GCSE Biology flashcards

About this deck

382 free AQA GCSE Biology flashcards across 8 topics. Every card is a key term and its definition, taken word for word from a published Revise Right lesson, and links back to that lesson so you can read the full notes behind it.

Cell biology

51 cards from 21 lessons. Each term links to the lesson it comes from.

Understanding Cell Types: Eukaryotes vs Prokaryotes

• Eukaryotic cell: A cell with genetic material enclosed in a nucleus. Found in plants, animals, fungi and protists.
• Prokaryotic cell: A cell with genetic material not enclosed in a nucleus. Found in bacteria and archaea.
• Plasmid: Small rings of DNA found in bacterial cells, separate from the main chromosome. Often carry genes for antibiotic resistance.

Setting up sterile cultures and bacterial growth

• Uncontaminated culture: A bacterial culture containing only one type of microorganism, with no unwanted bacteria, fungi, or other microbes present.
• Binary fission: Simple cell division where one bacterial cell splits into two identical daughter cells, occurring as often as every 20 minutes under optimal conditions.

Measuring and calculating bacterial populations

• Colony area calculation: The cross-sectional area of a circular bacterial colony calculated using the formula A = πr², where r is the radius measured from the centre to the edge.
• Standard form: A way of writing numbers as a × 10ⁿ where a is between 1 and 10, and n shows how many places the decimal point has moved.

Cell Differentiation: Animal vs Plant Cells

• Cell differentiation: The process by which unspecialised cells become specialised to perform specific functions through changes in gene expression and cell structure.
• Meristem: Regions of unspecialised plant cells that retain the ability to divide and differentiate throughout the plant's life. Found at root tips, shoot tips, and in stems.

Comparing Animal and Plant Cell Structures

• Nucleus: The control centre of the cell that contains DNA and controls all cell activities
• Cytoplasm: A jelly-like substance where chemical reactions take place and organelles are suspended
• Cell membrane: A partially permeable barrier that controls what substances can enter and leave the cell
• Mitochondria: The powerhouses of the cell where aerobic respiration occurs to release energy
• Ribosomes: Tiny structures that make proteins by joining amino acids together
• Chloroplasts: Green organelles that contain chlorophyll and carry out photosynthesis to make glucose
• Permanent vacuole: A large, fluid-filled sac that stores cell sap and helps maintain the cell's shape
• Cell wall: A rigid outer layer made of cellulose that provides structural support and protection

Structure and Function Relationships in Cells

• Plasmids: Small circular pieces of DNA found in bacterial cells, separate from the main chromosome. Often carry genes for antibiotic resistance or other survival advantages.

Development of Microscopy Techniques

• Light microscope: A microscope that uses visible light and glass lenses to magnify specimens. Maximum useful magnification is about 1500x with resolution of 200 nanometres.
• Electron microscope: A microscope using an electron beam instead of light. Can magnify up to 2 million times with resolution of 0.05 nanometres - 4000 times better than light microscopes.

Magnification Calculations

• Microscopy Units: 1 mm = 10^-3 m, 1 μm = 10^-6 m, 1 nm = 10^-9 m (so 1 mm = 1000 μm and 1 μm = 1000 nm).
• Magnification: The number of times larger an image appears compared with the real object, calculated as image size divided by real size.

The Cell Cycle and Preparation for Division

• Cell Cycle: The series of stages that a cell goes through as it grows and divides to produce two identical daughter cells. The cycle ensures genetic material is copied accurately before division occurs.
• DNA Replication: The process where DNA copies itself to form two identical copies of each chromosome. This happens before mitosis to ensure each daughter cell receives the same genetic information.
• Chromatid: One of two identical copies of a chromosome that are joined together after DNA replication. During mitosis, chromatids separate so each daughter cell gets one copy.
• Mitosis: The stage of the cell cycle where the nucleus divides to produce two identical nuclei, each containing the same number of chromosomes as the parent cell.

Mitosis and Cell Division Process

• Spindle fibres: Protein structures that attach to chromosomes and pull them to opposite ends of the cell during mitosis.

Chromosomes, DNA and Genes

• DNA: The chemical molecule that stores genetic information. Made of two strands twisted into a double helix shape.
• Gene: A section of DNA that codes for one specific characteristic, such as eye colour or blood group.
• Chromosome: A structure made of tightly coiled DNA that carries hundreds or thousands of genes.
• Homologous pair: Two chromosomes that carry the same genes in the same positions, but may have different versions (alleles) of those genes.

What are stem cells and where are they found?

• Stem cell: An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.

Medical uses and applications of stem cells

• Stem cells: Undifferentiated cells that can divide to produce more stem cells or differentiate into specialised cell types. They retain the ability to become any type of cell in the body.
• Therapeutic cloning: The process of creating an embryo with identical genes to the patient, then harvesting stem cells from this embryo. These cells are genetically identical to the patient and won't be rejected.

Stem cells in agriculture and conservation

• Meristem cells: Meristem cells can divide and differentiate into all specialised plant cell types, allowing a whole plant to be regenerated from meristem tissue.
• Disease resistance: Inherited plant characteristic that prevents or reduces damage from pathogens such as bacteria, viruses, or fungi. Often controlled by specific resistance genes.

Understanding Active Transport and Comparing Cell Transport Methods

• Active Transport: The movement of substances from a more dilute solution to a more concentrated solution (against a concentration gradient) using energy from respiration

Active Transport in Action: Plants and Animals

• Root Hair Cells: Elongated plant cells that increase surface area for absorption. They contain many mitochondria to provide energy for active transport of mineral ions.

What is diffusion and what affects its rate?

• Diffusion: The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.
• Concentration gradient: The difference in concentrations between two areas. The steeper the gradient (bigger difference), the faster the rate of diffusion.

Surface area to volume ratio and single-celled organisms

• Surface area to volume ratio: The relationship between an organism's outer surface and its internal space, calculated as surface area ÷ volume. Measured as a ratio (e.g., 6:1) or decimal value.
• Diffusion distance: The maximum distance molecules must travel from the cell surface to reach the centre. In single cells, this equals the radius of the cell.

Exchange surfaces in multicellular organisms

• Large surface area: Having many folded or branched structures to maximise the area available for exchange. Provides more space for molecules to cross simultaneously.
• Thin membrane: A barrier that is only one or two cells thick, providing a short diffusion path. Reduces the time needed for molecules to cross.
• Good blood supply: Dense network of capillaries that maintains concentration gradients by constantly removing or delivering materials. Only applies to animals.
• Ventilation: Movement of air or water across the exchange surface to maintain concentration gradients. Ensures fresh supply of materials and removal of waste products.

Understanding Osmosis

• Osmosis: The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Partially permeable membrane: A membrane that allows some molecules to pass through but not others - water can pass but larger solute molecules cannot
• Osmosis direction: In osmosis, water moves from a dilute solution to a more concentrated solution through a partially permeable membrane.

