Food Chains and Webs Questions in English

(B) Green plants are the primary producers and the ultimate source of energy for all organisms in an ecosystem.
If all green plants disappear from the earth,the food chain will collapse.
Herbivores,which depend directly on plants for food,will die due to starvation.
Subsequently,carnivores,which depend on herbivores for food,will also die due to the lack of prey,leading to the extinction of life on earth.

(B) In a food chain,the trophic levels are organized as follows:
$1$. The first trophic level $(T_1)$ is occupied by producers (autotrophs) like plants.
$2$. The second trophic level $(T_2)$ is occupied by primary consumers (herbivores) that feed on producers.
$3$. The third trophic level $(T_3)$ is occupied by secondary consumers (carnivores) that feed on herbivores.
Therefore,the third trophic level is always occupied by carnivores.

(D) According to the $10\%$ Law of energy transfer in an ecosystem,only $10\%$ of the energy is transferred from one trophic level to the next,while $90\%$ is lost as heat.
Let the energy at the producer level $(T_1)$ be $E$.
$T_1$ (Grass) = $E$
$T_2$ (Grasshopper) = $E \times 0.1$
$T_3$ (Frog) = $E \times 0.1 \times 0.1 = E \times 0.01$
$T_4$ (Snake) = $E \times 0.1 \times 0.1 \times 0.1 = E \times 0.001$
Given that the energy at the fourth trophic level $(T_4)$ is $5 \, kJ$:
$E \times 0.001 = 5 \, kJ$
$E = 5 / 0.001 = 5000 \, kJ$
Therefore,the energy available at the producer level is $5000 \, kJ$.

(A) Biomagnification is the process where the concentration of non-biodegradable substances,such as pesticides (e.g.,$DDT$),increases at each successive trophic level in a food chain.
This occurs because these substances cannot be broken down by organisms and are passed on to the next level in higher concentrations.
Therefore,the correct answer is $A$.

(D) According to the $10\%$ Law proposed by Lindeman,only about $10\%$ of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
This energy is stored in the biomass of the organisms in the form of chemical energy (organic compounds like carbohydrates,proteins,and fats).
The remaining $90\%$ of the energy is lost to the environment as heat during metabolic processes or used for the organism's own life activities.

(A) $food \text{ } chain$ represents a single linear pathway of energy flow through an ecosystem.
However, in nature, organisms often feed on multiple sources from different trophic levels.
When these multiple food chains become interconnected, they form a complex network known as a $food \text{ } web$.
Since organisms at a higher trophic level feed on several types of organisms from lower levels, this interconnected feeding relationship is defined as a $food \text{ } web$.

(B) In an ecosystem, energy enters from the sun in the form of solar radiation. Producers (plants) capture this energy and convert it into chemical energy through photosynthesis. As energy moves from one trophic level to the next (e.g., from producers to primary consumers, then to secondary consumers), a significant portion of energy is lost as heat at each step, according to the $10\%$ law of energy transfer. Because energy cannot be recycled or reused by the producers once it is lost as heat, the flow of energy in an ecosystem is always unidirectional.

(A) The number of trophic levels in a food chain is limited by the $10\%$ law of energy transfer. According to this law,only about $10\%$ of the energy available at one trophic level is transferred to the next higher trophic level. The remaining energy is lost as heat during metabolic activities. As a result,after $3$ to $4$ trophic levels,the amount of energy remaining is insufficient to support the survival of organisms at the next level. Therefore,the decrease in energy at higher trophic levels acts as a limiting factor.

(A) According to the $10\%$ law of energy transfer in an ecosystem,only $10\%$ of the energy is transferred from one trophic level to the next higher trophic level.
Therefore,the maximum amount of energy is available at the first trophic level $(T_1)$,which consists of producers (plants).
As we move up the pyramid from $T_1$ to $T_4$,the amount of available energy decreases significantly at each successive level.

