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170 points - 5 points for name on top of each page.
40 pts. 1. Define and provide an example of each of the following (4 pts. each):
a. search image
a hypothetical mental image
(picture) used by predators to search specifically for cryptic,
common, edible prey, e.g., specialization on particular species
of potential prey by tits, blue jays finding moths; see Midterm
I
b. parental investment
the risks, time and energy a parent expends on one offspring that reduce its ability to produce additional offspring in the future or care for other current offspring, e.g., nursing a calf over winter rather than breeding in fall in ungulates
c. spermatophore
a packet of energy and nutrients accompanying sperm that is a food resource to the male's mate, e.g., male Mormon crickets release spermatophores that are about a fourth of their weight.
d. epigamic selection
The role female choice of mates
plays in the evolution of male mating success, e.g., female
choice of mates on a lek.
e. reciprocity
A helpful action by a donor to
a recipient that is at least a minor cost to the donor and a benefit
to the recipient that is repaid by the recipient at a later time,
e.g., bollid sharing in vampire bats.
f. cooperative breeding
Breeding, social systems in which
adults forego breeding and help breeding pairs, e.g., helpers
in Florida scrub jays.
g. contest competition
Access to limiting resource is
affected by agonistic interactions with other individuals, e.g.,
agonistic interactions at bird feeders that affect rates of food
intake.
h. indirect selection
Selection on an individual's ability to aid relatives and enhance their inclusive fitness; selection on the part of an individual's inclusive fitness that is due to production of nondescendent kin, e.g., the extra breeding success of a pair that is due to a helper is that helper's indirect fitness.
i. runaway sexual selection
Evolution of male secondary sexual
characteristics that is based on female choice of traits that
are unrelated to male's fitness--arbitrary choice; e.g., female
choice of longer swords in the swordtail.
j. resource defense polygyny
Males gain access to females
by controlling certain vital resources that females require, e.g.,
male territoriality in red-winged blackbirds, bobolinks.
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(20 pts.) 2.
Define and provide an example of a lek. In general, what are
the general patterns of variance in (a) male breeding success
and (b) female breeding success on a lek? Explain what is meant
by the "lek paradox" and provide at least one reason
why there may be no paradox.
A lek is a traditional display
site where males gather to defend small territories that lack
resources useful to females, which nevertheless visit the site
to mate. Examples of lek breeding species include Uganda kob,
Sharp-tailed grouse, Fallow deer.
Variance in male breeding success
can be extremely high with one to a few males having most of the
mating success. Female breeding success will vary much less as
each probably mates successfully on the lek and then has a more
or less successful breeding attempt.
The paradox of the lek is that
females seem to be highly choosy and male mating success is highly
variable, yet all displaying males are offspring of many generations
of successful males and thus probably differ little genetically
(and all that females receive from the males is their genes).
Female choice may depend on ecological
factors, e.g., the safest place on the lek to avoid predators;
all females may be able to make appropriate choices. Even if
genetic variability is reduced, some variability is present due
to recombination (and perhaps mutation) so some variants may result
in better condition. Thus females should remain choosy because
even slight differences in male genotypes may influence fitness
of their offspring.
(15 pts.) 3. Explain why bridewealths are provided in many human societies and dowries in some societies. Does this pattern provide a basis for understanding why the bride's family typically pays for the cost of a wedding in our society?
Bridewealths (where the groom
provides gifts/payment to the bride's family) show that females
are a scarce resource in many human societies. Bridewealths are
most common in societies in which there is "general polygyny"
(>20% of married men have >1 wife), i.e., within societies
where male competition for mates is high and unmarried females
are a scarce resource.
Dowries (where the female's family
provides gifts/payment to the groom) are relatively rare but are
most prevalent in monogamous societies with a high degree of social/economic
stratification; they provide a means for a bride to increase
not only her fitness, but also that of future generations.
Perhaps since we live in a monogamous
system and there is high variability in male wealth, the tradition
of the bride's family paying for the cost of the wedding has evolved
from traditional dowry payments.
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(20 pts.) 4. Outline the types of mating systems that can be found within even a single population of the dunnock (hedge sparrow) and explain why each type occurs.
Females arrive first in the spring
and establish breeding territories. Females may defend small
rich territories or large areas of relatively low prey density.
If a male is able to successfully defend one female's territory
and exclude all other males, MONOGAMY will result; this usually
occurs on small territories. In some instances resource abundance
is so high that female territories are very small and a male may
be able to successfully defend and exclude all other males from
the territories of two breeding females, resulting in POLYGYNY;
this is rare and resisted by females. On larger territories,
males sometimes are unable to exclude all other males. If a monogamous
male is unable to exclude an intruding male, the female will court
the intruder and copulate with him, resulting in POLYANDRY (males
who copulate with a particular female will help feed her young).
