Question

Upper part of sea/aquatic ecosystem contains………………….
A. Plankton
b. Nekton
c. Plankton and nekton
d. None of these

Answer 1

Hint:
 Aquatic ecology is the study of water-based ecosystems. They are a region of the water, in which ‘significant’ biological activity can occur. This definition avoids most groundwater systems. Aquatic ecosystems involve flowing or still water and can be fresh or saline.


Complete step by step solution:
The aquatic ecosystem has several types, they are freshwater, groundwater, brackish water, marine water, anthropogenic waters.

Importance of aquatic ecosystems:
- Biodiversity- species richness or trophic structure.
- Breeding- it grounds for many species.
- Buffer systems- physical and chemical.
- Sinks- resting places for sediments and chemicals.
 - Hydrological cycles- continuous movement of water on, above and below the earth’s surface.

Characteristics of aquatic ecosystems:
- Factors such as temperature, sunlight, oxygen and nutrients decide which organisms live in which area of the water.

- Aquatic organisms have three groups:
a. Plankton- it is microscopic organisms that float in the upper part of water, it can be zooplankton or phytoplankton.
b. Nekton- it is all organisms that swim actively in open water, independent of currents.
c. Benthos- they are bottom-dwelling organisms of the sea or ocean and are often fixed to hard surfaces.


Hence, the correct answer is option A.

Note:
 Freshwater includes ponds, lakes, rivers, ponds. Freshwater refers to having low salt concentration (usually less than $1\% $ ). Drinking water is known as anthropogenic water. Zooplankton is the one of the microscopic animals. Phytoplankton are microscopic plants.