Speciation

Slide 70 - Speciation: When a population of a species changes so much it becomes an entirely new species.

Slide 71 - Gene Pool:All the alleles in a population.

Slide 72 - Allelic FrequencyFrequency = Percent

The Percent of any specific allele (e.g. R and r) in the gene pool.

Allele # of Alleles in

Population

Allelic Frequency

R 5 5/20 = ¼ = 25%

r 15 15/20 = ¾ = 75%Total Number Alleles in population =

20

Slide 73 - Genetic EquilibriumEquilibrium = state of no change.

When % of alleles do not change over time.This means population is NOT evolving!

AlleleYear2000

Year2005

R 25% 27%r 75% 73%

Slide 74 – What causes populations to evolve (aka moving away from

genetic equilibrium)

Mutation Genetic Drift Migration

Slide 75 - MutationChanges in DNA sequence.

Purpose of DNA is to make proteins.The mutated DNA will likely make a different protein and cause change in the organism.

DNA Sequence: A-T-T-G-A-G-C

Mutated DNA Sequence: A-A-T-G-A-G-C

Slide 76 - Genetic DriftChange in gene pool by chance events.

Affects small populations!

Slide 77 - Gene FlowMovement of genes In and out of a Population.

Slide 78 - SpeciesOrganisms that can can mate, reproduce, have offspring

which can also reproduce (are fertile).

Slide 79 - What can prevent mating in a population?

•Geographic Barriers

•Reproductive Barriers

Barrier also means obstacle, wall, divide, etc.

Slide 80 - Geographic IsolationWhen a physical barrier (e.g. ocean)

separates/isolates a population.

Slide 81 - Example:

Marsupials in Australia

Slide 82 - Reproductive IsolationWhen organisms can no longer mate with other members.

Due to differences in mating behavior or species becomes so different genetically the sperm can no longer enter the egg.

Slide 83 - Rates of Speciation

Polyploidy

Gradualism

Punctuated Equilibrium

Slide 84 – PolyploidyInstant development of a new species in one generation!

Sometimes chromosomes do not separate like they should during meiosis, which is the process that creates egg and

sperm (gametes). If these gametes are fertilized, the offspring created can turn into an entirely new species because they have an abnormal number of chromosomes. Usually the

organisms dies, but sometimes it can survive as a new species.

Gametes

Zygote

Slide 85 - Gradualism:Gradual = Little change over time.

Species evolve slowly.Little change over a long period time.

Slide 86 - Punctuated Equilibrium:

Punctuate = BurstsSpecies evolve in quick bursts followed by

periods of no change.Big changes over a quick period of time.

Slide 87 - Patterns of EvolutionDivergent Evolution

Convergent Evolution

Slide 88 - Divergent Evolution:Diverge = move away

When species evolve from the same ancestor. They start as the same species and then diverge

(move away) from each other by developing different features.

Slide 89 - Convergent Evolution:Converge = Move Closer

When organisms evolve similar traits but did not come from the same ancestor. Even though these organisms fly, they

evolved from a different ancestor.