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Biology Final Exam with Answers
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Killer Whale
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1.   Which of the following would be an example of secondary succession?
A.   recovery of a grassland from a prairie fire
B.   conversion of forest to a pond due to beaver activity
C.   decimation of a population of oak trees due to disease
D.   answers A and B

2.   Assume that you have been studying a population of cattails at the edge of a pond. After 10 years of observations, you notice that the population has remained steady. What is the most likely explanation?
A.   The birth rate and death rate are both increasing at the same rate.
B.   The pond is drying up.
C.   The carrying capacity of the pond has been reached.
D.   Nutrient levels in the pond are fluctuating.

3.   Assume that each individual of a particular species produces 10,000 seeds over its lifetime. If the population size is stable (not increasing or decreasing), approximately how many of those seeds will (on average) survive to reproduce?
A.   1
B.   10
C.   1000
D.   There is no way to know.

4.   Ecologists generally separate organisms in an ecosystem into three categories (producer, consumer, decomposer) based on
A.   how they obtain their energy.
B.   how rapid their metabolism is.
C.   the rate of succession in the ecosystem.
D.   the size and complexity of the ecosystem.

5.    A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations best describes this observation?
A.   The herbicide company lost its triazine formula and started selling poor-quality triazine.
B.   The herbicide caused the pigweed to mutate, creating a new triazine-resistant species.
C.   Triazine-resistant pigweed has less efficient photosynthesis metabolism.
D.   Only triazine-resistant weeds survived and reproduced, so each year more pigweed was triazine-resistant.

6.   A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed, no matter how often he applies triazine. Which of these actions is most likely to solve the farmer’s problem?
A.   buying triazine from a different company
B.   trying a different herbicide
C.   increasing the amount of triazine he puts on his fields
D.   adding triazine more often to his fields

7.   Parasitic species tend to have simple morphologies. Which of the following statements best explains this observation?
A.   Parasites are lower organisms, and this is why they have simple morphologies.
B.   Parasites do not live long enough to inherit acquired characteristics.
C.   Simple morphologies have been naturally selected for in most parasites.
D.   Parasites have not yet had time to progress, because they are young evolutionarily.

8.   Why are some traits considered vestigial?
A.   They improve the fitness of an individual who bears them, compared with the fitness of individuals without those traits.
B.   They change in response to environmental influences.
C.   They existed a long time in the past.
D.   They are reduced in size, complexity, and function compared with traits in related species.

9.   An example of a vestigial trait in humans is:
A.   kidneys
B.   cataracts
C.   goose bumps
D.   There are no vestigial traits in humans.

10.   Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 4 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg model?

A.   f(A1) = 0.9996, f(A2) = 0.0004
B.   f(A1) = 0.9984, f(A2) = 0.0016
C.   f(A1) = 0.9800, f(A2) = 0.0200
D.   f(A1) = 0.9604, f(A2) = 0.0392
E.   f(A1) = 0.9200, f(A2) = 0.0800

aa = A2A2= 4/10,000 = 0.0004
A2 = 0.02

11.   For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet?
A.   no selection
B.   no genetic drift
C.   no gene flow
D.   no mutation
E.   random mating

12.   What does it mean when an allele reaches “fixation”?
A.   It is eliminated from the population.
B.   It has a frequency of 1.0.
C.   It is dominant to all other alleles.
D.   It is adaptively advantageous.

13.   Male turkeys have a snood, which is a flap of skin that hangs across their beak. Snood length is negatively correlated with parasite load (e.g., males with longer snoods have fewer parasites), and females prefer to mate with long-snooded males. This is an example of:
A.   the fundamental asymmetry of sex
B.   sexual selection via female choice
C.   sexual selection via male-male competition
D.   a genetic marker

14.  Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. The dominant allele (T) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined (see chart) and used to determine the allele frequencies in the population.
Genotype Frequencies   Allele Frequencies
TT   Tt   tt   T   t
560   280   160   0.7   0.3

Is this population in Hardy-Weinberg equilibrium?  SHOW ALL YOUR MATH!

