Change Over Time Evolution A cumulative change in

Change Over Time

Evolution • A cumulative change in the characteristics of organisms or populations from generation to generation – Slow process – Many small changes collect to form a new species – Species - group of the same organism, organisms that can breed together

Charles Darwin • Observed the main mechanism of evolution on his travels around the world. Natural Selection

Galapagos Islands • Island chain off the coast of Peru • Islands vary in terrain and vegetation • Darwin studied finches on several of the islands

Galapagos Finches • Many different species are found on the island – Each finch is well adapted to their island habitat – How? Why?

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • (Potential for) Overpopulation Unchecked reproduction causes exponential population growth.

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • Competition - for resources occurs because resources are limited (space, clean water, food, etc…) – Ex. Predator Prey relationship

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • Variation with in a population. – Some organisms may be… • • faster or slower, stronger or weaker, more resistant to a disease Blend in with surroundings better • Etc.

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • Selection - some variations increase the chance of survival because they – Out run a predator – Hide from a predator – Find clean water – Use different food sources – Etc. .

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • Reproduction - organisms that are selected for survival can pass on their traits – Over time the frequency of favorable traits will increase in the population

Darwin’s Theory of Evolution by Natural Selection (OCVSRS) • Speciation - Process of forming a new species – Over time many changes accumulate – If populations are different enough that they can no longer mate with each other. The two populations are considered different species.