a liver lobule, and relate sinusoids, hepatocytes and Kupffer cells to what the organ does.
  • Explain how the liver detoxifies a substance, using the breakdown of alcohol through ethanal as the worked case.
  • Describe deamination and the ornithine cycle in order, saying where in the cell each step happens.
  • Explain why an animal spends ATP turning ammonia into urea rather than excreting the ammonia itself.

Thermoregulation in endotherms and ectotherms AQA 3.6.4.1 · OCR A 5.1.1 · CAIE not examined as a topic · Edexcel A 5.16, 7.12 · Edexcel B 5.1 i, 9.1 ii, 9.9 vi, 9.9 vii

  • Explain why a mammal controls its core temperature, in terms of what temperature does to enzymes.
  • Distinguish peripheral from central thermoreceptors by what each of them detects.
  • Describe the responses of the skin, muscle and liver to cold and to heat, in the vocabulary of negative feedback.
  • Explain vasoconstriction and vasodilation correctly, naming the arterioles and the shunt vessels.
  • Describe how an ectotherm regulates its temperature by behaviour and posture.
  • Compare the costs and benefits of the two strategies, arguing the case both ways.

Plant responses: tropisms, auxins and the classic experiments AQA 3.6.1.1 · OCR A 5.1.5 · CAIE 15.2, 14.2 · Edexcel A 8.6 · Edexcel B 9.3 i, 9.3 ii, 9.3 iii, 9.3 iv

  • Define a tropism and name the common ones with their stimulus and direction.
  • State what Darwin's, Boysen-Jensen's and Went's experiments each establish, and what they do not.
  • Explain how auxin causes a cell to elongate, using the cell wall.
  • Explain why the same auxin distribution bends a shoot upwards and a root downwards.
  • Describe apical dominance and the evidence that auxin from the apical bud causes it.
  • Describe the effects of gibberellins and of abscisic acid.
  • Give a commercial use of a plant growth substance and explain how it works.
  • Describe the two forms of phytochrome and how red light, far-red light and darkness convert one into the other.
  • Describe etiolation and explain how phytochrome brings about photomorphogenesis when a seedling reaches light.
  • Explain how phytochrome controls flowering in long-day and short-day plants, using the results of night-break experiments.
  • Explain how IAA and phytochrome each change the transcription of genes.
  • Investigate the effect of gibberellin on amylase production in cereal grains with a starch agar assay, and process the clear zones into areas.
Inheritance and population genetics

Meiosis and the sources of genetic variation AQA 3.4.3 · OCR A 2.1.6 · CAIE 16.1 · Edexcel A 3.9 · Edexcel B 2.3 iv, 2.3 v, 2.3 vii, 8.1 i, 8.1 ii, 8.2 iv

  • Say which chromosomes separate in the first division and which in the second, and why that order matters.
  • Describe how a bivalent forms and what crossing over does to the chromatids in it.
  • Work out how many chromosome combinations a gamete could carry, given the haploid number.
  • Track chromosome number and chromatid number through both divisions without losing count.
  • Set out the differences between mitosis and meiosis, division by division.
  • Name all eight stages in order and say what the spindle, the nuclear envelope and the cell surface membrane are doing in each.
  • Name the stage of meiosis that a photomicrograph shows, and justify the naming.
  • Explain how non-disjunction leads to polysomy, as in Down's syndrome, and to monosomy, as in Turner's syndrome.

Monohybrid inheritance and genetic diagrams AQA 3.7.1 · OCR A 6.1.2 · CAIE 16.2 · Edexcel A 2.13, 3.8 · Edexcel B 1.4 ix, 8.2 i, 8.2 ii, 8.2 v

  • Use the terms gene, allele, locus, genotype and phenotype with their standard meanings.
  • Set out a complete monohybrid genetic diagram, from parental phenotypes to the offspring ratio.
  • Predict and interpret ratios for complete dominance, codominance and multiple alleles.
  • Work out blood group possibilities from parental genotypes and the reverse.
  • Handle a sex-linked cross, including why sons and daughters are affected at different rates.
  • Name the gene and the protein behind albinism, sickle cell anaemia, haemophilia A, Huntington's disease and stem length in peas.
  • Explain why an allele is dominant or recessive from what its protein does.
  • Read and draw a pedigree diagram, and deduce from it whether an allele is dominant or recessive and whether its gene is autosomal or on the X chromosome.

