EvolutionHigh NEET PriorityClass 12
Natural Selection
Definition
Natural selection is the process by which organisms with favorable traits are more likely to survive and reproduce, passing these traits to the next generation. First proposed by Charles Darwin, it is the primary mechanism of evolution. Over time, beneficial traits become more common in a population while harmful traits decrease.
Key Points for NEET
- 1Requires variation, heritability, and differential reproduction
- 2Acts on phenotypes, not genotypes
- 3Can be stabilizing, directional, or disruptive
- 4Leads to adaptation and evolution
- 5Different from artificial selection (human-directed)
Example
Peppered moths: dark moths survived better in polluted areas, changing population color
Asked in NEET
NEET 2023NEET 2022NEET 2020
Common Mistakes to Avoid
- ✗Confusing natural selection with Lamarckism — acquired characters are NOT inherited
- ✗Thinking natural selection creates new traits — it only selects from existing genetic variation
- ✗Mixing up stabilizing (reduces variation), directional (shifts mean), and disruptive (splits population) selection
Quick Revision Notes
- ⚡Darwin's 4 observations: variation exists, more offspring than survive, struggle for existence, survival of fittest
- ⚡Industrial melanism (peppered moth) is the classic example of directional selection
- ⚡Natural selection acts on phenotypes but changes genotype frequencies over generations
- ⚡Fitness = reproductive success, not just survival; measured by number of viable offspring
Related Terms
EvolutionAdaptationFitnessDarwinSpeciation
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