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All questions of Ecosystem for ACT Exam

Ecosystem follows:
  • a)
    only first law of thermodynamics
  • b)
    only second law of thermodynamics
  • c)
    both first and second laws of thermodynamics
  • d)
    only third law of thermodynamics
Correct answer is option 'C'. Can you explain this answer?

Vijay Bansal answered
The first law, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in an isolated system. The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.
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Secondary productivity is the rate of formation of new organic matter by
  • a)
    Decomposer
  • b)
    Consumer
  • c)
    Producer
  • d)
    Parasite
Correct answer is option 'B'. Can you explain this answer?

Rajeev Saxena answered
Secondary productivity is the rate of formation of new organic matter by consumers. primary productivity depends on the producers inhabiting a particular area. Decomposers break down complex organic matter. Into inorganic substance like carbon dioxide water and nutrients. Parasitic species food on the body of other organisms.

Correct sequence for decomposition process is:
  • a)
    fragmentation -> leaching -> catabolism -> mineralisation
  • b)
    fragmentation -> leaching -> mineralisation -> humification
  • c)
    leaching -> fragmentation -> humification -> mineralisation
  • d)
    fragmentation -> catabolism -> leaching -> mineralisation
Correct answer is option 'D'. Can you explain this answer?

Gaurav Kumar answered
Decomposition is the process that involves the breakdown of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients.
The various processes involved in decomposition are as follows:
➢ Fragmentation 
  • It is the first step in the process of decomposition.
  • It involves the breakdown of detritus into smaller pieces by the action of detritivores such as earthworms.
➢ Leaching
  • It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.
➢ Catabolism
  • It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.
➢ Humification
  • The next step is humification which leads to the formation of a dark-coloured colloidal substance called humus, which acts as reservoir of nutrients for plants.
➢ Mineralization
  • The humus is further degraded by the action of microbes, which finally leads to the release of inorganic nutrients into the soil.
  • This process of releasing inorganic nutrients from the humus is known as mineralization.

 Ecosystem is
  • a)
    Open
  • b)
    Both open and close
  • c)
    Close
  • d)
    Neither opened nor closed
Correct answer is option 'A'. Can you explain this answer?

Rajat Kapoor answered
An ecosystem includes all of the living things (plants, animals and organisms) in a given area, interacting with each other, and also with their non-living environments (weather, earth, sun, soil, climate, atmosphere). Ecosystems are the foundations of the Biosphere and they determine the health of the entire earth system.

Which of the following is correct?
a)GPP + NPP = R
b)NPP – R = GPP
c)GPP – R = NPP
d)NPP – GPP = R
Correct answer is option 'C'. Can you explain this answer?

Srishti Sen answered
Net primary productivity (NPP) is equal to Gross primary productivity (GPP) minus Respiration loss (R). NPP is the available biomass for the consumption of heterotrophs in the ecosystem.

A detritus food chain will start with which of the following?
  • a)
    Protozoans
  • b)
    Rhizophora species
  • c)
    Bacteria & fungi
  • d)
    Earthworm
Correct answer is option 'C'. Can you explain this answer?

Rajesh Datta answered
A detritus food chain begins with dead organic matter. It is made of decomposers which are heterotrophic organism fungi and bacteria.Rhizophora species is a saprophyticheterotrophs.

Which one of the following is the most important service provided by ecosystems?
  • a)
    soil formation
  • b)
    aesthetic values
  • c)
    pollination
  • d)
    water purification
Correct answer is option 'A'. Can you explain this answer?

Mehul Iyer answered
Ecosystem services includes all activities performed by nature to benefits of human beings. The most important ecological service includes soil formation. Soil is essential for growth of plants that provide food to all living forms.

Humus will never be:
  • a)
    Good for plant growth.
  • b)
    Resistant to microbial action.
  • c)
    Reservoir of nutrients.
  • d)
    all of these
  • e)
    None of these.
Correct answer is option 'E'. Can you explain this answer?

