IGCSE Biology Comprehensive Guide (Video 91)

Features of Living Organisms

• Key characteristics: Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction, Growth
• Non-living examples (e.g., viruses) lack these features

Cell Structures

• Animal and Plant Cells:
  • Shared organelles: Cell membranes, Cytoplasm, Nuclei, Ribosomes, Mitochondria
  • Plant-specific: Cell wall, Vacuole, Chloroplasts
• Functions of Organelles:
  • Nucleus: Controls cell activities
  • Cytoplasm: Site of chemical reactions
  • Cell Membrane: Regulates entry and exit
  • Ribosomes: Protein synthesis
  • Cell Wall (plants): Made of cellulose, supports cell
  • Vacuole: Contains cell sap, maintains cell structure
  • Chloroplasts: Contains chlorophyll, site of photosynthesis

Eukaryotes vs Prokaryotes

• Eukaryotes: Animal cells with membrane-bound organelles
• Prokaryotes: Bacteria and viruses, no membrane-bound organelles

Types of Cells

• Bacteria:
  • Structure: Cell wall, sometimes slime capsule, flagella, nucleoid, plasmids
  • Pathogenic examples: Pneumococcus, Tuberculosis
  • Useful examples: Lactobacillus bulgaricus
• Viruses:
  • Structure: Protein coat, DNA/RNA
  • Always pathogenic: Flu, Cold, HIV, Tobacco mosaic virus
• Protists:
  • Examples: Algae (plant-like), Amoeba (animal-like)
  • Pathogenic example: Plasmodium (causes malaria)

Fungi

• Structure similar to plant cells but without chloroplasts
• Nutrition: Saprotrophic - secretes enzymes to break down dead matter
• Useful example: Yeast (used in bread and beer making)

Biological Organization

• Hierarchy:
  • Cells → Tissues → Organs → Organ Systems → Organism
• Digestive System Examples:
  • Organs: Stomach, Esophagus, Pancreas
  • Tissues: Glandular (secretes acid), Muscular

Enzymes

• Biological catalysts, accelerate reactions without being consumed
• Digestive Enzymes:
  • Amylase: Starch → Glucose
  • Protease: Proteins → Amino acids
  • Lipase: Lipids → Fatty acids and glycerol
• Enzyme Activity:
  • Affected by temperature and pH
  • Optimum conditions lead to peak enzyme activity

Plant Processes

• Photosynthesis:
  • Equation: CO2 + H2O → Glucose + O2
  • Factors affecting rate: CO2, Light, Temperature
• Leaf Structure Adaptations:
  • Large surface area, thin, specific layers (e.g., palisade mesophyll)

Transport in Plants

• Xylem and Phloem:
  • Xylem: Transports water and minerals
  • Phloem: Transports sugars

Human Anatomy and Physiology

• Respiratory System:
  • Key structures: Trachea, Bronchi, Alveoli
  • Gas exchange adaptations: Alveoli structure
• Circulatory System:
  • Heart functions, blood flow
  • Double circulatory system concept

Genetics and Evolution

• Genetic Definitions:
  • Gene, allele, genotype, phenotype
• Reproduction:
  • Sexual vs Asexual
  • Fertilization and development
• Natural Selection:
  • Variation, survival of the fittest, inheritance

Human Impact on the Environment

• Greenhouse Effect:
  • Gases involved: CO2, CH4, Nitrous Oxide
  • Consequences: Global warming, sea level rise
• Eutrophication:
  • Caused by excess fertilizers
  • Leads to aquatic life depletion

Biotechnology

• Genetic Engineering:
  • Use in insulin production
  • Transgenic organisms
• Selective Breeding and GMOs:
  • Examples: Disease resistance, nutritional improvements

Study Tips

• Remember key definitions
• Understand processes and cycles
• Use diagrams to reinforce learning

Ensure thorough understanding of each topic for exam success. Utilize revision guides for deeper insights.