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Ecology

📆 September 25, 2024

Total Questions: 88

51. An inverted pyramid of biomass can be found in which ecosystem? [R.A.S./R.T.S.(Pre) 2021]

Correct Answer: (a) Marine
Solution:An inverted pyramid of biomass can be found in marine ecosystem. The pyramid of biomass in sea is generally inverted because the biomass of fishes far exceeds that of phytoplankton. Hence option (1) is correct.

52. Which of the following statements is true about Bionomics? [U.P.U.D.A./L.D.A. (Pre) 2001 ]

1. It means "management of life'.
2. It is synonymous with ecology.
3. It stresses the value of natural systems which influence human systems.
Codes :

Correct Answer: (c) 2 and 3
Solution:In ecology, bionomics (Greek: bio = life; nomos = law) is the comprehensive study of an organism and its relation to its environment. Another way of expressing this word is the term currently referred to as "ecology". It stresses the value of natural systems which influence human systems and is not related to the management of life.

53. Which one of the following organisms is likely to show the highest concentration of DDT, once it has been introduced into the ecosystem? [I.A.S. (Pre) 1997]

Correct Answer: (c) Snake
Solution:DDT is a non-biodegradable, biomagnifying pollutant (used as insecticide) which increases in concentration from producers, primary consumers, secondary consumers to tertiary consumers. In the question, only the snake represents the tertiary consumers, so the concentration of DDT will be highest in the snake.

It is a synthetic chemical compound that was widely used as an insecticide. Because it is fat-soluble and persistent, DDT can accumulate in the food chain, leading to biomagnification, meaning its concentration increases as it moves up the food chain.

54. The cycling of elements in an ecosystem is called : [U.P.P.C.S. (Pre) 2020, 2021]

Correct Answer: (b) Biogeochemical cycles
Solution:In Earth science, a biogeochemical cycle is a pathway by which a chemical substance moves through both biotic and abiotic components of Earth. Biogeochemical cycles of nitrogen, phosphorus and carbon, etc. are found in nature.

Chemical cycle: While the term "chemical cycle" is broad and encompasses any movement of chemicals, "biogeochemical cycles" specifically highlight the role of living organisms in the process.
Geological cycles: Geological cycles focus on the long-term processes that shape the Earth's geological features, such as plate tectonics and erosion.

Geochemical cycles: Geochemical cycles deal with the movement of chemical elements within the Earth's geological components, like the crust and mantle. This is a broader term than biogeochemical cycles, as it doesn't necessarily involve living organisms.

55. In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to entry the cycle? [I.A.S. (Pre) 2021]

Correct Answer: (c) Phosphorus cycle
Solution:Phosphorus is a chemical element found on Earth in numerous compound forms, such as the phosphate ion (PO), located in water, soil and sediments. Much of the phosphorus on Earth is tied up in rock and sedimentary deposits, from which it is released by weathering, leaching, and mining. Some of it passes through freshwater and terrestrial ecosystems via plants, grazers, predators, and parasites, to be returned to those ecosystems by death and decay. Much of it, however, is deposited in the sea, in shallow sediments, where it circulates readily, or in ocean deeps, whence it wells up only occasionally. Phosphorus is brought back to the land through fish harvests and through collection of guano deposited by seabirds.

56. In the grassland, trees do not replace the grasses as a part of an ecological succession because of : [I.A.S. (Pre) 2013]

Correct Answer: (c) water limits and fire
Solution:Ecological succession is the gradual process by which ecosystems change and develop over time. In grassland, trees have already been cleared away due to fires in the past, which also changes the ground composition. Without the trees to hold them, water washes away most of the soil and the underlying ground becomes the pioneer population, which is then replaced by grass. The grass, however, absorbs most of the water before it reaches the roots of the shrubs. Thus, the ecological succession does not occur beyond the grass.

57. Which one of the following is the correct sequence of the phases of biotic succession? [U.P.P.C.S. (Mains) 2016]

Correct Answer: (a) Nudation, Migration, Ecesis, Reaction, Stabilization
Solution:Biotic succession is a natural process of displacement of one particular community by another in a particular area. A scientist named Odum described it as a sequenced process. The correct order of biotic succession is as follows:

Nudation

↓

Migration

↓

Ecesis

↓

Reaction

↓

Stabilization

1. Nudation: It is the development of a bare site uninhabited by any organisms. The process is usually caused by disturbances. These factors can be either topographic (soil erosion, wind action etc); climatic (hails, storm, glaciations, fire etc.); or biotic (human activities).

2. Invasion or migration: The process of invasion or migration helps the arrival of seeds, spores or other reproductive propagules for establishment of species. Invasive species are non native organisms which can spread widely in a community.

3. Ecesis: This is the initial establishment of plant community. This is dependent on the soil structure. The stage is also called as 'colonization'. In this stage, the early colonizing species proliferate abundantly through germination, growth, and reproduction. Ecesis is due to allogenic mechanisms alone. This is the stage at which the pioneer species survive the dispersal mechanisms.

4. Reaction: The environmental conditions get modified by the action of species occupying the habitat. These changes subsequently trigger the displacement and replacement of one species by another.

5. Stabilization is the process by which the climax community gets established. A climax community is mature, self sustaining, stable and is the final stage of succession. The physical and chemical conditions are altered and stabilized to such levels that it supports the entire community. The climax communities are best adapted to the regions of succession and the community structure is likely to continue until another disturbance steps in.

58. The concept of 'Ecological Transition' was first used by: [U.P.P.C.S. (Pre) 2020]

Correct Answer: (b) Bennett
Solution:The concept of 'Ecological Transition' was first used by John W. Bennett. He proposed the concept in his book "The Ecological Transition: Cultural Anthropology and Human Adaptation". "Ecological transition" mean, the development of an anthropocentric orientation toward the natural world that emerged in the Western Renaissance but has since characterized every civilization and nation. Ecologically speaking, the transition is expressed in the growing incorporation of Nature into Culture and by the breakdown of local self sufficiency-the ability of the local group to satisfy its needs with existing resources in a particular geographical range.

59. The entire sequence of communities that successively change in a particular area are called : [U.P.P.C.S. (Pre) 2020]

Correct Answer: (b) Sere
Solution:The entire sequence of communities that successively change in a particular area are called 'Sere'.

Community dynamics: Community dynamics refers to the interactions between
different species within a community, including competition, predation, and symbiosis. While these dynamics are important in succession, they don't describe the overall process of succession itself.

Pyramid of biomass: A pyramid of biomass shows the relative amount of biomass at each trophic level in an ecosystem. This is a concept related to energy flow within ecosystems, not the process of ecological succession.

60. The movement of nutrient elements through various components of an ecosystem is called : [U.P.P.C.S. (Pre) 2020]

Correct Answer: (a) Bio-geochemical cycle
Solution:The words "Bio" means living, "Geo" means rock and "Chemical" means element. Thus, the biogeochemical cycle can be defined as the cyclic exchange of material between living organisms and their nonliving environment to ensure conservation of nutrients in the ecosystem. Therefore, the nutrients are never lost from the ecosystems and the earth's components are constantly recycled.

Depending on the nature of the reservoir, the nutrient cycles or biogeochemical cycles are of two types-

(a) Gaseous Biogeochemical cycle.
(b) Sedimentary Biogeochemical cycle.

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