Today green algae is considered the most extensive group, which has about 20 thousand species.These include both single-celled organisms, and colonial forms, as well as plants with large multicellular thallus.There are representatives that live in water (salt and fresh), and the organisms adapted to survive on land in conditions of high humidity.
Division Green algae: a brief description of
The main feature of this group is their color scheme - for all kinds of characteristic green or greenish-yellow color.This is due to the main pigment cells - chlorophyll.
As already mentioned, the department combines very different representatives.There are unicellular and colonial forms, as well as multicellular organisms with a large, differentiated thallus.Some representatives unicellular move via flagella multicellular usually attached to the bottom or live in the water column.
Although there are organisms with bare cells, has the majority of the cell wall.The main structural component of the cell wall is cellulose, which, incidentally, is considered an important characteristic of a systematic.
number, size and shape of the chloroplast in the cell may be different depending on the plant species.The main pigment is chlorophyll, in particular, a and b form.As for carotenoids in plastids it contained mainly beta-carotene and lutein, as well as small amounts neosantina, zeaxanthin and violaxanthin.Interestingly, some of the cells of organisms have an intense yellow or orange color - this is due to the accumulation of carotenes is the chloroplast.
Some unicellular green algae have a specific structure - the eye that responds to light blue and green spectrum.
is stored main product is starch granules which are contained mainly in the plastids.Only a few members of the order replacement substances are deposited in the cytoplasm.
Division Green algae: reproduction methods
In fact, for the representatives of this order are characterized by practically all the possible ways of reproduction.Vegetative propagation can occur by dividing cells (unicellular representatives without cell wall), the fragmentation of the thallus (this method is typical for multicellular and colonial forms).Some specific types of formed nodules.
Asexual reproduction is represented by the following forms:
- zoospores - cells with flagella, capable of active movement;
- aplanospory - have no such dispute flagellar apparatus, but well developed contractile vacuole;cells are unable to active movement;
- autospores - this type of dispute is related primarily to the adaptation to the environment.In this form, the body can wait out the dry land, and other adverse conditions.
Sexual reproduction can also be varied - this oogamy and heterogamy and hologamiya and isogamy and conjugation.
Squad Green algae: characterization of some representatives
This group includes many well-known representatives of the plant world.For example, single-celled algae Spirogyra and Chlorella are also included in the squad.
Chlamydomonas - fairly well-known genus of green algae, which is of practical importance.This group includes single-celled organisms with a red eye and a large chromatophores, which contain pigments.It chlamydomonas causes "blooming" ponds, pools and aquariums.In the presence of sunlight organic substances produced by photosynthesis.However, this organism can absorb substances from the external environment.Therefore Chlamydomonas often used for water purification.
