GCSE Combined Science: Biology - Paper 2 Notes

Introduction

• Presenter: Emma
• Content overview for both higher and foundation tiers.
• Importance of practicing questions.

Homeostasis and Response

Homeostasis

• Definition: Regulation of internal environments/conditions.
• Keeps conditions constant for optimal enzyme function.
• Three key conditions in humans:
  • Blood glucose concentration
  • Water levels
  • Body temperature (~37°C)

Human Nervous System

• Stimulus: Change in environment detected by receptor cells.
• Receptor Cells: Detect changes and send information to Coordination Center (e.g., brain, pancreas).
• Effectors: Muscles and glands that restore optimal conditions.

Neurons and Nervous System Pathway

• Neurons: Individual nerve cells; many bundled together form a nerve.
• Pathway: Stimulus -> Receptor -> Sensory Neuron -> Relay Neuron -> Motor Neuron -> Effector -> Response.
• Reflex actions: Automatic and rapid responses.

Synapse and Impulses

• Synapse: Gap between neurons; slower chemical diffusion but essential for impulse transfer.
• Importance of correct terminology (impulses, not messages).

Human Endocrine System

• Composed of glands secreting hormones into the bloodstream.
• Major glands: Pituitary (master gland), thyroid, pancreas, adrenal glands, testes, ovaries.
• Hormonal vs. nervous system: Slower but longer lasting.

Hormonal Control and Feedback

Negative Feedback

• Used to maintain constant hormone levels (e.g., thyroxine regulation via TSH).

Blood Glucose Regulation

• Importance for cellular respiration and organ protection.
• Insulin: Lowers blood glucose by enabling cellular glucose uptake and glycogen storage.
• Glucagon: Raises blood glucose by converting glycogen back to glucose.

Diabetes

Type 1 Diabetes

• Cause: No insulin production.
• Treatment: Insulin injections, no cure yet.

Type 2 Diabetes

• Cause: Insulin resistance.
• Treatment: Lifestyle changes (diet, exercise), medication if necessary.

Reproductive Hormones and Menstrual Cycle

• Testosterone in males: Stimulates sperm production.
• Estrogen in females: Initiates menstrual cycle, growth of secondary sexual characteristics.

Menstrual Cycle

• FSH, LH, estrogen, and progesterone regulate the cycle.
• Ovulation and uterine lining maintenance.

Contraception

• Hormonal Methods: Pills, patches, injections, implants (inhibit FSH, LH).
• Non-Hormonal Methods: Barrier methods, IUDs, surgical procedures, and abstinence.

Infertility Treatments

• Fertility Drugs: Contain FSH/LH.
• IVF: Eggs fertilized in vitro and implanted into the uterus.

Inheritance, Variation, and Evolution

Sexual and Asexual Reproduction

• Sexual: Genetic variation from gamete fusion.
• Asexual: Identical offspring via mitosis.

Meiosis

• Reduction division creating gametes with half chromosome number.

DNA and Genome

• DNA: Double helix, genes code for proteins.
• Genome: Entire genetic material.

Inheritance Patterns

• Alleles determine traits (dominant vs. recessive).

Genetic Disorders

• Cystic Fibrosis: Recessive; Polydactyly: Dominant.

Genetic Engineering

• Transfer of genes to create GM organisms.
• Used in crops for resistance and increased yield, and in bacteria for insulin production.

Fossils and Extinction

Fossils

• Remains of organisms, formation via mineralization or trace preservation.
• Incomplete fossil record due to geological activity and lack of soft-bodied preservation.

Extinction

• Causes: New predators/diseases, competition, environmental changes, catastrophic events.

Antibiotic Resistance

• Rapid bacteria evolution due to high reproduction rate.
• Prevention: Appropriate antibiotic use, completing courses, reducing agricultural use.

Ecology and Ecosystems

Community Interactions

• Ecosystems composed of interacting species and abiotic factors.
• Abiotic Factors: Light, moisture, pH, temperature, etc.
• Biotic Factors: Predators, food availability, competition.

Sampling for Ecology

• Quadrats: For slow-moving organisms.
• Transects: For studying distribution across a gradient.

Cycles in Nature

• Water Cycle: Evaporation, condensation, precipitation.
• Carbon Cycle: Photosynthesis, respiration, combustion.

Biodiversity and Human Impact

Importance

• Biodiversity ensures ecosystem stability and resource availability.

Human Impact

• Activities reducing biodiversity: Building, quarrying, landfill.
• Pollution types: Land, air, water.

Global Environmental Issues

Deforestation and Peat Destruction

• Loss of habitats, increased CO2 levels.

Global Warming

• Caused by CO2, methane; leads to climate change and biological consequences.

Conservation Efforts

• Breeding programs, habitat protection, sustainable practices.