The Origin of Species:!By Means of Natural Selection!

Published 1859!

Darwin had discovered and described for the first time:!

A process in nature - a scientific mechanism - that could operate like artificial selection.!

Western Toad!Bufo boreas!

Individuals have natural variation among their heritable traits. Some of those variants are better suited

to their environment than others.!

Where’s frogo?!

Adaptation!

Adaptations Anyone?!

Fitness!

Individuals with adaptations that are well suited to their environment can survive and reproduce and are

said to have high fitness.!

Survival of the Fittest!

Survival: reproducing and passing

adaptations to the next generation.!

❖  The Mechanism for Biological Evolution!

the process by which organisms with variations most suited to their local environment survive

and leave more offspring.!

In natural selection, the environment - not a farmer or animal breeder - influences fitness.!

The Struggle for Existence!More individuals are born than

can survive.!

Variation and Adaptation!There is natural heritable variation.!

Survival of the Fittest!There is variable fitness

among individuals.!

Natural Selection does NOT!make organisms “better”.!

It just selects the best out of the bunch...!

If local environmental conditions change, some traits that were once adaptive may no longer be useful, and different

traits may become adaptive.!

Evolution takes TIME!!!!Each generation experiences natural selection,

but evolution is the process of natural selection over time on a population.!