Mix Examples- Ecosystem Questions in English

(A) Stability in an ecosystem is generally proportional to its complexity and biodiversity.
$A$ natural ecosystem like a river or a pond is more stable than an agricultural ecosystem.
Among the given options,a river ecosystem is typically considered more stable than a pond because it has a continuous flow of water,higher connectivity,and a more complex food web that allows it to recover from disturbances more effectively.
Agricultural ecosystems are artificial and highly unstable because they are maintained by human intervention and lack biodiversity.

(D) In a sedimentary cycle,the reservoir is the Earth's crust (rocks/soil).
Elements like Phosphorus $(P)$,Sulfur $(S)$,and Calcium $(Ca)$ have their primary reservoirs in the Earth's crust and are thus part of sedimentary cycles.
Hydrogen $(H)$,along with Carbon $(C)$,Nitrogen $(N)$,and Oxygen $(O)$,is part of a gaseous cycle,where the reservoir is the atmosphere or hydrosphere.
Therefore,$H$ cannot be included in a sedimentary cycle.

(C) To determine the trophic level of the rat,let's analyze the food chain described:
$1$. Grasshopper (Primary consumer) feeds on producers (plants).
$2$. Rat (Secondary consumer) feeds on the grasshopper.
$3$. Snake (Tertiary consumer) feeds on the rat.
$4$. Hawk (Quaternary consumer) feeds on the snake.
Since the rat consumes the grasshopper (which is a primary consumer),the rat occupies the position of a secondary consumer.

(B) Primary succession is a very slow process that begins on bare,lifeless areas (e.g.,bare rock) where no soil exists. It takes a long time for soil to form and for pioneer species to colonize.
Secondary succession occurs in areas where a previously existing community has been cleared by a disturbance (e.g.,fire,flood,or deforestation) but soil remains intact. Because soil and nutrients are already present,the process of recolonization is significantly faster than primary succession.
Evolution is a biological process occurring over geological time scales,which is much slower than ecological succession.
Therefore,secondary succession occurs at a faster rate compared to primary succession and evolution.

(C) Primary succession in freshwater environments is known as $Hydrosere$.
$Hydrosere$ involves a series of stages starting from open water and progressing through various plant communities (such as phytoplankton,submerged plants,floating plants,reed-swamp,marsh-meadow,and scrub) until it eventually reaches a climax forest community.
$Xerosere$ refers to succession in dry areas,$Lithosere$ refers to succession on bare rock,and $Halosere$ refers to succession in saline environments.

(C) Ecological succession is the gradual and predictable change in the species composition of a given area.
$1$. Succession occurring in water is called $Hydrarch$ succession.
$2$. Succession occurring on bare rocks is called $Litharch$ succession (a type of $Xerarch$ succession).
However,in the context of specific terminology for saline water and bare rocks:
- Succession in saline water is known as $Halarch$ succession.
- Succession on bare rocks is known as $Litharch$ succession.
Therefore,the correct answer is $Halarch$ and $Litharch$.

(D) Ecological succession is the gradual and predictable change in the species composition of a given area.
$1$. It involves the replacement of pioneer species (often short-lived) by more complex,long-lived species over time.
$2$. It is a process that occurs in parallel with the evolution of the ecosystem's structure and function.
$3$. The community undergoes continuous changes in species composition and structure until it reaches a stable,self-perpetuating state known as the climax community.
Therefore,all the given characteristics are observed in ecological succession.

(D) The functional aspects of an ecosystem are essential for its survival and maintenance. These include:
$1$. Productivity: The rate of biomass production by producers or consumers.
$2$. Decomposition: The breakdown of complex organic matter into simpler inorganic substances.
$3$. Energy flow: The unidirectional movement of energy through different trophic levels.
$4$. Nutrient cycling: The movement of nutrients through the biotic and abiotic components of the ecosystem.
Since options $A$,$B$,and $C$ are all fundamental functional components of an ecosystem,the correct answer is $D$.

