Which of the following is a man-made ecosystem?

Correct Option: B. Solution: An aquarium is considered a man-made ecosystem.

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Summary

Chapter 12: Ecosystem

Summary

An ecosystem is a structural and functional unit of nature comprising abiotic (inorganic materials like air, water, soil) and biotic components (producers, consumers, decomposers).
Ecosystems vary in size from small ponds to large forests and can be categorized into terrestrial (e.g., forests, grasslands, deserts) and aquatic (e.g., ponds, lakes, rivers).
Key components of ecosystems include:
- Productivity: Rate of biomass production by producers, divided into Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
- Decomposition: Breakdown of complex organic matter into inorganic substances by decomposers, involving fragmentation, leaching, and catabolism.
- Energy Flow: Unidirectional movement of energy from producers to consumers, with energy loss at each trophic level.
- Nutrient Cycling: Movement of nutrients through ecosystems, categorized into gaseous and sedimentary cycles.
Ecological pyramids illustrate the relationships between different trophic levels in terms of number, biomass, and energy.
The productivity of ecosystems varies based on environmental factors, species composition, and nutrient availability.

Learning Objectives

Define the concept of an ecosystem and its components.
Describe the structure and function of ecosystems, including abiotic and biotic factors.
Explain the processes of productivity, decomposition, energy flow, and nutrient cycling in ecosystems.
Differentiate between gross primary productivity (GPP) and net primary productivity (NPP).
Identify the roles of producers, consumers, and decomposers in an ecosystem.
Discuss the significance of ecological pyramids and their limitations.
Analyze energy transfer through trophic levels and the implications of the 10 percent law.
Illustrate the decomposition process and its importance in nutrient recycling.

Detailed Notes

Chapter 12: Ecosystem

12.1 Ecosystem - Structure and Function

An ecosystem is a functional unit of nature where living organisms interact with each other and the physical environment.
Ecosystems vary in size from small ponds to large forests or seas.
Two basic categories of ecosystems:
- Terrestrial: Forests, grasslands, deserts.
- Aquatic: Ponds, lakes, wetlands, rivers, estuaries.
Man-made ecosystems include crop fields and aquariums.

Key Components of Ecosystems

Productivity: Input of solar energy and biomass production.
Decomposition: Breakdown of organic matter.
Energy Flow: Transfer of energy through food chains/webs.
Nutrient Cycling: Movement of nutrients through the ecosystem.

12.2 Productivity

Primary Production: Amount of biomass produced by plants during photosynthesis, expressed in gm⁻² or kcal m⁻².
Gross Primary Productivity (GPP): Total production of organic matter.
Net Primary Productivity (NPP): Biomass available after respiration losses (NPP = GPP - R).
Secondary Productivity: Rate of formation of new organic matter by consumers.

12.3 Decomposition

Decomposers break down complex organic matter into inorganic substances.
Steps in Decomposition:
1. Fragmentation: Breakdown of detritus into smaller particles.
2. Leaching: Water-soluble nutrients leach into the soil.
3. Catabolism: Degradation of detritus by bacterial and fungal enzymes.
4. Humification: Formation of humus, a nutrient reservoir.
5. Mineralisation: Release of inorganic nutrients.

12.4 Energy Flow

Energy flow is unidirectional, moving from producers to higher trophic levels.
Only 10% of energy is transferred to each successive trophic level.

12.5 Ecological Pyramids

Types of Ecological Pyramids:
- Pyramid of Numbers: Represents the number of individuals at each trophic level.
- Pyramid of Biomass: Shows the dry weight of organisms at each level.
- Pyramid of Energy: Illustrates energy flow through the food chain.

