Why are the cell structures shaped so different

 Cells have different shapes because they do different things. ... The shapes of cells have evolved to help them carry out their specific function in the body, so looking at a cell's shape can give clues about what it does. Neurons are cells in the brain and nervous system.

Explanation:

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.