Dihybrid inheritance, linkage, epistasis and the chi-squared test AQA 3.7.1 · OCR A 6.1.2 · CAIE 16.2 · Edexcel A 3.8 · Edexcel B 8.2 ii, 8.2 iii, 8.2 iv, 8.2 vi

  • Work out the gametes a dihybrid parent produces and use them to build a 16-cell Punnett square.
  • Predict the 9 : 3 : 3 : 1 and 1 : 1 : 1 : 1 ratios and say what each assumes.
  • Recognise autosomal linkage from a test cross result and calculate a recombination frequency.
  • Identify epistasis from a modified dihybrid ratio and explain it through a pathway.
  • Carry out a chi-squared test in full, from null hypothesis to a conclusion that names the probability.

Population genetics and Hardy-Weinberg equilibrium AQA 3.7.2 · OCR A 6.1.2 · CAIE 17.2 · Edexcel A 4.5, 5.17 · Edexcel B 8.3 iv

  • Define a gene pool and calculate an allele frequency from genotype counts.
  • State the Hardy-Weinberg principle and the five conditions it assumes.
  • Use p + q = 1 and p² + 2pq + q² = 1 to move between allele and genotype frequencies.
  • Calculate carrier frequency from the frequency of a recessive phenotype, and turn frequencies into numbers of individuals.
  • Explain what a departure from Hardy-Weinberg proportions shows about a population.
Gene regulation, genomics and biotechnology

Control of gene expression AQA 3.8.2.2 · OCR A 6.1.1 · CAIE 16.3 · Edexcel A 3.12, 3.14, 6.10, 7.16, 8.6 · Edexcel B 7.2 i, 7.2 ii, 7.2 iii, 7.2 iv, 7.2 v, 7.3 iii, 7.3 iv, 9.2 ii

  • Explain what a transcription factor is and how one alters the rate of transcription of a particular gene.
  • Describe how the lac operon switches on when lactose arrives, naming the regulatory gene, the promoter, the operator and the structural genes.
  • Describe how oestrogen switches a gene on, and explain why a steroid hormone can take that route and a peptide hormone cannot.
  • Explain how DNA methylation and histone acetylation change the accessibility of a gene, and say which way each one pushes.
  • State precisely what epigenetic inheritance is known to involve, and where the evidence in humans runs out.
  • Explain how small interfering RNA stops a protein being made from a gene that has already been transcribed.

Mutation, gene expression and cancer AQA 3.8.1, 3.8.2.1, 3.8.2.3 · OCR A 6.1.1 · CAIE 6.2 · Edexcel A 2.12, 2.14, 4.13 · Edexcel B 1.4 viii, 2.3 vi, 7.3 ii

  • Name the types of gene mutation and give the consequence of each at the level of the polypeptide.
  • Explain why many base substitutions change nothing about the protein, and why a deletion of one base usually changes everything.
  • Distinguish a mutation in a gene from one in a control sequence, and give an example of each.
  • Explain the difference between a proto-oncogene and a tumour suppressor gene, including how many alleles must be affected.
  • Explain how methylation of a promoter can silence a tumour suppressor gene without altering a single base.
  • Describe the therapeutic uses of stem cells and set out the ethical arguments on both sides of the embryonic case.
  • Distinguish a chromosome mutation from a gene mutation, and explain why a balanced translocation carrier is usually healthy but can produce unbalanced gametes.
  • Explain how a faulty CFTR channel makes mucus thick and sticky, and how that mucus impairs the gaseous exchange, digestive and reproductive systems.

