Biology Archives

111. With reference to Neem tree, consider the following statements : 1.

With reference to Neem tree, consider the following statements :

1. Neem oil can be used as a pesticide to control the proliferation of some species of insects and mites.
2. Neem seeds are used in the manufacture of biofuels and hospital detergents.
3. Neem oil has applications in pharmaceutical industry.

Which of the statements given above is/are correct?

[amp_mcq option1=”1 and 2 only” option2=”3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in

UPSC IAS – 2014

The Neem tree (Azadirachta indica) is renowned for its various uses, particularly derived from its seeds and leaves.
Statement 1 is correct: Neem oil contains compounds like azadirachtin which act as natural insecticides, repellent, and growth regulators for a wide range of insects and mites. It is widely used as a biopesticide.
Statement 2 is correct: Neem seeds contain oil that can be used for making soap (a component in detergents) and has potential as a non-edible oil source for biodiesel production (biofuels). While ‘hospital detergents’ is specific, the use in soap/detergents and potential for biofuels from seeds is established.
Statement 3 is correct: Neem and its derivatives have a long history of use in traditional medicine (Ayurveda, Unani). Modern research has explored its potential in pharmaceuticals for its antifungal, antibacterial, antiviral, anti-inflammatory, and other properties.

– Neem products, especially neem oil from seeds, have insecticidal properties.
– Neem oil is used in soap/detergent making and explored for biofuel production.
– Neem has medicinal properties and applications in the pharmaceutical industry.

The numerous applications of Neem tree have led to it being called “Sarva Rog Nivarni” (curer of all ailments) or “village pharmacy” in India. Its eco-friendly pesticidal properties are particularly valued in organic farming.

112. Lichens, which are capable of initiating ecological succession even on

Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of

[amp_mcq option1=”algae and bacteria” option2=”algae and fungi” option3=”bacteria and fungi” option4=”fungi and mosses” correct=”option2″]

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UPSC IAS – 2014

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Lichens are a symbiotic association between a fungus and a photosynthetic organism, typically an alga or a cyanobacterium.

In this symbiosis, the fungus (mycobiont) provides structure, protection from drying, and absorbs water and minerals from the environment. The alga or cyanobacterium (photobiont) provides food through photosynthesis, producing carbohydrates that the fungus utilizes. This mutualistic relationship allows lichens to colonize harsh environments, including bare rock, where neither organism could easily survive alone.

Lichens are pioneers in primary ecological succession on bare rock. They secrete acids that help weather the rock, breaking it down and creating initial soil particles, which allows other plants to eventually grow. They are also excellent indicators of air quality because they are very sensitive to atmospheric pollution.

113. If you walk through countryside, you are likely to see some birds stal

If you walk through countryside, you are likely to see some birds stalking alongside the cattle to seize the insects disturbed by their movement through grasses. Which of the following is/are such bird/birds?

1. Painted Stork
2. Common Myna
3. Black-necked Crane

Select the correct answer using the code given below.

[amp_mcq option1=”1 and 2″ option2=”2 only” option3=”2 and 3″ option4=”3 only” correct=”option2″]

This question was previously asked in

UPSC IAS – 2014

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The behaviour of stalking alongside cattle to catch insects disturbed by their movement is characteristic of the Common Myna.

Common Mynas (Acridotheres tristis) are frequently observed foraging for insects in grasslands, often following grazing animals like cattle, sheep, or even lawnmowers, taking advantage of insects stirred up from the vegetation. This is a form of commensalism, where the bird benefits, and the cattle are largely unaffected.

Painted Storks (Mycteria leucocephala) are wading birds that feed primarily on fish and other aquatic prey in wetlands. Black-necked Cranes (Grus nigricollis) are large birds that feed on roots, tubers, insects, and small vertebrates, often foraging in wetlands or agricultural fields, but are not typically known for actively following cattle for insects in the same way as mynas.

