MCQ (Practice) - Ecosystem (Level 1) - Class 12 MCQ

Explanation:
Pyramid of numbers:
The pyramid of numbers represents the number of organisms at each trophic level in an ecosystem. It shows the flow of energy and biomass through different levels of the food chain. In a typical pyramid of numbers, the number of organisms decreases as we move up the trophic levels.
Inverted pyramid of numbers:
An inverted pyramid of numbers is a situation where the number of organisms at higher trophic levels is greater than the number of organisms at lower trophic levels. This is usually observed in parasitic food chains where the number of parasites is higher than the number of hosts.
Examples:
A: Parasitic food chain
- In a parasitic food chain, the number of parasites is usually higher than the number of hosts.
- This is because parasites rely on the host organisms for their survival and reproduction.
- The hosts may support a large number of parasites, resulting in an inverted pyramid of numbers.
B: Grassland ecosystem
- In a grassland ecosystem, the pyramid of numbers is typically upright, with a large number of grasses at the base, followed by a smaller number of herbivores and an even smaller number of carnivores.
- The number of organisms decreases as we move up the trophic levels, following the typical pyramid shape.
C: Forest ecosystem
- Similar to a grassland ecosystem, a forest ecosystem also follows a typical pyramid of numbers.
- The number of trees is usually the highest, followed by a smaller number of herbivores and an even smaller number of carnivores.
D: Lake ecosystem
- In a lake ecosystem, the pyramid of numbers is also typically upright, with a large number of primary producers (algae, phytoplankton) at the base, followed by a smaller number of herbivores (zooplankton) and an even smaller number of carnivores (fish).
In conclusion:
The correct answer is A: Parasitic food chain. In a parasitic food chain, the pyramid of numbers is inverted, with a higher number of parasites compared to the number of hosts. This is because parasites rely on the host organisms for their survival and reproduction.

The type of food chain in which organic matter decomposed is converted into energy-rich compounds is called a Detritus food chain.
Explanation:
The Detritus food chain is a type of food chain that begins with dead organic matter or detritus. It involves the decomposition of dead plants, animals, and other organic material by decomposers such as bacteria and fungi. These decomposers break down the organic matter into simpler compounds through the process of decomposition.
Here is a detailed explanation of the Detritus food chain:
1. Decomposers: Decomposers play a vital role in the Detritus food chain. They are responsible for breaking down the dead organic matter into smaller, simpler compounds. Decomposers include bacteria, fungi, and other microorganisms.
2. Detritus: Detritus refers to the dead organic matter, such as dead plants, animals, leaves, and other organic debris. It serves as the primary source of energy for the Detritus food chain.
3. Decomposition: The decomposers break down the detritus through the process of decomposition. They release enzymes that break down complex organic compounds into simpler forms.
4. Energy-rich compounds: As the decomposition process occurs, energy-rich compounds such as carbohydrates, proteins, and lipids are produced. These compounds contain stored energy that can be utilized by other organisms in the food chain.
5. Detritivores: Detritivores are organisms that feed on the decomposed organic matter. They consume the energy-rich compounds produced during decomposition. Detritivores can include organisms such as earthworms, millipedes, and some insects.
6. Higher trophic levels: The energy from the detritivores is then transferred to higher trophic levels in the food chain. Predators and scavengers that feed on detritivores obtain energy from the detritus indirectly.
7. Nutrient recycling: The Detritus food chain plays a crucial role in nutrient recycling. The decomposition of organic matter releases essential nutrients back into the ecosystem, which can be utilized by plants and other organisms.
In summary, the Detritus food chain is a process of converting decomposed organic matter into energy-rich compounds through the actions of decomposers. It is an important pathway for energy flow and nutrient recycling in ecosystems.

Eltonian pyramids:
- Eltonian pyramids are a graphical representation of ecological trophic relationships.
- They show the flow of energy or biomass through different levels of a food chain or food web.
- Each level in the pyramid represents a different trophic level, with primary producers at the base and top predators at the apex.
Upright pyramid:
- An upright pyramid means that the energy or biomass decreases at each successive trophic level.
- This is because energy is lost as it is transferred from one trophic level to another, through processes such as respiration, heat loss, and incomplete digestion.
- Biomass also decreases because less energy is available to support the growth and reproduction of organisms at higher trophic levels.
Options:
A. Biomass:
- The biomass pyramid represents the total amount of living or organic matter at each trophic level.
- An upright biomass pyramid indicates a decrease in biomass from lower to higher trophic levels.
- Therefore, an upright biomass pyramid is consistent with the concept of energy flow in an Eltonian pyramid.
B. Energy:
- The energy pyramid represents the amount of energy available at each trophic level.
- An upright energy pyramid indicates a decrease in energy from lower to higher trophic levels.
- Therefore, an upright energy pyramid is consistent with the concept of energy flow in an Eltonian pyramid.
C. Number:
- The number pyramid represents the number of individuals at each trophic level.
- An upright number pyramid indicates a decrease in the number of individuals from lower to higher trophic levels.
- Therefore, an upright number pyramid is consistent with the concept of energy flow in an Eltonian pyramid.
Conclusion:
- Since all three options (biomass, energy, and number) require an upright pyramid to represent the flow of energy in an Eltonian pyramid, the correct answer is D: All of these.

