OCR A-Level Biology
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Module 1: Development of practical skills in biology
1.1 Practical skills assessed in a written examination
1.1.1(a)-(c) - Experimental design and controlled variablesTurn a biological question into a method that can answer it: choose a measurable response, suitable apparatus, a treatment range and controls, then judge whether the results could distinguish the proposed effect.
1.1.2(a)-(c) - Practical techniques, units and recording dataGood biology practical work is not just "doing the experiment". It means using apparatus correctly, recording each measurement with a suitable unit, and presenting observations so another scientist can understand what happened. In this lesson, you will learn the implementation habits OCR can test...
1.1.3(a)-(d)(ii) - Analysis, calculations and graph skillsIn this lesson you learn how experimental results become biological conclusions. You will process qualitative and quantitative results, choose suitable mathematical handling, use significant figures sensibly, and construct or interpret graphs with correct axes, scales, units, gradients and interc...
1.1.4(a)-(e) - Evaluation, uncertainty and method improvementThis lesson is about judging the quality of practical evidence. You will learn how to move from results to a supported conclusion, how to spot anomalies and limitations, how precision, accuracy and uncertainty affect confidence, and how to suggest method improvements that are specific enough to e...
1.2 Practical skills assessed in the practical endorsement
1.2.1(a)-(c) - Investigative approaches, risk and instructionsThis lesson is about practical competence: how to move from a biological question to a safe, workable method, and how to carry it out without losing control of the investigation. You will learn how to apply investigative approaches, solve practical problems, use equipment and materials safely, id...
1.2.1(d)-(g) - Recording, presenting and processing dataGood practical work is not only about doing the experiment. It is also about leaving a record that another scientist can understand, check and use as evidence. In this lesson you will learn how to make and record observations and measurements, keep appropriate practical records, present data scie...
1.2.1(h)-(j) - Research, citation and choosing equipmentIn practical biology, good planning begins before anyone picks up a pipette. You need to find information from suitable sources, record where it came from, and use it to choose equipment and techniques that fit the biological question. This lesson teaches those Module 1 skills as practical decisi...
1.2.2(a)-(c) - Measurement apparatus and serial dilutionsPractical biology only becomes evidence when measurements are made with apparatus that suits the question. In this lesson you will learn how to choose apparatus for quantitative measurements, how to make those measurements trustworthy, and how instruments such as colorimeters and potometers turn...
1.2.2(d)-(e) - Light microscopy and biological drawingsThis lesson teaches the practical skill behind many later OCR Biology observations: using a light microscope at low and high power, measuring with a graticule, and turning observations into a clear scientific drawing. The aim is not to memorise one specimen. It is to make the microscope view reli...
1.2.2(f)-(g), 1.2.2(i) - Reagent tests, separation and asepsisIn this lesson you are learning three laboratory technique families that OCR expects you to use safely and explain precisely: qualitative tests for biological molecules, separation methods, and aseptic microbiology. The biology is not just the name of a test; it is the link between a method step,...
1.2.2(h), 1.2.2(j)-(l) - Responses, dissection, fieldwork and ICTIn this lesson you are learning how to choose and carry out four broad practical technique families: measuring responses in organisms, dissecting organs safely, sampling in the field, and using ICT to collect or process data. The focus is not detailed physiology, ecology or anatomy; it is the pra...
Module 2: Foundations in biology
2.1.1 Cell structure
2.1.1(a) - Microscopy to observe eukaryotic cellsThis lesson is about using microscopy as evidence: choosing a microscope because of the kind of cell structure you need to investigate, then interpreting what its image can and cannot show. The focus is eukaryotic organisms, so examples may come from animal, plant, fungal or protist cells. You ar...
2.1.1(b)-(d) - Slide preparation, staining and drawingsThis lesson teaches how a microscope observation becomes reliable evidence: prepare a thin slide, use stains sensibly, measure with calibrated scale, then communicate only what is visible. The focus is practical microscopy, not electron microscopy or organelle ultrastructure.
2.1.1(e)-(f) - Magnification, resolution and microscope choiceThis lesson separates two ideas students often merge: magnification makes an image bigger, while resolution makes close structures distinguishable. You will also practise the magnification formula and choose between light, transmission electron and scanning electron microscopes from evidence.
2.1.1(g)-(h) - Eukaryotic cell ultrastructure and micrographsThis lesson builds a usable map of eukaryotic cell components and then shows how to interpret electron micrographs without guessing. The key habit is structure-function reasoning: identify what is visible, then connect it to a precise function.
2.1.1(i)-(j) - Protein secretion organelles and the cytoskeletonThis lesson is about how eukaryotic cells coordinate internal structures to get useful proteins out of the cell and to move materials within the cell. You need the organelle sequence for protein secretion and the three key roles of the cytoskeleton: mechanical strength, intracellular transport an...
2.1.1(k) - Prokaryotic and eukaryotic cell comparisonThis lesson is about comparing two basic kinds of cellular organisation. You are not learning every organelle again; you are learning the precise structural features that let a biologist distinguish a prokaryotic cell from a eukaryotic cell. The specification point also links to microscopy, so th...
2.1.2 Biological molecules
2.1.2(a) - Water, hydrogen bonding and biological rolesIn this lesson you are learning why water is not just a background liquid in Biology. OCR wants you to explain how hydrogen bonding occurs between water molecules and then link water's properties to roles in living organisms. The route is molecule first, then property, then biological role, with...
2.1.2(b)-(c) - Polymers, condensation, hydrolysis and elementsLiving cells contain large biological molecules, but those molecules are built from a small set of recurring chemical ideas. In this lesson you learn how smaller units can join to form larger molecules, why condensation and hydrolysis reactions matter, and which chemical elements OCR expects you...
2.1.2(d)-(e) - Mono- and disaccharides and glycosidic bondsThis lesson teaches carbohydrate structure at the level needed for glucose, ribose, named disaccharides and glycosidic bonds. The aim is to connect molecular shape to bond formation without drifting into later starch, cellulose or biochemical test lessons.
2.1.2(f)-(g) - Starch, glycogen and cellulose structure-functionThis lesson is about how a small difference in glucose bonding changes the job of a carbohydrate. Starch, glycogen and cellulose are all polysaccharides made from glucose, but they are not interchangeable: their linkage pattern and branching decide whether they are useful for storage or support....
2.1.2(h)-(i) - Triglycerides, phospholipids and ester bondsIn this lesson you are learning how triglycerides and phospholipids are built from glycerol and fatty acids. The key specification idea is structural: where the fatty acid chains attach, what saturated and unsaturated means, and how ester bonds form and break in triglycerides. Keep the boundary t...
