Question

Animals or organisms floating on the surface of water are known as
A. Plankton
B. Pelagic
C. Benthon
D. Neritic

Answer 1

Animals which can float on the surface of water are generally unable to swim against a current and thus they act as a crucial source of food to various small to big animals present in water bodies.

Complete answer:
Let us analyse the options and find the correct answer.
Option A: Planktons are the organisms that float on the surface of water bodies. They may be animal-like (Zooplankton) or plant-like (Phytoplankton). Therefore, it is the correct option.
Plankton is a term used for animals and organisms which are found in water bodies but cannot swim against the water current. Their size ranges from 0.2 micrometers (bacteria) to 20 centimeters (jellyfish). They have a very significant role in the ecosystem as they account for 50% of the total oxygen produced by photosynthesis.

Option B: Pelagic fishes are present in the water column of lake, coastal and ocean water, and they are not found concentrated near the bottom of the sea or the lake. Therefore, it is the incorrect option.

Option C: Benthos are bottom dwellers. They live in the bottom of the sea or lakes where relatively little light penetrates and pressure is high due to the water column.Therefore, it is the incorrect option.

Option D: Neritic means animals living in muddy or sandy bottoms near the sea shore. They are also known as inshore fish or coastal fish. Therefore, it is the incorrect option.

Therefore, the correct option is A) Planktons.

Note: Planktons have a significant role to play in the ecosystem,
- They are producers of half the total amount of oxygen which is produced during photosynthesis.
- They have an important role in nutrient cycling.
- Some of the planktons have the ability to fix atmospheric nitrogen as ammonia and nitrates.
- They are required for keeping a balance between oxygen and carbon dioxide levels.