Speciation & Macroevolution

Species What is a species?

Speciation Microevolution – Speciation – Macroevolution

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. flowers’ particular structure means that only insects of certain size and behavior can effect pollination. The lip or labellum of these orchids is inflated into a sac- like structure and this floral morphology is key to their mode of pollination. The labellum has an upper orifice with a smooth margin that affords no purchase and an infolded margin and side lobes that block escape by visiting insects should they fall into the pouch. Insects are generally unable to exit by the route in which they entered. In attempting to escape, insects are guided to climb a particular interior portion of the pouch and then under one of two anthers and out through one of the basal orifices. If they are of the correct size they receive a smudge of granular pollen on the dorsum and may transfer the pollen to the stigma of the same flower or another plant. 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?