[Mission 2024] STATIC QUIZ, 6 April 2024 – Environment

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We will post 5 questions daily on static topics mentioned in the UPSC civil services preliminary examination syllabus. Each week will focus on a specific topic from the syllabus, such as History of India and Indian National Movement, Indian and World Geography, and more.

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• Question 1 of 5 1. Question Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its a) Ecology b) Ecosystem c) Ecological Niche d) Ecotone Correct Solution: c) What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats? The most important ones are temperature, water, light and soil. We must remember that the physico-chemical (abiotic) components alone do not characterize the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. We assume that over a period of time, the organism had through natural selection, evolved adaptations to optimise its survival and reproduction in its habitat. Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche. Incorrect Solution: c) What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats? The most important ones are temperature, water, light and soil. We must remember that the physico-chemical (abiotic) components alone do not characterize the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. We assume that over a period of time, the organism had through natural selection, evolved adaptations to optimise its survival and reproduction in its habitat. Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.

#### 1. Question

Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its

• a) Ecology

• b) Ecosystem

• c) Ecological Niche

• d) Ecotone

Solution: c)

What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats?

The most important ones are temperature, water, light and soil. We must remember that the physico-chemical (abiotic) components alone do not characterize the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. We assume that over a period of time, the organism had through natural selection, evolved adaptations to optimise its survival and reproduction in its habitat. Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.

Solution: c)

What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats?

• Question 2 of 5 2. Question Consider the following statements. In a terrestrial ecosystem, a much larger fraction of energy flows through the grazing food chain than through the detritus food chain. In an aquatic ecosystem, detritus food chain is the major conduit for energy flow. Detritus food chain may be connected with the grazing food chain at some levels. How many of the above statements is/are correct? a) Only one b) Only two c) All three d) None Correct Solution: a) Only Statement 3 is correct. In an aquatic ecosystem, Grazing food chain is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain. Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web. Incorrect Solution: a) Only Statement 3 is correct. In an aquatic ecosystem, Grazing food chain is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain. Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web.

#### 2. Question

Consider the following statements.

• In a terrestrial ecosystem, a much larger fraction of energy flows through the grazing food chain than through the detritus food chain.

• In an aquatic ecosystem, detritus food chain is the major conduit for energy flow.

• Detritus food chain may be connected with the grazing food chain at some levels.

How many of the above statements is/are correct?

• a) Only one

• b) Only two

• c) All three

Solution: a)

Only Statement 3 is correct.

In an aquatic ecosystem, Grazing food chain is the major conduit for energy flow.

As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.

Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores.

These natural interconnection of food chains make it a food web.

Solution: a)

Only Statement 3 is correct.

In an aquatic ecosystem, Grazing food chain is the major conduit for energy flow.

As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.

These natural interconnection of food chains make it a food web.

• Question 3 of 5 3. Question Consider the following statements. Ecological Succession is the gradual process by which ecosystems change and develop over time. Hydrarch succession takes place in wetter areas and xerarch succession takes place in dry areas. The species that invade a bare area are called keystone species. How many of the above statements is/are correct? a) Only one b) Only two c) All three d) None Correct Solution: b) Statement 3 is incorrect. Ecological Succession is the gradual process by which ecosystems change and develop over time. Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch, respectively. Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions. As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions. Hence, both hydrarch and xerach successions lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet (hydric). The species that invade a bare area are called pioneer species. In primary succession on rocks these are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation. A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Incorrect Solution: b) Statement 3 is incorrect. Ecological Succession is the gradual process by which ecosystems change and develop over time. Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch, respectively. Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions. As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions. Hence, both hydrarch and xerach successions lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet (hydric). The species that invade a bare area are called pioneer species. In primary succession on rocks these are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation. A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.

#### 3. Question

Consider the following statements.

• Ecological Succession is the gradual process by which ecosystems change and develop over time.

• Hydrarch succession takes place in wetter areas and xerarch succession takes place in dry areas.