Introduction:
The word 'ecosystem' is a term widely used in the field of ecology and environmental science. It refers to a complex network of interactions between living organisms and their environment. The term was coined by a prominent British ecologist named Arthur Tansley in the year 1935.
Detailed Explanation:
Arthur Tansley, a British ecologist, introduced the term 'ecosystem' in his publication titled "The Use and Abuse of Vegetational Concepts and Terms" in 1935. This publication played a crucial role in establishing the concept of ecosystems as a fundamental unit of ecological study.
Tansley's definition of an ecosystem emphasized the interconnectedness and interdependence of organisms and their environment. He described an ecosystem as a system composed of both living (biotic) and non-living (abiotic) components, which interact with each other to form a dynamic ecological community.
The term 'ecosystem' gained widespread recognition and acceptance within the scientific community. It provided a conceptual framework for studying the intricate relationships and processes occurring in natural environments. Today, the concept of ecosystems is fundamental to our understanding of ecology, conservation, and sustainable development.
Conclusion:
In conclusion, the word 'ecosystem' was coined by Arthur Tansley, a British ecologist, in 1935. His pioneering work in defining and conceptualizing ecosystems has greatly contributed to our understanding of the complex interactions between organisms and their environment. The term continues to be widely used and forms the basis of ecological research and conservation efforts.

Biotic components include:
- Producers: Producers are organisms that can convert sunlight into energy through the process of photosynthesis. They include plants, algae, and some bacteria. Producers are the foundation of the food chain as they provide energy for other organisms.
- Consumers: Consumers are organisms that obtain their energy by consuming other organisms. They can be further classified into different types based on their feeding habits:
- Herbivores: Herbivores are primary consumers that feed on plants and algae.
- Carnivores: Carnivores are secondary and tertiary consumers that primarily feed on other animals.
- Omnivores: Omnivores are consumers that eat both plants and animals.
- Decomposers: Decomposers are organisms that break down dead organic matter and release nutrients back into the environment. They include bacteria, fungi, and some insects. Decomposers play a vital role in the recycling of nutrients and the decomposition of organic waste.
Therefore, the correct answer is D: producers, consumers, and decomposers. Biotic components encompass all these organisms, which interact with each other in ecosystems and contribute to the overall functioning and balance of the environment.

The last organisms of the food chain are generally:
Answer: D. Top carnivores

Explanation:
The food chain is a hierarchical series of organisms in which each organism depends on the one below it for food. The last organisms in the food chain are known as the top carnivores. These organisms occupy the highest trophic level and are often referred to as apex predators. Here is a detailed explanation of each option:
A. Photosynthetic plants:
- Photosynthetic plants are at the beginning of the food chain as they produce their own food through photosynthesis.
- They are primary producers and form the base of the food chain.
- They are not the last organisms in the food chain.
B. Herbivores:
- Herbivores are animals that feed on plants.
- They occupy a higher trophic level than photosynthetic plants but are not at the top of the food chain.
- They are preyed upon by carnivores.
C. Carnivores:
- Carnivores are animals that primarily feed on other animals.
- They occupy a higher trophic level than herbivores but are not at the top of the food chain.
- They are preyed upon by top carnivores.
D. Top carnivores:
- Top carnivores are the last organisms in the food chain.
- They occupy the highest trophic level and have no natural predators.
- They are often apex predators and play a crucial role in regulating the populations of other organisms in the ecosystem.
In conclusion, the last organisms of the food chain are generally the top carnivores, which occupy the highest trophic level and have no natural predators.

Population of Primary Producers vs. Primary Consumers in an Ecosystem

• Statement: The population of primary producers is larger than primary consumers.

When considering the population dynamics of an ecosystem, it is important to understand the roles and relationships between different organisms. In this case, we are comparing the population sizes of primary producers and primary consumers. Here's a detailed explanation:

• Primary Producers:




• Primary producers, such as green plants and algae, are organisms that can convert sunlight into energy through the process of photosynthesis.


• They form the base of the food chain and provide food and energy for other organisms.


• Examples: Grass, trees, phytoplankton.





• Primary Consumers:




• Primary consumers, also known as herbivores, are organisms that feed directly on primary producers.


• They obtain energy by consuming plants or algae.


• Examples: Deer, rabbits, cows.

Now, let's analyze the given statements:

• Statement A: Primary producers have a larger population than primary consumers.




• This statement is correct because primary producers are the foundation of the food chain and are generally more abundant in an ecosystem.


• They can reproduce rapidly, and their population size is often much larger compared to primary consumers.





• Statement B: The population of secondary consumers is the largest.




• This statement is incorrect because secondary consumers, such as carnivores that feed on herbivores, have a smaller population compared to primary consumers.


• As we move up the food chain, the population size tends to decrease due to the energy loss and inefficiency of energy transfer between trophic levels.





• Statement C: Primary consumers outnumber primary producers.




• This statement is incorrect because primary producers, being the primary source of food and energy, generally have a larger population compared to primary consumers.