(B) In the given food chain,Grass $\to$ Deer $\to$ Tiger,the deer acts as the primary consumer and the sole source of food for the tiger.
If the deer is removed from this ecosystem,the tiger will lose its food source,leading to a decline in the tiger population due to starvation.
Simultaneously,since the deer (the primary consumer) is no longer present to graze on the grass,the grass population will increase due to the lack of predation/consumption.

(D) In an ecosystem,the energy flow follows a specific trophic level sequence.
$1$. Producers (plants) are at the first trophic level.
$2$. Primary consumers (herbivores like grasshoppers) feed on producers and occupy the second trophic level.
$3$. Secondary consumers (carnivores like frogs) feed on primary consumers and occupy the third trophic level.
When a grasshopper is eaten by a frog,the energy is transferred from the grasshopper (primary consumer) to the frog (secondary consumer).

(N/A) common food chain in a pond ecosystem is as follows:
Phytoplankton (producers) $\to $ Zooplankton (primary consumers) $\to $ Small fish (secondary consumers) $\to $ Large fish or birds (tertiary consumers).
This sequence represents the flow of energy from producers to various levels of consumers within the aquatic environment.

(N/A) The flow of energy in an ecosystem follows the path: $\text{Sun} \to \text{Producer} \to \text{Herbivore} \to \text{Carnivore}$.
This flow is considered unidirectional because energy is transferred from one trophic level to the next and cannot revert to the previous level.
Justification: According to the $10\%$ law of energy transfer,a significant amount of energy is lost as heat at each trophic level. Because the energy available at higher trophic levels is much lower than at lower levels,the energy cannot flow backward from a higher trophic level to a lower one.

(N/A)

Food chain	Food web
$(a)$ $A$ food chain is a linear sequence of organisms where nutrients and energy are transferred from one organism to another.	$(a)$ $A$ food web is a complex network of interconnected food chains that shows the multiple feeding relationships in an ecosystem.
$(b)$ In a food chain,an organism at a higher trophic level feeds on only one specific type of organism from the lower trophic level.	$(b)$ In a food web,an organism at a higher trophic level can feed on various types of organisms from different lower trophic levels.

(C) The food chain is represented as: Grass (Producer) $\rightarrow$ Insect (Primary Consumer) $\rightarrow$ Frog (Secondary Consumer) $\rightarrow$ Snake (Tertiary Consumer).
In this sequence,the grass occupies the $1^{\text{st}}$ trophic level.
The insect occupies the $2^{\text{nd}}$ trophic level.
The frog occupies the $3^{\text{rd}}$ trophic level.
The snake occupies the $4^{\text{th}}$ trophic level.
Therefore,the frog is at the $3^{\text{rd}}$ trophic level.

(B) According to the $10\%$ Law of energy transfer in an ecosystem,only $10\%$ of the energy available at one trophic level is transferred to the next higher trophic level.
Given that the energy at the $1^{\text{st}}$ trophic level (producers) is $10,000 \, J$.
Energy at the $2^{\text{nd}}$ trophic level = $10\%$ of $10,000 \, J$.
Calculation: $(10 / 100) \times 10,000 = 1,000 \, J$.
Therefore,the energy available to the organisms of the $2^{\text{nd}}$ trophic level is $1,000 \, J$.

(A) The first trophic level in a food chain is always a green plant because they are producers.
Only green plants possess chlorophyll,which allows them to capture radiant energy from the sun.
Through the process of photosynthesis,they convert this solar energy into chemical energy stored in the form of glucose (food).
Since all other organisms in a food chain depend on this stored chemical energy for their survival,plants must occupy the first trophic level.

(C) In a food chain,the first trophic level is occupied by producers (autotrophs) which synthesize their own food. Herbivores,which feed directly on these producers,always occupy the second trophic level. Carnivores occupy the third or higher trophic levels depending on the food chain structure.

(B) In an ecosystem,the food chain starts with producers (plants/grains) which occupy the $First$ trophic level.
Rats feed directly on grains,making them primary consumers.
Primary consumers occupy the $Second$ trophic level in a food chain.

(C) The phenomenon where harmful chemicals like pesticides accumulate in the tissues of organisms at higher trophic levels is known as biomagnification.
Once a pesticide enters a food chain, it is not broken down or excreted easily.
As a result, its concentration increases progressively at each successive trophic level, reaching the highest levels in the top carnivores.