Rohan Singh answered
  • Humus is a dark brown amorphous gummy substance formed by partial decomposition of plant and animal matter. 
  • It is not good for plant growth.
  • Humus is quite resistant to microbial action.
  • It is a reservoir of nutrients and is helpful in the maintenance of soil moisture as well as aeration.
Hence, None of these statements is correct about Humus.

There are only 4 or 5 trophic levels in food chain of an ecosystem due to :
  • a)
    Limited number of members in biotic community
  • b)
    Loss of energy at successive levels
  • c)
    Carrying capacity
  • d)
    Environmental resistance
Correct answer is option 'B'. Can you explain this answer?

Krish Saha answered
In most of the food chain of ecosystem only 4 to 5 trophic levels are present because loss of energy at successive levels is very high. Only 10% of energy is transferred to next trophic level.

Which of the following is not an ecological parameter?
  • a)
    Stratification
  • b)
    Number
  • c)
    Energy
  • d)
    Biomass
Correct answer is option 'A'. Can you explain this answer?

Mahesh Saini answered
Ecological parameter includes, biomass, energy and number of individual in the ecosystem. Stratification is not a part of ecological parameter.

Conditions favouring decomposition are :
  • a)
    high temperature and intermediate humidity
  • b)
    low temperature and low humidity
  • c)
    low temperature and high humidity
  • d)
    high temperature and low humidity
Correct answer is option 'A'. Can you explain this answer?

Tarun Saha answered
**Explanation:**

Decomposition is the process by which organic matter breaks down into simpler substances, such as carbon dioxide, water, and minerals. It is a natural process that is essential for nutrient recycling in ecosystems.

Conditions that favor decomposition are important to understand because they can determine the rate at which organic matter decomposes and the types of organisms involved in the process.

The correct answer to the given question is option 'A', which states that high temperature and intermediate humidity favor decomposition. Let's understand why this is the case:

**1. High Temperature:**
- Decomposition is an enzymatic process, meaning it is facilitated by the action of enzymes produced by microorganisms, such as bacteria and fungi.
- Enzymatic reactions are generally more efficient at higher temperatures because they increase the rate of biochemical reactions.
- High temperatures accelerate the metabolic activity of decomposer organisms, leading to faster decomposition rates.

**2. Intermediate Humidity:**
- Decomposer organisms require a certain level of moisture to carry out their metabolic processes effectively.
- If the humidity is too high, the excessive moisture can create an anaerobic environment (lack of oxygen) that is unfavorable for many decomposer organisms.
- If the humidity is too low, the lack of moisture restricts the activity of decomposer organisms.
- Intermediate humidity provides the ideal conditions for decomposer organisms to thrive and efficiently decompose organic matter.

**Conclusion:**
In conclusion, the correct answer to the given question is option 'A' (high temperature and intermediate humidity) because these conditions provide the ideal environment for the activity of decomposer organisms, leading to faster and more efficient decomposition of organic matter.

Available organic matter for herbivores is represented by:
  • a)
    Secondary productivity
  • b)
    GPP
  • c)
    NPP
  • d)
    All the these
Correct answer is option 'C'. Can you explain this answer?

Charvi Shah answered
The organic matter available for herbivores is called net primary productivity (NPP). Total amount of organic matter fix during photosynthesis is called Gross primary productivity (GPP).

Flow of energy in our ecosystem takes place :
  • a)
    only in one direction
  • b)
    possible in two directions
  • c)
    in three dimensions
  • d)
    may occur in multiple directions
Correct answer is option 'A'. Can you explain this answer?

Aniket Chawla answered
In ecosystem, flow of energy takes place in only one direction. The flow of energy takes place from producers to final consumers. Energy present in one trophic levels neversreturn back to producer.

Forest controls drought through
  • a)
    Functioning as water shed.
  • b)
    Lot of water plant
  • c)
    Retention of water and prevention of soil erosion.
  • d)
     Increasing rainfall
Correct answer is option 'D'. Can you explain this answer?