• Primary consumers depend on primary producers for their survival.





• Statement D: Primary consumers are least dependent upon primary producers.




• This statement is incorrect because primary consumers rely entirely on primary producers for their food and energy.


• Primary consumers cannot survive without the presence of primary producers in the ecosystem.

Therefore, the correct answer is Statement A: The population of primary producers is larger than primary consumers in an ecosystem.

An aquatic ecosystem consists of:
- Biotic factors: Living organisms that are a part of the ecosystem, including plants, animals, and microorganisms.
- Abiotic factors: Non-living components of the ecosystem that influence the biotic factors, such as water, temperature, sunlight, pH levels, and nutrient availability.
- Producers: Organisms that can produce their own food through photosynthesis, such as algae and aquatic plants.
- Consumers: Organisms that obtain their energy by consuming other organisms. They can be further classified into primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (top carnivores).
- Decomposers: Organisms that break down dead organic matter and recycle nutrients back into the ecosystem, such as bacteria and fungi.
- Physical features: This includes the physical characteristics of the aquatic environment, such as the depth, flow rate, and clarity of water, as well as the presence of rocks, sand, and other substrates.
In summary, an aquatic ecosystem consists of both biotic and abiotic factors, including producers, consumers, decomposers, and physical features of the environment. These components interact with each other to form a complex and interconnected web of life within the aquatic ecosystem.

To determine the best arrangement of the energy system consisting of hawks, snakes, mice, and grasses, we need to consider the flow of energy through the different organisms in the food chain.
The correct arrangement is A: Grass → Mice → Snake → Hawks. Here's why:
1. Grass: Grass is a producer that converts sunlight into energy through photosynthesis. It is the primary source of energy in the ecosystem.
2. Mice: Mice are herbivores that feed on grass. They obtain energy by consuming plants.
3. Snake: Snakes are carnivores that prey on mice. They obtain energy by consuming other animals.
4. Hawks: Hawks are apex predators that feed on snakes. They obtain energy by consuming other animals.
This arrangement follows the natural flow of energy in an ecosystem, where energy is transferred from one organism to another. Here, the grasses provide energy to the mice, which in turn provide energy to the snakes, and finally, the snakes provide energy to the hawks.
Key Points:
- The best arrangement is Grass → Mice → Snake → Hawks.
- The flow of energy in the food chain is from producers (grass) to primary consumers (mice) to secondary consumers (snakes) to tertiary consumers (hawks).
- This arrangement follows the natural flow of energy in an ecosystem.
- Each organism in the food chain obtains energy by consuming the organism before it.

Chain of Consumption:
- Hydra eats water fleas
- Small fish eat Hydra
- Big fish eat small fish
Classification of Organisms:
- Phytoplankton: Producers (they produce their own food through photosynthesis)
- Water fleas: Primary consumers (they eat the producers, phytoplankton)
- Hydra: Secondary consumers (they eat the primary consumers, water fleas)
- Small fish: Tertiary consumers (they eat the secondary consumers, Hydra)
- Big fish: Top consumer (they eat the tertiary consumers, small fish)
Explanation:
- Water fleas are classified as primary consumers because they directly consume the producers, phytoplankton.
- Hydra, being a level above the water fleas, is classified as a secondary consumer as it feeds on the primary consumers, water fleas.
- Small fish, being a level above Hydra, are classified as tertiary consumers as they consume the secondary consumers, Hydra.
- Finally, big fish, being at the top of the chain, are considered the top consumer as they feed on the tertiary consumers, small fish.
Therefore, water fleas are correctly classified as primary consumers in this chain of consumption.

Introduction:
The graphic representation of trophic levels is represented by a pyramid, which shows the flow of energy and nutrients through an ecosystem. There are three types of pyramids commonly used: pyramid of number, pyramid of biomass, and pyramid of energy.
Explanation:
Among the three types of pyramids, the pyramid of energy is always a true pyramid, unlike the others. Here's why:
Pyramid of Number:
- Represents the number of individuals at each trophic level.
- In some cases, the pyramid of numbers may not be a true pyramid due to the presence of parasites or predators with low numbers but high biomass at the top of the pyramid.
- This can lead to an inverted pyramid of numbers, where the number of individuals decreases at higher trophic levels.
Pyramid of Biomass:
- Represents the total biomass (mass of living organisms) at each trophic level.
- Can be a true pyramid, but it may also be inverted in some cases.
- Inverted pyramids of biomass can occur when the biomass of primary producers (e.g., plants) is low, but the biomass of consumers (e.g., insects) is high.
Pyramid of Energy:
- Represents the flow of energy through an ecosystem.
- Always a true pyramid because energy is lost at each trophic level due to respiration, heat loss, and incomplete digestion.
- As energy is transferred from one trophic level to the next, only a fraction of it is available for the next level.
- This results in a decrease in energy available at each higher trophic level, leading to a pyramid shape.
Conclusion:
In conclusion, the pyramid of energy is always a true pyramid unlike the pyramid of number and pyramid of biomass. This is because energy flow in an ecosystem follows the laws of thermodynamics, resulting in a decrease in energy available at higher trophic levels.

