Contractile vacuole of protozoa takes part in

• Explain how vacuoles, present in microorganisms, work to excrete waste • Describe the way in which flame cells and nephridia in worms perform excretory functions and maintain osmotic balance • Explain how insects use Malpighian tubules to excrete wastes and maintain osmotic balance Microorganisms and invertebrate animals use more primitive and simple mechanisms to get rid of their metabolic wastes than the mammalian system of kidney and urinary function. Three excretory systems evolved in organisms before complex kidneys: vacuoles, flame cells, and Malpighian tubules. Contractile Vacuoles in Microorganisms The most fundamental feature of life is the presence of a cell. In other words, a cell is the simplest functional unit of a life. Bacteria are unicellular, prokaryotic organisms that have some of the least complex life processes in place; however, prokaryotes such as bacteria do not contain membrane-bound vacuoles. The cells of microorganisms like bacteria, protozoa, and fungi are bound by cell membranes and use them to interact with the environment. Some cells, including some leucocytes in humans, are able to engulf food by endocytosis—the formation of vesicles by involution of the cell membrane within the cells. The same vesicles are able to interact and exchange metabolites with the intracellular environment. In some unicellular eukaryotic organisms such as the amoeba, shown in Figure 22.9. Some unicellular organisms, such as the amoeba, ingest food by endocytosis. ...

Euglena Euglena are characterized by an elongated cell (15–500 micrometres [1 micrometre = 10 −6 metre], or 0.0006–0.02 inch) with one E. rubra) appear red in sunlight because they contain a large amount of Euglena lack a rigid paramylon, which enables the organisms to survive in low-light conditions. Euglena reproduce asexually by means of

• The rate of output of the contractile vacuole in a fresh-water peritrich ciliate (Carchesium aselli) varies with temperature with a Q 10 of about 2·5–3·2, or a μ of about 17,000, over the range 0–30° C. • There is a slow decline in output during exposure for several hours to high temperatures (25–30° C.). At still higher temperatures (34° C.) a high rate of output is maintained for a few minutes, but swelling and death rapidly ensue. • The frequency of uptake of food vacuoles also varies with temperature, increasing from o to about 24° C., but decreasing at higher temperatures. At about o° C. and at temperatures above about 30° C. no food vacuoles are taken up and the adoral cilia remain extended and motionless. • No change in body volume could be detected during exposure to high temperatures (25–30° C.) for two or more hours, even though the rate of vacuolar output was increased to three or four times its normal level at 15° C. It is concluded that the rate of uptake of water from the outside medium must have been increased correspondingly. • It is suggested that temperature affects the permeability of the organism to water, and that the rate of vacuolar output is adjusted accordingly, although on the evidence so far presented other explanations are possible. In many Protozoa, and especially in fresh-water forms, there is a considerable exchange of water between the body and the outside. The contractile vacuole bales out water continually, and there must be a correspond...

A contractile vacuole ( CV) is a sub-cellular structure ( pulsatile or pulsating vacuole. Overview [ ] The contractile vacuole is a specialized type of The contractile vacuole, as its name suggests, expels water out of the cell by contracting. The growth (water gathering) and contraction (water expulsion) of the contractile vacuole are periodical. One cycle takes several seconds, depending on the species and the diastole. The contraction of the contractile vacuole and the expulsion of water out of the cell is called systole. Water always flows first from outside the cell into the The best-understood contractile vacuoles belong to the protists Chlamydomonas) which do possess a cell wall. Through The number of contractile vacuoles per cell varies, depending on the Amoeba have one, spongiome; the contractile vacuole together with the spongiome is sometimes called the "contractile vacuole complex" ( CVC). The spongiome serves several functions in water transport into the contractile vacuole and in localization and docking of the contractile vacuole within the cell. Paramecium and Amoeba possess large contractile vacuoles (average diameter of 13 and 45µm, respectively), which are relatively comfortable to isolate, manipulate and assay. The smallest known contractile vacuoles belong to Chlamydomonas, with a diameter of 1.5µm. In Paramecium, which has one of the most complex contractile vacuoles, the vacuole is surrounded by several canals, which absorb water by osmosis from the ...