Question

(i) Why is the removal of feces from the alimentary canal not considered as excretion?
(ii) Name the waste products excreted by lungs and skin.

Answer 1

Excretion:

1. Metabolic reactions result in the release of energy and form other substances that are not required by the body.
2. These unwanted products are called waste products.
3. The process by which the waste products that are harmful to the body are removed from the body is known as excretion.
4. The organs that eliminate the excretory products are called excretory organs.

Defecation:

1. The process of removal of feces from the body is known as defecation.
2. This removes the undigested food (produced as feces) from the alimentary canal through the anus.
3. Since fecal matter is not formed by metabolic reactions, this process cannot be considered excretion.

Lungs and Skin:

1. The lungs are the respiratory organs that help in the exchanges of gases - Oxygen and Carbon dioxide between the body and the environment.
2. The skin is the outer layer or covering that is present throughout the body and protects the body from heat, light, injury, microbes, etc.
3. The lungs excrete the gas Carbon dioxide by expiration or breathing out.
4. The skin eliminates or excretes metabolic wastes such as nitrogenous wastes, salts, and excess water by sweating.