• The species that invade a bare area are called keystone species.

How many of the above statements is/are correct?

• a) Only one

• b) Only two

• c) All three

Solution: b)

Statement 3 is incorrect.

Ecological Succession is the gradual process by which ecosystems change and develop over time.

Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch, respectively.

Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions.

As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions. Hence, both hydrarch and xerach successions lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet (hydric).

The species that invade a bare area are called pioneer species. In primary succession on rocks these are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation.

A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.

Solution: b)

Statement 3 is incorrect.

Ecological Succession is the gradual process by which ecosystems change and develop over time.

Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch, respectively.

Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions.

• Question 4 of 5 4. Question Consider the following statements regarding Ecological Succession. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. Primary succession begins in areas where natural biotic communities have been destroyed. The entire sequence of communities that successively change in a given area are called sere(s). How many of the above statements is/are correct? a) Only one b) Only two c) All three d) None Correct Solution: b) Statement 2 is incorrect. ECOLOGICAL SUCCESSION An important characteristic of all communities is that their composition and structure constantly change in response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession some species colonies an area and their population become more numerous whereas populations of other species decline and even disappear. The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities. Succession is hence a process that starts in an area where no living organisms are there – these could be areas where no living organisms ever existed, say bare rock; or in areas that somehow, lost all the living organisms that existed there. The former is called primary succession, while the latter is termed secondary succession. • Secondary succession begins in areas where natural biotic communities have been destroyed such as in abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession. Incorrect Solution: b) Statement 2 is incorrect. ECOLOGICAL SUCCESSION An important characteristic of all communities is that their composition and structure constantly change in response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession some species colonies an area and their population become more numerous whereas populations of other species decline and even disappear. The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities. Succession is hence a process that starts in an area where no living organisms are there – these could be areas where no living organisms ever existed, say bare rock; or in areas that somehow, lost all the living organisms that existed there. The former is called primary succession, while the latter is termed secondary succession. • Secondary succession begins in areas where natural biotic communities have been destroyed such as in abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession.

#### 4. Question

Consider the following statements regarding Ecological Succession.

• The gradual and fairly predictable change in the species composition of a given area is called ecological succession.

• Primary succession begins in areas where natural biotic communities have been destroyed.

• The entire sequence of communities that successively change in a given area are called sere(s).

How many of the above statements is/are correct?

• a) Only one

• b) Only two

• c) All three

Solution: b)

Statement 2 is incorrect.

ECOLOGICAL SUCCESSION

• An important characteristic of all communities is that their composition and structure constantly change in response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession some species colonies an area and their population become more numerous whereas populations of other species decline and even disappear.

• The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities.

• Succession is hence a process that starts in an area where no living organisms are there – these could be areas where no living organisms ever existed, say bare rock; or in areas that somehow, lost all the living organisms that existed there. The former is called primary succession, while the latter is termed secondary succession.

• Secondary succession begins in areas where natural biotic communities have been destroyed such as in abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession.

Solution: b)

Statement 2 is incorrect.

ECOLOGICAL SUCCESSION

• The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities.

• Question 5 of 5 5. Question Molds derive energy through a) Photosynthesis b) Heterotrophy c) Sulphur synthesis d) Autotrophy Correct Solution: b) We can find molds on degraded bread. Like all fungi, molds derive energy not through photosynthesis but from the organic matter on which they live, utilizing heterotrophy. Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems. Incorrect Solution: b) We can find molds on degraded bread. Like all fungi, molds derive energy not through photosynthesis but from the organic matter on which they live, utilizing heterotrophy. Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems.

#### 5. Question

Molds derive energy through

• a) Photosynthesis

• b) Heterotrophy

• c) Sulphur synthesis

• d) Autotrophy

Solution: b)

We can find molds on degraded bread. Like all fungi, molds derive energy not through photosynthesis but from the organic matter on which they live, utilizing heterotrophy. Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems.

Solution: b)

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