Curriculum
Science — Third Preparatory
Science — Third Preparatory
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Science — Third Preparatory 2026/2027
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Unit 1 — Chemical Reactions and Their Environmental Impacts
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Unit 2 — Electricity and Magnetism
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Unit 3 — Variation of Traits in Living Organisms
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- 1.1 Why are family members alike but not identical?
- 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
- Extra Study Section: Common Mistakes and More Practice
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Unit 4 — Dating Planet Earth
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Unit 1 - Force, Motion, Acceleration and Physical Quantities
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Unit 3 — Variation of Traits in Living Organisms
Unit 3 — Variation of Traits in Living Organisms
2.3 Factors affecting population growth
2.3 Factors affecting population growth
- Two main groups:
- Environmental factors. All living (biotic) and non-living (abiotic) components of the environment: food, water, temperature, disease, predators and space.
- When the environment is rich (plenty of resources), survival and reproduction increase and the population rises.
- When it deteriorates (scarcity, danger, pollution), the population decreases due to lower reproduction, higher death rate, or both.
- Genetic factors. The inherited traits that affect an organism’s ability to adapt, survive and reproduce.
- Individuals in a population are not identical; the genetic variation gives some a better chance in a given environment.
- fur colour, resistance to disease, tolerance of heat or cold, sharp eyesight, strong sense of smell, strong beaks for cracking seeds.
- Classifying cases:
| Case | Factor type |
|---|---|
| Heavy rain causes lush wheat growth | Environmental |
| An inherited disease reduces an animal population | Genetic |
| Birds with strong beaks survive to crack hard seeds | Genetic |
| Water pollution reduces fish in a lake | Environmental |
Resource abundance followed by scarcity→the population first increases, then, as resources run short, competition rises and the population falls until a balance with the available resources is reached.
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