Recombinant DNA technology AQA 3.8.4.1 · OCR A 6.1.3 · CAIE 19.1, 19.2, 19.3 · Edexcel A 6.3, 6.4, 8.17, 8.18 · Edexcel B 3.1 iv, 7.1 ii, 7.4 i, 7.4 ii, 7.4 iii, 7.4 iv, 7.4 v, 7.4 vi

  • Describe the three ways of obtaining a gene, and say which one suits which situation and why.
  • Explain what a sticky end is, why the same restriction enzyme must be used on gene and vector, and what ligase does afterwards.
  • Describe transformation and explain why marker genes are needed at all.
  • State the three temperatures of the polymerase chain reaction and explain what each step needs its own temperature for.
  • Calculate the number of copies produced by a given number of PCR cycles, and explain why a real reaction falls short of it.
  • Explain how gel electrophoresis separates DNA fragments, in terms of charge and of the gel itself.
  • Distinguish in vivo from in vitro amplification, and evaluate the ethical, financial and social issues genetic modification raises in a named application.
  • Describe how viral vectors and the gene gun deliver DNA into cells, and say which kinds of cell each suits.
  • Describe how a knockout mouse is produced, and explain how it is used as an animal model to investigate what a gene does.
  • Describe how soya beans are genetically modified, and explain how altering the balance of fatty acids stops soya oil oxidising.
  • Run a gel to separate DNA fragments, and find the length of a fragment from a DNA ladder.

Genome analysis, genetic screening and gene therapy AQA 3.8.3, 3.8.4.2, 3.8.4.3 · OCR A 6.1.3 · CAIE 19.2 · Edexcel A 2.12, 2.14, 2.15, 2.16, 5.18, 6.3, 8.16 · Edexcel B 3.1 v, 7.1 i, 7.1 ii, 7.4 ii

  • Say what a genome project produces, and what still has to be done before a sequence becomes useful.
  • Explain why predicting a proteome from a genome sequence is more direct in many bacteria than in a eukaryote, and where it is not.
  • Explain how a DNA probe works and what a microarray adds to it, distinguishing genotyping from expression profiling.
  • Distinguish genetic screening from genetic counselling, and state what non-directive counselling involves.
  • Describe how a DNA profile is produced from variable number tandem repeats, and interpret a match probability correctly.
  • Compare somatic with germ line gene therapy, and set out why the second is the more contested.
  • Explain how a simpler organism's proteome identifies candidate vaccine antigens, and give the uses of profiling beyond forensics.
  • Explain what personalised medicine is, using HER2 with trastuzumab and TPMT with azathioprine, and weigh its benefits against cost, unequal reference data and the fact that most conditions are polygenic.

Industrial biotechnology and fermentation OCR A 6.2.1 · Edexcel A 4.14, 8.17 · Edexcel B 6.1 i, 6.1 ii, 6.1 iii, 6.1 iv, 6.1 v

  • Give the reasons industry grows microorganisms rather than farming a plant or an animal for the same product.
  • Set out the arguments for and against using microorganisms as human food, with mycoprotein as the named example.
  • Name the parts of a stirred-tank fermenter and explain why each condition inside it has to be controlled.
  • Distinguish batch from continuous fermentation on the closed-culture growth curve, and state which part of the curve each uses.
  • Match a product to the method that suits it, using primary and secondary metabolites.
  • Describe broth, agar and selective media, and say what each is used for.
  • Compare cell counts, dilution plating, mass and turbidity as measures of bacterial growth, distinguishing a total count from a viable count.
  • Calculate an exponential growth rate constant and a mean generation time from two population sizes in the log phase.
  • Follow the growth of bacteria in liquid culture by turbidity, and find the growth rate constant from the log phase.
  • Isolate single species from a mixed culture by streak plating, working aseptically.
  • Test plant extracts for antibacterial activity on a lawn of bacteria, working aseptically, and compare them by the area of the zone of inhibition.

Pharming, recombinant medicines and synthetic biology OCR A 6.1.3 · CAIE 19.2 · Edexcel A 8.17, 8.18 · Edexcel B 7.4 vi

  • Name factor VIII and adenosine deaminase as recombinant medicines, state what each treats, and explain what recombinant production replaced.
  • Explain why some human proteins must be made in eukaryotic cells rather than in bacteria.
  • Describe how a transgenic animal is engineered to secrete a human protein in its milk, and explain the role of the mammary-specific promoter.
  • Set out the welfare and regulatory arguments around pharming on both sides.
  • Describe what synthetic biology adds to genetic engineering, using standard parts, genome synthesis and the artemisinin pathway as the named examples.
  • Argue the biosecurity and ownership questions synthetic biology raises, from both directions.
  • Describe how genetically modified plants are used to produce medicines, with a named example, and weigh the advantages against the risks.
Classification, biodiversity and conservation

