Use the diagram that shows a river basin with three parts labeled X, Y, and Z to answer the question.

What process is occurring at the location labeled Z?

The image shows an aquatic food chain. Which organism(s) will be unaffected if the krill are removed from the aquatic food web?

A student observes four actions, as described in the table.

Which actions are physical changes?

In 1911, a small population of 25 reindeer was introduced on Saint Paul Island. The graph shows the increase in the population of reindeer on the island between 1911 and 1940 with four lines (W, X, Y, and Z) that represent the estimated reindeer population by 1950.

If the reindeer population overgrazed their food supply in 1940, which line would likely represent the estimated population of reindeer on the island by 1950?

The chemical equation represents the process of photosynthesis.

Which element in the reaction is unbalanced?

Which are sources of freshwater on Earth’s surface?

A group of researchers analyzed the water samples from four polluted lakes (P, Q, R, and S) for the presence of four different substances, as shown in the table.

Which lakes’ water samples exceed only one of the EPA’s maximum permissible levels?

A researcher analyzes the water in a stream and observes that the water contains many snails, crayfish, shrimp, caddisflies, mayflies, and stoneflies. These organisms are invertebrates that are used as bioindicators for bodies of water.

What can be concluded correctly about the water in the stream?

Examine the diagram of a food web.

A small population of eagles is introduced in the food web. The eagles feed on mice and reproduce at high rates. What is the most likely consequence of the introduction of eagles in the food web?