This article will acquaint the reader with the structure of the simplest organisms, namely, it focuses on the structure of the contractile vacuole, which performs an excretory (and not only) function, talks about the meaning of protozoa and describes the ways of their existence in the environment.
Contractile vacuole. Concept
Vacuole (from the French vacuole, from the Latin word vacuus - empty), spherical-shaped small cavities in plant and animal cells or unicellular organisms. Contractile vacuoles are primarily common among the simplest organisms that live in freshwater, for example, among protists, such as the amoeba proteus and the ciliate slipper, which received such an original name because of the shape of the body, similar to the shape of the sole of a shoe. In addition to the protozoa listed above, identical structures were also found in the cells of various freshwater sponges that belong to the Badyagaceae family.
The structure of the contractile vacuole. Features
The contractile vacuole is a membrane organoid that ejects excess fluid from the cytoplasm. The localization and structure of this apparatus varies in different microorganisms. From a complex of vesicular or tubular vacuoles called spongia, fluid enters the contractile vacuole. Thanks to the constant work of this system, a stable volume of the cell is maintained. Protozoa have contractile vacuoles, which are an apparatus that regulates osmotic pressure, and also serves to excrete decay products from the body. The body of the simplest consists of only one cell, which, in turn, performs all the necessary life functions. Representatives of this sub-kingdom, such as the ciliate slipper, amoeba, and other unicellular organisms, have all the properties of an independent organism.
The role of protozoa
The cell performs all vital functions: excretion, respiration, irritability, movement, reproduction, metabolism. The simplest are ubiquitous. The largest number of species lives in marine and fresh waters, many inhabit moist soil, can infect plants, live in the bodies of multicellular animals and humans. In nature, protozoa perform a sanitary role, they also participate in the cycle of substances, they are food for many animals.
Contractile vacuole in the common amoeba
Amoeba ordinary - a representative of the class of rhizomes,does not have, unlike other representatives of a permanent body shape. Movement is carried out with the help of pseudopods. Now let's figure out what function the contractile vacuole performs in an amoeba. This is the regulation of the level of osmotic pressure inside her cell. It can be formed in the amoeba proteus in any part of the cell. Through the outer membrane, water from the environment enters osmotically. The concentration of dissolved substances in the amoeba cell is higher than in the environment. Thus, a pressure difference is created inside the cell of the simplest and outside it. The functions of the contractile vacuole in an amoeba are a kind of pumping apparatus that removes excess water from the cell of a simple organism. Amoeba Proteus can release accumulated liquid into the environment in any part of the body surface.
This function of the contractile vacuole is acceptable for the simplest organisms living in freshwater. In parasitic and marine forms that live in an environment where the osmotic pressure is higher than in fresh water, these primitive apparatuses contract very rarely or are usually absent. Around the contractile vacuole in the most protozoan organisms, mitochondria are concentrated, delivering energy to perform osmotic work.
In addition to osmoregulatory, it performs the function of respiration in life, since as a result of osmosis, incoming water delivers oxygen dissolved in it. What other function does the contractile vacuole perform? It also performs an excretory function, namely, together with water, metabolic products are excreted intheir environment.
Respiration, excretion, osmoregulation in shoe ciliates
The body of protozoa is covered with a dense shell, which has a constant shape. It feeds on both bacteria and algae, including some protozoa. The organism of ciliates has a more complex structure than that of an amoeba. In the shoe cell, two contractile vacuoles are located in front and behind. In this apparatus, a reservoir and several small tubules are distinguishable. Contractile vacuoles are constantly, thanks to this structure (from microtubules), in a permanent place in the cell.
The main function of the contractile vacuole in the life of this representative of the protozoa is osmoregulation, it also removes excess water from the cell, which enters the cell due to osmosis. First, the leading channels swell, then the water from them is pumped into a special reservoir. The reservoir is reduced, separated from the leading channels, water is thrown out through the pores. There are two contractile vacuoles in the ciliate cell, which, in turn, act in antiphase. Due to the operation of two such devices, a continuous process is ensured. In addition, water continuously circulates due to the activity of contractile vacuoles. They contract one by one, and the frequency of contractions depends on the ambient temperature.
Thus, at room temperature (+18 - +20 degrees Celsius), the frequency of vacuole contractions is, according to some sources, 10-15 seconds. And given that the natural habitatshoes are any fresh water reservoirs with stagnant water and the presence of decaying organic substances in it, the temperature of this environment changes by several degrees depending on the season and, therefore, the frequency of contractions can reach 20-25 seconds. In an hour, the contractile vacuole of the simplest organism is able to throw water out of the cell in quantity. commensurate with its size. They accumulate nutrients, undigested food residues, metabolic end products, and oxygen and nitrogen can also be detected.
Wastewater treatment with the simplest
The influence of protozoa on the cycle of substances in nature is of great importance. In reservoirs, due to the descent of wastewater, bacteria multiply in large numbers. As a result, various simple organisms appear, which use these bacteria as food and thus contribute to the natural purification of water bodies.
Conclusion
Despite the simple structure of these unicellular organisms, whose body consists of one cell, but performs the functions of a whole organism, surprisingly adapted to the environment. This can be observed even in the example of the structure of the contractile vacuole. To date, the enormous importance of protozoa in nature and their participation in the cycle of substances has already been proven.
