Edexcel IGCSE Biology

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Structure and functions in living organisms

Biological molecules

2.7-2.9 - Biological molecules and food testsFood is made from large biological molecules, and those molecules are built from smaller units. In this lesson you will learn the element patterns and building blocks that Edexcel expects you to recall, then use qualitative food tests to identify glucose, starch, protein and fat in food samples.
2.10-2.12 - Enzyme action and temperatureEnzymes make metabolic reactions happen fast enough for living organisms to survive. This lesson shows how enzymes act as biological catalysts, why their active sites matter, how temperature changes enzyme activity, and how to investigate that effect in a practical.
2.13-2.14B - Enzyme activity and pH practicalEnzymes work because their active sites have a particular shape. This lesson shows how changing pH can alter that shape, then uses a practical investigation to measure the effect of pH on enzyme activity. The practical model is amylase digesting starch, with iodine solution used to show when star...

Nutrition

2.18-2.20 - Photosynthesis reactions and limiting factorsPhotosynthesis is the process that lets flowering plants trap light energy and store it as chemical energy in glucose. In this lesson, the process is treated as an energy conversion, a pair of equations, and a set of rate patterns. The key exam skill is to connect the graph shape to the factor th...
2.21-2.23 - Leaf adaptations, minerals and photosynthesis practicalLeaves are not just flat green surfaces: their layers, air spaces and transport tissues make photosynthesis efficient. Plants also need mineral ions to build the molecules that let them grow. This lesson finishes with the practical logic for showing oxygen production, starch production, and the r...
2.24-2.26 - Balanced diet and energy requirementsA balanced diet is not a diet where every food component is eaten in equal amounts. It is a diet that supplies the right nutrients, in suitable proportions, for the body's needs. Those needs change with the person's activity level, age and pregnancy, so "balanced" always means matched to the indi...
2.27-2.28 - Alimentary canal and peristalsisFood does not just sit inside the body while it is digested. It passes through a muscular tube called the alimentary canal, where different regions carry out different jobs. This lesson follows the route food takes and then explains the muscle action that keeps it moving.
2.29-2.32 - Digestive enzymes, bile and absorptionFood is useful to the body only after large, insoluble molecules have been digested into small, soluble molecules. Digestive enzymes do the chemical breakdown, bile makes lipid digestion more efficient, and the small intestine absorbs the soluble products into transport systems. This lesson follo...
2.33B - Food energy practicalFood contains chemical energy. In this practical, you estimate how much energy a food sample releases by burning it and measuring how much it warms a known mass of water. The method is simple, so the result is an estimate rather than the true food-label value, but it is excellent for learning fai...

Respiration

2.34-2.37 - Aerobic respiration and ATPRespiration is the chemical process that transfers energy from glucose into ATP in living organisms. ATP is the small molecule cells can use directly when they need energy for work such as movement, active transport, and building larger molecules. In this lesson, the main focus is aerobic respira...
2.38 - Anaerobic respirationAnaerobic respiration releases energy from glucose when oxygen is not available. For this lesson, the key skill is to know the word equation in animal cells and the word equation in plant cells. The reactant is the same each time, but the products are different, so the organism named in the quest...
2.39 - Respiration practicalRespiring living organisms release carbon dioxide and heat. In this practical, you investigate those two products using living material such as germinating seeds, then compare the results with suitable controls. The exam focus is not just the observation: it is also whether the method is fair, re...

Gas exchange

2.40B-2.42B - Leaf structure and gas exchangeLeaves are gas-exchange surfaces: carbon dioxide and oxygen must move between the air and living leaf cells. In a leaf, this movement happens by diffusion, so the direction of movement depends on concentration gradients created by photosynthesis and respiration. The leaf is built to make these di...
2.43B-2.45B - Stomata, day - night gas exchange and leaf gas-exchange practicalA leaf is not a sealed sheet. It has tiny adjustable pores called stomata, and those pores let gases diffuse between the air and the living cells inside the leaf. In this lesson you will track how stomata support gas exchange, why a leaf's net exchange changes between darkness, dim light and brig...
2.46-2.47 - Human breathing system and ventilationBreathing is not the same as respiration. Respiration is the chemical release of energy in cells; breathing is the physical movement of air into and out of the lungs. This lesson focuses on the structure of the human thorax and how muscles change its volume to ventilate the lungs.
2.48-2.50 - Alveoli, smoking and breathing practicalGas exchange in humans depends on diffusion across the alveoli, the tiny air sacs at the ends of the bronchioles. This lesson links alveolar structure to fast diffusion, then follows the biological consequences of smoking for the lungs and the circulatory system. It finishes with the specified pr...

