1. The Origin of Species
Chapter 24

2. Lunch Thursday
Speaker from Hawai'i Institute of Marine Biology!!

3. Biological species concept
A population whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot produce viable, fertile offspring with members of other species

4. Reproductive Isolation
Barriers that prevent two species from producing viable fertile hybrids

5. Pre-zygotic barriers Do not allow species to mate
Does not allow fertilization of eggs

6. Habitat Isolation
Species living in different locations may never meet and thus will never mate.

7. Behavioral Isolation
If mating behaviors are dissimilar among species, mating may not occur
Unique behaviors allow own species recognition

8. Temporal Isolation
When species mate at different times of year and are not able to breed with one another

9. Mechanical Isolation
The reproductive organs of two species are incompatible

10. Gametic Isolation
Gametes of 2 species may not meet due to chemical barriers preventing survival of sperm
Important to aquatic species

11. Postzygotic Barriers
Barriers that prevent the hybrid zygote from becoming an adult (or producing offspring).

12. Reduced hybrid viability
Genetic incompatibility may force miscarriage of hybrid embryo

13. Reduced hybrid fertility
Adult hybrid organisms can be sterile

14. Hybrid Breakdown
1st generation hybrids are viable and fertile but subsequent generations are not (may be sterile and feeble)

15. Limitations to the BSC
Does not account for asexually reproducing organisms, like bacteria
Does not account for interbreeding that may have happened in fossil species

16. Mode of speciation: Allopatric
Two species are separated by a physical barrier that causes them to be isolated
Over time, gene frequencies diverge due to selection, mutation, or genetic drift

17. Mode of speciation: sympatric
New species arise within parent population in geographically overlapping populations
In plants: Allopolyploidy (getting an extra set of chromosomes in cell division)
In animals: less common; subset of population becomes reproductively isolated b/c of switch to a habitat or food source not used by parent population OR sexual selection

18. Adaptive Radiation
Rapid evolution of many species from single ancestor when that ancestral species colonizes a new area or environmental changes cause extinctions and new ecological niches open up
(Changing to survive new habitations)- example: Hawaiian honeycreepers

19. Gradualism vs. Punctuated equilibrium
Gradualism: Gradual accumulation of small changes over time
Punctuated Equilibrium: long periods of stasis punctuated by rapid changes

20. Phylogeny and Systematics
Chapter 25

21. Cladistics and Phylogeny
Cladistics: study of relationships among organisms shown by common characteristics not found in ancestral group
Cladogram: diagram showing relationships among organisms

22. Cladogram