F(T) = [(560x2) + 280]/2000 = 0.7      f(t) = 0.3

Exp. #: TT = 490      Tt = 420      tt = 90

X2 = 111; this population is NOT in HW

A.   yes
B.   No; there are more heterozygotes than expected.
C.   No; there are more homozygotes than expected.
D.   More information is needed in order to answer this question.

15.   The researchers had already noted that negligible mutation and migration existed in this milkweed population, and the butterflies that pollinate these plants are not affected by the toxin. Which of the following would be a logical conclusion about this milkweed population based on your answer to question 14 above?
A.   Genetic drift and selection are negligible.
B.   There is either a heterozygote advantage or inbreeding depression.
C.   There is either directional selection or sexual selection.
D.   There is either disruptive selection or genetic drift.
E.   There is either stabilizing selection or gene flow.

16.   Mutation is the ultimate source of genetic variability. Why is this statement correct?
A.   DNA polymerase (the enzyme that copies DNA) is remarkably accurate.
B.   “Mutation proposes and selection disposes.”
C.   Mutation is the only source of new alleles.
D.   Mutation occurs in response to natural selection. It generates the alleles that are required for a population to adapt to a particular habitat.

17.   Male reproductive success, measured as the number of offspring surviving to adulthood (pupating), is found for two closely related beetle species and graphed below. Which of these statements would you expect to be true of sexual dimorphism in the two species?
A.   Species A should have greater sexual dimorphism than species B.
B.   Species B should have greater sexual dimorphism than species A.
C.   Species A and B should have about equal amounts of sexual dimorphism.
D.   Neither species should show any sexual dimorphism.

18.   Genetic diversity is required for natural selection to act, but natural selection can reduce or eliminate diversity. What process can restore genetic diversity to a population?
A.   genetic drift
B.   mutation
C.   sexual selection
D.   stabilizing selection

19.   Which of the following biological processes causes adaptation?
A.   mutation
B.   migration
C.   natural selection
D.   genetic drift
E.   all of the above

Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.

20.   What keeps the two populations separate?
A.   temporal reproductive isolation
B.   lack of hybrid viability
C.   gametic barrier
D.   spatial reproductive isolation
E.   behavioral reproductive isolation
21.   The two populations (in question above) are:
A.   different subspecies, under the morphospecies concept
B.   different species, under the biological species concept
C.   different species, under the phylogenetic species concept

22.   Most causes of speciation are slow, except:
A.   polyploidy
B.   vicariance
C.   colonization
D.   natural selection

23.   Which of the following statements explains why animals are less likely than plants to speciate by polyploidy?
A.   Animals rarely self-fertilize, so diploid gametes are much less likely to fuse.
B.   Animals have better mechanisms for repairing chromosomes than plants have.
C.   Animals are better at recognizing appropriate mates.
D.   Animals are more mobile, so populations get separated far less often.

24.   Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of pairs of closely related tree frogs in South America. If reinforcement of prezygotic isolation is occurring, what would you expect if you compare the calls of the two species in zones of sympatry and allopatry?
A.   Calls would be about the same in both areas.
B.   Calls would be more similar in areas of sympatry.
C.   Calls would be more different in areas of sympatry.

25.   Why are genetic isolation and genetic divergence occurring in soapberry bugs, even though populations occupy the same geographic area?
A.   Members of the different populations feed and mate on different types of fruit.
B.   One population recently became tetraploid, and hybrid offspring cannot undergo meiosis correctly.
C.   A vicariance event occurred when nonnative host plants were introduced.
D.   Beak length has changed due to disruptive selection.

26.   When the ranges of different species meet, a stable “hybrid zone” occupied by hybrid individuals may form. How is this possible?
A.   Hybrid individuals may have intermediate characteristics that are advantageous in a given region, relative to traits in the different species.
B.   Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species. Allopolyploidy forms new species.
C.   Hybrid individuals may have reduced fitness and thus be strongly selected against.
D.   One species has a selective advantage, so as hybridization continues, the other species will go extinct.