Measuring and Calculating Water Movement

• Rate of water uptake: The volume of water absorbed by a plant per unit time, typically measured in cm³/min or ml/hour. Calculated by dividing the volume of water taken up by the time period.
• Percentage change in mass: The proportional change in mass of plant tissue expressed as a percentage. Formula: ((final mass - initial mass) / initial mass) × 100. Positive values indicate mass gain, negative values indicate mass loss.

Organisation

44 cards from 14 lessons. Each term links to the lesson it comes from.

From Cells to Organisms

• Cell: The basic structural and functional unit of all living organisms. All cells contain genetic material and can carry out the seven life processes.
• Tissue: A group of cells with similar structure and function working together to perform a specific task. Examples include muscle tissue, nerve tissue, and epithelial tissue.
• Organ: A structure made of different tissues working together to perform a particular function. Each organ contains multiple tissue types that support its main function.
• Organ System: A group of organs working together to perform complex functions in an organism. Examples include the circulatory system, digestive system, and respiratory system.

Components of Blood

• Plasma: The pale yellow liquid component of blood that makes up about 55% of blood volume. Contains water, dissolved nutrients, hormones, antibodies, and waste products.
• Red Blood Cells (Erythrocytes): Biconcave disc-shaped cells packed with haemoglobin protein. They have no nucleus, allowing maximum space for oxygen transport.
• White Blood Cells (Leukocytes): Larger cells with nuclei that defend the body against pathogens. Include phagocytes that engulf bacteria and lymphocytes that produce antibodies.
• Platelets: Small cell fragments without nuclei that help blood clot at injury sites. They stick together and release chemicals to form a plug.

Blood Cell Structure and Function

• Red Blood Cell (Erythrocyte): A biconcave disc-shaped cell specialised for oxygen transport. Contains haemoglobin protein but lacks a nucleus and organelles.
• Phagocyte: A type of white blood cell that engulfs and digests pathogens and cellular debris through phagocytosis.
• Lymphocyte: A type of white blood cell that produces antibodies specific to particular antigens, providing targeted immune responses.
• Platelet (Thrombocyte): Small cell fragments that initiate blood clotting at wound sites. Contain clotting proteins but no nucleus.

Understanding Cancer and Tumour Types

• Cancer: A disease caused by changes in cells that lead to uncontrolled growth and division. These changes occur in the cell's DNA, disrupting normal cell cycle control.
• Benign tumour: A growth of abnormal cells which are contained in one area, usually within a membrane. They do not invade other parts of the body.
• Malignant tumour: Cancerous cells that invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours.
• Secondary tumour: A new tumour that forms when cancer cells from the primary tumour spread to a different part of the body through the bloodstream.

Cancer Risk Factors

• Risk Factor: A factor that increases the likelihood of developing a disease. Can be lifestyle-related or genetic.
• Lifestyle Risk Factor: A behavioural or environmental factor that can be controlled or modified to reduce disease risk.
• Genetic Risk Factor: An inherited factor that increases susceptibility to disease, passed from parents to offspring.

Understanding Coronary Heart Disease and Its Treatments

• Coronary Arteries: Blood vessels that branch from the aorta and supply oxygenated blood directly to the heart muscle tissue. They wrap around the heart's surface like a crown.
• Coronary Heart Disease (CHD): A condition where layers of fatty material build up inside the coronary arteries, narrowing them and reducing blood flow to the heart muscle. This leads to oxygen starvation of heart tissue.
• Stent: A small mesh tube, usually made of metal, that is inserted into a narrowed coronary artery to keep it open and restore normal blood flow to the heart muscle.
• Statins: Medications that reduce blood cholesterol levels by blocking the enzyme that produces cholesterol in the liver. This slows down the rate of fatty material deposit in arteries.

Heart Valve Problems and Heart Failure Solutions

• Heart valve stenosis: A narrowed heart valve cannot open fully, restricting blood flow through the heart.
• Heart valve regurgitation: A leaky heart valve allows blood to flow backwards when it should be closed.
• Heart transplant: A surgical procedure where a diseased heart is replaced with a healthy donor heart to treat end-stage heart failure.
• Artificial heart: A mechanical device that temporarily replaces heart function while patients wait for transplants or to help damaged hearts recover.

Evaluating Cardiovascular Disease Treatments

• Artificial pacemaker: An electronic device implanted under the skin that sends electrical impulses to regulate abnormal heart rhythms.

Understanding Health and Disease Interactions

• Health: Health is the state of physical and mental wellbeing. It's not just the absence of disease - you can be disease-free but still not healthy if you're stressed, malnourished, or mentally unwell.
• Communicable Disease: A disease caused by pathogens (bacteria, viruses, fungi, or parasites) that can be transmitted from one organism to another through direct contact, air, water, or vectors.
• Non-communicable Disease: A disease that cannot be transmitted between organisms. Usually caused by genetic factors, lifestyle choices, environmental factors, or age-related changes.

Plant Tissues and Their Functions

• Epidermal tissue: The protective outer layer of cells that covers all plant surfaces, forming a barrier against water loss and pathogens.
• Palisade mesophyll: Tightly packed cells just below the upper epidermis, containing many chloroplasts for maximum photosynthesis.
• Spongy mesophyll: Loosely arranged cells with air spaces between them, allowing gases to move freely for photosynthesis and respiration.
• Xylem: Dead, hollow cells with thick walls that transport water and mineral ions from roots to leaves in one direction only.
• Phloem: Living cells with perforated end walls that transport dissolved sugars from leaves to all parts of the plant in multiple directions.
• Meristem tissue: Rapidly dividing, unspecialised cells found at growing tips of shoots and roots that produce new cells for plant growth.

The Leaf as a Plant Organ

• Epidermis: The protective outer layer of cells covering both surfaces of the leaf. Acts as a barrier against water loss and pathogens.
• Stomata: Microscopic pores in the leaf epidermis that allow gases to enter and exit. Each stoma is surrounded by two guard cells that control opening and closing.
• Guard cells: Specialised kidney-shaped cells that surround each stoma. Can change shape to open or close the pore, controlling gas exchange and water loss.

Plant Transport System Structure

• Translocation: The movement of dissolved sugars and other organic compounds through phloem tissue from sources (like leaves) to sinks (like roots, fruits, or growing tips).

Transpiration and Water Movement

• Transpiration: The loss of water vapour from plant leaves through stomata, creating a transpiration stream that pulls water up from roots through xylem vessels.

Analysing Plant Transport Data

• Limiting factor: The environmental factor that restricts the rate of a biological process when it is in short supply.
• Validity: Whether an investigation actually measures what it is supposed to measure, without the influence of other variables.

Infection and response

41 cards from 17 lessons. Each term links to the lesson it comes from.

