Earthworm – the representative like Annelidas. Its long extended business consists of separate segments – the rings divided by ring banners than and the name of a look is caused. Thanks to such building it can freely move both in dense soil, and on the surface of the soil.
Instruction
1. The body of an earthworm is extended in length at 10-16 cm of Ono roundish on cross section, but longitudinally divided by ring banners into 100-180 chlenik. On them elastic bristles which the worm clings to roughnesses of the soil during the movement are located.
2. In the afternoon worms are in the soil and lay in it the courses. Soft they easily proburavlivat the front end of a body: in the beginning that becomes thin, and the worm pushes it between earth lumps forward, then, being thickened, the front end moves apart the soil, and the worm tightens already back part of a body. In the dense earth the worms can eat to themselves the courses, passing it through a digestive tract. At night they come to the surface of the soil and leave behind characteristic earth small groups.
3. Skin of an earthworm damp to the touch as it is covered with the slime facilitating movement of a worm in the soil. The oxygen necessary for breath, can also get only through moist skin. Under it there is a skin and muscular bag – the ring (cross) muscles which grew together with skin under which the layer of longitudinal muscles lies. The first do a body of an animal long and thin, the second – thickened or shortened. The coordinated alternate work of these muscles also provides the movement of a worm.
4. Under a skin and muscular bag it is possible to see the body cavity filled with liquid. In it internals of an animal are located. Unlike roundworms, at rain a body cavity not continuous, but chlenisty, divided by cross walls.
5. On the front end of a body there is a mouth. He swallows the decaying vegetable remains and fallen leaves which the worm eats together with the earth by means of a brawny throat. Further the digestive tract proceeds a gullet, a craw, a stomach, a gut and an anus. Through the last on the back end of a body the undigested remains of food together with the earth are thrown out outside.
6. The blood system of an earthworm has two main vessels: back and belly. On the first blood moves behind beforehand, on belly – in front back. In each chlenik they are connected by ring vessels. Due to reduction of muscular walls several thick ring vessels have a blood current.
7. The main vessels branch on thinner, and those are on the smallest capillaries. Nutrients from intestines and oxygen from skin come to them. Such blood system at which blood moves only on vessels and does not mix up with band liquid is called closed.