• 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. Heredity and Variation of Traits
2. │ ├── 1.1 Why are family members alike but not identical?
3. │ ├── 1.2 How are traits passed on?

│ ├── 1.3 Alleles, dominance and recessiveness

1. │ ├── 1.4 Mendel and the discovery of the laws of heredity
2. │ ├── 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

└── Linking the ideas