Question

44. Jellyfish are considered

a. meroplankton

b. kronoplankton

c. cryoplankton

d. holoplankton

45. Crab larvae are considered

a. meroplankton

b. kronoplankton

c. cryoplankton

d. holoplankton

46. Organisms that are able to swim against the current

a. phytoplankton

b. zooplankton

c. nekton

d. infauna

e. epifauna

47. Heterotrophic organisms that are too weak to swim against the current

a. phytoplankton

b. zooplankton

c. nekton

d. infauna

e. epifauna

Answer 1

Planktons is a collective term used for marine or freshwater organisms that cannot swim against the current, that is, they are carried along by the tides and currents of a marine or freshwater body. Each organism of planktons is known as a Plankter.

Planktons are of two types:

1. Phytoplanktons- autotrophs, they make their own food through photosynthesis
2. Zooplanktons- animals, heterotrophs, eat phytoplanktons

ANSWER 44: d) holoplankton

REASON: Jelly fishes are marine organisms that belong to the phylum Cnidaria. They spend their whole life as a plankton because of poor swimming abilities.

Meroplanktons are a type of marine organism that spend only a part of their life cycle (early life or the larval stage) in the plankton stage. They then move to a benthic (reside at the sea bed) or a nekton(can swim against the water currents) existence. But, we know that jelly fishes spend their whole life as a plankton which is contrasting to a meroplankton. Hence, option A is INCORRECT.

There are no planktons existing as kronoplankton. Hence, option B is INCORRECT.

Cryoplanktons are planktonic organisms that live in icy cold waters in the polar areas. Jellyfishes cannot survive such harsh environment. Hence, option C is INCORRECT.

Holoplanktons are planktonic organisms whose complete life cycle is in the form of a plankton. These organisms are found in the pelagic zones of the ocean. Since jellyfishes also sped their whole life as plankton, option D is the CORRECT answer.

ANSWER 45: a) meroplankton

Crabs are marine organisms that belong to the phylum arthropoda. Adult crabs are benthic, that is stay along the sea bed. The larval stage of crabs is a planktonic stage only.

Meroplanktons are a type of marine organism that spend only a part of their life cycle (early life or the larval stage) in the plankton stage. They then move to a benthic (reside at the sea bed) or a nekton(can swim against the water currents) existence. We know that, crabs spend their larval stage as planktonic stage and then as they become adult they move to a benthic stage. Hence, option A is CORRECT.

There are no planktons existing as kronoplankton. Hence, option B is INCORRECT.

Cryoplanktons are planktonic organisms that live in icy cold waters in the polar areas. Crabs cannot survive such harsh environment. Hence, option C is INCORRECT.

Holoplanktons are planktonic organisms whose complete life cycle is in the form of a plankton. These organisms are found in the pelagic zones of the ocean. Crabs do not spend their whole life as plankton, instead only larval stage as plankton. Hence, option D is INCORRECT.

ANSWER 46: c) nekton

REASON: Planktons are organisms that cannot swim against the current of water or are weak swimmers against the water current. They are of two types: phytoplankton (photosynthetic organisms) and zooplankton (animals). Thus, neither phytoplanktons nor zooplanktons can swim against the water current. Hence, option A and B both are INCORRECT.

Nekton is a collective term used for actively swimming organisms. These organisms are good swimmers and can even swim against the flow of water current. Hence, option C is CORRECT.

Benthic organisms are the one which live along the bed of a water body, because they cannot swim. They are further divided into two types:

1. Infauna- benthic organisms living inside the sediments of the bed of water body.
2. Epifauna- benthic organisms living on the surface of the bed of a water body.

Since, benthic organisms cannot swim, option D and E both become INCORRECT.

ANSWER 47: b) zooplankton

REASON: Planktons are organisms that cannot swim against the current of water or are weak swimmers against the water current. They are of two types: phytoplankton (photosynthetic organisms) and zooplankton (animals).

Phytoplanktons are autotrophic as they make their own food through the process of photosynthesis. Since they are planktons they cannot swim or are too weak to swim against the current, but they are not heterotrophic. Hence, option A is INCORRECT.

Zooplanktons are heterotrophic because they cannot prepare their own food and feed on phytoplanktons. Also being planktons they cannot swim against the current and carried along with the flow of water. Hence, option B is CORRECT.

Nekton is a collective term used for actively swimming organisms. These organisms are good swimmers and can even swim against the flow of water current. Hence, option C is INCORRECT.

Benthic organisms are the one which live along the bed of a water body, because they cannot swim. They are further divided into two types:

1. Infauna- benthic organisms living inside the sediments of the bed of water body.
2. Epifauna- benthic organisms living on the surface of the bed of a water body.

Since, benthic organisms cannot swim, option D and E both become INCORRECT.