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Biology
Ecosystem
85 questions from 36 papers, each with its answer.
- 85 questions
- 36 papers
- 2.41% of Biology
Productivity
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Given below are two statements:
Statement I: The primary source of energy in an ecosystem is solar energy.
Statement II: The rate of production of organic matter during photosynthesis in an ecosystem is called net primary productivity (NPP).
In the light of the above statements, choose the most appropriate answer from the options given below:Statement I is correct; Statement II is incorrect as total organic matter production is Gross Primary Productivity (GPP).
Solar energy is the ultimate energy driver for all ecosystems except deep-sea hydrothermal vents. The total rate of organic matter synthesis during photosynthesis is Gross Primary Productivity (GPP). Net primary productivity equals $NPP = GPP - R$. Hence Statement I is correct and Statement II is incorrect. -
In the equation GPP – R = NPP. GPP is Gross Primary Productivity, NPP is Net Primary Productivity. R here is
Gross primary productivity minus respiration losses (R) is net primary productivity.
Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP). -
The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis is called:The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis is defined as primary production.
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In the equation GPP - R = NPP. R represents:
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In relation to Gross primary productivity and Net primary productivity of an ecosystem, which one of the following statements is correct?Gross primary productivity (GPP) is the rate of production of organic matter during photosynthesis. Net primary productivity: NPP = GPP – R (respiration losses) So GPP is always more than NPP.
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In an ecosystem the rate of production of organic matter during photosynthesis is termedGross primary productivity is the rate of production of organic matter during photosynthesis per unit area per unit time.
Net primary productivity is GPP minus respiration losses; secondary productivity is the rate of formation of new organic matter by consumers. -
Secondary productivity is rate of formation of new organic matter by:Secondary productivity is the rate of formation of new organic matter by consumers.
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The rate of formation of new organic matter by rabbit in a grassland is calledPrimary productivity is the rate at which producers (green plants) form biomass by photosynthesis; gross and net primary productivity both refer to producers.
Secondary productivity is defined as the rate of formation of new organic matter by consumers.
A rabbit is a herbivore, i.e., a primary consumer feeding on the grass.
Therefore the organic matter it forms from the food it eats is secondary productivity.
Hence the answer is secondary productivity. -
The biomass available for consumption by the herbivores and the decomposers is calledGross primary productivity (GPP) is the rate of production of organic matter during photosynthesis.
A considerable amount of GPP is used by the plants themselves in respiration (R).
Net primary productivity: NPP = GPP − R
NPP is the biomass available for consumption by the heterotrophs (herbivores and decomposers).
Secondary productivity is the rate of formation of new organic matter by consumers, and standing crop is the mass of living material at a trophic level at a given time.
Hence the answer is net primary productivity. -
Which one of the following ecosystem types has the highest annual net primary productivity?Net primary productivity (NPP) is the gross primary productivity minus the respiration losses of the producers; it is the biomass available to the heterotrophs.
Productivity depends on sunlight, temperature, rainfall and the availability of nutrients.
Tropical rain forests are found in the equatorial regions, where the temperature is high throughout the year and the rainfall exceeds 140 cm.
The warm, humid climate supports dense, broad-leaved evergreen vegetation arranged in several well-defined layers (stratification), which photosynthesises all the year round.
As a result the tropical rain forest has the highest annual net primary productivity among terrestrial ecosystems.
Deciduous forests shed their leaves in one season and temperate forests have a short growing season, so their productivity is lower.
So the answer is tropical rain forest. -
Which of the following is expected to have the highest value (gm/m$^2$/yr) in a grassland ecosystem : -Gross primary production (GPP) is the total rate at which producers fix solar energy as organic matter by photosynthesis.
Net primary production (NPP) = GPP $-$ respiration losses of the plants. So NPP is always less than GPP.
Only a small part (about 10 percent) of the energy of one trophic level passes to the next. So secondary production (by herbivores) is much less than NPP, and tertiary production (by carnivores) is even less.
So the order is: GP $\gt$ NP $\gt$ secondary production $\gt$ tertiary production.
The highest value is that of gross production (GP).
Productivity Units
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Which of the following is the unit of productivity of an Ecosystem?
Productivity is expressed in energy per unit area per unit time, e.g., $(kcal\,m^{-2})\,yr^{-1}$.