Types of Pathogens and How They Spread

• Pathogen: A microorganism that causes infectious disease. Pathogens may be viruses, bacteria, protists or fungi and can infect plants or animals.
• Virus: A non-living pathogen that can only reproduce inside host cells. Contains genetic material (DNA or RNA) surrounded by a protein coat.
• Bacteria: Single-celled living organisms that can reproduce independently. Some are pathogenic and cause disease by producing toxins or damaging tissues.
• Protist: Single-celled organisms with a nucleus. Some are parasitic pathogens that live inside or on host organisms.
• Fungi: Organisms that can be single-celled (yeasts) or multicellular (moulds). Some cause disease by growing on or in host tissues.
• Direct contact transmission: Pathogens spread through physical contact between infected and uninfected organisms, including touching, sexual contact, or contact with bodily fluids.
• Water transmission: Pathogens spread through contaminated water sources, affecting organisms that drink the water or come into contact with it.
• Air transmission: Pathogens spread through the air in droplets produced by coughing, sneezing, or breathing, or as spores carried by wind.

How Pathogens Cause Disease

• Toxin: A poisonous substance produced by bacteria that damages tissues and causes illness symptoms.
• Host cell: A living cell that provides nutrients and reproduction machinery for viruses to multiply inside.

Preventing the Spread of Disease

• Direct transmission: Pathogens pass directly from one person to another through physical contact, droplets, or bodily fluids
• Indirect transmission: Pathogens spread through contaminated objects, food, water, or vector organisms like mosquitoes
• Herd immunity: When enough people in a population are immune to a disease that it cannot spread effectively, protecting even unvaccinated individuals

How Vaccination Works

• Vaccination: The introduction of small quantities of dead or inactive forms of a pathogen into the body to stimulate white blood cells to produce antibodies without causing disease.
• Memory cells: Specialised white blood cells that remain in the body after vaccination or infection and can rapidly recognise and respond to the same pathogen if encountered again.

Individual and Population Protection Through Vaccination

• Vaccine: A preparation containing antigens from pathogens that stimulates immunity without causing disease. Contains dead, weakened, or parts of disease-causing organisms.

Sources of medicines and their discovery

• Digitalis: A heart medication extracted from foxglove plants that increases the strength of heart contractions and is used to treat heart failure.
• Aspirin: A painkiller and anti-inflammatory drug originally derived from willow bark, now synthetically produced as acetylsalicylic acid.
• Penicillin: The first antibiotic drug, discovered by Alexander Fleming from Penicillium mould, which kills bacteria by preventing them from building cell walls.

Testing new medicines: from laboratory to clinic

• Preclinical testing: Laboratory testing of potential medicines using cells, tissues and live animals to check basic safety and effectiveness before human trials.

Clinical trials and finding the right dose

• Phase I trial: The first stage of human testing where very small doses are given to check for safety and side effects
• Placebo effect: The improvement in symptoms that occurs because a patient believes they are receiving treatment

What are monoclonal antibodies and their key properties

• Monoclonal antibodies: Identical antibodies produced from a single clone of cells that are specific to one binding site on one protein antigen. They can target specific chemicals or specific cells in the body.
• Hybridoma cell: A cell created by fusing a B-lymphocyte with a tumour cell, combining the ability to produce specific antibodies with unlimited cell division.
• Antigen specificity: The property that allows antibodies to bind to only one specific binding site on one particular antigen, determined by the complementary shape between antibody and antigen.

The hybridoma technique for producing monoclonal antibodies

• Screening (hybridoma): The process of testing many hybridoma clones to identify the clone that produces the required monoclonal antibody with the correct specificity.

Diagnostic and Laboratory Applications of Monoclonal Antibodies

• ELISA test: Enzyme-Linked Immunosorbent Assay - a laboratory technique using monoclonal antibodies to measure specific substances in blood samples. The antibodies are linked to enzymes that produce colour changes for detection.

Therapeutic Uses and Limitations of Monoclonal Antibodies

• Therapeutic monoclonal antibodies: Monoclonal antibodies designed to treat diseases by binding to specific antigens on target cells, such as cancer cells or pathogens.

Physical Defence Responses in Plants

• Cellulose cell wall: A rigid structural barrier made of cellulose fibres that surrounds every plant cell. Acts as the primary physical defence against pathogen invasion and provides structural support.
• Waxy cuticle: A waterproof waxy layer covering the outer surface of leaves and stems. Prevents water loss and creates a hydrophobic barrier that most pathogens cannot penetrate.
• Mechanical adaptations: Physical structures such as thorns, spines, and hairs that deter herbivores from feeding on plant tissues. Reduce the risk of wounds that could become entry points for pathogens.

Chemical Defence Responses in Plants

• Antibacterial chemicals: Compounds produced by plants that kill bacteria or prevent their growth. Released in response to infection to stop disease spreading through plant tissues.
• Plant toxins: Poisonous chemicals stored in plant tissues that harm or deter herbivores. Can cause illness, bad taste, or digestive problems in animals that eat the plant.
• Chemical mimicry: The production of chemicals that copy the scent, taste, or chemical signals of dangerous or unpalatable organisms to trick animals into avoiding the plant.

Recognising Plant Disease Symptoms

• Stunted growth: Reduced plant size and development compared to healthy plants of the same age. The plant appears smaller, with shorter stems and fewer leaves than expected.
• Tobacco mosaic virus (TMV): A viral disease that causes distinctive mosaic patterns of light and dark green patches on leaves. Reduces photosynthesis efficiency and causes stunted growth in infected plants.
• Black spot: A fungal disease that causes dark, circular spots on leaves, typically with yellow halos. Severely infected leaves turn yellow and drop off, weakening the plant.

Methods for Identifying Plant Diseases

• Reference identification: Comparing observed plant symptoms with photographs and descriptions in gardening manuals or reputable websites to make a preliminary diagnosis
• Monoclonal antibody testing kit: A rapid diagnostic tool containing identical antibodies that bind specifically to antigens from particular plant pathogens, producing a visible colour change

Mineral Deficiencies in Plants

• Nitrate ions: Essential mineral ions (NO₃⁻) that plants absorb through their roots and use to make proteins for growth
• Chlorosis: Yellowing of plant leaves caused by insufficient chlorophyll production, most commonly due to magnesium deficiency

Bioenergetics

37 cards from 12 lessons. Each term links to the lesson it comes from.

The Photosynthesis Equation and Chemical Symbols

• Word equation for photosynthesis: carbon dioxide + water → glucose + oxygen (in the presence of light)
• CO₂ (Carbon dioxide): One carbon atom bonded to two oxygen atoms. A gas that plants absorb from the atmosphere through stomata.
• H₂O (Water): Two hydrogen atoms bonded to one oxygen atom. Absorbed by plant roots from the soil.
• C₆H₁₂O₆ (Glucose): Six carbon, twelve hydrogen, and six oxygen atoms. The sugar molecule plants make and store as starch.
• O₂ (Oxygen): Two oxygen atoms bonded together. The gas released by plants as a waste product of photosynthesis.
• Endothermic reaction: A chemical reaction that takes in energy from the surroundings. The products have more energy than the reactants.

