1a) The h2 estimates for sibs raised in different households are preferred to sibs raised in the same household because the additive genetic component of ~30-35% of the phenotypic variance (key for h2 estimates) is confounded with common household effects (~5-15%) in the case of same-household sibs. Raising sibs in randomized households (or different households) eliminates this confound. (4 pts)
b) The separation-of-sibs-at-birth protocol does not eliminate the impact a common womb (2 pts) or dominance variation (2pts), another genetic component. Full sibs share dominance genetic variation (Vd).
c) The factor discussed in b is directly related to why progeny can also be completely unrelated. Sibs can share 0 alleles, 1 allele (or 2 alleles, which generates Vd). The pedigree diagram below shows how this can come about. In the pedigree the alleles are labeled uniquely in each parent and all possible outcomes are shown. A more than perfect answer would also state that the cases where sibs share none or share two alleles occurs with probability ¼, while the case with one allele occurs with probability ½. Your answer should give some kind of reason Òfor half related on averageÓ such as progeny get half the genes from each parents and this leads to on average half-relatedness, but the diagram shown below explains precisely why the ½ sharing comes about. For complete points you need to report the probability of being dissimilar and half similar (4 pts)
2) Social hymenoptera are more predisposed to altruism
because of their haplodiploid mating system in which reproductive females are 2N
and reproductive males begin life as N (unfertilized zygotes from the mom).
Below I diagram a social hymenoptopera and below that diagram a regular diploid
(2N) organism and the salient feature to explain is that sires in social
hymenoptera pass on exact copies to each daughter. These daughters then are on average ¾ related [e.g., (1+1/2)/2].
Therefore a daughter that is a queen is ¾ related to her sisters that
might end up as her workers and this enhances overall gene sharing, r the
coefficient of relatedness. LetÕs look at HamiltonÕs equation.
The question asks about altruism so you have to discuss the benefits and costs of altruism, which is a benefit to fitness of related individuals (i.e., summed across all of them, e.g., Windirect below, the sum is over all relatives!! affected by the behavior) multiplied by the coefficient of relatedness of each relative (e.g., rk). This benefit is at the expense of a cost to individual fitness (Wdirect below). Various forms of HamiltonÕs Equation will be accepted including the inequality version or the version that discusses Inclusive fitness in terms of direct versus indirect fitness. These two versions are pasted below (only 1 is required). Finally, by increasing r, haplodiploidy increases the benefit term making it more likely that benefits > costs.
While I described the terms above, it is always safest to make sure you define them in some way. You could define the terms like so avoiding much of the writing above, but you still need the key points in bold. Here are precise definitions (note this is somewhat redundant with the paragraph above):
Thus, a perfect answer need not include both the paragraph and the definitions but I would have to make sure my paragraph to the answer includes short definitions of the terms parenthetically, where I talk about each term. I went back and did this in my paragraph. Thus, describing the equation is sufficient.
3abc)
a,b,c each worth 4 pts. (1 pt. for correctly labeled axes, 1 pt. for graph, 2 pts. for explanation)
This should be simple to explain in one fell swoop. Female fecundity (the dashed lines) increase linearly with fitness in each panel. The lines for male fecundity differ in each panel and three possibilities are shown.
The brief sentence mentions female fecundity at least once in your answer, and then explains that females will transform to male in the case of large size enhancing male fitness more than female fitness (protandry), or the converse case, where say a sneak strategy does quite well if small (protogyny). The ÒNull hypothesis caseÓ (e.g., 1st panel) is that the sexes do not differ in size-dependent fitness and thus, you might find no sex change (and of course it would likely be a dioeceous species).
d) The three hormones are quite simple, E (estrogen), T (testosterone) and 11-keto T. The E levels are hi medium and low in females, Intermediate phase males and Terminal phase males, respectively. While T levels start out low and go higher in IP males and then higher still in TP males. 11-keto appears to go high in IP males and stay high. (Slightly shorter versions of this story will be fine as long as the key details are present). While a diagram was not required an answer with a diagram was of course appreciated by your TA J.
4a) The male trait is some ornament that is used to attract females, and the ornament of course might vary in size.
b) The female trait is female preference for the large ornament, but this preference varies in intensity among females (e.g., you could have random choice versus highly choosy females)
IN a and b you had to
talk about different types (e.g., variation is required for selection). If you
just state Òmale ornamentÓ, Òfemale preferenceÓ you are not giving us enough
information.
c)
Two versions can be supplied but the table is to be preferred (the alternative is a mating diagram, used in class):
This table clearly shows a bias in the C pairing up with E and N going with + types. This sets up a situation in which a genetic correlation forms (optional point). The key is to state that non-random combinations of male and female traits are favored and that choosy mainly goes with Elaborate. If you state that E traits are favored in males and choosiness is favored in females without linking the two, you have missed the key point. Therefore, it is the combination of EC that is favored overall, as this has higher fitness in males and female lineages (and higher fitness in the sons of choosy females <- optional). You might phrase this as the ÒinteractionÓ, etc.
You could do this with a mating diagram but you have to point out these key facts in words regardless.