BIO 102 | Study Mode

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Question 61
A
mutualism/symbiosis
B
commensalism
C
amensalism
D
both A and B.
Explanation
Mutualism is an association between individuals of two species, both of which are benefitted but cannot live separately under natural conditions e.g. instances of mutualism exist between animals and plants and also in between plants e.g. lichens. Ammensalism is an interaction in which one species causes harm to another spices with its toxic secretion often without gaining any benefit from the interaction. Commensalism is the relationship between individuals of two species of which one is benefitted and the other is almost unaffected i.e.; neither benefitted nor harmed.

Correct option: A
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Question 62
A
primary consumers are least dependent upon producers
B
primary consumers out-number producers
C
producers are more than primary consumers
D
secondary consumers are the largest and most powerful.
Explanation
An ecosystem may be defined as a structural and functional unit of the biosphere comprising living organisms and their non-living environment that interact by means of food chains and chemical cycles resulting in energy flow, biotic diversity and material cycling to form a stable, self supporting system.

The organisms in an ecosystem are classified into 3 main categories-producers, consumers and decomposers. The consumers utilize materials and energy stored by the producers. Decomposers obtain their food molecules from the organic materials of dead producers and consumers. In a true ecosystem, producers are more than consumers (herbivores and carnivores).


Correct option: C
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Question 63
A
free energy
B
carbon
C
nitrogen
D
potassium.
Explanation
The behaviour of energy in ecosystem can be termed energy flow due to unidirectional flow of energy, Flow of energy is only in one direction i.e., from solar radiation > producers > heribivorous > carnivores. This energy cannot pass in the reverse direction. There is decrease in the content and flow of energy with rise j in tropic level.

Correct option: A
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Question 64
A
infra-red rays reaching earth
B
moisture layer in atmosphere
C
increase in temperature due to increase in carbon dioxide concentration of atmosphere
D
ozone layer of atmosphere.
Explanation
The mean global temperature rise by 2 6c and the concentration of carbon dioxide increases in the troposphere upto 600 ppm. Hence, the surface of the earth becomes warm which causes global warming. The phenomenon is similar to that of green house in which the glass enclosed atmosphere gets heated up due to its insulation from the rest of the environment. Hence, global warming is also known as green house effect and the gases responsible for it are called green house gases e.g CH4, CO2 etc.

Correct option: C
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Question 65
A
conversion of sterile soil into fertile one
B
aeration of soil
C
erosion of soil
D
protection against loss.
Explanation
Soil conservation is to conserve fertile soil from the losses like heavy rainfall, drainage, high wind, flood, draught etc. Soil is the top cover of the earth in which plants can grow. The rotation of crops, contour ploughing and use of proper fertilizers help in maintaining the fertility of soil. Plantation of trees, controlled grazing of grasslands, reforestation, prevention of forests fires will protect the erosion of top soil. The regulation of water resources to prevent flood will help not only in soil conservation but also supply an adequate water supply in the period of drought.

Correct option: D
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Question 66
A
symbiosis
B
parasitism
C
commenalism
D
protocooperation.
Explanation
Algae and fungi in a lichen show symbiotic relationship. Fungi give support to the algae, give protection and help in absorption of water while algae provide food to fungi which is achlorophyllous. No one is harmed but both are benefitted by each other.

Correct option: A
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Question 67
A
sulphur dioxide
B
carbon monoxide
C
methane
D
fluorocarbon.
Explanation
Aerosols are chlorofluoro-hydrocarbon compounds released into air with force in the form of vapour. Main source of aerosols is the emission of jet planes, where fluorocarbons are used. These chlorofluorocarbons deplete the ozone layer in the higher atmosphere. These CFCs have produced a hole in the ozone layer.

Correct option: D
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Question 68
A
methyl isocyanate
B
potassium isothiocyanate
C
sodium isothiocyanate
D
ethyl isothiocyante.
Explanation
In Bhopal, the killer gas methyl isocyanate (MIC) was leaked into air from a chemical plant (Union Carbide) killing more than 2,000 people, many of the people are still suffering from various diseases and defects of eye.

Correct option: A
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Question 69
A
soil erosion
B
soil fertility
C
land slides
D
rainfall.
Explanation
Deforestation is the conversion of forested areas to non-forest land use such as arable land, pasture, urban use, logged area, or wasteland. Generally, the removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity. Deforestation results from removal of trees without sufficient reforestation, and results in declines in habitat and biodiversity, wood for fuel and industrial use, and quality of life. Due to deforestation, transpiration will be decreased, air temperature will be increased and water content will be decreased hence rainfall decreases.

Correct option: D
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Question 70
A
always inverted
B
always upright
C
both A and B
D
spindle-shaped.
Explanation
Pyramid of number in a grassland/tree ecosystem is always upright. It shows the number of individual organisms at each level. In grassland, the producers, which are mainly grasses, are always maximum in number. This number then shows a decrease towards apex, primary consumers are lesser in number than the grasses; the secondary consumers are lesser in number than the primary consumers. Finally, the top consumers are least in number. Thus, the pyramid becomes upright.

Correct option: B

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