What are the main characteristics characteristic of algae? How do they differ from other plants? What functions do they perform? We will deal with this below.
What is algae?
Until the middle of the 20th century, algae, along with fungi, lichens and bacteria, were attributed to lower plants. Now this concept has lost its relevance. The term “algae” is purely biological, not systematic. The characteristics of algae are ambiguous, as they can belong to different departments and categories.
The concept itself does not mean a specific species, but a group of organisms that are united by a number of common features. They represent heterogeneous multicellular, unicellular and colonial organisms. The main signs characteristic of algae are the absence of blood vessels, the presence of chlorophyll in the cells, and habitat in the aquatic environment. More than one hundred thousand algae are known. Their sizes can range from one micrometer to 40 meters in length.
Numerous species and classes of algae are combined into departments of green, brown, golden, yellow-green, cryptophytic. Almost all of them belong to the kingdom of Algae in the kingdom of plants. An exception is blue-green algae. They are classified as cyanobacteria.
Key features
The characteristic features of algae are the presence of photoautotrophic nutrition, that is, the implementation of photosynthesis due to the presence of chlorophyll. They absorb substances from the environment over the entire surface of the body.
The main signs characteristic of algae are also the lack of a clear separation of the body into organs. Their body has no roots, stem, leaves, but differs in structure in different representatives of algae. It can take the form of 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 using spores, vegetatively or sexually.
Habitat
Initially, they have an aquatic lifestyle, but some species have adapted to life in soils, on trees and even rocks. Small algae can attach to other algae or live on the bottom of ponds, being part of the benthos.
Some small species swim freely in the upper layers of water along with plankton. There are parasitic species that invade the shells of organisms. The largest sizes are brown algae. Growing, they form entire forests underwater, providing shelter for fish and other animals.
As a rule, they live at depths to which sunlight is still able to penetrate. The maximum depth is 200 meters, although most species do not fall below forty. Algae often grow on the surface in conditions of good humidity. They can even appear on a fence or house. Entering symbiosis with mushrooms, some algae merged with them as a whole, forming a separate species of organisms - lichens.
Biological significance
Due to the active photosynthesis, algae are the main producers of organic substances in water. Due to the circulation of carbon dioxide and oxygen, they are part of the global circulation of substances. People use them as biofuels, use them for water treatment.
Algae serve as food for many living things. They are rich in iodine and minerals, so some species are used by people, for example, ulva, seaweed. They are used in pharmaceuticals as well as in the chemical industry to obtain agar-agar, cellulose, acetic acid, alcohol.