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horse. donkey. Speciation. mule. Speciation. A. B. baby. Defined : evolution of new species from an existing species Species : group of organisms that can interbreed and produce fertile offspring 5 factors that lead to evolution Natural Selection Gene flow Mutations Sexual selection

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Horse

horse

donkey

Speciation

mule


Speciation

Speciation

A

B

baby

  • Defined: evolution of new species from an existing species

  • Species: group of organisms that can interbreed and produce fertile offspring

  • 5 factors that lead to evolution

    • Natural Selection

    • Gene flow

    • Mutations

    • Sexual selection

    • Genetic drift

A

B

baby

A

B

Sterile baby


Gene flow migration

Gene Flow(Migration)

  • Defined: Movement of alleles from 1 population to another

    • Increases variations in a population

    • Keeps differing populations similar

  • If gene flow is prevented

    • No variations (alleles) exchanged

    • Populations are isolated

    • Organisms adapt to their own environment

    • Can lead to speciation


Reproductive isolation

Random DNA mutations

Random DNA mutations

Reproductive Isolation

Different predators

Different predators

Different resources

Different resources

  • When populations are isolated for a long time…gene flow stops

  • When populations can no longer mate or no longer reproduce fertile offspring

  • Final step in the development of a new species

  • Geographic Isolation:

    • Organisms isolated by geographic barrier


Horse

Kaibab Squirrel (Grand Canyon)


California salamanders evolution in action

California Salamanders: Evolution in Action


Horse

Ancestral salamanders

B

A

One species

One species


Famous fruit fly experiment

Fruit flies of the same species were placed into two separate cages

Famous fruit fly experiment

Once isolated, the 2 groups were fed different types of food

Although isolated, the flies continued to live and reproduce for many generations

When brought back together most separated during reproduction.


Reproductive isolation1

Reproductive Isolation

  • When populations are isolated for a long time…gene flow stops

  • When populations can no longer mate or no longer reproduce fertile offspring

  • Final step in the development of a new species

  • Geographic Isolation:

    • Organisms isolated by geographic barrier

  • Behavioral Isolation

    • Organisms isolated by differing mating rituals

If the mating calls do not attract each other, will they reproduce?

Is gene flow stopped?


Birds of paradise

Birds of Paradise


Human mating rituals

Human mating rituals


Human mating rituals1

Human mating rituals


Human mating rituals2

Human mating rituals


Human mating rituals3

Human mating rituals


Human mating rituals4

Human mating rituals


Human mating rituals5

Human mating rituals


Reproductive isolation2

Reproductive Isolation

  • When populations are isolated for a long time…gene flow stops

  • When populations can no longer mate or no longer reproduce fertile offspring

  • Final step in the development of a new species

  • Geographic Isolation:

    • Organisms isolated by geographic barrier

  • Behavioral Isolation

    • Organisms isolated by differing mating rituals

  • Temporal Isolation

    • Organisms isolated by differing times of reproduction

If one group mates during the spring…

Is gene flow stopped?

And the other mates during the fall…


Genetic drift

Genetic Drift

  • Defined: Changes in allele frequencies due to chance

    • NOT natural selection

  • The Bottleneck Effect

    • Results in a loss of genetic variation (alleles)

    • More likely in smaller populations

    • Example: Natural disaster

      • Pre-forest fire: Green is best adapted (blend better)

      • Post-forest fire: Brown more likely to reproduce

    • Survival UNRELATED to adaptations


Review

Review

  • What is speciation?

  • What leads to speciation?

  • What is gene flow?

  • What happens if gene flow is prevented?

  • How are temporal, behavioral, and geographic isolation different?

  • How are temporal, behavioral, and geographic isolation similar?

  • What are the 5 factors that lead to evolution?


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