Ecology

41. What is ‘duff’?

What is ‘duff’?

Partially decomposed litter
Weathered rock
Muddy puddle
Carcass of a dead animal
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The correct answer is Partially decomposed litter.
‘Duff’ is an ecological term referring to the layer of organic matter on the floor of a forest or wooded area, consisting of fallen leaves, twigs, and other plant debris in various stages of decomposition. It is the layer above the mineral soil but below the fresh litter.
Duff is also known as the O horizon (organic layer) in soil profiles, specifically the Oi (slightly decomposed) and Oe (moderately decomposed) sub-horizons, although the term ‘duff’ sometimes specifically refers to the Oel and Ofh layers in certain classification systems. It plays a significant role in forest nutrient cycling and fire behavior.

42. What is ecological amplitude?

What is ecological amplitude?

The range of demands and consequent range of tolerance of a species to the fluctuations in environmental conditions
The range of tolerance of a species in constant environmental conditions
The range of demands of a species in constant environmental conditions
The range of ecological conditions found in a biome
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The correct answer is The range of demands and consequent range of tolerance of a species to the fluctuations in environmental conditions.
Ecological amplitude refers to the range of environmental conditions (such as temperature, moisture, salinity, pH, etc.) within which a species can survive, grow, and reproduce. It is determined by the physiological tolerance limits of the species to fluctuations in these conditions and its specific resource requirements (demands).
Species with a wide ecological amplitude are called eurytopic and can inhabit diverse environments. Species with a narrow ecological amplitude are called stenotopic and are restricted to specific environmental conditions. Options B and C are incomplete as they focus only on tolerance or demands, not the combined range of conditions. Option D describes a characteristic of a biome, not a species’ ecological amplitude.

43. In deep ponds and lakes, which one of the following vertical zones rec

In deep ponds and lakes, which one of the following vertical zones receives least light penetration?

Surface
Littoral zone
Limnetic zone
Profundal zone
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The correct answer is Profundal zone.
In deep ponds and lakes, the water column is divided into different zones based on light penetration. The Profundal zone is the deep-water zone beneath the Limnetic zone, where light penetration is insufficient for photosynthesis. It is often dark and characterized by decomposition.
The Surface (Epilimnion) and Limnetic zones are well-lit areas where photosynthesis can occur. The Littoral zone is the shallow area near the shore where light reaches the bottom, allowing rooted plants to grow. The Profundal zone is typically aphotic (without light).

44. Which one among the following statements regarding Ecotone is correct

Which one among the following statements regarding Ecotone is correct ?

It represents a transitional region between two ecosystems.
It represents a region which is ecologically perfect.
It represents a region which is ecologically barren of organisms.
It represents an ecosystem containing deep marine organisms.
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An ecotone is a transitional area between two different ecosystems. It is where elements from both bordering communities intermix. This often results in a higher biodiversity than either of the adjacent ecosystems, due to the presence of species from both communities and unique species adapted to the transitional conditions (known as the edge effect).
An ecotone is a boundary or transitional zone between two ecosystems.
Examples of ecotones include mangrove forests (between marine and terrestrial ecosystems), grasslands (between forest and desert), and estuaries (between river and ocean). They are often areas of high ecological interest due to their unique characteristics and biodiversity.

45. Mangroves represent :

Mangroves represent :

Epiphytic vegetation
Salt-tolerant vegetation
Floodplain vegetation
Playa vegetation
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Mangroves are a group of trees and shrubs that live in coastal intertidal zones. They are adapted to unique conditions, including low-oxygen soil and high salinity levels (brackish or saltwater). Their ability to tolerate and thrive in saline environments is a defining characteristic. Therefore, mangroves represent salt-tolerant vegetation.
– Mangroves are coastal plants.
– They are adapted to survive in saline or brackish water.
– They possess specialized physiological adaptations to deal with salt, waterlogged soil, and tidal fluctuations.
Mangrove ecosystems are vital coastal habitats, providing ecological services such as coastal protection against erosion and storms, serving as nursery grounds for various marine species, and sequestering carbon. They are found in tropical and subtropical regions worldwide.

46. Which one of the following is the appropriate sequential order of ecol

Which one of the following is the appropriate sequential order of ecological succession ?

Invasion – Nudation – Competition and coaction – Reaction – Stabilization
Nudation – Invasion – Competition and coaction – Reaction – Stabilization
Nudation – Invasion – Reaction – Competition and coaction – Stabilization
Invasion – Nudation – Competition and coaction – Reaction – Stabilization
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Ecological succession is the process of change in the species structure of an ecological community over time. It typically occurs in a somewhat predictable sequence of stages. The question asks for the correct sequential order of these stages.
The classic sequence of ecological succession (particularly primary succession on bare ground) involves several steps:
1. **Nudation:** The creation of a bare area devoid of life (e.g., by volcanic eruption, glacier retreat, landslide).
2. **Invasion:** The arrival of organisms (propagules like seeds, spores, or larvae) into the bare area. This includes migration and ecesis (establishment and growth).
3. **Competition and Coaction:** Interactions between the established organisms and with the environment, including competition for resources and modifications of the environment.
4. **Reaction:** The established organisms modify the environment (e.g., adding organic matter, changing soil pH, altering light levels), making it more or less suitable for themselves and often creating conditions favorable for the invasion and growth of new species.
5. **Stabilization:** The community reaches a relatively stable state, often referred to as a climax community, where the species composition changes little over time.
Comparing the options with the standard sequence, option B (Nudation – Invasion – Competition and coaction – Reaction – Stabilization) correctly follows the order of the main stages of ecological succession from the initial bare state to a stable community.

