Our Environment-5 PDF

and animals. This is one of the ways in which they enter the food chain. As these chemicals are not degradable, these get accumulated progressively at each trophic level. As human beings occupy the top level in any food chain, the maximum c...

and animals. This is one of the ways in which they enter the food chain. As these chemicals are not degradable, these get accumulated progressively at each trophic level. As human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our bodies. This phenomenon is known as biological magnification. This is the reason why our food grains such as wheat and rice, vegetables and fruits, and even meat, contain varying amounts of pesticide residues. They cannot always be removed by washing or other means. Activity 13.3 n Newspaper reports about pesticide levels in ready-made food items are often seen these days and some states have banned these products. Debate in groups the need for such bans. n What do you think would be the source of pesticides in these food items? Could pesticides get into our bodies from this source through other food products too? n Discuss what methods could be applied to reduce our intake of pesticides. Q U E S T I O N S ? 1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it. 2. What is the role of decomposers in the ecosystem? 1 3. 2 HOW DO OUR ACTIVITIES AFFECT THE ENVIRONMENT? We are an integral part of the environment. Changes in the environment affect us and our activities change the environment around us. We have already seen in Class IX how our activities pollute the environment. In this chapter, we shall be looking at two of the environmental problems in detail, that is, depletion of the ozone layer and waste disposal. 13.2.1 Ozone Layer and How it is Getting Depleted Ozone (O3) is a molecule formed by three atoms of oxygen. While O2, which we normally refer to as oxygen, is essential for all aerobic forms of life. Ozone, is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation 212 Science 2024-25