Example Data for Pyramid of Numbers

Trophic Level	Number of Individuals
Tertiary Consumers (TC)	3
Secondary Consumers (SC)	354,000
Primary Consumers (PC)	708,000
Producers (P)	5,842,000

Example Data for Pyramid of Biomass

Trophic Level	Dry Weight (kg m⁻²)
Tertiary Consumers (TC)	1.5
Secondary Consumers (SC)	11
Primary Consumers (PC)	37
Producers (P)	809

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips in Ecosystem Studies

Common Pitfalls

Misunderstanding Trophic Levels: Students often confuse the roles of different trophic levels. Remember that producers are at the base, followed by primary consumers, secondary consumers, and tertiary consumers.
Ignoring Energy Loss: Many forget that energy decreases at each trophic level due to the 10% law, where only about 10% of energy is transferred to the next level.
Overlooking Decomposition Processes: Students may not fully describe the steps of decomposition, such as fragmentation, leaching, and catabolism.
Confusing Gross and Net Primary Productivity: Be clear that GPP is the total production of organic matter, while NPP is what remains after respiration losses.
Neglecting Nutrient Cycling: Failing to explain how nutrients are recycled in ecosystems can lead to incomplete answers.

Tips for Success

Use Diagrams: Practice drawing and labeling ecological pyramids and energy flow diagrams to visualize concepts better.
Understand Definitions: Make sure you can define key terms like primary productivity, decomposition, and ecological pyramids.
Practice Exam Questions: Work through past exam questions related to ecosystems to familiarize yourself with the format and types of questions asked.
Clarify Concepts: If unsure about concepts like food chains vs. food webs, seek clarification to avoid confusion in exams.
Review Examples: Study examples of different ecosystems (terrestrial vs. aquatic) to understand their unique characteristics and functions.

Practice & Assessment

Multiple Choice Questions

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

None of the above

Correct Answer: A

Solution:

The introduction of a large number of herbivorous insects feeding on a single tree species can result in an inverted pyramid of numbers, as the number of insects (primary consumers) can exceed the number of trees (producers).

Energy flow is bidirectional.

Energy flow is unidirectional and follows the second law of thermodynamics.

Energy is recycled through the ecosystem.

Energy flow does not follow the laws of thermodynamics.

Correct Answer: B

Solution:

Energy flow in an ecosystem is unidirectional, moving from the sun to producers and then to various consumers, with energy being lost as heat at each step, consistent with the second law of thermodynamics.

Fish

Zooplankton

Phytoplankton

Bacteria

Correct Answer: C

Solution:

Phytoplankton are the primary producers in aquatic ecosystems as they perform photosynthesis.

1400 kcal/m²/year

2000 kcal/m²/year

600 kcal/m²/year

2600 kcal/m²/year

Correct Answer: A

Solution:

Net primary productivity (NPP) is calculated as the difference between gross primary productivity (GPP) and the energy used in respiration by producers. NPP = GPP - Respiration = 2000 kcal/m²/year - 600 kcal/m²/year = 1400 kcal/m²/year.

A forest with a large number of insects feeding on a few trees.

A grassland with numerous herbivores and few predators.

A desert with sparse vegetation and abundant small mammals.

A wetland with a high density of aquatic plants and few fish.

Correct Answer: A

Solution:

An inverted pyramid of numbers occurs when the number of consumers exceeds the number of producers. In a forest with a large number of insects feeding on a few trees, the base of the pyramid (trees) is narrower than the next level (insects), creating an inverted shape.

Tertiary consumers

Secondary consumers

Primary consumers

Producers

Correct Answer: C

Solution:

In many aquatic ecosystems, the biomass of primary consumers, such as zooplankton, often exceeds that of producers like phytoplankton due to rapid turnover rates of the latter.

Temperature

Light availability

Nutrient availability

Water depth

Correct Answer: C

Solution:

In aquatic ecosystems, nutrient availability is often the limiting factor for productivity.

The existing herbivore population will increase due to competition.

The existing herbivore population will decrease due to competition.

There will be no change in the existing herbivore population.

The existing herbivore population will become extinct immediately.

Correct Answer: B

Solution:

The introduction of a new herbivore that competes for the same food source is likely to decrease the existing herbivore population due to increased competition for limited resources.

Decomposition rate would increase significantly.

Decomposition rate would decrease significantly.

Decomposition rate would remain unchanged.

