---
title: "Organisms & Life Processes"
description: "132 topics in Science, in the order they build on each other."
canonical: https://lightmysky.com/learn/science/areas/organisms-and-life-processes
source: https://lightmysky.com/learn/science/areas/organisms-and-life-processes.md
retrieved: 2026-10-19
---

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# Organisms & Life Processes

132 topics in Science, in the order they build on each other.

Page: https://lightmysky.com/learn/science/areas/organisms-and-life-processes

- [Common Plants & Trees](https://lightmysky.com/learn/science/common-plants-and-trees-mt_j7cer_Nmor): Identify and name common wild and garden plants, including deciduous and evergreen trees
- [Living Things Vocabulary](https://lightmysky.com/learn/science/living-things-vocabulary-mt_zexbopQjG0): Name and use vocabulary for what makes something living — alive, dead, never been alive, movement, nutrition, growth, reproduction, sensitivity, excretion — and apply these terms when classifying objects and explaining why plants and animals count as living things
- [Naming Common Animals](https://lightmysky.com/learn/science/naming-common-animals-mt_zVLOm6U7bh): Identify and name common animals from major groups: fish, amphibians, reptiles, birds, and mammals
- [Animal Body Groups](https://lightmysky.com/learn/science/animal-body-groups-mt_fDoE-pL6Jv): Describe and compare the external body structure of common animals across groups (fish, amphibians, reptiles, birds, mammals)
- [Body Parts & Senses](https://lightmysky.com/learn/science/body-parts-and-senses-mt_83gRQ9OPkc): Identify, name, and locate basic parts of the human body and associate each body part with its sense
- [Herbivores, Carnivores & Omnivores](https://lightmysky.com/learn/science/herbivores-carnivores-and-omnivores-mt_13CtLTcWUB): Classify common animals as carnivores (eat meat), herbivores (eat plants), or omnivores (eat both)
- [Parts of a Plant](https://lightmysky.com/learn/science/parts-of-a-plant-mt_xT6jPzyj92): Identify and describe the basic structure of common flowering plants (roots, stem, leaves, flowers) and trees (roots, trunk, branches, leaves)
- [What Living Things Need](https://lightmysky.com/learn/science/what-living-things-need-mt_L1469gt34A): Understand what plants and animals (including humans) need to survive: water, food, air, and suitable conditions
- [Seeds & Plant Growth](https://lightmysky.com/learn/science/seeds-and-plant-growth-mt_0B64gfJf7j): Observe and describe how seeds and bulbs grow into mature plants through stages of germination and growth
- [What Plants Need to Grow](https://lightmysky.com/learn/science/what-plants-need-to-grow-mt_3v0VNkwquK): Understand that plants need water, light, and a suitable temperature to grow and stay healthy
- [Animal Classification Vocabulary](https://lightmysky.com/learn/science/animal-classification-vocabulary-mt_1J5fwxNDxL): Use vocabulary for classifying animals and describing life cycles — vertebrate, invertebrate, mammal, bird, reptile, amphibian, fish, insect, arachnid, larva, pupa, metamorphosis, gestation, offspring, complete metamorphosis, incomplete metamorphosis — and apply these correctly when sorting and comparing organisms
- [Animal Nutrition](https://lightmysky.com/learn/science/animal-nutrition-mt_E1wR8IfCV6): Understand that animals, including humans, need the right types and amounts of nutrition, and that animals cannot make their own food
- [How Plant Parts Work](https://lightmysky.com/learn/science/how-plant-parts-work-mt_6xsEXxKdUX): Identify and describe the functions of different parts of flowering plants: roots absorb water and nutrients, stems transport materials, leaves make food, flowers enable reproduction
- [Pollination & Seed Dispersal](https://lightmysky.com/learn/science/pollination-and-seed-dispersal-mt_WNBHZ1d94L): Understand the life cycle of flowering plants including pollination, seed formation, and seed dispersal
- [Water Transport in Plants](https://lightmysky.com/learn/science/water-transport-in-plants-mt_GF6L7J4MNN): Investigate how water is transported within plants, using observations such as coloured water being drawn up through a stem
- [What Plants Need to Thrive](https://lightmysky.com/learn/science/what-plants-need-to-thrive-mt_lutxvMlkwS): Explore and compare the requirements of plants for life and growth: air, light, water, nutrients from soil, and room to grow
- [Senses, Brain & Responses](https://lightmysky.com/learn/science/senses-brain-and-responses-mt_IzlVK0Eony): Use a model to describe that animals receive information through their senses, process it in their brain, and respond in different ways
- [Plants Grow from Air & Water](https://lightmysky.com/learn/science/plants-grow-from-air-and-water-mt_3-ii06P4YS): Support an argument that plants get the materials they need for growth chiefly from air and water, not from the soil
- [Energy from Food & the Sun](https://lightmysky.com/learn/science/energy-from-food-and-the-sun-mt_PYPs2yD2sn): Use models to describe that energy in animals' food was once energy from the sun, transferred through plants or other organisms
- [Cells Under the Microscope](https://lightmysky.com/learn/science/cells-under-the-microscope-mt_VfA4xo4kUv): Understand that all living organisms are made of cells and use a light microscope to observe, interpret, and record cell structure
- [Nutrients in a Healthy Diet](https://lightmysky.com/learn/science/nutrients-in-a-healthy-diet-mt_sDmrVCfzqt): Identify the seven components of a healthy diet — carbohydrates, lipids, proteins, vitamins, minerals, dietary fibre, and water — and explain the role of each in the body
- [Calculating Dietary Energy](https://lightmysky.com/learn/science/calculating-dietary-energy-mt_83KkBCtVyR): Calculate and evaluate energy intake and requirements in a healthy daily diet, interpreting food labels and nutritional data
- [Diet Imbalance & Deficiency](https://lightmysky.com/learn/science/diet-imbalance-and-deficiency-mt_NZHFcEtTyI): Explain the health consequences of an imbalanced diet including obesity (excess energy), starvation (severe energy deficit), and deficiency diseases (lack of specific nutrients, e.g. scurvy, rickets)
- [Parts of Plant and Animal Cells](https://lightmysky.com/learn/science/parts-of-plant-and-animal-cells-mt_bABr-c2DfV): Describe the functions of the main components of plant and animal cells: cell wall, cell membrane, cytoplasm, nucleus, vacuole, mitochondria, ribosomes, and chloroplasts
- [Plant cells vs animal cells](https://lightmysky.com/learn/science/plant-cells-vs-animal-cells-mt_fhqBH9scsU): Compare typical plant and animal cells, identifying shared parts and differences involving cell walls, large central vacuoles and chloroplasts.
