In this post, you will get all intext and end exercise questions solutions prepared by experienced teachers. These are useful for RBSE and other state boards also.
Chapter 15 -Our Environment
Answers of Questions on Page 212
Q.1 What are trophic levels? Give an example of a food chain
and state the different trophic levels in it.
Answer
Trophic
levels- ‘Trophs’ means organisms. In a
food chain there are many levels in which energy (food) flows in one direction.
These levels are called trophic levels.
In above food chain grass is first trophic level, deer
second level and lion is third trophic level.
Q.2 What is the role of decomposers in the ecosystem?
Answer
(i) Decomposers act as scavengers or cleaning agents i the environment.
(ii) They release nutrients back to the environment by decomposing dead remains of plant and animals
Answers of Questions on Page 214
Q.1 Why are some substances biodegradable and some are
non-biodegradable?
Answer
(a).Biodegradable
substances:- The substances which can be broken down to non-poisonous
and simple substances by the action of microorganism or biological process in
nature, are called biodegradable substances such cattle dung, vegetable stuffs,
tea leaves, paper wood ,leather etc.
(b).Non-biodegradable substances:-
the substances which cannot be broken down to non-poisonous and simpler
substances by the action of microorganism or biological processes in nature
,are called non-biodegradable substances such as pesticides, plastics, polythene
bags, glass, metals etc.
Q.2 Give any two ways in which biodegradable substances would
affect the environment.
Answer
Biodegradable substances are decomposed into simple substances by biological processes. These substances would affect the environment in following manner-
(i) Poisonous and foul smelling gases like methane are formed and these are responsible for greenhouse effect.
(ii)Dead and decaying substances make water unsafe and cause water pollution
Q.3 Give any two ways in which non-biodegradable substances
would affect the environment.
Answer
(i) Non – biodegradable substances in the form of fine particles pollute water, air and soil.
(ii) They increase bio magnification in food chain and end up human beings.
Answers of Questions on Page 216
Q.1 What is ozone and how does it affect any ecosystem?
Answer
Ozone
(O3) is a molecule formed by three atoms of oxygen. Ozone forms layer at a
certain height of atmosphere. It protects the living beings from the harmful
ultraviolet rays emitted by the sun.
Q.2 How can you help in reducing the problem of
waste-disposal? Give any two methods.
Answer
We can
help in reducing the problem of waste-disposal in the following ways:
(i) Biodegradable
waste should be used to obtain bio-gas and manure.
(ii) The wastes
from industries should be treated at the plant-site before disposal.
Answers of End Exercise Questions
Q.1 Which of the following groups contains 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
Groups
containing biodegradable items only (a), (c) and (d).
Q.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 (b) grass, goat and human
Q.3 Which of the following are environment friendly
practices?
Answer
(a) carrying cloth-bags to put purchase 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 the above
Answer (d) all the above
Q.4 What will happen if we kill all the organisms in one
trophic level?
Answer
If we kill all the organisms in one trophic level, there will be the following effects.
(i) The population of organisms in the previous trophic level will increase.
(ii) It will cause an ecological imbalance.
(iii) The organisms in next trophic level will not be able to get the food, so they will migrate to some other ecosystem or die.
Q.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
Yes,
the impact of removing all the organisms in a trophic level will be different
for different trophic levels. For example if all carnivores are killed then
initially the population of herbivores would increase. They will eat all
vegetation therefore an imbalance in
ecosystem will occur later of sooner.
No, it not possible that the organisms of any
trophic level can be removed without causing any damage to the ecosystem. All
producers and consumers form a food web and any harm to this web will affect
all living beings.
Q.6 What is biological magnification? Will the levels of this
magnification be different at different levels of the ecosystem?
Answer
Continuous
progress in harmful non-biodegradable substances in progressive trophic level
of food chain is called biological magnification.
Yes, the levels of magnification will be
different at different levels of the ecosystem.
Q.7 What are the problems caused by the non-biodegradable
wastes that we generate?
Answer
Non-biodegradable
wastes cause following problems –
i. Very large space is required for disposal.
ii. Many harmful substances like DDT, CFC etc
are released that enters in food chain.
iii. Its
volume cannot be reduced.
Q.8 If all the waste we generate is biodegradable, will this
have no impact on the environment?
Answer
If all
the waste we generate is biodegradable, it will cause no pollution, but still
it is not true to say that there will be no impact on the environment, because excess
of any waste is not good for the environment. Decomposition of these substances
produce foul smell and forms breeding place for germs and pests.
Q.9 Why is damage to the ozone layer a cause of concern? What
steps are being taken to limit this damage?
Answer
Ozone layer
prevents the harmful ultraviolet radiation from the sun to enter into the
atmosphere and to reach the earth-surface. Exposure to ultraviolet radiation
may cause fatal disease skin cancer and change in genetic-material DNA,
increase in average temperature of the earth. That’s why, damage to the ozone
layer is a cause of great concern.
The United
Nations Environment Programme (UNEP) succeeded in forging an agreement to
freeze CFC production at 1986 level.
No comments:
Post a Comment