Define ozone layer?
Ozone is a form of oxygen. Each ozone molecule is made of three oxygen atoms, so its chemical formula is O3. But unlike oxygen, ozone is a poisonous gas, and an increase in its concentration at ground level is harmful. But in the stratosphere, where ozone exists naturally, it blocks out the sun’s ultraviolet rays and is a lifesaver.
(a) Define decomposers. Name one decomposer.
(b) What is the role of decomposers in the ecosystem ?
(a) What is meant by non-biodegradable waste materials ? Give two examples of non-biodegradable wastes.
(b) Which of the following materials are biodegradable ?Animal bones, Iron nails, Plastic mugs, Leather belts, Silver foil
Explain how, harmful ultraviolet radiations of sunlight are prevented from reaching the earth’s surface.
Give an example to illustrate that indiscriminate use of pesticides may result-in the degradation of the environment. [All India]
Fill in the following blanks with suitable words :Fill in the following blanks with suitable words :
(a) Ultraviolet rays can cause skin…………………
(b) Pesticides enter the food chain at the…………………. level
(c) Grass →…………….→Human
(d) Lettuce →…………….→ Fox
(e) Plants→ Antelope→ …………….
Why did United Nations act to control the production of chlorofluorocarbons (CFCs) used in refrigerators? [Delhi]
What name has been given to those organisms which break down the complex organic compounds present in dead animals and plants ?
Which organisms belong to third and fourth trophic levels in the food chain comprising the following ?
Rats, Plants, Hawk, Snakes
Can the organisms of any trophic level be removed without causing any damage to the ecosystem ? Will the impact of removing all the organisms in a trophic level be different for different trophic levels ?
(a) What is meant by ‘environment’ ?
(b) What type of substances are the major pollutants of the environment ? Name two such substances.
(c) Name the organisms whose uncontrolled activities are damaging the environment.
(d) Explain why, it is better to use paper bags than plastic bags.
Name the process in which a harmful chemical enters the food chain and gets concentrated at each trophic level.
‘If we excessively use pesticides to protect the crops from diseases, then it may cause long-term damage to mankind’. Justify this statement.
Give a method for the disposal of household wastes such as left-over food, fruit and vegetable peels, and leaves of potted plants.
(a) With the help of a flow diagram, describe how energy from the sun flows through various trophic levels.
(b) Explain why, the flow of energy in the ecosystem is said to be unidirectional.
Name the wastes which are generated in your house daily. What measures would you take for their disposal?
Why is ozone layer getting depleted at the higher levels of the atmosphere? [Delhi (C)]
Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment. [Delhi]
State two problems caused by the non- biodegradable waste that we generate in our daily life. [All India (C)]
Explain the phenomenon of “biological magnification” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers? [Delhi]
Select two non-biodegradable substances from the following waste generated in a kitchen: spoilt food, paper bags, milk bags, vegetable peels, tin cans, used tea leaves. [Delhi]