Question

Second most important trophic level in a lake is
A) Zooplankton
B) Phytoplankton
C) Benthos
D) None of the above

Answer 1

Hint: The amount of energy decreases at successive trophic levels and all organisms at each trophic level depend upon those at the lower trophic level for their energy demands.

Complete answer :
In the lake ecosystem, phytoplankton are the primary producers while zooplanktons, larval insects, tadpole larvae, snails, turtles, etc are the primary consumers or herbivores. Benthos and fishes were included in the higher trophic levels. The broad base of primary producers supports overlying levels of herbivores, planktivores and smaller numbers of carnivores. These individuals' trophic level is identified as a food chain, but in fact many organisms are omnivorous and not characterized by a particular level. And the consumers often shift levels throughout their life cycle.
The plants may decompose and be eaten by primary consumers, which is the second trophic level. The link occurred in the food chain typically involves zooplankton grazing on algae. But it also includes larval fish eating zooplankton and a variety of invertebrates that eat attached algae and higher plants. The secondary consumers are considered as the third trophic level which eats the primary consumers. The tertiary consumers are considered as fourth trophic level which are large consumers.

Additional information:
Primary carnivores or secondary consumers include some insects, small predatory fishes, etc.
Secondary carnivores or tertiary consumers are represented by large predatory fishes, frogs, etc.
Tertiary carnivores or quaternary consumers are represented by snakes.

So, the correct answer is ‘zooplanktons’.

Note: Zooplankton are heterotrophic planktons that range from microscopic organisms to large species, such as jellyfish. Zooplanktons are found within large bodies of water, including oceans and freshwater systems. Zooplanktons are ecologically important organisms that are an integral component of the food chain. Benthos are the organisms, which are attached to or resting on the bottom sediments.