27.   Paleontologists studying fossilized therapsids (a group of mammal-like reptiles that are now extinct) would probably be using which of the following species concepts?
A.   the biological species concept
B.   the morphospecies concept
C.   the phylogenetic species concept   (accepted either B or C)
D.   None of the above; fossil species cannot be classified.

28.   The largest extinction, measured as a percentage of species that disappeared, occurred at the end of which geological period?

A.   Permian
B.   Cretaceous
C.   Tertiary
D.   Devonian
E.   Silurian

29.   Which of the following isolating mechanisms are prezygotic and which are postzygotic?
1.    Land iguana eggs can’t be fertilized by marine iguana sperm.
2.    Mules—horse-donkey hybrids—are sterile.
3.    In a forest, one beetle species lives on oaks and another beetle species lives on pines.
4.    In closely related bird species, males sing different courtship songs.
5.   Hybrid seeds from pollination of one yucca by another yucca species are aborted.

30.   Which of the following is most accurate?
A.   Mass extinctions are due to asteroid impacts; background extinctions may have a wide variety of causes.
B.   Mass extinctions focus on particularly prominent groups, such as dinosaurs; background extinctions affect species from throughout the tree of life.
C.   Only five mass extinctions have occurred, but many background extinctions have occurred.
D.   Mass extinctions involve at least 60 percent of the species present and extinguish groups rapidly and randomly; background extinctions are slower and result from natural selection.

31.   Some birds follow moving swarms of army ants in the tropics. As the ants march along the forest floor hunting insects and small vertebrates, birds follow and pick off any insects or small vertebrates that fly or jump out of the way of the ants. The interaction between birds and ants is an example of  what kind of species interaction?
A.   competition
B.   consumption
C.   commensalism
D.   parasitism
E.   mutualism

32.    In the example described in the previous question, what is the specific benefit relationship?
A.   Birds benefit from the association but have no impact on the ants.
B.   Birds benefit from the association and harm the ants.
C.   Birds and ants benefit from the association.
D.   Birds do not benefit from the association, but the ants do.
E.   Neither birds nor ants benefit from the association.

33.   A land developer is arguing with a group of ecologists. Of course the land developer wants the most land possible for building houses, but has to compromise by saving some land for animal habitat. The land developer offers 20 hectares in evenly distributed but isolated 1-hectare portions. The ecologists keep arguing for one 20 hectare area to remain intact. What’s the difference?
A.   There really is no difference; they should both work equally well.
B.   The isolated hectare plots are better because they spread out the habitat.
C.   The isolated plots are more vulnerable to edge effects.
D.   The large plot will create more inbreeding in many species.

34.   What does the above graph tell you about the definition of a keystone species?
A.   A keystone species has little interaction with other species in an environment.
B.   A keystone species removed from a community could have drastic effects.
C.   A keystone species can be any species.   
D.   A keystone species added to a community can make it more robust.

35.   Which of the following statements regarding extinction is false?
A.    Only certain species are immune from extinction.
B.   Species are vanishing today faster than at any other time in Earth’s history.
C.   Extinction occurs whether humans interfere or not.
D.   Extinctions can even be caused indirectly by humans.

36.  If a fossil is limited to undisturbed geological strata above the iridium layer created at the boundary between the asteroid that struck the earth at the end of the Meozoic era, then it
A. was abundant on Earth at the time of the asteroid impact.
B. should be embedded in volcanic ash.
C. is less than 65 million years old.
D. existed before the extinction of the reptiles known as dinosaurs.
E. became extinct before the Cenozoic era.