How Plants Use Glucose for Energy and Storage

• Respiration in plants: The process where glucose is broken down with oxygen to release energy for cellular processes.
• Starch: A large, insoluble polymer made from many glucose molecules joined together. Used for long-term energy storage in plants.
• Plant lipids: Fats and oils produced by converting glucose, providing concentrated energy storage especially in seeds and fruits.

Building Plant Structures with Glucose

• Cellulose: A structural carbohydrate polymer made from glucose molecules that strengthens plant cell walls
• Amino acids: Building blocks of proteins formed when plants combine glucose with nitrate ions from soil

Measuring and Graphing Photosynthesis Rates

• Rate of photosynthesis: The speed at which photosynthesis occurs, measured as the volume of oxygen produced or carbon dioxide used per unit time. Typical units: cm³/min or bubbles per minute.

What is Metabolism?

• Metabolism: The sum of all chemical reactions that occur in a cell or organism. The energy from respiration is used for the continual enzyme-controlled processes of metabolism.
• Building reactions: Reactions that build larger molecules from smaller ones.
• Breakdown reactions: Reactions that break down larger molecules into smaller ones.
• Respiration: The process that releases energy from glucose (and other molecules) to power metabolic reactions. Occurs in mitochondria and requires oxygen for maximum efficiency.

Building Large Molecules from Small Ones

• Joining molecules together: A reaction that joins small molecules together to make larger molecules.
• Glycogen: A storage polymer made from glucose monomers with extensive branching. Found in animal cells, particularly liver and muscle, for rapid energy release.
• Triglyceride: A lipid molecule formed when one glycerol molecule combines with three fatty acid molecules. The main form of stored fat in organisms.

Breaking Down Molecules and Building Blocks

• Building blocks: Small molecules that join together to form larger biological molecules. Sugars build carbohydrates, amino acids build proteins, fatty acids and glycerol build lipids.
• Deamination: The removal of amino groups from excess amino acids in the liver. The amino group forms ammonia (NH₃), which is toxic and must be converted to urea for safe excretion.
• Carbohydrate building blocks: Simple sugars (monosaccharides) like glucose, fructose and galactose. These join together to form complex carbohydrates like starch and glycogen.
• Protein building blocks: Amino acids (20 different types). These join in specific sequences to form proteins with unique shapes and functions.
• Lipid building blocks: Fatty acids and glycerol. Three fatty acids join to one glycerol molecule to form a triglyceride (fat or oil).
• Synthesis: The process of building large molecules from smaller building blocks. Requires energy input (endergonic reaction). Examples: glucose → starch, amino acids → proteins.
• Breakdown: The process of breaking large molecules into smaller building blocks. Releases energy (exergonic reaction). Examples: starch → glucose, proteins → amino acids.

Introduction to Cellular Respiration

• Cellular Respiration: An exothermic reaction that occurs continuously in living cells to transfer energy from glucose for life processes
• Aerobic Respiration: Cellular respiration that uses oxygen to completely break down glucose, transferring maximum energy
• Anaerobic Respiration: Cellular respiration that occurs without oxygen, transferring less energy than aerobic respiration
• Exothermic Reaction: A chemical reaction that releases energy to the surroundings, usually as heat

Aerobic Respiration

• Chemical Symbols in Respiration: C₆H₁₂O₆ (glucose), O₂ (oxygen), CO₂ (carbon dioxide), H₂O (water)

Anaerobic Respiration and Fermentation

• Fermentation: Anaerobic respiration in yeast cells that produces ethanol and carbon dioxide, used commercially in brewing and baking

How the Body Responds to Exercise

• Heart Rate: The number of heartbeats per minute, measured in beats per minute (bpm). Increases during exercise to pump more oxygenated blood to working muscles.
• Breathing Rate: The number of breaths taken per minute, measured in breaths per minute. Increases during exercise to take in more oxygen and remove more carbon dioxide.
• Breath Volume: The amount of air breathed in or out in one breath, measured in litres (L). Increases during exercise to maximise oxygen intake per breath.

Anaerobic Respiration and Recovery

• Lactic acid: A toxic waste product formed during anaerobic respiration. It accumulates in muscle cells and causes the burning sensation during intense exercise
• Oxygen debt: The amount of extra oxygen the body needs after exercise to convert accumulated lactic acid back into glucose in the liver

Homeostasis and response

64 cards from 22 lessons. Each term links to the lesson it comes from.

What is Homeostasis and Why is it Important?

• Homeostasis: The regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• Optimum conditions: The ideal internal environment that allows enzymes and cells to function at their maximum efficiency
• Negative feedback: A control mechanism that detects changes from the optimum and triggers responses to counteract those changes

How Control Systems Work in Homeostasis

• Receptor: A cell that detects stimuli (changes in the environment) and converts them into electrical impulses.
• Coordination centre: An organ that receives and processes information from receptors, such as the brain, spinal cord and pancreas.
• Effector: A muscle or gland that brings about responses to restore optimum levels when stimulated by the nervous system.

Structure and Functions of the Brain

• Cerebral cortex: The wrinkled outer layer of the brain responsible for consciousness, intelligence, memory, language and voluntary movement. It's what makes you 'you'.
• Cerebellum: The 'little brain' at the back that controls balance, posture, muscle coordination and fine motor skills. Think of it as your body's autopilot for movement.
• Medulla: The brain stem region that controls vital unconscious functions including breathing rate, heart rate and blood pressure. It keeps you alive without you thinking about it.

Investigating and Treating Brain Disorders

• Brain lesion studies: Research method that examines patients with brain damage to understand which brain regions control specific functions. Used when natural brain damage provides insights into normal brain function.
• Electrical stimulation: A technique where small electrical currents are applied to specific brain regions to observe their function. Used during brain surgery to map critical areas.
• MRI scanning: Magnetic Resonance Imaging - a non-invasive technique that uses magnetic fields to create detailed images of brain structure and activity. Used when doctors need to see inside the brain without surgery.

Structure of the Eye

• Sense organ: A collection of receptor cells responding to specific stimuli, connected to the nervous system via sensory neurones.
• Sclera: The tough, white outer layer of the eye that maintains the eye's shape and protects the delicate inner structures.
• Cornea: The transparent structure at the front of the eye that refracts light as it enters.
• Iris: The coloured part of the eye containing muscles that control the size of the pupil.
• Lens: A transparent, flexible structure that fine-tunes the focusing of light onto the retina by changing shape.
• Ciliary muscles: Ring-shaped muscles that control the shape of the lens during accommodation.
• Suspensory ligaments: Tough fibres that connect the ciliary muscles to the lens and transmit the force needed to change lens shape.
• Retina: The light-sensitive layer at the back of the eye containing receptor cells (rods and cones) that detect light intensity and colour.
• Optic nerve: The bundle of sensory neurones that carries electrical impulses from the retina to the brain.

