IGCSE Biology Lecture Summary

Introduction

• Aimed to cover all specification points for IGCSE Biology
• Emphasized the importance of revision guides for perfect questions and answers

Characteristics of Living Organisms

• MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
• Distinguishing living from non-living (e.g., viruses do not display these characteristics)

Basic Cell Biology

• Shared Organelles: Cell membrane, cytoplasm, nucleus, ribosomes, mitochondria
• Plant-Specific Organelles: Cell wall, vacuole, chloroplasts
• **Functions of Key Organelles: **
  • Nucleus: Controls cell activities
  • Cytoplasm: Site of chemical reactions
  • Cell Membrane: Controls entry and exit of substances
  • Ribosomes: Protein synthesis
  • Cell Wall: Made of cellulose, supports and strengthens cells
  • Vacuole: Contains cell sap, maintains cell structure
  • Chloroplasts: Site of photosynthesis

Types of Cells

• Eukaryotes vs. Prokaryotes
  • Eukaryotes (animals, plants): Have membrane-bound organelles
  • Prokaryotes (bacteria, viruses): No membrane-bound organelles, contain DNA/RNA

Bacteria and Viruses

• Bacteria:
  • Can be pathogenic or beneficial (e.g., Lactobacillus in yogurt)
  • Structures: Cell wall, slime capsule, flagella, nucleoid, plasmids
• Viruses:
  • Simple structure: protein coat, DNA/RNA
  • Always pathogenic (e.g., flu, HIV, TMV)

Protists and Fungi

• Protists:
  • Diverse group; can be plant-like (algae) or animal-like (amoeba)
  • Example: Plasmodium causes malaria
• Fungi:
  • Cell structure similar to plants but no chloroplasts
  • Examples: Mucor, mushrooms
  • Saprobiotic nutrition: secretion of enzymes to decompose material

Biological Classification

• Five Kingdoms: Plants, Animals, Protists, Bacteria, Fungi
• Storage of Carbohydrates:
  • Animals: Glycogen
  • Plants: Starch
  • Fungi: Glycogen

Levels of Organization

• Cell → Tissue → Organ → Organ System → Organism
• Examples of organ systems: digestive, endocrine, reproductive, circulatory, respiratory, nervous, excretory

Enzymes and Digestion

• Enzymes: Biological catalysts, specific to substrates, affected by temperature and pH
• **Digestive Enzymes: **
  • Amylase: Starch to glucose
  • Protease: Proteins to amino acids
  • Lipase: Lipids to fatty acids and glycerol

Transport in Cells and Organisms

• **Types of Transport: **
  • Diffusion: Passive, high to low concentration
  • Osmosis: Movement of water across a partially permeable membrane
  • Active Transport: Against concentration gradient, requires energy
• Adaptations in organisms:
  • Amoeba: Large surface area to volume ratio, uses diffusion

Photosynthesis and Plant Structures

• Photosynthesis Equation: Carbon dioxide + Water → Glucose + Oxygen
• Limiting Factors: Carbon dioxide, light intensity, temperature
• Leaf Adaptations:
  • Large surface area, thin, stomata for gas exchange
  • Specific layers: waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll

Nutrition and Balanced Diet

• Nutrients Needed: Carbohydrates, fats, proteins, minerals, vitamins, water, fiber
• Specific Nutrients:
  • Vitamin C (Citrus fruits): Prevents scurvy
  • Vitamin D (Fish liver oils, sunshine): Prevents rickets
  • Iron (Red meat, spinach): Prevents anemia

Human Physiology

• Respiration: Aerobic and anaerobic, involves mitochondria
• Gas Exchange: Occurs in alveoli, supported by adaptations like large surface area
• Heart and Circulation: Double circulatory system, role of valves, structure of heart

Diseases and Immunity

• Pathogens: Bacteria, viruses, fungi can cause diseases
• **White Blood Cells: **
  • Phagocytes: Engulf pathogens
  • Lymphocytes: Produce antibodies

Reproduction

• Sexual vs. Asexual Reproduction:
  • Sexual: Involves gametes, genetic variation
  • Asexual: Identical offspring
• Structure and Function of Reproductive Systems: Male and female anatomy, roles of hormones like estrogen and testosterone

Genetics

• DNA and Genes:
  • Gene: Section of DNA coding for a protein
  • Alleles: Different forms of a gene
  • Genotype vs. Phenotype: Genetic makeup vs. physical expression
• Mendelian Genetics: Use of Punnett squares for predicting inheritance

Ecology and Environment

• Ecosystems: Definitions of terms like habitat, population, community
• Food Chains and Webs: Energy transfer, pyramids of numbers and biomass
• Human Impact: Pollution, global warming, conservation efforts

Biotechnology

• Genetic Engineering:
  • Insulin production via recombinant DNA
  • GM crops for better yield, resistance
• Fermentation: Use in food production like yogurt and beer making

These notes cover a broad range of biological topics, emphasizing important concepts and processes relevant for IGCSE Biology preparation. Reviewing these topics and related diagrams or experiments would be beneficial for thorough understanding and exam readiness.