1. The whole-organism approach considers selection at the level of the phenotype. It considers interactions between trait combinations that arise from either selection on several genes or selection on many traits (arising either from one gene or many genes). Genic selection considers the impact of single alleles on fitness. There are many interactions between genes (e.g., epistasis) that cannot be encapsulated as a purely allelic effect. Likewise selection often arises on trait combinations (correlational selection on garter snake behavior and morphology) not just from the simple effect of alleles. These emergent properties of selection on gene interactions are not considered in the genic approach. (You may have also mentioned additive effects of many genes).

1. Whole organism approach breakdown.

6pts Definition of Genic Selection: for this you needed to show that you understood that genic selection is selection on the level of an individual gene (actually an individual allele). “Genic selection considers the impact of a single allele on fitness.”
Genic selection does not have to be selfish; it can benefit both the gene and the individual.

6pts Definition of Whole Organism approach: The whole organism approach looks at selection on the level of the individual. The whole-organism approach considers selection at the level of the phenotype. It considers interactions between trait combinations that arise from either selection on several genes or selection on many traits (arising either from one gene or many genes). It is important to realize that the whole organism approach can address specific phenotypic traits in an organism; is not limited to selection on the whole organism and every gene.

4pts The best argument for the whole organism approach has to do with emergent properties, that the phenotype/organism is more than just the sum of all the genes.
The argument is not individual vs genic levels of selection.

4pts You needed to reference some example of an emergent property of the organism. The best examples are epistasis, correlational selection, and polygenetic phenotypes/traits. All of these require interactions among multiple genes (not just one) to work. Gene by environmental affects affect both selection on a gene and selection on the individual. Thus gene by environmental affects aren’t a good example.

2. The male’s extended phenotype is any attribute outside of its physical body such as territory quality or ornaments hung around its territory (e.g., shrike skewering lizards on its turf). In a resource based mating system the male might be using a quality territory to signal to females that it is of superior fitness because it has good genes that allow it to hold such a territory (e.g., indirect effects on offspring). However, many attributes of a good territory provide direct benefits to offspring (e.g., Howard’s Bull frog example). Thus, the male may be signaling both good genes (indirect benefit) or direct benefits of a good territory. Indicator traits are aspects of the males phenotype that signal good genes (many forms of good genes are possible) to the female. In a non-resource based mating system, which we call a lek, there are not resources that are confounded with the male signals, thus, the males indicator traits are all that a female can choose from to gain, in this case, only indirect benefits for the females progeny. There may in fact be past resources that the male acquired that affect the male trait, but the female is likely still choosing the male on the basis of genes that allowed the male to acquire such resources.

2. This question was tricky in that it was a combination question. For instance, you needed to explain the extended phenotype in the context of a resource based mating system. Just talking about one or the other did not fully answer the question.

6pts Defining an extended phenotype, giving an example, and talking about the role of resources. Note that an extended phenotype is not just territory.

6pts Defining indicator traits, giving an example, and talking about a non-resource based mating system. Note that just defining indicator traits was not enough…you had to do so in the context of a nonresource based mating system.

4pts A female in a resource based mating system can choose either territory benefits (direct benefits) or good genes (indirect benefits) or both. It is not just direct benefits (see the sample answer). This tripped up many people. Remember that gathering resources (like dead lizards) can show hunting skill and thus good genes.

4pts In a nonresource based mating system, all the female has to choose is indirect benefits (good genes).

3. The fundamental assumption of optimal foraging theory considers that animals are omniscient (“all-knowing”). Thus, during the learning process, information required to make optimal foraging decisions is acquired and the animal is foraging at sub-optimal levels. This is a short-term effect. Once learning is complete, foraging can be optimal. In the case of memory, it may pose a real constraint on foraging. If the animal cannot retain all the information needed for foraging optimally then it is constrained. The example used in lecture derived a “memory constraint” explanation for risk-aversive behavior. If the bee could only remember the last flower (list length = 1), it would tend to avoid a flower color that ended up providing no reward in some cases (high variance), even if the average reward were the same or perhaps higher than a flower (with alternative color) that provided a more consistent reward (lower variance). It can be shown that if the bee had a list length of 2 or 3 it would have enough information to make the cognitive decision that the flowers were of equal value.

4. Sibs raised in different households do not have the confounding effect of common environment, which would tend to elevate the measured h2. Confounding environment biases h2 upwards which makes the estimate of h2 from sibs raised in different households better than sibs raised in the same household. There is still a problem of dominance variance that the different household design does not remove from full sibs. Dominance variance is found between full sibs only (not half sibs). In the argument, the fraternal twins not only share a common household environment but also a common womb environment, and dominance variance. The correlation between the adopted child and their unrelated sib is actually the correlation that is due to the common household environment.

5. Two critical conditions:
a) hybrid unfitness (e.g., some ecological reason)
b) assortative mating that allows pre-mating isolation to evolve
The process of reinforcement speciation (reproductive character displacement) causes the male trait to diverge more in sympatry than in allopatry (one species is exaggerated up the other is exaggerated down). Why? Males that have a more exaggerated trait than the allopatric populations are giving the female better information as to identity (e.g., species identity) than males in the population that are closer to the value observed in the other species. You must explain this as a process as I have done! Example: the fly catchers males have similar signals in allopatry (even though one is slightly larger in the white collar). However, in sympatry the collared fly catcher evolves a very wide signal while the other species of flycater evolves a duller or smaller white collar. Hybrids produce fewer surviving fledglings. Another example: frog calling between the ancestral and polyploid species of frog. One frog evolves a shorter call the other evolves a longer call. Hybrid unfitness arises from mixing different haploid genomes.

Points Breakdown: (out of 6, later scaled to out of 20, or 1:3.3)

Hybrid Unfitness (1)

Assortative mating (1)

Evolution of reinforcement/character displacement (1) (got full credit if this was explained rather than use of term)

For species recognition, not req'd in allopatric situations (1)

Example: (0 pts) if example of sympatric speciation through a mechanism unrelated to mate choice; OR (1 pt) for example of sympatric speciation due to mate choice-- the 2 conditions are fulfilled; OR (2 pts) for example of sympatric speciation w/mate choice AND reproductive char. displacement.

6. Orientation is the ability of animal to move around its local area using some “relative” cues. For example, scout bees use a sun compass to orient the other foraging bees to flowers by the means of a waggle dance. The dance describes the distance from the hive (number of circles) and the direction of the waggle relative to polarizing light from the sun describes the direction to the flower. There is NO sense of global location. In contrast, an animal with true navigational sense has a cognitive picture of where they are located in the world. Many migrating birds actually have a sense of where they are located (migrating birds use a number of cues to figure out this information, mention one map sense used and that is enough). The only way to truly tell the difference between the two is to translocate an animal and see if it re-establishes a new (and correct heading) back to its target location (e.g., migratory grounds).

Points Breakdown: (out of 6, later scaled to out of 20, or 1:3.3)

Orientation: (1 pt) using environmental cues to move around; AND (1 pt) relative to a fixed location/ local use only; AND (1 pt) example of an animal using dead reckoning.

Navigation: (1 pt) cognitive sense of global position; AND (1 pt) use of absoulte, not relative, cues; AND (1 pt) example of either the test for navigational ability OR an example of an animal navigating by an absolute cues (internalized star maps, for example)