Structure of an Ecosystem:
The structure of an ecosystem refers to the organization and arrangement of its components. These components include living organisms (biotic factors) and the non-living environment (abiotic factors). The structure of an ecosystem determines the flow of energy and the interactions between different organisms. The key components of the ecosystem structure are:
1. Ecological Community:
- An ecological community consists of all the different species that interact with each other within a specific area.
- It includes plants, animals, microorganisms, and their relationships, such as predator-prey interactions, competition for resources, and symbiotic relationships.
- The ecological community is a fundamental part of the ecosystem structure as it influences the dynamics and stability of the ecosystem.
2. Quantity and Distribution of Abiotic Materials:
- Abiotic factors include non-living components of the ecosystem, such as soil, water, air, temperature, sunlight, and nutrients.
- The quantity and distribution of these abiotic materials play a crucial role in shaping the structure of an ecosystem.
- For example, the availability of water and nutrients determines the types and abundance of plant species, which in turn affects the diversity and abundance of animal species.
3. Range of Physical Conditions:
- The physical conditions within an ecosystem, such as temperature, humidity, rainfall, and altitude, form an important part of its structure.
- Different organisms have specific adaptations to survive and thrive within certain physical conditions.
- The range of physical conditions in an ecosystem determines the types of organisms that can inhabit it and influences their distribution and abundance.
4. All of the Above:
- The structure of an ecosystem includes all of the above components working together.
- The ecological community, quantity and distribution of abiotic materials, and range of physical conditions are interconnected and influence each other.
- Changes in any of these components can have cascading effects on the entire ecosystem.
In conclusion, the structure of an ecosystem is composed of the ecological community, quantity and distribution of abiotic materials, and range of physical conditions. All of these components are interconnected and contribute to the functioning and stability of the ecosystem.

Biotic Components of an Ecosystem
The biotic components of an ecosystem are the living organisms that interact with each other and their environment. These components include:
1. Producers:
- Producers, also known as autotrophs, are organisms that can produce their own food using sunlight or inorganic compounds.
- They are the foundation of the food chain, converting sunlight energy into chemical energy through photosynthesis.
- Examples of producers include plants, algae, and some bacteria.
2. Consumers:
- Consumers, also known as heterotrophs, are organisms that obtain their energy by consuming other organisms.
- They cannot produce their own food and rely on consuming producers or other consumers.
- Consumers can be further classified into different types based on their feeding habits:
- Herbivores: animals that eat plants
- Carnivores: animals that eat other animals
- Omnivores: animals that eat both plants and animals
3. Decomposers:
- Decomposers play a vital role in the ecosystem by breaking down organic matter and recycling nutrients back into the environment.
- They feed on dead organisms, waste products, and decaying organic matter, helping to return nutrients to the soil, air, and water.
- Examples of decomposers include fungi, bacteria, and certain types of insects.
4. All the Above:
- The correct answer to the question is D, as all the options mentioned (producers, consumers, and decomposers) are biotic components of an ecosystem.
- These components are interconnected and depend on each other for energy and resources, forming complex food webs and ecological relationships within the ecosystem.
In conclusion, the biotic components of an ecosystem include producers, consumers, and decomposers. These organisms interact with each other and the environment, playing essential roles in energy flow, nutrient cycling, and maintaining the overall balance of the ecosystem.

Autotrophic Organisms: Producers

Autotrophic organisms, specifically green plants, are known as producers. They use the process of photosynthesis to capture solar energy and convert it into organic food. Here are the key points to understand:

• Autotrophic organisms: These are organisms that are capable of producing their own food using energy from the environment.


• Green plants: In the context of autotrophic organisms, green plants are the primary examples. They contain chlorophyll, which enables them to capture sunlight for photosynthesis.


• Photosynthesis: This is the process by which autotrophic organisms, like green plants, convert sunlight, water, and carbon dioxide into glucose (organic food) and oxygen.


• Producers: Autotrophic organisms, such as green plants, are referred to as producers because they produce their own food through photosynthesis. They are the primary source of energy and nutrients for other organisms in an ecosystem.

Therefore, the correct answer is A: Producers.

The number of primary consumers is always less than the producers in a pyramid of numbers that represent an ecosystem with a large freshwater pond. In a large freshwater pond, the producers are always higher in number. The number of primary consumers is less than the producers, and secondary consumers are even less in number. The top consumers in a pond ecosystem are least in number.