Transport

2.51-2.52 - Why multicellular organisms need transportEvery living cell needs substances from its surroundings and must remove waste substances. For very small, simple organisms, diffusion alone can be enough because every part of the cell is close to the cell surface. Multicellular organisms have a different problem: many cells are deep inside the...
2.53-2.55B - Xylem, phloem and water absorptionPlants are multicellular organisms, so leaves, roots, stems and flowers cannot all get the substances they need by short-distance diffusion alone. Flowering plants use two transport tissues with different jobs: phloem moves useful organic substances around the plant, while xylem carries water and...
2.56B-2.58B - Transpiration factors and transpiration practicalPlants lose water all the time, but the rate is not fixed. In this lesson you will learn the Edexcel definition of transpiration, predict how four environmental factors change its rate, and plan a leafy-shoot investigation using a potometer. The exam focus is usually careful cause-effect wording...
2.59-2.61, 2.64B - Blood components, transport and clottingBlood is a transport tissue: it carries useful substances to cells, removes wastes from cells, helps defend the body, and can seal damaged blood vessels. In this lesson, the focus is the composition of blood, the substances carried in plasma, the adaptations of red blood cells for oxygen transpor...
2.62-2.63B - Immune response and vaccinationWhen pathogens enter the body, the immune system responds using white blood cells. In this lesson, the two named white blood cell roles are phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen. The separate-science extension is vaccination: memory cells are...
2.65-2.66 - Heart structure and heart-rate controlThe heart is a muscular pump that keeps blood moving through the lungs and around the body. Its structure matters because each chamber, valve and wall helps blood move in the correct direction. Heart rate then changes when the body needs blood to be pumped faster, especially during exercise or wh...
2.67-2.69 - Blood vessels, circulation and coronary heart diseaseBlood vessels are not just tubes: their walls, lumens and valves match the pressure and job of the blood they carry. This lesson links those vessel adaptations to the whole circulation map, including the vessels serving the lungs, liver and kidneys. It also shows how risk factors can increase the...

Excretion

2.70-2.71 - Excretion overview and plant wastesCells are always carrying out metabolic reactions. Some products of those reactions are useful, but others must be removed because they would build up, disturb conditions inside the organism, or simply be surplus to what the organism needs. In this lesson, excretion means knowing where key waste...
2.72B-2.73B - Kidney function and urinary systemYour kidneys are not just "urine-making organs". They constantly help keep the internal environment suitable for cells by removing metabolic waste and controlling water balance. This lesson focuses on the kidney's two required roles, then follows urine through the named parts of the urinary system.
2.74B-2.75B - Nephron structure and ultrafiltrationInside each kidney, blood is filtered by microscopic structures called nephrons. This lesson follows the named parts of a nephron, then zooms in on the first filtering step: ultrafiltration in the Bowman's capsule. The key exam skill is to separate what happens at the start of the nephron from la...
2.76B-2.79B - Selective reabsorption, ADH and urine compositionThe kidney does not simply filter blood and throw everything filtered away. After useful small molecules and water enter the nephron fluid, selected substances are reabsorbed back into the blood so that only waste and excess substances are lost in urine. This lesson follows two key reabsorption d...

