Evidence of Evolution

Early Evidence of Evolution =

1. Fossils Relics or impressions of organisms from

the past.› Show changes over time from simple to

complex.› Many fossils don't have descendants.

Fossil Record

Most fossils found in sedimentary rock Due to aquatic

preservation, fossils remain largely intact and fossilize in layers

Rock forms in layers, or strata Often sand or silt is

deposited on top existing layer,

compacting it into rock

Fossil Record Limited:1. Type of material

preserved (bone, shell, impressions, amber)

2. Incomplete record3. Easily disrupted

Evolution Relevance

Life has changed over time.

Many species failed to survive and became extinct.

Law of Superposition- Fossil Record is

formed due to the layering

- Older rock is “lower” than younger rocks

- Fossils help show what organisms have similarities or dissimilarities

Comments1. Fossilization is a rare event.2. Only hard parts fossilize well.3. Problem in finding fossils.4. Interpretation.5. Missing Links.

2. Homology

Evidence for evolution: used with fossils and current species

Homologous Structures - Same structure, different function

Mammal forelimbs

3. Vestigial structures structures that have a major function in one

organism, but less in another ex: whale limbs. ostrich wings

› Evidence for descentfrom common ancestor

4. Comparative Anatomy: Structural similarities link related species

5. Development (Embryology) Developing embryos of different

organisms appear similar during maturation.

Distinctive differences occur later in the process

Comparative embryology:Similar embryo development in closely related species

6. BiogeographyThe geographical distribution of species.Some animals in South American tropics

share similarities with African desert animals rather than African tropical animals

Australia is home to more marsupial animals than anywhere else in the world, and had relatively few placental animals.

7. Plate Tectonics How the continents moved Supports evolution by looking at

which species used to be close to each other geographically

8. Molecular Biology In the era of DNA –

- The closer the DNA sequences, the closer related› The less the sequences match, the further

the relationship› Humans and Chimps 98% similar genes› Humans and Mice 70-80% similar genes