1. How does selection on stripped vs spotted snakes, and selection on reversing vs non-reversing escape tactics yield only two kinds of snakes:

1.         stripped -- non-reversing snakes and

2.         spotted -- reversing snakes?

Assume one gene controls color, and another controls behavior. Assume that the gene that controls color has two alleles (stripped and spotted) and the gene that controls behavior has two alleles (non-reversing and reversing) shouldn't we see at least four kinds?

1pt  for realizing that 4 types are born every season.  You should have named all 4 types

            3 pts for getting the mechanism correct.  The gist is that :

a.       Certain combinations of gene work well for cryptsis

b.      The non-cryptic combinations are eliminated by predators each year.

1pt for getting the details right.  The most important one is that this is correlational selection.   Points were also given if wrote about how another mechanism (such as assortative mating, genetic linkage) was not involved in creating the pattern of only 2 types being around.  It was important to realize that it was the action of selection creating the pattern, not linkage or assortative mating.

Below is an example of a good answer I got.  My comment is italized.

            Four kinds of snakes are born: stripped non-reversing, stripped reversing, spotted reversing, and spotted non-reversing.  The fact that 4 are born means that the genes are unlinked for color and movement.  The snakes do not breed assortatively.  The reason only 2 kinds are present is because they are exploiting a weakness in the predator’s vision.  Striped snakes who don’t reverse are cryptic.  So are spotted snakes that reverse.  The patterns and movement work together to confuse the predator.  Striped reversing snakes and spotted non-reversing snakes don’t enjoy the crypsis of the other two varieties and are picked off before they become adults.  So the predators are selecting upon the snakes.  (ie There is correlational selection for the right combos of genes).

2. What are the five levels of selection and what is the continuum along which we rank the various levels of selection?  Describe each level and try to give one real biological example of selection acting at each level.

The continuum is:

genes -> individuals -> kin -> groups -> species

This continuum is of more and more inclusive levels…individuals are composed of genes, kin of multiple individuals, etc.  It is important to realize that selection can act on multiple levels…thus the real story of what is going on can be complicated.  The examples like the t allele or relatedness in hymenoptera are brought up because these are instances where it seems like selection on one level is particularly strong.

Ideally you would have pointed out this continuum, which was the first part of the question.  

Below is a compilation of good answers that I got for the different parts of this question.  My comments are italized.  Each level was worth one point: .5 for naming it, and .5 for a correct explanation.

There are five levels of selection: genic, individual, kin, group, and species.  The continuum is that it starts at the level of the gene and gradually looks at larger and larger scales until reaching selection at the level of the species.

1. Genic Selection.  Selection at the fundamental unit of inheritance, the gene.  For example, the t allele in mice.  In males the t+ genotype has 85-95% t-sperm as opposed to expected 50:50 distribution.
2. Individual selection.  Selection which operates on the phenotype of individuals (ie not just a single gene, but the collection of genes that make up an individual)-this is classic natural selection as proposed by Darwin.  A real example is the gopher snake camouflage to behavior pattern. (ie the individual’s phenotype encompasses the multiple genes involved in behavior and pattern).
3. Kin selection.  Kin selection is selection on closely related individuals.  Kin selection is when an individual favors kin because of a higher than average coefficient of relatedness.  An example of this can be seen in Pfennig’s work on Tiger salamanders.  The amount of cannibalism was reduced as relatedness increased.
4. Group selection.  Much like individual selection (though usually weaker), group selection states that groups (of individuals) will increase in frequency.  Strong conditions are favored for selection at the level of the group including small groups and rapid generations.  For example, small groups of mice fixed for the t allele (ie genotype of all individuals in the group =tt) will have lower fitness (ie zero) than groups not fixed for the t allele.
5. Species selection.  One whole species is selected for over another species.  A real example is found during mass extinctions; species with smaller body size tend to survive mass extinctions more than species with large body sizes.