Explains the current observations and predicts new observations. A theory… Explains the current observations and predicts new observations. Present day organisms are similar, but not identical, to fossil organisms. Explain this observation What predictions can we make? We should see observable differences and similarities between fossils and living things. Others?

Darwin’s Theory of “Natural Selection” There is variation within populations. Some variations are heritable. More offspring are born than can possibly survive due to limited resource. Individuals that survive and reproduce are those with favorable traits.

What types of evidence would help us confirm these predictions? A Theory… What types of evidence would help us confirm these predictions? Fossils Embryology DNA sequence Similar Body Structures

Embryology is also used as Evidence of Evolution: Similar development of the embryo is evidence of a common ancestor All three embryos have “gill pouches” in the folds of the neck. All three have tails.

As these embryos develop, note how the last two continue to look similar. This indicates that they are more closely related to each other than they are to the first embryo

The last two are both mammals!

This suggests that if traced back far enough all three have a common ancestor because all three have similar looking embryos. This is also evidence of evolution.

Amino Acid Sequence Can be used to determine relatedness

1) homologous 2) vestigial 3) analogous Evidence for Evolution: Body Structures 1) homologous 2) vestigial 3) analogous

Homologous Structures: Traits that are similar in different species because they share a common ancestor. Note how the bones have adapted to different niches This is evidence of a common ancestor.

This is evidence that humans evolved from an ancestor that had a tail. Vestigal Structures: No longer used. The Human “Tailbone” This is evidence that humans evolved from an ancestor that had a tail.

A whale has a pelvic bone, and tiny leg bones.

Analogous Structures structures that are similar in function but are not inherited from a common ancestor. Indicate similar selective pressure.

Convergent Evolution

Analogous structures Similar niches usually contain similar evolutionary pressures (selective pressures). If ancient niches were similar to modern niches then organisms today could resemble organisms now long extinct.

Modern dolphins and prehistoric ichthyeosaurs (marine reptiles) look very similar due to the types of niche they inhabited.

Analogous structures can be caused by niches Analogous structures can be caused by niches. Similar niches create similar body forms. . . . . . .

. . Similar niches favored long necks in both sauropods and giraffes.

Similar foods (similar niches) favor similar teeth in herbivores.

Similar foods (similar niches) create similar teeth in carnivores.

Evolution can be seen experimentally through artificial selection.

“If we can change these animals in 200 years, what can nature do in millions of years?”

Types of Adaptations Anything that helps an organism Hide from/defend against predators Attract a mate/reproduce (sexual selection) Catch food

Hide from/defend against predators

Disruptive markings make it hard for predators to single out a victim.

One Peppered Moth or Two?

Attract a mate/reproduce Male-male contest Mate selection Anole Elephant Seal Peacock Peahen Irish Elk

Catch Food