Final Exam Study Questions.
1. It is said there is a two-fold disadvantage of sex. Explain.
advantageous genotypes don't true breed ie. not all offspring have the
reduced reproductive output (50% of offspring cannot bear children)
2. Asexual reproduction, over the longer term, is disadvantageous. What phylogenetic
evidence supports that hypothesis.
- we only see asexual organisms very rarely
- asexual species only exist of very recent origin
- no example of a species that reverts back to sexual (maybe they die out too
3. What is the Red Queen’s hypothesis, and how has it bee addressed experimentally??
- "you need to keep running to stay in the same place"
- need to constantly be generating new genetic combinations to deal with a
constantly changing environment
- this has been tested experimentally with caenorhabditis
- faster tracking of shifting phenotypic optimum
Population of worms
4. Sex ratio’s are most often 50:50. How did R.A. Fisher explain this? When might a male-
biased sex ratio evolve by selection?
rarity is always favored, this is called frequency dependant sex determination. the sex that
is of a lower frequency will be favored by sselection because it will have a higher
reproductive output. if there are a lot of males and a few females, an average female will
have a better chance of mating, on the other hand if a male is rare, he will on average have
more kids. these to opposing selections will push the frequency of the less common sex
higher, closer to 50%. the 2 opposing selections will be in equilibrium and maintain the
ratio. some cases a male will be favored when only few individuals can be produced in and
environment with multiple females, like in parasatoid wasps. also in ant populations when
there are multiple queens. Whenever there is a population with a female biased sex ratio,
selection will favor the development of a male biased sex ratio. 5. Distinguish between sexual selection through male-male contests, and through female choice.
6. Explain the ideas of a) sensory bias and selection for male traits, b) runaway sexual selection
of male traits and female choice, and c) the ‘good genes’ model for evolution of male traits and
7. Aggressive competition can be favored by selection, even if the spread of an aggression gene
lowers population mean fitness. Explain.
8. What are the key features of cooperatively breeding species? What additional features are
found in eusociality?
Were more then 2 individuals display parental-like behavior towards a offspring
Helpers provide a resource or a service to offspring that are not their own, often a siblings
or an older offspring
Helpers can face a fitness cost for helping
Helpers can go on to reproduce later
Additional features that are found in eusociality are a joint defensible nest and the fact
that helpers do not reproduce
9. What genetic features of the hymenoptera have bee thought to predispose them to the
evolution of eusociality?
10. Define each of the following
The Typological Species Concept
The Phylogenetic Species Concept
The Biological Species Concept (What makes it biological?)
typological species concept: a group of similiar individuals that conform to an ideal
phylogenetic Species concept: a cluster of indivuduals that are distinct from other
clusters, all descendants from a common ancsetor
Biological species concept: a group of interbreeding or potentially interbreeding
populations that are isolated from other such groups reproductively. This can be due to
many different reasons. 11. What are the four geographical modes of speciation?
allopartic speciation: a new physical barrier arieses that leads to no gene flow
peripartic speciation: a new population of individuals is created that doesnt have gene
flow with the original
parapartic speciation: a range expands with strong divergent selection and limited gene
sympatric speciation: sexual isolation in the same geographic area in an initially random
12. Define and give an example for each
Ecological Isolation: different time or place of mating like spring vs fall cricket
Sexual Isolation: different mating preferences lacewing songs
Mechanical or Gametic incompatibilitie: when the structure of the sex organs don’t allow
meeting of the gametes or when the gametes cannot fuse. Different drosophila species with
different penis styles
Hybrid Sterility: when the hybrid is sterile like a mule
Hybrid Inviability: when there are developmental issues and the offsping cannot survive like
sunfish species intermating
ecological isolation: where gene flow is restricted due to different times of mating or
different areas of mating. ex is the spring field cricket and the fall field cricket
sexual isolation: is when gene flow is restricted because of differences in mating