(a) Aquatic ecosystems are rich in diversity. The life inside water is largely influenced by various abiotic factors. The abiotic factors are the chemical and physical components of an environment that affect the organisms living there. The primary abiotic factors that affect the life underwater are temperature, light and availability of oxygen.
(b) Oxygen available to the aquatic organisms is a detrimental factor. If less oxygen is available underwater aquatic animals will not be able to respire and die.
Light is also an important abiotic factor for underwater organisms especially for the aquatic plants. the aquatic plants underwater will not be able to make their food by photosynthesis if proper light is not available.
Temperature also plays an important role. Too low or too high temperature affects the metabolic activities of the organisms.
Depth of water body affects the availability of light and oxygen to the aquatic organisms. Shallow water bodies have light available to more aquatic organisms.
A) gravitropism is how they "know"
Each daughter cell would still have 16 chromosomes
