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

SpeciationThe formation of new species

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

Speciation

Kaibab squirrel Abert squirrel

Genetic Isolation

1. Reproductive Barriers2. Geographic barriers

Reproductive BarriersPrevents closely related species from interbreedingTimingBehaviorHabitat

Timing Similar species have different

breeding seasonsEastern Spotted Western Spotted

Skunk Skunk

BehaviorSimilar 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

HabitatSpecies 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 be1. Mountains2. Islands with water in between

Darwin’s 13 finches on Galapagos

3. 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 EvolutionUnrelated 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