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One of the most common evidences that a paramecium is maintaining homeostasis is the pumping of water from the vacuoles present in its body.
The paramecium is a protozoan that lives in aquatic environments, mainly those composed of fresh water. The problem with this environment is that water is able to enter the paramecium organism in large quantities and this can promote the disruption of the organism through lysis of the cell. In this case, homeostasis must act quickly and pump water out of the body, through the cell vacuole.
Homeostasis is a regulatory system of the organism, which must promote the balance of the organism, whenever any external or internal factor tries to harm this balance.