15-3

Evolution in Process

Evidence of Evolution

• 1. Homologous Structures• 2. Analogous Structures• 3. Vestigial Structures• 4. Similarities in Embryology• 5. Similarities in Macromolecules

1. Homologous Structures

• Similar features that originated in common ancestor (recent)

• Ex: human arm, bird wing, frog arm

2. Analogous Structures

• Features which share a purpose but do not have common origin

• Ex: bird wing insect wing

3. Vestigial Structures

• Features which were useful to an ancestor but have no current use

• Ex: – Human tail bone, appendix– Snake pelvic bones

limb bones– Whale pelvic bones

4. Similarities in Embryology

• “Ontogeny recapitulates phylogeny”• Embryological development repeats

evolutionary history• Ernst Haeckel

5. Similarities in Macromolecules

• Amino acid sequence (proteins)• Ex cytochrome C• The more similarities = the more recent

common ancestor

Patterns of EvolutionWays in Which Species Change

• 1. Coevolution• 2. Convergent evolution• 3. Divergent evolution

1. Coevolution

• Change of 2 or more species in close association with each other

• Ex predator/prey

flowers/pollinators

2. Convergent Evolution

• Occurs when similar phenotypes in different species are selected in similar environment even though ancestors were very different

• Ex shark & porpoise

3. Divergent Evolution

• Occurs when 2 or more related populations or species become more & more different (usually due to habitat changes)

• 2 types– Adaptive radiation– Artificial selection

Adaptive Radiation

• Many species from single common ancestor• Ex Darwin’s finches

Artificial Selection

• Selective breeding• Ex dogs, cats, horses, sheep,

chickens, fruit