(C) In a grassland ecosystem,herbivores act as the primary consumers that feed on producers (plants).
If all herbivores are removed,the carnivores (secondary and tertiary consumers) will lose their source of food and eventually die out.
Simultaneously,the producers will no longer be consumed,leading to an uncontrolled increase in their population,which disrupts the ecological balance.

(N/A) In an ecological pyramid,the trophic levels are arranged from the base to the apex.
$1$. The base level consists of Producers.
$2$. The level above the producers is $X$,which represents the Primary consumers (herbivores).
$3$. The level above the primary consumers is the Secondary consumers.
$4$. The top level $Z$ represents the Tertiary consumers (carnivores).
Therefore,$X$ is Primary consumers and $Z$ is Tertiary consumers.

(N/A) Trophic levels are the specific stages or steps in a food chain through which energy is transferred from one organism to another.
Example of a food chain:
Grass $\rightarrow$ Grasshopper $\rightarrow$ Frog $\rightarrow$ Snake $\rightarrow$ Peacock
The different trophic levels in this food chain are as follows:
$1$. Grass (Producer): First trophic level $(T_1)$
$2$. Grasshopper (Primary consumer): Second trophic level $(T_2)$
$3$. Frog (Secondary consumer): Third trophic level $(T_3)$
$4$. Snake (Tertiary consumer): Fourth trophic level $(T_4)$
$5$. Peacock (Quaternary consumer): Fifth trophic level $(T_5)$

(A) food-chain represents the sequence of organisms through which energy flows in an ecosystem,typically starting with a producer (plant) followed by consumers.
In the option $A$,Grass is a producer,Goat is a primary consumer (herbivore),and Human is a secondary or tertiary consumer (omnivore).
This sequence represents a valid flow of energy: $Grass \rightarrow Goat \rightarrow Human$.
Options $B$,$C$,and $D$ do not represent a logical feeding sequence where one organism consumes the other.

(B) If all the organisms or members of any trophic level are removed, the ecosystem will definitely be damaged.
For example, in the food chain: $Grass \rightarrow Grasshopper \rightarrow Frog \rightarrow Snake \rightarrow Peacock$.
If all grasshoppers are killed or removed, the frogs will not get food and will either die or migrate to another place in search of food.
If snakes are killed, the number of frogs will increase significantly, which will disturb the balance of the entire ecosystem.

(B) The impact of removing all organisms in a trophic level is indeed different for different trophic levels.
If producers are removed,the entire food chain collapses as there is no energy source.
If primary consumers are removed,producers overgrow and secondary consumers starve.
If top carnivores are removed,the population of lower trophic levels increases uncontrollably,leading to overgrazing and ecological imbalance.
Therefore,it is not possible to remove the organisms of any trophic level without causing significant damage to the ecosystem,as every level plays a crucial role in maintaining the balance of the food web.

(N/A) Biological magnification is the process of increasing the concentration of non-biodegradable toxic substances (such as pesticides or heavy metals) in the tissues of organisms at each successive trophic level of a food chain.
Yes,the levels of this magnification are different at different levels of the ecosystem.
The concentration of these chemicals increases as we move up the food chain.
Therefore,the maximum concentration is observed in the organisms at the highest trophic level (top carnivores),while the minimum concentration is found in the organisms at the lowest trophic level (producers).

(N/A) food chain represents the flow of energy from one trophic level to another. In a forest ecosystem,a typical food chain is:
Grass (Producer) $\rightarrow$ Deer (Primary Consumer) $\rightarrow$ Tiger (Secondary/Tertiary Consumer).

(A) $DDT$ is a non-biodegradable chemical substance that cannot be broken down by biological processes.
It accumulates at each successive trophic level in a food chain,a phenomenon known as biological magnification or biomagnification.
Since man occupies the highest trophic level in this food chain,the concentration of $DDT$ is found to be the maximum in man due to the cumulative effect of its intake from lower trophic levels.