Decomposition rate would fluctuate seasonally.

Correct Answer: B

Solution:

Decomposition is slower if detritus is rich in lignin, as lignin is resistant to microbial action, thus decreasing the rate of decomposition.

They are primary producers.

They convert inorganic matter into organic matter.

They break down dead organic matter into simple inorganic materials.

They are top carnivores.

Correct Answer: C

Solution:

Decomposers break down dead organic matter into simple inorganic materials, which are then absorbed by plants, thus playing a crucial role in nutrient cycling.

High lignin content in detritus

High temperature and moisture

Low nitrogen content in detritus

Anaerobic soil conditions

Correct Answer: B

Solution:

Decomposition is faster in warm and moist environments as these conditions enhance microbial activity. High lignin content and anaerobic conditions slow decomposition, while nitrogen-rich detritus speeds it up.

Geothermal energy

Wind energy

Solar energy

Chemical energy

Correct Answer: C

Solution:

Solar energy is the primary source of energy for most ecosystems, driving the process of photosynthesis in producers.

Phytoplankton

Zooplankton

Fungi

Lion

Correct Answer: B

Solution:

Zooplankton are primary consumers as they feed on phytoplankton, which are producers.

Wind

Sun

Water

Geothermal heat

Correct Answer: B

Solution:

The sun is the primary source of energy for all ecosystems on Earth, except for deep-sea hydrothermal ecosystems.

Producers

Primary consumers

Secondary consumers

Decomposers

Correct Answer: A

Solution:

Producers form the base of the food chain and typically have the largest population.

Decrease in primary productivity

Increase in primary productivity

No change in primary productivity

Primary productivity becomes zero

Correct Answer: A

Solution:

A reduction in photosynthetically active radiation (PAR) would decrease the primary productivity, as less solar energy is available for photosynthesis by aquatic producers.

Increase the rate of decomposition

Decrease the rate of decomposition

No effect on the rate of decomposition

Decomposition rate becomes zero

Correct Answer: A

Solution:

The presence of a decomposer that efficiently breaks down lignin-rich detritus would increase the rate of decomposition, as lignin is typically resistant to decomposition.

Pyramid of biomass is always upright.

Pyramid of energy can be inverted.

Pyramid of numbers is always upright.

Pyramid of energy is always upright.

Correct Answer: D

Solution:

The pyramid of energy is always upright because energy decreases at each successive trophic level due to energy loss as heat. The other pyramids can be inverted in certain ecosystems.

Amount of sunlight

Soil moisture

Presence of predators

Wind speed

Correct Answer: B

Solution:

Soil moisture is a critical factor influencing decomposition as it affects the activity of decomposers. Warm and moist environments favor decomposition, while dry conditions slow it down.

Grass

Cow

Wolf

Lion

Correct Answer: B

Solution:

Primary consumers are herbivores that feed on producers like plants. In this case, a cow is a primary consumer as it feeds on grass.

Forest

Aquarium

Lake

Desert

Correct Answer: B

Solution:

An aquarium is considered a man-made ecosystem.

100%

50%

1-5%

2-10%

Correct Answer: D

Solution:

Only 2-10% of incident solar radiation is photosynthetically active.

Herbaceous plants

Zooplankton

Carnivores

Decomposers

Correct Answer: A

Solution:

In a terrestrial ecosystem, herbaceous and woody plants are considered primary producers as they capture solar energy to produce organic matter.

It occupies multiple trophic levels

It is a tertiary consumer

It is a producer

It is a decomposer

Correct Answer: A

Solution:

The bird occupies multiple trophic levels because it acts as a primary consumer when eating seeds and fruits, and as a secondary consumer when eating insects and worms.

Zooplankton

Phytoplankton

Fish

Algae

Correct Answer: B

Solution:

Phytoplankton are the primary producers in aquatic ecosystems, capturing solar energy through photosynthesis.

5 kg/m²

50 kg/m²

500 kg/m²

100 kg/m²

Correct Answer: B

Solution:

According to the 10% law, only 10% of the biomass is transferred to the next trophic level. Therefore, the biomass of primary consumers would be 50 kg/m².