2.1.2(j) - Lipid properties, cholesterol and biological functionsIn this lesson you are learning how three lipid types do their jobs because of their properties: triglycerides, phospholipids and cholesterol. The important move is not just naming a lipid, but linking a property such as hydrophobicity, amphipathic structure or high energy content to a function i...
2.1.2(k)-(m) - Amino acids, peptide bonds and protein structureThis lesson builds proteins from the bottom up: amino acid template, peptide bond, polypeptide, then four levels of protein structure. The emphasis is using precise bond language, because peptide bonds are not the same as the interactions that stabilise folding.
2.1.2(n)-(o) - Globular and fibrous proteinsThis lesson is about how protein shape fits biological function. You already met amino acids, peptide bonds and levels of protein structure; here the focus narrows to two broad protein types that OCR names directly: globular proteins and fibrous proteins. You will use haemoglobin, a named enzyme...
2.1.2(p) - Inorganic ions in biological processesInorganic ions are small charged particles, but they are involved in many of the biological processes you meet across the course. This lesson keeps the boundary tight: you need to recognise the required ion symbols, know whether each ion is positive or negative, and connect each one with a sensib...
2.1.2(q) - Chemical tests for biological moleculesThis lesson teaches how to carry out and interpret the four qualitative tests named in OCR Biology A for biological molecules. You will learn what each reagent shows, how to keep the method safe and valid, and how to turn a colour change into a careful biological conclusion without overclaiming.
2.1.2(r) - Colorimetry for concentration determinationIn this lesson you learn how a colorimeter can turn a colour change into a numerical estimate of concentration. The boundary is deliberately tight: the skill is using quantitative readings, known standards and a calibration curve to find the concentration of a chemical substance in solution. This...
2.1.2(s)(i)-(ii) - Paper and thin layer chromatographyIn this lesson you are learning how paper chromatography and thin layer chromatography separate biological compounds, how to run a valid practical investigation, and how to calculate and interpret Rf values. OCR cares about the method because a chromatogram is evidence: it can show whether a biol...
2.1.3 Nucleotides and nucleic acids
2.1.3(a)-(b) - Nucleotides and polynucleotidesNucleic acids such as DNA and RNA are built from smaller monomers called nucleotides. In this lesson you will learn what a nucleotide contains, how DNA and RNA nucleotides differ, and how nucleotides join into polynucleotides through phosphodiester bonds. This is the molecular foundation for late...
2.1.3(c) - ADP and ATP as phosphorylated nucleotidesIn this lesson you are learning the structure of ADP and ATP as OCR expects it: both are phosphorylated nucleotides made from adenine, ribose and inorganic phosphate groups. The focus is deliberately narrow. Later lessons use ATP in respiration, photosynthesis, active transport and muscle contrac...
2.1.3(d)(i)-(ii) - DNA structure and DNA precipitationDNA stores genetic information because its structure is stable, specific and copyable. In this lesson you learn how two antiparallel DNA polynucleotides are held together by complementary base pairing, how this produces a double helix, and how a simple precipitation practical can release visible...
2.1.3(e) - Semi-conservative DNA replicationIn this lesson you learn how DNA can be copied before cell division while keeping the genetic information almost exactly the same. The key idea is semi-conservative replication: each new DNA molecule keeps one strand from the original molecule and gains one newly made complementary strand. You wi...
2.1.3(f) - The nature of the genetic codeIn this lesson you learn how the base sequence in a protein-coding gene determines the sequence of amino acids in a polypeptide. The focus is the nature of the genetic code: it is triplet, non-overlapping, degenerate and universal. The lesson stays at the level of the code itself, with only a lig...
2.1.3(g) - Transcription and translationIn this lesson you learn how the information in a gene is used to make a polypeptide. OCR expects the mechanism, not just the slogan "DNA makes protein": transcription makes an mRNA copy of the gene, then translation uses that mRNA at a ribosome to join amino acids in the correct sequence. The na...
2.1.4 Enzymes
2.1.4(a)-(b) - Intracellular and extracellular enzymesEnzymes make metabolism fast enough to sustain life. Catalase and amylase show how the location of a catalysed reaction connects cell protection, digestion and the functioning of the whole organism.
2.1.4(c) - Mechanism of enzyme actionEnzymes speed up metabolic reactions because their three-dimensional structure lets specific substrates bind and react more easily. In this lesson you will learn how the active site, lock and key model, induced-fit model, enzyme-substrate complex, enzyme-product complex and activation energy fit...
2.1.4(d)(i)-(ii) - Enzyme activity factors and practicalsTemperature, pH and reactant concentrations affect the rate of enzyme-catalysed reactions. Learn how to explain their effects, calculate Q₁₀, and design reliable enzyme experiments using measured rates.
2.1.4(e) - Coenzymes and cofactorsSome enzyme-controlled reactions need a non-protein helper before the enzyme can work at its normal rate. In this lesson you will learn the course distinction between cofactors and coenzymes, why chloride ions matter for amylase, and how vitamins can provide sources of coenzymes. The practical th...
2.1.4(f) - Enzyme inhibitors and end-product inhibitionEnzyme inhibitors reduce the rate of enzyme-controlled reactions, but they do this in different ways. In this lesson you will learn how to distinguish competitive and non-competitive inhibition, how reversible and non-reversible inhibition affect enzyme activity, and how end-product inhibition co...
2.1.5 Biological membranes
2.1.5(a)-(b) - Membrane roles and the fluid mosaic modelMembranes separate aqueous compartments while allowing selective exchange, organised reactions and signalling. The fluid mosaic model links these roles to phospholipids, cholesterol, proteins and carbohydrate-bearing components.
2.1.5(c)(i)-(ii) - Factors affecting membrane permeabilityMembranes are not fixed plastic bags around cells. Their phospholipids and proteins move, and their structure can be disturbed by conditions such as temperature and solvents. In this lesson you will learn how those conditions affect permeability, and how beetroot practicals use pigment leakage an...
2.1.5(d)(i)-(ii) - Transport across membranes and model cellsCells survive because their membranes are selective boundaries, not sealed walls. In this lesson you will learn how molecules move across membranes by diffusion, facilitated diffusion, active transport, endocytosis and exocytosis. You will then use model-cell investigations to connect those ideas...
