Evidence for Evolution

The Fossil Record

• The fossil record provides evidence of the extinction of species, the origin of new species, and changes within groups over time

Fig. 22-15

Bristolia insolens

Bristolia bristolensis

Bristolia harringtoni

Bristolia mohavensis

Latham Shale dig site, SanBernardino County, California

Dep

th (m

eter

s)

0

2

4

6

8

10

12

14

16

18

1

2

3

3

3

1

2

44

• Evolutionary transitions should leave signs in the fossil record

• Paleontologists have discovered fossils of many transitional species

Fig. 22-17

Humerus

Radius

Ulna

Carpals

Metacarpals

Phalanges

Human WhaleCat Bat

• Homology is similarity resulting from common ancestry• Homologous structures are anatomical similarities that

represent variations on a structural theme present in a common ancestor

Human embryoChick embryo (LM)

Pharyngealpouches

Post-analtail

• Comparative embryology reveals anatomical homologies not visible in adult organisms

• Vestigial structures are left-overs of features that served important functions in the organism’s ancestors

Top 10 Vestigial Structures10. Wings in flightless birds9. Hind Leg bones in whales8. Erector Pili and Body Hair7. Human Coccyx8. Blind Fish Astyanax mexicanus.5. Wisdom Teeth in humans4. Sexual Organs of dandelions3. Fake sex in virgin whiptail lizards2. Male Breast tissue and nipples1. The human appendix?

Astyanax mexicanus Virgin Whiptail Lizards – “Parthenogenesis”

Biogeography

• Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution

• Islands have many endemic species that are often closely related to species on the nearest mainland or island

Biochemistry

• In modern research scientists can compare the similarities in the DNA between two related species. The more similar the DNA the more related the two species are.