As an overall average, about ______ of the energy at one trophic level is generally available to the next highest rank in the food chain.

Which ecosystem is characterized by freshwater and ranges in size from a few square meters to thousands of square kilometers? It is a permanent feature of the landscape. 

Grain is eaten by cows, and cows are eaten by humans. If the ecological transfer efficiency between each trophic level is 10 percent, how much grain is required to produce 70 kg of human biomass?

Combustion is an important action in the _____ cycle.

A toxic pollutant would probably reach its highest concentration in which species?

What is the relationship between global warming and the greenhouse effect?

Use the incomplete diagram, illustrating some of the steps involved in eutrophication to answer the question. What would be a likely entry for box B?

Which type of forest has seasons divided into short, moist, and moderately warm summers and long, cold, and dry winters? The length of the growing season is 130 days.

Which of these land ecosystems would be expected to have the highest total net primary productivity?

The amount of chemical energy in consumers’ food that is converted to their own new biomass during a given time period is known as which of the following?