Evolution & genetic variation Chapter 16.1-16.4 Evolution & genetic variation

Darwin and his studies Charles Darwin proposed the idea of Evolution and Natural Selection Geologists were beginning to suggest that the world went through a process of change over a given period of time (1831) Sailed on the HMS Beagle to the Galapagos Islands to study animals, primarily finches Wrote On the Origin of Species where he discussed EVOLUTION!

Evolution Change over time Explains how modern organisms evolved over long periods of time through descent from COMMON ancestors

3 Patterns of biological diversity Species vary globally Species vary locally Species vary over time LED DARWIN TO DETERMINE THAT GALAPAGOS SPECIES MAY HAVE EVOLVED FROM THEIR SOUTH AMERICAN ANCESTORS

Species vary globally Darwin noticed in both South America and Africa that large, flightless birds lived in both places Different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe!

Species vary locally Different, yet related, animal species often occupied different habitats within a local area EXAMPLES: differences among the Galapagos tortoises’ shells (depending on the island they lived on) Bird beak shape

Darwin collected fossils (traces of ancient organisms) Species vary over time Darwin collected fossils (traces of ancient organisms) He noticed that some fossils of extinct animals were similar to living species EXAMPLE: Armadillo and the ancient glyptodont

Definition of natural selection Natural selection occurs in any situation in which more individuals are born than can survive (struggle for existence), there is natural heritable variation (variation and adaptation), and there is variable fitness among individuals (survival of the fittest).

EVOLUTION BY NATURAL SELECTION All organisms have to do the following: Struggle for existence: compete to obtain food, living space, etc. Variation and Adaptation: some heritable traits (body parts, colors, etc.) are better than others and more suited to a specific environment. Survival of the Fittest: how well an organism can survive and reproduce in its environment Natural Selection: occurs when more individuals are born than can survive

Principle of common descent “All species—living and extinct—are descended from ancient common ancestors.”

Vestigial Structures (pelvis in whales) Evidence of evolution Fossils Comparing anatomy and embryology (Homologous Structures, i.e. limb bones) Vestigial Structures (pelvis in whales)