Cyclic and reversible

Unidirectional and non-cyclic

Bidirectional and cyclic

Random and unpredictable

Correct Answer: B

Solution:

Energy flow in an ecosystem is unidirectional, starting from the sun to producers and then to various consumers.

Energy is created at each trophic level.

Energy is lost as heat at each trophic level.

Energy is recycled completely at each trophic level.

Energy is stored indefinitely at each trophic level.

Correct Answer: B

Solution:

Pyramids of energy are always upright because energy is lost as heat at each trophic level, following the second law of thermodynamics.

100%

50%

2-10%

1-5%

Correct Answer: C

Solution:

Plants capture only 2-10% of the photosynthetically active radiation (PAR) from the sun.

Photosynthesis

Decomposition

Respiration

Transpiration

Correct Answer: B

Solution:

Decomposition involves the breakdown of complex organic compounds into simpler substances by decomposers.

Producers

Primary consumers

Secondary consumers

Decomposers

Correct Answer: A

Solution:

Producers, such as plants and phytoplankton, convert inorganic materials into organic matter using solar energy.

Phytoplankton

Zooplankton

Fishes

Bacteria

Correct Answer: B

Solution:

Zooplankton occupy the second trophic level in a pond ecosystem as they are primary consumers feeding on phytoplankton, which are the primary producers.

The bird exclusively feeds on plants.

The bird feeds on both plants and herbivores.

The bird is a top predator.

The bird is a decomposer.

Correct Answer: B

Solution:

The bird acting as both a primary and secondary consumer indicates it feeds on both plants (primary consumer role) and herbivores (secondary consumer role).

The biomass of the dominant tree species will increase due to increased leaf production.

The population of secondary consumers that feed on these insects will increase.

The rate of decomposition in the ecosystem will decrease due to reduced leaf litter.

The energy flow to tertiary consumers will increase significantly.

Correct Answer: B

Solution:

The introduction and increase in the population of the herbivorous insect will likely lead to an increase in the population of secondary consumers that feed on these insects. This is due to the increased availability of food for the secondary consumers, which are typically carnivores or omnivores that prey on herbivores.

Primary productivity would decrease.

Primary productivity would increase.

Primary productivity would remain unchanged.

Primary productivity would initially increase, then decrease.

Correct Answer: B

Solution:

Introducing a phytoplankton species with a higher photosynthesis rate would increase the ecosystem's primary productivity as more solar energy is converted into biomass.

0.002% of the incident solar energy

0.02% of the incident solar energy

0.2% of the incident solar energy

2% of the incident solar energy

Correct Answer: A

Solution:

If primary producers capture 2% of solar energy, then primary consumers receive 0.2% (10% of 2%), and secondary consumers receive 0.02% (10% of 0.2%).

Pond

Lake

Desert

Estuary

Correct Answer: C

Solution:

A desert is an example of a terrestrial ecosystem, whereas ponds, lakes, and estuaries are aquatic ecosystems.

Energy is gained at each trophic level.

Energy is lost as heat at each trophic level.

Energy is recycled back to the producers.

Energy is stored indefinitely in organisms.

Correct Answer: B

Solution:

Energy pyramids are always upright because energy is lost as heat at each trophic level, resulting in less energy being available to higher trophic levels.

Increase the NPP

Decrease the NPP

No change in the NPP

NPP becomes zero

Correct Answer: A

Solution:

The introduction of a phytoplankton species with a higher rate of photosynthesis would increase the net primary productivity (NPP) as it would capture more solar energy and convert it into biomass.

Nutrient cycling would slow down.

Nutrient cycling would accelerate.

Nutrient cycling would remain constant.

Nutrient cycling would become erratic.

Correct Answer: B

Solution:

Accelerated mineralization by detritivores would speed up the conversion of organic matter into inorganic nutrients, thereby accelerating nutrient cycling.

First

Second

Third

Fourth

Correct Answer: B

Solution:

Herbivores are primary consumers and occupy the second trophic level.

