Our Environment Class 10 Important Questions Science Chapter 15

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Our Environment Class 10 Important Questions with Answers Science Chapter 15

Our Environment Class 10 Important Questions Very Short Answer Type

Question 1.
What will happen if we kill all the organisms in one trophic level? (CBSE 2011-2012)
Answer:
If we kill all the organisms in one trophic level, the following effects will take place:

The population of organisms in previous trophic level will increase.
The organisms in next trophic level will not be able to get the food, so they will migrate to some other ecosystem or die.
It will cause an ecological imbalance in the food chain.

Question 2.
Why did United Nations act to control the production of chlorofluorocarbons (CFCs) used in refrigerators? (CBSE 2011-2012)
Answer:
CFCs deplete the ozone layer around the earth, hence their production is controlled by United Nations.

Question 3.
Which compounds are responsible for the depletion of ozone layer? (CBSE 2011-2012)
Answer:
The compounds responsible for the depletion of ozone layer are chlorofluorocarbons (CFCs).

Question 4.
Define “trophic level”. (CBSE 2011-2012)
Answer:
Trophic level is the position that an organism occupies in a food chain, where transfer of food or energy takes place.

Question 5.
What are the various steps in a food chain called? (CBSE 2011-2012)
Answer:
The various steps in a food chain are called trophic levels.

Question 6.
Give an example to illustrate that indiscriminate use of pesticides may result in the degradation of the environment. (CBSE 2011-2012)
Answer:
The pesticides used in crop field are washed down into the water bodies. From water bodies these are absorbed by aquatic plants and animals of a food chain and thereby degrades the environment.

Question 7.
What is the important function of presence of ozone in earth’s atmosphere? (CBSE 2011-2012)
Answer:
The important function of presence of ozone in earth’s atmoshphere is that it shields the surface of the earth from ultraviolet (UV) radiations of the sun.

Question 8.
Why is it necessary to conserve our environment? (CBSE 2011-2012)
Answer:
It is necessary to conserve our environment to prevent depletion of natural resources and environmental damage, thereby sustaining life.

Question 9.
What is meant by a biodegradable waste? (CBSE 2011-2012)
Answer:
Biodegradable wastes are those substances which are broken down into simpler, harmless substances in nature in due course of time by the biological processes such as action of microorganisms like certain bacteria.

Examples: Urine and faecal matter, sewage, agricultural residue, paper, wood, cloth and cattle dung.

Question 10.
What is the role of decomposers in the ecosystem? (CBSE 2011-2012)
Answer:
Role of decomposers in the environment:

They return the nutrients to the nutrient pool.
They help in completing bio-geochemical cycles, thus they maintain the balance in the ecosystem.

Question 11.
What step is being taken to limit the damage to the ozone layer? (CBSE 2011-2012)
Answer:

Judicious use of aerosol spray propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
Control over large scale nuclear explosions and limited use of supersonic planes.

Question 12.
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. (CBSE 2011-2012)
Answer:
Milk bags and tin cans.

Question 13.
What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere? (CBSE 2011-2012)
Answer:
When high energy ultraviolet radiations act on oxygen, ozone is produced:

Our Environment Class 10 Important Questions Science Chapter 15, 1

Question 14.
In a food chain, 10,000 joules of energy is available to the producer. How much energy will be available to the secondary consumer to transfer it to the tertiary consumer? (CBSE 2011-2012)
Answer:
10 J will be available to the secondary consumer to transfer to the tertiary consumer.

Question 15.
List two man-made ecosystems. (CBSE 2011-2012)
Answer:
Garden and pond are man-made ecosystems.

Question 16.
Name the phenomenon in which non-biodegradable chemicals get accumulated progressively at each trophic level of a food chain. (CBSE 2011-2012)
Answer:
Biological magnification.

