Exam 47: Species Interactions, Communities, and Ecosystems

The diversity of our native grassland species is in decline. Restoration ecologists working to restore native grasslands are experimenting with combinations of burning and grazing to simulate natural conditions and increase species diversity. According to Joseph Connell, what level of burning and grazing should ecologists aim for?

The bacterial species Staphylococus aureus is found on the skin and in the nasal passages of about 20% of the human population. It can survive on polyester for 3 months and can also infect cows and chickens. Thus, its relationship with humans is:

You decide to follow the development of the human gut microbiota over time by sampling the solid waste of infants from birth to 24 weeks old. Which of the following setups minimizes the sources of variation in your experiment?

A species' _____ niche comprises the full range of climate conditions and food resources that permit the individuals in a species to live.

Many flowering plant species are pollinated by a single species. The evolution of specialist pollinators is the result of:

Symbiotic relationships are subject to natural selection.

The sequence of species that colonize a recently disturbed area through succession is unpredictable.

A woman observes a hawk perched in the branches of a pine tree. Suddenly, the hawk swoops down and catches a chipmunk that has been eating sunflower seeds at the woman's bird feeder. The hawk returns to its nest, which is in a nearby oak tree. Through this scenario, what can you tell about the niches of the organisms involved?

Spanish moss is not a moss, but a flowering plant (Tillandsia usneoides) often seen draped from the branches of live oaks, cypress, and other large trees in the southeastern United States. The trees on which it grows provide support but no nutrients or moisture-the plant provides those things for itself, without apparently harming its support tree. This, then, is an example of a:

What is the ecological explanation for why sunflowers and grassy weeds thrive in your untended, sunny garden, but mosses, which require shade, do not?

Which of the following is a good predictor of biodiversity in terrestrial ecosystems?

During a biodiversity sampling exercise, an undergraduate found 52 species of bees in one area of campus yet calculated that there were probably 72 species of bees in that specific area of the campus. Why is there typically a discrepancy between the number of different species caught and the calculated value of how many species probably exist in an area?

Because energy transfer is not 100% efficient across trophic levels, a maximum of about _____% of energy and biomass available at one trophic level is available at the next.

Southern California is an ecosystem that has evolved organisms with adaptations to frequent fires. Each time a fire occurs in the region a biologist should observe:

Measuring its costs and benefits in terms of energy spent and/or gained, which interaction(s) involve(s) one individual gaining and one individual losing?

Consider the following: You continue your experiments by taking one of the trees in the canopy and removing all of the ants. If the ants and aphids are in a mutualistic relationship that strongly benefits them both, you expect the aphid population will decrease in size in response to the lack of ants. The BEST control for your experiment in this scenario is a tree in which you _____ and you measure the abundance of _____ over time.

Aphids can feed in the leafy treetops (or tree canopies). Ants are usually not abundant in the tree canopies unless aphids are also present. You introduce aphids to an area of the tree canopy and survey the abundance of ants over time. Which of the plots below represents your expected trend in ant abundance?

Competition occurs: