19. The fishes are considered ectothermic, what does that mean?
The prefix "ecto" means outside and "thermic" means temperature. Many animals receive their primary body temperature from the environmental temperature. It is an advantage because it requires less food intake than an endotherm. We are endotherms which require a large daily intake of food. This food is turned into calories, some of which meets our physiological needs and the excess calories are turned into heat. This excess heat keeps us warm and within limits we can be active when ectotherms cannot (like cold climates).