Exam 53: Ecosystems and Global Ecology

Which of the following factors account for the inefficiency of the rate of photosynthesis? I. Even when conditions are ideal, the pigments that drive photosynthesis can absorb only a fraction of the light wavelengths available and thus a fraction of the total energy received. II. Plants in equatorial biomes have drastically reduced photosynthetic rates in winter. III. If conditions get dry, stomata close to conserve water. IV. The efficiency of enzymes is not temperature dependent.

-Consider the global nitrogen cycle depicted in the accompanying figure. What is the limiting portion of the cycle for plants?

-Using the accompanying figure, what is the predicted change in temperature under a model with dramatic reduction of greenhouse gases?

- Consider the global water cycle depicted in the accompanying figure. Which one of the reserves contains the smallest percentage of global water?

Approximately how many kilograms (kg) of carnivore (secondary consumer) biomass can be supported by a field plot containing 1000 kg of plant material?

-Which habitat type in the figure makes available the most new tissue to consumers?

What is the main reason for using food webs instead of food chains in analyzing ecosystems? I. Most organisms eat more than one type of food. II. Most organisms feed at several trophic levels. III. The decomposition cycle needs to be shown.

When primary producers expend energy to build new tissue, this is ________.

A 3-hectare lake in the American Midwest suddenly has succumbed to an algal bloom. What is the likely cause of this in freshwater ecosystems?

For most terrestrial ecosystems, pyramids composed of species abundances, biomass, and energy are similar in that they have a broad base and a narrow top. The primary reason for this pattern is that ________.

You own 300 acres of patchy temperate forest. Which one of the following actions would increase the net primary productivity of the area the most?

Which of the following most often controls the rate of nutrient cycling in ecosystems?

Consider the food chain of grass → grasshopper → mouse → snake → hawk. About how much of the chemical energy fixed by photosynthesis of the grass (100 percent) is available to the hawk?

Detritus can be consumed by which of the following primary decomposers? I. bacteria II. archaea III. fungi IV. earthworms

Which of the following is a consequence of biomagnification?

-After looking at the experiment in the accompanying figure, what can be said about nutrient export in ecosystems? Nutrient export is ________.

Approximately what percentage of the energy from sunlight is converted into gross primary production?

Considering its total area covered, which ecosystem type represented in the figure has a very low level of economic impact on Earth's ecosystem, assuming that NPP is positively correlated with economic value?

Global climate change refers to ________.

If the flow of energy in an arctic ecosystem goes through a simple food chain, perhaps involving humans, starting from phytoplankton to zooplankton to fish to seals to polar bears, then which of the following could be TRUE?