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Exam 54: Biodiversity and Communities

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Question 21

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Using the symbols +, −, and 0 to indicate interspecific species interactions, where the first symbol refers to the first organism mentioned, which of the following claims/statements is correct?

A) +/0 will always remain such.
B) A +/− interaction could shift to +/0 or +/+ over time, depending on other factors such as competition, population density, or environmental changes.
C) Species interactions occur in isolation and cannot affect the structure of ecological communities.
D) A −/− interaction benefits both of the species in the relationship.

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Question 22

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Which of the following is a correct statement about MacArthur and Wilson's island equilibrium model?

A) As the number of species on an island increases, the emigration rate decreases.
B) Competitive exclusion is less likely on an island that has large numbers of species.
C) Small islands receive few new immigrant species.
D) Islands closer to the mainland have higher extinction rates.

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Question 23

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Which of the following best describes the consequences of white-band disease in Caribbean coral reefs?

Use the figure to answer the following question. Treehoppers (a type of insect) produce honeydew, which ants use for food. Treehoppers have a major predator, the jumping spider. Researchers hypothesized that the ants would protect the treehoppers from the spiders. In an experiment, researchers followed study plots with ants removed from the system and compared them to a control plot. Which of the following conclusions is best supported by the data provided in the figure?

Which claim best explains the observation that species richness is higher in tropical regions than in temperate regions?

Which of the following best explains why moderate levels of disturbance result in an increase in community diversity?

Use the figure to answer the following question. In the figure, species A through F are found among four communities, with the number of circles representing their abundance. Which community has the highest diversity?

In a particular case of secondary succession, three species of wild grass all invaded a field. By the second season, a single species dominated the field and the other two species had a lower relative abundance. A possible factor contributing to the abundances of these species in this example of secondary succession is ________.

Which of the following is a widely supported explanation for the tendency of tropical communities to have greater species diversity than temperate or polar communities?

Approximately how much total biomass of plant material would hypothetically be necessary to support six carnivorous lions (whose diet consists only of herbivorous prey) , each weighing 50 kg, living in a given area along with their prey, on an ongoing basis? (Assume a 10% efficiency in energy transfer.)

Use the following diagram of a hypothetical food web to answer the question. In this particular scenario, the arrows represent the transfer of energy between the various organisms and decomposers are included in the diagram. Which letter best represents a primary consumer in the community?

Which of the following best explains why a pathogen is generally more virulent in a new habitat?

As you study two closely related predatory insect species, the two-spot and the three-spot avenger beetles, you notice that each species seeks prey at night when present in an area where the other beetle species is absent. However, where their ranges overlap, the two-spot avenger beetle hunts at night and the three-spot hunts in the morning. When you bring them into the laboratory and isolate the two different species, you discover that the offspring of both species are nocturnal. The observations above indicate that the two species most likely demonstrate which of following ecological processes? You have discovered an example of ________.

Use the figures to answer the following question. The different shaded squares in the figure, from white to darker gray, represent different species, and more squares of a shade correspond to a higher abundance. According to the Shannon Diversity Index, which of the five blocks above, with each containing 36 squares, represents the greatest diversity?

Five hypothetical forest communities, each have one hundred individuals distributed among four different tree species (W, X, Y, and Z) . Which of the following combinations of species in a forest community would make it the most diverse?

The principle of competitive exclusion states that ________.

The oak tree pathogen that causes sudden oak death, Phytophthora ramorum, has dispersed 800 kilometers in 15 years. West Nile virus spread from New York State to 46 other states in 5 years. Which of the following best explains the difference in the rate of spread of these two pathogens?

Food chains are sometimes short because ________.

In terms of community ecology, which of the following best explains why pathogens are often more virulent now than in the past?

Use the following diagram of five islands formed at around the same time near a particular mainland, as well as the principles of MacArthur and Wilson's island equilibrium model, to answer the question. Which region would likely have the greatest species diversity?