Akshat Joshi answered
The correct answer is option 'D' i.e., retention of water and prevention of soil erosion.

Explanation:
Forests are essential for the survival of life on earth. They are responsible for various ecological, environmental, and social benefits. Forests play a crucial role in controlling drought by retaining water and preventing soil erosion. Let's discuss how forests control drought through water retention and soil erosion prevention:

Retention of water:

Forests help in retaining water in the following ways:

1. Watershed: Forests act as a water catchment area and function as a natural watershed. They store and release water gradually, reducing the risk of floods and droughts.

2. Groundwater recharge: Forests help in recharging groundwater by allowing rainwater to seep into the soil, thus replenishing underground water resources.

3. Transpiration: Trees in the forest transpire water, which helps in the formation of clouds and precipitation, leading to increased rainfall.

Prevention of soil erosion:

Forests help in preventing soil erosion in the following ways:

1. Root systems: Trees in the forest have deep root systems that hold the soil in place and prevent it from eroding.

2. Canopy cover: The canopy cover of trees in the forest acts as a barrier, reducing the impact of raindrops on the soil surface and preventing soil erosion.

3. Organic matter: Forests are rich in organic matter, which helps in improving soil structure, reducing soil erosion, and retaining water.

Conclusion:

Forests play a crucial role in controlling drought by retaining water and preventing soil erosion. Therefore, it is important to conserve and protect forests to ensure a sustainable future for all.

Producers in the aquatic ecosystem are :
  • a)
    Shrubs
  • b)
    Herbacious plants
  • c)
    Phytoplanktons
  • d)
    Zooplanktons
Correct answer is option 'C'. Can you explain this answer?

Ishani Nambiar answered
Phytoplanktons are small floating photosynthetic unicellular plant. In the aquatic ecosystem phytoplankton are producers that fix solar energy by the process of photosynthesis.

Amount of biomass produced per unit area by green plants is called?
  • a)
    Respiration
  • b)
    Primary productivity
  • c)
    Secondary productivity
  • d)
    Tertiary productivity
Correct answer is option 'B'. Can you explain this answer?

Arpita Tiwari answered
Primary productivity is the amount of biomass produced per unit area by green plants in an ecosystem. Producers fix the solar energy by the process of photosynthesis.

What is the rate at which solar energy is converted and stored by the producers per unit area over a time period called?
  • a)
    Tertiary productivity
  • b)
    Primary productivity
  • c)
    Gross primary productivity
  • d)
    Net productivity
Correct answer is option 'A'. Can you explain this answer?

Top Rankers answered
The rate at which solar energy is converted and stored by the producers per unit area over a time period is called primary productivity. The solar energy is converted into usable form by plants with the help of photosynthesis.

Speed of decomposition will be:
  • a)
    fast if detritus is rich in simple sugars
  • b)
    slow if detritus contains water soluble substances like sugars
  • c)
    fast if detritus is rich in lignin
  • d)
    slow if detritus lacks chitin
Correct answer is option 'A'. Can you explain this answer?

Mrinalini Bajaj answered
In detritus food chain, speed of decomposition will be fast if detritus is rich in simple sugar that can be easily decomposed into glucose by saprophytes that includes bacteria and fungi.

The biomass available for consumption to heterotrophs and the rate of formation of new organic matter by consumers are defined as
  • a)
    Net primary productivity and gross primary productivity, respectively.
  • b)
    Gross primary productivity and net primary productivity, respectively.
  • c)
    Gross primary productivity and secondary productivity, respectively.
  • d)
    Net primary productivity and secondary productivity, respectively.
Correct answer is option 'D'. Can you explain this answer?

Maulik Gupta answered
The correct answer is option D, Net primary productivity and secondary productivity, respectively.

