Population Genetics

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Organisms of two populations require different habitats

Slide 13

Mechanisms of Speciation

Behavioral Isolation

Changes in habits that identify one population with another

Mating rituals

Methods of communication

Slide 14

Mechanisms of Speciation

Seasonal Isolation

Reproductive cycles do not coincide

Plants that flower at different times

Animals that mate or nest build at different times

Slide 15

Mechanisms of Speciation

Mechanical Isolation

Physical characteristics that keep organisms from interbreeding

Difference in size

Difference in reproductive anatomy

Inability of sperm to penetrate the egg

Slide 16

Observations From the Fossil Record

Species often remain stable for millions of years with little or no noticeable change

Species may disappear rapidly and new species may appear just as fast

Slide 17

Population Evolution

Slide 18

Punctuated Equilibrium

Long periods of

stability followed

by short periods

of rapid change