114. Consider the following : 1. Bats 2. Bears 3. Rodents The phe

Consider the following :

1. Bats
2. Bears
3. Rodents

The phenomenon of hibernation can be observed in which of the above kinds of animals?

[amp_mcq option1=”1 and 2 only” option2=”2 only” option3=”1, 2 and 3″ option4=”Hibernation cannot be observed in any of the above” correct=”option3″]

This question was previously asked in

UPSC IAS – 2014

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Hibernation is a state of inactivity and metabolic depression in endotherms. It is observed in various animal groups, including mammals like bats, bears, and many rodents.

Bats enter deep hibernation. Many rodents, such as groundhogs, ground squirrels, and hamsters, are well-known hibernators. While the hibernation of bears is sometimes debated in terms of its physiological depth compared to smaller mammals, they do enter a state of reduced metabolic activity, body temperature, and heart rate for extended periods during winter.

True hibernation involves a significant drop in body temperature (close to ambient), drastic slowing of metabolic rate, and infrequent arousals. Some animals, like bears, enter a less profound state sometimes called ‘winter sleep’ or torpor, where the body temperature drop is less severe and arousals might be more frequent, but it still serves the purpose of conserving energy during periods of food scarcity and cold.

115. Which of the following phenomena might have influenced the evolution o

Which of the following phenomena might have influenced the evolution of organisms?

1. Continental drift
2. Glacial cycles

Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”2 only” option3=”Both 1 and 2″ option4=”Neither 1 nor 2″ correct=”option3″]

This question was previously asked in

UPSC IAS – 2014

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The correct answer is C.

Both Continental drift (1) and Glacial cycles (2) are major geological and climatic phenomena that have profoundly influenced the evolution of organisms. Continental drift alters the distribution of landmasses and oceans, creating or removing physical barriers, changing climate patterns, and leading to the isolation or mixing of populations, which drives speciation and extinction. Glacial cycles cause significant changes in climate, sea levels, and habitats, leading to species migrations, adaptations, extinctions, and the formation of new species through the creation of refugia and altered selective pressures.

The theory of plate tectonics explains continental drift and is a cornerstone of modern geology. Glacial cycles have occurred repeatedly throughout Earth’s history, most notably during the Pleistocene epoch (the ‘Ice Age’).

116. Mycorrhizal biotechnology has been used in rehabilitating degraded sit

Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to

1. resist drought and increase absorptive area
2. tolerate extremes of pH
3. resist disease infestation

Select the correct answer using the codes given below:

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in

UPSC IAS – 2013

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Mycorrhizal associations significantly benefit plants, especially in challenging or degraded environments, by improving their ability to absorb water and nutrients, tolerate harsh soil conditions (including pH extremes), and resist diseases. Therefore, all three statements are correct.

Mycorrhizal fungi form symbiotic relationships with plant roots. The fungal hyphae extend far into the soil, vastly increasing the surface area for absorption of water and nutrients (particularly phosphorus and nitrogen) beyond what the plant’s root hairs can reach. This enhanced absorption capacity helps plants cope with drought stress. Mycorrhizae can also modify the rhizosphere environment and interact with soil microbes, improving plant tolerance to soil acidity/alkalinity and heavy metals, and enhancing resistance to root pathogens.

Mycorrhizal biotechnology is increasingly used in ecological restoration and sustainable agriculture due to these multifaceted benefits to plant health and resilience, reducing the need for irrigation, fertilizers, and pesticides.

117. Which of the following leaf modifications occurs/occur in desert areas

Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?

1. Hard and waxy leaves
2. Tiny leaves or no leaves
3. Thorns instead of leaves

Select the correct answer using the codes given below.

[amp_mcq option1=”1 and 2 only” option2=”2 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in

UPSC IAS – 2013

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All the listed leaf modifications occur in desert areas to inhibit water loss: hard and waxy leaves, tiny leaves or no leaves, and thorns instead of leaves.

