Not all animals have lungs. Many animals live in environments where lungs would be efficient enough for survival. Gills are another type of respiratory system, which are very efficient at removing oxygen from water: there is only 1/20 the amount of oxygen present in water as in the same volume o...

Respiration is the process by which oxygen is delivered to cells and body systems for use. It consists of levels, several of which are breathing, internal respiration, and external respiration. Breathing is the process by which air is inhaled and exhaled through the mouth. External respiration is th...

Carbohydrates are a good source of fuel while lipids are a good storage fuels. Skeletal muscles and the liver store significant amount of carbohydrates. Triacylglycerols are stored in adipose tissues. At the starting of race, the body is resting. Glucose is then taken into the body, storing in the...