The definition of calories is a measure of energy in food, specifically the measure of heat needed to raise a kilogram or a gram of water by one degree Celsius.
Darwin noticed that there were different kinds of the same species. For example, he studied four different kinds of finches. Each one had a different beak and are different kinds of food. This was the first time genetic diversity had been so obvious to humans.
Reticulum is the only one I know of that contain lysosmes.
Sun which produces sunlight