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.



Q 1.

What will happen if we kill all the organisms in one trophic level? [Delhi]

Q 2.

What is pollution?

Q 3.

(a) Define decomposers. Name one decomposer.
(b) What is the role of decomposers in the ecosystem ?

Q 4.

Name two predators of snakes in a food web operating in a forest ecosystem.

Q 5.

(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

Q 6.

How are most of the solid wastes in urban areas disposed of ?

Q 7.

Write the common food chain of a pond ecosystem.

Q 8.

Why is ozone layer getting depleted at the higher levels of the atmosphere? [Delhi (C)]

Q 9.

Name the process in which a harmful chemical enters the food chain and gets concentrated at each trophic level.

Q 10.

‘If we excessively use pesticides to protect the crops from diseases, then it may cause long-term damage to mankind’. Justify this statement.

Q 11.

How is the increase in demand for energy affecting our environment adversely?

Q 12.

Why are some substances non- biodegradable? [Foreign]

Q 13.

What are planktons ?

Q 14.

Name the process by which the volume of solid wastes can be reduced.

Q 15.

Explain how, harmful ultraviolet radiations of sunlight are prevented from reaching the earth’s surface.

Q 16.

Give a method for the disposal of household wastes such as left-over food, fruit and vegetable peels, and leaves of potted plants.

Q 17.

What are the advantages of cloth bags over plastic bags during shopping?

Q 18.

Why are green plants called ‘producers’? [All India]

Q 19.

Why did United Nations act to control the production of chlorofluorocarbons (CFCs) used in refrigerators? [Delhi]

Q 20.

Why is it necessary to conserve our environment? [All India]

Q 21.

What are the various steps of food chain called ?

Q 22.

If a harmful chemical enters a food chain comprising cat, mice and plants, which one of these organisms is likely to have the maximum concentration of the harmful chemical in its body ?

Q 23.

How can the wastes such as paper, plastic and metal objects be disposed of ?

Q 24.

We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

Q 25.

Give an example to illustrate that indiscriminate use of pesticides may result-in the degradation of the environment. [All India]

Q 26.

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]

Q 27.

State whether the following statements are true or false :State whether the following statements are true or false :
(a) In biology, human beings are called producers.
(b) Secondary consumers and tertiary consumers, both are carnivores.

Q 28.

Which category of organisms forms the starting point of a food chain ?

Q 29.

Where does all the energy in living organisms originate from ?

Q 30.

What is the important function of presence of ozone in earth’s atmosphere? [Delhi]

Q 31.

Which of the following belong to the same trophic level ?
Tree ; Frog ; Snake ; Grass ; Lizard

Q 32.

(a) Describe an activity to show that while paper is biodegradable but plastic (say, polythene) is non-
(b) Explain why, some materials are biodegradable but some are non-biodegradable.

Q 33.

What would happen if the ozone layer in the atmosphere completely disappears ?

Q 34.

Explain the phenomenon of “biological magnification” How does it affect organisms belonging to different trophic levels particularly the tertiary consumers? [Delhi]

Q 35.

Write the name and formula of a molecule made up of three atoms of oxygen. [All India]

Q 36.

Which one term in the following includes the others ?
air, flora, fauna, environment, water, sunlight, soil

Q 37.

Write the harmful effects of ozone depletion.

Q 38.

Suggest any four activities in daily life which are eco-friendly.

Q 39.

“Damage to the ozone layer is a cause for concern.” Justify this statement. Suggest any two steps to limit this damage. ‘ [Delhi]

Q 40.

Define ozone layer?

Q 41.

Why is it necessary to manage our garbage?

Q 42.

Fill in the following blanks with suitable words : Fill in the following blanks with suitable words :
(a) Decomposer organisms are……………. in their action.
(b) In nature, all green plants are……………. whereas animals are consumers.
(c) A series of organisms, each of which feeds on the next organism, the beginning of which is a green plant, is called a…………….
(d) The science that deals with the inter-relationships of living things with one another and their environment is called …………….
(e) Plastic is a……………. material whereas paper is a……………. material.

Q 43.

What percentage of energy available at the producer level is transferred at successive trophic levels in a food chain ?

Q 44.

Name the group of chemical compounds which damages the ozone layer.

Q 45.

Which disease is caused in human beings due to depletion of ozone layer in the atmosphere? [Foreign]

Q 46.

Define ‘trophic level’. [Delhi]

Q 47.

Name the phenomenon in which non-biodegradable chemicals get accumulated progressively at each trophic level of a food chain.

Q 48.

Name two natural ecosystems and two artificial ecosystems.

Q 49.

A food chain represents a unidirectional flow of X. What is X ?

Q 50.

What is the difference between the food habits of organisms belonging to the first and the third trophic levels ? Give one example each of the organisms belonging to these two trophic levels.