The process by which animals rid themselves of waste products is called excretion. Wastes can consist of nitrogenous by-products and metabolic waste products such as carbon dioxide, excess water, excess salts, ammonia, sweat, urine and feces. The organisms control osmotic pressure – the balance between inorganic ions and water- and maintain acid-base balance through this process. It also helps in promoting homeostasis, a process that helps maintain the stability that helps the organs or biological systems to survive.
Excretion is also done by green plants, which produce water as respiratory products. Carbon dioxide released by humans during exhalation is utilised by green plants for the process of photosynthesis. Plants get rid of excess water by transpiration and guttation.
In general, plants contain vacuoles which enclose all other metabolic waste that is generated. They are in a leaf cell, which allows vacuoles to crystallize. We usually see the vacuoles get filled, and then the leaf drops. These are known as Excretophores. Saps and gums are also the types of excretion displayed by plants, which we see with our naked eye.
The excretory system in human beings expel wastes that are usually toxic when they accumulate in the body. Sweating is also a type of excretion displayed by humans. Sweat also helps in bringing down the temperature of the body because high temperatures can be fatal or cause life-threatening injuries. Dogs have a very limited number of sweat pores and they discharge excess body temperature through panting.
Unicellular organisms like amoeba also produce metabolic waste products and they rid themselves of these by a process called diffusion. But they also use this as a method for respiration since they obtain oxygen through this process.
A virus does not consume nutrients like any other living organisms hence they do not produce wastes that are usually associated with metabolism.
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