BIO 102 | Study Mode

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Question 191
A
< 30 ppm
B
< 3.0 ppm
C
< 10 ppm
D
< 100 ppm
Explanation
Strength of sewage of degree of water pollution is measured in terms of BOD (Biological oxygen demand) value. BOD may be defined as, number of milligrams of 02 required for decomposition of one litre of waste or water by decomposing micro-organisms (bacteria). According to central pollution control board, limit of BOD prescribed is 30 ppm (mg/d) for 3 days at 27 C.

Correct option: A
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Question 192
A
fresh weight
B
dry weight
C
number of individuals
D
rate of energy flow
Explanation
Ecological pyramids represents the tropic structure and tropic function of an ecosystem. In an ecological pyramid, the first tropic level forms the base and successive tropic levels the tiers which make up the apex. Ecological pyramids may be of three general types pyramid of number, pyramid of biomass and pyramid of energy.

Pyramid of biomass i.e. the living weight of the organisms of the food chain present at any time in an ecosystem forms the pyramids of biomass. The pyramid of biomass indicates the decrease or the gradual reduction in biomass at each trophic level from base to apex. Fresh weight is not used in ecological pyramids.


Correct option: A
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Question 193
A
mutualism between two species
B
active cooperation between two species
C
two different parasites on the same host
D
sharing of one or more resources between the two species (2006)
Explanation
Niche/ecological niche is specific part of habitat occupied by individuals of a species which is circumsribed by its range of tolerance, range of movement, microclimate, type of food and its availability, shelter, type of predator, and timing of activity. A habitat has several ecological niches and supports a number of species.

An ecological niche is used by a single species. Two or more species cannot use the same niche despite having a mutualistic association. Organisms or populations in competition have a niche overlap of a limited resource for which they compete.

Both owl and cat feed on shrews and mice. They occupy the same niche because of being ecological equivalents though their habitats are different.


Correct option: D
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Question 194
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 195
A
SE < PE < S < DE
B
PE < S < SE < DE
C
S < DE < PE < SE
D
SE < S < PE < DE.
Explanation
The BOD of the given pollutants in ascending order is PE < S < SE < DE

Correct option: B
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Question 196
A
NOx
B
SPM
C
CO
D
SO2.
Explanation
SPM is suspended particulate matter which is less than 10 p.m remaining in air for more than one day to several weeks. It includes aerosol, dust, mist, smoke, soot etc.

Correct option: B
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Question 197
A
population
B
landscape
C
ecosystem
D
biotic community.
Explanation
Population has several characteristics or attributes which are a function of the whole group and not of individual. Age distribution is one of them that is the number or the percentage of individuals in a population in different age groups. This is represented geometrically in the form of age pyramid.

Correct option: A
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Question 198
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 199
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 200
A
a bi-modal distribution
B
a T-shaped curve
C
a skewed curve
D
a normal distribution.
Explanation
It the mean and the median pertaining to a certain character of a population are of the same value a normal distribution is most likely to occur.

Correct option: D

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