Life Processes in Animals - Respiration in Animals

Respiration is a vital biological process where food (glucose) is broken down in the cells of an organism to release energy. This is called cellular respiration.

Aerobic respiration occurs in the presence of oxygen ($O_2$), where glucose is completely broken down into carbon dioxide ($CO_2$), water ($H_2O$), and energy.

Anaerobic respiration occurs in the absence of oxygen. In organisms like yeast, it produces alcohol and $CO_2$. In human muscle cells, during heavy exercise, it produces lactic acid, leading to muscle cramps.

Breathing is the physical process of inhaling air rich in oxygen and exhaling air rich in carbon dioxide using respiratory organs.

The breathing rate is the number of times a person breathes in one minute. On average, an adult human at rest breathes $15 - 18$ times per minute.

During inhalation, the diaphragm moves down and the rib cage moves outwards, increasing the space in the chest cavity and allowing air to rush into the lungs.

During exhalation, the diaphragm moves up to its former position and the rib cage moves inwards, decreasing the space and pushing air out of the lungs.

Different animals have different organs for gas exchange: Insects use spiracles and tracheae; Earthworms use their moist skin; Fish use gills; and Frogs use both lungs and their moist skin.