Food Chain:
A food chain is a representation of the flow of energy in an ecosystem through the transfer of food from one organism to another. It shows how energy is transferred from producers to consumers and ultimately to decomposers. The food chain is an essential concept in understanding the ecological relationships between different organisms in an ecosystem.
Explanation:
The correct answer to the question is B: The transfer of food energy from producers to consumers. Here is a detailed explanation of why this is the correct answer:
- A food chain is a linear sequence of organisms, where each organism serves as a source of food for the next organism in the chain.
- It represents the flow of energy through the different trophic levels (feeding levels) in an ecosystem.
- The food chain starts with producers, such as plants or algae, which convert sunlight energy into chemical energy through photosynthesis.
- The primary consumers, such as herbivores, feed on the producers and obtain energy from them.
- The energy is then transferred to the secondary consumers, which are carnivores that feed on the herbivores.
- The energy flow continues through higher-level consumers, such as tertiary and quaternary consumers, until it reaches the top predator in the food chain.
- The energy is eventually transferred to decomposers, such as bacteria and fungi, which break down the remains of dead organisms and organic waste, releasing nutrients back into the ecosystem.
In summary, the food chain represents the transfer of food energy from producers to consumers, showing the interconnectedness and interdependence of organisms in an ecosystem. It is a fundamental concept in ecology and helps us understand the dynamics of energy flow and the relationships between different organisms.

Explanation:
The correct answer is B. Food chain.
Here is a detailed explanation of each option:
A. Food web:
- A food web is a complex network of interconnected food chains that shows the flow of energy and matter through an ecosystem.
- It includes multiple species and their interactions, including predator-prey relationships and the transfer of nutrients.
- While a food web is related to the movement of organic molecules in a community, it does not specifically refer to the sequence of species through which these molecules pass.
B. Food chain:
- A food chain is a linear sequence of organisms, where each organism is a source of food for the next organism in the chain.
- It represents the transfer of energy and nutrients from one organism to another in a community.
- In a food chain, organic molecules move from one species to another in a specific sequence, starting from producers (plants) to primary consumers (herbivores) to secondary consumers (carnivores) and so on.
- Therefore, the correct answer is B. Food chain.
C. Nutrient cycle:
- The nutrient cycle refers to the movement and recycling of nutrients through biotic and abiotic components of an ecosystem.
- It involves the cycling of elements such as carbon, nitrogen, phosphorus, and others through living organisms, soil, water, and the atmosphere.
- While organic molecules are involved in nutrient cycles, the nutrient cycle does not specifically represent the sequence of species through which these molecules pass.
D. Pyramid of energy:
- A pyramid of energy is a graphical representation of the flow of energy through different trophic levels in an ecosystem.
- It shows the decrease in energy as it moves from one trophic level to another, with each level consuming a fraction of the energy from the level below.
- While organic molecules contribute to the energy flow in a pyramid of energy, it does not specifically represent the sequence of species through which these molecules pass.
To summarize, the correct answer is B. Food chain, as it represents the linear sequence of species through which organic molecules pass in a community.

Food Web: A Group of Interconnected Food Chains
A food web is a group of interconnected food chains that shows the flow of energy and nutrients in an ecosystem. It represents the complex relationships between different organisms and their feeding habits. Here is a detailed explanation of why a food web is the correct answer:
1. Definition of a food web:
- A food web is a graphical representation of the feeding relationships between different organisms in an ecosystem.
- It consists of multiple food chains that are interconnected, forming a complex network of interactions.
2. Interconnected food chains:
- A food chain represents a linear sequence of organisms, where each organism is a source of food for the next organism in the chain.
- However, in reality, organisms are often part of multiple food chains, as they can have multiple predators or prey.
- These interconnected food chains form a web-like structure, showing the complexity of species interactions in an ecosystem.
3. Energy flow and nutrient cycling:
- Food webs not only show the transfer of energy from one organism to another but also the cycling of nutrients within an ecosystem.
- Energy flows through the food web from producers (plants) to consumers (herbivores, carnivores, omnivores) and eventually to decomposers (bacteria, fungi).
- Decomposers break down dead organisms and waste materials, releasing nutrients back into the environment for reuse by producers.
4. Importance of food webs:
- Food webs are essential for maintaining the balance and stability of ecosystems.
- They help regulate populations by showing the dependencies between different species.
- Changes in one part of the food web can have cascading effects on other organisms, leading to potential disruptions in the ecosystem.
Conclusion:
In summary, a group of interconnected food chains is referred to as a food web. It is a complex network that represents the flow of energy and nutrients in an ecosystem. Understanding food webs is crucial for comprehending the relationships between organisms and the overall functioning of ecosystems.

The energy utilized by the living world is primarily light.
Explanation:
- The living world, including plants, animals, and other organisms, primarily utilize light energy for their various biological processes.
- Light energy is essential for photosynthesis, the process by which plants convert sunlight into chemical energy in the form of glucose.
- This glucose serves as a source of energy for all living organisms, either directly or indirectly.
- Animals obtain this energy by consuming plants or other animals that have consumed plants.
- Light energy is also important for the regulation of biological rhythms and behaviors in living organisms.
- It plays a crucial role in the synthesis of Vitamin D in humans and other animals.
- Light energy is converted into electrical and chemical energy in the cells of living organisms, enabling them to carry out their physiological functions.
- While heat, electricity, and kinetic energy are also involved in various biological processes, they are secondary to the primary utilization of light energy by the living world.
- Therefore, the correct answer is C: Light.