(D) In an aquatic ecosystem,the food chain typically starts with phytoplankton (producers),followed by zooplankton (primary consumers),small fish (secondary consumers),and larger organisms. Whales,specifically baleen whales,feed on krill and small fish,while toothed whales (like orcas) feed on larger fish,seals,or other marine mammals. Because they occupy the highest position in the food chain and have no natural predators,they are classified as $Apex$ $predators$.

(D) An ecosystem is a dynamic system that functions through the following processes:
$1$. Constant interaction between biotic (living) and abiotic (non-living) components,which maintains the flow of energy and the cycling of nutrients.
$2$. Continuous consumption of energy stored by producers (green plants) by consumers (animals),which transfers energy from one trophic level to another.
$3$. Decomposition of dead organic matter by decomposers (bacteria and fungi),which releases nutrients back into the environment,thereby maintaining the balance of the ecosystem.
Therefore,all the given options are responsible for the dynamics of an ecosystem.

(D) The correct matching is as follows:
$(i)$ Sedimentary cycle: Sulphur $(S)$ is a classic example of a sedimentary nutrient cycle where the reservoir is the Earth's crust.
$(ii)$ Gaseous cycle: Carbon $(Q)$ is a gaseous nutrient cycle where the reservoir is the atmosphere.
$(iii)$ Herbivore: Herbivores are primary consumers $(P)$ that feed directly on plants.
$(iv)$ Top carnivore: Top carnivores are typically tertiary consumers $(R)$ in a food chain.
Therefore, the correct sequence is $(i-S, ii-Q, iii-P, iv-R)$.

(B) The correct matching is as follows:
$(i)$ Producers represent the $(R)$ Primary trophic level.
$(ii)$ Herbivores are the $(P)$ Primary consumers.
$(iii)$ Carnivores represent the $(S)$ Secondary productivity (as they consume primary consumers).
$(iv)$ Top carnivores represent the $(Q)$ Net primary productivity (in terms of energy flow and biomass accumulation).
Therefore,the correct sequence is $i-R, ii-P, iii-S, iv-Q$.

(A) The correct matching is as follows:
$(i)$ Ecosystem: It is a functional unit of nature where living organisms interact among themselves and with their physical environment,primarily characterized by nutrient cycling $(Q)$.
$(ii)$ Food chain: It represents the transfer of energy through various trophic levels. Deer $(S)$ is a primary consumer in a food chain.
$(iii)$ Birds: Many birds act as primary consumers $(R)$ in various ecosystems.
$(iv)$ Decomposers: Bacteria and Fungi $(P)$ are the primary decomposers that break down organic matter.
Therefore,the correct sequence is $(i-Q, ii-S, iii-R, iv-P)$.

(B) $1$. $A$ pond is a classic example of a natural ecosystem. This is a correct pair.
$2$. Gross primary productivity is the rate at which producers capture solar energy,not consumers. Therefore,'Consumer - Gross primary productivity' is a mismatched pair.
$3$. Sulfur cycle is primarily a sedimentary cycle,but it has a gaseous component (e.g.,$H_2S$,$SO_2$). However,in the context of standard biology questions,it is often contrasted with purely gaseous cycles like Carbon or Nitrogen. Given the options,option $B$ is the most clearly incorrect definition.
$4$. Producers are the organisms that are consumed by primary consumers. This represents a trophic relationship.

(B) $1$. $A$ hawk is a top carnivore in a food chain,which is correct.
$2$. $A$ pond is an aquatic ecosystem with high productivity,not the lowest. Deserts or deep oceans typically have the lowest productivity,making this the mismatched statement.
$3$. $A$ climax community is the final stable stage of succession that is well-adapted to the environment,which is correct.
$4$. Dry weight is defined as the total weight of an organism excluding water content. Therefore,water is not part of the dry weight,making this statement also factually incorrect in the context of biological definitions. However,in the context of typical multiple-choice questions on this topic,option $B$ is the most significant ecological mismatch regarding productivity levels.

