Phytoplankton, shown on the left in the image below, are microscopic organisms that can be found in freshwater and salt water environments. They perform photosynthesis to get energy and act as an important food source for larger organisms, such as the whale that is shown on the right. Phytoplankton A large whale. Which characteristic describes the whale but not its food source, the phytoplankton? The whale is heterotrophic. The whale has cell walls. The whale is unicellular. The whale is a prokaryote.

The whale is heterotrophic.

Explanation:

Energy is needed by organisms to perform their life functions. Organisms, in nature, feed on one another for energy source. Some organisms are, however, capable of synthesizing their own food or energy source via a process called photosynthesis. This is the case of the phytoplankton in the question. These organisms are, therefore, called AUTOTROPHIC ORGANISMS or PRODUCERS.

On the other hand, some organisms are incapable of this self-production of energy source. Hence, they rely on other organisms for it. These category of organisms are called HETEROTROPHIC organisms, which is the category the large whale fall into due to its dependence on phytoplankton for energy source.