Question

Which one of the following is the correct sequence of a food chain?

• A. Diatoms-Herrings-Crustaceans
• B. Crustaceans-Diatoms-Herrings
• C. Diatoms-Crustaceans-Herrings
• D. Crustaceans-Herrings-Diatoms

Hint:

Remember the aquatic food chain: \[ \text{Phytoplankton} \rightarrow \text{Zooplankton} \rightarrow \text{Fish} \] Here:
• Diatoms \(\rightarrow\) Phytoplankton (Producer)
• Crustaceans \(\rightarrow\) Zooplankton (Primary consumer)
• Herrings \(\rightarrow\) Fish (Secondary consumer)

Answer 1

The Correct Option is C

Concept: A food chain represents the transfer of energy from producers to consumers in an ecosystem. The sequence generally follows: \[ \text{Producer} \rightarrow \text{Primary Consumer} \rightarrow \text{Secondary Consumer} \] In aquatic ecosystems:
• Diatoms are microscopic photosynthetic producers.
• Crustaceans feed on phytoplankton such as diatoms.
• Herrings are fish that feed on small crustaceans.

Step 1: Identifying the producer in the food chain. Diatoms are photosynthetic phytoplankton and form the primary producers of many aquatic food chains. Thus: \[ \text{Diatoms} \Rightarrow \text{Producer} \]

Step 2: Identifying the primary consumer. Small crustaceans such as copepods consume phytoplankton like diatoms. Hence: \[ \text{Crustaceans} \Rightarrow \text{Primary consumers} \]

Step 3: Identifying the secondary consumer. Herrings feed on crustaceans and therefore occupy the next trophic level. Thus: \[ \text{Herrings} \Rightarrow \text{Secondary consumers} \] Therefore, the correct food chain sequence is: \[ \boxed{\text{Diatoms} \rightarrow \text{Crustaceans} \rightarrow \text{Herrings}} \]

Step 4: Eliminating the incorrect options.
• Option (A): Incorrect because herrings do not feed directly on diatoms before crustaceans.
• Option (B): Incorrect because producers must come first.
• Option (D): Incorrect because diatoms cannot occupy the final trophic level. Hence, option (C) is correct.