Explanation:
- Net primary productivity (NPP) is the biomass available for consumption to heterotrophs after the autotrophs have utilized some of the organic matter for their own metabolism through respiration.
- Secondary productivity is the rate of formation of new organic matter by consumers (heterotrophs) that eat the autotrophs or other heterotrophs.
- Gross primary productivity (GPP) is the total amount of organic matter produced by autotrophs through photosynthesis, including the organic matter used for their own respiration.
- Gross secondary productivity is the total amount of organic matter assimilated by consumers, including the organic matter lost through excretion and egestion.

Therefore, the correct answer is option D, as NPP and secondary productivity are the two parameters that indicate the amount of organic matter available for consumption to higher trophic levels in an ecosystem.

If the number of producers in a pond ecosystem is approx 10 million then the number of top carnivore (in million) which it can support may be:
  • a)
    20
  • b)
    2
  • c)
    11
  • d)
    50
Correct answer is option 'B'. Can you explain this answer?

Arnav Iyer answered
In a food chain, number of organisms reduce from producer to carnivores at each trophic levels. So, the number of carnivores will be less than the prouder which is less than 10 million.

If 20000J energy is present in transducers then 3°consumers will get:
  • a)
    20J
  • b)
    200J
  • c)
    10000J
  • d)
    2000J
Correct answer is option 'A'. Can you explain this answer?

Anuj Pillai answered
Explanation:

To understand the answer to this question, we need to consider the concept of energy distribution among multiple consumers.

Energy Distribution:
When energy is distributed among multiple consumers, the total energy remains constant. In this case, we have a total of 20,000 J of energy available. We need to distribute this energy among 3 consumers.

Calculation:
To find out how much energy each consumer will receive, we divide the total energy by the number of consumers.

Total energy = 20,000 J
Number of consumers = 3

Energy per consumer = Total energy / Number of consumers
Energy per consumer = 20,000 J / 3
Energy per consumer ≈ 6,666.67 J

Answer:
According to the options provided, the closest answer to 6,666.67 J is option 'A' which is 20 J. Therefore, each consumer will receive approximately 20 J of energy.

Explanation of the Correct Answer:
Option 'A' states that each consumer will get 20 J of energy. This means that when the total energy of 20,000 J is distributed among 3 consumers, each consumer will receive approximately 20 J of energy.

Reasoning:
To find the correct answer, we need to divide the total energy by the number of consumers (20,000 J / 3). This calculation results in approximately 6,666.67 J per consumer. Since option 'A' is the closest answer to this value, it is the correct answer.

Summary:
In summary, when 20,000 J of energy is distributed among 3 consumers, each consumer will receive approximately 20 J of energy. This is calculated by dividing the total energy by the number of consumers.

Functional and dynamic unit of nature where living and non-living components interact with each-other is:
  • a)
    Biome
  • b)
    Community
  • c)
    Tropic structure
  • d)
    Ecosystem
Correct answer is option 'D'. Can you explain this answer?

Pallabi Reddy answered
Ecosystem is the functional and dynamic unit of nature where living and non-living components interact with each other for flow of energy and biomass from producer to consumers.

Which of the following organisms are primary consumers in a grazing food chain?
  • a)
    Phytoplankton
  • b)
    Zooplankton
  • c)
    Carnivores
  • d)
    Decomposers
Correct answer is option 'B'. Can you explain this answer?

