Ecology

21. In an ecosystem why is the number of trophic levels of a food chain us

In an ecosystem why is the number of trophic levels of a food chain usually limited ?

Lower trophic level has lesser energy than the higher trophic level
Because of the loss of energy at each trophic level
Higher trophic level individual can control the lower ones more efficiently
Limited trophic level makes a food chain less vulnerable to parasites
This question was previously asked in
UPSC CAPF – 2024
Download PDFAttempt Online
The correct option is B. The number of trophic levels in a food chain is usually limited because of the significant loss of energy at each trophic level.
– According to the 10% rule of energy transfer in ecosystems, only about 10% of the energy available at one trophic level is transferred to the next higher trophic level. The rest is lost as heat, used for metabolic processes, or not consumed.
– This drastic reduction in available energy at each successive level limits the biomass and population size that can be supported.
– After a few trophic levels, there is insufficient energy remaining to support a viable population of organisms at a higher level, thus limiting the food chain length.
Lower trophic levels (producers) contain the most energy (biomass). Energy flows unidirectionally up the food chain, becoming less available at each step. While other factors like biomass and population dynamics play a role, the fundamental limit is imposed by energy transfer efficiency.

22. The boundary layer of the forest at which the energy exchange occurs a

The boundary layer of the forest at which the energy exchange occurs and some insolation is returned directly to space is

forest floor
forest soil
forest canopy
forest litter
This question was previously asked in
UPSC CAPF – 2022
Download PDFAttempt Online
The forest canopy, which is the upper layer formed by the crowns of trees, is the primary interface between the forest ecosystem and the atmosphere. This is where the majority of solar radiation is intercepted, leading to energy exchange through processes like photosynthesis, transpiration, and radiation absorption/reflection. A significant portion of incoming solar radiation is absorbed or reflected by the canopy, influencing the microclimate below and contributing to the Earth’s energy balance (with some insolation reflected back to space).
The question describes the boundary layer of the forest involved in significant energy exchange and reflection of insolation. This description perfectly matches the functions of the forest canopy.
The forest floor, soil, and litter are important components of the forest ecosystem but are not the primary interface for the initial large-scale energy exchange with the atmosphere via direct insolation and radiation. The canopy is the highest and most exposed layer, thus playing this crucial role.

23. Which of the following factors are needed for the growth of corals?

Which of the following factors are needed for the growth of corals?

  • Freshwater
  • Clear shallow salt water
  • Plenty of sunlight for photo-synthesis
  • Warm water between 23 °C and 25 °C

Select the correct answer using the code given below.

1, 3 and 4 only
2, 3 and 4 only
1 and 2 only
1, 2, 3 and 4
This question was previously asked in
UPSC CAPF – 2021
Download PDFAttempt Online
The factors needed for the growth of corals are clear shallow salt water, plenty of sunlight for photo-synthesis, and warm water between 23 °C and 25 °C.
Coral reefs thrive in specific marine environments characterized by warm, clear, shallow saltwater and sufficient sunlight to support the symbiotic algae (zooxanthellae) living within the coral tissues.
Let’s evaluate each factor:
1. **Freshwater:** Corals are marine organisms and are highly sensitive to salinity changes. Freshwater input (e.g., from rivers) can be detrimental to coral health. Thus, freshwater is NOT needed.
2. **Clear shallow salt water:** Corals need saltwater. Shallow water allows sunlight penetration. Clear water is crucial because suspended sediment can block sunlight (harming zooxanthellae) and smother corals. This factor is essential.
3. **Plenty of sunlight for photo-synthesis:** Most reef-building corals have symbiotic algae (zooxanthellae) living in their tissues. These algae perform photosynthesis and provide the coral with energy. Sufficient sunlight is necessary for this process. This factor is essential.
4. **Warm water between 23 °C and 25 °C:** Corals generally require warm water temperatures, typically between 20°C and 28°C. The range 23-25°C falls well within the optimal temperature zone for many coral species. Sustained temperatures outside this range (too hot or too cold) can cause stress and bleaching. This factor is essential.
Therefore, factors 2, 3, and 4 are needed for the growth of corals.

24. Which of the following statements about tropical rain forests are corr

Which of the following statements about tropical rain forests are correct?

  • 1. The soils of tropical rain forests are quite infertile.
  • 2. The vegetation is evergreen, enabling photosynthesis to take place year around.
  • 3. They have been described as ‘deserts covered by trees’.
  • 4. They are most productive land-based ecosystem.

Select the correct answer using the code given below.

2 and 4 only
1, 3 and 4 only
1, 2 and 3 only
1, 2, 3 and 4
This question was previously asked in
UPSC CAPF – 2021
Download PDFAttempt Online
The correct answer is D) 1, 2, 3 and 4.
Let’s examine each statement:
1. The soils of tropical rain forests are quite infertile: Correct. High rainfall leads to rapid leaching of nutrients. Rapid decomposition returns nutrients, but they are quickly absorbed by the dense vegetation, leaving the soil itself poor in nutrients, especially mineral nutrients.
2. The vegetation is evergreen, enabling photosynthesis to take place year around: Correct. Tropical rainforests experience high temperatures and rainfall throughout the year, supporting continuous growth and photosynthesis, resulting in evergreen forests.
3. They have been described as ‘deserts covered by trees’: Correct. This phrase highlights the paradox of incredibly lush vegetation growing on nutrient-poor soil, contrasting the high biomass with the low soil fertility, much like how a desert is characterized by poor soil although it lacks the trees.
4. They are most productive land-based ecosystem: Correct. Due to favorable conditions of high sunlight, temperature, and water availability year-round, tropical rainforests exhibit the highest rates of primary productivity among all terrestrial ecosystems.
All four statements accurately describe characteristics of tropical rain forests.
The high productivity of tropical rainforests is concentrated in the biomass, not the soil. The rapid nutrient cycling makes the ecosystem vulnerable if the vegetation cover is removed, as the underlying soil cannot support regrowth for long without the constant input from decomposing organic matter. Deforestation in these areas often leads to soil degradation.

25. Transition zone of varied natural vegetation occupying the boundary be

Transition zone of varied natural vegetation occupying the boundary between two adjacent and differing plant communities is known as

ecological succession
ecotone
ecological niche
climax
This question was previously asked in
UPSC CAPF – 2020
Download PDFAttempt Online
The correct option is B.
An ecotone is a transition area between two biological communities. It is the zone where two communities meet and integrate, and it often contains a diversity of species characteristic of both communities, as well as some species that are unique to the transition zone itself.
Ecological succession is the process of change in the species structure of an ecological community over time. An ecological niche describes the role and position a species has in its environment. Climax community is the stable, mature stage of ecological succession. The description provided in the question accurately defines an ecotone.

26. Which one of the following does NOT illustrate the importance of the C

Which one of the following does NOT illustrate the importance of the Coral Reef ?

They provide employment to the people
They supply building materials
They protect shoreline from storms
They protect communities from earthquakes
This question was previously asked in
UPSC CAPF – 2020
Download PDFAttempt Online
Protecting communities from earthquakes does NOT illustrate the importance of coral reefs.
Coral reefs are biological structures that provide ecological services such as habitat for marine life, coastal protection by acting as natural breakwaters against waves and storms, and economic benefits through tourism and fisheries (employment). Earthquakes are geological events caused by tectonic plate movements and are not related to coral reefs.
Coral reefs are vital ecosystems that support high biodiversity. Their structural complexity helps dissipate wave energy, reducing erosion and damage to coastlines during storms and tsunamis. They also form the basis of lucrative industries like fishing and tourism.

27. Phreatophytes are the plants adapted to grow in

Phreatophytes are the plants adapted to grow in

moist shaded places
rocky environments
arid environments
active volcanic lava
This question was previously asked in
UPSC CAPF – 2019
Download PDFAttempt Online
The correct answer is C, arid environments.
Phreatophytes are plants that are adapted to arid or semi-arid environments by having very deep root systems that can reach the water table.
The term “phreatophyte” comes from the Greek words ‘phrear’ (well) and ‘phuton’ (plant). These plants rely on groundwater for survival, making them common indicators of groundwater levels in regions where surface water is scarce.

28. The ecological niche of an organism relates to

The ecological niche of an organism relates to

specific habitat of the organism
symbiotic relationship with other organisms
diverse occurrence of a species under different conditions
its interaction with all other organisms
This question was previously asked in
UPSC CAPF – 2017
Download PDFAttempt Online
The ecological niche of an organism is its functional role and position within an ecosystem. It encompasses not just where an organism lives (habitat, A), but also how it interacts with other organisms (biotic interactions) and the environment (abiotic conditions), its resource use, and its position in the food web. While A, B, and C touch upon aspects related to the niche (habitat is part of the environment it occupies, symbiotic relationships are a type of interaction, and occurrence under different conditions relates to the range of its niche), option D, “its interaction with all other organisms,” best represents the biotic aspect of its functional role within the community, which is a crucial component of the ecological niche, especially in the context of Elton’s definition (the animal’s place in the biotic environment). Although a complete definition includes abiotic interactions and resource use, among the given options, D is the most comprehensive in describing the organism’s role within the living part of the ecosystem.
The ecological niche is the functional role or ‘profession’ of an organism in an ecosystem, including its interactions with other organisms and the environment, and its resource use.
Ecological niche is a complex concept with different definitions. Hutchinson defined it as an “n-dimensional hypervolume” representing the range of environmental conditions and resources within which a species can survive and reproduce (fundamental niche) or actually does so in the presence of competitors and predators (realized niche). Elton’s definition focused on the organism’s place and role in the community. Option D aligns well with the role aspect and biotic interactions emphasized in some definitions.

29. Study of a single species and the environmental factors in its habitat

Study of a single species and the environmental factors in its habitat is called

Genecology
Synecology
Autecology
Ethology
This question was previously asked in
UPSC CAPF – 2017
Download PDFAttempt Online
The correct answer is C) Autecology.
Autecology is the branch of ecology concerned with the study of the ecological relationships of a single species or population with its environment. It focuses on how an individual species interacts with the biotic and abiotic factors in its habitat, including its adaptations, physiological responses, life cycle, and population dynamics.
A) Genecology is the study of the genetic composition and evolutionary history of plant populations in relation to their ecological environments.
B) Synecology is the study of ecological relationships within biological communities, focusing on the interactions among different species and the structure and function of entire ecosystems.
D) Ethology is the scientific study of animal behavior, usually in natural conditions.

30. NPP (Net Primary Productivity) is highest for

NPP (Net Primary Productivity) is highest for

tropical forests
swamps
reefs
woodland and shrub land
This question was previously asked in
UPSC CAPF – 2017
Download PDFAttempt Online
The correct answer is B) swamps.
Net Primary Productivity (NPP) is the rate at which producers (like plants) accumulate biomass, equal to Gross Primary Productivity minus the rate of respiration. Ecosystems with high light availability, abundant water, warmth, and nutrient-rich conditions tend to have high NPP. Among the given options, tropical forests, swamps, and reefs all have very high NPP per unit area. However, swamps and marshes (a type of wetland) are consistently cited in ecological studies as having among the highest rates of NPP globally, often exceeding tropical forests and reefs due to high nutrient availability from water flow and decomposition under saturated conditions.
Typical NPP values (in g Carbon/m²/year) for these ecosystems can range widely:
* Tropical forests: 1000-3500
* Swamps and Marshes: 800-3500
* Algal beds and reefs: 1000-2500
* Woodland and shrub land: 200-2000
While the ranges overlap, many ecological sources point to swamps/marshes and estuaries as having the absolute highest peak NPP values per unit area.
Page 1Page 2Page 3Page 4Page 5
Exit mobile version