Co-ordination and response

2.80-2.82 - Responses, homeostasis, receptors and effectorsOrganisms do not survive by staying passive while conditions change around them. They detect changes, respond in ways that help them survive, and keep important internal conditions suitable for cells. This lesson sets up the core language for co-ordination and response: stimulus, receptor, effect...
2.83-2.85 - Plant tropisms and auxinPlants do not have nerves or muscles, but they still respond to changes in their environment. Many plant responses are growth responses: one side of a root or stem grows faster than the other side, so the organ bends. This lesson focuses on two directional responses, phototropism and geotropism,...
2.86-2.87 - Nervous system and receptorsHumans use communication systems to control responses. Some responses need fast electrical messages through the nervous system. Others are controlled by chemical hormones carried in the blood. This lesson compares those two systems and shows how sense organs are linked to the central nervous syst...
2.88-2.90 - Synapses and reflex arcsSome nervous responses need to happen fast enough to protect the body before conscious thought has caught up. In this lesson, you will follow an electrical impulse from a stimulated receptor, across synapses, through the central nervous system and out to an effector. The required example is the w...
2.91-2.92 - The eye - structure, focusing and light responseThe eye is a sense organ that acts as a receptor for light. It does more than let light in: it focuses light onto receptor cells in the retina, then sends electrical impulses to the central nervous system. The same eye also adjusts when objects are near or distant, and when light intensity changes.
2.93 - Skin and temperature regulationBody temperature must be kept within a suitable range so that enzyme-controlled reactions can work properly. The skin helps with this by controlling heat loss from the body surface. In this lesson, the three named Edexcel mechanisms are sweating, vasodilation and vasoconstriction.
2.94-2.95B - Hormones and endocrine controlHormones are chemical messages that help coordinate body processes. This lesson focuses on the source, role and effect of the named hormones in the specification: adrenaline, insulin, testosterone, progesterone, oestrogen, and the Biology-only hormones ADH, FSH and LH. The key skill is to link th...

Reproduction and inheritance

Reproduction

3.1-3.2 - Sexual - asexual reproduction and fertilisationReproduction produces new organisms, but not all reproduction works in the same way. This lesson compares sexual and asexual reproduction, then follows the exact fertilisation sequence required by Pearson Edexcel: male gamete plus female gamete, zygote, cell division, embryo. The main exam skill...
3.3-3.4 - Flower structure, pollination and fertilisationFlowers are reproductive organs in flowering plants. Their structures are arranged so that pollen can move from an anther to a stigma, which is pollination. If pollination is followed by pollen tube growth and fertilisation, ovules can become seeds and the ovary can become a fruit.
3.5-3.7 - Seed germination and plant asexual reproductionSeeds do not need to photosynthesise before they germinate because they contain stored food reserves. Germination depends on suitable external conditions, and the practical skill is to test one condition at a time. Plants can also make new plants without seeds, using natural runners or artificial...
3.8-3.10B - Human reproductive systems and menstrual-cycle hormonesHuman reproduction depends on structures that make and move gametes, and on hormones that prepare the uterus and time the release of an egg. This lesson keeps to the Edexcel International GCSE Biology boundary: the male and female reproductive systems, then the menstrual-cycle roles of oestrogen,...
3.11-3.13 - Placenta, amniotic fluid and secondary sexual characteristicsAfter fertilisation, the embryo grows inside the uterus and needs a steady supply of useful substances. The placenta and amniotic fluid support this early development in different ways: one supplies, the other protects. Later, sex hormones trigger the changes of puberty called secondary sexual ch...