Zooplankton

Phytoplankton

Fishes

Benthos

Correct Answer: B

Solution:

In aquatic ecosystems, phytoplankton are the primary producers that capture solar energy.

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

None of the above

Correct Answer: A

Solution:

In a forest ecosystem, the pyramid of numbers can be inverted if there are fewer producers (large trees) supporting a larger number of herbivores (insects). The pyramid of energy is always upright.

Amount of sunlight

Soil pH

Temperature and soil moisture

Presence of herbivores

Correct Answer: C

Solution:

Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes.

NPP would increase due to enhanced efficiency of photosynthesis.

NPP would decrease due to reduced energy capture by producers.

NPP would remain unaffected.

NPP would initially decrease, then stabilize at a higher level.

Correct Answer: B

Solution:

A reduction in PAR would lead to less energy being captured by producers, thereby decreasing NPP.

Energy is created and destroyed within the ecosystem, violating the first law.

Energy flows in a circular path, consistent with the second law.

Energy flows unidirectionally and is lost as heat, consistent with both the first and second laws.

Energy is recycled completely without any loss, adhering to the first law.

Correct Answer: C

Solution:

Energy flows unidirectionally from the sun to producers and then to consumers, with some energy lost as heat at each step, aligning with the first law (energy conservation) and the second law (increased entropy).

They are primary producers that convert solar energy into biomass.

They are primary consumers that feed on producers.

They are decomposers that break down dead organic matter into inorganic substances.

They are secondary consumers that feed on primary consumers.

Correct Answer: C

Solution:

Saprophytes, such as fungi and bacteria, decompose dead organic matter, converting it into simpler inorganic substances that can be reused by producers.

They produce energy from sunlight.

They consume primary consumers.

They break down dead organic matter.

They occupy the top trophic level.

Correct Answer: C

Solution:

Decomposers break down dead organic matter into simpler substances, recycling nutrients back into the ecosystem.

High temperature and high soil moisture

Low temperature and high lignin content in detritus

High nitrogen content in detritus

Presence of earthworms and bacteria

Correct Answer: B

Solution:

Low temperature and high lignin content in detritus slow down decomposition as they inhibit microbial activity and make detritus resistant to breakdown.

Availability of sunlight

Nutrient concentration

Water temperature

Oxygen levels

Correct Answer: B

Solution:

In aquatic ecosystems, nutrient concentration, especially nitrogen and phosphorus, is often the limiting factor for productivity as they are essential for the growth of phytoplankton, which are primary producers.

Fix carbon dioxide

Break down dead organic matter

Capture solar energy

Consume primary consumers

Correct Answer: B

Solution:

Decomposers, such as fungi and bacteria, break down dead organic matter into simpler inorganic materials.

Phytoplankton

Zooplankton

Fishes

Benthos

Correct Answer: B

Solution:

Zooplankton are primary consumers as they feed on phytoplankton.

First trophic level

Second trophic level

Third trophic level

Fourth trophic level

Correct Answer: B

Solution:

Zooplankton are primary consumers and occupy the second trophic level in an aquatic ecosystem.

True or False

Correct Answer: False

Solution:

In a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.

Correct Answer: False

Solution:

Humus is a highly resistant substance to microbial action and decomposes at an extremely slow rate.

Correct Answer: False

Solution:

Energy flow in an ecosystem is unidirectional, moving from the sun to producers and then to various levels of consumers.

Correct Answer: True

Solution:

Primary productivity is defined as the rate at which producers capture solar energy and convert it into biomass.

Correct Answer: False

Solution:

Decomposition is largely an oxygen-requiring process.

Correct Answer: False

Solution:

In an ecological pyramid, producers form the base, not the apex, which is occupied by top-level consumers.

Correct Answer: True

Solution:

Primary productivity refers to the rate at which solar energy is captured by producers and converted into biomass.

Correct Answer: True

Solution:

The rate of decomposition is slower if detritus is rich in lignin and chitin, as these substances are resistant to microbial breakdown.

