Fossil Record• Definition: The fossil record is all the known fossils and their

placements in the formation of rocks and positions in time.

• Information: The fossil record is evidence of the evolution of plants and animals, and their extinction.

6.1 Fossils and Evolution

Fossil record• Why are there gaps in the fossil record?

– Decay before fossilization

– Geological process destroy fossils

– They are undiscovered

6.1 Fossils and Evolution

(cont.)

How can fossil and rock data determine when an organism lived?

Homologous Structures• DEFINITION: Parts of organisms that are similar in

origin and structure are called homologous structures.

6.2 Biological Evidence

• INFORMATION:

– Are the result of evolution

– Can indicate how closely two or more species share common ancestors

Homologous Structures

• EXAMPLES: At some point in our pasts, humans, frogs, bats, birds, and cats all shared a common ancestor, because the bones in the upper limbs are homologous.

Homologous Structures (cont.)

6.2 Biological Evidence

The bones in the upper limbs of these animals are homologous structures.

Analogous Structures• DEFINTION: Analogous structures appear similar, but

have different ancestral origins.

6.2 Biological Evidence

• INFORMATION: Result from similar environmental conditions that produced similar natural selection outcomes

• EXAMPLE: The wings of birds and insects.

Vestigial Structures• DEFINTION: structures that have no function in their

present-day form.

6.2 Biological Evidence

• INFORMATION: Scientists hypothesize that the structures once functioned in an ancestor.

Vestigial Structures• EXAMPLES:

– Pelvic bones in whales

– Wings in ostriches

– Pelvic spurs in boas and phythons

– Eyes in cavefish

– Tail bones in humans

Embryology• DEFINTION: The science of

the development of embryos from fertilization to birth is embryology.

6.2 Biological Evidence

• INFORMATION: The more closely related species are, the more features they share during development.

• EXAMPLES: Fish, reptiles, birds, and human embryos

Geographic Isolation• Definition: Geographic isolation occurs when

populations of species are separated by a physical barrier.

• Information: Leads to closely related species that appear different.

• Examples:

– Salamanders in California and Oregon

– Squirrels in the Grand Canyon

6.3 Evolution and Plate Tectonics

Convergent Evolution• Definition: Convergent evolution results in structural and functional similarities.

• Information: Sometimes distant locations with similar environmental conditions have species with similar traits that evolved independently.

• Examples: Catci and Euphorbia

6.3 Evolution and Plate Tectonics