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Respiration is the biochemical process in which the cells of the organism obtain energy by combining oxygen and glucose and resulting in the release of carbon dioxide, water and ATP.

Respiration is completed in following steps:

Step- 1 Gaseous exchange

Living organisms must be able to take oxygen from the air and get rid of carbon dioxide and water to the air. Swapping oxygen for carbon dioxide in this way is called gas exchange. Gaseous exchange is often referred to as external respiration to distinguish it from cell respiration. Exchange of gases between the animal body and its external environment also called ventilation or breathing.

Step- 2 Cellular Respiration

Cellular respiration is the process of stepwise biological oxidation of organic molecules to release energy, which is stored in readily usable form in ATP. During the process molecular oxygen is used and CO2 and water are produced.

Image showing general features of respiration.

Image Showing General Features of Respiration.

Image showing general features of respiration.

Respiratory Exchange in Different Animals

All animals exchange gases with their surroundings by the mechanism of diffusion. In animals with a closed circulatory system (such as birds, mammals, reptiles, and some amphibians), gas exchange takes place across the capillaries. A gas diffuses across a membrane from outside where its concentration (partial pressure) is higher than inside where its concentration is lower. Thus oxygen is taken up and carbon dioxide is released from the respiratory surface.

Gas exchange through the general body surface in earthworm – cutaneous respiration

In earthworms, gaseous exchange occurs through skin and is called cutaneous respiration. These do not have specialized respiratory organs, but their skin is thin, moist, highly vascular and permeable to gases. Skin is kept moist by the mucus, secreted by glandular cells of epidermis and by the coelomic fluid which constantly oozes out through dorsal pores. When blood circulates through cutaneous capillaries, exchange of gases occurs between blood and atmosphere and oxyhaemoglobin is formed. In case oxygen is not available, earthworms can survive by anaerobic respiration for 6 to 30 hours. Earthworms asphyxiate when skin gets dried up.

Even frog shows some cutaneous respiration (respiration through skin) across their moist skin, particularly during hibernation when they become inactive during the winter to avoid cold. However, frogs are mainly lung breathing animals.

Tracheal System in Cockroach

Like majority of insects, cockroach respires by means of internal tubes called tracheae that open through 10 pairs of small holes called spiracles present on the lateral side of the body. Thin branching tubes (tracheal tubes subdivided into tracheoles) carry oxygen from the air to all the parts. The opening of the spiracles is regulated by the sphincters. Exchange of gases takes place at the tracheoles by diffusion. Excretion is performed by Malpighian tubules. Each tubule is lined by glandular and ciliated cells. They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic. In addition, the fat body, nephrocytes and urecose glands also help in excretion.

Image showing Tracheal system in a cockroach.

Image Showing Tracheal System in a Cockroach.

Image showing Tracheal system in a cockroach.

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