(N/A) The scheme illustrates an aquatic food chain.
It demonstrates the $10 \%$ law of energy transfer,which states that only $10 \%$ of the energy available at one trophic level is transferred to the next higher trophic level.
In this example:
- Phytoplankton $(400 \text{ kJ})$ $\rightarrow$ Zooplankton $(40 \text{ kJ})$
- Zooplankton $(40 \text{ kJ})$ $\rightarrow$ Smaller fishes $(4 \text{ kJ})$
- Smaller fishes $(4 \text{ kJ})$ $\rightarrow$ Big fish $(0.4 \text{ kJ})$
Each step shows a $10 \%$ transfer of energy from the previous level.

(B) According to the $10 \%$ law of energy transfer in an ecosystem,only $10 \%$ of the energy available at one trophic level is transferred to the next higher trophic level.
Given: Energy at the producer level (Grass) = $4000 \ J$.
$1$. Energy available to the primary consumer (Grasshopper) = $10 \%$ of $4000 \ J = 400 \ J$.
$2$. Energy available to the secondary consumer (Frog) = $10 \%$ of $400 \ J = 40 \ J$.
$3$. Energy available to the tertiary consumer (Snake) = $10 \%$ of $40 \ J = 4 \ J$.
Therefore,the energy available to the frog is $40 \ J$ and to the snake is $4 \ J$.

(N/A) Biological magnification,also known as biomagnification,refers to the progressive increase in the concentration of non-biodegradable chemicals (such as pesticides or heavy metals) at each successive trophic level in a food chain. This occurs because these substances are not broken down by organisms and are passed on to the next level in higher concentrations.

(C) In the given food chain: $Wheat \rightarrow Rat \rightarrow Snake \rightarrow Peacock$.
If all the snakes are killed, the primary predator of the rats is removed, leading to an uncontrolled increase in the rat population.
Due to the lack of food (snakes), the population of peacocks will decrease significantly as they will starve.
Therefore, the removal of an intermediate trophic level disrupts the entire ecosystem balance.

(A) The trophic levels in an ecosystem are defined by the position an organism occupies in a food chain.
$(i)$ Second trophic level: These are primary consumers (herbivores) that feed directly on producers. Among the given organisms,the rabbit is a herbivore.
$(ii)$ Third trophic level: These are secondary consumers (carnivores) that feed on primary consumers. Among the given organisms,the frog and fox act as secondary consumers in various food chains.

(C) If deers are removed from the given food chain,the following consequences will occur:
$1$. Tigers will not survive because their primary source of food (deers) is removed.
$2$. The population of plants will increase significantly because the primary consumer (deers) that feeds on them is no longer present.

(N/A) food web depicts the complex feeding connections within an ecological community. It consists of many interconnected food chains. If any one organism becomes endangered or extinct,the organisms that depend on it for food have alternative options available for their survival. This redundancy prevents the collapse of the food chain and,in this way,a food web increases the overall stability of an ecosystem.

(N/A) food web is a complex network of interconnected food chains that shows the feeding relationships among various organisms in an ecosystem.
Significance for an ecosystem:
$1$. It maintains ecological balance by ensuring the interdependence of different organisms.
$2$. It provides stability to the ecosystem by offering alternative food sources for consumers if one population declines.
$3$. It helps in the flow of energy and the cycling of nutrients through different trophic levels.

(N/A) According to the $10 \%$ Law of energy transfer,only $10 \%$ of the energy available at one trophic level is transferred to the next higher trophic level.
$(b)$ Green plants (producers) capture approximately $1 \%$ of the solar energy falling on their leaves and convert it into food energy through the process of photosynthesis.

(C) $(i)$ The population of herbivores will increase beyond control because their natural predators are reduced.
$(ii)$ Autotrophs (producers) will disappear from the earth due to overgrazing by the unchecked herbivore population.
$(iii)$ Both these factors will disrupt food chains and food webs,ultimately leading to the collapse or severe imbalance of the ecosystem.