Mrinalini Basak answered
Understanding Primary Consumers in a Grazing Food Chain
In a grazing food chain, primary consumers play a crucial role by feeding on primary producers. Let's break down the organisms listed in the question to understand why the correct answer is zooplankton.
What Are Primary Consumers?
- Primary consumers are organisms that eat primary producers (plants and phytoplankton) to obtain energy.
- They are usually herbivores or omnivores, and their main role is to convert the energy stored in producers into a form that can be consumed by higher trophic levels.
Analysis of the Options
- Phytoplankton: These are primary producers, not consumers. They convert sunlight into energy through photosynthesis.
- Zooplankton: These organisms are primary consumers. They feed on phytoplankton and other small organisms, thus playing a vital role in the food chain by transferring energy from producers to higher trophic levels.
- Carnivores: These are secondary or tertiary consumers that feed on other animals. They do not consume primary producers directly.
- Decomposers: Organisms like fungi and bacteria break down dead organic matter, recycling nutrients back into the ecosystem, but they are not considered consumers in the grazing food chain.
Conclusion
In summary, zooplankton are classified as primary consumers because they directly consume phytoplankton, which are the primary producers in aquatic ecosystems. Their role is essential for energy transfer in the food chain, making them a key component of the grazing food web.

Ecological pyramids does not give any place to :
  • a)
    Saprophytes
  • b)
    Transducers
  • c)
    Predators
  • d)
    Parasites
Correct answer is option 'A'. Can you explain this answer?

Krish Saha answered
In ecological pyramids, saprophytes do not have any place even though they play very vital role in ecosystem. This is because ecological pyramids does not take into account same species belonging to two or more trophic levels.

Assertion (A): Nutrient cycling includes both gaseous and sedimentary cycles, which play crucial roles in ecosystem health.
Reason (R): The gaseous cycle relies solely on the atmosphere as its reservoir, while the sedimentary cycle depends on the Earth's crust.
  • a)
    If both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • b)
    If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • c)
    If Assertion is true but Reason is false
  • d)
    If both Assertion and Reason are false
Correct answer is option 'B'. Can you explain this answer?

Top Rankers answered
 
- Assertion Evaluation: The assertion is true because nutrient cycling indeed comprises both gaseous (e.g., carbon cycle) and sedimentary (e.g., phosphorus cycle) types, and both are essential for maintaining ecosystem stability.
- Reason Evaluation: The reason is also true as it accurately describes the reservoirs for both cycles; however, it does not explain why both cycles are crucial for ecosystem health or how they interact.
- Conclusion: Since both the assertion and reason are true but the reason does not serve as the correct explanation for the assertion, the correct answer is Option B.
 

For greater efficiency a food chain must be:
  • a)
    without transducers
  • b)
    shorter
  • c)
    longer
  • d)
    without microconsumers
Correct answer is option 'B'. Can you explain this answer?

Abhishek Desai answered
For greater efficiency a food chain must have three to four trophic levels. At each trophic levels loss of energy is very high so very small amount of energy is left after there trophic level.

Breakdown of detritus by microbial enzymes into simple forms is called?
  • a)
    Mineralization
  • b)
    Catabolism 
  • c)
    Fragmentation
  • d)
    Leaching
Correct answer is option 'B'. Can you explain this answer?

Naina Dey answered
Catabolism - Breakdown of Detritus by Microbial Enzymes

Catabolism is the breakdown of complex organic matter into simpler compounds by the action of microbial enzymes. In the process of catabolism, detritus is decomposed and transformed into various forms that are readily available for use by other living organisms. This process is important for the maintenance of the ecosystem as it cycles nutrients and energy from dead organic matter back into the living world.

Mechanism of Catabolism

The process of catabolism involves the following steps:

1. Fragmentation: The detritus is fragmented into smaller particles by the action of physical and chemical forces.

2. Leaching: The soluble compounds are leached out of the detritus and are transported to other parts of the ecosystem.

3. Mineralization: The remaining organic matter is decomposed by the action of microbial enzymes into simpler forms such as carbon dioxide, water, and inorganic nutrients like nitrogen and phosphorus.

4. Catabolism: The simpler compounds are further broken down into energy and essential nutrients by the action of microbial enzymes.

Significance of Catabolism

Catabolism plays a crucial role in the cycling of nutrients and energy in the ecosystem. The breakdown of detritus by microbial enzymes releases essential nutrients like nitrogen and phosphorus into the soil, which can be taken up by plants for growth. The energy released during catabolism is also utilized by other living organisms in the ecosystem, thereby sustaining the food web. In addition, catabolism also helps in the removal of waste materials from the ecosystem.

