MPSC 2022 Prelims Paper-I · Question 20 of 100

Correct — option (4). The question rests on the division of the environment into components, and on one distinction in particular: the difference between the media in which life exists and the substances of which those media are composed. The environment is ordinarily divided first into the abiotic and the biotic, and the abiotic is then divided into physical factors and chemical factors. The physical factors are the conditions — temperature, light, rainfall, humidity, wind, pressure and the lie of the land — together with the media themselves, the air, the water and the soil in which organisms live. The chemical factors are the substances present in those media: the gases of the atmosphere, the salts and nutrients dissolved in water, the mineral and organic constituents of the soil, and the properties that follow from them such as pH and salinity. Tested against that distinction, none of the four listed pairs names the chemical environment. Statement (a) pairs temperature, which is a physical condition, with soil, which is a medium. Statement (b) pairs water and soil, again two media rather than the chemical substances they contain. Statement (c) pairs vegetation, which is living and therefore biotic, with water. Statement (d) pairs human functions with biological components, and both belong to the living world rather than to the chemistry of the surroundings. Since not one of the four statements identifies the chemical component of the environment, the row that rejects all of them is the answer, and that is option (4). It is worth adding that the exact phrase “None of the above” is on offer six times among this paper's four hundred options, and two further rows say the same thing in other words, so its presence here signifies nothing by itself; it has to be earned by disposing of the other three, which is what the reasoning above does.

• (1)Only (a) and (b) — This row accepts statement (a), temperature and soil. Temperature is the clearest case of a physical factor in the whole question: it is a condition of the surroundings, measured in degrees, and it governs the rate of every biological process without being a substance at all. Soil is a medium, the mixture of mineral particles, organic matter, water, air and living organisms in which plants root; it certainly has a chemistry, and the nutrients, salts and pH of the soil solution are part of the chemical environment, but the soil itself is not a chemical factor. The statement therefore pairs a physical condition with a physical medium and names nothing chemical. The distinction to hold is between where an organism lives and what it is chemically surrounded by, and this option confuses the two twice over.
• (2)Only (b) — This row accepts only statement (b), water and soil, and it is the most plausible of the wrong rows because both items do have an important chemistry. Dissolved oxygen, carbon dioxide, nitrates, phosphates and salinity in water, and the nutrients, minerals and pH of the soil solution, are all genuinely part of the chemical environment. But water and soil named as such are the media themselves — the hydrosphere and the pedosphere — and belong with the physical components; what belongs to the chemical environment is the content, not the container. A candidate who chooses this row is answering a slightly different question from the one asked, namely which media carry chemical factors rather than which factors are chemical, and the difference between those two questions is exactly what the item is testing.
• (3)Only (c) and (d) — This row accepts statement (c), vegetation and water. Vegetation disposes of it at once: plants are living organisms and belong to the biotic component of the environment, not to any part of the abiotic one, and no classification places them among chemical factors. That leaves water, which as argued above is a medium rather than a chemical factor in itself. The option is worth noticing because it mixes a biotic item with an abiotic one, a common construction in this block, and because it shows why the first sorting a candidate should make in any environment question is between the living and the non-living. Once vegetation is identified as biotic, the statement cannot describe the chemical environment whatever is said about the other half of the pair.

The environment of an organism is the sum of everything outside it that affects it, and it is analysed by dividing that sum into components. The first division is between the abiotic and the biotic. The biotic component comprises all living things and their activities, and is often sorted by function into producers, consumers and decomposers; human activity is sometimes separated out as the anthropogenic or cultural environment because of its scale. The abiotic component is then divided again. Its physical side comprises the conditions and the media — solar radiation and light, temperature, rainfall and humidity, wind and pressure, the relief and slope of the land, and the air, water and soil in which organisms live. Its chemical side comprises the substances present in those media: the gases of the atmosphere, the inorganic nutrients and salts, the organic compounds released by decay, and the derived properties such as acidity and salinity. The value of the division is that it explains how an ecosystem works, because energy enters as light and flows one way through the biotic component while chemical elements cycle round and round between the abiotic and the biotic in the carbon, nitrogen, phosphorus and water cycles. Anything that changes the chemical environment therefore changes the ecosystem: acidification of soil or water, eutrophication from excess nutrients, salinity in irrigated land and the buildup of pollutants all act on that side of the system.