- [Cells to organ systems](https://lightmysky.com/learn/science/cells-to-organ-systems-mt_7hB8s5eOP1): Describe organisation in humans and other complex multicellular organisms: cells, tissues, organs, organ systems and the whole organism.
- [Photosynthesis](https://lightmysky.com/learn/science/photosynthesis-mt_zM5vu31jgl): Explain photosynthesis as the process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen, and describe how mineral nutrients are absorbed through roots
- [Single-Celled Organisms](https://lightmysky.com/learn/science/single-celled-organisms-mt_g9RcQOhU5d): Explain how unicellular organisms such as bacteria and Amoeba carry out all the functions of life within a single cell
- [Using a Microscope](https://lightmysky.com/learn/science/using-a-microscope-mt_lMLeNLDRO8): Use a light microscope correctly to prepare, focus, and examine biological specimens, including making accurate labelled drawings at an appropriate magnification
- [How Diffusion Works](https://lightmysky.com/learn/science/how-diffusion-works-mt_i80I-1MLP2): Explain diffusion as the net movement of particles from a region of higher concentration to lower concentration, and describe its role in moving materials (oxygen, carbon dioxide, glucose) in and between cells
- [Gas Exchange & Breathing](https://lightmysky.com/learn/science/gas-exchange-and-breathing-mt_V9SQS9gLFw): Describe the structure of the human gas exchange system (trachea, bronchi, bronchioles, alveoli) and explain how the mechanism of breathing — using pressure changes from rib and diaphragm movement — moves air in and out of the lungs
- [Aerobic Respiration](https://lightmysky.com/learn/science/aerobic-respiration-mt_mquPi2IP-J): Explain aerobic respiration as the process by which organisms release energy from glucose using oxygen, producing carbon dioxide and water; write and interpret the word equation: glucose + oxygen → carbon dioxide + water
- [Anaerobic Respiration](https://lightmysky.com/learn/science/anaerobic-respiration-mt_TKZefYXaVS): Explain anaerobic respiration in animals as the incomplete breakdown of glucose to lactic acid when oxygen is in short supply, causing muscle fatigue; contrast this with aerobic respiration in terms of energy yield and products
- [Pathogens & the Immune System](https://lightmysky.com/learn/science/pathogens-and-the-immune-system-mt_1VIE8FlZvL): Explain how pathogens (bacteria, viruses, and fungi) cause disease and describe how the immune system responds, including the roles of white blood cells (phagocytosis, antibody production) and the concept of immunity
- [Osmosis in Plant and Animal Cells](https://lightmysky.com/learn/science/osmosis-in-plant-and-animal-cells-mt_XciCLO69xG): Water crosses a partially permeable membrane from the more dilute solution towards the more concentrated one. Explains turgid, flaccid and plasmolysed plant cells, and why an animal cell in pure water can burst.
- [Active Transport Against the Gradient](https://lightmysky.com/learn/science/active-transport-against-the-gradient-mt_BQf1bgo9oM): A cell can move substances from a low concentration to a high one by spending energy released in respiration. Covers mineral ion uptake by root hairs and glucose absorption from the small intestine.
- [Prokaryotic and Eukaryotic Cells](https://lightmysky.com/learn/science/prokaryotic-and-eukaryotic-cells-mt_vlL4GinuH6): Compare a bacterial cell with plant and animal cells: a free loop of DNA and plasmids on one side, a nucleus and membrane-bound organelles on the other. Sets the size scale the rest of cell biology works in.
- [Magnification and Scale Calculations](https://lightmysky.com/learn/science/magnification-and-scale-calculations-mt_0Iowx29ddQ): Use magnification as image size divided by actual size, and convert between millimetres, micrometres and nanometres without losing a factor of a thousand. Includes reading a scale bar and choosing a light or electron microscope by the detail needed.