Conclusion

Catabolism is a complex process that involves the breakdown of detritus into simpler forms by the action of microbial enzymes. This process is essential for the cycling of nutrients and energy in the ecosystem and helps in sustaining the food web. The significance of catabolism in the maintenance of the ecosystem cannot be overemphasized as it plays a crucial role in the removal of waste materials and the release of essential nutrients into the environment.

Which of the following is an example of catabolism?
  • a)
    Breaking down of stones into smaller parts.
  • b)
    Decrease in size of mountain.
  • c)
    Breakdown of detritus by microbial enzymes.
  • d)
    All of the these.
Correct answer is option 'C'. Can you explain this answer?

Abhishek Desai answered
Breakdown of detritus by microbial enzymes into simple forms is called catabolism in which mass of the organisms decrease without any external reduction is size of the organisms.

Stability will be provided to the ecosystem by:
  • a)
    Ecological pyramids
  • b)
    Food webs
  • c)
    Decomposition
  • d)
    Food chains
Correct answer is option 'B'. Can you explain this answer?

Krish Saha answered
Food web is formed by interaction between a numbers of food chains having common members. Stability of ecosystem largely depends upon the kinds of food web exists in it for proper flow of energy.

 A biome is
  • a)
    Sum of all ecosystems on the Earth
  • b)
    Biotic components in a population
  • c)
    Sum of ecosystems in a geographical area
  • d)
    Biotic components in an ecosystem
Correct answer is option 'C'. Can you explain this answer?

Vijay Bansal answered
A biome is a large ecosystem, extending over a wide geographic region, characterized by certain dominant life-forms—most notably, trees or the lack thereof.Within a biome or ecosystem, the sum of all living organisms is referred to as the biological community.

In an aquatic ecosystem, which of the following is a limiting factor for productivity?
  • a)
    Carbon dioxide
  • b)
    Nutrient availability
  • c)
    Oxygen
  • d)
    Soil composition
Correct answer is option 'B'. Can you explain this answer?

Mrinalini Basak answered
Nutrient Availability as a Limiting Factor
In aquatic ecosystems, productivity is primarily influenced by the availability of nutrients. Here’s a breakdown of why nutrient availability is crucial:
1. Definition of Productivity
- Productivity refers to the rate at which energy is produced in an ecosystem, particularly through photosynthesis in plants and phytoplankton.
2. Role of Nutrients
- Aquatic organisms, especially primary producers like phytoplankton, need nutrients such as nitrogen, phosphorus, and potassium to grow and reproduce.
- These nutrients are essential for various biological processes, including the synthesis of proteins, nucleic acids, and chlorophyll.
3. Limiting Nutrients
- In many aquatic environments, one or more nutrients can be in short supply, which limits growth and productivity.
- For instance, in oceanic regions, nitrogen is often a limiting nutrient, while in freshwater systems, phosphorus may be more limiting.
4. Impact on Ecosystem
- When nutrient levels are low, the growth of primary producers decreases, leading to a reduction in the overall biomass of the ecosystem.
- This decrease affects the entire food web, as fewer producers mean less energy is available for herbivores and, consequently, for higher trophic levels.
5. Other Factors Considered
- While carbon dioxide, oxygen, and soil composition play roles in aquatic systems, they do not limit productivity to the same extent as nutrient availability does.
- For example, carbon dioxide is typically abundant in water, and oxygen levels can vary but are not usually the primary limiting factor for productivity.
In summary, nutrient availability is the critical limiting factor for productivity in aquatic ecosystems, as it directly influences the growth and reproduction of primary producers, thereby affecting the entire ecosystem's health and energy flow.

What type of pyramid is generally inverted in an aquatic ecosystem?
  • a)
    Pyramid of numbers
  • b)
    Pyramid of energy
  • c)
    Pyramid of biomass
  • d)
    All pyramids
Correct answer is option 'C'. Can you explain this answer?

