Natural selection
1. Phenotypic variation exists within a population.
2. Specific traits, aka, adaptations, confer fitness advantages.
3. Individuals with those traits benefit from increased reproductive success.
Example
- Population of original and mutated beetles
- Beetles with yellow circles on their wings
- Beetles with small black circles within the yellow circles; these markings resemble the eyes of a much larger animal.
- Snake is a predator that feeds on beetles, but fears mutated beetles.
- Beetles with black markings survive and out-reproduce the original form.
Natural Selection
Natural selection and Adaptations
- Natural selection is the process of selection for traits that enhance reproductive success in a particular environment.
- Remember that natural selection acts on individuals, but produces evolution within the population: ie, individuals do not evolve / populations do through the natural selection of traits that enhance reproductive success.
- Natural selection promotes adaptation, which is a term that can be used to describe a trait or a process:
- As a trait, an adaptation is an inherited characteristic that enhances reproductive success; natural selection acts to promote adaptations.
- Tradeoffs:
- Natural selection is limited by trade-offs, or compromises, between the costs and benefits of traits. In other words, natural selection produces adaptations that are "better than" the possible alternatives, not perfect.