(B) In an ecosystem, the primary source of energy is the $Sun$ (solar radiation), not decomposers. Decomposers are organisms that break down dead organic matter and recycle nutrients. Therefore, the pair $B$ is mismatched.

(A) Let's analyze each statement:
$(1)$ Secondary succession occurs in areas where living organisms previously existed. It is faster than primary succession and depends on the soil condition and water availability. This statement is correct.
$(2)$ Air,water,and soil (land) are indeed the fundamental abiotic components of an ecosystem. This statement is correct.
$(3)$ The functional aspects of an ecosystem include productivity,decomposition,energy flow,and nutrient cycling. Energy flow is unidirectional,while nutrient cycling is cyclic. This statement is correct.
$(4)$ The sun is the ultimate and primary source of energy for all ecosystems on Earth (except for deep-sea hydrothermal ecosystems). This statement is correct.
Since all $4$ statements are correct,the answer is $4$.

(D) Statement $(1)$ is correct: In a grassland ecosystem,the pyramid of number is upright,while in a tree ecosystem,it is inverted. Similarly,the pyramid of biomass is generally upright but inverted in aquatic ecosystems.
Statement $(2)$ is correct: Phosphorus and sulfur cycles are classified as sedimentary cycles because their main reservoirs are in the Earth's crust (rocks/soil).
Statement $(3)$ is correct: Oceans contain the largest reservoir of carbon on Earth,holding approximately $38,000$ billion tons of carbon.
Statement $(4)$ is correct: An ecosystem is defined as the structural and functional unit of nature where living organisms interact among themselves and with their physical environment.
Therefore,all statements are correct.

(A) Statement $(1)$ is correct: $NPP$ (Net Primary Productivity) is indeed $GPP$ (Gross Primary Productivity) minus $R$ (Respiration losses).
Statement $(2)$ is correct: Productivity is measured in terms of biomass $(g/m^2/yr)$ or energy $(kcal/m^2/yr)$. The units provided in the question are standard scientific representations for productivity.
Statement $(3)$ is incorrect: The total amount of energy produced by all producers is called Gross Primary Productivity $(GPP)$,not Net Primary Productivity $(NPP)$.
Statement $(4)$ is incorrect: The total annual net primary productivity of the whole biosphere is approximately $170$ billion tons (dry weight) of organic matter. Of this,the productivity of the oceans is only $55$ billion tons,but this refers to the total biomass production,not specifically the 'net primary productivity' in the context of the entire biosphere's comparison. However,more importantly,the statement defines it as 'net primary productivity' which is often confused with total production. In the context of $NCERT$,the total annual $NPP$ of the whole biosphere is $170$ billion tons,and the oceans contribute less than half of this.
Thus,only statements $(1)$ and $(2)$ are correct. The total number of correct statements is $2$.

(A) Statement $(1)$ is correct: Succession in dry areas is known as xerarch succession.
Statement $(2)$ is correct: The herb stage represents the initial colonization phase where plants can survive in open,exposed conditions.
Statement $(3)$ is incorrect: Ecological succession generally leads to an increase in biomass and net primary productivity as the community matures towards a climax state.
Statement $(4)$ is incorrect: Primary succession is a very slow process that typically takes hundreds to thousands of years,but it is not defined by a fixed average of $1000$ years for all cases.
Therefore,only statements $(1)$ and $(2)$ are correct.

(C) The provided figure shows a stage in hydrarch succession where the water level is very shallow and the area is dominated by plants like Typha,Phragmites,etc.,which have their roots in the mud but their shoots are exposed to the air. This is characteristic of the Reed-swamp stage. The Marsh-meadow stage follows this,where the area becomes swampy and is dominated by grasses and sedges. Since the image specifically depicts the dense growth of emergent vegetation typical of the Reed-swamp stage,option $C$ is the most accurate description.

