(ii) By burning of fossil fuels: Fossil fuels like coal, petroleum
and natural gas are rich source of carbon. On burning,
they release carbon in the form of carbon dioxide back
into the atmosphere.
- (a) Metals used in catalytic converters that help in keeping
the environment clean are platinum- palladium and
rhodium.
(b) Lichens are very sensitive to pollution, especially
caused by SO 2. Air polluted with SO 2 and acid rain,
destroy lichen population. Hence, lichens are regarded
as pollution indicators.
- (a) Differences between grazing food chain and detritus
food chain are as follows:
Grazing food chain Detritus food chain
(i) The food chain begins
with producers at the
first trophic level.
The food chain begins
with detritivores and
decomposers at the first
trophic level.
(ii) Energy for the food
chain comes from sun.
Energy for the food chain
comes from organic
remains or detritus.
(b) In ecological context, herbivores are considered similar
to predators because they feed on plants and their
products for their food requirements just like predators
feed on prey for their food needs.
- (a) Mammals from colder climates generally have shorter
ears and limbs to minimise heat loss. This is called as
the Allen’s rule.
(b) Photochemical smog is composed of secondary air
pollutants. It is formed by interaction of hydrocarbons
with nitrogen oxides. The products are ozone,
peroxyacyl nitrate (PAN), aldehydes and phenols.
(c) Diapause is a stage of suspended development, which
is exhibited by many zooplankton species in lakes and
ponds, under unfavourable conditions.
(d) Biodiversity hotspots are the regions which are
characterised by very high levels of species richness
and high degree of endemism. India has three hotspots
- Indo-Burma (North-East India), Eastern Himalayas,
and Western Ghats.
- (a) CNG (Compressed natural gas) is a better fuel than
petrol or diesel because it is (i) cheaper (ii) burns more
efficiently, (iii) does not produce much pollution,
(iv) cannot be siphoned off by thieves and (v) cannot be
adulterated like petrol and diesel. The major problem of
CNG is laying down of pipes to ensure uninterrupted
supply of CNG to CNG pumps or distribution points.
(b) Catalytic converters, having expensive metals namely
platinum-palladium and rhodium as the catalysts,
are fitted into automobiles for reducing emission of
poisonous gases. As the exhaust passes through the
catalytic converter, unburnt hydrocarbons are converted
into carbon dioxide and water, and carbon monoxide
and nitric oxide are changed to carbon dioxide and
nitrogen gas, respectively. Vehicles equipped with
catalytic converter should use unleaded petrol because
lead in the petrol inactivates the catalyst.
(c) Cars seen with Bharat stage IV stickers implies that the
vehicles are complied with the new auto fuel policy to
reduce vehicular pollution. Bharat stage IV norms are
implemented in 13 mega cities of India.
(d) Rekha shows alertness, awareness, responsibility and
firmness in tackling a problem. She had the knowledge
about vehicular norms which she applied in a correct
situation.
- (a) The nutrient enrichment of water bodies near industrial
area is due to passage of industrial effluents, sewage,
etc. This cause dense growth of planktonic algae, that
results in colouration of water called algal bloom.
Excessive growth of it cut off light for submerged
plants which kills the latter and causes organic loading.
This leads to decreased oxygen level which eventually
chokes the water body.
(b) Organic waste and other types of waste material
should not be dumped into the pond. Domestic wastes
with organic nutrients must be treated before passing
into it.
(c) Eichhornia crassipes is also called as “Terror of
Bengal” because it is an exotic shrub which strongly
competes with the native species and has also
eliminated many of them. It has beautiful flowers but
it sometimes chokes ponds, lakes, wetlands and rivers
resulting in imbalance of ecosystem of water bodies
and causes death of many aquatic species of India.
It also increases biochemical oxygen demand of the
water body.
OR
Refer to answer 74, page 370, MTG CBSE Champion.
- Refer to answer 114, page 350, MTG CBSE Champion.
OR
(a) Refer to answers 84 and 82 (a), page 409, MTG CBSE
Champion.
(b) Refer to answer 86 (b), page 409, MTG CBSE
Champion.
- Refer to answer 82, page 371, MTG CBSE Champion.
OR
Refer to answer 65 (a), page 368, MTG CBSE Champion.