Insects, insects (Insecta) - a cluster of arthropods. The largest group of animals. Estimated number of insect species is around 1 million. These are animals of all terrestrial environments, or re-adapted to the aquatic environment. Were the first animals to acquire the ability to active flight. Insect body sizes ranging from 0.25 mm to 350 mm. In Poland, the most numerous orders of insects are represented, butterflies, beetles, hymenopterans and dipterans. Insects are of great importance in nature, among them are both beneficial insects and pests, parasites and commensally. Science that deals with insects is entomology.
Due to the small amount of fossil evidence (mainly ...view middle of the document...
It consists of prothorax, and outer-body inter-body. On each segment there is a pair of legs, and outer-body inter-body and is also present a pair of wings (winged insects).
Respiratory system of insects is composed of a system of branched tubes called trachea. The air enters the system through trachea spiracles - small holes in the surface of the body. Number and location of the spiracles are different in different species. Maximum number of spiracles is 20 (eight pairs of torso spiracles and 2 pairs of abdomen). Then the air goes trachea branching system that can be traced to all parts of the body of the animal. Tracheae are chitinous sheath, providing sufficient flexibility walls. Oxygen is supplied directly to the cells. The exchange of air from trachea is by diffusion through the gas and cramping, thorax and abdomen. Inside the body tracheae end blindly, microscopic soft, fluid-filled trachoma. Gas exchange occurs by diffusion between the liquid filling trachoma’s, and cells of the body. Insect larvae living in water gills breathe. They are thin walled plaques on the abdomen, leading to appropriate tracheas. In insects, so there is a direct supply of oxygen to every cell of the body without the cardiovascular system. This ensures high efficiency of gas exchange, necessary for flight.
The importance of insects in nature
Insects on land meets water, air, underground, the plants and animals, in their feces and cadavers, and in cold areas, hot and mild. So unusual spread of insects, combined with their enormous fertility, and thus the size, plays in human life and its economy a huge positive role, but often negative. Indeed, the majority of insects pollinate commercial crops, purify the land of the dead, rotting organic debris, improve soil structure, produce some raw materials such as honey and wax, but also destroy the forests and field crops and garden, damaging and...