Lesson 3

Unit 3 — Variation of Traits in Living Organisms

Lesson parts

3.1 1.1 Why are family members alike but not identical?

3.2 1.2 How are traits passed on?

3.3 1.3 Alleles, dominance and recessiveness

3.4 1.4 Mendel and the discovery of the laws of heredity

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

3.6 1.6 The Punnett square

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

3.8 1.8 Genetic diversity

3.9 1.9 Genetic (inherited) diseases

3.10 1.10 Marriage between close relatives

3.11 1.11 Summary of Lesson 1

3.12 2.1 Populations

3.13 2.2 Population growth

3.14 2.3 Factors affecting population growth

3.15 2.4 Natural selection

3.16 2.5 Artificial selection

3.17 2.6 Natural versus artificial selection

3.18 2.7 Techniques used in artificial selection

3.19 2.8 Summary of Lesson 2

3.20 Extra Study Section: Common Mistakes and More Practice