- [Surface Area to Volume Ratio and Exchange Surfaces](https://lightmysky.com/learn/science/surface-area-to-volume-ratio-and-exchange-surfaces-mt_1TclgVUxfa): Work out surface area to volume ratios for cubes and simple shapes and show that the ratio falls as size rises. That falling ratio is why a large organism needs lungs, gills or a folded gut lining.
- [The Cell Cycle and Mitosis](https://lightmysky.com/learn/science/the-cell-cycle-and-mitosis-mt_gllZOZEzW7): A cell copies its DNA, then divides into two cells with identical chromosomes. Covers the stages of the cycle, what mitosis produces, and where in the body it is happening now.
- [Gas Exchange Surfaces Across Taxa](https://lightmysky.com/learn/science/gas-exchange-surfaces-across-taxa-mt_gCcrXUH0aP): Insects, fish, leaves and mammals solve one problem with different surfaces, and every solution ends up thin, large and moist. Comparing them shows which features are forced by physics rather than by ancestry.
- [Fick's Law and What Sets the Rate of Exchange](https://lightmysky.com/learn/science/ficks-law-and-what-sets-the-rate-of-exchange-mt_6JreZAFeb-): Rate of diffusion rises with surface area and with the concentration difference, and falls with the distance crossed. The relationship turns comparisons between exchange surfaces into arithmetic.
- [Ventilation in Insects, Fish and Mammals](https://lightmysky.com/learn/science/ventilation-in-insects-fish-and-mammals-mt_Thd06O06Vr): Ventilation keeps the concentration difference high by replacing the medium at the exchange surface. Tracheal pumping, countercurrent flow in gills and pressure changes in the thorax are three answers to one demand.
- [Water and Hydrogen Bonding in Living Systems](https://lightmysky.com/learn/science/water-and-hydrogen-bonding-in-living-systems-mt_79dzlo6fD5): Hydrogen bonds between water molecules give water its cohesion, its high heat capacity and its behaviour as a solvent. Every one of those properties traces back to the same charge separation across the molecule.
- [Condensation, Hydrolysis and the Polymers of Life](https://lightmysky.com/learn/science/condensation-hydrolysis-and-the-polymers-of-life-mt_v-M8zHd22C): Carbohydrates, proteins and nucleic acids are all polymers joined by condensation and taken apart by hydrolysis. One bond-making rule covers three families of molecule.
- [Lipids: Built by Condensation but Not Polymers](https://lightmysky.com/learn/science/lipids-built-by-condensation-but-not-polymers-mt_8-JYrLwjCw): Triglycerides and phospholipids form by condensation yet have no repeating monomer, so they sit outside the polymer rule. The phospholipid has one end attracted to water and one repelled, which is what later builds a membrane.
- [Protein Structure from Primary to Quaternary](https://lightmysky.com/learn/science/protein-structure-from-primary-to-quaternary-mt_bMdQS2lqSI): A protein's shape is described in four levels, from the order of amino acids up to several chains held together. Each level is kept by named bonds, and the finished shape decides what the protein can do.
- [The Fluid Mosaic Model of the Cell Membrane](https://lightmysky.com/learn/science/the-fluid-mosaic-model-of-the-cell-membrane-mt_-xnAIG5hFc): The membrane is a phospholipid bilayer with proteins, cholesterol and glycoproteins set into it, and the parts drift. The model is what explains which molecules cross unaided and which need a protein.
- [Cell Cycle Checkpoints, Control and Cancer](https://lightmysky.com/learn/science/cell-cycle-checkpoints-control-and-cancer-mt_nwNmCVnZ7O): Checkpoints hold a cell back at set points in the cycle until conditions and DNA are sound. Tumours follow when the genes that run those checkpoints stop working.
- [Co-transport and Coupled Movement Across Membranes](https://lightmysky.com/learn/science/co-transport-and-coupled-movement-across-membranes-mt_pzQ8n3FWNV): A pump spends ATP to build an ion gradient, and a second protein then uses that gradient to drag another molecule in with the ion. Glucose uptake at the gut wall is the standard case.
- [Water Potential and Osmosis Quantified](https://lightmysky.com/learn/science/water-potential-and-osmosis-quantified-mt_dFBz-cE6W0): Water potential puts a number on the tendency of water to move, made from solute potential and pressure potential. Cells are then predicted to gain or lose water from the numbers alone.
- [Protists: the eukaryotes that are not plants, animals or fungi](https://lightmysky.com/learn/science/protists-the-eukaryotes-that-are-not-plants-animals-or-fungi-mt_CHb8H727nW): Protists are diverse eukaryotes informally grouped outside animals, land plants and fungi. They include feeding, photosynthetic and mixed lifestyles. Their cell structures and genes provide evidence of bacterial organelle origins, later organelle loss and uptake of photosynthetic eukaryotes.
