The amount of energy the producers in this energy pyramid provide the primary consumer is 54,000 joules. From this amount, 540 joules are provided to the tertiary consumers. Based on this model, how much of the energy was provided to secondary consumers?

Food webs such as the one shown were first used in 1927 by the animal ecologist Charles Elton. The food web below represents the feeding relationships among organisms in an Alaskan ecosystem. An environmental change that removed which of these organisms from the ecosystem would cause the most instability in the ecosystem?

Some relationships between different organisms are shown in the table. Which table correctly identifies each type of interaction described?

What step of the water cycle is shown in this picture?

What word describes a trait that helps an organism survive in its environment?

What is the role of the sun in the water cycle?

Most of Earth's fresh water is used for

Dissolved oxygen enters a body of water through which processes?

What percentage of the water on Earth is FRESHWATER?

Which is the best definition of an Aquifer?

Water that has a salinity above 0.5%, but below 3% is considered -

An area where all of the precipitation and runoff eventually end up in the same body of water.

Which of the following describes characteristics of PLANTS, but not algae?

Using this dichotomous key, identity the name of the circled fish.