IGCSE Biology Overview - Lecture Notes

Introduction

• Comprehensive review aimed at aiding students to achieve a grade 9 in IGCSE Biology.
• Encouragement to utilize revision guides available online.

Characteristics of Living Organisms

• Movement, respiration, sensitivity, nutrition, excretion, reproduction, and growth.
• Viruses lack these characteristics.

Animal and Plant Cell Biology

• Shared organelles: Cell membranes, cytoplasm, nuclei, ribosomes, mitochondria.
• Plant-specific organelles: Cell wall, vacuole, chloroplasts.
• Role of organelles:
  • Nucleus: Controls cell activities.
  • Cytoplasm: Site of chemical reactions.
  • Cell membrane: Regulates entry/exit.
  • Ribosomes: Protein synthesis.
  • Cell wall: Made of cellulose, protects/supports plant cells.
  • Chloroplasts: Site of photosynthesis.

Eukaryotes vs Prokaryotes

• Eukaryotes: Animal and plant cells with membrane-bound organelles.
• Prokaryotes: Bacteria and viruses lacking membrane-bound organelles.

Bacterial and Viral Cells

• Bacteria: Cell wall, sometimes slime capsule and flagella, circular chromosome (nucleoid), plasmids.
  • Can be pathogenic (e.g., Pneumococcus) or useful (e.g., Lactobacillus in yogurt).
• Viruses: Simple structure, non-living, always pathogenic, examples include flu virus, HIV, and tobacco mosaic virus.

Protists and Fungi

• Protists: Diverse group, examples include amoeba and Plasmodium (malaria-causing).
• Fungi: Mold, yeast, mushrooms, heterotrophic nutrition, saprotrophic feeding.

Biological Classifications

• Five kingdoms: Plants, Animals, Protists, Bacteria, Fungi.
• Storage of carbohydrates: Glycogen in animals and fungi, starch in plants.

Organizational Hierarchy in Biology

• Cell: Group of organelles.
• Tissue: Group of cells.
• Organ: Group of tissues.
• Organ system: Group of organs.

Digestive System

• Organs: Stomach, esophagus, pancreas, intestines.
• Enzymes: Amylase, protease, lipase.
• Bile: Emulsifies fats, neutralizes stomach acid.

Plant Physiology

• Photosynthesis: Carbon dioxide + Water → Glucose + Oxygen.
• Limiting factors: Light, carbon dioxide, temperature.
• Leaf adaptations: Large surface area, thin, specific tissue functions.

Nutrition and Balanced Diet

• Nutrients: Carbohydrates, proteins, fats, vitamins, minerals, water, fiber.
• Deficiency diseases: E.g., scurvy (Vitamin C), rickets (Vitamin D).

Respiration

• Aerobic respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy.
• Anaerobic respiration: Results in lactate in muscles, ethanol in yeast.

Circulatory System

• Heart anatomy: Four chambers, valves, arteries, veins.
• Blood vessels: Arteries have thick walls, veins have valves.

Excretion

• Humans: Kidneys excrete urea, lungs excrete CO2.
• Plants: Stomata release oxygen and CO2.

Coordination and Response

• Plant tropisms: Phototropism (light), geotropism (gravity).
• Human nervous system: Electrical impulses, reflex actions, hormonal communication.

Reproduction

• Sexual vs Asexual: Sexual involves gametes; asexual identical offspring.
• Human reproductive system: Structure and functions of male and female systems.

Genetics

• DNA structure: Chromosomes, genes.
• Punnett squares: Predict inheritance patterns, e.g., cystic fibrosis.

Biotechnology

• Genetic engineering: Insulin production using bacterial plasmids.
• GMO advantages: Improved crop resilience, nutritional benefits.

Ecology

• Definitions: Species, community, ecosystem.
• Energy transfer: Pyramids of biomass, food chains.

Human Impact

• Pollution: Greenhouse gases, CFCs, acid rain.
• Conservation efforts: Addressing eutrophication, sustainable practices.

Conclusion

• Encouragement to use additional revision materials for thorough understanding and exam preparation.