Classification, phylogeny and molecular evidence AQA 3.4.5 · OCR A 4.2.2 · CAIE 18.1 · Edexcel A 4.6, 5.18 · Edexcel B 3.1 i, 3.1 ii, 3.1 iii, 3.1 iv, 3.1 v, 3.1 vi, 3.1 vii

  • Write the eight taxonomic ranks in order and name a group at each rank for a named organism.
  • Write a binomial correctly and say what each part of it means.
  • State the biological species concept and give two situations it cannot handle.
  • Distinguish a phenetic from a phylogenetic classification, and explain why convergent evolution defeats the first.
  • Describe the evidence from ribosomal RNA that split the prokaryotes into two domains.
  • Explain how DNA sequences, amino acid sequences and immunological comparisons are used to estimate how closely two species are related.
  • Read a cladogram: say what it asserts, and say what it does not.

The five kingdoms, species concepts and viruses OCR A 4.2.2 · CAIE 18.1 · Edexcel A 4.6 · Edexcel B 2.2 i, 2.2 iii, 3.1 ii, 3.1 iii, 3.1 vii

  • State the characteristic features of each of the five kingdoms and use them to place an unfamiliar organism.
  • Explain why the presence of a nucleus is the first division made, and what separates the three kingdoms that have cell walls.
  • Distinguish the biological, morphological and ecological species concepts, and say which one to use when the others fail.
  • Explain why viruses are placed in no kingdom at all.
  • Classify a virus by whether its genome is DNA or RNA and single-stranded or double-stranded, giving a named example of each.

Measuring biodiversity AQA 3.4.6, 3.4.7, 3.7.4 · OCR A 4.2.1, 6.3.1 · CAIE 18.2 · Edexcel A 4.1, 4.2 · Edexcel B 3.3 i, 3.3 ii, 8.3 iii, 10.1 iv, 10.1 v

  • Distinguish species richness from species diversity, and say what evenness adds.
  • Calculate an index of diversity using the form your board specifies, and state which form you have used.
  • Explain why one Simpson form rises with diversity and the other falls, and interpret a value correctly either way.
  • Describe how genetic diversity within a species is measured, and why observable characteristics are a poor measure of it.
  • Explain how agriculture and monoculture reduce diversity at the habitat, species and genetic levels, and describe measures that offset this.
  • Distinguish random sampling from opportunistic, stratified and systematic sampling, and choose the right collecting equipment for small animals.

Conservation in situ and ex situ AQA 3.7.4 · OCR A 4.2.1 · CAIE 18.3 · Edexcel A 4.1, 4.16, 5.22 · Edexcel B 3.3 ii, 3.3 iii, 10.4 ii, 10.4 iii

  • Define in situ and ex situ conservation and give examples of each.
  • Explain the advantages and the limitations of each approach, and why most programmes use both.
  • Describe how a seed bank collects, dries, stores and tests seed, and explain which species it cannot store.
  • Outline what CITES and the Convention on Biological Diversity each do.
  • Set out the economic, ecological, ethical and aesthetic cases for conservation, and the objection each one meets.
  • Discuss a case where conservation succeeded and one where the outcome is genuinely disputed.
  • Name the assisted reproduction methods used in captive breeding, and explain what a frozen zoo stores and what it cannot do.
Evolution and speciation

Natural selection: variation, selection and allele frequency AQA 3.4.3, 3.4.4 · OCR A 4.2.2, 6.1.2 · CAIE 17.1, 17.2 · Edexcel A 4.3, 4.4, 5.17 · Edexcel B 3.2 i, 3.2 ii, 8.1 i, 8.1 ii, 8.3 i

  • Name the sources of genetic variation and say which of them produces an allele that did not exist before.
  • Distinguish variation that can be selected on from variation that cannot be inherited.
  • Define fitness and selection pressure precisely.
  • Recognise stabilising, directional and disruptive selection from a distribution and from a description.
  • Explain why selection acts on phenotype while evolution is measured as a change in allele frequency.
  • Write about selection without using language that implies organisms change on purpose.