- [Animal Life Stages](https://lightmysky.com/learn/science/animal-life-stages-mt_oR6dwRj2Ll): Recognise that animals, including humans, have offspring which grow into adults, and describe basic animal life stages
- [Offspring resemble parents](https://lightmysky.com/learn/science/offspring-resemble-parents-mt_cEzX5r7kp0): Observe that young plants and animals resemble their parents but are not identical, recognising inherited similarities and individual differences
- [Drawing Life Cycle Diagrams](https://lightmysky.com/learn/science/drawing-life-cycle-diagrams-mt_7EqhgErJyU): Draw and interpret life cycle diagrams for flowering plants, insects (complete and incomplete metamorphosis), birds, and mammals — labelling stages, describing transitions, and comparing cycles across species
- [Life Cycles of Organisms](https://lightmysky.com/learn/science/life-cycles-of-organisms-mt_4IVWRAZoNC): Develop models to describe that organisms have unique and diverse life cycles but all share the common stages of birth, growth, reproduction, and death
- [Inheritance Vocabulary](https://lightmysky.com/learn/science/inheritance-vocabulary-mt_h4abSktujo): Use vocabulary for variation and inheritance: inherited characteristic, acquired characteristic, variation, offspring, trait, species, breed, genetic and environment. Apply these words when comparing organisms and explaining similarities and differences within and between species.
- [Inherited characteristics](https://lightmysky.com/learn/science/inherited-characteristics-mt_1wxwg782yX): Analyse and interpret data to provide evidence that plants and animals have traits inherited from parents and that variation of these traits exists in a group of similar organisms
- [Traits: inherited and environmental](https://lightmysky.com/learn/science/traits-inherited-and-environmental-mt_Tls5qJ4p0L): Use evidence to support the explanation that traits can be influenced by the environment as well as inheritance
- [Human Reproduction](https://lightmysky.com/learn/science/human-reproduction-mt_tQkCzRcWG7): Describe the structure and function of the male and female human reproductive systems, and explain the processes of fertilisation, gestation, and birth including the role of the placenta
- [Transpiration and Transport in Plants](https://lightmysky.com/learn/science/transpiration-and-transport-in-plants-mt_AqN0vL8QRu): Water pulled up the xylem replaces what evaporates from the leaves, while phloem carries dissolved sugar to where it is used or stored. Covers stomata, guard cells, and what changes the transpiration rate.
- [Cohesion-Tension and Water Movement in the Xylem](https://lightmysky.com/learn/science/cohesion-tension-and-water-movement-in-the-xylem-mt_9_TORolYIl): Evaporation from leaf cell walls creates tension that pulls water through the xylem. Hydrogen bonding gives the water column cohesion. Stomatal closure reduces transpiration-driven flow, while gas bubbles can interrupt individual columns.
- [Translocation and the Mass Flow Hypothesis](https://lightmysky.com/learn/science/translocation-and-the-mass-flow-hypothesis-mt_WZ8id0kou4): Sugars are loaded into the phloem at a source, water follows by osmosis, and the pressure built there pushes sap towards a sink. The hypothesis is judged against ringing experiments and tracer evidence.
- [Variation & Survival Advantage](https://lightmysky.com/learn/science/variation-and-survival-advantage-mt_UR5LvBeyF1): Use evidence to explain how variations in characteristics among individuals of the same species may provide advantages in surviving, finding mates, and reproducing
- [Evolution vocabulary](https://lightmysky.com/learn/science/evolution-vocabulary-mt_lWqmKn5Jvr): Use technical vocabulary for evolution and natural selection — adaptation, evolution, natural selection, extinct, extinction, fossil record, species, common ancestor, mutation, variation — and explain the mechanism of natural selection using these terms in the correct sequence
- [How living things adapt to environments](https://lightmysky.com/learn/science/how-living-things-adapt-to-environments-mt_LRzjbo1Fn6): Identify how animals and plants are adapted to suit their environment and understand that adaptation may lead to evolution over time
- [Plant Reproduction](https://lightmysky.com/learn/science/plant-reproduction-mt_ck57CDFGet): Describe the structure of a flower and explain the processes of wind and insect pollination, fertilisation, seed and fruit formation, and seed dispersal in plants
- [Plant growth responses: tropisms and the hormones behind them](https://lightmysky.com/learn/science/plant-growth-responses-tropisms-and-the-hormones-behind-them-mt_q1N7OG2_6j): Plants change their direction of growth in response to light and gravity. Unequal auxin distribution changes cell elongation across a shoot or root. Experiments distinguish light detection from signal transmission, and growers use hormone responses in rooting, ripening and weed control.
- [Communities: Interdependence, Competition and Abiotic Factors](https://lightmysky.com/learn/science/communities-interdependence-competition-and-abiotic-factors-mt_su-CNKV8hK): An organism in a community depends on others for food, shelter and reproduction, and competes with them for whatever is scarce. Alongside that sit the non-living conditions of the place, and separating the two kinds of factor is what makes an ecological explanation testable.
- [Human Impact on Ecosystems: Land, Waste and a Warming World](https://lightmysky.com/learn/science/human-impact-on-ecosystems-land-waste-and-a-warming-world-mt_BiYCyohfyI): Growing population and rising standards of living take more land and leave more waste, and both show up in ecosystems as lost habitat and changed conditions. The arguments about what to do are trade-offs between real costs, not a single right answer.
- [Decomposers and the Rate of Decay](https://lightmysky.com/learn/science/decomposers-and-the-rate-of-decay-mt_4152TrzD6A): Bacteria and fungi break dead material down and return carbon to the air and mineral ions such as nitrates to the soil. Decay speeds up with temperature, water and oxygen, which is what a compost heap and a fridge each work on.
