AQA GCSE Biology (8461) Comprehensive Specification Study Notes

Topic 1: Cell Biology

4.1.1 Cell Structure

  • Eukaryotes: Plant and animal cells have a cell membrane, cytoplasm, and genetic material within a nucleus.

  • Prokaryotes: Bacteria are smaller, with a cell membrane and wall; their genetic material is a single DNA loop (often with plasmids).

  • Sub-cellular Structures:

    • Animal cells: Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

    • Plant cells: All animal cell components plus chloroplasts, permanent vacuole, and a cellulose cell wall.

  • Microscopy:

    • Electron Microscopes: Provide high magnification to see fine details of sub-cellular structures.

    • Magnification Formula: magnification=size of imagesize of real object\text{magnification} = \frac{\text{size of image}}{\text{size of real object}}

  • Specialisation: Cells differentiate for functions (e.g., sperm, nerve, muscle, root hair, xylem, phloem).

  • Culturing Microorganisms (Biology Only): Bacteria multiply via binary fission; aseptic techniques are essential for lab work.

4.1.2 Cell Division

  • Chromosomes: Found in nucleus as pairs with DNA carrying genes.

  • Cell Cycle and Mitosis: Involves genetic material doubling (DNA replication) and dividing into two identical cells.

  • Stem Cells: Undifferentiated cells with potential to form various cell types; important in therapeutic cloning.

4.1.3 Transport in Cells

  • Diffusion: Movement from high to low concentration (e.g., O<em>2O<em>2, CO</em>2CO</em>2).

  • Osmosis: Water movement through a partially permeable membrane.

  • Active Transport: Requires energy to move substances against concentration gradient (e.g., mineral ions, sugar molecules).

Topic 2: Organisation

4.2.1 Principles of Organisation

  • Hierarchy: Cells -> Tissues -> Organs -> Organ Systems -> Organism.

4.2.2 Animal Tissues and Organ Systems

  • Human Digestive System: Collaboration of organs in digestion and absorption.

  • Enzymes as Biological Catalysts: Specific enzymes aid in food breakdown (carbohydrases, proteases, lipases).

  • Heart and Blood Vessels: Structure of the double circulatory system; implications for heart disease treatment.

4.2.3 Plant Tissues and Organ Systems

  • Plant Structures: Comprises of specific tissues like xylem and phloem.

  • Transpiration and Translocation: Mechanisms of water and food transport in plants.

Topic 3: Infection and Response

4.3.1 Communicable Diseases

  • Pathogens: Types include viruses, bacteria, fungi, and protozoa.

  • Human Defenses: Skin, immune responses, vaccination importance.

4.3.2 Monoclonal Antibodies (Biology Only/HT Only)

  • Production: From a single clone of cells; uses in pregnancy tests and cancer treatment.

Topic 4: Bioenergetics

4.4.1 Photosynthesis

  • Equation: 6CO<em>2+6H</em>2O→lightC<em>6H</em>12O<em>6+6O</em>26CO<em>2 + 6H</em>2O \xrightarrow{light} C<em>6H</em>{12}O<em>6 + 6O</em>2

  • Limiting Factors: Factors affecting photosynthesis efficiency.

4.4.2 Respiration

  • Exothermic Nature: Continuous energy production processes, including aerobic and anaerobic respiration.

Topic 5: Homeostasis and Response

4.5.1 Homeostasis

  • Regulation of Internal Conditions: Mechanism and components involved.

4.5.2 Human Nervous System

  • Structure and Function: Pathway of impulses through neurones; reflex actions.

4.5.3 Hormonal Coordination

  • Endocrine System Impact: Hormones regulate various body functions.

Topic 6: Inheritance, Variation, and Evolution

4.6.1 Reproduction

  • Sexual vs. Asexual Reproduction: Differences and impacts on genetic diversity.

4.6.2 Evolution

  • Theory of Evolution: Natural selection principles and historical context from Darwin.

Topic 7: Ecology

4.7.1 Communities and Adaptations

  • Ecosystems: Interactions between living and non-living components; adaptations of species.

4.7.2 Organisation and Cycling

  • Food Chains and Ecosystem Dynamics: Structure and energy flow through ecosystems.

Required Practical Activities

  1. Microscopy: Observe and label plant/animal cells (use magnification scale).

  2. Microbiology (Bio only): Effect of antibiotics/antiseptics on bacterial growth.

  3. Osmosis: Effect of sugar solutions on plant tissue mass.

  4. Food Tests: Benedict's (sugars), Iodine (starch), Biuret (protein).

  5. Enzymes: Effect of pH on amylase activity.

  6. Photosynthesis: Effect of light intensity on pondweed oxygen production.

  7. Reaction Time: Effect of a factor on human response speed.

  8. Plant Growth (Bio only): Effect of light/gravity on seedlings.

  9. Fieldwork: Measure population size using quadrats/transects.

  10. Decay (Bio only): Effect of temperature on the rate of milk decay using pH change.