8. ENVIRONMENTAL ISSUES
2020
SAY
1. One of the
effects of water pollution is algal bloom. (2)
(a)
Define algal
bloom.
(b)
Write two
effects of algal bloom in aquatic ecosystem.
ü Answer:
(a) Algal bloom is the presence of large amount of
nutrients in water resulting in excess growth of planktonic algae.
(b) i) imparts a distinct colour to the water bodies.
ii) cause deterioration of water quality and fish
mortality.
2. Write the uses
of scrubber and electrostatic precipitator. (2)
ü Answer:
Scrubber: Removes gases like sulphur dioxide from exhaust.
Electrostatic precipitator: Removes particulate matter present in the exhaust.
3. The
concentration of toxicants like DDT increase in successive trophic levels. (2)
(a)
Name this
phenomenon.
(b)
How does this
phenomenon affect the fish-eating birds in an aquatic food chain? (2)
ü Answer:
(a) Biomagnification.
(b) High concentrations of DDT disturb calcium
metabolism in birds that causes thinning of eggshell.
2020
MARCH
1. What are the
main consequences of Global warming? (2)
ü Answer:
Climatic changes, El Nino Effect, Melting of polar
ice etc.
2. Suggest any two
methods for the disposal of solid wastes. (2)
ü Answer:
1. Sanitary landfills, 2. Recycle, 3.
Incineration etc.
3. Ozone depletion
in stratosphere is a serious environmental issue. (3)
a. What is good ozone?
b. How do CFCs
degrade ozone molecules in stratosphere?
ü Answer:
(a) Good ozone: It is the ozone found in the stratosphere which
prevents harmful UV rays.
(b) When CFCs reach stratosphere, UV rays act on them
releasing Cl atoms. In presence of Cl (catalyst), ozone degrades to O2.
This causes ozone depletion
2019
SAY June
1. Expand CNG. (1)
ü Answer:
Compressed Natural Gas.
2. Water bodies
around us are getting polluted due to various reasons. Write any four
consequences of water pollution. (2)
ü Answer:
BOD of water increases.
Algal bloom.
Biomagnification.
Water borne diseases.
Eutrophication.
3. Observe the
figure showing the relative contribution of various greenhouse gases to global
warming. (3)
a. Identify A, B.
b. Write any two
consequences of global warming.
ü Answer:
(a) A= Methane B=
CO2
(b) Odd climatic change.
Melting of polar ice and rise in sea level.
2019
MARCH
1. The Government
of India has introduced the concept of ......................., so as to work
closely with the local communities for protecting and managing forests. (1)
ü Answer:
Joint Forest Management (JFM).
2. Which among the
following is not a greenhouse gas? (1)
a. N2O
b. Methane
c. Carbon dioxide
d. Ozone
ü Answer:
(d) Ozone
3. Deforestation
is a serious issue in the present scenario. Write any two major consequences of
deforestation. (2)
ü Answer:
Increase in atmospheric CO2 concentration causing
Global warming, Loss of habitat and biodiversity, Desertification.
4. Given below is
a flow chart showing the accumulation of DDT in different trophic levels: (2)
a. Name the
phenomenon.
b. How does it
affect bird population?
ü Answer:
(a) Biomagnification
(b) In birds, it
disturbs calcium metabolism resulting in thinning of egg shells.
2018
SAY June
1. Catalytic
converters are used in automobiles to control air pollution. Briefly comment on
its role. (2)
ü Answer:
Ÿ Unburnt hydrocarbons are converted into CO2 and
water.
Ÿ Carbon monoxide is changed to CO2.
2. Domestic sewage
and industrial effluents contain large amount of nutrients. What are the
probable effects of these nutrients on water bodies? (2)
ü Answer:
Ÿ Algal bloom.
Ÿ Eutrophication.
Ÿ Biomagnification.
Ÿ Deterioration of water quality.
2018
MARCH
1. Ozone acts as a
shield for absorbing ultraviolet radiations from the Sun. (2)
a.
Name the region
of atmosphere where Ozone is seen.
b.
Write the unit
used to measure ozone layer.
ü Answer:
(a) Stratosphere or Troposphere.
(b) Dobson (Db).
2. In 1990s, Delhi
ranked 4th among the most polluted cities of the world. What are the
parallel steps taken to reduce vehicular pollution? (2)
ü Answer:
Ÿ Use of lead-free petrol or diesel.
Ÿ Use of catalytic converters.
Ÿ Phasing out of old vehicles.
Ÿ Use of low-sulphur petrol and diesel.
Ÿ Use of compressed
natural gas (CNG) etc.
3. Increase in the
level of greenhouse gases leads to global warming. How can it be controlled?
(2)
ü Answer:
Ÿ Reduce the use of fossil fuel.
Ÿ Improve efficiency of energy usage.
Ÿ Reduce deforestation and plant trees.
Ÿ Slowing down the
growth of human population.