2.1.5(e)(i)-(ii) - Osmosis, water potential and practicalsOsmosis is how water moves across cell membranes when there is a difference in water potential. In this lesson you will learn how that gradient affects animal and plant cells, then use the same idea to design and interpret PAG8-style investigations with potato tissue or model cells. The important...
2.1.6 Cell division, cell diversity and cellular organisation
2.1.6(a)-(b) - Cell cycle phases and checkpoint regulationCells do not divide by simply stretching and splitting. They move through an ordered cell cycle in which DNA is copied, the copied genetic information is separated, and the cell is divided into two genetically identical daughter cells. This lesson focuses on the phase sequence and on checkpoints:...
2.1.6(c)-(d) - Mitosis stages and plant tissue microscopyMitosis is the part of the cell cycle where the copied genetic material is separated into two nuclei. In this lesson you will learn the visible stages of mitosis, the exact structures whose changes you must track, and how stained plant tissue can be used as evidence for those stages. The practica...
2.1.6(e)-(f) - Significance of mitosis and meiosis in life cyclesLiving organisms have two linked problems to solve. They need to make more cells for growth, repair and some forms of reproduction, while keeping the genetic instructions stable. In sexual life cycles they also need to make haploid cells and create genetic variation, so meiosis has a different si...
2.1.6(g) - Stages of meiosis and homologous chromosomesMeiosis is a two-division sequence that turns one diploid cell into haploid cells. In this lesson, the main job is not to memorise a blur of chromosome pictures, but to know what separates at each division: homologous chromosomes in meiosis 1, then sister chromatids in meiosis 2. That distinction...
2.1.6(h) - Specialised cells in multicellular organismsMulticellular organisms are not built from one general-purpose cell repeated millions of times. They work because cells become specialised: their visible shape, internal contents and surface structures suit a particular job. In this lesson you will learn the named animal and plant cell examples r...
2.1.6(i) - Cells, tissues, organs and organ systemsMulticellular organisms are not just large bags of separate cells. Their cells are organised into levels, and each level adds coordination: cells work together as tissues, tissues combine as organs, and organs cooperate in organ systems. In this lesson you will learn the hierarchy and the tissue...
2.1.6(j)-(l) - Stem cells and differentiated cell outcomesMulticellular organisms need some cells to become highly specialised, but they also need a way to keep making new specialised cells. This lesson follows one central idea: a stem cell can renew an undifferentiated source and can also produce differentiated outcomes. The OCR examples are deliberate...
2.1.6(m) - Potential uses of stem cellsStem cells matter because they connect a simple cell property to a big biological question: can lost or damaged specialised cells be replaced? In this lesson, you will learn how stem cells could be used in medicine and research, while keeping the word potential honest. The strongest answers do no...
Module 3: Exchange and transport
3.1.1 Exchange surfaces
3.1.1(a)-(b) - Need and features of specialised exchange surfacesEvery living cell must exchange substances with its surroundings: useful substances such as oxygen and nutrients move in, while waste substances such as carbon dioxide move out. This lesson explains why a simple body surface is enough for some organisms but not for others, and how specialised exc...
3.1.1(c)-(d) - Mammalian gaseous exchange system and ventilationMammals need a system that gets fresh air to a thin exchange surface and then keeps replacing that air. In this lesson, you will learn the route air takes through the mammalian gaseous exchange system, how the main tissues in the airways support their functions, and how muscle action changes thor...
3.1.1(e) - Spirometry, vital capacity and oxygen uptake dataSpirometry turns breathing into a trace that can be measured. In this lesson you will learn how tidal volume, vital capacity, breathing rate and oxygen uptake are connected, and how to interpret primary or secondary data from a spirometer or data logger. The important skill is not just naming the...
3.1.1(f) - Bony fish gills and countercurrent exchangeBony fish live in water, where oxygen is dissolved at a much lower concentration than in air. This lesson explains how a bony fish keeps water moving over its gills, how the gill surface is organised for diffusion, and why countercurrent flow lets more oxygen enter the blood than a simpler same-d...
3.1.1(f) - Insect ventilation and tracheal gas exchangeInsects exchange gases through a tracheal system: a branching network of air-filled tubes that opens to the outside through spiracles. This lets oxygen reach respiring tissues directly, without needing blood to carry oxygen around the body. In this lesson you will learn the route gases take, how...
3.1.1(g)-(h) - Exchange surface dissection, drawing and histologyThis lesson is about using practical observation as biological evidence. You already know that exchange surfaces need a large surface area, a short diffusion pathway, and a maintained concentration gradient; here you learn how dissection, microscope slides and scientific drawings let you examine...
3.1.2 Transport in animals
3.1.2(a)-(b) - Need for transport systems and circulatory designsLarge multicellular animals have a problem that single cells do not: many of their cells are too far from the outside environment for diffusion alone to supply materials and remove wastes fast enough. This lesson builds the need for transport systems from size, metabolic rate and surface area to...
3.1.2(c)-(d) - Blood vessels, tissue fluid and lymphBlood is useful only if it can be moved close enough to cells for exchange to happen. In this lesson you will learn how the structure of arteries, arterioles, capillaries, venules and veins matches their function, then use pressure differences to explain how tissue fluid and lymph form. The key e...
3.1.2(e)(i)-(ii) - Mammalian heart structure and dissectionThe mammalian heart is two muscular pumps joined in one organ: the right side sends blood to the lungs, and the left side sends blood to the rest of the body. In this lesson you will learn the external and internal structures that make that separation possible, then use the same structures to pla...
3.1.2(f) - Cardiac cycle and cardiac outputEvery heartbeat is a repeated mechanical sequence: chambers relax, fill, contract, and push blood into the arteries. In this lesson the key idea is that blood moves because of pressure differences, while valves make that movement one-way. You will also use the OCR formula for cardiac output, whic...
3.1.2(g)-(h) - Heart conduction and ECG interpretationThe heart does not wait for a nerve impulse before every beat. Cardiac muscle is myogenic, so it can initiate its own electrical excitation, then coordinate that excitation so the atria and ventricles contract in the right order. In this lesson you will connect the named conduction tissues to the...
3.1.2(i) - Haemoglobin transport of oxygen and carbon dioxideCells need a continuous supply of oxygen for aerobic respiration, and they must remove the carbon dioxide produced by that respiration. Haemoglobin makes both jobs efficient: it carries oxygen reversibly and also helps carbon dioxide travel safely in the blood. This lesson follows the exact route...
3.1.2(j) - Oxygen dissociation curves and the Bohr effectHaemoglobin is useful because it does not hold oxygen with the same strength in every situation. This lesson teaches how to read oxygen dissociation curves for adult and fetal human haemoglobin, and how carbon dioxide changes the curve in the Bohr effect. The goal is to turn a curve into a biolog...
