Evidence of Evolution

Evidence of Evolution

A. Direct Evidence

B. Indirect Evidence

Direct Evidence

Visible evidence that organisms have changed over time

Ex. – Fossils

Fossils

Paleontologists: scientists who study fossils.

Provides incomplete information about the history of life.

Over 99% of all species that have lived on Earth have become extinct.

How Fossils Form

How Fossils FormDead organisms are buried by layers of sediment, which forms new rock.

How Fossils FormThe preserved remains may be later discovered and studied.

Dating Fossils

Relative Dating

Age is determined by the layers of rock.

Rock layers form in order by age—the oldest on the bottom, with more recent layers on top.

Relative Dating

Dating Fossils

Radioactive dating

Radioactive elements steadily break down into non-radioactive elements.

Half-lives determine the age of a sample.

Half-life - time required for half of the atoms to decay.

Half-life of Radioactive Isotopes

C-14 breaks down into N-14.

The half life of C-14 is 5,760 years.

Comparing the amount of C-14 to N-14 can determine the age of the fossil

Radioactive Dating

A fossil has 50% C-14 and 50% N-14 The fossil should be 5,760 years old. If another 5,760 years passed, what would

be the ratio of C-14 to N-14? Right!!.........C-14 25% to N-14 75%

Potassium 40

What about transitional fossils?

A B C D F G H I

1 2 3 4 5 6 8 9

Indirect Evidence of Evolution

Evidence that suggests organisms have common ancestry.

1. Embryological Similarities

Indirect Evidence of Evolution

2. Comparative Morphology

(Homologous Structures)

Indirect Evidence of Evolution

3. Similarities in Biochemistry

DNA similarities (98% of our DNA is the same as a chimpanzee)

Protein in all organisms is composed of the same 20 amino acids!!

Evidence of Evolution

Direct Evidence – something we can look at that takes us back in time.

Ex. Fossils

Indirect Evidence – something we can look at that show some kind of evolutionary connection between organisms.

Ex. Embryological similarities, Homologous structures, Biochemistry similarities