Accommodation and Light Adaptation (Part 1/2)

• Accommodation: The process of changing the shape of the lens to focus on near or distant objects by adjusting the curvature of the lens.
• Light adaptation: The process by which the eye adjusts to changes in light intensity, particularly when moving from bright to dim conditions.

Accommodation and Light Adaptation (Part 2/2)

• Distant vision accommodation: The process where ciliary muscles relax, suspensory ligaments pull tight, and the lens becomes thinner and less curved to focus parallel light rays from distant objects onto the retina
• Myopia (Short-sightedness): A vision defect where distant objects appear blurred because light focuses in front of the retina, usually due to an eyeball that's too long or a lens that's too curved

Vision Problems and Corrections

• Hyperopia (Long-sightedness): A vision defect where near objects appear blurry because light rays would focus behind the retina if extended. Distant objects can be seen more clearly.

Temperature Detection and Control

• Thermoregulatory centre: A region in the brain that monitors and controls body temperature.
• Temperature receptors: Specialised sensory cells in the skin that detect temperature changes and send nervous impulses to the thermoregulatory centre via sensory neurons.

Temperature Regulation Mechanisms

• Vasodilation: The widening of blood vessels (arterioles) near the skin surface, allowing more warm blood to flow close to the skin where heat can be lost to the environment.
• Vasoconstriction: The narrowing of blood vessels near the skin surface, reducing blood flow to the skin and minimising heat loss to the environment.

Adrenaline: The Fight or Flight Hormone

• Adrenaline: A hormone produced by the adrenal glands in times of fear or stress. It increases heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'flight or fight'.

Thyroxine: Metabolism and Feedback Control

• Thyroxine: A hormone produced by the thyroid gland that controls basal metabolic rate and is important for growth and development.
• Basal Metabolic Rate (BMR): The minimum rate of energy expenditure needed to maintain basic body functions at rest, measured in kilojoules per day.

Hormonal methods of contraception

• Hormonal contraception: Methods of preventing pregnancy that use synthetic hormones to disrupt the normal menstrual cycle by inhibiting egg maturation, ovulation, or both.
• FSH inhibition: The suppression of follicle stimulating hormone production by the pituitary gland, which prevents eggs from maturing in the ovaries.
• Progesterone contraceptives: Synthetic progesterone hormones delivered via injection, implant, or skin patch that inhibit egg maturation and release for months or years.

Non-hormonal methods of contraception

• Condoms: Thin latex or polyurethane sheaths that cover the penis (male condoms) or line the vagina (female condoms) to prevent sperm entering the reproductive tract.
• Diaphragm: A dome-shaped rubber cup that covers the cervix to block sperm from entering the uterus, usually used with spermicide.
• Spermicides: Chemical agents containing nonoxynol-9 or other compounds that kill or disable sperm, preventing them from swimming to fertilise an egg.
• Intrauterine Device (IUD): A T-shaped device inserted into the uterus that prevents implantation of embryos. Copper IUDs release copper ions toxic to sperm and eggs.
• Vasectomy (Male Sterilisation): Surgical cutting or blocking of the vas deferens tubes to prevent sperm from mixing with semen during ejaculation.
• Tubal Ligation (Female Sterilisation): Surgical cutting, blocking, or removal of sections of the fallopian tubes to prevent eggs from reaching the uterus and sperm from reaching eggs.

Evaluating contraceptive methods

• Combined pill: Contains synthetic oestrogen and progesterone that prevent ovulation by inhibiting FSH and LH release from the pituitary gland
• Progesterone-only pill: Contains only synthetic progesterone that thickens cervical mucus and sometimes prevents ovulation
• Barrier methods: Physical contraceptives that prevent sperm from reaching the egg, including condoms, diaphragms, and cervical caps

Male and Female Reproductive Hormones

• Secondary sex characteristics: Physical features that develop during puberty but are not directly involved in reproduction. Examples include deepening voice, body hair growth, breast development, and changes in body shape.
• Oestrogen: The main female reproductive hormone produced in the ovary. Controls egg maturation, triggers ovulation, and causes female secondary sex characteristics to develop.
• Ovulation: The release of a mature egg from the ovary, occurring approximately every 28 days in the menstrual cycle. Triggered by hormonal changes including oestrogen.
• Testosterone: The main male reproductive hormone produced by the testes. Stimulates sperm production and causes male secondary sex characteristics including voice deepening, muscle development, and facial hair growth.

The Menstrual Cycle and Hormone Control

• Follicle Stimulating Hormone (FSH): Hormone released by the pituitary gland that causes maturation of an egg in the ovary. Levels are highest at the start of the cycle.
• Luteinising Hormone (LH): Hormone that stimulates the release of the mature egg from the ovary (ovulation). Shows a dramatic surge around day 14 of a 28-day cycle.
• Progesterone: Hormone produced by the corpus luteum (remains of the follicle after ovulation) that maintains the thick uterine lining for potential implantation.

Introduction to the Endocrine System

• Endocrine System: A collection of glands that secrete hormones directly into the bloodstream to control body functions. These glands have no ducts - they release hormones straight into blood vessels.
• Hormone: A chemical messenger secreted by endocrine glands that travels in blood to target organs where it produces a specific effect. Hormones are highly specific - each one has particular target organs.
• Pituitary Gland: The 'master gland' located in the brain that controls other endocrine glands by releasing regulatory hormones. It responds to body conditions and coordinates the entire endocrine system.

Plant Hormones in Agriculture and Horticulture

• Selective Herbicide: A weed killer that targets specific plant types (usually broad-leaved weeds) while leaving crops like grass unharmed, often using synthetic auxins at precise concentrations.
• Seed Dormancy: A state where viable seeds delay germination even when environmental conditions appear suitable, broken by specific triggers including gibberellins.

Plant Hormones in Food Production

• Auxins: Plant hormones that promote cell elongation and control fruit development. Naturally produced in growing tips and developing fruits.
• Ethene: A gaseous plant hormone that triggers fruit ripening. Controls the breakdown of chlorophyll, softening of cell walls, and sugar production in fruits.

Plant Hormones and Growth Responses

• Plant hormones: Chemical messengers produced in small quantities that coordinate and control growth and responses to environmental stimuli in plants.
• Auxin: A plant hormone that promotes cell elongation by making cell walls more flexible, allowing cells to absorb water and grow longer.
• Phototropism: The growth response of plants to light direction. Shoots show positive phototropism (grow towards light), whilst roots show negative phototropism (grow away from light).
• Gravitropism: The growth response of plants to gravity. Shoots show negative gravitropism (grow away from gravity/upwards), whilst roots show positive gravitropism (grow towards gravity/downwards).

Gibberellins and Ethene in Plant Development

• Gibberellins: Plant hormones that initiate seed germination and promote stem elongation. They break seed dormancy by activating enzymes that break down stored food reserves.

Inheritance, variation and evolution

62 cards from 25 lessons. Each term links to the lesson it comes from.

DNA Structure and the Genome

• Genome: The entire genetic material of an organism. The human genome contains all the DNA found in human chromosomes.