(N/A) $(i)$ The flow of energy in a food chain is unidirectional, moving from producers to primary consumers, then to secondary consumers, and finally to top carnivores.
$(ii)$ No, food and energy cannot move back to the previous trophic level. This is because energy is lost as heat at each trophic level during metabolic activities, as per the $10\%$ law of energy transfer. Once energy is transferred to a higher trophic level, it is no longer available to the previous level.

(N/A)

First Trophic Level	Third Trophic Level
$1$. The organisms of this trophic level are plants,also known as producers.	$1$. The organisms of this trophic level are animals,also known as secondary consumers.
$2$. They transform solar energy into chemical energy via photosynthesis. Example: Grass (all green plants).	$2$. They obtain chemical energy by consuming primary consumers (herbivores). Example: Carnivores (e.g.,Lion).

(B) According to the $10 \%$ Law of energy transfer in an ecosystem,only $10 \%$ of the energy available at one trophic level is transferred to the next trophic level.
The remaining $90 \%$ of the energy is lost to the environment.
This energy is primarily used by the organism for its own metabolic activities (such as respiration,movement,and growth) and is eventually released into the environment as heat.

(N/A)

Food chain	Food web
$1$. It is a straight sequence of organisms which depicts 'who eats whom'.	$1$. It is a complex network of many food chains existing in an ecosystem.
$2$. Food chain does not have any cross linkages.	$2$. Food web has many cross linkages.

(N/A) Differences between the Second Trophic Level and the Fourth Trophic Level:

Second Trophic Level	Fourth Trophic Level
$1$. The organisms of this trophic level are herbivores.	$1$. The organisms of this trophic level are carnivores.
$2$. They obtain more energy as they are closer to the producers. Example: $Deer, Rabbit, Grasshopper$.	$2$. They obtain less energy because they are further away from the producers. Example: $Snake, Peacock, Hawk$.

(N/A) If all lions are removed,the population of deer will increase significantly due to the lack of predators. This overpopulation will lead to overgrazing,causing a depletion of grass,which may eventually result in soil erosion.
$(b)$ If all deer are removed,the lions will lose their primary food source,leading to a decline in the lion population due to starvation. Conversely,the amount of grass will increase as there are no herbivores to consume it.

(N/A) According to the $10\%$ law of energy transfer, only about $10\%$ of the energy available at one trophic level is transferred to the next higher trophic level.
Because so little energy is available for the next level of consumers, food chains generally consist of only three or four steps.
The loss of energy at each step is so significant that very little usable energy remains after four trophic levels to support a fifth level.

(B) $food \text{ } chain$ is a linear sequence of organisms through which energy is transferred.
However, in nature, organisms rarely feed on only one type of organism.
Most organisms feed on multiple types of organisms from lower trophic levels, creating a complex, interconnected network of feeding relationships.
This interconnected network of multiple food chains is known as a $food \text{ } web$.

(C) In an ecosystem, energy enters from the sun and is captured by producers (plants) through photosynthesis.
As energy moves from one trophic level to the next (e.g., from producers to primary consumers, then to secondary consumers), a significant portion of energy is lost as heat at each step, according to the $10\%$ law.
Because energy cannot be recycled or reused by the producers once it is lost as heat, the flow of energy is strictly unidirectional, moving from the sun to producers and then to higher trophic levels.

(C) According to the $10 \%$ Law proposed by Lindeman,only about $10 \%$ of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
This energy is stored in the biomass of the organisms in the form of chemical energy (organic compounds like carbohydrates,proteins,and fats).
The remaining $90 \%$ of the energy is lost to the environment as heat during metabolic processes or used for the organism's own life activities.

(D) In the given food chain,Grass $\rightarrow$ Deer $\rightarrow$ Tiger,the deer acts as the primary consumer and the tiger acts as the secondary consumer.
If the deer is removed from this food chain,the tiger will lose its primary source of food,leading to a decrease in the tiger population due to starvation.
Simultaneously,since the deer (which consumes grass) is no longer present to graze,the grass population will increase due to the lack of predation.
Therefore,the correct consequence is that the population of tiger decreases and the population of grass increases.