Question

Study the following

S.No	Consumer	Character	Example
I.	Neuston	Air water interface	water snakes
II.	Nekton	Free swimming	Ranatra
III.	Periphyton	Cling to aquatic plants	mosquito larvae
IV.	Benthos	move to bottom	crayfish

Which two of the above are true?
A. I, II
B. II, IV
C. III, IV
D. II, IV

Answer 1

Aquatic organisms have different biological features, adaptations and environments, but within a dynamic network of ecological functions and relationships, they are related. These interactions provide the environment with its distinctive features and the ability to execute its essential functions.

Complete Answer:
The species in the marine environment (both flora and fauna) that have water as their primary habitat are classified as aquatic organisms. They can be found in various kinds of marine environments.

Now, let us find the solution from the options-
- Neuston, a community of species located on top of the surface water film or stuck to the underside of it. Insects including whirling beetles and water striders, certain spiders and protozoans, and sometimes worms, insect larvae, snails, and hydras are found in the neuston. It is distinct from plankton that is only incidentally connected to the surface film.

- Nekton, an agglomeration of pelagic animals, independent of water movement or wind, which swims freely. Adult types are described only by three phyla. Various species of bony fish like chordate nekton, cartilaginous fish including sharks, many species of reptiles.

- Periphyton is a diverse marine biota and microorganisms clinging to stones, sticks and underwater surfaces, and similar non-attached organisms and detritus, on underwater substrates. The Periphyton is overgrown in the marine ecosystem by mammals. For the manufacturing of Periphyton is used in aquaculture as a combination of biodegradable and non-biodegradable substrates and its abundance on biodegradable substrates is greater.

- Benthos, also recognized as the benthic zone, is the population of animals that exist on, in, or near the seabed, river, bay, or stream floor. This group, from tidal pools across the foreshore, to the territorial waters, and then down to the abyssal depths, exists in or around aquatic or freshwater sedimentary habitats.

Thus, the correct option is option (C) III, IV.

Note: Aquatic animals (and plants) use oxygen dissolved in water for respiration, and a decrease in its concentration below 3-5 ppm can result in the death of many aquatic species. There are narrow temperature range levels for marine animals, so minor increases in water temperature can be a significant challenge to certain species' survival.