37.  Which of the following is the best example of humans undergoing evolution, understood as "descent with modification"?
A. reduction in number of hairs on the head of a balding person
B. widening of the pupils of the eyes when one encounters dimly lit conditions
C. increase in weight over an individual's lifetime
D. increased pigment production by the skin of a person who is exposed to increased UV radiation levels
E. reduction in coarseness of body hair over millennia

38.  Over evolutionary time, many cave-dwelling organisms have lost their eyes.  Tapeworms have lost their digestive systems.  Whales have lost their hind limbs.  How can natural selection account for these losses?
A. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
B. By the principle of use and disuse
C. Natural selection cannot account for losses, only for innovations.
D. These organisms had the misfortune to experience harmful mutations, which caused the loss of these structures.
E. Both B and D are correct.
39.   Looking at the species-area plot above, what can be concluded?
A.   Number of bird species increases linearly with island area.
B.   Number of bird species is different on various islands.
C.   Diversity is independent from island area.
D.   Number of bird species increases exponentially with island area.

40.   Using the same graph above, if habitable area on an island were reduced from 10,000 km2 to 1000 km2, roughly what percentage of the species would disappear?
A.    0.3%
B.   3%
C.   30%
D.   60%

Attached file(s)* Final exam KEY.doc (370 KB - downloaded 12 times.)
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3 years ago

The following questions refer to this information:  In the year 2500, five male space colonists and five female space colonists from Earth settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations.  All ten of the original colonists had free ear lobes, and two are heterozygous for that trait.  The allele for free ear lobes (A) is dominant to the allele for attached ear lobes (a).

41.  What is the allele frequency in the founding population?
A. 0.1 a,  0.9 A
B.  0.5 a,  0.5 A
C.  0.4 a,  0.6 A
D.  0.2 a,  0.8 A
E.  0.8 a,  0.2 A

42.  If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached ear lobes when the planet's population reaches 10,000?
A. 1,000    B.  100       C.  10,000    D.  400       E.  800

43.  If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This is an example of
A. diversifying selection.
B. stabilizing selection.
C. gene flow.
D. diploidy.
E. genetic drift.

44.  After many generations, the population on this planet has an unusually high frequency for the incidence of retinitis pigmentosa, a recessive genetic disease that makes people go blind, relative to Earth's population. This is most likely due to
A. the founder effect.
B. the bottleneck effect.
C. mutations.
D. sexual selection.
E. the inheritance of acquired characteristics.

45.  All of the following statements are inferences of natural selection except
A. subsequent generations of a population should have greater proportions of individuals that possess favorable traits.
B. unequal reproductive success among its members leads a population to adapt over time.
C. often only a fraction of offspring survive because there is a struggle for limited resources.
D. individuals whose inherited characteristics best fit them to the environment should leave more offspring.
E. an individual organism undergoes evolution over the course of its lifetime.

46.  A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats.  That the actual forelimbs of these mammals do not seem to be optimally arranged is because
A. in many cases, phenotype is not merely determined by genotype, but by the environment as well.
B. natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time.
C. natural selection is generally limited to modifying structures that were present in previous generations and in previous species.
D. natural selection operates in ways that are beyond the capability of the human mind to comprehend.
E. though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design.

47. Darwin synthesized information from several sources in developing his theory of evolution by natural selection.  Which of the following did not influence his thinking?
A.   Linneaus’ hierarchical classification of species, which could imply evolutionary relationships
B.   Lyell’s Principles of Geology, which described the gradualness and uniformity of geologic changes over long periods of time
C.   Mendel’s paper describing the basic principles of inheritance
D.   Examples of major changes in domesticated species produced by artificial selection
E.   The biogeographic distribution of species that he observed on the Galapagos Islands and during his journey around South America.

48.  On the axes below, illustrate the differences between the three types of selection.  (a; 3 pts) In the upper set of graphs, the original frequency distribution of phenotypes is illustrated.  Draw a second line on each panel to illustrate how the frequency distribution of phenotypes will change under the type of selection indicated.  For directional selection, you can decide which direction selection is operating.  (b; 3 pts) On the lower set of graphs, draw the curve showing how relative fitness changes according to the value of the trait in question under each corresponding selection regime.   

49. A stream has the following food chain (listed in order from the lowest to highest trophic levels):  benthic (bottom-dwelling) plants ? grazing macroinvertebrates ? juvenile fish (‘fry’) ? adult carnivorous fish. 
a.   (2 pts) If the food chain exhibits trophic cascades, will the plants be limited by top-down or bottom-up control?_______Top-down___________

b.   (2 pts) If the food chain exhibits trophic cascades and the top predator is removed, will the abundance of plants increase or decrease?___increase________ __________.

