Practically in every reservoir on the entire surface of the globe you can meet such a unique organism, reminiscent of its composition, a plant, like algae.
What is algae
Algae is a special group of unicellular or multicellular organisms that live mainly in the aquatic environment. This is a fairly large group of lower plants. Their habitat is so great that it can be found everywhere, as in the oceans, and in the seas, lakes, rivers, other water bodies, on wet soil and even bark of trees.
Algae are like unicellular protozoans and multicellular colonies. Shells of multicellular algae consist of cellulose, which are attached to each other from the butt.
They do not have a root system. Instead, algae attach to the surface with the help of special processes - rhizoids.
Algae is the main source of organic matter on the whole Earth. Almost all food chains start with them. Moreover, they serve as a source of nutrition for many inhabitants of the aquatic environment.
Also, algae are suitable for the production of fertilizers, animal feed, and, of course, can be eaten by humans.
Origin of algae
Until now, there is no consensus on the origin of algae and their exact age due to the fact that this species of organisms is represented by a wide variety. Moreover, not a single example of fossil specimens has been preserved and it is impossible to establish what evolutionary stages this type of organisms has gone through.
Biologists around the world are convinced that no plant in the world can compare with the healing power of seaweed, since there is a theory about the origin of life at sea, which means that they contain a unique biological composition.
However, it is believed that green and yellow algae appeared on Earth about 3 billion years ago. Initially, they arose in the form of unicellular and only then colonial. And it was the appearance of this type of organisms that led to the formation of an oxygen atmosphere on the Earth and an ozone layer, which subsequently led to the birth of life. About a billion years ago, multicellular complex algae appeared.
Types of algae
More than 30 thousand species of algae are known in modern biology. However, all of them can be combined into special groups:
- Euglenic or unicellular. The smallest algae.
- Pyrophytic algae, the membrane of which consists of cellulose.
- Diatoms. They consist of cells with a so-called double shell.
- Golden seaweed. Here it is possible to meet both unicellular and multicellular, but all of them are fresh-water golden or brown-yellow in color.
- Yellow-green. They are often combined with the previous group.
- Green. They can be detected with the unaided eye, for example, on the bark of trees.
- Charcoal seaweed. These are multicellular algae, which are often combined with green algae. The height of the stem varies from 2.5 cm to 10 cm.
- Red algae. So called because of the presence in their composition of a special element - phytoerythrina, which turns them into red. These algae live mainly in great depths in the seas.
- Brown seaweed. The most perfect kind. They dwell in great depth and are able to create thickets, such as, for example, in the Sargasso Sea. Rizoids are tightly attached to the surface, so it is almost impossible to tear them apart.
The spread of algae in nature
According to the mode of existence, algae are divided into two large groups: these are aquatic and live on land - outside water.
In turn, water can be divided into several categories:
- Plankton. Are in the water in a suspended state. They are absolutely adapted to this way of life.
- Benthic. They live on the bottom of the reservoirs.
- Periphyton. They live on underwater rocks, overgrown with deep-sea objects.
- Neustonic. This species of algae floats in a semi-submerged state. One part is above the surface of the water, the other must be immersed in water.
Algae, living on land, are divided into two subgroups:
- Aerophyton. Algae, which overgrown land objects, piled objects, stumps.
- Algae growing on the surface of the soil.
In addition to the above species, there are those that live in salt water, snow or ice, and also live in limestone substratum.
How the algae reproduce
Let's deal with the main issue of the article. In nature, algae reproduce in three ways. Each of them has its own characteristics.
- Algae reproduce vegetatively. This is a method of reproduction in which an adult is divided in two or, for example, the kidney is separated from the mother's body. Then the newly formed cells are divided into two and four cells, from which later grows adult algae.
- Asexual reproduction. This is the kind in which the protoplast divides inside the algal cell, then exits to the outside and separates from the mother cell.
- Algae reproduce by spores, which are formed in special organs - sporangia.
- Sexual reproduction. It consists in the fusion of two cells, gametes, resulting in a zygote, which subsequently grows into a new individual or gives zoospores. And the zygotes of different algae after their formation behave differently. In some, they fall into a period of rest, which can last up to several months. And others sprout immediately into a new layer or thallus.
It is noteworthy that each species of algae reproduces in different ways. This question is studied by the school program. And often the students hear a question from the teacher: "How do the algae multiply? Describe the multiplication of algae." Reply to it simply, if you study the material in detail.
When algae reproduce asexually. Types of Asexual Reproduction
This is the simplest option. Sexlessly or vegetatively, algae reproduce mainly only in favorable conditions for them. This means, when the water in the reservoir has a certain temperature and conditions maximally contribute to asexual reproduction.
If in the water body or the environment there are sharp temperature changes, pollution or overcrowding by the inhabitants, in this case the algae proceed to sexual reproduction.
