Exam 37: Communities and Ecosystems

In a certain ecosystem, field mice are preyed on by snakes and hawks. The entry of wild dogs into the system adds a third mouse predator. The most likely short-term result of this addition is

To stabilize the environment in the habitat and enable it to become self-sufficient again, it would be helpful to add

The most worrisome results of the large-scale clearing and cultivation of land include

When a crocodile eats a fish, the interspecific interaction between the two could be expressed as ________ for the crocodile and ________ for the fish.

Which ecological problem might result from fertilizing a golf course with phosphorus-rich fertilizer?

If an overlap develops between the ranges of two closely related species, and if the species occupy the same niche in the zone of overlap, what will probably happen in the zone of overlap?

About how much of the energy in the producers of an ecosystem will be available to secondary consumers in this ecosystem?

Which statement about the nitrogen cycle is true?

For a given area and time period, the amount of solar energy converted to chemical energy in organic compounds is called

Which trophic level in this food chain represents the secondary consumer?

Non-native species that are introduced to new environments, spread far beyond the original point of introduction, and cause damage are called

The prokaryotes that cause tooth decay have a ________ relationship with humans.

Within an ecosystem, a tree is a

In an average ecosystem, about how much energy is present in the organisms at a given trophic level compared to the organisms at the next higher trophic level?

In your backyard you overturn a large rock. In the damp soil underneath the rock, you see various insects scurrying for cover: two black beetles, five black ants, two brown beetles, and three pillbugs. In this community of organisms, relative abundance favors

A stonefly is an aquatic insect that has an incomplete life cycle. It spends its growing period (nymph life stage) on the bottom of streams, camouflaged by the rocky bottom. When it has finished growing, it crawls to the edges of streambeds to molt and emerges as a winged adult. Fish often eat the juvenile nymphs as they make their way to the edge of the streambeds. -Suppose that scientists who study predator-prey relationships notice that over a 50-year span, new color patterns evolve in the stonefly nymphs. What would be a logical and reasonable question that the scientists could investigate in relation to their observations and their knowledge of predator-prey relationships?

Which process represents a step in the nitrogen cycle?

If an owl and a hawk both eat mice, what is the relationship between a hawk and an owl?

Kudzu is a fast-growing vine that was introduced to the United States in 1876 as a fragrant, ornamental plant and was later used as a source of erosion control. Kudzu grows especially well in the warm, humid climate of the Southeastern United States. In fact, it grows so well that it can outgrow and kill off less successful native plants; it can also kill off areas of forest because it prevents forest trees from receiving sunlight. Kudzu can best be described as

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. -What do their results demonstrate about the interactions between the species that they studied?