Seaweed are an extensive group of photosynthesizing organisms including 12 departments and more than 40 thousand types. Seaweed mainly live in water, but some of them adapted to life on the land — in the soil, on stones and trunks of trees.
Instruction
1. The body of seaweed is not differentiated on vegetative bodies (stalk, a leaf, a root), it is presented sloyevishchy, or tallomy. For this reason they are often called sloyevishchny, or tallomny, plants. Seaweed can freely float in water or be attached to various objects, for example, to soil and stones at the bottom of a reservoir.
2. More than 40 thousand species of seaweed are known, they can be divided into two subkingdoms — the Real seaweed and Bagryanki. The real seaweed are subdivided into several departments — Green, Golden, Diatomic, Brown, Harovy. They differ from each other in a set of photosynthesizing pigments, structure of a tallom, features of reproduction and cycles of development.
3. Cages of the majority of seaweed do not differ considerably from typical cages of the higher plants, but they have a number of features. The cellular cover consists of cellulose and pectinaceous substances, at many seaweed additional components, such as iron, lime, alginic acid and others are its part. Cytoplasm, as a rule, is located a thin layer along a cellular wall, surrounding with itself big central vacuoles.
4. At cages of seaweed there are chromatophores which differ from chlorolayers of the higher plants. They are more various in structure, to a set of pigments, in a form and the sizes. Chromatophores of seaweed can be tape-like, lamellar, disk-shaped, star-shaped or cup-shaped.
5. A morphological variety is characteristic of seaweed, among them is monocelled (a chlorella, a hlamidomonada), colonial (volvox) and also multicellular. Among multicellular seaweed lamellar and nitchaty forms are known. Their sizes also differ in a big variety — from 1 micron to dozens of meters.
6. The majority of seaweed are eukariota, only blue-green and pro-chlorophyto-blue-green - prokariota. At cages eukariot there are chlorolayers which contain various pigments: carotinoids, chlorophyll or fikobilina characteristic of red seaweed. However a part of seaweed lost photosynthesizing pigments and passed to heterotrophic food.
7. Seaweed breed sexless and sexually, at some each individuals forms disputes and gametes seasonally, at others different individuals perform functions of sexual and asexual reproduction. Sporofita form disputes, and gametogophytes are gametes. Strict alternation of generations of the sporofit and a gametogophyte is characteristic of many seaweed (brown, red and some green). Vegetativno seaweed breed sites of colonies (diatomic), threads (spirogir) and also cell division (euglena).