Evidence for evolution, resistance and genetic drift AQA 3.4.4, 3.7.3 · OCR A 4.2.2, 6.1.2 · CAIE 17.2, 17.3 · Edexcel A 4.4, 5.17, 5.18, 6.13, 6.14, 6.15 · Edexcel B 3.2 iv, 6.3 i, 6.4 i, 6.4 ii, 8.3 ii, 8.3 iii

  • Explain the origin of antibiotic resistance in a bacterial population without implying the antibiotic caused it.
  • Distinguish vertical from horizontal transfer of a resistance gene, and say why the second is faster.
  • Give the biological reason a prescribed course of antibiotics is finished.
  • Describe pesticide resistance and explain why a refuge of untreated crop slows it.
  • Set out the fossil, anatomical, biochemical and biogeographical evidence for common ancestry.
  • Distinguish genetic drift and the founder effect from natural selection, and say when each matters most.
  • Outline what Darwin and Wallace each contributed to the formulation of the theory of natural selection, and what neither of them could explain.
  • Distinguish bactericidal from bacteriostatic antibiotics, using the action of penicillin and tetracycline.
  • Explain the contributory causes of hospital-acquired infections and the codes of practice on prescribing and infection control that follow from them.
  • Compare the effect of different antibiotics on a lawn of bacteria by the area of the zone of inhibition, working aseptically, and say what the comparison cannot show.

Speciation and reproductive isolation AQA 3.4.5, 3.7.3 · OCR A 6.1.2 · CAIE 17.3, 18.1 · Edexcel A 4.5, 5.19 · Edexcel B 3.1 ii, 3.1 iii, 3.2 iii, 8.3 i

  • State the biological species concept and identify situations in which it cannot be applied.
  • Explain what reproductive isolation means and why it defines the boundary between species.
  • Describe allopatric speciation as a sequence, from one gene pool to two.
  • Describe sympatric speciation, and explain why polyploidy is the most direct route to it.
  • Classify isolating mechanisms as prezygotic or postzygotic and give an example of each.
  • Discuss the timescale of speciation and why the boundary between two species is often not sharp.

Continuous and discontinuous variation OCR A 4.2.2 · CAIE 17.1 · Edexcel A 3.14, 3.15, 8.19

  • Distinguish continuous from discontinuous variation on the number of genes, the effect of the environment, the distribution and the graph.
  • Give a named example of each kind, and say why blood group and height behave differently.
  • Explain how several genes acting together on one characteristic produce a smooth distribution rather than separate classes.
  • Describe how environmental factors modify a phenotype, and say why they are not inherited.
  • Use the terms intraspecific and interspecific variation correctly.

Artificial selection and selective breeding OCR A 6.1.2 · CAIE 17.2

  • State the principle of artificial selection and set it against natural selection point by point.
  • Describe how disease resistance is bred into a crop such as wheat or rice.
  • Explain how inbred lines of maize are produced and why the cross between two of them outyields either parent.
  • Describe how milk yield is improved in dairy cattle, using progeny testing and artificial insemination.
  • Explain inbreeding depression and say why wild types and their alleles are worth keeping.
  • Discuss the ethical objections to breeding an animal to an extreme.
Ecology, populations and environmental change

Populations and their limits AQA 3.7.4 · OCR A 6.3.2 · CAIE 18.2 · Edexcel A 4.3, 4.14, 5.1, 5.2, 5.3 · Edexcel B 3.2 ii, 6.1 v, 10.1 i, 10.1 ii, 10.3 ii

  • Use population, community, habitat and ecosystem as four different words with four different meanings.
  • Describe each phase of a sigmoid growth curve in terms of birth rate and death rate.
  • Sort a limiting factor into density-dependent or density-independent, and justify the choice.
  • Distinguish intraspecific from interspecific competition and predict what each does to a population.
  • State the competitive exclusion principle and use the ecological niche to explain it.
  • Explain why the predator peak lags the prey peak, and what that lag can and cannot show about predator control.
  • Estimate a population by mark, release and recapture, and say which assumption a given problem breaks.

