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WFC 151 SECOND MIDTERM FALL

2008

Name____________________________________________________

You have obtained a representative sample of the age structure of animals dying in a

population of the yew tern, a bird that nests in yew trees. Ages range from the very

young (age class 1) to the very old (age class 4); adults are age classes 2 and 3. Whattype of survivorship curve does the yew tern exhibit? Explain. (3 pts).

0

10

20

30

40

50

60

1 2 3 4

Age class

%ofsample

Steep slope = high mortality rate

Flat adulthoodSteep old

Type I high juvenile mortality rate with stable adulthood until older (senescence)

Type III b/c such high mortality

Type II - if all bars were equal

Generalist predators may respond functionally and numerically to increasing preydensity, but responses may be delayed because of time lags. Explain the causes of these

time lags. (6 pts)

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Some ecologists argue that Batesian mimicry should be considered as an interspecific

interaction in the same category as predation and parasitism. Explain the basis of this

argument. (4 pts)

The ham hawk is a predatory bird that feeds exclusively on wild pigs. It hunts by sitting

motionless on a concealed perch, waiting for a pig to wander by. Would piglets be morevulnerable than adult pigs to capture by the ham hawk? Explain. (3 pts)

Recent research suggests that the relationship between oxpeckers and ungulates may not

be mutualism, as previously thought. If so, then what interspecific interaction mightcharacterize the oxpecker/ungulate relationship? Explain. (2 pts)

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Below are the age structures of two populations. Describe what these data tell you about

the future size of each population (increasing, decreasing, no change) and why. (5 pts)

Social behavior is a trait found in many vertebrates, but how it evolved is unclear.

Briefly describe two hypotheses that explain the evolution of social behavior. (4 pts)

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Desert tortoises are rare, and one possible cause is competition with cattle for food.

Recently, however, Vern Bostick published a paper claiming cattle and tortoises do not

compete because they eat different foodscattle eat grasses and tortoises eat cattle dung.Bostick provided no data in support of this claim. You have been hired as an ecologist to

answer the following questions. (8 pts)

1. What is the name of the interspecific interaction between cattle and tortoises that

Bostick has described?

2. If, in fact, cattle eat grasses and tortoises eat dung, then is it true that they do not

currently compete for food? Explain.

Niche partitioning but dont conclude mutualismBut they could still be in competition

3. Describe the approach you would use to determine if cattle and tortoises are competing

for food.Character displacement analysis

See desert tortoises preference by separating the tortoise from cattle and making grassavailable