Question 17.
Consider the following food chain which occurs in a forest: Grass → Deer → Lion. If 10000 J of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion? (CBSE 2011-2012)
Answer:
10 J energy would be available to deer to transfer to lion.

Question 18.
Which of the following belong to the first trophic level of a food chain? Grass, Grasshopper, Plants, Rat, Tiger. (CBSE 2011-2012)
Answer:
Grass and plants belong to the first trophic level of a food chain.

Question 19.
What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules? (A.I. 2015)
Answer:
1000 J.

Question 20.
What is the function of ozone in the upper atmosphere? (Delhi 2015)
Answer:
It shields the surface of the earth from ultraviolet rays from the Sun.

Question 21.
List two natural ecosystems. (Delhi 2016)
Answer:
Natural ecosystem-Forest/Lake/Pond/River.

Question 22.
We often use the word, environment. What does it mean? (Foreign 2016)
Answer:
It is the physical, chemical and biological conditions of a particular area or the whole world, as the case may be.

Question 23.
The depletion of ozone layer is a cause of concern. Why? (AI 2016)
Answer:
Ultraviolet rays from the sun penetrate down the earth and cause health hazards, e.g., skin cancer in human beings.

Our Environment Class 10 Important Questions Short Answer Type

Question 1.
Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment. (CBSE 2008)
Answer:
Bacteria and fungi are called decomposers as they break down the dead remains and waste of organisms. They convert the organic complex substance into simple inorganic substances that go into the soil and are used up by plants.
Two advantages of decomposers:

They return the components back to nature and creates balance in the environment.
They act as cleansing agents of the atmosphere.

Question 2.
(a) Distinguish between producers and decomposers.
(b) Classify the following as producers and decomposers.
Green plants, bacteria, fungi, blue-green algae. (CBSE 2008 F)
Answer:
(a)
Producers:

Producers convert simple inorganic substances into complex organic substances
Producers are autotrophs that can prepare food with CO2, FLO, chlorophyll and sunlight e.g., green plants.

Decomposers:

Decomposers break the complex organic substances into simple inorganic substances.
Decomposers decompose the complex substances present in the plants, animals e.g., bacteria, fungi.

(b) Producers – Green plants, blue-green algae.
Decomposers – bacteria, fungi.

Question 3.
Name any two abiotic components of an environment. (CBSE 2009)
Answer:

Water
air.

Question 4.
What are the two main components of our environment? (CBSE 2009)
Answer:

Biotic (living components) → Plants, animals
Abiotic (non-living components) → Water, air

Question 5.
Which compounds are responsible for the depletion of ozone layer? (AI 2009)
Answer:
Chlorofluorocarbons (CFC)

Question 6.
Why are green plants called producers? (AI 2009)
Answer:
Green plants can prepare complex organic matter as food from simple inorganic substances like CO₂, H₂O in presence of sunlight and chlorophyll. They produce food and hence called producers.

Question 7.
Which disease is caused in human beings due to depletion of ozone layer in the atmosphere? (Foreign 2009)
Answer:
Skin cancer, cataract.

Question 8.
Why are forests considered “biodiversity hot spots”? List two ways in which an individual can contribute effectively to the management of forests and wildlife. (Delhi 2015)
Answer:
Forests are considered ‘biodiversity hot spots’ because a large number of life forms such as bacteria, fungi, fern, nematodes, insects, birds, reptiles, mammals, gymnosperms and angiosperms are found there. A region with large biodiversity of endangered species, many of them being highly endemic and such regions being subjected to large scale destruction are designated as “Flot spots” by ecologists.

Two ways in which an individual can contribute to the management of forests and wildlife:

Not allowing cutting of trees
To promote/make people aware about the importance of forests and wildlife,
Not using wildlife products.

Question 9.
What is ozone? How and where is it formed in the atmosphere? Explain how does it affect an ecosystem. (Foreign 2015)
Answer:
Ozone is a molecule containing three atoms of oxygen (O₃), a highly poisonous gas present in the upper layers of the atmosphere.

