Algae are mostly water organisms

Algae are a wide group of mostly water. From unicellular to multicellular photosynthetic autotrophic organisms, like plants known as phytoplankton. Also known as a living organism, plant without roots, leaves or flowers. There are more than 25.000 species, most of the sea algae in the ocean and the rest are freshwater algae. For instance, seaweed or sea grass, water flowers and aquatic moss are all forms of algae.

In fact, they are of different sizes. From tiny picoplankton to giant grass in the oceans, which are up to 50 m in length. A common feature of the performance of photosynthesis, in which as a by-product is oxygen. Exceptions are cyan (eukaryotes), whose cells contain ogan, including core and mitochondria membrane separated from the cytoplasm. Eukaryotic have chloroplasts containing the pigment to absorb solar energy during the process of photosynthesis. In most, primary pigment is chlorophyll, along with other pigments which are giving them a characteristic coloration (phycoerythrin - red, phycocyanin, allophycocyanin - blue, fukoksantin - brown, violaxanthin - purple and others).

Macroalgae are not true plants despite the many similarities to land plants. For instance, they lack a specialized vascular system (conduction system for nutrients and fluids). Stems, roots and leaves (directly from the water column taking liquid, nutrients and gases). The closed reproductive organs (cone or flower).

For flowering need sunlight, minerals and aquatic life to prevent it's drying out. Biochemical reactions allow them to create their own food from surrounding minerals and gases.

Can be used as a food additive. Brown, which are collected, milled and dried, produces flour (porridge), which is used as a food additive for livestock. Can be used as a highly valuable fertilizer because the high concentration of fiber retains moisture and the concentration of minerals that comprise enriching soil and is a source of trace elements. Some macroalgae have the ability to absorb heavy metal ions from contaminated water (zinc or cadmium). Drain water from farms often contain a large amount of organic substances, which create problems for aquatic life in nearby waters. They are able to take advantage of contamination as a source of nutrients for their metabolism and thus purify the water. Isolated substances such as alginates, carrageenan and agar, extracted from various red and brown and are widely used in various industries (cosmetics, pharmaceutical, chemical, food processing, textile and other). 
 

Algae belong to the kingdom of prokaryotes and protists and are divided into:

Protists:

- Bacillarophyceae (algae diatoms)
- Chlorophyceae (green algae)
- Chrysophycae (golden algae)
- Dinophyceae (dinoflagellates)
- Phaeophyceae (brown algae)
- Class Rhodophyceae (red algae)

Prokaryotes:

- Class Cyanophyceae (blue-green)