Consider the roles of different types of selective pressure.
Part A: Compare and contrast sexual selection, artificial selection, and natural selection.
Part B: Give examples of traits that may be favored in sexual selection, artificial selection, and natural selection. For each, explain if the trait would be favored by one type of selection but selected against by another type of selection.
Part A:
1. Sexual selection:
- Sexual selection is a type of natural selection that operates on traits that affect an individual's ability to obtain mates and reproduce. It can result in the evolution of traits that may be disadvantageous in terms of survival but provide an advantage in terms of mating success.
- Sexual selection can lead to the development of elaborate ornaments, displays, and behaviors that are used to attract mates.
- It is often driven by mate choice, where individuals of one sex choose mates based on specific traits.
2. Artificial selection:
- Artificial selection is the intentional breeding of plants or animals by humans for specific traits.
- It is often used in agriculture and animal husbandry to develop desired characteristics, such as increased yield, disease resistance, or aesthetic traits.
- Artificial selection can lead to rapid changes in traits that may not necessarily confer a survival advantage in the wild.
3. Natural selection:
- Natural selection is the process by which organisms that are better adapted to their environment survive and reproduce at higher rates, leading to the propagation of advantageous traits in a population.
- It operates on traits that increase an individual's chances of survival and reproduction in a given environment.
- Natural selection is the primary mechanism of evolution and is responsible for the adaptation of organisms to their habitats.
Part B:
1. Examples of traits favored in sexual selection:
- Bright plumage in male birds for attracting mates
- Elaborate courtship displays in male peacocks
- Large antlers in male deer for fighting off rivals
- In this case, these traits would be favored by sexual selection but may be selected against by natural selection if they make the individual more conspicuous to predators.
2. Examples of traits favored in artificial selection:
- Increased milk production in dairy cows
- Resistance to pests in crop plants
- Shorter snouts in dogs for brachycephalic breeds
- These traits may not necessarily be advantageous in terms of survival in the wild, so they would not be favored by natural selection.
3. Examples of traits favored in natural selection:
- Camouflage in prey animals to avoid predation
- Resistance to diseases in plants
- Increased speed in predators for catching prey
- These traits directly impact an individual's survival and reproductive success in their natural environment and would be favored by natural selection.