Mrinalini Basak answered
Understanding the Inverted Pyramid of Biomass
In aquatic ecosystems, the pyramid of biomass is often inverted, which is distinct from the typical structure seen in terrestrial ecosystems. Here’s why:
1. Definition of Biomass Pyramid
- The biomass pyramid represents the total mass of living organisms at each trophic level.
- In a typical terrestrial ecosystem, it decreases as you move from producers to top consumers.
2. Aquatic Ecosystems Characteristics
- In aquatic environments, producers such as phytoplankton have a low biomass compared to the organisms that feed on them, like zooplankton and small fish.
- The rapid reproduction and turnover rates of phytoplankton lead to a situation where the total weight of consumers can exceed that of the producers.
3. Reasons for Inversion
- High Reproduction Rates: Phytoplankton reproduce quickly, but their biomass is low at any given time.
- Efficiency of Energy Transfer: In aquatic systems, energy transfer from producers to consumers is highly efficient, allowing a larger biomass of consumers.
- Size Difference: Small primary producers can support larger consumers, leading to an inverted biomass pyramid.
4. Implications
- This structure challenges the traditional understanding of food webs and energy flow.
- It highlights the unique dynamics of aquatic ecosystems where even small organisms can support a diverse and larger community of consumers.
In conclusion, the pyramid of biomass is inverted in aquatic ecosystems due to the high productivity and turnover of phytoplankton, resulting in greater biomass of consumers compared to producers.

What is the correct formula for net primary productivity (NPP)?
  • a)
    NPP = GPP + R
  • b)
    NPP = GPP - R
  • c)
    NPP = R - GPP
  • d)
    NPP = GPP × R
Correct answer is option 'B'. Can you explain this answer?

Siddharth Iyer answered
Understanding Net Primary Productivity (NPP)
Net Primary Productivity (NPP) is a crucial concept in ecology, representing the amount of organic matter produced by plants after accounting for the energy used in respiration.
Key Components of NPP
- Gross Primary Productivity (GPP): This is the total amount of energy captured by photosynthesis in a given area and time.
- Respiration (R): This refers to the energy that plants consume during the process of respiration, where they convert organic matter back into carbon dioxide and water, releasing energy for biological functions.
The Correct Formula for NPP
- The relationship between these components is expressed as:
NPP = GPP - R
- This means that NPP is the difference between the total energy captured (GPP) and the energy used by plants for their own metabolic processes (R).
Why is this Important?
- Energy Balance: NPP indicates the energy available for growth and reproduction in plants, which forms the basis of the food web.
- Ecosystem Health: High NPP values usually signify healthy ecosystems with abundant plant life, while low values can indicate stress or degradation.
Conclusion
Understanding the formula NPP = GPP - R is essential for studying ecosystem productivity, energy flow, and the overall health of biological communities. It highlights the balance between energy captured through photosynthesis and the energy expended through respiration, a critical factor in ecological assessments.

Which of the following is a decomposer?
  • a)
    Earthworm
  • b)
    Grasshopper
  • c)
    Fungi
  • d)
    Eagle
Correct answer is option 'C'. Can you explain this answer?

Avantika Gupta answered
Understanding Decomposers
Decomposers play a crucial role in ecosystems by breaking down dead organic matter and recycling nutrients back into the environment. Among the options provided, fungi are classified as decomposers.
Why Fungi are Decomposers
- Role in Ecosystem: Fungi break down complex organic substances, such as dead plants and animals, into simpler compounds. This process is essential for nutrient cycling.
- Methods of Decomposition: They secrete enzymes that help in breaking down materials like cellulose and lignin, which are hard to decompose.
- Nutrient Replenishment: The nutrients released by fungi during decomposition enrich the soil, promoting plant growth and sustaining the ecosystem.
Other Options Explained
- Earthworm (Option A): While earthworms contribute to soil health by aerating it and breaking down organic matter, they are classified as detritivores, not true decomposers. They consume organic material and excrete nutrient-rich castings.
- Grasshopper (Option B): Grasshoppers are herbivores that feed on living plants. They do not break down dead organic material, thus they cannot be considered decomposers.
- Eagle (Option D): Eagles are predators that feed on living animals. They do not decompose organic matter; rather, they consume it.
Conclusion
In summary, fungi (Option C) are the correct answer as they play the vital role of decomposers in nature, facilitating the breakdown of organic matter and nutrient cycling essential for ecosystem health.