Applications of Genome Research

• Disease gene mapping: The process of identifying specific genes or DNA regions that increase the risk of developing particular diseases

Genetic vocabulary and basic inheritance (Part 1/2)

• Gamete: A reproductive cell (sperm or egg) that contains half the normal number of chromosomes
• Allele: Different versions of the same gene that control the same characteristic but may produce different traits
• Dominant: An allele that is expressed in the phenotype even when only one copy is present, represented by a capital letter
• Recessive: An allele that is only expressed in the phenotype when two copies are present, represented by a lowercase letter
• Homozygous: Having two identical alleles for a particular gene (e.g., BB or bb)
• Heterozygous: Having two different alleles for a particular gene (e.g., Bb)
• Genotype: The combination of alleles an organism has for a particular gene, written using letters (e.g., Bb)
• Phenotype: The observable characteristic that results from an organism's genotype (e.g., brown eyes)

Genetic vocabulary and basic inheritance (Part 2/2)

• Dominant allele: An allele that is always expressed in the phenotype, even if only one copy is present. Represented by a capital letter (e.g., B for brown fur).
• Recessive allele: An allele that is only expressed if two copies are present (no dominant allele present). Represented by a lowercase letter (e.g., b for white fur).

Multiple gene inheritance

• Polygenic inheritance: The inheritance pattern where multiple genes contribute to a single characteristic, creating continuous variation rather than distinct categories.
• Continuous variation: Variation that shows a range of phenotypes between two extremes, typically forming a bell-shaped (normal) distribution when plotted.
• Phenotypic plasticity: The ability of a genotype to produce different phenotypes in response to different environmental conditions.

Gametes in Sexual Reproduction

• Sperm cell: The male gamete in animals. Small, mobile cell with a tail (flagellum) for swimming to reach the egg cell.
• Egg cell (ovum): The female gamete in animals. Large cell containing nutrients and cytoplasm needed for early embryo development.
• Pollen grain: Structure containing the male gametes in flowering plants. Transferred from anther to stigma during pollination.
• Ovule: Structure in flowering plants containing the female gamete (egg cell). Found inside the ovary of the flower.

Sexual vs Asexual Reproduction and Cell Division

• Sexual reproduction: Reproduction involving two parents where male and female gametes fuse to form offspring with mixed genetic information
• Asexual reproduction: Reproduction involving only one parent with no fusion of gametes, producing genetically identical offspring (clones)
• Meiosis: Cell division that produces four genetically different haploid gametes from one diploid parent cell. Used only for sexual reproduction

The Process of Genetic Engineering

• Genetic Engineering: A process that involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
• Enzymes: Biological catalysts that speed up chemical reactions. In genetic engineering, specific enzymes cut DNA at precise locations
• Vector: A carrier molecule used to transfer genes into target cells, usually a bacterial plasmid or virus

Applications of Genetic Engineering

• GM Crops: Genetically modified crops that have had their genes altered to improve characteristics like disease resistance, herbicide tolerance, or nutritional content.
• Gene Therapy: The experimental technique of introducing genetic material into a patient's cells to treat inherited disorders by correcting defective genes.

What is Evolution?

• Evolution: A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.
• Natural Selection: The process by which organisms with characteristics that make them better adapted to their environment are more likely to survive and reproduce successfully, passing these advantageous characteristics to their offspring.
• Adaptation: A characteristic that increases an organism's chance of survival and reproduction in its environment, developed through natural selection.

How Evolution Works Through Natural Selection

• Variation: Differences in characteristics between individuals of the same species, caused by genetic and environmental factors.
• Selection Pressure: Environmental factors that affect an organism's ability to survive and reproduce, such as predation, disease, or climate change.

Formation of New Species

• Species: A group of organisms that can interbreed to produce fertile offspring. Members of the same species share similar characteristics and can pass on their genes to the next generation.
• Cannot interbreed: When populations of the same species become separated and can no longer interbreed to produce fertile offspring. This can happen due to geographical barriers (like rivers or mountains), behavioural differences, or genetic changes.
• Speciation: The evolutionary process by which populations evolve to become distinct species. This occurs when populations become so different that they can no longer interbreed to produce fertile offspring.

Animal Cloning Techniques

• Animal Cloning: The process of creating genetically identical animals using scientific techniques that bypass normal sexual reproduction.
• Nuclear Transfer: A cloning method where the nucleus from an adult body cell is inserted into an egg cell that has had its nucleus removed.
• Embryo Transplant: A cloning method where an early embryo is split or transferred so genetically identical offspring can develop.

Plant Cloning Methods

• Plant cloning: Asexual reproduction method that produces genetically identical offspring from a single parent plant. Used to preserve desirable characteristics without genetic variation.
• Tissue culture: Laboratory technique using small groups of plant cells to grow identical new plants in sterile conditions. Requires nutrient medium and controlled environment.
• Cuttings: Traditional method of plant cloning where sections of stem, leaf, or root are removed from parent plant and grown into new individuals. Relies on plant's natural ability to regenerate.

Mendel's Revolutionary Discovery

• Controlled Cross-Breeding: The deliberate mating of organisms with specific traits to study inheritance patterns. Mendel prevented natural pollination and chose which plants bred together.

From Chromosomes to Gene Theory

• Cell Division: The process by which one cell splits into two or more daughter cells, involving the precise distribution of chromosomes

What are fossils and how are they formed?

• Fossil: The preserved remains or traces of organisms that lived millions of years ago, found in rocks.
• Mineralisation: A fossilisation process where minerals gradually replace original organic material.
• Trace Fossil: Evidence of an organism’s activity, such as footprints, burrows, or faeces, rather than body remains.

Fossils as evidence for evolution

• Transitional fossil: Fossil showing intermediate characteristics between two different groups of organisms. Provides evidence for evolutionary change from one form to another.

Darwin and Wallace: Developing the Theory of Evolution

• Scientific Priority: The principle that credit for a scientific discovery goes to the person who first publishes the idea, ensuring fair recognition in the scientific community

Wallace's Contributions and the Impact on Biology

• Warning colouration: Bright colours or patterns displayed by animals to warn predators that they are dangerous, poisonous, or unpalatable. Used as a defence mechanism to avoid predation.

The Process of Speciation

• Geographical isolation: Physical separation of populations by geographical barriers such as mountains, rivers, or oceans that prevent interbreeding.

Darwin's Theory of Natural Selection

• Inheritance: The passing of characteristics from parents to offspring through genes. Only inherited traits can be affected by natural selection.

The Three-Domain System

• Three-Domain System: A classification system developed by Carl Woese that divides all life into three domains based on cellular structure and biochemical analysis: Archaea, Bacteria, and Eukaryota.
• Archaea: Single-celled organisms without a nucleus (prokaryotic) that are genetically and biochemically distinct from bacteria. Often called 'primitive bacteria' because they can survive in extreme environments similar to early Earth conditions.
• Eukaryota: Organisms whose cells contain a membrane-bound nucleus and organelles. This domain includes four kingdoms: protists (single-celled eukaryotes), fungi, plants, and animals.

