1. SPECIATION
Ch pp

2. Forming a new species
Speciation: forming a new species

3. Forming a new species
Speciation: forming a new species Species: a group of organisms that can mate and produce fertile offspring

4. Forming a new species Speciation: forming a new species
Species: a group of organisms that can mate and produce fertile offspring
1. same number of chromosomes
2. similar morphology (body
structure)

5. Disruptive Selection
Divergent evolution that most likely results in two new species

6. Mechanisms
Allopatric speciation caused by geographic isolation

7. Mechanisms Allopatric speciation caused by geographic isolation
physical separation of organisms (mountain, river forms etc)

8. Mechanisms Cont.
Sympatric Speciation due to reproductive isolation

9. Mechanisms Cont. Sympatric Speciation due to reproductive isolation
Live in the same area
Barriers to successful breeding

10. Mechanisms Cont. Two types of Sympatric Speciation Barriers
Prezygotic: before fertilization (i.e breeding times, mating calls etc.)

11. Mechanisms Cont. Two types of Sympatric Speciation Barriers
Prezygotic: before fertilization (i.e breeding times, mating calls etc.)
Postzygotic: after fertilization- infertile offspring (chromosome # doesn’t add up)

12. Rates of Speciation Gradualism: slow divergence (small changes)
Punctuated equilibrium: sudden shift in form (irregular)

13. Pre or Postzygotic?
offspring die young when two species of salamanders mate – they do not make it to maturity

14. Pre or Postzygotic?
Two different species of birds have different mating calls so they cannot recognize each other as mates

15. Pre or Postzygotic?
garter snakes that live in water and one on land cannot mate although they live in the same geographic area

16. Pre or Postzygotic?
mules are produced by mating a horse and a donkey, but mules are sterile and cannot breed

17. Pre or Postzygotic?
if gametes of red and purple sea urchins do not fuse, there will be no zygote produced

18. Pre or Postzygotic?
although some strains of cultivated rice can be cross-mated, after a few generations, sterile offspring are created