UPSC Geoscientist Archives

31. An ecotone generally refers to the:

An ecotone generally refers to the:

frontier between two ecosystems of different evolutionary levels.

frontier between two ecosystems of same evolutionary levels.

integration of two ecosystems of different evolutionary levels.

integration of two ecosystems of graded evolutionary levels.

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An ecotone is a transitional area between two distinct ecosystems. This zone can be a narrow belt or a wider area and typically exhibits characteristics of both adjacent ecosystems.

The core concept of an ecotone is the ‘frontier’ or ‘transition zone’ between two different ecological communities or ecosystems.

Ecotones often have a higher species diversity (edge effect) than the adjacent ecosystems, as they contain species from both communities as well as unique species adapted to the transitional conditions. The options relating to “evolutionary levels” are less central to the definition than the concept of a “frontier” or transition between *different* ecosystems.

32. Montreal Protocol ratifies:

Montreal Protocol ratifies:

restricting the production of CFCs.

sustainable development.

carbon trading.

restricting the global average temperature below 2 °C above the pre-industrial level.

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The Montreal Protocol on Substances that Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production and consumption of ozone-depleting substances, most notably chlorofluorocarbons (CFCs).

Ratified in 1987, the Montreal Protocol is considered one of the most successful international environmental agreements. Its implementation has led to a significant reduction in the emission of ODS and the slow recovery of the ozone layer.

Sustainable development is a broader concept. Carbon trading and the goal of restricting global temperature increase below 2 °C are associated with efforts to combat climate change, primarily through the Kyoto Protocol and the Paris Agreement, respectively, not the Montreal Protocol.

33. Which one among the following is true about Ozone Hole?

Which one among the following is true about Ozone Hole?

It is the loss of Tropospheric ozone over Antarctica

It is the loss of Stratospheric ozone over Antarctica

It is a hole in the Antarctic ice sheet created due to ozone

It is the loss of equatorial ozone

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The “Ozone Hole” refers to the significant thinning or depletion of the protective stratospheric ozone layer, primarily observed over the Antarctic region during the spring (August-October).

The stratospheric ozone layer absorbs most of the Sun’s harmful ultraviolet (UV) radiation. Its depletion, mainly due to human-produced chemicals like CFCs and halons, leads to increased UV radiation reaching the Earth’s surface.

Ozone depletion also occurs over the Arctic, but the phenomenon is more severe and consistent over Antarctica due to specific atmospheric conditions (polar vortex and polar stratospheric clouds). Tropospheric ozone is a greenhouse gas and an air pollutant, harmful to human health and ecosystems, and is distinct from the stratospheric ozone layer.

34. The natural rain water has a pH value of:

The natural rain water has a pH value of:

5.6

6.5

7.0

Zero

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The pH of natural, unpolluted rainwater is typically around 5.6.

Rainwater is naturally slightly acidic because carbon dioxide (CO2) from the atmosphere dissolves in it, forming weak carbonic acid (H2CO3).

Acid rain, caused by pollutants like sulfur dioxide (SO2) and nitrogen oxides (NOx), has a pH lower than 5.6. Pure water has a neutral pH of 7.0, but rainwater is never pure due to dissolved atmospheric gases.

35. Which one among the following is NOT a characteristic feature of

Which one among the following is NOT a characteristic feature of Mangrove?

They are intertidal forested wetlands

Mangrove habitat obstructs the growth and establishment of other organisms

They dominate river deltas, lagoons and estuaries

They are highly salt tolerant

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While the specific conditions of mangrove habitats (salinity, low oxygen) do exclude many non-adapted organisms, mangroves themselves provide structure, habitat, and resources that *support* the growth and establishment of a specialized community of organisms adapted to these conditions (e.g., certain fish, crustaceans, molluscs, birds, epiphytes). Therefore, it is not accurate to say the habitat broadly “obstructs the growth and establishment of *other* organisms” as it facilitates a diverse, albeit specialized, ecosystem.

Mangroves are a group of trees and shrubs that live in the intertidal zone of tropical and subtropical coastlines. They are halophytes (salt-tolerant) and possess unique adaptations like prop roots, pneumatophores, and salt-excreting leaves to survive in challenging conditions.

Mangrove ecosystems are intertidal forested wetlands, often found in estuaries, lagoons, and river deltas. They play crucial ecological roles as nurseries for marine life, coastal protection against erosion and storm surges, and carbon sequestration.

36. Which one among the following is NOT an attribute of the ‘Land Ra

Which one among the following is NOT an attribute of the ‘Land Races’?

