Crustaceans are mainly marine animals, representatives of a number of species live in fresh waters and on land. Among crustaceans there are sessile, attached species, there are parasites,
Type Arthropods are the largest group of animals that inhabit our planet (more than 1 million species). They are found everywhere (in the ground-air environment, in all seas
The leech class has about 400 species. Leeches are descended from small-bristled annelids. The body length of leeches is from a few millimeters to 15 cm. Representatives of
From the polychaetal worms the small-bristle worms originated. The class Small-bristle worms include 4–5 thousand species. Habitat and meaning Most small-bristled worms live in the soil (for example,
The class of Polychaetes includes free-living annelids, in which numerous long bristles are collected in bundles and are located on the sides of each segment. There are about
Ringworms (Ringworms) type – includes animals whose bodies are made up of repeating segments, or rings. The annelids are the most progressive group of worms. These are the
Human roundworm (caused by a disease – ascariasis) The human roundworm parasitizes the human small intestine. Roundworms feed on the contents of the human intestine. The length of
Nematodes (from the Greek. Nemas – “thread”) are a class of Roundworms (about 20 thousand species). Free-living nematodes live on the bottom of seas and fresh water bodies,
All roundworms have a similar structure: an elongated body shape, a round cross-section (hence the name of the type), bilateral symmetry. The body of Roundworms consists of three
More than 25 thousand species belong to the type of Flatworms. Flatworms have bilateral (bilateral) symmetry. The body of Flatworms is formed from three layers of cells: ectoderm,