- [Fertilisers, Leaching and Eutrophication](https://lightmysky.com/learn/science/fertilisers-leaching-and-eutrophication-mt_9lTF20DWOZ): Nitrate added to a field does not stay in the field, and once it reaches a river it feeds algae rather than crops. The damage is done by the decomposers that follow, because the oxygen they use is the oxygen the fish needed.
- [Fungi: Hyphae, Spores and Digestion Outside the Body](https://lightmysky.com/learn/science/fungi-hyphae-spores-and-digestion-outside-the-body-mt_qfp2nuk1IH): A fungus grows as a network of threads that secretes enzymes into its surroundings and takes back what dissolves, which is why the body plan is all surface. That habit makes fungi the main decomposers on land and, with the same machinery, serious pathogens of plants.
- [Skeletons & Muscles](https://lightmysky.com/learn/science/skeletons-and-muscles-mt_g4YSiOCS8g): Identify that humans and some other animals have skeletons and muscles for support, protection, and movement
- [The Human Skeleton](https://lightmysky.com/learn/science/the-human-skeleton-mt_Qkl46lyris): Describe the structure and four main functions of the human skeleton: support, protection, movement, and production of blood cells in bone marrow
- [Joints, Tendons & Ligaments](https://lightmysky.com/learn/science/joints-tendons-and-ligaments-mt_yefw2CQT4x): Explain biomechanics — the interaction between skeleton and muscles at joints, including the roles of tendons (attach muscle to bone) and ligaments (attach bone to bone)
- [Muscles Work in Pairs](https://lightmysky.com/learn/science/muscles-work-in-pairs-mt_lm0usBAF53): Explain that muscles work in antagonistic pairs — one contracts while the other relaxes — to produce movement, using the bicep and tricep as a key example
- [Organ Systems Vocabulary](https://lightmysky.com/learn/science/organ-systems-vocabulary-mt_K8DJzqbksM): Use technical vocabulary for the major organ systems — organ, organ system, circulatory system, digestive system, respiratory system, skeletal system, muscular system, nutrient, oxygen, carbon dioxide, blood vessel, artery, vein, capillary, enzyme — and describe the function of each system using these terms
- [Human Life Stages](https://lightmysky.com/learn/science/human-life-stages-mt_OSfCeIeBak): Describe the changes as humans develop to old age, including the stages of the human life cycle
- [Structures for Survival](https://lightmysky.com/learn/science/structures-for-survival-mt_8VA40Tumth): Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behaviour, and reproduction
- [The Digestive System](https://lightmysky.com/learn/science/the-digestive-system-mt_Ruk2-lyGPZ): Describe the simple functions of the basic parts of the human digestive system: mouth, oesophagus, stomach, small intestine, large intestine
- [Digestion & Enzymes](https://lightmysky.com/learn/science/digestion-and-enzymes-mt_0NlbulkB5P): Describe the organs of the human digestive system and how food is physically and chemically digested, including the role of enzymes as biological catalysts
- [Gut Bacteria & Digestion](https://lightmysky.com/learn/science/gut-bacteria-and-digestion-mt_fCvmdI6xGO): Explain the role of gut microbiome bacteria in digestion, including breaking down dietary fibre and contributing to a healthy gut environment
- [Enzyme Action and the Active Site](https://lightmysky.com/learn/science/enzyme-action-and-the-active-site-mt__ozLTPNN0H): An enzyme speeds a reaction because its active site has complementary shape and chemical properties for a substrate. Covers specificity, induced fit, and why an enzyme is not used up by the reaction it catalyses.
- [The Digestive System and Testing Food for Nutrients](https://lightmysky.com/learn/science/the-digestive-system-and-testing-food-for-nutrients-mt__mBJCQEqPS): Digestion is a sequence of organs each doing one job to a food molecule too big to absorb, with enzymes and bile doing the chemistry. Simple colour tests let a learner check which nutrient classes are actually present in a sample.
- [Measuring the Rate of an Enzyme Reaction](https://lightmysky.com/learn/science/measuring-the-rate-of-an-enzyme-reaction-mt_Rmz54ICmRC): Calculates rate as amount per unit time, and in a defined colour-change method as 1000 divided by seconds. Describes how temperature and pH change enzyme rate, including the rise to an optimum and the possible irreversible fall after denaturation.
- [Photosynthesis and Limiting Factors](https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih): Light intensity, carbon dioxide concentration and temperature can each limit photosynthesis. At a given set of conditions, the main limiting factor sets the rate. For the lamp model used here, intensity follows an inverse-square relation with distance.
- [Food Security: What Limits Yield and What It Costs to Raise It](https://lightmysky.com/learn/science/food-security-what-limits-yield-and-what-it-costs-to-raise-it-mt_SprRvGuyrK): Every way of getting more food out of the same land moves a cost somewhere else, usually onto soil, water or biodiversity. Working out which limit is actually binding on a given farm is what separates a real answer from a slogan.
