* Metabolic byproducts: Substances produced as a result of normal metabolic processes, such as carbon dioxide, urea, and uric acid.
* Excess substances: Substances that are taken in but not needed by the body, such as excess water, salts, and vitamins.
* Toxic compounds: Substances that can be harmful to the body if they accumulate, such as toxins and heavy metals.
Key characteristics of excretion:
* Elimination: The waste products are removed from the body.
* Waste products: The substances removed are not useful to the organism and may even be harmful.
* Specific organs: Excretion often involves specialized organs and systems, such as the kidneys, lungs, skin, and liver.
Examples of excretion:
* Urination: The kidneys filter waste products from the blood and excrete them as urine.
* Breathing: The lungs expel carbon dioxide, a waste product of cellular respiration.
* Sweating: The skin releases sweat, which helps to regulate body temperature and remove some waste products.
* Defecation: The intestines eliminate undigested food and other waste products as feces.
In essence, excretion is a crucial biological process that maintains homeostasis by removing waste products and preventing their harmful accumulation in the body.