Question

Assertion: In an open water zone upto the depth to which light can penetrate, called the photic zone.
Reason: The photic zone is categorized into euphotic and disphotic zone.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Hint: The photic zone, epipelagic zone, euphotic zone, or sunlight zone is the uppermost layer of the sea which receives the sunlight which leads the phytoplankton to perform the photosynthesis process. The whole process undergoes chemical, physical and biological processes which help in the supply of nutrients into the upper water column.

Complete answer: The topmost layer of the ocean which receives the light is called the photic zone. The photic zone is categorized into the euphotic and disphotic zone. The euphotic zone is the topmost layer of the ocean where sufficient light for photosynthesis is found is called the disphotic zone. In the photic zone, almost all the autotrophs present in this layer of the ocean have access to the light. The organism in the ocean that performs photosynthesis lives in this zone so that they can have access to the light from the sun.
When the light from the sun enters the water, it gets absorbed and reflected by the particles in the water. The more the depth of the water, the less amount of light penetrates it because the light gets reflected back from various layers of the water. There are phytoplanktons present in the ocean which utilize the sunlight for the process of photosynthesis by various biological, chemical and physical processes. This process of photosynthesis helps in the synthesis of nutrients in the water which can be consumed by small fishes.
Hence, the correct option is B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Note: Phytoplanktons are the key source of food in the ocean and other water bodies. They remain mainly on the surface which comes in the photic zone which helps them to produce their own food and helps various marine animals to consume the food made by them.