Food Chains and Webs Questions in English

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

(D) 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 $90\%$ of energy is lost as heat to the environment or used for metabolic activities by the organisms.
Due to this significant loss of energy at each step,there is very little energy left to support a higher trophic level after $3$ to $4$ transfers.
Therefore,the decrease in energy at higher trophic levels acts as a limiting factor for the length of a food chain.

(A) 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.
In the given food chain: Grass (Producer,$T_1$) $\rightarrow$ Grasshopper $(T_2)$ $\rightarrow$ Frog $(T_3)$ $\rightarrow$ Snake $(T_4)$ $\rightarrow$ Hawk $(T_5)$.
The fourth trophic level $(T_4)$ is the Snake.
Given: Energy at $T_4 = 5 \, kJ$.
To find the energy at the producer level $(T_1)$,we move backwards by multiplying by $10$ for each step:
Energy at $T_3 = 5 \times 10 = 50 \, kJ$.
Energy at $T_2 = 50 \times 10 = 500 \, kJ$.
Energy at $T_1$ (Producer) $= 500 \times 10 = 5000 \, kJ$.
Therefore,the energy available at the producer level is $5000 \, kJ$.

(B) 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 stored in their tissues,leading to higher concentrations as they move up the food chain from producers to top consumers.

(B) The statement is $False$.
Food chains vary significantly in length and complexity depending on the ecosystem.
Some food chains may consist of only two or three trophic levels (e.g., grass $\rightarrow$ deer $\rightarrow$ lion), while others can be much longer and more complex, involving many interconnected organisms in a food web.
Energy loss at each trophic level (as per the $10\%$ law) limits the length of food chains, but the specific structure and complexity are determined by the biodiversity and environmental conditions of the habitat.

(B) The flow of energy in an ecosystem is always unidirectional or one-way.
Energy enters the ecosystem from the sun and is captured by producers (plants) through photosynthesis.
It then moves from producers to consumers (herbivores,carnivores,etc.) and is eventually lost as heat at each trophic level.
Energy is never recycled back to the sun or to the previous trophic level,which is why the flow is unidirectional.

(B) The statement is False. In a food chain,energy flow is unidirectional,but organic matter (nutrients) follows a cyclic path. Organic matter is recycled through the ecosystem by decomposers,which break down dead organic material and return nutrients to the soil,where they are again taken up by producers.

(B) The statement is False. According to the $10 \%$ Law of energy transfer in an ecosystem,only about $10 \%$ of the energy available at one trophic level is transferred to the next trophic level as organic matter. The remaining $90 \%$ is lost to the environment as heat or used by the organism for its own metabolic processes.

(A) In an ecosystem, energy flows from producers to consumers. According to the $10\%$ law of energy transfer, only about $10\%$ of the energy is transferred from one trophic level to the next. Due to this significant loss of energy, the number of organisms that can be supported decreases as we move up the food chain. Therefore, the base of the pyramid (producers) typically contains the highest number of individuals, while the top trophic levels (apex predators) contain the fewest.

(A) According to the $10 \%$ Law proposed by Lindeman in $1942$,only about $10 \%$ of the energy entering a particular trophic level of organisms is stored as biomass and is available for transfer to the next higher trophic level.
Most of the energy is lost as heat to the environment during metabolic activities like respiration,movement,and digestion.
Therefore,the statement is True.

(B) In an ecosystem,consumers are classified based on their food source.
$1$. Primary consumers (First order consumers) are organisms that feed directly on producers (plants).
$2$. Since plants are producers,organisms that eat plants are known as herbivores.
$3$. Therefore,first order consumers are herbivores.

(C) Omnivores are organisms that have the ability to obtain energy and nutrients from materials originating from both plant and animal sources.
They are primary,secondary,or tertiary consumers in a food chain.
Examples include humans,bears,and crows.
Therefore,the correct option is $C$.

(B) In an ecosystem,the food chain follows a specific hierarchy:
$1$. Producers (Green plants) are at the first trophic level.
$2$. Primary consumers (Herbivores) feed directly on producers.
$3$. Secondary consumers (Carnivores) feed on primary consumers.
$4$. Tertiary or top carnivores feed on secondary consumers.
Therefore,carnivores that eat herbivores are classified as secondary consumers.

(B) In an ecosystem,organisms are classified based on their source of nutrition.
Producers (autotrophs) synthesize their own food using sunlight.
Herbivores are animals that feed directly on producers (plants).
Since they consume plants directly,they are classified as primary consumers.
Therefore,the correct option is $B$.

(A) In a food chain,the trophic levels are organized as follows:
$1$. The first trophic level consists of producers (autotrophs) like plants.
$2$. The second trophic level consists of primary consumers,which are herbivores (animals that eat plants).
$3$. The third trophic level consists of secondary consumers,which are carnivores.
Therefore,herbivores represent the second trophic level.

(C) In a food chain,the trophic levels are organized as follows:
$1$. $T_1$ (First Trophic Level): Producers (Plants).
$2$. $T_2$ (Second Trophic Level): Primary Consumers (Herbivores).
$3$. $T_3$ (Third Trophic Level): Secondary Consumers (Primary Carnivores).
$4$. $T_4$ (Fourth Trophic Level): Tertiary Consumers (Top Carnivores).
Therefore,primary carnivores occupy the third trophic level $(T_3)$.

(B) The first trophic level of any food chain consists of producers,which are organisms capable of producing their own food through photosynthesis.
In a terrestrial ecosystem,green plants or grass act as the primary producers.
Therefore,grass forms the first trophic level,followed by primary consumers (herbivores like deer) and secondary consumers (carnivores like lions).

$(A)$ top-level carnivore (or apex predator) is an organism at the end of a food chain that has no natural predators.
In the given options, the $Hawk$ occupies the highest trophic level as it feeds on primary and secondary consumers like snakes or small mammals, making it a top-level carnivore.
$Grasshopper$ is a primary consumer (herbivore), $Frog$ is a secondary consumer (carnivore), and $Deer$ is a primary consumer (herbivore).

(B) food chain represents the feeding relationship between different organisms in an ecosystem.
$1$. Energy flows through the food chain as organisms consume one another. This energy originates from the sun and is transferred from producers to consumers.
$2$. Nutrients (matter) are also cycled through the food chain as organic matter is passed from one trophic level to another and eventually decomposed back into the soil.
Therefore,both energy and nutrients are transferred through a food chain.

(D) detritus food chain $(DFC)$ begins with dead organic matter.
Decomposers and detritivores,such as fungi and bacteria,break down this dead organic matter to obtain energy.
Therefore,the chain starts with the decomposition of dead organic material by these organisms.

(B) 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 of energy transfer.
Because energy is not recycled back to the sun or to previous trophic levels, the flow of energy is strictly unidirectional.

(B) The correct matching is as follows:
$1.$ Producer: Algae $(c)$ are autotrophic organisms that produce food via photosynthesis.
$2.$ Herbivore: Rabbit $(a)$ is an animal that feeds primarily on plants.
$3.$ Carnivore: Snake $(d)$ is an animal that feeds primarily on other animals.
$4.$ Omnivore: Bear $(b)$ is an animal that consumes both plant and animal matter.
Therefore, the correct sequence is $(1-c), (2-a), (3-d), (4-b)$.