1. Natural Selection More offspring than will survive
Individuals vary in the population
Individuals with certain variations will survive in their environment, pass on those variations to the next generation
Overtime, offspring with certain variations make up MOST of the population

2. Types of Selection 2. Directional Selection Stabilizing selection
3. Disruptive Selection
3. Disruptive Selection

3. Populations change over time…not individuals!Aa AA aa AA

4. Reproductive Isolation due to…
Geographical isolation
Mechanical Incompatibility
Behavioral isolation
Seasonal isolation

5. Mechanical

6. GeographicaL Figure: 16-2 Title:
original population
geographical isolation
ecological isolation
GeographicaL
genetic divergence
Figure: 16-2
Title:
Models of allopatric and sympatric speciation
Caption:
The main difference between allopatric (left column) and sympatric (right column) speciation is the mechanism by which genetic isolation arises. 1 Both cases begin with a single species (white mice) occupying a relatively homogeneous habitat. 2 In allopatric speciation, the population is separated into two isolated populations by an impassable geographical barrier (here, a river changing course). In sympatric speciation, there are no physical barriers to movement, but different parts of the population become restricted to different habitats. 3 In both cases, genetic drift and/or different environmental pressures cause the two populations to diverge genetically (tan vs. white mice). 4 The isolated populations may later come into contact. If the genetic differences between the two populations have become large enough to prevent inbreeding, then the two populations constitute separate species (brown vs. white mice). Exercise Make a list of events or processes that could cause geographical or ecological subdivision of a population. Are the items on your list sufficient to account for formation of the millions of species that have inhabited Earth?
reproductive isolation

7. Behavioral

9. Seasonal

10. Sterility
Male donkey & female horse makes a mule + =

11. Sterility
Female donkey and male horse makes a “hinny”

12. Sterility
Liger
Zonkey