POLYGYNANDRY can result if two adjacent females are able to successfully
solicit copulations from each other's mate or if an intruding
male successfully establishes alliances with the females on a
polygynous male's territory. Males who mate with a female help
feed that female's nestlings.
(20 pts.)
5. In some fish species individuals change sex from male to female
and in others individuals change sex from female to male. Provide
examples of each and explain, using appropriate graphs, why each
of these types of sex change occurs.
Protandry: since sperm is relatively cheap to produce compared to eggs, even a small male can produce enough sperm to fertilize all of a female's eggs; fecundity of males increases little as size increases. Female fecundity increases with body size in fishes. If the system is monogamous it is best for both male and female if the female is larger. In the monogamous Anemonefish individuals hatch as protomales and the largest will turn into a male if the male is removed or dies. If the female dies and the male is the largest in the area, he will turn into a female. This insures maximum fecundity for the breeding pair because fecundity of both is limited by female size and egg-laying potential.
Protogyny: if male fecundity is affected by contest competition and only the largest males breed, male fecundity may be zero or low until the male is larger than all other males. In such cases it would be better to start life as a female and switch only when larger and more dominant than all others in the area--blue-headed wrasses are a prime example.
For graphs: see lecture handout
on this subject.
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(25 pts.) 6.
Outline the basic life cycle of a paper wasp (yellowjacket) in
the Fairbanks area. Use appropriate diagrams to show coefficients
of relatedness of (a) workers to their sisters (assuming there
is only one breeding queen who had mated with only one drone)
and (b) workers to their own offspring (if workers could leave
the hive and breed successfully). Note that the relatedness of
workers to nephews and nieces produced by sisters is half of the
relatedness of workers to their sisters, which you calculated
in (a) above. Why do these calculations show that indirect fitness
cannot account for the nonbreeding status of typical workers?
What seems to be the best reason for a nonreproductive worker
caste in paper wasps?
Could start at any time of year; I'll start in late summer. In late summer queens and drones emerge from the nest and disperse and mate. Drones then die. Queens overwinter solitarily in relatively warm microhabitats, e.g., leaf litter under snow. In spring queens emerge and start nests, usually solitarily, but sometimes two or more "littermates" will start a nest together. We'll assume a single female starts her nest. She lays several fertilized eggs in a small comb; this is the first round of daughters and all will be workers. They then help enlarge the nest and defend it as she lays several additional rounds of workers through mid-summer. In late summer she lays eggs that will become queens and drones, repeating the cycle started above; the old queen and all the workers die at freeze-up.
Use a diagram to show relatedness of a worker to a full sister (either worker or queen); r=0.75. Worker to daughter: r=0.5; worker to son: r=0.5 (note that son receives genes only from mother and he has no father, but a particular allele in mother has only a 50% chance of going to a particular son).
These calculations show that a worker would be more closely related to her sons and daughters (r=0.5) than she is to her nieces and nephews (r=0.375, as noted above); therefore, she would be better off if she could reproduce.
Best reason? workers are suppressed
reproductives; they have no option for direct fitness. Therefore,
they should maximize indirect fitness, which they can do by protecting
mother and sisters and brothers and helping the mother raise more
reproductive offspring. Other reasonable arguments are also acceptable.
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(15 pts.) 7.
Discuss one example of an alternative mating strategy which is
maintained by frequency dependent selection and another which
is represents a conditional strategy. Explain how you can differentiate
between the two.
Jacks and hooknoses in coho salmon
and marine isopod discussed by Alcock are two appropriate examples.
In both cases strategies are fixed by the time the males have
matured (genetically determined in the isopod). A particular
phenotype does well when its phenotype is relatively rare in the
population and less well when its phenotype is abundant, resulting
in a stable equilibrium of relative frequencies of phenotypes.
Conditional strategy is exemplified
by coursing and blocking in bighorn sheep, where the largest most
dominant rams tend estrous females and subdominant and small rams
adopt the other strategies and have low success, making the best
of a bad lot. Small rams cannot tend because they cannot compete
with large rams.
Generally individuals adopting
a conditional strategy will have lower breeding success than those
adopting the "preferred" strategy and will switch strategies
if given the opportunity; both characteristics distinguish conditional
strategies from frequency dependent selection.
(10 pts.)
8. Why are polygamous marriages prohibited by law in our
society?
There are several possible and plausible answers to this. The question can be considered in relation to either polyandry or polygyny vs. monogamy. One possibility: with monogamy all or most males and females will find mates and variance in breeding success will be minimal. With polygyny male competition for females is intensified, perhaps leading to increased violent crime and rape. Since polygyny is widespread in human societies, moral codes, religious beliefs and legislation in our society all seem to promote good of the group over maximizing individual fitness.
Many different answers are possible,
but saying its because of our religious beliefs or moral codes
is not sufficient; I'd like you to challenge yourself to think
in evolutionary terms why our society has those religious beliefs
and moral codes.
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