WHat is evolution ?
Evolution is the change over time or a change in allele frequency. Allele frequency can change in four ways: Mutation, Genetic Drift, Migration, and Natural Selection. Mutation is the only way new alleles are created. Mutations can be helpful or harmful to alleles. It must be heritable and may or may not affect reproductive success. Genetic Drift is a random change in allele frequency. One example is the population bottle neck. Migration which is gene flow is a group of individuals that's moves from one population to another. Natural Selection is the "survival of the fittest". Those who are best suited to the environment survive, and reproduce. This has the most reproductive success. Three conditions needed for natural selection to occur is variation in a trait, the trait must be heritable, and differential reproductive success. Darwin concluded that birds adapted their beak to specific foods on each island. An example of evolution is mammals.. they start small the large, then primates, then into humans.
special adaptations
- Eyes: It is hard to see at the bottom of the water crayfish live in. Their eyes are on a short stem that allows them to see in all directions if the move them.
- Reproduction: Female crayfish have adapted a way to store sperm until they are ready to lay their eggs.
- Color: Crayfish are only red when you cook them. They are actually different colors depending on their habitat. It helps them to camouflage with their surrounding.
- Pincers: The small pincers help bring food to the crayfish mouth and help to cut them into smaller pieces. The large pincers help to catch preys and help to ward off predators.
- Exoskeleton: When the crayfish gets bigger their exoskeleton starts to shed and become harder and harder making it harder for predators to get them.