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Speciation & Macroevolution. Species. What is a species?. Speciation. Microevolution – Speciation – Macroevolution. Reproductive Isolation. Reproductive isolation – Classified as: - Prezygotic mechanisms – - Postzygotic mechanisms –. 5 Prezygotic Mechanisms.

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Speciation & Macroevolution

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Speciation & Macroevolution


Species

What is a species?


Speciation

  • Microevolution –

  • Speciation –

  • Macroevolution


Reproductive Isolation

  • Reproductive isolation –

    Classified as:

    - Prezygotic mechanisms –

    - Postzygotic mechanisms –


5 Prezygotic Mechanisms

Groundhog – lives in fields at lower elevations

Marmot – lives in alpine meadows


Prezygotic Mechanisms Cont’d

2.

Day and night-blooming cacti


Prezygotic Mechanisms Cont’d

  • 3.

  • 4.

Insects of a particular size and shape can enter the Pink Lady Slipper’s sac to get pollen


5 Prezygotic Mechanisms

5.

Coral reefs release sperm and egg. Those from same species will fuse together


3 Postzygotic Mechanisms

Different species may produce a hybrid –

  • Zygotic mortality –

    2. Hybrid inviability –


3 Postzygotic Mechanisms

3.

+

horse

donkey

Mule - infertile


Modes of Speciation

Allopatric Speciation –


Modes of Speciation

Sympatric Speciation –

Frogs live in same habitat – but 1 is diploid, other is tetraploid

What does that indicate about their evolutionary relationship?


Divergent Evolution

Divergent Evolution –


Convergent Evolution

Convergent Evolution –

Why would this occur?


Rates of Evolution

  • Theory of Punctuated Equilibrium –

    • - Species evolve drastically in rapid bursts of change (evolution time) followed by long periods of no change

    • - Transition fossils are rare

  • Theory of Gradualism –

    • - Many small changes accumulate over time to produce a different species

    • - Gradually become distinct from parent generation

    • - Transition fossils are common


Rates of Evolution

Both theories are widely accepted


Co-evolution

Co-evolution –

Plants require bees to disperse pollen. To attract bees –produce sweet nectar


Plants and Herbivorous Insects

Monarch caterpillar tolerates milkweed’s toxins and can store it in its tissues to make itself poisonous to others


Cumulative Selection


Does Evolution Always Produce Perfect Organisms?

Any other examples we’ve discussed?


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