- [Respiration: Energy Yield, Oxygen Debt and Fermentation](https://lightmysky.com/learn/science/respiration-energy-yield-oxygen-debt-and-fermentation-mt_mvnCjThdTH): Compare aerobic respiration with lactate formation in muscles and fermentation in yeast. Covers ATP yield, word equations, and the extra oxygen used during recovery after intense exercise.
- [Digestion and Absorption in the Mammalian Gut](https://lightmysky.com/learn/science/digestion-and-absorption-in-the-mammalian-gut-mt_xZ2-3ZClDa): Explain how villi support absorption and how an ATP-powered pump maintains the sodium gradient used for glucose co-transport. Connect villus damage in coeliac disease with reduced nutrient absorption.
- [Enzyme Kinetics: Vmax and the Michaelis Constant](https://lightmysky.com/learn/science/enzyme-kinetics-vmax-and-the-michaelis-constant-mt_ooF8eZ1Gzy): Rate plotted against substrate concentration flattens to a maximum because the active sites become saturated. Vmax and Km are read off that curve and used to compare enzymes.
- [Light-Dependent Reactions in the Thylakoid Membrane](https://lightmysky.com/learn/science/light-dependent-reactions-in-the-thylakoid-membrane-mt_3Ooq3BfmpX): Thylakoid membranes hold pigments that trap light. The light-dependent reactions split water, make ATP, and reduce NADP+ to NADPH, also called reduced NADP. ATP and NADPH then supply energy and reducing power to carbon-fixing reactions.
- [The Calvin Cycle and Carbon Fixation](https://lightmysky.com/learn/science/the-calvin-cycle-and-carbon-fixation-mt_zGOCx9mNrx): Rubisco joins carbon dioxide to RuBP, and the ATP and reduced NADP from the light reactions turn the product into triose phosphate. Most of that triose phosphate is spent regenerating RuBP.
- [Glycolysis and the Link Reaction](https://lightmysky.com/learn/science/glycolysis-and-the-link-reaction-mt_crbadbBvqB): Glucose is split into two pyruvate molecules in the cytoplasm, with a small net ATP gain and no oxygen involved. Pyruvate then enters the mitochondrion and becomes acetyl coenzyme A.
- [Enzyme Inhibition and Metabolic Control](https://lightmysky.com/learn/science/enzyme-inhibition-and-metabolic-control-mt_8VYolkJ_wR): Competitive inhibition raises apparent Km without lowering Vmax. Pure non-competitive inhibition lowers Vmax without changing Km. Reversible end-product inhibition lets accumulated products reduce their own production.
- [The Krebs Cycle and the Reduced Carriers](https://lightmysky.com/learn/science/the-krebs-cycle-and-the-reduced-carriers-mt_eviWcVke2x): Acetyl coenzyme A enters a cycle that releases carbon dioxide and loads electrons onto NAD and FAD. The cycle makes almost no ATP directly; its real output is the reduced carriers.
- [Oxidative Phosphorylation and Chemiosmosis](https://lightmysky.com/learn/science/oxidative-phosphorylation-and-chemiosmosis-mt_1wP3-14Y4V): Electrons from the reduced carriers pass along a chain, and the energy released pumps protons across the inner membrane. Protons flowing back through ATP synthase make most of the cell's ATP.
- [Anaerobic Routes and the ATP Yield Compared](https://lightmysky.com/learn/science/anaerobic-routes-and-the-atp-yield-compared-mt_LBZ4laMfqb): Without oxygen the chain backs up, so cells reduce pyruvate to lactate or to ethanol purely to regenerate NAD. The ATP arithmetic shows how much a cell gives up by doing it.
- [Ecosystem Energy Budgets: GPP, NPP and Transfer Efficiency](https://lightmysky.com/learn/science/ecosystem-energy-budgets-gpp-npp-and-transfer-efficiency-mt_D81CKcOdBI): Gross primary production is what producers capture, net primary production is what remains after their own respiration, and only a small share reaches the next trophic level. The numbers are why food chains stay short.
- [The Nitrogen Cycle and the Microbes That Drive It](https://lightmysky.com/learn/science/the-nitrogen-cycle-and-the-microbes-that-drive-it-mt__K1J47NhWj): Nitrogen moves between air, soil and organisms through fixation, ammonification, nitrification and denitrification, each run by particular bacteria. Unlike energy, the atoms get used again and again.
- [Population Growth Curves and Carrying Capacity](https://lightmysky.com/learn/science/population-growth-curves-and-carrying-capacity-mt_KX6rhHF5kj): In a logistic growth model, population growth slows as resources become limited. Carrying capacity is estimated from a sustained population level. Density-dependent and density-independent effects are distinguished by how their effect per individual changes with crowding.
- [Succession from Pioneer to Climax Community](https://lightmysky.com/learn/science/succession-from-pioneer-to-climax-community-mt_3s3dVLP0Lf): Succession changes a community as organisms arrive, alter conditions and interact. Its path depends on the site and disturbances. Management can hold a meadow or other habitat at an earlier stage.