Land Races have a ‘certain genetic integrity’

They can be very well recognised morphologically

They are highly adapted to specific soil types and local environmental variables

They don’t have specific time of seeding and date of maturity

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Landraces are typically highly adapted to their local environments, including the specific climatic cycles. This adaptation results in relatively specific timing for key phenological events like seeding and maturity that are synchronized with the local season. Therefore, stating they “don’t have specific time of seeding and date of maturity” is incorrect.

Landraces are traditional, locally adapted varieties of crops or animals that have evolved through a combination of natural selection under local conditions and human selection. They possess genetic diversity and resilience suited to their specific agroecological niche.

Attributes of landraces include distinct genetic identities, recognizable morphological traits, high adaptation to local conditions (soil, climate, pests, diseases), and they often have specific growth cycles adapted to the local season. Their genetic diversity makes them valuable resources for breeding programs.

37. Which one of the following is NOT a condition necessary for natural se

Which one of the following is NOT a condition necessary for natural selection to occur?

More organisms are born than can survive

Organisms should not vary in their characteristics within a species

Variation is inherited

Differences in reproduction and survival are due to variation among organisms

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For natural selection to occur, organisms *must* vary in their characteristics within a species. Variation is the raw material upon which selection acts.

The necessary conditions for natural selection are: variation among individuals, inheritance of variation, differential survival and reproduction based on that variation, and often, limited resources leading to competition (more offspring born than can survive).

If there were no variation within a species, all individuals would be identical, and there would be no basis for differential survival or reproduction based on traits, thus no natural selection leading to evolutionary change.

38. A growing population cannot increase indefinitely at a geometric rate

A growing population cannot increase indefinitely at a geometric rate because a given habitat has a carrying capacity. This type of growth is known as:

Exponential growth

Sinusoidal growth

Logistic growth

Chaotic growth

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The type of population growth that cannot increase indefinitely at a geometric (exponential) rate because of limitations imposed by a carrying capacity is known as logistic growth.

Logistic growth describes a population’s growth when it is limited by the carrying capacity (K) of its environment. As the population size approaches K, the growth rate slows down due to resource scarcity, increased competition, predation, or disease, resulting in an S-shaped curve.

Exponential growth occurs in an unlimited environment, resulting in a J-shaped curve. Sinusoidal growth implies oscillations around a mean, while chaotic growth refers to unpredictable fluctuations. The concept of carrying capacity is central to the logistic growth model.

39. Plants, which survive by withdrawing water from their cells to prevent

Plants, which survive by withdrawing water from their cells to prevent ice formation during extreme cold up to -40 ° C, are known as:

Frost sensitive

Frost tolerant

Frost resistant

Chilling resistant

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Plants that survive extreme cold by withdrawing water from their cells to prevent intracellular ice formation are known as frost resistant or freeze tolerant.

Frost resistance or freeze tolerance involves various physiological adaptations that allow plants to survive temperatures below freezing. Mechanisms include supercooling (preventing ice formation even below the freezing point) or dehydrating cells to allow ice to form only in extracellular spaces, preventing lethal damage from intracellular ice crystals.

Frost sensitive plants are damaged or killed by freezing temperatures. Chilling resistant plants can tolerate low temperatures above freezing (typically 0-15 °C). The description in the question specifically points to mechanisms that prevent freezing damage at sub-zero temperatures.

40. Which among the following are true about hyperthermophile microbes?

Which among the following are true about hyperthermophile microbes?

1. The preferred temperature for growth of such microbes is around 45 °C
2. They prefer to grow and reproduce at over 80 °C
3. They normally grow in deep sea floors
4. Below 60 °C they find it too cold and stop growing

Select the correct answer using the code given below:

1 and 3

2 and 3 only

2 and 4 only

2, 3 and 4

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Statements 2 and 3 are true about hyperthermophile microbes. Hyperthermophiles are extremophiles that thrive at very high temperatures, typically optimally above 80 °C, and are commonly found in environments like deep-sea hydrothermal vents.

Hyperthermophiles represent the upper temperature boundary for life as we know it. Their enzymes and cellular structures are specially adapted to withstand denaturation at extremely high temperatures.

Statement 1 is incorrect; preferred temperature around 45 °C describes mesophiles. Statement 4 is incorrect; while they prefer temperatures above 80 °C, their minimum growth temperature is typically above 60 °C, but saying they “stop growing” below 60 °C might not be universally true for all species within this group, and some might exhibit very slow growth in the range of 60-80°C. Deep sea floors, specifically hydrothermal vents, and hot springs are typical habitats.