Organic Evolution A change in allele frequencies in a population or species.

Story of the Peppered Moth

 Dark form dominates after pollution kills lichen.

Changes in allele frequencies in populations can occur because of:  Mutations (increases genetic diversity)  Genetic Drift (chance, particularly in smaller populations)  Migrations  Natural Selection (decreases genetic diversity)

Or Natural Selection

Theory of Natural Selection 1. Since more babies are born than an area can support, many die before reaching reproductive age. 2. Individuals in a population differ. Some of this variation is heritable. 3. Individuals with heritable variations that increase their chance of reproductive success will make a greater contribution to future generations. So the characteristics of individuals in subsequent generations will change. What are they contributing?

Do the above processes cause either or both of these to occur?  Microevolution = The small genetic changes a population undergoes.  Macroevolution = Long-term, large scale evolutionary changes among groups of species (includes speciation)

Review: Mechanisms of Evolution  Mutations- change in the DNA sequence.  Genetic drift- random change in the allelic frequencies of a population.  Migration/Immigration- genetic exchanges with another population.  Natural Selection- differential reproductive success of genotypes.

Natural Selection  The differential action of environmental factors operate on the inherited variability of a population or species tending to eliminate those individuals which are less fit.

Fitness or Ecological Fitness The reproductive advantage of an individual in a population under a given set of environmental conditions.

How does Natural Selection work? Case 1: Stabilizing Selection. Case 2: Directional Selection. Case 3 : Disruptive Selection.

Natural Selection (cont.)

Suppose there is a population of rabbits. The color of the rabbits is governed by two incompletely dominant traits: black fur represented by “B” and white fur represented by “b”. A genotype of “Bb” would have gray fur (a display of blended black and white). If this population of rabbits were put into an area that had very dark black rocks as well as very white colored stone, the rabbits with black fur would be able to hide from predators amongst the black rocks and the white furred rabbits would be able to hide in the white rocks, but the gray furred rabbits would stand out in both of the habitats and thus would not survive. This environment selects for the two extremes and against the middle. What type of selection is this??

Speciation The creation of two separate species from 1 original species

How does Natural Selection work? Case 1: Stabilizing Selection.  Is this likely to lead to speciation?

How does Natural Selection work? Case 2: Directional Selection.  Is this likely to lead to speciation?

How does Natural Selection work? Case 3: Disruptive Selection  Could this lead to speciation?

Sympatric Speciation “Same land” - speciation

Sympatric Speciation

Allopatric Speciation “Different lands” - Speciation

Allopatric Speciation

Kaibab Squirrel Abert’s Squirrel

Tortoises (Gopherus) Texas Tortoise Desert Tortoise Gopher Tortoise

Diamondbacks (Crotalus) Red Diamondback Rattlesnake Western Diamondback Rattlesnake Eastern Diamondback Rattlesnake

Some Types of Evolution

Divergent Evolution

Some Types of Evolution

Convergent Evolution Green Tree Python Emerald Tree Boa

Convergent Evolution (cont.)

Some Types of Evolution