Correct Answer: True

Solution:

The pyramid of energy is always upright because energy decreases at each trophic level due to energy loss as heat, as per the second law of thermodynamics.

Correct Answer: False

Solution:

In some ecosystems, like the sea, the biomass of herbivores can exceed that of producers, resulting in an inverted pyramid of biomass.

Correct Answer: True

Solution:

The standing crop in an ecosystem is measured as the mass of living organisms (biomass) or the number in a unit area.

Correct Answer: True

Solution:

Producers in aquatic ecosystems are various species like phytoplankton and algae.

Correct Answer: True

Solution:

The interaction of biotic and abiotic components results in a physical structure that is characteristic for each type of ecosystem.

Correct Answer: False

Solution:

The pyramid of biomass in sea ecosystems is generally inverted because the biomass of fishes far exceeds that of phytoplankton.

Correct Answer: True

Solution:

The pyramid of energy is always upright because when energy flows from one trophic level to the next, some energy is always lost as heat.

Correct Answer: True

Solution:

In most ecosystems, all the pyramids, of number, of energy and biomass are upright.

Correct Answer: False

Solution:

In most ecosystems, including forests, the pyramid of biomass is upright, with producers having more biomass than herbivores.

Correct Answer: True

Solution:

In terrestrial ecosystems, a larger fraction of energy flows through the detritus food chain.

Correct Answer: False

Solution:

The pyramid of energy is always upright because energy is lost as heat at each trophic level.

Correct Answer: True

Solution:

The 10% energy transfer rule limits the number of trophic levels in a grazing food chain because only a small fraction of energy is passed to the next level.

Correct Answer: False

Solution:

Decomposition is largely an oxygen-requiring process.

Correct Answer: True

Solution:

In aquatic ecosystems, the biomass of fishes can exceed that of phytoplankton, resulting in an inverted pyramid of biomass.

Correct Answer: True

Solution:

Decomposers are crucial for nutrient cycling as they decompose dead organic matter into simpler inorganic materials, which are then available for uptake by producers.

Correct Answer: False

Solution:

Energy flow in an ecosystem is unidirectional, from the sun to producers and then to consumers.

Correct Answer: True

Solution:

The pyramid of biomass in aquatic ecosystems is often inverted because the biomass of consumers like fishes can exceed that of producers like phytoplankton.

Correct Answer: False

Solution:

In a terrestrial ecosystem, a larger fraction of energy flows through the detritus food chain rather than the grazing food chain.

Correct Answer: False

Solution:

Saprophytes or decomposers are not given a place in ecological pyramids, despite their vital role.

Correct Answer: False

Solution:

The rate of decomposition is slower in environments rich in lignin and chitin, as these substances are resistant to microbial breakdown.

Correct Answer: True

Solution:

Decomposition requires oxygen and is influenced by climatic factors such as temperature and moisture.

Correct Answer: False

Solution:

In a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.

Correct Answer: True

Solution:

In an aquatic ecosystem, GFC is the major conduit for energy flow.

Correct Answer: False

Solution:

Secondary consumers are typically carnivores that feed on primary consumers, which are herbivores.

Correct Answer: False

Solution:

In aquatic ecosystems, the pyramid of biomass is often inverted because the biomass of fishes can exceed that of phytoplankton.

Correct Answer: True

Solution:

Energy flow in an ecosystem is unidirectional as it moves from the sun to producers, then to consumers, and finally to decomposers, with energy being lost as heat at each step.

Correct Answer: False

Solution:

Producers are found at the first trophic level, not the highest, in a food chain.

Correct Answer: False

Solution:

Ecological pyramids do not accommodate saprophytes, even though they play a vital role in the ecosystem.

Correct Answer: True

Solution:

Energy flows from the sun to producers and then to consumers, following a unidirectional path.

