Flagellates - protozoa , moving with one or more flagella. Some of them are capable of producing pseudopods. Among them are unicellular monoenergy and polyenergy forms, as well as colonial (for example, Eudorina ) and multicellular ( Volvox ) forms. In general, flagellates tend to have small cell sizes and osmotic feeding, although among them there are also very large phagotrophic forms.
Description
Prior to the separation of protozoa into an independent kingdom, botanists included flagellates in the plant kingdom as “ lower green algae ”, and zoologists attributed them to the kingdom. Animals as a class composed of the simplest type with division into plant (having chloroplasts) and animal flagellates (lost chloroplasts). In a certain period of development, protistology was considered as a type of the kingdom Protista ( lat. Mastigophora ), then as a subtype of the Sarcomastigophora type. Subsequently, using ultrastructural and molecular genetic studies, it was proved that the flagellates were a polyphyletic group .
The simplest of this group have one, two or many flagella. Not only unicellular flagellates are known, but also colonial species consisting of 4, 8, 16, 32 and even 20 thousand cells.
Flagellates reproduce by division . In unicellular species, the nucleus is first divided, and the remaining organelles grow and regenerate in the process of division. Then the cell is overtightened. Under favorable conditions, the next day the affiliated flagellates can divide.
Selection takes place with the help of contractile vacuoles .
All plant flagellates can photosynthesize and feed like plants, because their cells have a green pigment - chlorophyll . Some of the flagellates, for example, euglena green , feed on the light like plants, and in the dark like animals or mushrooms, ready-made organic substances. All vegetable flagellates lead a free lifestyle in the aquatic environment.
Other flagellates do not have chloroplasts . Among them are free-living individuals, but their main representatives have moved to a parasitic way of life in plant and animal organisms.
Also found flagellates, which are human parasites. The most famous of them are trypanosomes . They cause sleeping sickness. The vector of trypanosomes is a tsetse fly.
Other parasitic flagellates, from the genus of Leishmania, are transmitted by mosquitoes and cause diseases such as cutaneous and visceral leishmaniasis ( pendinsky ulcer and kala-azar ) in humans.
Under unfavorable conditions, flagellates form cysts, which also serve for settlement. For example, Giardia .
Perhaps from the collar flagellates originated animals .
Literature
- Life of animals. T.1. - M .: Enlightenment.
- Biology. Animals 7th grade. - Vlados.
- Bichenous // Encyclopedic Dictionary of Brockhaus and Efron : 86 t. (82 t. And 4 extra.). - SPb. , 1890-1907.