(C) The provided figure illustrates the phosphorus cycle.
In the phosphorus cycle,the reservoir is the Earth's crust (rock minerals).
Phosphorus is released from rocks through weathering,enters the soil solution,is taken up by producers,moves to consumers,and returns to the soil through decomposition (detritus).
Since the reservoir is the Earth's crust and not the atmosphere,it is classified as a sedimentary cycle.

The plant $\text{Eichhornia crassipes}$, commonly known as $\text{Water hyacinth}$, was introduced in India because of its beautiful mauve-colored flowers and uniquely shaped leaves.
It is the world's most problematic aquatic weed, also known as the $\text{Terror of Bengal}$.
It grows abundantly in eutrophic water bodies and leads to an imbalance in the ecosystem by causing the death of fishes and other aquatic organisms due to oxygen depletion.

(C) Energy content does not remain trapped permanently in any organism. It is passed on to various trophic levels in the food chain.
According to the $10\%$ law proposed by Lindemann, only about $10\%$ of the energy is transferred to the next trophic level.
Therefore, the energy content gradually decreases from the first $(T_1)$ to the fourth $(T_4)$ trophic level.
Thus, the statement that energy content increases is incorrect.

(D) The phosphorus cycle is a sedimentary cycle.
Rocks are the major reservoir of phosphorus.
Unlike the carbon cycle,there is no respiratory release of phosphorus into the atmosphere because phosphorus does not have a significant gaseous phase in its cycle.
Therefore,the statement regarding the respiratory release of phosphorus is incorrect.

(A) The Nitrogen cycle is a gaseous nutrient cycle because its reservoir pool is the atmosphere. Sedimentary cycles,such as the Phosphorus or Sulphur cycle,have the lithosphere as their reservoir pool.
The pyramid of biomass in an aquatic ecosystem like the sea is inverted because the biomass of phytoplankton is much lower than that of the zooplankton and fishes that feed on them.
Therefore,statements $I$ and $IV$ are incorrect.

(C) The bulk of carbon fixation on Earth occurs in the oceans. This is primarily due to the vast surface area covered by oceans and the presence of a massive number of phytoplankton,which are the primary producers responsible for photosynthesis in marine ecosystems.

(C) Tropical rain forests receive high amounts of rainfall,which leads to intense leaching of nutrients from the soil.
Leaching is the process where water-soluble nutrients are washed away from the soil profile.
Due to this high rate of leaching,the soil in these regions typically has a low base content and is often acidic.
Therefore,the Assertion is correct because the soil has low base content,but the Reason is incorrect because these soils actually show high rates of percolation and leaching,not less.

(C) An estuary is a semi-enclosed coastal body of water where freshwater from rivers or streams meets and mixes with saltwater from the ocean.
It is considered one of the most productive ecosystems on Earth due to the high nutrient availability and the mixing of water bodies.
The Reason statement is incorrect because an estuary is a transition zone between two different ecosystems (freshwater and marine),not merely a transition zone between two populations of a single species.
Therefore,the Assertion is correct,but the Reason is incorrect.

(D) In the carbon cycle,which is a gaseous type of nutrient cycle,the atmosphere serves as the primary exchange pool or reservoir. Carbon dioxide $(CO_2)$ is exchanged between the atmosphere and living organisms through processes like photosynthesis and respiration.

(D) Secondary succession is an ecological succession that occurs in areas where natural biotic communities have been destroyed,such as in abandoned farm lands,burned or cut forests,or lands that have been flooded.
Since the soil is already present,it is faster than primary succession.
Primary succession begins on a bare rock or a completely sterile area where no soil exists.
Therefore,the statement that secondary succession begins on a bare rock is incorrect,as this is a characteristic of primary succession.

(C) Oak trees $(Quercus)$ are characteristic species of temperate deciduous forests. These forests are found in regions with moderate climates where trees shed their leaves annually during the cold season. The broad-leaved nature of oak is a typical adaptation to the temperate climate,allowing for efficient photosynthesis during the growing season.

