BIO 102 | Study Mode

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Question 201
A
PAN (peroxy acyl nitrate)
B
ozone
C
nitrogen dioxide
D
carbon dioxide
Explanation
Photochemical smog is grey or yellow brown opaque smog having oxidising environment with little smoke. Photochemical smog contains secondary pollutants or photochemical oxidants. It was first reported over Loss Angels in 1940s. Photochemical smog is formed at high temperature over cities and towns due to still air, emission of nitrogen oxides and carbohydrates from automobile exhausts and solar energy.

Nitrogen dioxides split into nitric oxide and nascent oxygen. Nascent oxygen combines with molecular oxygen to form ozone. Ozone reacts with carbohydrates to form aldehydes and ketones. Nitrogen oxides, oxygen and ketones combine to form peroxy-acyl-nitrates (PAN). In areas with intense solar radiations, photoelectrical smog forms brown air.


Correct option: D
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Question 202
A
the food plants mature and die at the end of the rainy season
B
its population growth curve is of J-type
C
the population of its predators increases enormously
D
S-shaped or sigmoid growth of this insect.
Explanation
J-shape of growth pattern can be easily observed in algae blooms, some insects, annual plants and the lemmings of Tundra. In the beginning density of the population increases rapidly in compound interest fashion and then stops abruptly as the environmental resistance or other limiting factors become effective. These factors may be food, space, seasonal (frost, excessive rain etc.) or the termination of reproduction session.

Correct option: B
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Question 203
A
Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.
B
Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and for plant nutrition in soil
C
At present it is not possible to grow maize without chemical fertilizers
D
Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.
Explanation
Eutrophication in the phenomenon of nutrient enrichment of a water body that initially supports a dense growth of plants and animals. It is caused by runoff from fertilized fields, suburban lawns, detergent rich sewage; Eutrophication is caused by the increase in an ecosystem of chemical nutrients, typically compounds containing nitrogen and phosphorus.

It may occur on land or in water, although traditionally thought of as enrichment of Aquatic systems by addition of fertilizers into lakes, bays or other semi-enclosed waters terrestrial ecosystems are subject to similarly adverse impacts, eg cause of algal blooms.

Increased content of nitrates in soil frequently leads to undesirable changes in vegetation composition and many plant species are endangered as a result of eutrophication in terrestrial ecosystems, e.g., majority of orchid species in Europe.


Correct option: D
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Question 204
A
Lantana camara, water hyacinth
B
water hyacinth, Prosopis cinereria
C
nile perch, Ficus religiosa
D
Ficus religiosa, Lantana camara.
Explanation
As opposed to native species, which are indigenous and found naturally in an environment, animals and plant species introduced from other countries and which are not otherwise found local are termed exotic. These introduced or exotic species can adversely affect the ecosystem.

In India, large varieties of exotic animal and plant species have been introduced from other parts of the world through the ages. Some exotic plants have turned into weeds, multiplying fast and causing harm to the ecosystem, e.g. water hyacinth and Lantam camara. Water hyacinth was introduced in Indian waters to reduce pollution. It has clogged water bodies including wetlands at many places resulting in death of aquatic orgnisms.


Correct option: A

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