Natural Selection
- Created by: Holly
- Created on: 13-02-14 17:54
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- Natural Selection
- Examples
- Orchids
- Pyramidal orchids produce a scent to attract male moths
- Some look like female wasps to attract a particular species of male wasp
- Woodpeckers
- Lesser spotted woodpecker prefers to feed from finer branches at the tops of trees
- Great spotted woodpecker prefers to feed from the broader branches
- Green woodpecker prefers to feed from the ground
- Headlice
- They have become resistant to the insecticides in shampoos
- insecticide-resistant alleles in head lice have gone from being quite rare in pre-insecticide populations to extremely common
- Orchids
- Survival of the fittest
- Some individuals by chance have a characteristic that gives them an advantage over others
- 'fit' = well adapted
- Evolution
- A change in allele frequency in a population over time
- For natural selection to lead to evolution there must be some genetic variation
- An allele may have no obvious advantage or disadvantage but it may become selectively advantageous if the environment changes
- Process of evolution
- 1. A population has some naturally-occuring genetic variation with new alleles created through mutations.
- 2. A change in the environment causes a change in the selection pressures acting on the population
- 3. An allele which was previously of no particular advantage now becomes favourable
- 4. Organisms with the allele are more likely to survive, reproduce and so produce offspring
- 5. Their offspring are more likely to have the allele so it becomes more common in the population
- 4. Organisms with the allele are more likely to survive, reproduce and so produce offspring
- 3. An allele which was previously of no particular advantage now becomes favourable
- 2. A change in the environment causes a change in the selection pressures acting on the population
- 1. A population has some naturally-occuring genetic variation with new alleles created through mutations.
- Examples
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