50. (2 pts) Why are many crops triploid or tetraploid?  Humans have selected for these genotypes – why?

They produce bigger products: flowers, fruits, seeds, etc.

51. The figure below represents some of my famous brother’s research in Kenya.  He created large exclosures that kept different sized herbivores out of his plots of Acadia drepanolobium trees.  Over a period of 5 years, he measured spine length on the branches of these trees.  Once produced spines don’t change in length, so he was interested in the length of spines produced on branches while under these different herbivory regimes.  The open bars indicate spine length of branches low and high on the trees in the absence of large mammalian herbivores (gazelles, elands, oryx); the gray bars represent spine lengths on trees in the presence of large mammalian herbivores, and the black bars indicate the spine length on trees  exposed to large mammals AND megaherbivores (elephants and giraffes).

a) (2 pts) What role do Acacia spines play in herbivory?  Ignore the ants that live in the spines: think only about the plant and its herbivores.  How does herbivory act as a selective agent on spine length?

Spines deter herbivory by making it difficult for herbivores to reach the leaves of the plant

b) (2 pts) Describe and explain the pattern of spine length on the low branches.

In plots with no herbivores, spine length on new branches was shorter than when herbivores are present. The plant responds to herbivory by producing longer spines and when there are no herbivory, selection favors NOT making long spines, to save energy.

c)  (2 pts) Describe and explain the pattern of spine length on the high branches.

Regardless of the herbivory category, the spines are relatively short.  The plant doesn’t “waste” energy producing long spines when they are not eaten (the animals can’t reach that high).  The exception might be in the presence of the megaherbivores – these spines are slightly longer than the other treatments.

d)  (2 pts) What does this tell you about foraging height (how high the mammals can reach) of the various mammalian herbivores?

This suggests that only the megaherbivores can reach at least 2m into the canopy of these trees; the “large” herbivores can not.

e)  (1 pt) This is an example of a _________  in Acacia.
i.   Compensatory response
ii.   Competitive response
iii.   Induced response
iv.   Non-adaptive response

52. (3 pts) Lawns are near monocultures, in part because grass is a good competitor.  It will outcompete most weeds such as dandelions etc.  Nevertheless, any homeowner will tell you that dandelions and other weeds persist in their lawns.  Using the principles we have learned in class, what might allow those weeds to persist in face of competition from a superior competitor (grass)?  Use R* in your answer.

It is likely that dandelions have a lower R* for some limiting resource (nutrient or water).  Once grass has been growing for awhile, depleting this resource below the level that grass can survive, dandelions will continue to grow and prosper because they need less of this recourse than grasses do. OR Weeds have higher R*– grass is the superior competitor until fertilizer added, raises nutrient levels and weeds flourish

53. (4 pts) Two populations are growing with logistic population growth.  Population 1 has r1=0.1 and K1=100. Population 2 has r2=0.05 and K2=150.  On a single graph, sketch N vs time for these populations (be sure to label which line refers to which population).

54. (3 pts) Many species of woodpecker are insectivorous—they drill holes in trees in search of insects to eat.  Search time for these species is quite high; handling time, in contrast, is extremely short.  If the foraging decisions of woodpeckers conform to the predictions of optimal foraging theory, should they be generalists (eat lots of different kinds of prey) or specialists (eat only a very few different kinds of prey)?  Explain, with specific reference to the formula (i.e., to receive full credit your answer must include a discussion of the terms of the formula) we discussed in class!

The formula in question says that if E2/h2 > E1/(s1+h1), then the predator should eat the 2nd prey item.  It should, in other words, be a generalist.  If handling time is low and search time is high, then this ratio will generally be true:  even if E2 is relatively low, it will probably make sense to eat it, since “s” is so high (and hence E1/(s1+h1) will generally be small.

