Lesson 3

Unit 3 — Variation of Traits in Living Organisms

Lesson parts

3.1 1.1 Why are family members alike but not identical?

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3.2 1.2 How are traits passed on?

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3.3 1.3 Alleles, dominance and recessiveness

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3.4 1.4 Mendel and the discovery of the laws of heredity

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3.5 1.5 Mendel's first law (law of segregation)

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3.6 1.6 The Punnett square

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3.7 1.7 Mendel's second law (law of independent assortment)

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3.8 1.8 Genetic diversity

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3.9 1.9 Genetic (inherited) diseases

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3.10 1.10 Marriage between close relatives

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3.11 1.11 Summary of Lesson 1

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3.12 2.1 Populations

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3.13 2.2 Population growth

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3.14 2.3 Factors affecting population growth

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3.15 2.4 Natural selection

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3.16 2.5 Artificial selection

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3.17 2.6 Natural versus artificial selection

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3.18 2.7 Techniques used in artificial selection

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3.19 2.8 Summary of Lesson 2

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3.20 Common mistakes to avoid

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3.21 Probability of independent events

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3.22 Linking the ideas

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