Give me some proof!

Evidence for Evolution

1. Studies of Fossils

• What are Fossils?– Fossils are any trace of dead organisms.

Fossil evidence• Shows history of life on Earth.

• Shows how different organisms have changed over time.

• Fossils appear in a particular order.

What can fossils tell us?

• Finding the age of a fossil will show us how long ago that organism existed.

Example

• This dinosaur fossil shows us that it existed 113 million years ago.

2. Comparison of Structures

• We can compare body structures of different living organisms to determine evolutionary relationships.

2A. Homologous Structures

Homologous Structures: structures that share a common ancestor.

•The structures can be different sizes & serve different functions.

•Similarities and differences among the homologous structures help determine how recently species shared a common ancestor.

Example

• The human, cat, whale and bat all share a common mammalian ancestor.

2B. Analogous Structures

Analogous Structures: Structures that serve the same function in different species, but evolved independently (NOT from a common ancestor).

Example

• The Wings of Birds, Bats, & Butterflies

• Wings serve similar function but did NOT evolve from a common organism.

2C. Vestigial Structures

Vestigial Structures: Structures with NO known functions.

•Inherited from ancestors

•Structures are remnants of organism’s evolutionary past

Example in humans: appendix, tailbone, wisdom teeth (Individuals still have them because they must not affect the organisms fitness)

2D. Developmental Structures

• Developmental structure patterns show evolutionary relationships.

• The more closely related show the organisms descended from a common ancestor.

• Example:– Human Embryos & Chicken Embryos are very similar

at 4 days– Thus, must have evolved from common ancestor

3. DNA & proteins

• The universal genetic code provides evidence of common descent.

• We can also compare similarities in gene sequencing and protein production between organisms.

• We also know that heritable variation on which natural selection operates may be caused by mutations or the reshuffling of genes during sexual reproduction.

Example

• The genetic code is nearly identical in almost all organisms

• Humans and Chimpanzees have ~98% of the same genes and therefore have a common ancestor