• Third Preparatory, Science, Term 1 (English edition).
• Two lessons (1) Heredity and Variation of Traits and (2) Natural Selection and Artificial Selection.
• In the first lesson you learn how traits are passed from parents to children, how to predict the results of a cross with a Punnett square, and why some inherited diseases are more likely in marriages between relatives.
• In the second lesson you study populations, what makes them grow or shrink, and how the environment (natural selection) or humans (artificial selection) change the traits in a population.

🌳 Concept tree

Unit 3 — Variation of Traits in Living Organisms

1. ├── 1.1 Why are family members alike but not identical?
2. ├── 1.2 How are traits passed on?

├── 1.3 Alleles, dominance and recessiveness

• ├── 1.4 Mendel and the discovery of the laws of heredity

├── 1.5 Mendel's first law (law of segregation)

├── 1.6 The Punnett square

• ├── 1.7 Mendel's second law (law of independent assortment)

├── 1.8 Genetic diversity

├── 1.9 Genetic (inherited) diseases

├── 1.10 Marriage between close relatives

├── 1.11 Summary of Lesson 1

├── 2.1 Populations

├── 2.2 Population growth

├── 2.3 Factors affecting population growth

├── 2.4 Natural selection

├── 2.5 Artificial selection

├── 2.6 Natural versus artificial selection

├── 2.7 Techniques used in artificial selection

├── 2.8 Summary of Lesson 2

├── Common mistakes to avoid

├── Probability of independent events

├── Linking the ideas