EQ: What patterns can be observed in evolution? Patterns of Evolution EQ: What patterns can be observed in evolution? *

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

A. Mass Extinctions Huge numbers of species disappeared. Event in which many types of living things became extinct at the same time.  Huge numbers of species disappeared. Whole ecosystems were wiped out. Resulted in burst of evolution of new species in new habitat Disrupted energy flow throughout the biosphere and caused food webs to collapse (Possible Causes: Asteroids, volcanic eruptions, continental drifts, changing sea levels) *

B. Adaptive Radiation (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. *

Adaptive Radiation http://cache.eb.com/eb/image?id=54911&rendTypeId=4 *

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 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 *

Convergent Evolution http://www.wasted-disk-space.com/2007/0825/P8257787-2.jpg http://en.wikivisual.com/images/2/24/Oceanic_Whitetip_Shark.png *

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: Predator/prey Parasite/host Plant/pollinator Each party exerts selective pressures on the other, thereby affecting each others' evolution *

Coevolution Bumblebees and the flowers the they pollinate have co-evolved so that both have become dependent on each other for survival. *

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 Over a short period of time it is hard to notice *

Gradualism Current living zebras (top), extinct quaggas (bottom) http://media.eurekalert.org/release_graphics/yu0926.jpg *

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 *

Punctuated Equilibrium Horseshoe crabs have changed little since their first appearance in the fossil record. They are in a state of equilibrium *

Gradualism vs Punctuated Equilibrium *