MP Board Class 10th Science imp questions Chapter 15 Our Environment

 

CHAPTER        15

Our Environment

 

Objective Questions

 

Multiple Choice Questions

 

1. Which of the following groups contain only biodegradable items!

(a) Grass, flowers and leather

 

(b) Grass, wood and plastic

 

(c) Fruit-peels, cake and lime-juice

 

(d) Cake, wood and grass.

 

2. Which of the following constitute a food-chain ?

(a) Grass, wheat and mango

 

(b) Grass, goat and human

 

(c) Goat, cow and elephant

 

(d) Grass, fish and goat.

 

3. Which of the following are environment friendly practices ?

 

(a) Carrying cloth bags while shopping

 

(b) Switching off unnecessary lights and fans

 

(c)Walking to school instead of getting your mother to drop you on her scooter

 

(d) All of the above,

 

4. Depletion of Ozone layer is mainly due to

 

(a) methane

 

(b) chlorofluorocarbons

 

(c) carbon dioxide

 

(d) nitrogen

 

5. Which of the following is an abiotic component ?

(a) plants

 

(b) soil

 

(c) animals

 

(d) micro-organisms.”

 

6. Flow of energy is an ecosystem is always

 

(a) unidirectional

 

(b) bidirectional

 

(c) multidirectional

 

(d) none of these

 

7. First order consumers are

 

(a) Carnivores

 

(b) Decomposers

 

(c) Omnivores

 

(d) Herbivores

 

8. Accumulation of non-biodegradable pesticides in the food chain in increasing

amount at each higher trophic level is known as-

 

(a) pollution

 

(b) accumulation

 

(c) biomagnification

 

(d) entrophication

 

9. In an ecosystem, the 10% of energy disposable for transfer from one trophic

level to next is in the form of –

 

(a) heat energy

 

(b) chemical energy

 

(c) mechanical energy

 

(d) light energy

 

10. What percentage of sunlight is captured by plants to convert it into food

energy?

 

(a) 1 %

 

(b) 10 %

 

(c) 50 %

 

(d) more than 50%.

 

Ans. 1. (a), (c), (d)), 2. (b), 3. (d), 4. (b), 5. (b), 6. (a), 7. (d), 8. (C), 9. (b), 10. (a).

 

I Fill in the Blanks

 

1. Polythene is an example of … waste

 

2. The various components of an ecosystem are

 

3. Abnormal increase of temperature in the environment due to the continuous

accumulation of gaseous pollutants is known as ………….

 

4. The ……….. layer protects against the UV radiations from the Sun.

 

5. The … make the energy from sunlight available to the rest of the ecosystem.

 

6. Ozone (03) is a molecule formed by ……….

atoms of oxygen

 

 

7. Changes in packaging have resulted in much of our waste becoming …………

 

8. The disposal of the waste we generate, is causing serious… problems

 

 

9. The energy transfer is… percent from one trophical level to another.

 

Ans. 1. non-biodegradable, 2. interdependent, 3. global warming, 4. Ozone,

5. producers, 6. three, 7. non biodegradable, 8. environmental, 9. 10.

 

* True/False

 

1. An aquarium is an incomplete artificial ecosystem.

 

2. Green plants capture about 10% of the energy of sunlight that falls on their leaves.

 

3. All green plants are producers

 

4. The flow of energy in a food chain is bidirectional,

 

5. The herbivores or the primary consumers come at second trophic level.

 

6. Human beings occupy the top level in any food chain.

 

Ans. 1. True, 2. False, 3. True, 4. False, 5. True, 6. True.

 

Match the Columns

 

Column ‘A’.                           Column ‘B’

 

1. Green plants. (a) Fourth trophic level

 

2. Polythene. (b) Photosynthesis

 

3. Lion. (c) Deadly poison

 

4. Ozone. (d) Non-biodegradable

 

5. Herbivores. (e) Fire extinguisher

 

6. CFC. (f) Second trophic level

 

 

Ans. 1. → (b), 2. — (d), 3. — (a), 4. → (c), 5. — (1), 6. — (e).

I

 

Answer in one Word/Sentence

 

1. How are consumers classified ?

Ans. Consumers are classified as herbivores, carnivores, omnivores and parasites.

 

2. What are micro-organisms like bacteria and fungi called in a food chain ?

Ans. Decomposers.

 

3. Name the carbon which is used in fire extinguishers and as a refrigerant?

Ans. Chlorofluorocarbon (CFC).

 

4. What the product of the action of UV radiation oxygen molecule ?

Ans. Ozone (0)

 

5. What are the substances that are broken down by biological processes called ?

Ans. Biodegradable.

 

6. Write the full name of CFC.

Ans. Chlorofluorocarbon.

 

Very Short Answer Type Questions

 

1. 1. Give examples of natural ecosystems.

Ans. Forests, ponds, lakes, sea, oceans, rivers etc. are examples of natural ecosystems.

 

2. 2. Give examples of artificial ecosystems.

Ans. Gardens, crop fields etc. are examples of artificial ecosystems.

 

3. 3. Name different abiotic factors that affect the ecosystem.

Ans. Temperature, water, rocks, soil, sunlight, precipitation and wind are abiotic

factors that affect the ecosystem.

 

4. 4. Define Detrivores.

Ans. Detrivores or Decomposers are the consumers that get energy from dead

digest organic matter and link consumers and primary producers.

organic matter (detritus), Example

prokaryotes and fungi. They secrete enzymes to

 

5. 5. What is the role of decomposers in the ecosystem?