While biomass/standing crop is measured in $g\,m^{-2}$ or $kcal\,m^{-2}$, productivity is a rate metric expressed per unit time: $g\,m^{-2}\,yr^{-1}$ or $(kcal\,m^{-2})\,yr^{-1}$.
Energy Flow and Thermodynamics
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Given below are two statements:
Statement I: In ecosystem, there is unidirectional flow of energy of sun from producers to consumers.
Statement II: Ecosystems are exempted from 2nd law of thermodynamics.
In the light of the above statements, choose the most appropriate answer from the options given below:Statement I is correct; Statement II is incorrect because ecosystems are not exempt from the Second Law of Thermodynamics.
Energy flow through an ecosystem is strictly unidirectional (sun \rightarrow producers \rightarrow primary consumers \rightarrow top predators), obeying the 1st law of thermodynamics. Ecosystems are NOT exempt from the 2nd law of thermodynamics; they require continuous energy input to resist entropy/disorder.
Decomposition
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Detritivores breakdown detritus into smaller particles. This process is called.
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Which one of the following processes during decomposition is correctly described?Detritivores such as earthworms break detritus into smaller particles; this is fragmentation.
In leaching, nutrients go down into the soil; humus is degraded very slowly; catabolism is carried out by bacterial and fungal enzymes. -
The breakdown of detritus into smaller particles by earthworm is a process calledThe important steps of decomposition are fragmentation, leaching, catabolism, humification and mineralisation.
Detritivores such as earthworms break down detritus into smaller particles; this process is called fragmentation.
Catabolism is the degradation of detritus into simpler inorganic substances by bacterial and fungal enzymes.
Humification is the accumulation of dark, amorphous humus, and mineralisation is the release of inorganic nutrients from humus by microbes.
Hence the breakdown of detritus into smaller particles by earthworms is fragmentation. -
Plant decomposers are : -Decomposers break down dead plant and animal remains into simple inorganic substances, which are returned to the soil.
The main decomposers are bacteria (kingdom Monera) and fungi (kingdom Fungi). They secrete enzymes onto the dead matter and absorb the products.
So decomposers belong to Monera and Fungi.
Nutrient Cycling
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The amount of nutrients, such as carbon, nitrogen, phosphorus and calcium present in the soil at any given time is referred as:
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In which of the following both pairs have correct combination:
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Which one of the following is not a gaseous biogeochemical cycle in ecosystem?Nutrient cycles are of two types: gaseous (reservoir in the atmosphere) and sedimentary (reservoir in the earth's crust).
The phosphorus cycle is sedimentary; its reservoir is rock.
The carbon and nitrogen cycles are gaseous.
Ecological Pyramids
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Which of the following statements is not correct?
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Which of the following ecological pyramids is generally inverted?
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What type of ecological pyramid would be obtained with the following data? Secondary consumer : 120 g, Primary consumer : 60 g, Primary producer : 10 g
Biomass increasing up the trophic levels gives an inverted pyramid.
The given data depict an inverted pyramid of biomass, usually found in aquatic ecosystems. A pyramid of energy is always upright. Upright pyramids of biomass and numbers are not possible, as the data show the primary producer is less than the primary consumer, which is less than the secondary consumer. -
The upright pyramid of number is absent inIn grassland, pond and lake ecosystems the producers are the most numerous, so the pyramid of numbers is upright.
In a forest (tree) ecosystem a few large trees support many insects and birds, so the pyramid of numbers is not upright. -
Which one of the following statements for pyramid of energy is incorrect, whereas the remaining three are correct?The pyramid of energy shows the amount of energy present at each trophic level in a given time (per unit area per year).
When energy flows from one trophic level to the next, some energy is always lost as heat at each step; only about 10% is transferred (10 per cent law).
So the energy at a lower trophic level is always more than that at the higher level: the base (producers) is broad and the pyramid is upright.
The pyramid of energy can never be inverted (unlike the pyramid of biomass in the sea or the pyramid of numbers on a tree).
Hence the incorrect statement is that it is inverted in shape. -
Which one of the following is not used for construction of ecological pyramids ?An ecological pyramid is a graphic representation of the relationship between the successive trophic levels of an ecosystem.
There are three types of ecological pyramids.
The pyramid of numbers is based on the number of individuals at each trophic level.
The pyramid of biomass is based on the biomass at each trophic level, which is measured as dry weight.
