Question

What is excretion? Why is it important to living things?

Answer 1

Excretion is primarily carried out by the lungs, kidneys and skin in vertebrates. Urine is excreted through the urethra in mammals and metabolic waste products are directly excreted through the surface of the cell in unicellular organisms.

Complete answer:
Excretion is the process of elimination of metabolic waste from the body of an organism. Excretion differs from secretion in the way that the substances removed via secretion perform a specific function before their removal whereas excretion is the removal of waste that serves no purpose for the body of the organism.
Metabolism is the collection of all the chemical reactions that take place during cellular respiration.
These cellular chemical reactions produce various waste products like carbon dioxide, urea, uric acid, water and salts. The collection and storage of these waste products in the body for a long period of time and beyond a certain concentration can be harmful to the body of the organism. The excretory organs of the body remove the concentrated metabolic waste in order to maintain the concentration of waste in the body of the organism. This process of removal of waste from the body of an organism is called excretion.

Note:
The main excretory products in animals are carbon dioxide, urea, ammonia, guanine, uric acid, creatinine. These substances are filtered by the liver and kidneys of animals and are excreted in the form of feces and urine through the excretory system.
The removal of ammonia from the body of an organism through direct or indirect methods is called detoxification.