Ans. The role of decomposers in the ecosystem – The decomposers decompose

organic substances in simple compounds which are used for nutrition by the producers.

Short Answer Type Questions

.

1. 1. Why are some substances biodegradable and some non-biodegradable ?

Ans. Substances are classified as biodegradable and non-biodegradable because

some substances can be decomposed by micro-organisms and some cannot

Susbtances that are broken down into simple soluble forms are called biodegradable

substances and the substances that are not decomposed by micro-organisms into harmless

substances are called non-biodegradable substances

 

2. 2. Give any two ways in which biodegradable substances would affect the

environment.

Ans. Biodegradable substances affect the environment in the following ways-

(1) The biodegradable substances such as plant parts, kitchen wastes, tree leaves

can be used as humus after composting. This enhances soil fertility

(2) The biodegrdable substances mainly contain carbon. These substances after

decomposition release that carbon back into the atmosphere.

 

3. 3. Give any two ways in which non-biodegradable substances would affect

the environment.

Ans. Non-biodegradable substances affect the environment in the following ways-

(1) By contaminating soil and water resources as they cannot be decomposed by

micro-organisms.

(2) These substances when accidentally eaten by stray animals can harm them and

even cause their death.

 

4. 4. What is ozone and how does it affect any ecosystem !

Ans. Ozone (03) is a molecule made up of three atoms of oxygen

Ozone (03) forms a layer in the upper atmosphere. It is essential for the life on

earth. It shields the surface of the earth from ultraviolet (UV) radiations from the sun.

These radiations are very harmful to organisms. It causes skin cancer and cataract in

humans. It is also harmful for crops.

 

5. 5. How can you help in reducing the problem of waste disposal ? Give any

two methods.

Ans. We can help in reducing the problem of waste disposal in the following ways–

(1) By separating biodegradable substances from non-biodegradable substances.

(2) By reducing, reusing and recycling non-biodegradable sustances,

 

6. 6. What will happen if we kill all the organisms at one trophic level ?

Ans. If we kill all the organisms of one trophic level, it will create an imbalance

in the ecosystem. e.g. in a food chain: Grass-Deer-Lion;

If we remove all lions, then population of deer will increase which will cause

overgrazing. This will

lead to deforestation. It may even lead to soil erosion causing further conversation of fertile land into barren desert

 

7. 7. What are the problems caused by the non-biodegradable wastes that we

generate ?

Ans.

The problems caused by non-biodegradable wastes are

(1) They cause bio-magnification

(2) They increase pollution

(3) They make environment dirty

(4) They kill useful micro-organisms.

 

8. 8. What is the role of decomposers in the environment ?

Ans. The role of decomposers in the environment is as follows-

(1) They clean the environment.

(2) They decompose biodegradable substances into useful substances

(3) They release nutrients into soil by decomposing dead and decaying matter,

thereby making the soil fertile.

(4) They maintain the nutrient pool by returning back the nutrients in the pool.

 

9. 9. If all the waste we generate is biodegradable, will this have no impact

on the environment.

Ans. If all the waste generated would be biodegradable, this will also create problem.

As the number of decomposers will be comparatively less therefore wastes would not be broken down into harmless simpler substances at a fast rate. Their decomposition would be quite slow. Hence, it would become a breeding ground for flies, causing spread of

diseases. It will also emit foul smell which will make life miserable.

 

10. 10. What is biological magnification ? Will the levels of this magnification

be different at different levels of the ecosystem?

Ans. Biological magnification is defined as the phenomena of accumulation or

increase in the concentration of several toxic substances at each trophic level.

The levels of biomagnification will be different at different trophic levels. It will

be maximum at last trophic level which is mostly of the top carnivores.

 

11. 11. What will happen if we kill all the organism in one trophic level?

Ans. If we kill all the organisms in one trophic level then the organisms of the higher

trophic level will die due to deficiency of nutrition and the number of organism in lower

them.

trophic level will increase very high due to which the struggle for life will start among

 

Long Answer Type / Analytical Questions

 

1. 1. What are trophic levels? Give an example of a food chain and state the

different trophic levels in it.

Ans. The various links or steps in a food chain at which the transfer of food and

energy takes place are called trophic levels.

 

The autotrophs or the producers are at the first trophic level. They fix up the solar energy

and make it available for heterotrophs or the consumers. The herbivores or the primary

consumers comprise the second trophic level

. Small carnivores or the secondary consumers

form the third, and larger carnivores or the tertiary consumers form the fourth trophic level.

In the above fig grass is the producer which is eaten by grasshopper known as

primary consumer. Then the grasshopper is eaten by shrew, secondary consumer, and

lastly, shrew is eaten by owl, tertiary consumer.

 

2. 2. Why is the damage to the ozone layer a cause of concern? What steps

are being taken to limit this damage ?

Ans. Ozone shields the surface of the earth from ultraviolet (UV) radiations from the

Sun. The damage to ozone layer is a cause of concem. UV radiation is highly harmful to

organisms. It causes skin cancer, ageing, skin darkening and comeal cataracts in human

beings. It can result in the death of many phytoplanktons that leads to global warming.

They also cause variation in global rainfall and ecological disturbances.

To limit the damage to the ozone layer, the release of chlorofluorocarbons (CFCs)

into the atmosphere must be reduced. The CFCs are used as a refrigerant and in fire

extinguishers. In 1987, the United Nations Environment Programme (UNEP) succeeded

in forging an agreement to freeze CFC production, at 1986 level. It is now mandatory for all the manufacturing companies to make CFC-free refrigerators throughout the world