Population Genetics & Speciation

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Presentation transcript:

Population Genetics & Speciation

Populations Adapt – Individuals Can’t (They acclimatize) Fitness = ability to make a hereditary contribution to the next generation Populations Adapt – Individuals Can’t (They acclimatize)

Q: How do we see evolution? A: In populations Natural Selection acts on populations by changing the composition of the gene pool.

Gene Pool Gene pool refers to the total number of genes of every individual in a population. A large gene pool indicates high genetic diversity, increased chances of biological fitness, and survival.

Population Genetics Bell Curve – Ding! You’re most likely…just average!

Types of Selection – 3 Types Directional Stabilizing Disruptive

Directional Selection

Directional Selection

Directional Selection

Directional Selection

Stabilizing Selection

Stabilizing Selection

Stabilizing Selection NN nn Nn?

Disruptive Selection

Disruptive Selection

Disruptive Selection

Disruptive Selection

Types of Selection

Can selection eventually lead to new species?

What is a species? Morphological Species Concept: Focuses on morphology.

What is a species? Biological Species Concept – organisms that can successfully interbreed but can’t breed with other organisms

Species - Best Definition: A single kind of organism. Members are morphologically similar to each other and can interbreed to produce fully fertile offspring.

Speciation The process of species formation

Speciation – 2 steps Involves Isolation (Reproductive and/or Geographic) Then adaptation (Selection)

(Adaptation) (Isolation)

Isolation Geographic or Reproductive

Reproductive Isolation Prezygotic - barrier to creation of zygote Postzygotic – zygote formed, barrier/limitation related to development/reproduction/fitness

Reproductive Isolation – reduced fitness of hybrids Prezygotic or Postzygotic? Hybrids… Horse = 64 Donkey = 62 Mule = 63 Liger and Tiglon

Reproductive Isolation – Temporal Isolation Prezygotic or Postzygotic?

Behavioral Isolation Prezygotic or Postzygotic?

Prezygotic or Postzygotic?

Geographic Isolation

Allopatric Speciation “different homelands” Geographic Isolation

Allopatric Speciation “different homelands” Geographic Isolation

Sympatric Speciation “same homeland” Reproductive Isolation

Sympatric Speciation “same homeland” Reproductive Isolation