(B) Insectivorous plants are autotrophs because they possess chlorophyll and perform photosynthesis to produce their own food. They do not consume insects as a primary energy source; instead,they capture insects to obtain essential nutrients like nitrogen $(N)$ and phosphorus $(P)$,which are often deficient in the soil where they grow. Therefore,they are classified as primary producers in an ecosystem.

(B) In an ecosystem,primary consumers are herbivores that feed directly on producers (green plants). Since a person eating vegetables consumes plant-based food directly,they function as a primary consumer.

(D) The release of $CO_{2}$ into the atmosphere occurs through various natural and anthropogenic processes.
Burning of wood,forest fires,volcanic activity,combustion of organic matter,and the burning of fossil fuels are all primary sources that contribute to the increase of $CO_{2}$ levels in the atmosphere.
Therefore,all the listed options ($I, II, III$,and $IV$) are correct sources.

(A) The correct order of succession in xerarch (xerosere) is as follows:
$(i)$ Lichen stage: Crustose lichens followed by foliose lichens.
$(ii)$ Moss stage: Bryophytes like $Tortula$ and $Polytrichum$.
$(iii)$ Annual herb stage: Grasses like $Cymbopogon$.
$(iv)$ Perennial herb and shrub stage: Plants like $Rubus$,$Capparis$,and $Zizyphus$.
$(v)$ Forest stage: The climax community consisting of trees and shrubs.
Therefore,the correct sequence is: Lichen $\rightarrow$ Moss stage $\rightarrow$ Annual herb stage $\rightarrow$ Perennial herb stage $\rightarrow$ Scrub stage $\rightarrow$ Forest.

(B) An ecosystem that is created and maintained by human beings is called an artificial or man-made ecosystem.
An aquarium is a classic example of a man-made ecosystem where humans control the biotic and abiotic components.
Herbarium and tissue culture are laboratory techniques,not ecosystems.
$A$ forest is a natural ecosystem.

(A) Approximately $71 \; \%$ of the global carbon is found dissolved in the oceans. This oceanic reservoir plays a crucial role in regulating the concentration of carbon dioxide in the atmosphere.

(B) The correct answer is Secondary consumer.
In a food chain,organisms are classified based on their trophic levels:
$1$. Producers (e.g.,Grass) synthesize their own food.
$2$. Primary consumers (e.g.,Grasshopper) feed directly on producers.
$3$. Secondary consumers (e.g.,Frog) feed on primary consumers (insects).
$4$. Tertiary consumers (e.g.,Snake) feed on secondary consumers.
$5$. Quaternary consumers (e.g.,Hawk) feed on tertiary consumers.
The food chain is represented as:
$Grass (Producer) \longrightarrow Grasshopper (Primary consumer) \longrightarrow Frog (Secondary consumer) \longrightarrow Snake (Tertiary consumer) \longrightarrow Hawk (Quaternary consumer)$

(D) The food chain is represented as follows:
Algae (Producer) $\rightarrow$ Bugs (Primary consumer) $\rightarrow$ Fish (Secondary consumer) $\rightarrow$ Bear (Tertiary consumer).
Since the bear occupies the fourth trophic level,it is a tertiary consumer.

(A) Climax community is the stable,self-perpetuating,and final biotic community that develops at the end of biotic succession and is in perfect harmony with the physical environment.
It is also termed as a climatic climax community.

(B) Organic remains,such as dead plant parts,animal remains,and excretions,are collectively known as detritus.
$A$ food chain that begins with detritus or dead organic matter is defined as a detritus food chain.
In this specific example,the chain starts with a dead animal,which serves as the primary source of energy for detritivores (blow fly maggots),followed by secondary consumers (common frog) and tertiary consumers (snake).
Therefore,this is a classic example of a detritus food chain.