47. Nitrogen cycle is one of the most important microorganisms-mediated ch

Nitrogen cycle is one of the most important microorganisms-mediated chemical reactions in aquatic and soil environments. In this context consider the following statements :

  • 1. Nitrogen fixation is the process of oxidising NH₃ to NO₃⁻.
  • 2. Nitrification process causes reduction of NO₃ and NO₂⁻ to NO₂, followed by recycling of N₂ to the atmosphere.
  • 3. Denitrification converts molecular N₂ into a fixed form as an organic nitrogen.

How many of the statements given above is/are correct ?

1
2
3
None
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Correct Answer: D
– Statement 1 is incorrect: Nitrogen fixation is the process where atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or other nitrogenous compounds. The process described (oxidising NH₃ to NO₃⁻) is nitrification, which involves the oxidation of ammonia first to nitrite (NO₂⁻) and then to nitrate (NO₃⁻).
– Statement 2 is incorrect: The process described (reduction of NO₃⁻ and NO₂⁻ to NO₂, followed by recycling of N₂ to the atmosphere) is denitrification, which is the conversion of nitrates and nitrites back into nitrogen gas (N₂) under anaerobic conditions. Nitrification is the oxidation of ammonia compounds.
– Statement 3 is incorrect: Denitrification converts fixed nitrogen (like nitrates and nitrites) back into atmospheric molecular nitrogen (N₂). The process that converts molecular N₂ into a fixed form as organic nitrogen (via ammonia) is nitrogen fixation.
The nitrogen cycle is a complex biogeochemical cycle involving various microbial processes. The main processes are nitrogen fixation (N₂ to NH₃), nitrification (NH₃ to NO₂⁻ to NO₃⁻), assimilation (uptake of nitrogen by organisms), ammonification (organic nitrogen to NH₃), and denitrification (NO₃⁻ to N₂). Each process is crucial for the availability and cycling of nitrogen in ecosystems.

48. What is ‘phenology’?

What is ‘phenology’?

Study of phenol production in plants
Study of periodical phenomena of plants, such as the time of flowering in relation to climate
Study of excretory pathway of phenols by herbivores
Study of phenotypic variation in newborn individuals of cats
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The correct answer is ‘Study of periodical phenomena of plants, such as the time of flowering in relation to climate’.
Phenology is the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life. It focuses on the timing of recurring biological events, such as flowering, leaf unfolding, migration, and breeding, and their correlation with environmental factors like temperature, precipitation, and photoperiod.
Phenological studies are crucial for understanding the impacts of climate change on ecosystems. Changes in temperature and other climatic factors can alter the timing of phenological events, potentially leading to mismatches between interacting species (e.g., plants and their pollinators or herbivores) and disrupting ecosystem dynamics.

49. Quadrat is generally used to enumerate the number of

Quadrat is generally used to enumerate the number of

animals breeding in a pond
burrows present in an anthill
plants present in a unit area
epiphytes on a tree
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A quadrat is a standard frame, typically square or rectangular, used in ecological surveys to sample a specific area. Quadrats are primarily used for studying sessile or slow-moving organisms, most commonly plants. By placing quadrats in multiple locations within a habitat and counting the number of plants (or other organisms like fungi or invertebrates) of interest within each quadrat, ecologists can estimate population density, frequency, and distribution for the entire area. While quadrats can sometimes be adapted for studying other organisms, their fundamental use is to define a unit area for sampling, making them most suitable for enumerating stationary populations like plants.
– A quadrat is a sampling frame defining a unit area.
– Used in ecological surveys.
– Most commonly applied to enumerate sessile or slow-moving organisms.
– Ideal for sampling plant populations in a defined area.
Sampling methods for animals vary depending on the species and habitat and might involve trapping, observation transects, or counting signs like burrows or tracks. While a quadrat could theoretically be used to count burrows in a defined area, its standard application is primarily for vegetation surveys or similar studies of organisms within a fixed plot.

50. What is ‘bioenergetic approach’ in modern ecology?

What is ‘bioenergetic approach’ in modern ecology?

Study of similarities and differences in food relationships among living organisms and various forms of energy supporting life
Study of energy retention by ecosystems under threat
Study of energy loss by ecosystems under threat
Study of energy in deep oceans during cyclone buildup
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The bioenergetic approach in modern ecology is the study of similarities and differences in food relationships among living organisms and various forms of energy supporting life.
The bioenergetic approach views ecosystems in terms of energy flow and transformation. It quantifies the amount of energy at different trophic levels, how efficiently it is transferred from one level to the next, and how energy is lost from the system. This involves understanding food webs (food relationships) and the different forms of energy (solar energy captured by producers, chemical energy in biomass) that sustain life within the ecosystem.
Key concepts in bioenergetic ecology include primary production, secondary production, trophic efficiency, and ecological pyramids of energy. This approach is crucial for understanding ecosystem structure, function, and stability.
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