Evolution and Natural Selection IGCSE Biology: Complete Guide

🦎 Understanding Evolution in IGCSE Biology

Evolution explains how species change over time through natural selection. This guide covers Darwin’s theory, adaptation, and evidence for evolution.

🧠 Memory Tips

Natural Selection: “Variation Inheritance Selection Time”

• Variation exists in populations
• Inheritance of traits
• Selection pressure favors some traits
• Time allows change to accumulate

Evidence for Evolution: “Fossils DNA Embryos Geography”

• Fossil record shows change
• DNA similarities between species
• Embryological similarities
• Geographical distribution

📚 Key Concepts

Darwin’s Theory

• Variation: Individuals differ
• Inheritance: Traits passed to offspring
• Selection: Environmental pressure
• Time: Gradual change over generations

Natural Selection Process

1. Variation exists in population
2. Competition for resources
3. Survival of the fittest
4. Reproduction of successful individuals
5. Inheritance of favorable traits

Types of Selection

• Directional: Favors one extreme
• Stabilizing: Favors average
• Disruptive: Favors both extremes

Evidence for Evolution

• Fossil record: Shows progression
• Comparative anatomy: Similar structures
• Molecular biology: DNA/protein similarities
• Biogeography: Species distribution

Adaptation

• Structural: Physical features
• Behavioral: Actions and responses
• Physiological: Internal processes
• Examples: Camouflage, migration, hibernation

🎯 Exam Focus

Common Questions:

1. Explain natural selection process (6 marks)
2. Describe evidence for evolution (5 marks)
3. Give examples of adaptation (4 marks)
4. Compare Lamarck and Darwin theories (4 marks)

Key Examples:

• Peppered moths and industrial melanism
• Darwin’s finches and beak adaptation
• Antibiotic resistance in bacteria

🚀 Master Evolution

Excel in evolution concepts with comprehensive study materials and examples.

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