Question

The order of organisms in an aquatic food chain is
A) Bacteria seal diatom fish crustacea
B) Crustacean seal fish polar bear diatom
C) Polar bear diatom seal crustacea
D) Diatom crustacea fish seal bacteria

Answer 1

Hint: Diatoms are a kind of algae. They are primary producers which use photosynthesis to produce food energy. Most of the photosynthetic activity in the world is a result of algae and phytoplankton found in the ocean.

Complete Answer:
- Any food chain consists of producers, several levels of consumers, and decomposers. In an aquatic food chain, the producers are phytoplankton and algae which are a part of the first trophic level.
- Producers are called this because they synthesise their own food. As we go up the trophic levels, we encounter primary, secondary, and even tertiary consumers, which also tend to increase in size.
- Secondary and tertiary consumers are also known as predators as they kill and feed on other animals, while primary consumers directly feed on the producers. Right at the end, come in the decomposers. In the aquatic food chain, these are bacteria.
- Decomposers are responsible for breaking down all the remaining biological material into nutrients that the producers can then use.
- In option A, the diatom has been placed between the seal and the fish. The seal is a predator which would feed on the fish. In B, diatoms are shown to be next in lie with polar bears. In fact, the entire chain is mixed up. And in option C, again the producer diatom has been placed between two predators. In option D, the producer is the diatom, followed by the consumers consisting of crustaceans eaten by fish which are in turn eaten by seals. Finally the bacteria will decompose all of them.

Hence the correct answer is option D.

Note: It is more accurate to describe food webs as these interactions are not simple straight lines running from one organism to the next. Bacteria themselves can be chemo or photosynthetic producers.