3.1.3 Transport in plants
3.1.3(a)-(b)(iii) - Plant transport systems and vascular tissueLarge multicellular plants cannot rely on diffusion alone to connect roots, stems and leaves. In this lesson you will use size, metabolic demand and surface-area-to-volume ratio to explain why transport systems are needed, then link xylem and phloem structure to function in herbaceous dicotyledon...
3.1.3(c)(i)-(ii) - Transpiration, its factors and potometersTranspiration is water loss from a plant, but the important A-level idea is why it happens: leaves need open gas-exchange surfaces for photosynthesis, and open stomata also let water vapour escape. In this lesson you will connect that process to environmental factors, then use a potometer to esti...
3.1.3(d) - Water movement through plantsWater does not drift randomly through a plant. It follows a connected route from soil, into root cells, across root tissue, up the xylem, across the leaf and finally into the air surrounding the leaf. In this lesson, you will learn the two named tissue pathways OCR requires, and the mechanism tha...
3.1.3(e) - Xerophyte and hydrophyte adaptationsPlants cannot move away from dry soil, wind, flooding or a water surface, so their structure has to match the water availability of the environment. This lesson focuses on the named OCR examples: cacti and marram grass as xerophytes, and water lilies as hydrophytes. The important skill is not jus...
3.1.3(f) - Translocation in phloemPlants make sugars in some places and use or store them in others. This lesson explains how assimilates, especially sucrose, are transported through phloem from sources to sinks. The key idea is that translocation is not just diffusion along a tube: loading at the source and removal at the sink c...
Module 4: Biodiversity, evolution and disease
4.1.1 Communicable diseases, disease prevention and the immune system
4.1.1(a)-(b) - Pathogen types and transmissionCommunicable disease begins with two linked ideas: a pathogen must be able to cause disease, and it must be able to pass from one host to another. Different pathogen groups exploit different routes into hosts. Linking each route to the conditions that favour it explains why infection spreads in s...
4.1.1(c)-(d) - Plant defences and primary animal defencesPathogens only cause disease if they enter living tissue, survive there, and spread far enough to damage the organism. In this lesson you will learn how plants limit pathogen spread and how animals use primary non-specific defences before a pathogen-specific immune response is needed. The main sk...
4.1.1(e)(i)-(ii) - Phagocytes, blood smears and phagocytosisWhen a pathogen gets past the body's primary defences, some white blood cells respond by engulfing and digesting it. In this lesson you will learn the required structure and mode of action of phagocytes, then connect that biology to PAG1 blood-smear microscopy and biological drawing. The focus is...
4.1.1(f)-(g) - Lymphocytes, clonal selection and immune memoryThe specific immune response is the part of defence that recognises a particular antigen and builds a response against it. That specificity depends on B and T lymphocytes, which carry receptors that only fit certain antigens. In this lesson you will learn how the matching lymphocytes are selected...
4.1.1(h)-(i) - Antibodies, opsonins, agglutinins and antitoxinsAntibodies are proteins that make the specific immune response precise. In this lesson you will learn the general structure of an antibody molecule, how that structure lets antibodies bind specific antigens, and how three antibody actions - opsonisation, agglutination and anti-toxin action - help...
4.1.1(j)-(k) - Immunity categories and autoimmune diseaseThis lesson is about classifying immunity precisely. You will separate active from passive immunity, natural from artificial immunity, and then use that same idea of immune recognition to understand what an autoimmune disease is. The named example here is arthritis, treated carefully as autoimmun...
4.1.1(l) - Vaccination programmes and epidemicsVaccination is not only about protecting one person from one pathogen. In this lesson you will connect the immune memory made after vaccination to the population-level decisions that reduce the chance of an epidemic. You will also practise the kind of data reasoning used when vaccination programm...
4.1.1(m)-(n) - Medicines, antibiotics and resistanceMedicines are not just manufactured ideas from a laboratory bench: many began as useful chemicals made by living organisms. In this lesson, you will connect biodiversity, personalised medicine and antibiotic use into one careful argument: medicines can transform health, but their use creates biol...
4.2.1 Biodiversity
4.2.1(a) - Levels of biodiversityBiodiversity is not just a long species list. In this lesson you will learn how the same biological area can be described at three different levels: habitat biodiversity, species biodiversity and genetic biodiversity. That distinction matters because a question about habitats needs a different an...
4.2.1(b)(i)-(ii) - Sampling biodiversity in habitatsSampling lets biologists make a reliable estimate of the organisms in a habitat without trying to count every individual. In this lesson, you will learn how random and non-random field sampling are used to measure biodiversity, how to choose equipment for different organisms, and how to make the...
4.2.1(c)-(d) - Species richness, evenness and Simpson's IndexBiodiversity can be measured more carefully than by saying that a habitat "has lots of organisms". In this lesson you will learn how species richness and species evenness are measured from habitat data, how Simpson's Index of Diversity is calculated from a provided formula, and how to interpret h...
4.2.1(e) - Genetic biodiversity calculationsGenetic biodiversity is variation within a species, not the number of species in a habitat. In this lesson you will learn how genetic biodiversity can be assessed in isolated populations by counting polymorphic gene loci and turning that count into a proportion or percentage. This matters in cont...
4.2.1(f)-(g) - Threats to biodiversity and reasons to maintain itBiodiversity can be lowered by changes in human activity and the physical environment. Human population growth, monoculture and climate change alter habitats and populations through different mechanisms. Ecological, economic and aesthetic reasons explain why conserving this variety matters.
4.2.1(h)-(i) - Conservation methods and conservation agreementsConservation is the active management of species, habitats and genetic resources so that biodiversity is maintained. In this lesson, you will learn how conservation can happen inside a natural habitat, outside it, and through agreements that change human behaviour. The aim is not to memorise a ca...
4.2.2 Classification and evolution
4.2.2(a)-(b) - Taxonomic hierarchy and binomial namingClassification gives biologists a shared way to organise the huge variety of living organisms. In this lesson, you will learn the taxonomic hierarchy from domain to species, how a binomial scientific name is built, and why this naming system is useful when common names are unclear or different in...
4.2.2(c)(i)-(ii) - Kingdom and domain classification systemsClassification systems are models for organising the diversity of life. In this lesson, you will learn the features used in the five-kingdom system, why newer molecular evidence changed high-level classification, and how the three-domain system compares with the kingdom system. The key idea is no...
