Origins Of Biological Diversity Chapter 15

Species A population or group of populations whose members have the ability to breed with one another and produce fertile offspring

Macroevolution Dramatic biological changes that include the origin of different species Diversity Increases

Speciation The formation of new species For new species to form there must be a barrier between the same species to make the group genetically isolated.

Kaibab squirrel Abert squirrel Speciation Kaibab squirrel Abert squirrel

Genetic Isolation Reproductive Barriers Geographic barriers

Reproductive Barriers Prevents closely related species from interbreeding Timing Behavior Habitat

Timing Similar species have different breeding seasons Eastern Spotted Western Spotted Skunk Skunk

Behavior Similar species may have different courtship or mating behaviors. Ex: Eastern & Western meadowlarks almost identical in color shape & habitat, but difference in courtship rituals differ different species

Habitat Species remain reproductively isolated because they are adapted to different habitats. Ex: Stickleback fish one is a bottom feeder, one spends time in the top open layers of lakes in British Columbia, Canada

Geographic barriers A physical barrier that separates a population into groups. Can be Mountains Islands with water in between Darwin’s 13 finches on Galapagos Valleys caused by lava flow

Mountains

Geographical isolation

Patterns of Evolution Divergent Evolution Convergent

Divergent Evolution Related organisms become less alike through Adaptive Radiation Ex: Galapagos Finches common ancestor on the main land blown to different islands naturally selected into a new species

Darwin’s Finches

Convergent Evolution Unrelated species resemble each other due to adaptation to similar environments Environment has an important selective effect on the evolution of species

A Hummingbird Moth A Humming Bird

Rate of Evolution Evolution occurs very slowly Gradualism Punctuated Equilibrium

Gradualism Gradual changes in species over time Evidence of many intermediate forms in fossil records

Punctuated Equilibrium Scientists found remains of intermediate forms but also saw that populations remained the same over large periods of time then suddenly changed