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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

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




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 separate cages

  • 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 separate cages


Human mating rituals
Human mating rituals separate cages


Human mating rituals1
Human mating rituals separate cages


Human mating rituals2
Human mating rituals separate cages


Human mating rituals3
Human mating rituals separate cages


Human mating rituals4
Human mating rituals separate cages


Human mating rituals5
Human mating rituals separate cages


Reproductive isolation2
Reproductive Isolation separate cages

  • 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 separate cages

  • 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 separate cages

  • 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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