Desert plants (xerophytes) have evolved various adaptations to survive in arid environments with limited water availability. 1. Hard and waxy leaves (with thick cuticles) reduce cuticular transpiration. 2. Having tiny leaves or shedding leaves during dry periods minimizes the surface area for transpiration. Some plants have modified stems that photosynthesize instead of leaves. 3. Thorns are often modified leaves or stipules; they drastically reduce the surface area for transpiration and also deter herbivores, preventing tissue damage that could lead to water loss.

Other adaptations in desert plants include sunken stomata, fleshy stems or leaves for water storage (succulence), extensive root systems, and C4 or CAM photosynthesis pathways which are more water-efficient.

118. Which of the following statements is/are correct? 1. Viruses lack en

Which of the following statements is/are correct?

1. Viruses lack enzymes necessary for the generation of energy.
2. Viruses can be cultured in any synthetic medium.
3. Viruses are transmitted from one organism to another by biological vectors only.

Select the correct answer using the codes given below.

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option1″]

This question was previously asked in

UPSC IAS – 2013

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Only statement 1 is correct: Viruses lack enzymes necessary for the generation of energy.

Statement 1 is correct. Viruses are acellular and obligate intracellular parasites. They do not possess their own metabolic machinery, including enzymes for energy production like respiration or fermentation. They hijack the host cell’s metabolic processes to obtain energy and replicate. Statement 2 is incorrect because viruses require living cells to replicate and cannot be cultured in synthetic non-living media. Statement 3 is incorrect because while biological vectors are one mode of transmission for some viruses, many viruses are transmitted through non-vector means such as direct contact, airborne droplets, contaminated surfaces, food, or water.

Viruses consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid), and sometimes an outer envelope derived from the host cell membrane. Their dependence on host cells for replication and metabolism distinguishes them from cellular organisms like bacteria or fungi.

119. Many transplanted seedlings do not grow because

Many transplanted seedlings do not grow because

[amp_mcq option1=”the new soil does not contain favourable minerals” option2=”most of the root hairs grip the new soil too hard” option3=”most of the root hairs are lost during transplantation” option4=”leaves get damaged during transplantation” correct=”option3″]

This question was previously asked in

UPSC IAS – 2013

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Many transplanted seedlings do not grow because most of their root hairs are lost during the transplantation process.

Root hairs are fine, delicate extensions of root epidermal cells that greatly increase the surface area for absorption of water and mineral nutrients from the soil. When a seedling is dug up for transplantation, the soil around the roots is disturbed, and a large number of these fragile root hairs are broken or stripped off. The plant’s ability to absorb water is severely reduced until new root hairs can grow, leading to ‘transplant shock’, wilting, and potentially death if sufficient water uptake cannot be re-established quickly.

While factors like unfavorable soil conditions or leaf damage can also affect transplant success, the primary and most immediate challenge for a transplanted seedling is the drastic reduction in its water absorption capacity due to root hair loss. Proper watering and minimizing root disturbance during transplantation are crucial for survival.

120. Fruits stored in a cold chamber exhibit longer storage life because

Fruits stored in a cold chamber exhibit longer storage life because

[amp_mcq option1=”exposure to sunlight is prevented” option2=”concentration of carbon dioxide in the environment is increased” option3=”rate of respiration is decreased” option4=”there is an increase in humidity” correct=”option3″]

This question was previously asked in

UPSC IAS – 2013

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Fruits stored in a cold chamber exhibit longer storage life because the low temperature significantly reduces the rate of respiration in the fruits.

Respiration is a metabolic process in fruits that consumes stored sugars and leads to ripening and senescence. By lowering the temperature, this process is slowed down, thereby extending the time before the fruit spoils.

Other factors like preventing sunlight exposure and managing humidity are also important for fruit storage, but reducing the respiration rate through low temperature is the primary mechanism by which cold storage extends shelf life. Controlled atmosphere storage (modifying CO2 and Oxygen levels) is another technique used to further extend storage life by also impacting respiration and other metabolic processes.