4.2.2(d) - Classification and phylogenyClassification is the organised grouping and naming of organisms. Phylogeny is about evolutionary history: which organisms share ancestors, and how recently those ancestors were shared. In this lesson, you will connect the two ideas so that a classification table or a simple evolutionary tree bec...
4.2.2(e) - Evidence for evolution by natural selectionEvolution by natural selection is a scientific explanation supported by historical, molecular and experimental evidence. In this lesson, you will learn how Darwin and Wallace contributed to the theory, then how fossils, genomic DNA and molecular comparisons support it. The key skill is not just n...
4.2.2(f) - Types and causes of variationVariation means differences in characteristics. Those differences matter because biologists use them to describe biodiversity, compare organisms, collect data and explain how phenotypes arise. In this lesson you will separate variation within and between species, compare continuous and discontinu...
4.2.2(g) - Adaptations and similar anatomical featuresAdaptations explain why organisms seem so well suited to the places they live. In this lesson, you will learn how to recognise anatomical, physiological and behavioural adaptations, and how to explain why organisms from different taxonomic groups can show similar anatomical features without being...
4.2.2(h) - Natural selection changing population characteristicsNatural selection is one mechanism that can make a population look different over time. In this lesson you will learn the causal sequence: genetic variation, selection pressure, reproductive success or failure, and an increased proportion of individuals with advantageous characteristics. You will...
4.2.2(i) - Evolutionary implications for human populationsEvolution is not only a long-term idea about fossils or distant ancestors. It can happen quickly in species with short generation times, and that can affect human health, food production and disease control. In this lesson you will learn how resistance evolves in insects exposed to pesticides and...
Module 5: Communication, homeostasis and energy
5.1.1 Communication and homeostasis
5.1.1(a)-(b) - Communication systems and cell signallingMulticellular organisms only work because their cells do not behave as isolated units. In this lesson you will learn why animals and plants need communication systems, and how cell signalling lets cells coordinate activity over short and long distances. The focus is deliberately broad: detailed f...
5.1.1(c) - Principles of homeostasis and feedbackHomeostasis is the reason cells can keep functioning even when the outside world changes. In this lesson you will learn the general control-system language behind later examples such as temperature control, blood glucose control and water-potential control. The key skill is to describe the loop a...
5.1.1(d) - Temperature control in ectotherms and endothermsTemperature control matters because enzyme-controlled reactions are sensitive to temperature. If body temperature moves too far from a suitable range, metabolic reactions become too slow or proteins may lose their functional shape. In this lesson you will compare two strategies: endotherms use in...
5.1.2 Excretion as an example of homeostatic control
5.1.2(a) - Excretion and homeostasisExcretion is one of the ways a mammal keeps its internal environment suitable for life. In this lesson, you will define excretion precisely, distinguish it from similar-looking processes, and explain why removing carbon dioxide and nitrogenous waste matters for metabolism and homeostasis.
5.1.2(b)(i)-(ii) - Liver structure, histology and functionsThe liver is part of excretion because it removes or changes harmful metabolic products before they disrupt homeostasis. In this lesson you will link visible liver structure to microscopic histology, then use that structure to explain glycogen storage, detoxification and urea formation. You will...
5.1.2(c)(i)-(iii) - Kidney structure, nephrons and practicalsThe kidney is a homeostatic organ because it removes nitrogenous waste from the blood while conserving useful substances and helping the body produce urine with the right composition. In this lesson, you will connect the gross structure seen in a kidney dissection to the microscopic structure of...
5.1.2(d) - Control of blood water potential by ADHYour cells work properly only if the water potential of the blood is kept close to a set point. This lesson follows one homeostatic control loop: how osmoreceptors in the hypothalamus detect a change, how the posterior pituitary releases ADH, and how ADH changes the walls of the collecting ducts...
5.1.2(e) - Kidney failure, dialysis and transplantsKidneys help keep the internal environment stable by filtering blood, removing nitrogenous waste, regulating water content and controlling the concentrations of mineral ions. In this lesson you will learn what happens when kidney function fails, why glomerular filtration rate and electrolyte bala...
5.1.2(f) - Diagnostic uses of excretory productsUrine is an excretory product, but it is also a useful biological sample. It can carry hormones, drugs and drug metabolites that give evidence about a person's physiological state or exposure to particular substances. In this lesson you will learn how urine samples are used in diagnostic tests, h...
5.1.3 Neuronal communication
5.1.3(a) - Sensory receptors as transducersSensory receptors are the input side of a mammalian nervous response. They detect particular forms of stimulus, convert that stimulus into an electrical signal, and allow the nervous system to receive information about changes inside or outside the body. In this lesson, the Pacinian corpuscle is...
5.1.3(b) - Sensory, relay and motor neuronesNeurones are specialised cells that carry nerve impulses so an animal can detect a change, process information and produce a response. In this lesson you will learn how sensory, relay and motor neurones differ in structure and function, and why myelin changes the speed of impulse transmission. Th...
5.1.3(c) - Generation and transmission of nerve impulsesA nerve impulse is an action potential: a rapid, temporary change in the electrical potential difference across a neurone membrane. In mammals, this signal is generated by controlled ion movements and transmitted along axons quickly enough for coordinated responses. This lesson follows one impuls...
5.1.3(d) - Synapses and neurotransmissionNeurones carry action potentials along their membranes, but one neurone usually has to pass information to another cell across a tiny gap. In this lesson you will learn how a cholinergic synapse uses acetylcholine to transmit a signal, and how synapses help decide whether a postsynaptic neurone f...
5.1.4 Hormonal communication
5.1.4(a)-(b) - Endocrine communication and adrenal glandsHormones let one part of the body alter the activity of cells somewhere else. In this lesson you will learn the core route of endocrine communication: secretion into blood, transport in blood, and detection by target cells or tissues. You will then use the adrenal glands as the OCR example of end...
5.1.4(c)(i)-(ii) - Pancreas histology and endocrine tissueThe pancreas is useful in hormonal communication because its endocrine tissue releases hormones into the blood. In this lesson you will learn how that endocrine tissue appears in stained pancreas sections, how it differs from the surrounding exocrine tissue, and how to make accurate observations...
5.1.4(d) - Regulation of blood glucose concentrationBlood glucose concentration must stay within a narrow enough range for cells to receive a reliable supply of respiratory substrate. In this lesson, you will follow the two main hormonal feedback branches: insulin lowers blood glucose concentration, glucagon raises it, and the liver is the main or...
