Darwin and Natural Selection

Darwin’s Observations Darwin’s voyage provided insight on Evolution.

He Observed….Fossils Fossils of extinct animals that resemble modern animals. Fossils of sea animals high in the Andes mountains.

He Observed….Geologic Processes Darwin witnessed an earthquake. Applied: Geologic processes can add up to great changes over a long period of time.

He observed…..Variation Differences in a physical trait among organisms in the same species.

He observed…Adaptation A variation or characteristic that allows an organism to better survive in its environment.

Adaptation Can lead to a genetic change in a population over time.

He observed ….Artificial selection Humans change a species by breeding it for certain traits

Darwin started breeding pigeons Heritability - the ability of a trait to be passed down.

Darwin proposed Natural Selection as a mechanism for evolution.

Natural Selection-  organisms better adapted to their environment tend to survive and produce more offspring.

4 main principles to Natural Selection: Variation Overproduction Adaptation Descent with modification

1. Variation- differences among individuals are the basis for natural selection. Ex. Some jaguars may be born with slightly larger jaws and teeth due to natural variation in the population. Some variations are heritable.

2. Overproduction A jaguar may produce many offspring, but not all of the young will survive due to competition for resources.

3. Adaptation Jaguars with larger jaws and teeth are able to eat shelled reptiles. These jaguars are likely to survive longer and leave more offspring than jaguars that can eat only mammals.

4. Descent with modification Because large teeth and jaws are heritable traits, they become more common characteristics in the population.

Fitness- is the measure of survival ability to produce more offspring. Natural Selection Fitness- is the measure of survival ability to produce more offspring.