Question

Identify the organisms that belong to the benthos of the lake ecosystem.
(a)Chironomid larvae and Red annelids
(b)Daphnia and Notonecta
(c)Ranatra and copepods
(d)Garris and Beetles

Answer 1

Hint: Benthos lives near seabeds, river, lake, or sea bottom. Benthos are commonly heterotrophs that feed on dead animals, organic matter and in case of food deprivation, they feed upon one another.

Complete answer:
Lake ecosystem is a house for many biotic plants, animals, and microorganisms. Lake consists of freshwater which is static that's why the lake ecosystem is also called a lentic ecosystem. Lake ecosystem covers 3 percent of the earth’s surface. Lake is divided into three zones: littoral zone, limnetic zone, and benthic zone.
-Littoral zone present near the shore of the lake. The Littoral zone responds to human activities and interacts with the profundal and pelagic zone. The organism in this region includes anemone, barnacles, chiton, crab, green algae, and sponges.
-Limnetic zone is present in the open area of the lake. This zone receives the maximum amount of sunlight that's why this zone is responsible for photosynthesis and oxygen supply for bottom-dwelling aquatic animals. Organisms in this zone include copepods, cladoceran, rotifers, insects, and fishes.
-Benthic zone present deep in the lake, this zone receives a minimum amount of sunlight or no sunlight. This zone is a dark zone therefore organisms present in this zone depend on small fishes and amphibians for food. Organism present in this zone is called benthos like sea urchin, crab, corals, amphipods, Chironomus midge larvae.

Additional Information: The Caspian Sea in Europe and Asia is the world’s largest lake with an area of 370,000 square kilometers.
The world’s deepest lake is Lake Baikal in Russia, it is 2 Km deep from the surface.
The great salt lake in the US is the largest saline lake.
So, the correct answer is ‘Chironomid and Red annelids’.

Note: Increase chemicals as nitrate, phosphorus, detergents, and minerals lead to lake eutrophication. In the case of eutrophication oxygen present in water decreases because of useful bacterial degradation of algae.