Energy flow in ecosystem is unidirectional.
The energy flow in an ecosystem refers to the movement of energy through different trophic levels. It follows a specific direction and is not reversible. Here is a detailed explanation:
1. Energy flow in trophic levels:
- Producers, such as plants, obtain energy from the sun through photosynthesis. They convert this solar energy into chemical energy stored in organic compounds.
- Herbivores, or primary consumers, feed on plants and obtain energy from the organic compounds stored in them.
- Secondary consumers, such as carnivores, feed on herbivores and obtain energy from the organic compounds stored in their bodies.
- Tertiary consumers, or top predators, feed on other carnivores and obtain energy from the organic compounds stored in their prey.
- Decomposers, such as bacteria and fungi, break down dead organic matter and release energy back into the ecosystem.
2. Law of energy flow:
- The law of energy flow states that energy in an ecosystem flows in a unidirectional manner, from lower to higher trophic levels.
- This means that energy from the sun is transferred to producers, then to herbivores, then to carnivores, and so on.
- The energy is never transferred back to previous trophic levels, as it is used for growth, metabolism, and reproduction by the organisms at each level.
3. Energy loss:
- Energy is lost at each trophic level through various processes, such as respiration, heat loss, and waste production.
- Only a portion of the energy obtained by an organism is incorporated into its biomass and is available for the next trophic level.
- This energy loss limits the transfer of energy to higher trophic levels and explains why there are usually fewer individuals at higher trophic levels.
In conclusion, energy flow in an ecosystem is unidirectional, following a specific pathway from producers to decomposers. This ensures the transfer of energy through different trophic levels and maintains the functioning of the ecosystem.

The rate at which new tissues are formed in producers is known as the ecosystem's net primary productivity (NPP). Here is a detailed explanation of why the answer is A:
Definition:
Net primary productivity (NPP) refers to the rate at which energy is stored in the form of organic matter by producers (plants and other autotrophs) through photosynthesis, minus the energy lost through cellular respiration.
Explanation:
Net primary productivity is a crucial measure in understanding the energy flow and dynamics within an ecosystem. It represents the amount of energy available for consumption by primary consumers (herbivores) and subsequent trophic levels.
Key points:

• Net primary productivity is the rate of biomass production by producers after accounting for their own respiratory needs.


• It is calculated as the difference between gross primary productivity (GPP) and respiration.


• Gross primary productivity represents the total amount of energy captured by producers through photosynthesis.


• Respiration refers to the energy used by the producers for their own metabolic processes.


• The remaining energy after subtracting respiration from GPP is available for consumption by herbivores and subsequent trophic levels.


• NPP is an essential measure for understanding the productivity and energy flow in ecosystems, as it determines the amount of energy available for the growth and reproduction of organisms in higher trophic levels.

Therefore, the correct answer is A: Net primary productivity.

Amount of Light Used in the Production Process by Plants:
There are four options provided regarding the amount of light used in the production process by plants. Let's analyze each option and determine the correct answer.
A: 1 to 5%
- This option suggests that plants utilize only 1 to 5% of the light available to them for their production process.
B: 5% to 10%
- This option states that plants use 5% to 10% of the light during their production process.
C: 20 to 40%
- According to this option, plants utilize 20% to 40% of the available light for their production process.
D: more than 70%
- This option suggests that plants use more than 70% of the light available to them for their production process.
The correct answer is A: 1 to 5%. Plants use only a small fraction of the light they receive for their production process, as most of the light is reflected or transmitted through the leaves. The process of photosynthesis, which is the primary production process in plants, is not very efficient in converting light energy into chemical energy. Therefore, the amount of light used in the production process is relatively low compared to the total amount of light received by plants.

The importance of ecosystem maintenance lies in:
A: Cycling of materials
- Ecosystems play a crucial role in cycling essential nutrients and materials, such as carbon, nitrogen, and water.
- Through processes like photosynthesis, respiration, decomposition, and nutrient uptake by plants, ecosystems ensure the continuous circulation of these materials.
- Cycling of materials is important as it allows for the availability of nutrients to support the growth and survival of organisms within the ecosystem.
- It also helps maintain the balance and stability of the ecosystem by regulating nutrient levels and preventing nutrient depletion.
B: Flow of energy
- Energy flow refers to the transfer and transformation of energy within an ecosystem.
- Ecosystems rely on the flow of energy from the sun, which is captured by plants through photosynthesis.
- This energy is then transferred to herbivores when they consume plants, and further transferred to carnivores when they consume herbivores.
- The flow of energy is essential for the functioning of ecological processes and the maintenance of food chains and food webs.
- It determines the productivity, diversity, and stability of ecosystems, as well as the distribution and abundance of different organisms.
Both of the above
- Ecosystem maintenance requires the cycling of materials and the flow of energy to ensure the sustainability and functioning of the ecosystem.
- The cycling of materials and flow of energy are interconnected processes that support the growth, reproduction, and survival of organisms within the ecosystem.
- Without proper maintenance of these processes, ecosystems can experience imbalances, nutrient deficiencies, and disruptions in energy flow, leading to negative impacts on biodiversity and overall ecosystem health.
Conclusion:
Both the cycling of materials and the flow of energy are crucial aspects of ecosystem maintenance. They ensure the availability of nutrients, support the growth and survival of organisms, and maintain the balance and stability of ecosystems. Understanding and promoting these processes is essential for the conservation and sustainable management of ecosystems.

