BIO 102 | Study Mode

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Question 91
A
Cyperus rotundus
B
Eichhornia crassipes
C
Typha latifolia
D
Trapa bispinosa.
Explanation
Eichhornia crassipes or water hyacinth (American water plant) has become the most serious weed in many tropical, warm and temperate freshwater habitats worldwide including India. It has the highest growth rate of any saltwater, freshwater or terrestrial vascular macrophvte and can be labelled as an ecosystem engineer or an invasive habitat modifier.

In slow-moving to still water bodies it is especially problematic as it forms dense monospecific mats that lower dissolved oxygen levels in the water, alter river hydrology and increase organic sediment. These mats displace native aquatic plant and animal communities; drastically alter the ecosystem and puts native habitats and wildlife at risk. Furthermore, water hyacinth may interfere with the use of a water-body for cultural, social or commercial purposes causing substantial economic hardship and putting livelihoods at risk.


Correct option: B
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Question 92
A
ecology
B
ecosystem
C
phytogeography
D
ethology.
Explanation
Ecology is the branch of science which deals it the study of inter relationship between organisms their environment. The scope of ecology is very vast as it treats the organisms at the level of population, community and ecosystem. Ethology is the study of evolution any significant behaviour of people in their natural surroundings. Phytogeography is the branch of biogeography that is concerned with the geographic distribution of plant species.

Correct option: A
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Question 93
A
colony
B
genus
C
community
D
species.
Explanation
The sum total of the populations of the same kind of organisms constitute species. A species is a group of individuals of same kind of phenotypic characters and can interbreed.

Correct option: D
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Question 94
A
clay
B
loam
C
sandy
D
gravel.
Explanation
Soil best suited for plant growth is loam. Loam soils have sand, silt and clay in a specific proportion. The soil contains 20% clay, 40% silt and 40% sand. They have good nutritive status aeration and hydration.

Correct option: B
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Question 95
A
colony
B
mutualism
C
commensalism
D
ammensalism.
Explanation
Mutualism is a type of association where both the partners are benefitted. This is permanent and t obligatory association involving a physiological inter- dependence e.g. in lichens.

Correct option: B
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Question 96
A
species in an area
B
individuals in a community
C
individuals in a tropic-level
D
subspecies in a community.
Explanation
Pyramid of number is an ecological pyramid which employs the number of individuals per unit area at various trophic levels sequence wise with producers at the base and various consumers at successively higher levels. Pyramid of number assumes different shapes in different ecosystems, individuals in a trophic level.

The pyramid of number in pond ecosystem is also upright. In forest ecosystem the pyramid of number is inter mediate. Here the number of primary consumers is more than producers as well as top consumers. In parasitic food chain the pyramid of number is inverted.


Correct option: C
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Question 97
A
irregular
B
inverted
C
upright
D
spindle shaped.
Explanation
Pyramid of number in a pond ecosystem is always upright, showing the number of individual organisms at each level. In a pond, the producers, which are mainly phytoplanktons, 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: C
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Question 98
A
sea gull
B
phytoplankton
C
eel
D
crab.
Explanation
Biomagnifications is the increase in concentration of a compound in the tissue of organism as the compound passes up a food chain usually as a result of food intake. This results from the accumulation of the compound at each trophic level prior to its consumption by organisms at the next trophic level. Most chlorinated hydrocarbon like DDT shows biomagnifications. Level of concentration of compound increases in higher trophic level as shown in the following chain. Water > phytoplanktons > zooplanktons > insects > fish > large fish

Higher the trophic level higher will be the accumulation of organic compound. Hence sea gull is likely to have the highest level of DDT deposition in its body.


Correct option: A
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Question 99
A
carbon dioxide
B
chlorofluoro carbon
C
Freon
D
methane.
Explanation
Due to excessive combustion activity, the content of CO2 in the atmosphere has been steadily rising. CO2 is opaque to infra-red waves. Therefore, it allows the sunlight to fall on earth but checks the loss of heat during night. As carbon dioxide accumulates in the atmosphere it absorbs more and more of the reflected infrared radiation.

This could cause an increase in temperature referred to as the green house effect. Methane also causes green house effect but comparatively lesser than CO2. Chlorofluorocarbons and Freon cause depletion of ozone layers. Depletion of ozone layer leads to increase in incidence of skin cancer due to increased penetration of suns harmful rays.


Correct option: A
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Question 100
A
phytoplankton
B
zooplankton
C
benthos
D
plankton.
Explanation
Trophic level is a step or division of food chain which is characterized by the method of obtaining its food. The two fundamental trophic levels are producers and consumers. Producers belong to the first trophic level. In a lake the producers are mainly some rooted or floating plants and phytoplanktons.

Primary consumers form the second trophic level. They feed on living plants or plant parts. The primary consumers are zooplanktons.


Correct option: B

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