More than 7000 species are classified as flagellates. By the nature of their nutrition and metabolism, they are divided into plants and animals.
Animal flagellates include bodo, which lives in the same water bodies as the plant flagellate euglena green.
Bodo moves in water with two flagella located at the front end of the body. This animal does not have chlorophyll, therefore only heterotrophic nutrition is characteristic of it. It is fed by bacteria, unicellular algae and microscopic animals, which the Bodo drives to the mouth with the help of flagella and swallows them.
The bodies of colonial flagellates are composed of many cells.
Volvox is a large spherical colony with a diameter of about 8 mm, on the surface of which cells connected by cytoplasmic “bridges” are located in one layer, and the inner cavity of the ball is occupied by liquid mucus. The cells have flagella facing outward.
With asexual reproduction, daughter colonies are formed in colonial flagellates.
The first colonies arise due to the fact that after division the cells do not diverge, but remain together.
During sexual reproduction of volvox, male germ cells form 5-10 cells, female – 25-30. Thus, there are different types of cells in a Volvox colony, which is typical for multicellular animals.
Volvox can serve as a model showing how multicellular organisms could have evolved from unicellular organisms.