To determine the amount of energy utilized by herbivores from plants, we need to consider the energy transfer through the food chain. Here is a detailed explanation:
1. Trophic Levels:
- Plants are primary producers and occupy the first trophic level.
- Herbivores consume plants and occupy the second trophic level.
2. Energy Transfer:
- As energy flows through the food chain, it is transferred from one trophic level to the next.
- However, energy transfer is not 100% efficient, and a significant amount is lost as heat and metabolic processes.
- On average, only about 10% of the energy from one trophic level is transferred to the next.
3. Energy Utilization by Herbivores:
- Since herbivores consume plants, they receive energy from the plants they eat.
- As per the 10% energy transfer efficiency, herbivores utilize approximately 10% of the energy obtained from plants.
4. Answer:
- According to the given options, the correct answer is B: 10%.
Therefore, herbivores utilize 10% of the energy obtained from plants.

To determine the percentage of net primary production of total light intake, we need to consider the following information:
1. Net primary production (NPP): NPP refers to the amount of energy that plants capture through photosynthesis and convert into organic matter.
2. Total light intake: This refers to the total amount of light energy absorbed by plants for photosynthesis.
Now, let's break down the answer options and analyze each one:
A: 10%
- This option suggests that only 10% of the total light intake is converted into net primary production. However, this value is too low and not supported by scientific evidence.
B: 0.8-4%
- This option suggests that the range of net primary production as a percentage of total light intake is between 0.8% and 4%. This range is more plausible and aligns with scientific studies.
C: 10-20%
- This option suggests that the range of net primary production as a percentage of total light intake is between 10% and 20%. However, this range is too high and not consistent with scientific findings.
D: 15%
- This option suggests that exactly 15% of the total light intake is converted into net primary production. Although this value falls within a plausible range, it is more accurate to consider a range rather than a specific percentage.
Based on the analysis above, option B (0.8-4%) is the most appropriate answer. It represents a reasonable range for the percentage of net primary production of total light intake.

The flow of materials and energy in an ecosystem is both cyclic and linear.

1. Cyclic: The flow of materials and energy in an ecosystem is cyclic in nature. This means that there is a continuous recycling of nutrients and energy within the ecosystem. The key processes involved in the cyclic flow include:




• Photosynthesis: Green plants convert solar energy into chemical energy through the process of photosynthesis. This energy is stored in the form of glucose.


• Consumption: Herbivores consume plants and obtain energy from the stored glucose. This energy is transferred to the herbivores.


• Decomposition: When plants and animals die, their organic matter is broken down by decomposers such as bacteria and fungi. This releases nutrients back into the ecosystem, which can be used by plants for growth.


• Assimilation: Plants absorb nutrients from the soil and incorporate them into their tissues.




2. Linear: The flow of materials and energy in an ecosystem is also linear in nature. This means that energy flows through the ecosystem in a one-way direction. The key processes involved in the linear flow include:




• Trophic Levels: Organisms in an ecosystem are organized into trophic levels, which represent different levels of the food chain. Energy flows from one trophic level to another as organisms are consumed.


• Energy Transfer: As organisms consume other organisms, energy is transferred from one organism to another. However, energy is lost as heat during each transfer, resulting in a decrease in available energy at higher trophic levels.


• Energy Loss: Only a small fraction of the energy consumed by an organism is transferred to the next trophic level. This is known as the 10% rule, where approximately 10% of the energy is passed on to the next level, while the rest is lost as heat.


• Energy Flow: Ultimately, the energy in an ecosystem flows from producers (plants) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (top carnivores).

Therefore, the flow of materials and energy in an ecosystem is both cyclic and linear, as nutrients are continuously recycled while energy flows in a one-way direction.

Incorrect Statement: D. 75% of total carbon lies in geological component
Explanation:
The carbon cycle is the process through which carbon is exchanged between the atmosphere, oceans, land, and living organisms. It involves various processes that contribute to the movement and transformation of carbon. However, the statement D is incorrect because it states that 75% of total carbon lies in the geological component, which is not accurate. Here is a detailed explanation of the other statements and their correctness:
A. Lime rocks contribute to CO2 of water:
- Lime rocks, such as limestone, are composed of calcium carbonate (CaCO3).
- When these rocks undergo weathering and erosion, they release carbon dioxide (CO2) into the water through a process called carbonation.
- This statement is correct.
B. Atmospheric CO2 gets dissolved in water:
- Carbon dioxide (CO2) from the atmosphere can dissolve in water, forming carbonic acid (H2CO3).
- This process is known as carbonation and is one of the ways CO2 is removed from the atmosphere.
- This statement is correct.
C. CO2 is returned by combustion of fuel:
- When fossil fuels, such as coal, oil, and natural gas, are burned for energy, they release carbon dioxide (CO2) into the atmosphere.
- This is a significant source of CO2 emissions and contributes to the increase in atmospheric CO2 levels.
- This statement is correct.
D. 75% of total carbon lies in geological component:
- This statement is incorrect. The majority of carbon is found in the oceans, followed by the atmosphere, land, and living organisms.
- The geological component, which includes rocks, sediments, and fossil fuels, accounts for a smaller portion of the total carbon.
- The correct distribution of carbon is approximately 65,000 gigatons in the oceans, 720 gigatons in the atmosphere, 2,200 gigatons in land plants and soil, and 3,500 gigatons in living organisms.
In conclusion, the incorrect statement is D, which states that 75% of total carbon lies in the geological component. The correct distribution of carbon shows that the majority is found in the oceans, followed by the atmosphere, land, and living organisms.

