Heredity and Evolution — MCQ Practice
Heredity and Evolution — Lesson
1) Hook — A Fun Real-Life Story
Imagine a farmer in Punjab who has been growing wheat for generations. One day, he notices that some wheat plants are taller and produce more grains than others. Curious, he saves seeds from the best plants and plants them next season. Over years, this selective planting leads to stronger, higher-yielding wheat varieties. This simple practice is an example of heredity and evolution in action — traits passed down and changed over generations to improve crops!
2) Core Concepts — Heredity and Evolution Explained
Example: In humans, the brown eye colour gene is often passed from parents to children.
Example: The peppered moth in England changed its colour during the Industrial Revolution to better camouflage against predators — a classic case of natural selection.
Genetics: The Basics
| Term | Definition | Example |
|---|---|---|
| Gene | Unit of heredity made of DNA | Gene for eye colour |
| Allele | Different forms of a gene | Brown or blue eye colour |
| Dominant Allele | Allele that expresses itself even if only one copy is present | Brown eye colour (B) |
| Recessive Allele | Allele that expresses itself only when two copies are present | Blue eye colour (b) |
Mendel’s Laws of Heredity
- Law of Dominance: In a heterozygous organism, the dominant trait is expressed.
- Law of Segregation: Alleles segregate during gamete formation so each gamete carries only one allele.
- Law of Independent Assortment: Genes for different traits assort independently during gamete formation.
3) Key Formulas / Rules
Genotype Ratio (Monohybrid Cross): 1 : 2 : 1 (Homozygous dominant : Heterozygous : Homozygous recessive)
Phenotype Ratio (Monohybrid Cross): 3 : 1 (Dominant trait : Recessive trait)
4) Did You Know?
The Indian scientist J.B.S. Haldane was one of the pioneers in the field of population genetics and helped explain how evolution works at the genetic level!
5) Exam Tips — Avoid These Common Mistakes
- Do not confuse heredity and evolution: Heredity is about passing traits; evolution is about change over generations.
- Remember dominant vs recessive: Dominant traits show up even if only one allele is present.
- Practice Punnett squares: They help predict genotype and phenotype ratios.
- Use Indian examples: Mention crops like wheat or animals like the Indian peacock to make answers relevant.
- Board Pattern: Questions often include definitions, examples, and simple genetic crosses (monohybrid).
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