Formation of ozone: The UV radiations split some molecular oxygen (O₂) apart into free oxygen atoms (O + O). These atoms then combine with molecular oxygen to form ozone.
Effect: Ozone layer shields the surface of the earth from the damaging UV radiations of the sun.

Question 10.
The following organisms form a food chain. Which of these will have the highest concentration of non biodegradable chemicals? Name the phenomenon associated with it.
Insects, Hawk, Grass, Snake, Frog (Foreign 2015)
Answer:
Hawk will have the highest concentration of non-biodegradable chemicals.
The phenomenon associated with it is biomagnification.

Question 11.
Give reason to justify the following: (Delhi 2016)
(a) The existence of decomposers is essential in a biosphere.
(b) Flow of energy in a food chain is unidirection.
Answer:
(a) The existence of decomposers is essential in a biosphere because they break down complex organic substances into simple inorganic substances that can be absorbed by the plants. Thus, decomposers

replenish the soil naturally.
helps in removing the biodegradable waste.

(b) In a food chain the energy moves progressively through the various trophic levels. It is no longer available to the previous level (autotrophs) and the energy captured by the autotrophs does not go back to the solar input. Hence, the flow of energy is unidirectional.

Question 12.
“Burning of fossil fuels results in global warming”. Give reasons to justify this statement. (AI 2016)
Answer:
Burning of fossil fuels produces greenhouse gases (CO, CO₂, water vapour, oxides of nitrogen, sulphur). High concentration of CO₂ causes global warming.

Our Environment Class 10 Important Questions Long Answer Type

Question 1.
“Damage to the ozone layer is a cause of concern”. Justify this statement and suggest any two steps to limit this damage. (CBSE 2008)
Answer:
Ozone is a molecule of oxygen with 3 atoms i.e., 03. It is formed due to sunlight at higher levels with higher wavelength.

O₂ + (O) → O₃
Ozone is found in stratosphere shielding the earth by protecting it and by not allowing UV rays to reach the earth.

If these rays will reach the earth, then many harmful diseases are caused like skin cancer, cataract. It also affects the growth of plants and vegetation.
Two steps to limit the damage of this layer are:

Do not use aerosols, or any products which will release CFC (chlorofluorocarbon) in the atmosphere.
Ban on use of CFC as refrigerant and in fire extinguishers.

Question 2.
Distinguish between biodegradable and non-biodegradable substances. List two effects of each of them on our environment. (CBSE 2008)
Answer:
Biodegradable substance:

Substances can be decomposed by micro-organisms
Do not get accumulated in environment.
Do not cause any pollution

Non-biodegradable substance:

Substances cannot be decomposed by micro-organisms.
It gets accumulated in environment.
It causes pollution.

Two effects on environment:
Biodegradable substance:

Releases foul smell while decomposing in surrounding areas.
It acts as a breeding ground for insects.

Non-biodegradable substance:

It gets accumulated causing water and soil pollution and causes biological magnification.
It disturbs the ecosystem by interfering in the food chain and killing many animals.

Question 3.
The activities of man had adverse effects on all forms of living organisms in the biosphere. Unlimited exploitation of nature by man disturbed the delicate ecological balance between the living and non-living components of the biosphere. The unfavourable conditions created by man himself threatened the survival not only of himself but also of the entire living organisms on the mother earth. One of your classmates is an active member of ‘Eco club’ of your school which is creating environmental awareness amongst the school students, spreading the same in the society and also working hard for preventing environmental degradation of the surroundings. (AI 2016)
Answer:
Two reasons for the conservation of the environment:
(a)

To save air, water and soil from pollution.
To maintain ecological balance in nature.

(b) Green dustbins – green dustbins are used for biodegradable waste, and blue dustbins for non biodegradable waste for proper disposal of waste without wasting time and energy in segregating the biodegradable and non-biodegradable wastes.