The Linnaean Classification System

• Kingdom: The largest group in classification, containing organisms with fundamental similarities. Examples include Animal Kingdom and Plant Kingdom.
• Phylum: A major group within a kingdom, containing organisms with similar body plans. Example: Chordata (animals with backbones).
• Class: A group within a phylum, containing organisms with similar characteristics. Example: Mammalia (animals that produce milk).
• Order: A group within a class, containing organisms with similar lifestyles or structures. Example: Carnivora (meat-eating mammals).
• Family: A group within an order, containing closely related organisms. Example: Felidae (cat family).
• Genus: A group within a family, containing very similar organisms. Example: Panthera (big cats).

Evolution of Classification and Evolutionary Trees

• Traditional classification: Grouping organisms based on observable physical characteristics and behaviour patterns
• Evolutionary tree: A branching diagram that shows the evolutionary relationships between different species or groups, with branch points representing common ancestors

Ecology

78 cards from 34 lessons. Each term links to the lesson it comes from.

Understanding Ecosystems and Their Organisation

• Ecosystem: The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.
• Biotic factors: Living components of an ecosystem including all organisms such as plants, animals, fungi and microorganisms.
• Abiotic factors: Non-living components of an ecosystem including temperature, light intensity, moisture levels, soil pH and mineral content.

Competition and Survival in Communities

• Competition: The struggle between organisms for the same limited resources in a habitat. Occurs when resources are not abundant enough for all organisms.

Interdependence and Community Stability

• Interdependence: The way species in a community depend on each other for survival needs like food, shelter, pollination and seed dispersal. If one species is removed, it affects the whole community.
• Stable Community: An ecological community where all species and environmental factors are in balance so that population sizes remain fairly constant over time.

Types of Adaptations

• Structural Adaptations: Physical features of an organism that help it survive in its environment. These include body shape, size, colour, and specialised organs.
• Behavioural Adaptations: Actions or behaviours that help an organism survive. These are learned or instinctive responses to environmental challenges.
• Functional Adaptations: Internal processes that help an organism survive. These include how the body produces energy, removes waste, or maintains temperature.

Extremophiles and Extreme Environments

• Extremophiles: Organisms that live and thrive in environments with extreme conditions such as very high or low temperatures, high pressure, high salt concentration, or extreme pH levels. They are mostly bacteria and archaea.
• Deep sea vents: Underwater hot springs on the ocean floor where superheated water rich in minerals erupts from the Earth's crust. They create unique ecosystems in the deep ocean.

Living Factors Affecting Communities

• Interspecific competition: Competition between different species for the same limited resources such as food, territory, or nesting sites. Often results in competitive exclusion where one species outcompetes another.

Physical Abiotic Factors in Ecosystems

• Light intensity: The amount of light energy reaching a particular area per unit time, measured in lux. Directly affects the rate of photosynthesis in plants.

Environmental Factors Affecting Ecosystems

• Tolerance range: The range of environmental conditions within which an organism can survive and reproduce successfully. Outside this range, the organism experiences stress or death.

Evaluating Environmental Change Impact

• Environmental change: Any alteration in physical or chemical conditions that affects where organisms can survive and reproduce in an ecosystem
• Limiting factors: Environmental conditions that restrict the growth, abundance, or distribution of organisms in an ecosystem

Working with ecological data

• Mean (Arithmetic Average): The sum of all values divided by the number of values. Formula: Mean = Σx ÷ n, where Σx is the sum of all values and n is the number of values.
• Mode: The value that appears most frequently in a data set. A data set can have no mode, one mode, or multiple modes.
• Median: The middle value when all values are arranged in ascending order. For even numbers of values, it's the mean of the two middle values.

Producers and feeding relationships

• Producer: An organism that synthesises molecules using energy from the environment, usually through photosynthesis. Producers convert light energy into chemical energy stored in glucose.
• Food Chain: A diagram showing the feeding relationships between organisms, with arrows indicating the direction of energy flow from one organism to the next.
• Primary Consumer: The first consumer in a food chain - organisms that eat producers directly. Always herbivores in terrestrial ecosystems.
• Secondary Consumer: Organisms that eat primary consumers. Usually carnivores, but can be omnivores that eat both plants and animals.
• Tertiary Consumer: Organisms that eat secondary consumers. Often apex predators with few or no natural predators as adults.

Studying ecosystems and predator-prey relationships

• Quadrat: A square frame, usually 1m × 1m, placed randomly on the ground to sample organisms in a specific area. Used to estimate population density and percentage cover of species.
• Transect: A line or belt across a habitat used to study how species distribution changes along an environmental gradient such as distance from water, altitude, or soil pH.
• Predator: A consumer that kills and eats other animals (prey). Examples include lions hunting zebras, spiders catching flies, and hawks hunting mice.
• Prey: Animals that are killed and eaten by predators. They are often herbivores or smaller carnivores that form the food source for larger predators.

Factors Affecting Decomposition and Rate Calculations

• Decomposition: The breakdown of dead organic matter by microorganisms such as bacteria and fungi. Measured as mass lost per unit time.

Practical Applications of Decomposition

• Decomposer organisms: Bacteria and fungi that break down dead organic matter, releasing nutrients back into the ecosystem. They are essential for nutrient cycling.
• Aerobic decay: Decomposition in the presence of oxygen, producing carbon dioxide, water, and heat as waste products. Fast and efficient.
• Anaerobic decay: Decomposition without oxygen, producing methane, carbon dioxide, and other gases. Slower process with different end products.

Material cycling in ecosystems

• Material cycling: The continuous movement of chemical elements and compounds between living organisms and the non-living environment in an ecosystem. These materials include carbon, nitrogen, phosphorus, and water.
• Biotic components: The living parts of an ecosystem including all plants, animals, fungi, and microorganisms. These organisms take in materials from their environment and release materials back when they respire, excrete, or die.
• Abiotic components: The non-living parts of an ecosystem including air, water, soil, rocks, and minerals. These provide the raw materials that living organisms need and act as reservoirs where materials are stored.
• Decomposers: Organisms such as bacteria and fungi that break down dead organic matter and waste products through the process of decomposition. They release nutrients like nitrates, phosphates, and carbon dioxide back into the soil, water, and air.

Human Impacts on Biodiversity

• Habitat destruction: The process by which natural habitats are damaged or eliminated, making them unable to support the species that live there.

Conservation Programmes and Habitat Protection

• Captive Breeding Programme: A conservation strategy where endangered species are bred in controlled environments (zoos, wildlife centres) to increase population size and variation within a species before potential reintroduction to the wild.
• Field Margins: Uncultivated strips of land around field edges, typically 2-6 metres wide, left to develop natural vegetation that provides wildlife habitat.

