Patterns in evolution: Macroevolution

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6 themes in evolution

• Extinction Adaptive radiation• Convergent evolution Coevolution• Punctuated equilibrium• Developmental genes and body plans

Extinction

• 99% of all species once living are now extinct

• Species that can not adapt to a changing environment go extinct.

• Survivors experience a burst of diversification, producing many new species

Diatrymas: 55-65 MYA stood 2 m tall

Adaptiveradiation

• A single species or a small group of species evolve into many diverse forms, living in different niches.

Anole lizards of theCaribbean islands

Convergent evolution

• Unrelated organisms can develop to look similar to others if they adapt to the same environment

• Ex: all species that swim in the water are streamlined, with paddles for locomotion

Shark, dolphin, and penguin representaquatic fish, mammal, and bird species

Coevolution

• Organisms that are closely connected often evolve together

• Occurs often in flowers and their pollinators• Plants evolve poisons to ward off insects that eat

them, the insect then become immune over time.

Punctuated equilibrium

• Evolution can proceed at different rates

• There can be long periods of stability, then brief periods of more rapid change

Developmental genes & body plans

• Master control genes guide the development of major body parts in animals

• Small changes in the expression of developmental genes can cause large changes in the adult

Winged and wingless fruit flies

Summary & Review (answers these questions as part of your summary/ in paragraph

form)

1.Given an example of coevolution, not mentioned in the lecture.

2.What type of evidence would support the theory of punctuated equilibrium?

3.Would you expect adaptive radiation to occur everywhere or only in some environments?

4.Do you think most mutation in hox genes are helpful or harmful? Why?