Evolution Evidence

The theory of evolution states that all organisms on Earth have descended from a common

ancestor

Support for Evolution

1. The Fossil Record (Fig. 15.4 p.

423)–Fossils show that ancient

species share similarities with species that live on Earth today

Glyptodont

Armadillo

2. Comparative Anatomy (Fig. 15.6 p. 425)

a) Homologous structures develop from similar tissues in early developmental stages of the organism, but meet different needs in the adult.

Homologous Structures

Fig. 15.6 on p. 425• Q: What is similar about each of

these?• Similar bone structure, from same

tissue• Q: What is different about each of

these?• Perform different functions – grab,

walk, fly

b) Vestigial structures are features of ancestors that no longer have a function for that species and will become smaller over time until they are lost• Ex: Humans → appendix, tailbone

(Table 15.2 p. 425) Snakes →tiny bones where legs

used to be

Vestigial Structures

Other Vestigial Structures

• Vestigial Pelvis bone and femur in whales

Other Vestigial Structures

c) Analogous structures look similar in appearance and function, but are developed from anatomically different parts–They are used for the same purpose

and similar in construction, but not inherited from a common ancestor.

• Ex: eagle wing vs. beetle wing (Fig. 15.7)

bird wing vs. bat wing

Analogous Structures

3. Comparative Embryology(Fig. 15.8 p. 426)

• Embryology is the study of embryos• Embryo = early, pre-birth stage of an

organism’s development• Vertebrate embryos have similar

structures during certain stages of development, but become totally different structures in the adult form.

Comparative Embryology

Chick embryo (LM) Human embryo

Pharyngealpouches

Post-analtail

Comparative Embryology

Q: What do similarities in early development indicate?• The organisms have similar genes

controlling early development.Q: What do these similar genes indicate?• These organisms have a common ancestor.Q: Why do the embryos become

different as they develop?• Different genes start to contribute or

become “expressed” in the organism.

4. Comparative Biochemistry(Fig. 15.9 p. 427)

• Evolutionary theory predicts molecules in species with a recent common ancestor should share certain amino acid sequences.• The more closely related the species

are, the more amino acid sequences they have in common.

5. Geographic distribution(Fig. 15.10 p. 427)• Evolution is linked to climate and plate

tectonics which explains many ancestral relationships and geographic distributions seen in fossils and living organisms.–For example: South American animals

are more similar to other South American animals than to animals in Europe.

Rabbit – Europe

Mara – South America

Adaptation

• An adaptation is a trait influenced by natural selection that increases an organism’s reproductive success.

• Fitness: The ability of an organisms to survive and reproduce–how much a certain trait

appears in the next generation; measured by the amount of offspring

• Camouflage: adaptation that allows a species to blend in with their environment.

• Why? –Hide from predators/prey, more

survive to reproduce• Ex: Arctic fox (Fig. 15.11 p.

428)

Leafy sea dragon

•Mimicry: one species changes to look like another species

• Ex: Harmless snake “mimics” a poisonous snake so predators leave it alone (Fig. 15.12 p. 429)

Western Coral Snake

(poisonous)

California Kingsnake

• Antibiotic resistance: –Some species of bacteria that

originally were killed by antibiotics (like penicillin) have evolved to be drug resistant–For nearly every antibiotic, there

is at least one species of resistant bacteria

• Example: Tuberculosis (TB)