1. Natural Selection & Evolution

2. Theory of Evolution
Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms.
A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

3. Before there was Darwin…
Lamarck’s Giraffes: Does this make sense?
If an organism changes during life in order to adapt to its environment, those changes are passed on to its offspring.

4. …and then there was Darwin
Charles Darwin
Trip around the world in 1831
Collected fossil evidence and observations
Focused on species of finches and turtles
Variety of organisms and variation he saw on his travels sparked his interest in evolution and adaptation

5. Darwin’s Observations
OBSERVATION #1: All species have the potential for the overproduction of offspring.
OBSERVATION #2: Environmental resources are limited. Therefore, only a fraction of offspring are surviving each generation.
OBSERVATION #3: No two individuals are exactly alike.
OBSERVATION #4: Much of this variation is heritable (passed down through generations).

6. Theory of Natural Selection
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass those advantages to their children
5. Species alive today are descended with modifications from common ancestors

7. Theory of Natural Selection
Explains HOW the traits of a population change over time (adaptation)
Changes are dependent upon the resources available and pressure from the environment
Those individuals with the traits most beneficial for the environment are more likely to EAT, SURVIVE, and REPRODUCE…
Eventually, the individual traits become the traits of the population
Ex/ all arctic hares are white
Video

8. Amoeba Sisters

9. Theory of Evolution Natural Selection + Speciation = Evolution Video
Process in which new species are created using natural selection and speciation
Takes long periods of time for evolution to occur
How modern organisms have descended from ancient ancestor
Natural Selection + Speciation = Evolution
Video

10. Speciation Creation of new species through adaptation and…
Geographical Isolation
Separated by land
Reproductive Isolation
Separated by either mating ritual, mating time, sterility of offspring, habitat or eating habits

11. Phylogenetic Tree Each branch represents a speciation event
Characterized by a new trait Video