5.1.4(e)-(f) - Diabetes mellitus causes and treatmentsDiabetes mellitus is a blood-glucose control disorder, but the two main types have different causes and therefore different treatment logic. In this lesson you will learn how Type 1 and Type 2 diabetes mellitus differ, why insulin from genetically modified bacteria matters, and why potential stem...
5.1.5 Plant and animal responses
5.1.5(a)(i)-(ii) - Plant responses, tropisms and practicalsPlants do not have nerves or muscles like animals, but they still detect changes in their surroundings and respond in ways that improve survival. In this lesson, you will learn the range of plant responses, how tropisms are named, and how phototropism and geotropism can be investigated using cont...
5.1.5(b) - Roles of plant hormonesPlants coordinate growth, survival and seasonal changes using chemical signals called hormones. In this lesson you will learn how plant hormones help deciduous plants lose leaves, how they control seed germination, and how they close stomata during water stress. The important skill is to link eac...
5.1.5(c)-(d) - Auxin and gibberellin experimental evidencePlant hormones are not accepted as important just because they are present in a plant. Biologists need experiments that change the hormone, measure a growth response, and use controls to show that the hormone is a likely cause. In this lesson, you will learn how to interpret evidence for auxin in...
5.1.5(e) - Plant hormone growth practicalsPlant hormones can be investigated by applying known concentrations to growing plant material and measuring a growth response. In this lesson, you will learn how to design a valid plant-hormone growth practical, prepare a dilution series, process root or shoot data, and decide what the results ca...
5.1.5(f) - Commercial uses of plant hormonesPlant hormones can be used commercially because they change plant growth, development or ripening in predictable ways when the dose, timing and conditions are controlled. In this lesson you will learn the three uses named in this specification point: controlling fruit ripening, using rooting powd...
5.1.5(g) - Organisation of the mammalian nervous systemThis lesson is about the map of the mammalian nervous system before the next lessons zoom in on the brain, reflexes and coordinated responses. The key skill is to use two different classification lenses accurately: a structural lens and a functional lens. That prevents a common exam error: mixing...
5.1.5(h) - Human brain structure and functionsThe brain contains specialised regions that coordinate different functions. This lesson links the gross structure to the functions of five parts: the cerebrum, cerebellum, medulla oblongata, hypothalamus and pituitary gland. The key skill is to link a named part to a precise function or symptom,...
5.1.5(i) - Reflex actions and survival valueReflex actions are rapid, automatic responses that protect the body before there is time for a conscious decision. In this lesson you will use the knee jerk reflex to see how a reflex arc links a stimulus to a response, why a short pathway has survival value, and how repeated measurements can sup...
5.1.5(j) - Fight or flight and adrenaline signallingA sudden threat needs a whole-body response, not one isolated organ changing on its own. In this lesson you will learn how the nervous and endocrine systems coordinate the mammalian fight-or-flight response, then zoom into the outline cell-signalling pathway for adrenaline. The key distinction is...
5.1.5(k) - Hormonal and nervous control of heart rateYour heart is myogenic, so each normal beat begins within the heart itself. The rate of those beats is still adjustable: hormones and autonomic nerves can make the sino-atrial node start waves of excitation more often or less often. In this lesson, you will connect the biology of heart-rate contr...
5.1.5(l)(i)-(ii) - Mammalian muscle structure and contractionMuscle contraction is a response mechanism: a nervous signal is converted into movement by protein filaments inside muscle fibres. In this lesson, you will compare the three mammalian muscle types, zoom into skeletal muscle structure, then follow the neuromuscular junction and sliding filament mo...
5.2.1 Photosynthesis
5.2.1(a) - Photosynthesis and respiration interrelationshipPhotosynthesis builds organic molecules using light energy, while respiration transfers energy from organic molecules to ATP. Their reactants and products link the processes. Comparing their rates explains why a leaf can take up or release carbon dioxide as light changes.
5.2.1(b) - Chloroplast structure and photosynthesis sitesA chloroplast separates light capture from carbon fixation. Its internal membranes hold the light-dependent machinery, while the surrounding stroma contains enzymes that use its products to build organic molecules.
5.2.1(c)(i)-(ii) - Photosynthetic pigments and TLCIn this lesson you are learning why plants need several photosynthetic pigments, how those pigments are arranged in photosystems, and how thin layer chromatography can separate pigments from leaf extract. This matters because pigments are the first link between light energy and the chemical react...
5.2.1(d) - Light-dependent stage of photosynthesisThe light-dependent stage is the energy-conversion stage of photosynthesis. It does not make glucose directly; it uses light energy to make ATP and reduced NADP, which can then provide energy and reducing power for later metabolic processes. In this lesson, you will follow the electron pathway, t...
5.2.1(e) - Light-independent stage and the Calvin cycleThe Calvin cycle fixes carbon dioxide in the chloroplast stroma. Follow the carbon atoms from RuBP through GP to TP, then distinguish the energy supplied by ATP from the reducing power supplied by reduced NADP.
5.2.1(f) - Uses of triose phosphate and RuBP regenerationTriose phosphate is the point where photosynthesis becomes useful cell chemistry. In the Calvin cycle, carbon dioxide is fixed and reduced to make TP; in this lesson you will track what that TP can become. The important balance is that some TP is used as a starting material for synthesis, while s...
5.2.1(g)(i)-(ii) - Photosynthesis limiting factors and practicalsPhotosynthesis does not run at one fixed speed. Its rate depends on the environmental factor that is currently holding the process back, and that same factor can change the amounts of GP, TP and RuBP inside chloroplasts. In this lesson you will connect limiting factors to the Calvin cycle, water...
5.2.2 Respiration
5.2.2(a)-(b) - Need for cellular respiration and mitochondriaCellular respiration is not the same as breathing. It is the cellular process that transfers energy stored in complex organic molecules to ATP, the immediate energy source for biological processes. In this lesson you will learn why plants, animals and microorganisms all need respiration, then con...
5.2.2(c) - GlycolysisGlycolysis is the first stage in transferring energy from glucose into ATP. In this lesson you will learn where glycolysis happens, how one six-carbon glucose molecule is split and oxidised, and why the products are described as a small ATP yield plus reduced NAD. Track carbon, phosphate and hydr...
5.2.2(d)-(e) - Link reaction and Krebs cycleGlycolysis leaves the cell with pyruvate, but most of the chemical energy remains in the pyruvate molecules. In this lesson you will follow what happens to pyruvate in the mitochondrial matrix: the link reaction makes acetyl CoA, and the Krebs cycle releases carbon dioxide, reduces coenzymes and...
5.2.2(f)-(g) - Coenzymes and oxidative phosphorylationCellular respiration only keeps going because small carrier molecules move useful chemical cargo from one enzyme-controlled stage to the next. In this lesson, you will separate the roles of NAD, FAD and coenzyme A, then follow how reduced coenzymes feed electrons into oxidative phosphorylation. T...
5.2.2(h) - Chemiosmotic theoryATP production in respiration and photosynthesis depends on a surprisingly similar idea: a membrane can store energy as a proton gradient. In this lesson you will learn how an electron transport chain, a proton gradient and ATP synthase work together in oxidative phosphorylation and photophosphor...
5.2.2(i)(i)-(ii) - Anaerobic respiration and yeast practicalsThis lesson explains how eukaryotic cells keep making a small amount of ATP when oxygen is not available in sufficient supply. You will compare anaerobic respiration in mammalian muscle and yeast, then use yeast as a practical model for measuring respiration rate. The central idea is simple but p...
5.2.2(j)-(k) - Respiratory substrates and respiratory quotientCells do not have to use only glucose as a fuel. Carbohydrates, lipids and proteins can all act as respiratory substrates, but they differ in how much energy they release per gram and in the gas-exchange pattern they produce. In this lesson you will learn how to compare those substrates and how t...
5.2.2(l) - Respirometers and factors affecting respiration rateRespiration rate is not just a pathway idea; it can be investigated by measuring a physical change over time. In this lesson, you will learn how respirometers are used to estimate oxygen uptake, how to design fair investigations into temperature, substrate concentration and substrate type, and ho...
Module 6: Genetics, evolution and ecosystems
6.1.1 Cellular control
6.1.1(a) - Gene mutations and protein effectsA gene mutation is a change in the sequence of nucleotides within a gene. That small molecular change can matter because a gene's nucleotide sequence is used to produce a polypeptide, and the amino-acid sequence affects the protein's shape and function. Substitution, insertion and deletion can ea...
6.1.1(b) - Regulation of gene expressionIn this lesson you learn how cells control whether a gene is used, how an RNA transcript is processed, and whether a protein becomes active after it has been made. The same DNA can lead to very different cell activity because gene expression is regulated at several points. The examples are the la...
6.1.1(c) - Homeobox and Hox genes in body plansAn embryo is not built because every cell has different DNA. Most cells have the same genome, but different genes are switched on and off in different places and at different times. In this lesson you will learn how conserved Homeobox genes regulate gene expression, and how Hox genes, as a subset...
6.1.1(d) - Mitosis and apoptosis in body formBody form is not produced by cell division alone. During development, some cells are added, some cells are kept alive, and some cells are deliberately removed. In this lesson, you will see how mitosis and apoptosis work together as controlled mechanisms, and how genes regulating these processes c...
6.1.2 Patterns of inheritance
6.1.2(a)(i)-(ii) - Phenotypic variation and sexual reproductionVariation is why individuals in the same species are not identical. In this lesson you will separate phenotypic variation caused by genes, phenotypic variation caused by the environment, and genetic variation generated by sexual reproduction. The aim is to explain the chain clearly: genes and env...
6.1.2(b)(i) - Genetic diagrams for inheritance patternsGenetic diagrams are a way of turning meiosis and fertilisation into a clear probability argument. In this lesson you will learn how to build diagrams for monogenic, dihybrid, multiple allele, codominant and sex-linked inheritance. The aim is not to memorise one square, but to use the same logic...
6.1.2(b)(ii) - Phenotypic ratios, linkage and epistasisPhenotypic ratios are the bridge between a genetic cross and an explanation of inheritance. In this lesson you will use ratios as evidence for three patterns: autosomal linkage, sex linkage and epistasis. The aim is not just to name the pattern, but to explain why the observed ratio is different...
6.1.2(c) - Chi-squared test for genetic crossesGenetic crosses often predict a neat phenotypic ratio, but real offspring counts rarely land exactly on that ratio. This lesson teaches how to use the chi-squared test to decide whether the difference between observed and expected results is small enough to be explained by chance. The formula and...
6.1.2(d) - Continuous and discontinuous variationVariation means differences between individuals. In this lesson, the focus is not every cause of variation, but the genetic reason why some characteristics form a smooth range while others fall into clear categories. The genetic explanation depends on how many genes influence the characteristic a...
6.1.2(e) - Selection, drift, bottlenecks and founder effectsEvolution is not only about dramatic new species appearing. At this scale, it means inherited characteristics in a population changing over generations because allele frequencies change. In this lesson you will compare two broad routes: selection, where survival and reproduction are linked to phe...
6.1.2(f) - Hardy-Weinberg allele-frequency calculationsHardy-Weinberg calculations turn information about alleles and genotypes into estimates for a whole population. The biology is population genetics, but the skill is careful algebra: identify which frequency you have, substitute it into the provided equations, and interpret the answer. OCR provide...
6.1.2(g) - Isolating mechanisms and speciationSpeciation is the evolution of one species into two or more new species. Two routes involve geographical mechanisms in allopatric speciation and reproductive mechanisms in sympatric speciation. The big idea is that isolation reduces gene flow; over many generations, separated gene pools can diver...
6.1.2(h)(i)-(ii) - Artificial selection, breeding and ethicsArtificial selection is evolution directed by human choice rather than by the environment alone. In this lesson you will learn how selective breeding works, why it is useful in plants and animals, why genetic resources including wild types matter, and how to make a balanced ethical judgement abou...
6.1.3 Manipulating genomes
6.1.3(a) - DNA sequencing principles and new techniquesDNA sequencing is the set of methods used to find the order of bases in DNA. In this lesson you will learn the principle behind Sanger sequencing, why newer high-throughput approaches changed the scale of biology, and how to handle the simple rate calculations that often sit beside this topic. Th...
6.1.3(b)(i)-(iii) - Uses of gene sequencing and synthetic biologySequencing a gene or genome gives scientists the order of bases in DNA. The power of sequencing comes from what can be done with those data: comparing genomes, predicting polypeptides, tracking disease, searching for evolutionary relationships and designing new biological systems. The useful step...
6.1.3(c)-(d) - DNA profiling and PCRDNA profiling compares selected regions of DNA so that samples can be matched, excluded, or interpreted for risk. PCR, the polymerase chain reaction, is different: it is the method used to amplify a specific DNA sequence so there is enough DNA to analyse. In this lesson you will learn the princip...
