As a result, many animal species have become extinct or they have adjusted to the new conditions of life. Many water ecco-systems have dried out and in the process many species have dissapeared. With the development of cities, many birds vanished, while the ones that remained had to adjust to the conditions. Also, some insects, like the cockrouches, became present in the homes and cellars.

The most present and harmful chemical substances for the living creatures on Earth are the insecticides - DDT and Polychlorinated Biphenyls (PCBs), heavy metals - from which very dangerous are mercury, cadmium and lead. These hazardous substances are more present in the soil, in the organs of the plants, and through the plants in the animals, as well as in the water ecco-systems. The hazardous substances remain in the organisms of animals blocking the operation of some systems and causing changes to their metabolism.