(D) The phosphorus cycle is a sedimentary cycle,meaning it does not have a significant atmospheric component.
$I.$ The primary natural reservoirs of phosphorus are phosphate rocks and fossil bone deposits formed during past geological ages. This statement is correct.
$II.$ Weathering of these sedimentary rocks releases phosphate ions into the soil,making them available for uptake by plants. This statement is correct.
$III.$ Plants absorb inorganic phosphorus from the soil. Herbivores obtain this phosphorus by consuming plants,and carnivores obtain it by consuming herbivores. Thus,they obtain it directly or indirectly from plants. This statement is correct.
Since all three statements are true,the correct option is $D$.

(A) Ecological succession is a gradual and predictable change in the species composition of a given area.
It is a long-term process that occurs over a significant period of time,leading to the development of a stable climax community.
Primary succession occurs on previously sterile or bare areas,such as newly cooled lava,bare rock,or sand dunes,and takes a very long time to reach the climax stage.

(D) Statement $I$ is correct: $A$ food chain represents the transfer of energy from producers to top consumers through a series of organisms.
Statement $II$ is correct: By definition,a food chain is a single,linear pathway of energy flow in an ecosystem.
Statement $III$ is correct: Energy flow in an ecosystem is always unidirectional,starting from solar radiation $\rightarrow$ Producers $\rightarrow$ Herbivores $\rightarrow$ Carnivores. It cannot flow in the reverse direction.
Therefore,all three statements are correct.

(A) The correct sequence of stages in hydrarch succession (succession in water) is as follows:
$1.$ Phytoplankton stage $(IV)$
$2.$ Submerged plant stage $(III)$
$3.$ Submerged free-floating plant stage $(V)$
$4.$ Reed swamp stage $(II)$
$5.$ Marsh meadow stage $(I)$
Therefore,the correct sequence is $IV, III, V, II, I$.

(B) The statement in option $B$ is false. The energy content or biomass in a trophic level is determined by considering the total mass or energy of all individuals of all species present in that trophic level,not just individuals of a single species. The other statements are correct: $A$ defines standing crop,$C$ describes primary succession on barren rock/lava,and $D$ is true because secondary succession occurs on pre-existing soil,making it faster than primary succession.

(A) Statement $I$ is incorrect because the removal of tigers (top predators) would lead to an increase in the herbivore population,which would subsequently overgraze and decrease the vegetation,not increase it.
Statement $II$ is correct because carnivores act as a check on the population of herbivores (like deer). Removing them leads to an unchecked increase in the herbivore population.
Statement $III$ is correct because,according to the $10\; \%$ law of energy transfer,a significant amount of energy is lost as heat at each trophic level,limiting the number of levels to $3-4$.
Statement $IV$ is incorrect as food chains are typically restricted to $3-4$ levels and do not reach $8$ levels in standard ecosystems.
Therefore,statements $II$ and $III$ are correct.

(C) In the carbon cycle:
$A$ represents Respiration by plants,which releases $CO_2$ into the atmosphere.
$B$ represents Photosynthesis,where plants absorb $CO_2$ from the atmosphere.
$C$ represents Respiration by animals,which releases $CO_2$ into the atmosphere.
$D$ represents the Combustion of fossil fuels,which releases stored carbon as $CO_2$ into the atmosphere.
$E$ represents the Aquatic food chain,where carbon is transferred to marine organisms and eventually forms calcareous sediments.
$F$ represents fossil fuel reservoirs like Coal and oil.

(A) By analyzing the food web:
$1$. $A$ is a primary consumer that eats grass seeds and is eaten by a lion (e.g.,Deer).
$2$. $B$ is a primary consumer that eats grass seeds and is eaten by a snake (e.g.,Frog).
$3$. $C$ is a secondary consumer that eats rabbits and is eaten by a lion (e.g.,Foxes).
$4$. $D$ is a primary consumer that eats grass seeds and is eaten by hawks (e.g.,Sparrow).
Therefore,the correct identification is $A-$Deer,$B-$Frog,$C-$Foxes,$D-$Sparrow.