What are the main features that are characteristic of algae? How do they differ from other plants? What functions do they perform? We will deal with this below.
Until the middle of the 20th century, algae, along with mushrooms,lichens and bacteria were referred to inferior plants. Now this concept has lost its relevance. The term "algae" is purely biological, not systematic. The characteristics of algae are ambiguous, since they can belong to different departments and categories.
The concept itself does not mean a concrete species, butgroup of organisms, which are united by a number of common features. They represent heterogeneous multicellular, unicellular and colonial organisms. The main signs characteristic of algae are absence of blood vessels, presence of chlorophyll in cells, habitation in the aquatic environment. More than a hundred thousand algae are known. Their sizes can range from one micrometer to 40 meters in length.
Numerous species and classes of algaeunite in the departments of green, brown, golden, yellow-green, cryptophyte. Almost all of them belong to the subregion of Algae in the kingdom of the plant. Exceptions are blue-green algae. They are classified as cyanobacteria.
Характерные для водорослей особенности – это the presence of photoautotrophic nutrition, that is, the realization of photosynthesis, thanks to the presence of chlorophyll. They absorb the substances from the environment by the entire surface of the body.
The main features characteristic of algae,are also the absence of a clear division of the body into organs. Their body does not have roots, stem, leaves, but it differs in structure from different representatives of algae. It can look like thin threads, plates, ribbons, etc.
Algae can have a variety of colors.The green color of many species is determined by the presence of chlorophyll, red, yellowish and other colors indicate the presence of various pigments. They do not form flowers, reproduction in different species occurs by spores, vegetatively or sexually.
Изначально им присущ водный образ жизни, однако some species have adapted to life in soils, trees and even rocks. Algae of small size can be attached to other algae or live on the bottom of water bodies, being a part of the benthos.
Некоторые мелкие виды свободно плавают в верхних layers of water together with plankton. There are also parasitic species that are introduced into the shells of organisms. The largest sizes are brown algae. Growing up, they form whole forests under the water, providing shelter to fish and other animals.
As a rule, they live on the depths to whichstill able to penetrate the sunlight. The maximum depth is 200 meters, although most species do not fall below forty. On the surface, algae often grow in conditions of good humidity. They can appear even on a fence or a house. Entering with the mushrooms in symbiosis, some algae merged with them into one, forming a separate species of organisms - lichens.
За счет активного фотосинтеза водоросли являются the main producers of organic substances in water. Due to the circulation of carbon dioxide and oxygen, they are part of the global cycle of substances. People use them as biofuels, they use it to purify water.
Algae serve as food for many living beings.They are rich in iodine and minerals, so some species are consumed by people, for example, ulva, sea kale. They are used in pharmaceutics, as well as in the chemical industry, to produce agar-agar, cellulose, acetic acid, and alcohol.