Global and Local Environmental Solutions

• Deforestation: The permanent removal of forests and trees from land, typically for agriculture or development. Reduces biodiversity and increases atmospheric CO₂ levels.
• Recycling: The process of converting waste materials into new products to prevent waste and reduce consumption of raw materials.

What is Biodiversity and Why Does it Matter?

• Biodiversity: The variety of all the different species of organisms on Earth, or within an ecosystem. This includes plants, animals, fungi, bacteria, and all other living things.
• Ecosystem Stability: The ability of an ecosystem to maintain its structure and function over time, resisting changes and recovering from disturbances.

Human Impact on Biodiversity

• Conservation: The protection and management of natural resources and ecosystems to prevent extinction and maintain biodiversity.
• Balancing human needs and conservation: Development that meets current needs while protecting the environment.

How Human Activities Reduce Land for Wildlife

• Building development: The construction of houses, roads, factories and infrastructure that permanently converts natural habitats into urban areas.
• Quarrying: The extraction of stone, sand, gravel and minerals from the ground, creating large excavated areas that destroy existing ecosystems.
• Intensive farming: Agricultural practices that convert natural habitats into crop fields and livestock pastures, often using pesticides and fertilisers that affect surrounding ecosystems.
• Waste disposal: The dumping of household, industrial and agricultural waste on land, contaminating soil and water while making areas unsuitable for wildlife.
• Peat formation: The accumulation of partially decomposed plant material in waterlogged, acidic conditions where oxygen levels are too low for complete decay.

Understanding Global Warming and Its Biological Impact

• Carbon Dioxide (CO₂): A greenhouse gas produced by burning fossil fuels, deforestation, and respiration. Current atmospheric levels are the highest in 3 million years.
• Methane (CH₄): A greenhouse gas about 25 times more potent than CO₂ over a 100-year period, produced by livestock, rice farming, and landfill sites. Levels have tripled since pre-industrial times.

Types and Sources of Pollution

• Pollution: The contamination of the environment with harmful substances that damage ecosystems and human health. Can occur in water, air or on land.
• Eutrophication: The process where excess nutrients in water cause algae blooms, leading to oxygen depletion and ecosystem damage. Results in fish kills and loss of biodiversity.
• Acid rain: Rain that has become acidic (pH below 5.6) due to air pollution from sulfur dioxide and nitrogen oxides. Damages buildings, forests and aquatic ecosystems.
• Bioaccumulation: The build-up of toxic substances in organisms as they move up the food chain. Concentrations increase at each trophic level, making top predators most at risk.

Pyramids of Biomass and Energy Transfer

• Pyramid of biomass: A diagram showing the total mass of living organisms at each trophic level in an ecosystem, displayed as horizontal bars with producers at the base.

Why Biomass is Lost Between Trophic Levels

• Biomass Loss: The reduction in total living material as energy transfers from one trophic level to the next, caused by metabolic processes and waste production

Calculating Biomass Transfer Efficiency

• Biomass Transfer Efficiency: The percentage of biomass from one trophic level that becomes biomass in the next trophic level. Usually around 10% in most ecosystems.

Understanding Pyramids of Biomass

• Biomass: The total mass of living organisms in a given area or volume, measured in grams per square metre (g/m²) or kilograms per hectare (kg/ha).
• Trophic level: The position an organism occupies in a food chain, numbered from 1 (producers) upwards to higher consumers.
• Energy transfer efficiency: The percentage of energy passed from one trophic level to the next, typically around 10% in most ecosystems.

Understanding Trophic Levels in Ecosystems

• Producers: Organisms at trophic level 1 that manufacture their own food using photosynthesis. This includes all green plants, algae, and some bacteria. They convert light energy into chemical energy stored in glucose.
• Primary Consumers: Herbivores at trophic level 2 that feed directly on producers. They obtain energy by eating plants, algae, or other photosynthetic organisms. Examples include rabbits, deer, caterpillars, and many fish species.
• Secondary Consumers: Carnivores at trophic level 3 that feed on primary consumers (herbivores). They obtain energy by eating plant-eating animals. Examples include foxes eating rabbits, birds eating caterpillars, and small fish eating zooplankton.
• Tertiary Consumers: Carnivores at trophic level 4 that feed on secondary consumers (other carnivores). They are often large predators like eagles, sharks, or big cats. Some tertiary consumers are apex predators with no natural enemies.

What is Food Security and Its Challenges

• Food Security: Having enough food to feed a population with access to sufficient, safe, and nutritious food to maintain a healthy life.

Biological and Environmental Threats to Food Security

• Pest: An organism that damages crops, reduces yields, or competes with humans for food resources. Examples include locusts, aphids, and rodents.

Declining Fish Stocks and Their Conservation

• Fish stocks: The total number of fish of a particular species in a specific area of ocean that can be caught by fishing. Measured by population surveys and catch data.
• Overfishing: Catching fish at a rate faster than they can reproduce and replace themselves. Results in declining fish populations and potential species extinction in affected areas.
• Sustainable fishing: Fishing practices that maintain fish populations at levels where they can continue breeding and replacing themselves. Ensures long-term availability of fish resources.
• Net size regulation: Rules controlling the minimum mesh size of fishing nets to allow young fish to escape and reach breeding age. Protects juvenile populations from overfishing.
• Fishing quota: A legal limit on the total amount of fish that can be caught from a particular area or species over a set time period. Enforced by government regulations.

Biotechnology Solutions for Food Production

• Fusarium: A genus of fungus used to produce mycoprotein. Grows rapidly on glucose syrup in aerobic conditions, producing protein-rich biomass.

GM Crops and Improved Nutrition

• Genetic Modification (GM): The process of changing an organism's DNA by introducing genes from another species to give it new characteristics. Used to improve crop yield, nutritional content, or resistance to pests and diseases.
• Golden Rice: A genetically modified variety of rice that contains beta-carotene (vitamin A precursor) to help prevent vitamin A deficiency. Created by inserting genes from daffodils and bacteria.

Improving Food Production Efficiency in Farming

• Food Production Efficiency: The percentage of energy input that becomes useful food output. Higher efficiency means more food per unit of feed.
• High Protein Feed: Animal feed containing elevated protein levels (typically 20-40%) to promote rapid muscle growth and weight gain.

Key ideas

5 cards from 3 lessons. Each term links to the lesson it comes from.

Structure, Function and Organisation in Living Things

• Enzyme: A protein catalyst with a specific 3D shape that speeds up biological reactions by lowering activation energy. The active site shape is complementary to the substrate.
• Cell specialisation: The process by which cells develop specific structures and functions to perform particular roles in multicellular organisms, increasing efficiency through division of labour.

Ecosystems and Energy Flow

• Population: All the organisms of the same species living in the same area at the same time. They can potentially interbreed with each other.
• Community: All the different populations of organisms living together in the same habitat. Multiple species interacting with each other.

Genetics, Evolution and Chemical Cycles

• Carbon Cycle: The continuous movement of carbon atoms through the atmosphere, living organisms, oceans, and rocks