Page 198 - Class 10th Biology Chapter Our Environment NCERT Book Questions and Answers
| Chapter - Our Environment |
|---|
Page 257
Question 1:
Why are some substances biodegradable and some non-biodegradable?
Answer 1:
Some substances which are degraded and broken down into simpler substances
by the microorganisms, are called biodegradable substances.
For example: Cotton, wood, paper, wool, etc.
Substance (mainly man-made) that do not degraded or broken down into simpler
substances by the action of enzymes secreted by microorganisms are called non-
biodegradable substances.
For example: Plastic, polythene, DDT, etc.
Question 2:
Give any two ways in which biodegradable substances would affect the
environment.
Answer 2:
During decomposition process of biodegradable substances foul smell and
some harmful gases are released which make problem for the nearby living
person.
During decomposition it provide a breeding ground for mosquitoes, insects
and microbes responsible for diseases like cholera, diarrhoea, etc.
Question 3:
Give any two ways in which non-biodegradable substances would affect the
environment.
Answer 3:
Chemicals like BHC and DDT induce carcinoma (muscle cancer) and
growth of tumours.
Handling of waste materials may cause skin, respiratory and intestinal
infections.
Non-biodegradable substances do not decompose easily so it produces land
and water pollution.
Page 261
Question 1:
What are trophic levels? Give an example of a food chain and state the different
trophic levels in it.
Answer 1:
The various steps in food chain at which transfer of food energy takes place are
called trophic levels.
Example: Food chain operating in a grassland.
Grass → Insects → Frogs → Snakes
1. Grass → 1
st trophic level
2. Insects → 2
nd trophic level
3. Frogs → 3
rd trophic level
4. Birds → 4
th
trophic level
Question 2:
What is the role of decomposers in the ecosystem?
Answer 2:
Decomposers are microorganisms that act on dead and decaying bodies of
producers and consumers and break them into simple inorganic compounds. They
absorb some of the substances and release the rest into the environment to be
recycled and to be used in future by producers. Thus, decomposers have a key
role in the cycling of material in the biosphere and provide the raw materials to
the producers. So in this way they make the soil fertile.
Page 264
Question 1:
What is ozone and how does it affect any ecosystem?
Answer 1:
Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone, is a deadly
poison. However, at the higher levels of the atmosphere, ozone performs an
essential function. It shields the surface of the earth from ultraviolet (UV)
radiation from the Sun.
This radiation is highly damaging to organisms, for example, it is known to cause
skin cancer, cataract and damage the immune system in human beings. It also
destroys plants and reduces photosynthesis process.
Question 2:
How can you help in reducing the problem of waste disposal? Give any two
methods.
Answer 2:
By minimising the use of disposal items and promoting the use of recycled
articles.
Separating biodegradable and non-biodegradable waste before dumping
them.
Recycling the non-biodegradable waste material.
Exercises
Question 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
Answer 1:
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Question 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
Answer 2:
(b) Grass, goat and human
Question 3:
Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in 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
Answer 3:
(d) All of the above
Question 4:
What will happen if we kill all the organisms in one trophic level?
Answer 4:
If we kill all the organisms in one trophic level, the transfer of food energy to the
next trophic level will stop. This will cause a break in the food chain resulting in
ecosystem imbalance. As a result, the organisms of the higher trophic level will
also die, while the individuals of the lower trophic level will exhibit enormous
growth in their population. Both the conditions will result in ecological upset.
Question 5:
Will the impact of removing all the organisms in a trophic level be different for
different trophic levels? Can the organisms of any trophic level be removed
without causing any damage to the ecosystem?
Answer 5:
Yes, the impact of removing all organisms in a trophic level will be different for
different trophic levels. If all the producers are killed, it will cause death or
migration of the primary consumers in the ecosystem. In the absence of
producers, subsequent level of consumers will also be affected. But if primary
consumers are removed, organisms of higher trophic level will die, while those
of lower level (producers) show exponential growth much beyond the carrying
capacity of the environment. Removal of the organisms in a trophic level will
upset the whole ecosystem as all categories of organisms are linked through food
chain. The survival of organisms of one trophic level depends on the existence of
the members of other trophic level.
Question 6:
What is biological magnification? Will the levels of this magnification be
different at different levels of the ecosystem?
Answer 6:
Progressive increase in the concentration of non-biodegradable substances in a
food chain is called biological magnification. The level of these harmful
substances will go on increasing from one trophic level to the next. When certain
harmful substances enter the food chain at the level of primary producers,-they
get concentrated many times at each subsequent trophic level.
Question 7:
What are the problems caused by the non-biodegradable wastes that we generate?
Answer 7:
Non-biodegradable wastes cannot be broken-down into simpler substances. Their
volume keeps on increasing creating the problem of their safe disposal. Some of
the non-biodegradable wastes like heavy metals and pesticides enter into the food
chain and increases in the upper trophic levels. Non-biodegradable wastes reduce
the soil fertility by changing the natural pH balance.
Question 8:
If all the waste we generate is biodegradable, will this have no impact on the
environment?
Answer 8:
Biodegradable wastes are decomposed by microorganisms into simpler
substances themselves and provide raw materials for producers, but they also
have adverse effects on the environment:
Slow decomposition of biodegradable waste will result in the release of
foul smell and harmful gases. When inhaled by human beings, they may
cause irritation, nausea, giddiness, etc.
Decomposing waste provides breeding ground for some harmful
organisms. Abundance of harmful microorganisms may cause diseases in
animals, plants and human beings.
Increase in the number of microorganisms in aquatic medium will- cause
oxygen deficiency in waterbodies.
Question 9:
Why is damage to the ozone layer a cause for concern? What steps are being taken
to limit this damage?
Answer 9:
Ozone layer is a protective shield around the earth. It prevents harmful ultraviolet
radiation of the sun from reaching the earth. Air pollutants, like
chlorofluorocarbons (CFCs), are causing depletion of ozone layer. This is
allowing greater amount of UV radiation to reach the earth. UV radiation can
upset the ecosystem by affecting photosynthesis in plants, destroying planktons
and decomposers. In human beings, UV radiation may cause skin cancer, cataract
of eyes and damage to immune system. Several developed as well as developing
nations of the world have agreed to sign and obey the directions of TINEP (United
Nations Environment Programme) to freeze the production of CFCs or to 1imit
their production to some extent.