- [The Circulatory System](https://lightmysky.com/learn/science/the-circulatory-system-mt_BX4D8cCFtQ): Identify and name the main parts of the human circulatory system and describe the functions of the heart, blood vessels, and blood
- [Nutrient Transport in Animals](https://lightmysky.com/learn/science/nutrient-transport-in-animals-mt_YSyjTZfjvv): Describe how nutrients and water are transported within animals, including the role of the circulatory system in delivering nutrients from digestion
- [Heart Structure & Double Circulation](https://lightmysky.com/learn/science/heart-structure-and-double-circulation-mt_TR2oTy9c2M): Describe the structure of the heart (four chambers, valves, coronary arteries) and explain how it pumps deoxygenated blood to the lungs and oxygenated blood to the body in a double circulatory system
- [Diet, Exercise & Lifestyle](https://lightmysky.com/learn/science/diet-exercise-and-lifestyle-mt_2x-EwdBsgl): Recognise the impact of diet, exercise, drugs, and lifestyle on the way human bodies function
- [Effects of Drugs & Alcohol](https://lightmysky.com/learn/science/effects-of-drugs-and-alcohol-mt_2R3xRpYhMa): Explain how psychoactive drugs affect the brain, behaviour and health, including harm from alcohol and tobacco smoke, and distinguish depressant, stimulant and hallucinogen effects.
- [Body Temperature Regulation](https://lightmysky.com/learn/science/body-temperature-regulation-mt_zaXr5wcJD2): Explain how the body detects temperature changes and responds through sweating, shivering, vasodilation and vasoconstriction to regulate core temperature.
- [Differentiation and Stem Cells](https://lightmysky.com/learn/science/differentiation-and-stem-cells-mt_UmLJgmcCjO): An unspecialised cell switches on part of its genes and becomes a cell with a job. Compares embryonic, adult and plant meristem stem cells, with the medical uses and the objections that come with them.
- [Fertilisation and the First Cleavages](https://lightmysky.com/learn/science/fertilisation-and-the-first-cleavages-mt_9BXQsdP8fI): Fertilisation has to admit exactly one sperm and then start a programme of divisions that add no mass. The blocks against a second sperm and the pattern of those early cleavages already differ between animal groups, and both differences matter later.
- [Land Plants: Vascular Tissue and a Life Cycle That Alternates](https://lightmysky.com/learn/science/land-plants-vascular-tissue-and-a-life-cycle-that-alternates-mt_DFtQ2mCZSm): Moving onto land forced plants to solve support, water transport and reproduction without water, and the fossil sequence from mosses to flowering plants is a record of those solutions. Every land plant alternates between a spore-producing and a gamete-producing generation, and which one you notice is what changed across the group.
- [Animal body plans: symmetry, cavities and the deep splits](https://lightmysky.com/learn/science/animal-body-plans-symmetry-cavities-and-the-deep-splits-mt_hEC72cvFQF): Symmetry, embryonic germ layers and body-cavity lining describe animal body plans. Evolutionary placement also uses other anatomical traits and molecular evidence. In the standard introductory animal tree, sea urchins share a more recent ancestor with fish than with clams.
- [Protein Targeting and the Signal Sequence](https://lightmysky.com/learn/science/protein-targeting-and-the-signal-sequence-mt_wVFZq8cZgn): A short stretch of a nuclear encoded growing chain decides where the protein ends up: the endoplasmic reticulum, a mitochondrion, the nucleus or the cytosol. Removing or moving that stretch sends the protein to the wrong compartment.
- [Vesicle Traffic: Coats, Adaptors and Fusion](https://lightmysky.com/learn/science/vesicle-traffic-coats-adaptors-and-fusion-mt_uq8R0bdB_L): Cargo leaves one compartment in a coated bud and arrives at another by fusing with its membrane. Coat proteins choose the cargo, and matched proteins on the two membranes decide which vesicle fuses where.
- [Membrane Lipid Composition, Asymmetry and Fluidity](https://lightmysky.com/learn/science/membrane-lipid-composition-asymmetry-and-fluidity-mt_PIk59MG-gN): The two leaflets of a membrane hold different lipids, and enzymes spend energy to keep them different. Chain length, double bonds and sterol content set how fluid the bilayer is at a given temperature.
- [Ion Channels: Selectivity, Gating and the Evidence from Single Channels](https://lightmysky.com/learn/science/ion-channels-selectivity-gating-and-the-evidence-from-single-channels-mt_2xPzPeXZZ_): A channel passes one ion species far better than another because of the chemistry lining its narrowest point, and it opens in response to voltage, a ligand or a mechanical pull. Recording one channel at a time shows it flicking between full open and shut rather than easing part way.
- [Ligand Binding: Dissociation Constants and Receptor Occupancy](https://lightmysky.com/learn/science/ligand-binding-dissociation-constants-and-receptor-occupancy-mt_i-v79OaM0n): Binding of a ligand to a receptor reaches an equilibrium set by the dissociation constant, and the fraction of receptors occupied follows a saturating curve. A smaller dissociation constant means tighter binding, so half occupancy is reached at a lower concentration.
- [G-Protein-Coupled Receptors and Second Messengers](https://lightmysky.com/learn/science/g-protein-coupled-receptors-and-second-messengers-mt_7ozcs_sUOJ): A bound ligand changes the receptor shape so that it activates a G protein, which switches on an enzyme that floods the cytosol with a small messenger. One bound molecule outside becomes thousands of messenger molecules inside.