The pyramid of energy is based on the rate of energy flow (energy per unit area per unit time) through each trophic level.
Fresh weight is not used, because the water content of organisms varies greatly from one organism to another and with conditions, so it does not give a true measure of the organic matter present.
So the one not used for the construction of ecological pyramids is fresh weight.
Ecosystem – Trophic Levels and Food Chains
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Match the trophic levels with their correct species examples in grassland ecosystem.
Pick the matching item from Column II for each row.
Column I
- A. Fourth trophic level
- B. Second trophic level
- C. First trophic level
- D. Third trophic level
Column II
- I. Crow
- II. Vulture
- III. Rabbit
- IV. Grass
Correct answer: A → II, B → III, C → IV, D → I
Ecological succession
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All successions irrespective of the habitat proceed to which type of climax community?Both hydrarch and xerarch successions lead to medium water conditions, so all successions irrespective of the habitat proceed to a mesic climax community.
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Secondary succession takes place on/inPrimary succession begins where no living organisms ever existed: bare rock, newly created pond, newly cooled lava.
Secondary succession begins where natural communities have been destroyed, such as a degraded forest. -
During ecological succession:
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Both hydrarch and xerarch successions lead toHydrarch succession takes place in wet areas, and the successional series progresses from hydric to mesic conditions.
Xerarch succession takes place in dry areas, and the series progresses from xeric to mesic conditions.
Thus both hydrarch and xerarch successions lead to medium water conditions (mesic), neither too dry (xeric) nor too wet (hydric).
The climax community in both cases is a mesic forest.
Hence both lead to medium water conditions.
Hydrarch succession
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The pioneer species in a hydrarch succession are:In hydrarch succession (in water bodies), the pioneer species are phytoplankton, i.e. minute microscopic autotrophic organisms such as diatoms and unicellular algae.
Ecological succession - pioneer species
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The species that come to appear in bare area are calledThe first biotic species that invade a bare area are called pioneer species, e.g. lichens on rocks, phytoplankton in ponds.
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Which of the following would appear as the pioneer organisms on bare rocks?
Lichens colonise bare rock first in xerarch succession.
Lichens are symbiotic associations of algae (phycobiont) and fungi (mycobiont). They release acids that dissolve rock particles, causing weathering and soil formation, so lichens are pioneers on bare rock.
Food chains - trophic levels
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Which of the following are primary consumers in a food chain?Reference: NCERT Class XII, page 210.
Energy flow and ecological pyramids
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Which of the following statements are correct? (a) Energy flow from producers to consumers is unidirectional (b) Energy pyramid can never be inverted (c) Transfer of energy follows the 1% law Choose the correct answer from the options given below:Reference: NCERT Class XII, page 213.
Productivity and standing crop
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Which ecosystem has the maximum biomass?
Forests hold the largest standing biomass.
Highly productive ecosystems include tropical rain forests, coral reefs, estuaries and sugarcane fields; forest ecosystems have the maximum biomass.
Ecosystem structure – stratification
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Presence of plants arranged into well defined vertical layers depending on their height can be seen best in:
Tropical rain forests show the most distinct stratification.
Tropical rain forests have five vertical strata based on plant height, i.e. ground vegetation, shrubs, short canopy trees, tall canopy trees and tall emergent trees.
Man-made ecosystems – cropland
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Which one of the following is a characteristic feature of cropland ecosystem?
Monocultures have minimal genetic diversity.
The cropland ecosystem is one of the largest anthropogenic ecosystems, with less (least) genetic diversity and higher productivity.
Ecosystem – history of the term
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The term ecosystem was coined by
Tansley coined 'ecosystem' (1935).
The term ecosystem was coined by A.G. Tansley. He proposed that biotic and abiotic factors are components of nature inter-related to each other.
Producers – chemosynthetic bacteria
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The primary producers of the deep-sea hydrothermal vent ecosystem are:
Ecosystem structure
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Vertical distribution of different species occupying different levels in a biotic community is known asStratification is the vertical arrangement of the members of a community at different levels.
Productivity and biomass
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The mass of living material at a trophic level at a particular time is calledStanding crop is the mass of living material at a trophic level at a particular time.
Standing state is the amount of inorganic nutrients present at a given time; GPP and NPP are rates of production of organic matter.