Asexual reproduction can be divided into several types:
- Algae reproduce vegetatively - there is a division of vegetative cells.
- Sporulation. Or, in another way, algae reproduce by means of special cells. These cells are called spores.
When algae reproduce asexually, there is only one parent, from which all existing genomes are inherited. But in the case of mutations, the genetic material can change significantly.
Often one organism can reproduce both asexual and vegetative.
Vegetative reproduction of algae
Vegetative reproduction is characteristic in most cases for brown algae.
With this method of reproduction, parts of the algae (thalloms) are separated from existing ones, without any changes, and the newly formed cells inherit a part of the maternal shell.
Vegetatively can multiply both unicellular and multicellular algae. And in unicellular cells the cell is divided into two, and in multicellular cells it occurs by layers or whole thalluses, colonies. In filamentous algae, the vegetative mode of reproduction occurs by dividing the strands into their individual fragments.
In this case, not all algae from the squad of colonial representatives can reproduce vegetatively, as well as in the unicellular along with the vegetative mode of reproduction, there may also exist a sexual path.
Brown algae, as already mentioned above, multiply in this way, with the help of special brood branches. Similarly, all kinds of sargasses reproduce in the Sargasso Sea.
Propagation by spores
In addition to vegetative reproduction, algae reproduce by spores. This is a definite subspecies of asexual reproduction.
Disputes are formed in special organs, so-called sporangia or zoosporangia. With dispersion, the spore begins to germinate and then a new adult independent individual is formed.
Movable disputes with flagella, capable of movement, are called zoospores.
The variant of asexual reproduction by spores can be considered on the example of such alga as ulotriks. In the favorable conditions for her life, from the existing mother thread, her fragments are separated, which contain controversies. They float in a free state, then, attaching themselves to an underwater object, they begin to actively share and form a new thread of algae. It should be noted that this species of alga can simultaneously multiply both asexually and sexually.
It is noticed that it is possible to stimulate the formation of spores in some species of algae, for this, an increase in carbon dioxide should occur in the habitat.
The function of asexual reproduction in this case is performed by individuals called sporophytes, that is, forming spores.
Sexual Path of Reproduction
In addition to the above methods, algae reproduce sexually. First of all, it is characterized by fertilization, that is, the fusion of two cells - gametes. After this, a zygote is formed, which subsequently becomes the ancestor of the new organism.
Algae have several ways of sexual reproduction:
- Isogamy - implies the merging of two identical in size and structure gametes.
- Heterogamy. This is the fusion of two gametes, in which one is more than the other. And the one that is bigger in size, as a rule, is female.
- Oogamy. With this method of reproduction, the inactive female cell merges with the mobile male gamete.
- Conjugation. By this concept is meant a type of reproduction, in which there is a union of two vegetative cells, devoid of flagella.
In primitive algae, the same individual is capable of both sexual and asexual reproduction. The most developed function is performed by individuals called gametophytes, that is, gametes forming.
Examples of algae reproduction
An example of vegetative propagation of algae can serve as fucus. On its main thallium, additional similar thallomes are formed, which subsequently give rise to a new organism.
Asexual reproduction, that is, division into two cells, can be observed in euglena.
Chlamydomonas is an algae, the reproduction of which occurs both sexually and asexually, with the help of spores (zoospores) having flagella.
Another example of sexual reproduction may be brown algae, such as kelp. In this species there are three ways of sexual reproduction, such as isogamy, gethorogamy, oogamy.
Chlorella is a microscopic green alga. Propagates exclusively asexually through the use of spores.
Red algae (criminals) reproduce in two ways, one of which is sexual. A distinctive feature of it is the formation of male gametes without flagella. At the same time, female gametes remain on algae, and male gametes are transferred to them with the help of a current.
The importance of algae in nature
Algae are the most numerous and important for the whole planet photosynthetic organisms. Their distribution is so wide that they can be met not only in the seas, oceans, rivers, lakes, but also in small reservoirs, including artificial ones, and even puddles. They can be observed in the form of small greenish spots on the surface of almost every reservoir. The importance of algae in nature is great.
In addition to the fact that they release a sufficiently large amount of oxygen, they serve as a habitat for many aquatic animals, participate in the formation of a fertile layer of soil. Many algae are used for food, and also serve as the main source in the extraction of special food components. They are also used for the preparation of various medications and cosmetics.
Algae are unique in their composition and mode of reproduction of organisms. They combine in themselves several types of reproduction, more precisely: sexual, asexual and vegetative. This practically makes them immortal. Moreover, this issue is very entertaining, because it's not for nothing that the biology teacher across the country is trying to get his pupils to answer the question: "How do the algae multiply? Describe the multiplication of algae."