1. Speciation & Macroevolution

2. Species
What is a species?

3. Speciation
Microevolution –
Speciation –
Macroevolution

4. Reproductive Isolation
Classified as:
- Prezygotic mechanisms –
- Postzygotic mechanisms –

5. 5 Prezygotic Mechanisms
Groundhog – lives in fields at lower elevations
Marmot – lives in alpine meadows

6. Prezygotic Mechanisms Cont’d2.
Day and night-blooming cacti

7. Prezygotic Mechanisms Cont’d3. 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

8. 5 Prezygotic Mechanisms5.
Coral reefs release sperm and egg. Those from same species will fuse together

9. 3 Postzygotic Mechanisms
Different species may produce a hybrid –
Zygotic mortality –
2. Hybrid inviability –

10. 3 Postzygotic Mechanisms3. +
horse
donkey
Mule - infertile

11. Modes of Speciation
Allopatric Speciation –

12. 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?

13. Divergent Evolution
Divergent Evolution –

14. Convergent Evolution
Convergent Evolution –
Why would this occur?

15. 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

16. Rates of Evolution
Both theories are widely accepted

17. Co-evolution Co-evolution –
Plants require bees to disperse pollen. To attract bees –produce sweet nectar

18. Plants and Herbivorous Insects
Monarch caterpillar tolerates milkweed’s toxins and can store it in its tissues to make itself poisonous to others

19. Cumulative Selection

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