Question

In aquatic ecosystems, phytoplankton and other photosynthetic organisms appear in the upper layer of the water, but not deeper layers. Which statement explains this distribution?
A) The deeper layers are too dark for photosynthesis to occur.
B) The deeper layers are too cold for photosynthesis to occur.
C) The deeper layers have too little oxygen for photosynthetic organisms to survive.
D) The deeper layers have too much carbon dioxide for photosynthetic organisms to survive.

Answer 1

Answer:

A) The deeper layers are too dark for photosynthesis to occur.

Explanation:

Photosynthesis is a unique process to autotophic organisms. It involves the use of light energy from the sun to manufacture organic molecules (food). As the phenomenon implies i.e. PHOTO - LiGHT, light is an unnegotiable requirement for photosynthesis to take place. Autotrophs are able to perform this process because they contain pigments (Chlorophyll) that can trap energy from sunlight.

In an aquatic ecosystem, phytoplanktons and other photosynthetic organisms like aquatic plants are the autotophic organisms. They are found in the upper layer of the water so that they can reach light from the sun. The light from the sun cannot travel deep down the water making the deep parts of the ocean be deprived of light.

This is the reason why photosynthetic organisms cannot be found in the deep parts of the water as they will be unable to have access to the light from the sun in order to perform photosynthesis.

Answer 2

Answer: alternative A

Explanation: The deeper the layer in water, the less light reaches it. In deeper layers, therefore, it becomes difficult, if not impossible, to photosynthesis to occur. Having in mind that phytoplankton  and photosynthetic organisms depend on photosynthesis to survive, they won't appear in such dephts.