Habitat of roundworms. Characteristics of roundworms

In total, there are more than 20 thousand species of these creatures. But in the school they study only one of them. Depending on their biological characteristics, they can live in different conditions. Soil, fresh water and sea - this is the habitat of roundworms. Also there are separate representatives, leading a parasitic way of life.

general characteristics

These are non-parted animals. The primary body cavity is filled with liquid. They are capable of active movement. Food for free living species are bacteria, algae and unicellular. They, in turn, eat fish fry, small crustaceans.

In the school most often considered such representatives of parasitic forms, as pinworms and ascarids. They are able to live inside their master, whose role is played by animals and even by humans. In humans, they lead to a deterioration of well-being, whereas birds, fish and insects sometimes experience cases of mass death. Individual species parasitize on fungi and plants.

Structure

The structure of roundworms assumes the presence of a cylindrical or spindle-shaped body. The cuticle covers it from the outside. The primary cavity is located under the skin-muscular sac.

The intake of food is through the mouth in the throat. From here she goes to the digestive tube, which consists of the anterior, middle and posterior intestines. It ends with the anal opening. Modified skin glands are part of the excretory system.

These creatures are dioecious. They lack systems such as the respiratory and circulatory systems.

Universal capabilities in terms of adaptation to environmental conditions can be explained by the presence of a dense outer layer (cuticle).

The habitat of roundworms in some cases includes moss. They are able to penetrate into various parts of plants: stalks, roots, tubers and leaves.

The distribution of these creatures is wide.

Differences from other species

The structure of roundworms differs somewhat from the anatomical features of their flat counterparts. On a cross-section it is visible, that the body has the form of a circle. It is symmetrical and elongated. The skin-muscular sac serves for it as a kind of wall. Cuticle, located on the outside, serves as a skeleton.

The adaptive mechanisms of parasitic worms are such that this layer does not collapse under the influence of the digestive juices of the host. He is also not afraid in a number of cases of chemical attack.

Next is the hypodermis. This skin consists of protoplasm. Under it are longitudinal muscles. They are separated by a kind of ribbons.

Muscle cells consist of two parts:

• Reducible;
• The plasma.

Representatives of roundworms have a mouth opening located in the anterior part of the body. There is no lining of epithelium in it. In addition to internal organs, there is also a cavity fluid. In some species, it may have toxic properties. The high pressure created by it provides reliable support for the muscular sac. It is also important in terms of metabolism.

Characteristics of the roundworm includes many important features. It is noteworthy that the organs of hematopoiesis and respiration in these creatures are absent. Air exchange is carried out through the outer covers. Parasitic forms can do without oxygen at all.

Reproduction

In most cases, representatives of roundworms are dioecious organisms. Thanks to this, their descendants are distinguished by their genetic diversity. For individual individuals, so-called sexual dimorphism is characteristic, that is, males do not look like females in appearance.

Development is carried out indirectly. The larval stage takes place. A change of host is not required. Type of impregnation - internal.

Sense organs and nervous system

Nervous system

Refers to the ladder type. It is otherwise called "orthogon". A special nerve ring surrounds the pharynx. There are 6 nerve trunks that branch back and forth. Among them, the most developed are the dorsal and the ventral. They are connected by means of jumpers.

Sense organs

In the presence of organs of touch and chemical senses, that is, worms are capable of catching smells. Eyes in their most primitive form are present in free-living representatives.

There are several classes, but the most numerous are the nematodes. If your child goes to grade 7, roundworms will be studied by him in the biology program. Traditional representatives, considered in school:

• Ascarids;
• Pinworms.

Ascaris. Character traits

The first type of worms leads a parasitic life and lives in the small intestine. Helminth reaches a length of up to 40 centimeters. The female is capable to postpone over 200 thousand eggs per day. Their development without oxygen is impossible. They are covered with protective shells, located in several layers. Inside there are larvae. Their viability is sometimes preserved up to 10 years.

If there is insufficient hygiene, infestation occurs, that is, infection. In this case, eggs enter the oral cavity from the surface of unwashed vegetables and fruits, as well as hands. All this is indicated in the subject "biology". Round worms do not need a change of hosts for development.

After entering the intestine, the larvae exit the egg. They easily break through the mucous membrane and penetrate into the bloodstream. After that they fall into the heart and further into the lungs. From here they pass into the bronchi and the trachea. In this period, a person coughs.

The movement of the larvae can last up to 12 days. All this time they grow and change the shell several times. After re-entering the small intestine, they continue to grow for three months. At the end of this period, helminths become adults. Each of them lives about 1 year.

These species of roundworms are dangerous because they cause poisoning in the body. Intoxication occurs under the influence of poisonous substances, which are the result of the vital activity of parasites. In addition, after getting into the organs and cavities of the ascarid, it causes mechanical damage to them.

Pinworm. Characteristics of the round worm

Another representative of the class is an oyster. Usually she lives in the large intestine. Characterized by small dimensions. Females are larger than males and reach 12 mm. Infection is carried out in the same way as in the case with ascarid.

The main reason for invasion is inadequate hygiene. If you wash your hands badly after visiting the toilet, these kinds of roundworms can easily penetrate your body. Particular care should be taken during your stay in public places.

If the eggs of the pinworm fall under the fingernails, they can easily get into the mouth. After 6 hours, larvae will appear from them. Once in the small intestine, they will move to its final sections. After 14 days, the parasites will multiply. Each individual lives for not more than a month. But in the event that a repeated self-infection occurs, the disease can be delayed. Sometimes flies and cockroaches also carry helminth eggs.

Value in human life and nature in general

Type is represented not only by parasites, but also by predators. Plants are the habitat of roundworms of the following species:

• Onion;
• Beet;
• Wheat;
• Potato.

Parasites exert a depressing effect on the growth of crops. As a result, their yield is significantly reduced.

Among these creatures you can find detritophages. The source of food for them are organic remains, humus. Such worms take a direct part in the formation of soil.

Where do nematodes occur?

Find them is not as difficult as it seems. If you suddenly find yourself in the countryside, go to the nearest river or lake. Pay attention to the sand that is on the shore. These creatures are often found in it. It also makes sense to look at the growths on trees and old snags. This is also the habitat of roundworms.

Some species live in algae. Thus, they can be found almost everywhere. Each of them has its own power source. Despite this, they do not have to starve. Someone is digging in the sand and looking for bacteria, others are strenuously pulling out the juices from the plants.

In the forest, too, live round worms. To find them, you should come here in rainy weather. If desired, you can simply take a piece of moss or lichen and dip it into the water. Surely you will find representatives of this type in it.

But how do they survive if there is not enough moisture in the soil or vegetation? They come to the aid of natural protection. As soon as the moss dries, the nematodes run into anabiosis. At the same time they remain alive. Such a state is necessary in order to successfully wait out the best times. The same can be said for parasites in the expectation of a new master. They will begin to show activity only when conditions are acceptable for life.