Exam 37: Communities and Ecosystems

During ecological succession, the species composition of a plant community generally

Most plants have a variety of chemicals, spines, and thorns because the plants

Which arrow shows nitrogen fixation?

A community is composed of

What is an example of predation?

Eutrophication of a lake could occur if

Which list accurately orders a food chain in the grasslands of Africa from low to high trophic levels?

In addition to abiotic factors, community composition of plants can be severely compromised by

Organisms that digest decaying organic material are

Some herbivore-plant interactions evolved through a series of reciprocal evolutionary adaptations in both species. This process is called

The flow of ________ into ecosystems occurs in one direction only, while ________ are recycled within the ecosystem itself.

Biosphere II is a huge, dome-covered, self-contained structure located outside Tucson, Arizona. It was built to try to duplicate Earth's biosphere and ecosystems in miniature and to use the information gained from this experiment to help design similar habitats on the Moon and Mars. Biosphere II contained small versions of many of Earth's ecosystems, including an ocean with a coral reef, mangrove wetlands, a grassland, a desert, an agricultural system, and a house for humans. Eight men and women were sealed inside the habitat for a proposed 2-year stay. The air, water, and food for these "biospherians" all came from inside the sealed habitat, and their only contact with the outside world was through computers and telephones. Before the 2 years were up, however, the experiment failed. Supplemental oxygen was pumped into the facility, and food supplies were provided through the airlocks. What caused the failure of the experiment? It was traced to nutrient pollution. The soil in some of the biosphere ecosystems was unusually rich in nutrients. These excess nutrients caused a huge population explosion in decomposer bacteria, which led to oxygen depletion. -How could a population explosion of bacteria lead to oxygen depletion?

Denitrifying bacteria convert ________ to ________.

Consider the following marine community: Sea otters prey on sea urchins and therefore help maintain a healthy sea urchin population. Sea urchins prey on kelp. By helping to maintain viable sea urchin populations, the sea otters are also allowing enough kelp to grow and act as a habitat for other organisms. -Suppose that a bacterial infection swept across a sea otter population and killed most sea otters before they could reproduce. How would the marine community be affected?

When a New England farm is abandoned, its formerly plowed fields first become weedy meadows, then shrubby areas, and finally forest. This sequence of plant communities is an example of

A hypothetical community on a barren mid-Atlantic island consists of two fish-eating seabirds (the booby and the noddy), the fungi and microorganisms that live on the birds' dung, a tick that feeds on these two birds, a cactus, a moth that feeds on cast-off feathers, a beetle that lives on dung organisms, and spiders that eat the other arthropods. There are no other plants and no lichens. Which pair of organism and trophic structure is incorrect?

One predator avoidance mechanism that has evolved in prey is

Japanese stiltgrass is an invasive plant that was accidentally introduced to the United States in the early 1900s. It can be found on roadsides and in forests, and it has many impacts on native plants and animals. Biologists Jayna DeVore and John Maerz studied the effect of Japanese stiltgrass on American toads in their natural habitat. They enclosed American toads in cages with lycosid spiders and/or Japanese stiltgrass. The four treatments were (A) lycosid spiders and Japanese stiltgrass, (B) lycosid spiders without Japanese stiltgrass, (C) lycosid spiders and Japanese stiltgrass, and (D) no lycosid spiders and no Japanese stiltgrass. They compared the survival of American toads across the treatments (left graph). They also measured the density of lycosid spiders in different areas where Japanese stiltgrass was absent vs. present (right graph). Source: DeVore, J. L., & Maerz, J. C. (2014). Grass invasion increases top‐down pressure on an amphibian via structurally mediated effects on an intraguild predator. Ecology, 95(7), 1724-1730. -American toads consume insects. An American toad that is consuming herbivorous insects is considered a

In a hypothetical food chain consisting of grass, grasshoppers, sparrows, and hawks, the grasshoppers are

Which statement regarding food webs is true?