Inheritance

3.14-3.16B - DNA, genes and chromosomesDNA is the molecule that carries genetic information. In this lesson, you will connect three levels of organisation: the whole genome, chromosomes in the nucleus, and genes as sections of DNA. The separate-science extension then adds the shape of DNA and the base-pairing rule that holds its two s...
3.17B-3.18B - Protein synthesis and the genetic codeEvery cell needs proteins: enzymes, membrane proteins, structural proteins and many others. A gene is useful because its base sequence can be used as instructions for building a particular protein. In this lesson, you follow those instructions from DNA to mRNA, then from mRNA to a chain of amino...
3.19-3.22 - Alleles, inheritance terms and variation typesInheritance uses precise vocabulary. A gene can have different versions, and those versions can affect the characteristics an organism inherits. This lesson builds the terms needed before genetic diagrams: allele, genotype, phenotype, dominant, recessive, homozygous, heterozygous, codominance and...
3.23, 3.25 - Monohybrid inheritance and genetic diagramsA monohybrid cross follows the inheritance of one characteristic controlled by one gene. Genetic diagrams are a tidy way to show how parental alleles can combine in offspring, then use those combinations to predict probabilities. In this lesson, the focus is not memorising one cross, but learning...
3.24, 3.26-3.27 - Family pedigrees and sex determinationPedigrees and sex-determination diagrams are both ways of turning inheritance into evidence you can read. A family pedigree shows how a characteristic appears in different family members across generations. A sex-determination genetic diagram shows how X and Y chromosomes combine at fertilisation...
3.28-3.29 - MitosisMitosis is cell division that keeps the chromosome set the same. When a diploid cell divides by mitosis, it produces two cells with identical sets of chromosomes. This makes mitosis useful whenever an organism needs more genetically identical cells, such as during growth, repair, cloning and asex...
3.30-3.32 - Meiosis, gametes and chromosome numbersSexual reproduction needs gametes, such as sperm cells and egg cells, to join at fertilisation. Meiosis is the cell division that makes this possible: it produces gametes with half the usual chromosome number. That halving, followed by random fertilisation, helps keep the chromosome number stable...
3.33 - Variation and its causesVariation means that individuals of the same species are not all identical. Pearson Edexcel asks for one precise idea here: variation within a species can be caused by genetic factors, environmental factors, or a combination of both. The skill is to identify the cause and explain it without drift...
3.34-3.37B - Mutation and effects on proteins - phenotypeA mutation is a change in genetic material. Most mutations do not cause a noticeable change in phenotype, but a mutation can matter if it changes the amino acid sequence of a protein and the protein's function. This lesson follows the chain from DNA change to possible phenotype change, then finis...
3.38-3.39 - Natural selection and antibiotic resistanceDarwin's theory explains how populations can change over many generations without any organism choosing to change. Natural selection depends on inherited variation, different chances of survival and reproduction, and the passing on of advantageous characteristics. Antibiotic resistance is the sam...

Ecology and the environment

Human influences on the environment

4.12-4.15 - Air pollution, greenhouse gases and global warmingAir pollution can damage living organisms directly, while greenhouse gases change how much heat is retained by Earth's atmosphere. This lesson keeps those ideas separate: sulfur dioxide and carbon monoxide are air pollutants with biological effects, and the named greenhouse gases are linked to th...
4.16-4.17 - Water pollution and eutrophicationWater pollution can damage an ecosystem even when the pollutant does not poison every organism directly. Sewage and fertiliser minerals can both change the growth of microorganisms, algae and aquatic plants. The key biological consequence is often a fall in dissolved oxygen, so animals and other...
4.18B - Deforestation and environmental consequencesDeforestation changes more than the number of trees in an area. Removing forest cover exposes soil, changes how water returns to the atmosphere, and alters the movement of carbon between living biomass, soil and air. Edexcel questions usually reward linked cause-and-effect chains, so the aim is t...

Use of biological resources

Food production

5.1-5.4 - Crop yield and pest controlCrop yield is the amount of useful crop harvested from a given area or from a set of plants. Farmers can increase yield by improving the conditions for photosynthesis and growth, and by reducing losses caused by pests. In this lesson, keep the scope tight: protected growing, carbon dioxide and te...
5.5-5.8 - Microorganisms, fermentation and food productionMicroorganisms are useful in food production because their respiration changes raw materials into products humans want. In this lesson, yeast is used to explain bread making and a required yeast practical, Lactobacillus is used to explain yoghurt production, and industrial fermenters are used to...
5.9B - Fish farmingFish farming is the rearing of large numbers of fish to provide food, especially protein-rich food. A fish farm is more controlled than a natural lake or sea, but that control has to be managed carefully: crowded fish can run out of oxygen, spread disease, produce waste and eat each other. This l...