Question

In the open ocean, phytoplankton go through photosynthesis and are eaten by zooplankton as well as small fish and large whales. Small fish also eat zooplankton, and are eaten by medium fish. Medium fish are eaten by both seals and sharks eat both medium fish and seals. In this system, the small fish serve as:

a. secondary consumers

b. primary consumers

c. both primary and secondary consumers

d. both primary and secondary producers

Answer 1

a. Secondary consumer.

Discussion and explanation :

Here in marine food chain, phytoplanktons are producers because they are able to do photosynthesis and prepare their own food and also pass the energy to other organisms in the marine system.

Organisms which are unable to prepare their own food and thus depend on producer for their energy requirement either directly or indirectly are termed as consumers.

Organism (zooplankton) which is directly dependent on phytoplanktons is primary consumer. Primary consumer is usually a herbivore.

While small fish which eats zooplankton and phytoplankton both, is secondary consumer in this food chain. Any single species, usually cannot be primary or secondary consumer both. Here small fish is omnivore (Carnivore + herbivore).

Medium fish which eats small fish will be tertiary consumer. Sharks are top level consumers in this system.