55.  Life table analysis has been used to compare the viability of different sized populations of primrose—to see, for example, if large populations are more viable (i.e., are more likely to be stable or expanding) than small populations.  Researchers hypothesized that large populations of primrose were healthy (i.e., stable or expanding) while small populations (<100 individuals) were not healthy. The researchers sampled a large population and determined that R0=1.02.   The life table below contains data on age structure and fecundity of a small population.  Calculate the life table parameters, and compare the large and small populations.  (2 pts for correct R0 value)
Stage (x)   Nx    lx   mx   lxmx
Seedling   86   1.0   0   0
Juvenile   14   0.16   0   0
Adult 1   11   0.13   1   0.13
Adult 2   8   0.09   5   0.45
Adult 3   6   0.07   6   0.42
R0=   1.0

a.   (1 pt) Is the population increasing, declining, or stable?  __stable (this must match the R0 calculated above; if you calculated R0 = 1.007, this should say “increasing”____________

b.   (2 pts) During which age class is mortality highest?  Explain your answer with reference to the data.
The seedling stage experiences the highest mortality: only 16% of them survive to the juvenile stage.

c.   (2 pts) Which age class contributes most to reproduction in the population?  Explain your answer with reference to the data.
The Adult 2 stage contributes the most to reproduction because 1) they each produce 5 offspring and 2) they have a higher probability of survival to this stage than does the age class with the highest number of offspring (Adult 3). 

56. (3 pts) “The sight of a peacock makes me sick”.  Why did Darwin say this?

Darwin didn’t initially understand why male peacocks should have such a large, showy, expensive tails.  Only after careful consideration did he consider that the males with these big tails might have a reproductive advantage over males with small tails, through female choice.  But until he figured that out, he was baffled.

57.  (3 pts) In a population in Hardy-Weinberg equilibrium, 16% of the individuals show the recessive trait.  What is the frequency of the dominant allele in the population?  Circle your answer.

q2 = 0.16; q=0.4; p=0.6

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58. (5 pts) The Grants and Dolph Schluter spent a considerable amount of time trying to understand the “Ghost of Competition Past”, the suggestion that similar finch species living on the same island are morphologically and behaviorally different because selection favored these differences.  Schluter, in studying the details of feeding behavior of Geospiza difficilis and G. fuliginosa on the island of Pinta, found that the two species had virtually no overlap in their diets.  “There’s very little trace of competition”, Dolph says cheerfully,  “It really is a . . . . ghost.”   Why do birds of different species on a single island compete very little?  What is the Ghost of Competition Past?  What does this idea suggest about the role of competition in the past? 

Schluter finds that competition is basically non-existent between sympatric finches – they eat different food items.  He suspects that this is because food is limiting for the birds and the individuals of each species who ate different food items than individuals of the other species had higher fitness than those birds whose diets overlapped with the other species (this is an example of character displacement).  It truly is a ghost of competition past – there is no evidence of it except the different diets of the birds.  This suggests that the species did compete in the past, but have diverged enough in their beak dimensions to no longer compete.

59. (4 pts) The diagram below is our current best-guess for what a food web in Vermont prior to the arrival of European settlers looked like.  One of the first thing Europeans did was to eliminate wolves and mountain lions from Vermont.  Based on the food web, list 2 direct effects (i.e., effects that arise from direct species interactions) and 2 indirect effects (i.e., effects that arise from indirect species interactions) that would be likely following the removal of predators.


60. (4 pts) Explain the diversity of tree species in the Green Mountains based on the hypothesis that trade-offs prevent one species from dominating everywhere.  Be as specific as you can about the biology involved (i.e., provide examples of the mechanisms or processes that might be at work). 

Cold tolerance requires the investment of C and other resources into cryoprotectants, thicker cell walls, tracheids, etc.  Spruce and hemlock benefit from these costs at high elevation, but at low elevation they are poor competitors with species that can move water more quickly through their vascular systems (maple, birch). 