This question is a definitional one, and it is set in a form that this paper uses often: a stem asks about a category, four short pairs are offered as statements, and the rows include a none-of-the-above escape. Two features of the printing deserve notice. The first is that the stem and the line above the options do not agree — the stem asks which factors are included in the chemical environment, while the lead-in line asks which of the statements given above is or are correct — and the sense the candidate must work with is the one in the stem. The second is that a none-of-the-above row is available here, and the exact phrase “None of the above” appears six times across this paper's four hundred options and “All of the above” ten times, with a few further rows spelling either idea out in full. The presence of an escape row proves nothing about whether it is the answer; the only safe method is to test each of the other three and reject them on their merits, and to choose the escape row only when every alternative has actually failed. Candidates lose marks in both directions here, some refusing to believe an escape row can be right and others choosing it whenever they are unsure.

• The environment is divided first into abiotic and biotic components, the abiotic being further divided into physical factors and chemical factors.
• Physical factors include temperature, light, rainfall, humidity, wind and pressure, together with the media of air, water and soil in which organisms live.
• Chemical factors are the substances present in those media — atmospheric gases, dissolved salts and nutrients, the mineral and organic constituents of soil, and the resulting properties such as pH and salinity.
• Vegetation, animals, micro-organisms and human activity belong to the biotic component, human activity often being separated as the anthropogenic or cultural environment.
• Energy flows one way through an ecosystem from sunlight through producers and consumers, while chemical elements cycle between the abiotic and biotic components in the carbon, nitrogen, phosphorus and water cycles.

• Treating a medium as a factor, so that water and soil are taken for chemical components when it is their dissolved and mineral content that is chemical
• Overlooking that vegetation and human activity are biotic, which by itself disqualifies two of the four statements offered here
• Choosing a none-of-the-above row from uncertainty rather than from having tested and rejected each of the other three
• Reading the lead-in line instead of the stem when the two do not agree, as they do not in this question

Definitional questions on the components of the environment appear early in the environment block of MPSC papers, usually as a straight question about what belongs to which component, sometimes as a matching item joining components to examples, and sometimes as a statement set of the kind used here. The Commission also tests the same division indirectly, by asking which factor limits the distribution of a species or which component a named pollutant acts on. Escape rows are used freely in this paper, so the technique of testing every option before accepting an all-of-the-above or none-of-the-above row is worth practising deliberately. The preparation that covers the whole family is a single diagram of the environment split into abiotic physical, abiotic chemical and biotic components, with four or five examples written under each heading.

No directly related past PYQ was found.

• practice — not a real PYQ

  Which of the following belongs to the chemical component of the environment ?

  • (a)Wind speed over the surface
  • (b)Dissolved nitrates and phosphates in water
  • (c)The slope of the land
  • (d)The decomposer organisms in the soil

  Answer(b) Dissolved nitrates and phosphates in water — these are substances present in the medium and therefore chemical factors, and their excess is what produces eutrophication. Wind speed and the slope of the land are physical factors, one a condition of the atmosphere and the other a feature of relief, while decomposer organisms are living and belong to the biotic component along with plants, animals and human activity.

• practice — not a real PYQ

  In an ecosystem, which of the following statements is correct ?

  • (a)Both energy and nutrients move in a cycle
  • (b)Energy flows in one direction while nutrients circulate between the abiotic and biotic components
  • (c)Energy circulates while nutrients flow in one direction and are lost
  • (d)Neither energy nor nutrients move between the components

  Answer(b) Energy flows in one direction while nutrients circulate between the abiotic and biotic components — solar energy enters through the producers, passes along the food chain and is dissipated as heat, so it cannot be reused, whereas carbon, nitrogen, phosphorus and water pass repeatedly between organisms and their surroundings through the biogeochemical cycles.