Speciation & Macroevolution

Species What is a species?

Speciation Microevolution – Speciation – Macroevolution

Reproductive Isolation Reproductive isolation – Classified as: - Prezygotic mechanisms – - Postzygotic mechanisms –

5 Prezygotic Mechanisms 1. 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 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 – 1.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

Does Evolution Always Produce Perfect Organisms? Any other examples we’ve discussed?