Our environment Worksheet-11

Our environment Worksheet-11


  1. Describe any four modes of disposal of waste.


  1. How are depletion of ozone layer caused and what is its effect on our environment?


  1. What are decomposers? Write the role of decomposers in the environment.


  1. What is biological magnification? if the concentration of DDT were 0.2 ppm in water of a lake, what would be its likely concentration in fish in the following food chain? Plankton → Fish → Fish-eating birds.


  1. Write the food chain operation in a fresh water pond. Mention the food habit of each trophic level in this food chain.


  1. How do food chains get shortened? How does their shortening affect the biosphere?


  1. Give an example of a food chain consisting of four organisms at different trophic levels. Give the scientific term used to indicate the first and third trophic level.


  1. What would happen if all the decomposers were eliminated from the Earth? Explain.


  1. Describe how ozone present in the atmosphere is important for sustaining life on earth.


  1. List two reasons to show that the existence of decomposers is essential in biosphere.


  1. Mention the difference between food habits of organisms belonging to the first and third trophic level. Give one example of each of them.


  1. Draw schematic diagrams of a food chain and a food web. (use only the names of the organisms).


  1. Explain how will it affect the environment if the decomposers are removed from the ecosystem.


  1. Which food chains are advantageous in terms of energy? Support your answer giving one example.


  1. State (a) two causes and (b) two effects of the depletion of ozone layer in the atmosphere.


  1. Why we say energy flow in the biosphere is unidirectional.


  1. The use of pesticide DDT is discouraged since this chemical is found in human body. How does this chemical enter our body?


  1. The following are the organisms found in the grassland. Construct a food chain with four trophic levels: Seed eating bird, grasshopper, lion, green plants, rat, deer, frog, snake.


  1. What is the difference between the food habits of organisms belonging to second and fourth trophic levels. Give one example of organisms belonging to each of these two trophic levels.


  1. With the help of food chain explain how biological magnification of harmful chemicals can occur.