Ecology

Choose the Correct Answer

Correct Answer : Option c

Explanation
The lake ecosystem is divided into distinct zones, each with specific characteristics and inhabitants.

Littoral Zone (Shallow Water, Near the Shore)
● This zone allows easy light penetration and supports diverse aquatic life.
● Common species include crabs, clownfish, sharks, anemones, clams, lobsters, and penguins.
● The lake bottom near this zone is often covered with mud, where organisms like worms, chironomid larvae, mollusks, nematodes, and ostracods thrive.

Limnetic (Pelagic) Zone (Open Water)
● This zone consists of high light penetration and is dominated by plankton.
● Plankton vs. Nekton:
○ Plankton are suspended in water, while nekton are active swimmers.
○ Phytoplankton include algae like Chlorella (single-celled) and Volvox (colonial algae).
○ Zooplankton are primarily herbivores that feed on phytoplankton, but carnivores are also present.
○ Daphnia, a cladoceran crustacean, is a key zooplankton species in this zone.
Benthic Zone (Deepest Region, No Light Penetration)
● This zone extends beyond the littoral region and is dominated by heterotrophic organisms.
● The bottom is usually covered with mud, whose composition varies by lake conditions.
● Larger inhabitants include mollusks, worms, and chironomid larvae, while numerous small organisms like nematodes and ostracods also reside here.