In biology, two types of living organisms are classified as colonial. Firstly, those that are composed of a large number of cells. However, these cells do not form organs - their functions are very poorly differentiated. Also, this group of organisms differs in that their cells do not form tissues. The next category is the individual organisms that accumulate in the colony. Individuals in such colonies have a very similar genotype; there can be several in the colony. Biologists attribute sea sponges, corals, and algae to this type.
Green algae
Colonial algae includes many of the green algae department. This category is one of the most numerous in botany - up to 20 thousand different species belong to it. The vast majority of species of green algae can live only in freshwater bodies. Although there are also marine species.
Green algae are represented by five classes. These include the so-called volvox, protococcal, as well as ulotrix algae. The names of these classes come from the Latin language.
Alga Ulotrix
This type is very common in rivers and other fluid bodies of water. Typically, its colonies cover objects under water. Tina consists of threads. At the beginning of the growth cycle, the threads are attached to their base with the help of a rhizoid - an elongated cell. Ulotrix is a colonial algae that propagates in three ways: sexual, asexual, and also vegetative. This species lives both in sea water and in fresh waters. The most common type of ulotrix is the so-called belted ulotrix.
The second type of propagation occurs with the help of zoospores ripening inside the cells - oval-shaped cells with flagella on the front edge. The daughter zoospores, after leaving the mother cell, are still close to it for some time. Then they fall on the underwater object and settle on it. Germinating, zoospores become an adult.
Volvox algae
Colonial algae also includes volvox - algae, whose body consists of active flagellum cells. This type has evolved from the most primitive forms - amoebas. Despite the fact that among volvox there are colonial organisms, most of them are still unicellular. Stands of both types contain 1 core. In these types of algae, reproduction occurs in two ways - sexual and asexual. Colonial volvox is usually represented by many cells - their number ranges from 500 to 60 thousand. Algae has the shape of a ball with a diameter of about 2 mm. Inside it is filled with mucus. If we follow the movement of the Volvox colony, we can see that it is not random, but coordinated. This is due to the fact that the cells are interconnected using special bands.
Evdorina and Pandorina - the most famous volvox
Bright representatives of the volvox class, eudorin and pandorin, also belong to colonial algae. The eudorin colony usually consists of 32, 64 or 128 individuals. The cells are in a small lump of mucus, usually forming a spherical shape. Pandorina is also a spherical colony of algae. However, she is also mobile. Pandorin is usually found in the same place as eudorin.
Volvox and evolution
Volvox is an example of colonial algae that has had a great influence on the evolutionary process. With the Volvox, it occurred in two important directions. Firstly, during the evolution, the volvox cells divided their cell functions into normal and sexual. As you know, the latter method is one of the most important for the emergence of a multicellular biological organism. The second direction of evolution of the Volvoxians is their loss of activity. This direction has led to the appearance of terrestrial plants.
Protocol algae
Colonial algae also include protococci. Algae are beneficial organisms that are also cultivated by humans under artificial conditions. One of the first cultivated species is precisely the protococcal. The names of algae, which are most often used in industry, are chlorella and stagedesmus. They reproduce in a quick and easy way - there is no sexual reproduction, colony growth occurs due to the formation of daughter cells.
Algae are one of the oldest living inhabitants of the planet. This species (including colonial) is of great importance for life. Colonial algae have the ability to absorb the rays of the sun falling on the surface of the ocean. They also produce a large amount of organic matter. With the help of algae, ocean inhabitants get oxygen, and carbon dioxide is absorbed by the colonies. They are also used by humans - for various chemicals, in medicine, radiology, and surgery. Vital products of colonial algae are used in industry for the production of plastics, paints, resins, paper.