- [Plant Hormone Signalling and How a Plant Decides](https://lightmysky.com/learn/science/plant-hormone-signalling-and-how-a-plant-decides-mt_Zg2xpsb-p_): Plant hormones help coordinate growth, development and responses to changing conditions. Their effects depend on concentration, the responding tissue and interactions with other signals. Auxin and cytokinin balance can influence organ formation in tissue culture. Receptor-mediated signalling can change gene expression.
- [Receptor Tyrosine Kinases and Phosphorylation Cascades](https://lightmysky.com/learn/science/receptor-tyrosine-kinases-and-phosphorylation-cascades-mt_EvIwqsLVGA): Growth factor receptors pair up when a ligand binds, then phosphorylate each other on tyrosine residues. Those phosphates become docking sites, and the proteins that dock there start a kinase cascade that reaches the nucleus.
- [Signal Integration: Cross-talk, Feedback and Termination](https://lightmysky.com/learn/science/signal-integration-cross-talk-feedback-and-termination-mt_Io2P-l38Xq): A cell rarely receives one signal at a time, and the same messenger can mean different things depending on what else is active. Feedback loops, phosphatases and receptor removal decide how fast a response stops.
- [Apoptosis: Caspase Cascades and the Decision to Die](https://lightmysky.com/learn/science/apoptosis-caspase-cascades-and-the-decision-to-die-mt_Pi6c9yoT7w): A cell can dismantle itself in an ordered way using a cascade of proteases that are already present but inactive. Death signals from outside and damage signals from inside both converge on the same execution step.
- [Actin Filaments: Polarity, Treadmilling and Cell Shape](https://lightmysky.com/learn/science/actin-filaments-polarity-treadmilling-and-cell-shape-mt_sJlYoA-BnA): Actin filaments have different plus and minus ends. During steady-state treadmilling, plus-end addition balances minus-end loss. Actin assembly near the membrane helps a crawling cell extend its leading edge.
- [Microtubules, Dynamic Instability and the Spindle](https://lightmysky.com/learn/science/microtubules-dynamic-instability-and-the-spindle-mt_RWhMJxOmUu): Microtubules switch between growth and rapid shortening. These changes help spindle microtubules explore space and attach to chromosome kinetochores. Continued dynamics also support attachment correction and chromosome movement.
- [Motor Proteins and Directed Movement Along Tracks](https://lightmysky.com/learn/science/motor-proteins-and-directed-movement-along-tracks-mt_TUTmILr7y0): Myosins, kinesins and dyneins use ATP-dependent cycles to generate movement on polar filaments. Direction depends on the particular motor and the track's orientation. Opposite-direction motors support transport both ways along a track.
- [Junctions, Adhesion and the Extracellular Matrix](https://lightmysky.com/learn/science/junctions-adhesion-and-the-extracellular-matrix-mt_Sjcd3kQUmw): Cells hold onto each other and onto the matrix around them through junctions that are anchored to the cytoskeleton. The matrix is not filler: its stiffness and composition feed back into how the cell behaves.
- [Gastrulation and Laying Down the Body Axes](https://lightmysky.com/learn/science/gastrulation-and-laying-down-the-body-axes-mt_PABfw_4RPs): Gastrulation is where a ball of cells becomes an animal with an inside, an outside and three germ layers, by cells moving rather than dividing. The axes are set at the same time, and grafting experiments showed that one small region can organise a whole second axis.
- [What a Cell Has to Break to Become a Tumour](https://lightmysky.com/learn/science/what-a-cell-has-to-break-to-become-a-tumour-mt_cjg3DtLHQL): Growth control, replicative limits, programmed death, metabolic supply and immune surveillance each constrain a cell, and a tumour has to defeat several of them. This stop treats the hallmark list as a set of constraints rather than a catalogue to memorise.
- [Morphogen Gradients and Positional Information](https://lightmysky.com/learn/science/morphogen-gradients-and-positional-information-mt_EbOK5M7V6Y): A cell can work out where it is from the local concentration of a diffusible signal, and respond by switching on a different set of genes at different thresholds. This is how a smooth gradient produces sharp stripes, and why the same signal means different things in different tissues.
- [Organogenesis and the Model Organisms That Made It Visible](https://lightmysky.com/learn/science/organogenesis-and-the-model-organisms-that-made-it-visible-mt_MXqKNdT519): Organs form by a small repertoire of moves repeated in different places: fold a sheet, make a tube, branch it, then kill the cells in between. Most of what is known came from a handful of organisms chosen because they are transparent, fast, or easy to mutate, and that choice shapes what is known.
- [The Tumour Microenvironment: Stroma, Hypoxia and Immune Exclusion](https://lightmysky.com/learn/science/the-tumour-microenvironment-stroma-hypoxia-and-immune-exclusion-mt_OIrMAjomX_): A tumour is a tissue rather than a bag of cancer cells, and its stroma, blood supply and immune infiltrate change how it grows and what a drug can reach. This stop reads a tumour section as a habitat with its own gradients.
- [Targeted Therapy and the Resistance That Follows It](https://lightmysky.com/learn/science/targeted-therapy-and-the-resistance-that-follows-it-mt_HrU1DfZhGz): A drug aimed at a driver works for as long as the driver is required and the target is unchanged. This stop works through the routes back: mutation of the target, bypass signalling, and selection of a clone that was already present.