In gametogenesis , germinal cells multiply by mitosis and mature garnetes are formed by meiosis.
My guess is that fat-soluble toxins that may occur in freshwater ecosystems would most affect apex species in these ecosystems. This is because fat-soluble toxins are stored in the fat reserves of animals, and then bioaccumulate up the food chain. So in this case, most of the toxin is not secreted, but stored within the food chain, and bioaccumulates, with the concentration becoming higher the further up the food chain.
The answer is stroke. This means that formation of plaque in the blood vessels that serve the brain cause thickenning of the inner walls of the vessels. When the plaque ruptures, a blood clot forms and blocks blood passage to a particular region of the brain served by the vessel. This stifles oxygen supply to the respective part of the brain leading to the death of the cells in the region.