6.1.3(e) - Electrophoresis for nucleic acids and proteinsElectrophoresis is a way of separating biological molecules by making charged molecules move through a gel in an electric field. In this lesson you are learning the principle that makes nucleic acid fragments and proteins separate, how a practical gel is run safely, and how band patterns can be u...
6.1.3(f)(i)-(ii) - Genetic engineering principles and techniquesGenetic engineering is the deliberate transfer of a gene from one organism into another organism so the recipient can gain a new genetic instruction. In this lesson, you will learn the method sequence: isolate a target gene, place it into a vector, form recombinant DNA, and introduce it into a ho...
6.1.3(g) - Ethical issues in genetic manipulationGenetic manipulation can change the characteristics of animals, humans, plants and microorganisms, so the biology quickly becomes a question about who benefits, who might be harmed, and who controls the technology. In this lesson you will learn how to discuss both positive and negative ethical is...
6.1.3(h) - Gene therapy in medicineGene therapy is one medical use of manipulating genomes: the aim is to change gene expression in a patient's cells so that a disease is treated. In this lesson, you will learn the core principle, why delivery to the right cells matters, and how somatic cell gene therapy differs from germ line cel...
6.2.1 Cloning and biotechnology
6.2.1(a)(i)-(ii) - Natural plant clones and cuttingsPlant cloning is not always a laboratory technique. Many plants naturally make genetically identical new plants by vegetative propagation, and growers can use the same idea to produce reliable crops and garden plants. In this lesson you will learn how natural plant clones form, why they are usefu...
6.2.1(b)(i)-(ii) - Micropropagation and artificial plant cloningArtificial plant cloning uses laboratory tissue culture to make many plants with the same genotype as a selected parent plant. In this lesson you will learn how micropropagation works, why sterile conditions and plant growth substances matter, and how to evaluate its use in horticulture and agric...
6.2.1(c)-(d)(ii) - Natural and artificial animal cloningAnimal cloning is about copying genetic information into whole animals, either when it happens naturally or when humans intervene. In this lesson, you will learn how embryo splitting can produce natural animal clones, how artificial embryo twinning and somatic cell nuclear transfer produce artifi...
6.2.1(e)-(f) - Microorganisms in biotechnology and foodMicroorganisms can be grown as tiny biological factories. In this lesson, you will learn why bacteria and fungi are useful in biotechnology, then use bacterial and fungal food examples to weigh benefits and risks. The product may be the microbial cells themselves or a substance they make.
6.2.1(g)(i)-(ii) - Aseptic culturing and fermentationMicroorganisms are useful in biotechnology only if they can be grown safely, predictably and with little contamination. In this lesson you will learn how aseptic technique makes small-scale culturing reliable, how serial dilution and agar plates can estimate microbial density, and why industrial...
6.2.1(h)(i)-(ii) - Microbial growth curves and growth practicalsMicroorganisms reproduce fast enough that their population can change by several orders of magnitude in a few hours. In this lesson, you will learn the standard growth curve for a closed culture, how exponential growth is calculated, and how broth cultures, serial dilution and viable counts are u...
6.2.1(i) - Immobilised enzymes in biotechnologyImmobilised enzymes are enzymes held in one place while their substrates and products move around them. Biotechnology uses this idea to turn enzyme reactions into controlled production processes, such as making lactose-reduced milk or converting glucose to fructose. In this lesson you will learn...
6.3.1 Ecosystems
6.3.1(a) - Ecosystems, biotic and abiotic factorsAn ecosystem is not just a dramatic rainforest or a huge coral reef. It can be as small as a rock pool or as local as one large tree, as long as living organisms interact with each other and with the non-living conditions around them. In this lesson, you will learn how to recognise ecosystems of...
6.3.1(b) - Biomass transfers and efficiencyEvery food chain depends on biomass being built, eaten and rebuilt in another organism. This lesson shows how biomass transfer is measured, why the transfer between trophic levels is inefficient, and how to calculate percentage efficiency. You will also learn how human activities can manipulate b...
6.3.1(c) - Nitrogen recycling in ecosystemsNitrogen is needed to build proteins, nucleic acids and ATP, so every ecosystem needs a way to keep usable nitrogen moving through living organisms and soil. This lesson follows that movement through decomposers and the named microorganisms in the nitrogen cycle: Nitrosomonas, Nitrobacter, Azotob...
6.3.1(c) - Carbon cycling in ecosystemsCarbon atoms are constantly reused in ecosystems. In this lesson you will learn how carbon moves between carbon dioxide, organic molecules in living organisms, dead organic matter, decomposers, water and longer-term stores. The key is to follow the process arrows: photosynthesis moves carbon into...
6.3.1(d) - Primary and deflected successionEcosystems are not fixed snapshots. Over time, the species in a community can change because organisms alter the abiotic conditions around them, and those new conditions favour different species. In this lesson, you will learn the process of primary succession from pioneer species to a climax com...
6.3.1(e)(i)-(ii) - Distribution, abundance and ecosystem samplingEcologists often need to find out where organisms live and how common they are without counting every individual in the ecosystem. In this lesson, you will learn how distribution and abundance can be measured using sampling, how to choose a method that fits the organism and habitat, and how to re...
6.3.2 Populations and sustainability
6.3.2(a) - Population size and carrying capacityPopulation size is never just "how many organisms there happen to be". It is the outcome of survival, reproduction, movement and the environment's ability to keep supporting that species. In this lesson you will learn how limiting factors set carrying capacity, how that affects final population s...
6.3.2(b) - Predator-prey relationships and competitionPopulations do not change in isolation. In the same ecosystem, one population may become food for another, or two populations may put pressure on the same limited resource. In this lesson, you will learn how predator-prey relationships affect both populations, and how to distinguish interspecific...
6.3.2(c) - Conservation and preservationProtecting nature is not one single idea. Sometimes humans protect biological resources by managing them carefully; sometimes the aim is to keep them away from human use or disturbance as far as possible. In this lesson, you will learn the difference between conservation and preservation, and how...
6.3.2(d) - Sustainable management of timber and fishingSustainable resource use is not the same as leaving an ecosystem untouched. In this lesson, you will learn how an ecosystem can be managed so that people obtain timber or fish while the resource can keep being replaced. The central biological idea is simple but powerful: harvesting must be limite...
6.3.2(e) - Managing environmental resources and human impactsHuman populations need environmental resources: land, water, food, fuel, space, building materials and places to work or visit. The biological problem is that using those resources can change ecosystems and alter plant and animal populations. In this lesson, you will learn how to explain those ef...