Phosphorus cycle
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Natural reservoir of phosphorus is:The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphates.
Energy flow
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If 20 J of energy is trapped at producer level, then how much energy will be available to peacock as food in the following chain? plant → mice → snake → peacock:Only 10 per cent of energy passes to the next trophic level.
Plant 20 J → mice 2 J → snake 0.2 J → peacock 0.02 J -
Of the total incident solar radiation the proportion of PAR isPAR is photosynthetically active radiation, the part of sunlight (400–700 nm) that plants can use for photosynthesis.
NCERT states that of the incident solar radiation less than 50 per cent is PAR.
Plants capture only 2–10 per cent of this PAR, and this small amount of energy sustains the entire living world.
The remaining part of the incident radiation is ultraviolet and infra-red, which is not used in photosynthesis.
Hence the proportion of PAR is less than 50%. -
Mass of living matter at a trophic level in an area at any time is calledEach trophic level has a certain mass of living material at a particular time, called the standing crop.
The standing crop is measured as the biomass of living organisms or as their number in a unit area.
Standing state is the amount of nutrients (such as carbon, nitrogen, phosphorus, calcium) present in the soil at any given time.
Detritus is dead plant and animal remains, and humus is the dark amorphous substance formed by its partial decomposition.
Hence the mass of living matter at a trophic level is called the standing crop.
Food chain
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Identify the possible link "A" in the following food chain: Plant → insect → frog → "A" → EagleA must be a carnivore that eats frogs and is itself eaten by eagles.
A cobra feeds on frogs and is preyed upon by eagles.
Parrot and rabbit are herbivores, and a wolf does not fit between frog and eagle.
Ecosystem structure and function
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Which one of the following is not a functional unit of an ecosystem?The functional aspects of an ecosystem are productivity, decomposition, energy flow and nutrient cycling.
Stratification (vertical distribution of species at different levels) is a structural feature.
Food chain and trophic levels
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Which one of the following animals may occupy more than one trophic level in the same ecosystem at the same time?A trophic level is a functional level, not a species; a given species may occupy more than one trophic level in the same ecosystem at the same time.
NCERT gives the sparrow as the example: it is a primary consumer when it eats seeds, fruits and peas, and a secondary consumer when it eats insects and worms.
A goat is only a herbivore (primary consumer).
A frog feeds on insects and a lion on herbivores, so each is a carnivore at essentially one level.
Hence the sparrow may occupy more than one trophic level.
Structure of ecosystem
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Which one of the following is one of the characteristics of a biological community?A population has attributes that an individual does not have: birth rate (natality), death rate (mortality), sex ratio and age distribution.
A biological community is an assemblage of populations of different species; its characteristics include species composition, dominance and stratification.
Stratification is the vertical distribution of different species occupying different levels, e.g., trees in the top layer, shrubs in the second and herbs and grasses in the bottom layer of a forest.
Hence stratification is a characteristic of a biological community.
Trophic levels
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Bamboo plant is growing in a far forest then what will be the trophic level of it : -Green plants are producers: they make their own food by photosynthesis.
Producers always occupy the first trophic level ($T_1$) of any food chain, wherever they grow.
Herbivores are at $T_2$, and carnivores at $T_3$ and $T_4$.
So the bamboo plant is at the first trophic level ($T_1$).
Carbon Cycle
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About 70% of total global carbon is found in:Carbon constitutes about 49 percent of the dry weight of organisms and is next only to water.
Of the total quantity of global carbon, about 71 percent is found dissolved in the oceans.
This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere.
The atmosphere contains only about 1 percent of the total global carbon.
Forests, grasslands and agroecosystems hold carbon in their biomass and soil, but their share is far smaller than that of the oceans.
So about 70 percent of the total global carbon is found in the oceans.
Water Resources
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More than 70% of world's fresh water is contained in -Only about 2.5 to 3 percent of the water on earth is fresh water; the rest is salt water in the oceans.
Most of this fresh water is not in liquid form: about 70 percent of it is locked up as ice in the polar ice caps and ice sheets (Antarctica and Greenland).
Most of the remainder is ground water, and only a very small fraction is present in lakes and rivers.
Antarctica and Greenland are both parts of the polar ice, so the complete answer is polar ice.
So more than 70 percent of the world's fresh water is contained in polar ice.
That is every question in Ecosystem for this filter.
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