61.  (6 pts) You are a conservation biologist charged with creating a recovery plan for an endangered species of turtle. The turtle’s habitat has been fragmented into small, isolated but protected areas by suburbanization and highway construction. Some evidence indicates that certain turtle populations are adapted to marshes that are normal, whereas others are adapted to acidic wetlands or salty habitats. Further, some turtle populations number less than 25 breeding adults. In creating a recovery plan, the tools at your disposal are captive breeding, the capture and transfer of adults among populations, or the creation of habitat corridors between wetlands to make migration possible.  In the table below, identify what benefits might be achieved with each of the tools available (i.e., which of the problems that accompanies the “extinction vortex” are likely to be prevented or minimized by that approach), and what if any risks (i.e., is there something it might make worse?  Some hazard of doing this?) might accompany those tools.

Tool   Benefits   Risks
Captive breeding

   Used to increase reproductive success.  Benefits include the ability to plan matings so that inbreeding is avoided; survival of offspring can be higher than in the wild.  Can be the first step to a reintroduction plan.     Downside: very intensive, not all species respond well to captive breeding, mounting evidence that captive-bred individuals may not succeed in the wild.
Capture & transfer of adults among populations

   Can be used to rescue wild populations from the effects of inbreeding by mimicking natural gene flow. 
   Down side: very intensive, can be expensive, may have effects on the source population, may be impossible if there is not a healthy population nearby! In this particular case, transferring individuals that have adapted to one environment to a different environment is likely to be unsuccessful.
Habitat corridors

   Can increase movement of individuals among populations, thereby increasing genetic variation within them   Can be difficult and/or expensive to create; may not be possible if significant habitat degradation has occurred around each population.

62.  (6 pts) We discussed three factors that influence the pattern of succession at Glacier Bay by making some patterns of succession more likely and others less likely (or downright impossible). Provide an example of how each factor influenced succession either by recording a successional pathway that was made impossible or less likely by that factor OR one that was made more likely. 

Factor   Example of how it influenced succession
Species interactions

   Alder?Dryas?Spruce is impossible, because alder strongly inhibits Dryas
Species’ traits

   Dryas?Spruce?alder is impossible, because alder seeds are unable to germinate in the presence of any other vegetation.
Seed dispersal

   Most stages start with Dryas or alder because their seeds are more well-dispersed than those of spruce!
Note that in question 62, I asked for specific examples of pathways.  If you explained the mechanism but did not provide a pathway, you received partial credit.  Note that the pathway you provided actually had to illustrate the mechanism—so some of you provide examples for “seed dispersal” that were actual pathways, but had nothing to do with seed dispersal.  Those did not receive credit.

63. Islands have spurred important advances in both ecology and evolution.  The Theory of Island Biogeography was an attempt to explain patterns of species diversity among islands of different sizes and degrees of isolation. 

a)  (1 pts) Why does colonization rate decline as S (the # of species on the island) increases, according to the Theory of Island Biogeography?

Colonization rate declines because colonization is defined as the arrival of a new species.  As species accumulate, it becomes increasingly likely that any new arrivals are already present and, thus don’t count as new colonization.
b) (1 pt) Why does extinction rate increase with S?

Extinction increases as S increases because of the greater likelihood of competitive exlusion.  An additional factor is that as S increases, the population size of each individual species is likely to go down, and smaller populations are more vulnerable to extinction from a variety of factors (disturbance, disease, etc.).

c) (2 pts)What does the theory of island biogeography predict about how diversity should differ between a remote (isolated) island and an island close to the mainland (non-isolated)?

Remote islands should have fewer species at equilibrium than non-isolated islands.

d) (2 pts) What is the mechanism for this pattern, according to the theory of island biogeography?  (In other words, “why?”)

 This is because arrival of new species to the remote island will be slower/lower than to the non-isolated islands.
e)  (5 pts) Draw a graph below indicating how equilibrium species richness (S) is likely to differ between a small and a large island, according to the Theory of Island Biogeography.  Your graph should show the colonization and extinction curves and the equilibrium species richness for each island type.  (Note that if the curves are predicted to be the same for the two islands, you can just draw one curve but label it clearly so that I know that the one curve represents both islands.)

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