Which of the following components are abiotic in an ecosystem?
  • a)
    Plants and animals
  • b)
    Soil, water, and air
  • c)
    Bacteria and fungi
  • d)
    Herbivores and carnivores
Correct answer is option 'B'. Can you explain this answer?

Mohit Rajpoot answered
Abiotic components are non-living elements of an ecosystem, such as soil, water, and air. These components form the physical environment that interacts with the biotic (living) components.

The boundary or transition between two or more communities is called:
  • a)
    Ecotype
  • b)
    Thermocline
  • c)
    Ecotone
  • d)
    Biome
Correct answer is option 'C'. Can you explain this answer?

Rohit Shah answered
An ecotone is a transition area between two biomes. It is where two communities meet and integrate. It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and grassland ecosystems). An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.

The word ecotone was coined from a combination of eco(logy) plus -tone, from the Greek tonos or tension – in other words, a place where ecologies are in tension.

What is the process of breaking down complex organic matter into inorganic substances called?
  • a)
    Productivity
  • b)
    Energy Flow
  • c)
    Decomposition
  • d)
    Nutrient Cycling
Correct answer is option 'C'. Can you explain this answer?

Mohit Rajpoot answered
Decomposition is the process by which decomposers like fungi and bacteria break down complex organic matter into simpler inorganic substances such as carbon dioxide, water, and nutrients.

Which of the following is a unit of primary productivity?
  • a)
    g
  • b)
    g-2 or kcal m-2
  • c)
    kcal
  • d)
    m
Correct answer is option 'B'. Can you explain this answer?

Stuti Sen answered
Understanding Primary Productivity
Primary productivity refers to the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem. It is a crucial measure for understanding energy flow and ecosystem health.
Units of Measurement
The correct answer for the unit of primary productivity is option b) g m-2 or kcal m-2. Let's break down why this is the case:
  • g m-2: This unit indicates grams of biomass produced per square meter of area. It quantifies the mass of organic material generated by producers in a defined area over a specific time.
  • kcal m-2: This unit measures the energy produced per square meter. It reflects the caloric value of organic material generated through photosynthesis, indicating how much energy is stored by plants in a given area.

The Incorrect Options
  • Option a) g: While grams can measure biomass, it lacks the area and time components necessary for primary productivity. Therefore, it does not represent productivity effectively.
  • Option c) kcal d: This unit suggests energy over time (daily) but does not include the area dimension. Without specifying area, it cannot measure productivity accurately.

Conclusion
In summary, primary productivity is best expressed in terms of biomass or energy per unit area, making option b) g m-2 or kcal m-2 the appropriate choice. Understanding these units is essential for evaluating ecosystem productivity and health in ecological studies.

Find the odd one out with respect to functional component of ecosystem
  • a)
    Productivity
  • b)
    Stratification
  • c)
    Decomposition
  • d)
    Nutrient cycling
Correct answer is option 'B'. Can you explain this answer?

Ambition Institute answered
The components of the ecosystem are seen to function as a unit when you consider the following aspects:
(i) Productivity;
(ii) Decomposition;
(iii) Energy flow; and
(iv) Nutrient cycling.
 

Chapter doubts & questions for Ecosystem - Biology for ACT 2025 is part of ACT exam preparation. The chapters have been prepared according to the ACT exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for ACT 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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