AQA Biology Paper 2 Revision Guide

Topics Covered

• Homeostasis and Response
• Inheritance, Variation, and Evolution
• Ecology

Homeostasis and Response

Homeostasis

• Regulation of internal conditions despite external changes
• Maintains optimal conditions for enzyme reactions
• Key regulated areas: blood glucose, temperature, water levels

Nervous System

• Components: CNS (brain & spinal cord) and PNS (nerves)
• Process: Receptors (e.g., skin) detect stimuli, send electrical signals via neurons
• Synapses: Signals transfer across neurons using neurotransmitters
• Reflex Arcs: Signal bypasses brain for faster response

Brain and Eye (Triple Only)

• Brain:
  • Cerebral Cortex: memory, speech, problem-solving
  • Cerebellum: movement, balance, coordination
  • Medulla: heart rate, breathing
• Eye:
  • Accommodation: Lens adjusting for focus
  • Parts: Pupil, cornea, retina (rods & cones)
  • Myopia & Hyperopia: Focusing issues, corrected by glasses or surgery

Thermoregulation

• Heat Response: Sweating, vasodilation
• Cold Response: Shivering, vasoconstriction

Endocrine System

• Main Glands:
  • Pituitary: Master gland
  • Pancreas: Insulin & glucagon for blood glucose
  • Thyroid: Metabolism
  • Adrenal: Adrenaline
  • Ovaries/Testes: Reproductive hormones

Inheritance, Variation, and Evolution

Reproduction

• Sexual: Meiosis creates gametes, leads to genetic variation
• Asexual: Cloning, genetically identical offspring
• Human Genome Project: Mapping of genes, disease identification

Genes and DNA

• DNA Structure: Double helix, made of nucleotides (A, T, C, G)
• Mutations: Can be harmful, lead to non-functioning proteins
• Epigenetics: Non-coding DNA influences gene expression

Genetic Inheritance

• Dominant vs. Recessive Alleles
• Use of Punnett Squares to predict genetic outcomes
• Chromosomes determine sex: XX = female, XY = male

Evolution

• Theory of Evolution: Darwin’s natural selection
• Evidence: Bacterial resistance, fossil records
• Selective Breeding: Enhancing desired traits
• Genetic Engineering: Modifying organisms for desired traits

Ecology

Ecosystems

• Interaction and interdependence among organisms
• Abiotic Factors: Non-living (light, temperature, pH)
• Biotic Factors: Living (food, predators, diseases)
• Quadrats & Transects: Tools to measure population distribution

Food Chains and Pyramids

• Producers: Plants, algae
• Consumers: Herbivores, carnivores, omnivores
• Apex Predators: Top of the food chain
• Trophic Levels: Energy flow in ecosystems

Cycles and Decomposition

• Carbon Cycle: Recycling of carbon through respiration, photosynthesis
• Water Cycle: Movement of water through evaporation and precipitation
• Decomposition: Breakdown of organic matter

Biodiversity and Human Impact

• Importance of maintaining biodiversity for ecosystem stability
• Human Activities: Habitat destruction, pollution, deforestation
• Food Security: Issues due to population growth and environmental changes
• Sustainable Farming and Fishing: Techniques to maintain resources

Tips for the Exam

• Understand and memorize key processes and terms
• Practice using diagrams like Punnett squares and food chains
• Apply concepts to real-world examples
• Be aware of differences between higher and foundation tiers