Features of Selection and Evolution

1. Features of Selection and Evolution

2. 1. Selection is NOT pre-designed • Selection doesn’t always move in the same direction • Eg. Predator regimes and guppies • Streams without dangerous predators • Guppies are slow to mature • Fewer, larger offspring • Males brightly coloured • Streams with dangerous predators • Guppies are fast to mature • More, smaller offspring • Males are NOT brightly coloured • These features help the guppies live longer and give them a better chance of reproducing

3. 2. Selection is NOT perfect • Can’t anticipate future change • Can’t favour a trait before that trait becomes advantageous • Limited to available variation • Environment can only act on what variation is available • Natural selection DOES NOT create variation, it only acts on variation already in the population

5. 3. Selection works on individuals – evolution affects populations • Individuals “respond” to selection by: • Living or dying • Whether they reproduce or not • Therefore, over time the population evolves

7. 4. Selection works on phenotypes, evolution affects genotype frequencies • If tall plants produce more seeds, then the population’s height will only evolve if height is heritable (passed on) • Phenotype – its physical characteristics • Genotype – its genetic makeup

9. 5. Selection is more than just “survival of the fittest” • Selection doesn’t always work on maximizing an individuals lifespan • Eg. Sexual suicide in redback spiders • After copulation, the female eats the male • This will provide energy for the female and her to produce offspring

10. 6. Evolution is irreversible • Once lost, complex structures cannot be regained (at least not in the same form) • Eg. Plethodontid Salamanders lost lung breathing and larval stage • These structures are now used for other roles

11. 7. Natural selection, evolution and morality • Natural selection is neither moral nor immoral • It doesn’t justify eugenics or racism