AQA Biology Paper 2 Key Topics

Topics Covered

• Homeostasis and response
• Inheritance, variation, and evolution
• Ecology

Homeostasis

Definition

• Regulation of internal conditions despite external changes.
• Ensures optimal conditions for enzyme activity and bodily functions.

Key Components

• Nervous System: CNS (brain, spinal cord) and PNS (peripheral nerves).
• Reflexes: Quick responses bypassing the brain; involve reflex arcs.
• Glands: Produce necessary chemicals (e.g., saliva).

Experiment

• Reaction time measured by dropping a ruler and catching it.
• Variables: Stimulants (e.g., coffee) or depressants.

Brain, Eye, and Thermoregulation (Triple Only)

Brain Parts

• Cerebral Cortex: Memory, speech, problem-solving.
• Cerebellum: Motor skills, balance, coordination.
• Medulla Oblongata: Controls heart and breathing rates.

Eye Functions

• Accommodation: Adjusts lens shape for focusing.
• Photoreceptors: Rods (light intensity), cones (color detection).

Thermoregulation

• Vaso-constriction/dilation control heat loss.

Hormonal Control

Endocrine System

• Glands secrete hormones slower than nervous signals.
• Key glands: Pituitary, pancreas, thyroid, adrenal, ovaries/testes.

Blood Glucose Regulation

• Insulin and glucagon balance blood glucose levels.
• Diabetes types 1 and 2: Insulin production/absorption issues.

Water and Nitrogen Balance (Triple Only)

• ADH regulates water absorption in kidneys.
• Dialysis for kidney failure.

Reproduction

Menstruation Cycle

• Hormones: FSH, estrogen, LH, progesterone.

Contraceptive Methods

• Pills, implants, condoms, IUDs, surgical methods.

Infertility Solutions

• Injections, IVF, risks of multiple births.

Hormones in Stress

• Adrenaline: Increases heart/breathing rates.
• Thyroxine: Controls metabolic rate.

Plant Hormones (Triple Only)

• Gibberellins: Seed germination.
• Ethylene: Fruit ripening.
• Auxins: Phototropism and geotropism control.

Inheritance, Variation, and Evolution

Sexual vs Asexual Reproduction

• Sexual introduces variation.
• Asexual ensures identical offspring.

DNA and Genetics

• Genome: Complete genetic material.
• Mutations: Can alter protein synthesis.
• Genotype vs Phenotype.

Inheritance Patterns

• Dominant/Recessive alleles.
• Punnett squares for probability predictions.

Evolutionary Theories

• Darwin's natural selection.
• Epigenetics: Environmental gene expression influence.

Genetic Engineering

• Modifying organisms for beneficial traits.
• Techniques like gene insertion into vectors.

Fossils and Cloning (Triple Only)

• Fossils: Mineralized remains or impressions.
• Cloning: Techniques for plants and animals.

Ecology

Ecosystem Dynamics

• Abiotic vs Biotic factors.
• Food Chains: Energy flow through trophic levels.

Biodiversity

• High biodiversity stabilizes ecosystems.
• Threats: Human development, waste, pollution.

Environmental Impact

• Global warming contributors: CO2 & methane.
• Sustainable practices: Agriculture, fishing.

Food Security

• Challenges: Population growth, resource distribution.
• Sustainable farming and fishing methods.