Major Reservoir of Carbon in the Biosphere
The major reservoir of carbon in the biosphere lies in the hydrosphere.
Explanation:
The carbon cycle is the process by which carbon is exchanged between the atmosphere, land, and oceans. It is essential for the balance of carbon in the biosphere. The biosphere refers to all the living organisms on Earth, including plants, animals, and microorganisms. Carbon is a key element in all living organisms, and it is constantly cycled through various reservoirs.
Here is a detailed explanation of why the major reservoir of carbon in the biosphere is the hydrosphere:

• Atmosphere: The atmosphere contains carbon dioxide (CO2), which is a greenhouse gas. While the atmosphere does store a significant amount of carbon, it is not the major reservoir in the biosphere.


• Lithosphere: The lithosphere, which refers to the solid Earth, contains carbon in the form of rocks, minerals, and fossil fuels. While the lithosphere does store a large amount of carbon, it is not considered a major reservoir in the biosphere.


• Hydrosphere: The hydrosphere includes all the water on Earth, including oceans, lakes, rivers, and groundwater. Carbon is present in the form of dissolved CO2 in the water bodies. The oceans, in particular, are a significant reservoir of carbon in the biosphere. They absorb large amounts of carbon dioxide from the atmosphere through a process called carbon sequestration. This dissolved carbon plays a crucial role in the growth of marine plants and the overall carbon cycle.

Therefore, the correct answer is C: Hydrosphere as the major reservoir of carbon in the biosphere.

Biogeochemical cycling means -

Biogeochemical cycling refers to the movement and cycling of various elements and compounds through biotic and abiotic components of an ecosystem. It involves the transfer and recycling of nutrients and other substances necessary for life. The different components of biogeochemical cycling include the atmosphere, lithosphere (earth's crust), hydrosphere (water bodies), and the biosphere (living organisms).

Key points to note:

• Cycling of nutrients in an ecosystem: Nutrients such as carbon, nitrogen, phosphorus, and sulfur are essential for the growth and development of living organisms. Biogeochemical cycling ensures that these nutrients are recycled and made available for use by different organisms in an ecosystem.


• Cycling of water: Water is a vital component of biogeochemical cycling. It moves through various stages such as evaporation, condensation, and precipitation, facilitating the transport of nutrients and other substances.


• Cycling of energy in an ecosystem: While energy flows through an ecosystem, it is not considered a part of biogeochemical cycling. Energy enters an ecosystem through sunlight and is transferred from one organism to another through food chains and food webs. However, the energy is eventually lost as heat and is not recycled like nutrients.


• Cycling of gases between plants and the atmosphere: Gases such as oxygen, carbon dioxide, and nitrogen are exchanged between plants and the atmosphere through processes like photosynthesis and respiration. This exchange of gases is an important part of biogeochemical cycling.

In summary, biogeochemical cycling primarily refers to the cycling of nutrients in an ecosystem, but it also includes the cycling of water and gases between different components of the environment. It plays a crucial role in maintaining the balance and sustainability of ecosystems.

The least productive ecosystem is very deep lakes. Here is a detailed explanation:
1. Productivity in ecosystems:
- Productivity refers to the rate at which energy is converted into biomass by the producers (plants) in an ecosystem.
- It is a measure of how efficiently an ecosystem can support and sustain life.
2. Factors affecting productivity:
- Productivity in an ecosystem is influenced by various factors such as sunlight availability, nutrient availability, water availability, temperature, and the presence of decomposers.
- These factors determine the growth and reproduction of plants and the subsequent availability of food and resources for other organisms in the ecosystem.
3. Comparison of ecosystems:
- Coastal seas, grasslands, moist forests, and very deep lakes are all different types of ecosystems.
- Coastal seas are highly productive due to the abundance of sunlight and nutrients, supporting a wide variety of marine life.
- Grasslands and moist forests are also relatively productive due to favorable climatic conditions and nutrient availability.
4. Very deep lakes:
- Very deep lakes, on the other hand, have limited sunlight penetration and nutrient availability in the deeper regions.
- This restricts the growth of aquatic plants and algae, which are primary producers in the ecosystem.
- As a result, the food chain in deep lakes is relatively simple, with fewer organisms and lower biomass compared to other ecosystems.
5. Low productivity:
- The limited availability of sunlight and nutrients in very deep lakes hinders the efficient conversion of energy into biomass.
- This results in lower overall productivity and limited support for higher trophic levels in the food chain.
In conclusion, very deep lakes are considered the least productive ecosystem due to limited sunlight penetration and nutrient availability, leading to lower overall biomass and less support for life compared to other ecosystems.