Patterns of Evolution: A. Mass Extinctions. B. Adaptive Radiation C. Convergent Evolution D. Coevolution. E. Gradualism F. Punctuated Equilibrium

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1 : A. Mass Extinctions B. Adaptive Radiation C. Convergent Evolution D. Coevolution E. Gradualism F. Punctuated Equilibrium 1

2 A. Mass Extinctions: Over the past 540 million years, life on Earth has passed through five great mass extinction's. 1. Late Ordovician 2. Late Devonian 3. End Permian (sometimes called Permian Triassic) 4. End Triassic 5. End Cretaceous (Cretaceous Tertiary or K T) 2

3 A. Mass Extinctions: Over the past 540 million years, life on Earth has passed through five great mass extinction's. 1. Late Ordovician 440 MYA 86% of life on earth was wiped out 2. Late Devonian 365MYA 75% of species land plants: nutrients from roots went into ocean algae bloom lack of oxygen volcanic ash 3. End Permian (sometimes called Permian Triassic) MYA 96% lost volcanic eruption? 4. End Triassic MYA wed dinosaurs to dominate 5. End Cretaceous (Cretaceous Tertiary or K T) 65MYA extinction of dinosaurs 6. Holocene Extinction present caused by human activity 3

4 : A. Mass Extinctions B. Adaptive Radiation C. Convergent Evolution D. Coevolution E. Gradualism F. Punctuated Equilibrium 4

5 B. Adaptive Radtion (Divergent Evolution) The evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat Many new species diversify from a common ancestor. The branching out of a population through variation. The new species live in different ways than the original species did. Hawaiin honeycreepers Beak color,shape and size is different for different habitats and nutrition. 5

6 C. Convergent Evolution: Opposite of divergent evolution (adaptive radiation) Unrelated organisms independently evolve similarities when adapting to similar environments, or ecological niches Analogous structures are a result of this process (same function, different species) Example: penguin limb/whale flipper/fish fin The wings of insects, birds, pterosaurs, and bats all serve the same function and are similar in structure, but each evolved independently 6

7 D. Coevolution: The mutual evolutionary influence between two species When two species evolve in response to changes in each other They are closely connected to one another by ecological interactions (have a symbiotic relationship) including: > Predation: Predator/prey > Parasitism: Parasite/host > Mutualism: Plant/pollinator Each party exerts selective pressures on the other, thereby affecting each others' evolution Commensalism is not coevolution because one party is unaffected. 7

8 E. Gradualism The evolution of new species by gradual accumulation of small genetic changes over long periods of time Emphasizing slow and steady change in an organism Occurs at a slow but constant rate Cannot see this over a short period of time. Top: current living zebras Bottom: extinct quaggas 8

9 F. Punctuated Equilibrium Stable periods of no change (genetic equilibrium) interrupted by rapid changes involving many different lines of descent Opposite of gradualism It is rare, rapid events of branching speciation Characterized by long periods of virtual standstill ("equilibrium"), "punctuated" by episodes of very fast development of new forms 9

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