Nutrient cycles: nitrogen, phosphorus and eutrophication AQA 3.5.4 · OCR A 6.3.1 · CAIE not examined as a topic · Edexcel A 4.12, 6.2 · Edexcel B 10.2 iii, 10.4 i

  • Explain why plants cannot use nitrogen gas and must take up nitrate, or some ammonium, instead.
  • Name the four bacterial processes of the nitrogen cycle and state what each converts into what.
  • Say which of the four need oxygen and which needs its absence, and use that to explain a farming practice.
  • Describe the phosphorus cycle and explain why it has no gaseous stage.
  • Set out eutrophication as a sequence of consequences and identify the step that actually removes the oxygen.
  • Calculate the nitrogen applied to a field from the mass of fertiliser, and estimate what leaches from it.

Succession and environmental change AQA 3.7.4 · OCR A 6.3.1, 6.3.2 · CAIE 18.3 · Edexcel A 5.2, 5.4, 6.1 · Edexcel B 10.1 iv, 10.1 v, 10.3 i, 10.3 ii

  • Describe primary succession from a pioneer species to a climax community, naming what changes at each stage.
  • Explain how a pioneer species alters the abiotic environment and why that leads to its own replacement.
  • Distinguish primary from secondary succession and explain why secondary succession is faster.
  • Explain what a plagioclimax is and why conservation management often maintains one.
  • Describe how succession is investigated in the field, including the use of a chronosequence.
  • State what a long-term ecological dataset can establish and what it cannot.
  • Describe frame, gridded and point quadrats and the ACFOR scale, and choose between them for a given habitat and organism.
  • Explain how body temperature, rigor mortis, the extent of decomposition, forensic entomology and the stage of succession are used to estimate the time of death of a mammal.
  • Plan a field study of the effect of an abiotic factor on the distribution of a species, choosing random or systematic sampling, the size and number of quadrats, and how each abiotic factor is measured.
  • Analyse field data with Spearman's rank, a t-test or chi-squared as the question requires, and compare the population estimates that different sampling methods give.

The carbon cycle and climate change OCR A 4.2.1, 6.3.1 · Edexcel A 4.1, 5.12, 5.13, 5.14, 5.15, 5.16, 5.21, 5.22, 6.1, 6.2 · Edexcel B 10.4 i, 10.4 iv

  • Assemble the carbon cycle from the processes that move carbon between the air, living organisms, the soil and the sea.
  • Explain how fossil fuels were formed, and why burning them transfers geological carbon to the atmosphere far faster than natural processes do.
  • Describe the evidence that atmospheric carbon dioxide is rising, and explain the shape of the record.
  • Explain how deforestation, consumption per person and land-use choices contribute to the rise, alongside population size.
  • Describe the effects of a changing climate on the distribution and abundance of species, and hence on biodiversity.
  • Describe the evidence for climate change from temperature records, carbon dioxide records, pollen in peat bogs and dendrochronology, and separate correlation from cause in it.
  • Explain how climate models are built and tested, and why their projections have limitations and are given as ranges.
  • Describe how changing rainfall patterns and seasonal cycles affect the distribution, development and life cycles of plants and animals.
  • Describe the roles of scientific journals, peer review and conferences in validating evidence about climate change.
  • Investigate the effect of temperature on the development of an organism, and calculate a development rate and Q10 from the results.

Managing ecosystems sustainably OCR A 6.3.2 · Edexcel A 5.21, 5.22 · Edexcel B 10.4 i, 10.4 iii

  • Define sustainable yield and explain, using the growth curve, why it is greatest at about half the carrying capacity.
  • Describe coppicing, pollarding, rotational management and selective felling, and say what each is for.
  • Explain how quotas, mesh sizes, closed seasons and no-take zones each protect a fish stock.
  • Evaluate aquaculture as an answer to overfishing.
  • Discuss the conflict between managing an ecosystem for conservation and the needs of the people who use it.
  • Explain how knowledge of the carbon cycle is applied to methods of reducing atmospheric carbon dioxide.
  • Evaluate reforestation and biofuels as ways of managing the conflict between human needs and conservation.

Moving your ratings

Ratings live in this browser, on this device, unless you sign in to the optional account, which carries them between your devices. Without one, clearing your browser data clears them; use “Copy my progress” to carry them to another device by hand, and “Paste saved progress” at the other end.