Ecosystem

AI Learning Assistant

Summary

Chapter 12: Ecosystem

Summary

Learning Objectives

Learning Objectives

Detailed Notes

Chapter 12: Ecosystem

12.1 Ecosystem - Structure and Function

Key Components of Ecosystems

12.2 Productivity

12.3 Decomposition

12.4 Energy Flow

12.5 Ecological Pyramids

Example Data for Pyramid of Numbers

Example Data for Pyramid of Biomass

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips in Ecosystem Studies

Common Pitfalls

Tips for Success

Practice & Assessment

Multiple Choice Questions

Correct Answer: A

Q2.In an ecosystem, which of the following statements about energy flow is correct?

Correct Answer: B

Q3.In an aquatic ecosystem, which group of organisms is considered the primary producer?

Correct Answer: C

Q4.In a terrestrial ecosystem, if the gross primary productivity (GPP) is 2000 kcal/m²/year and the energy used by producers for respiration is 600 kcal/m²/year, what is the net primary productivity (NPP) of the ecosystem?

Correct Answer: A

Q5.In a terrestrial ecosystem, which of the following scenarios would most likely result in an inverted pyramid of numbers?

Correct Answer: A

Q6.In an aquatic ecosystem, which trophic level typically has the highest biomass?

Correct Answer: C

Q7.What is the primary factor that limits productivity in aquatic ecosystems?

Correct Answer: C

Q8.In a hypothetical forest ecosystem, a new species of herbivore is introduced. This herbivore exclusively feeds on a type of shrub that is the primary food source for an existing herbivore species. What is the most likely immediate effect on the existing herbivore population?

Correct Answer: B

Q9.In a hypothetical terrestrial ecosystem, a new type of plant with exceptionally high lignin content is introduced. What would be the most likely effect on the rate of decomposition in this ecosystem?

Correct Answer: B

Q10.In an ecosystem, what is the role of decomposers in the detritus food chain?

Correct Answer: C

Q11.Which of the following factors would most likely increase the rate of decomposition in a terrestrial ecosystem?

Correct Answer: B

Q12.What is the main source of energy for all ecosystems on Earth, except for the deep sea hydro-thermal ecosystems?

Correct Answer: C

Q13.In a food chain, which of the following is a primary consumer?

Correct Answer: B

Q14.What is the main source of energy for all ecosystems on Earth?

Correct Answer: B

Q15.In a food chain, which group of organisms has the largest population?

Correct Answer: A

Q16.In a laboratory simulation of an aquatic ecosystem, researchers find that the introduction of a pollutant reduces the photosynthetically active radiation (PAR) reaching the water surface. What is the most likely immediate effect on the ecosystem's primary productivity?

Correct Answer: A

Q17.A new species of decomposer is discovered in a forest ecosystem. This decomposer is highly efficient at breaking down lignin-rich detritus. What effect would this have on the rate of decomposition in the ecosystem?

Correct Answer: A

Q18.Which of the following statements about ecological pyramids is correct?

Correct Answer: D

Q19.In a forest ecosystem, which factor is most likely to influence the rate of decomposition?

Correct Answer: B

Q20.In a terrestrial ecosystem, which of the following organisms would be considered a primary consumer?

Correct Answer: B

Q21.Which of the following is a man-made ecosystem?

Correct Answer: B

Q22.What percentage of incident solar radiation is photosynthetically active?

Correct Answer: D

Q23.In a terrestrial ecosystem, which of the following is considered a primary producer?

Correct Answer: A

Q24.In an ecosystem study, it is observed that a particular species of bird acts as both a primary and secondary consumer. Which of the following best describes this bird's role in the food web?

Correct Answer: A

Q25.In an aquatic ecosystem, which of the following is typically the primary producer?

Correct Answer: B

Q26.In a grassland ecosystem, if the biomass of producers is 500 kg/m², what would be the expected biomass of primary consumers according to the 10% law?

Correct Answer: B

Q27.Which of the following best describes the energy flow in an ecosystem?

Correct Answer: B

Q28.What is the primary reason that pyramids of energy are always upright?

Correct Answer: B

Q29.What percentage of photosynthetically active radiation (PAR) is typically captured by plants in an ecosystem?

Correct Answer: C