The ecosystem is one of the most crucial topics in NEET (National Eligibility cum Entrance Test), covering concepts like food chains, ecological pyramids, energy flow, nutrient cycles, and trophic levels. Understanding these topics is essential to answering application-based and conceptual questions effectively.
This article provides a detailed set of ecosystem practice questions tailored for NEET aspirants. Each question is structured to test your conceptual understanding and application skills. We will cover MCQs, assertion-reason questions, match-the-following, fill-in-the-blanks, and short-answer questions.
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Let’s dive into the most important ecosystem practice questions for NEET!
1. Multiple Choice Questions (MCQs) – Test Your Knowledge
Question 1:
Which one of the following occupies more than one trophic level in an ecosystem?
A) Frog
B) Phytoplankton
C) Zooplankton
D) Fish
Answer: D) Fish
✅ Explanation: Fish can be both primary and secondary consumers. Some species feed on zooplankton (primary consumer), while larger fish prey on smaller fish (secondary consumer). This flexibility allows them to occupy multiple trophic levels.
Question 2:
What is secondary productivity in an ecosystem?
A) Rate of energy production by autotrophs
B) Rate of energy conversion by decomposers
C) Rate of formation of new organic matter by consumers
D) Rate of nutrient recycling
Answer: C) Rate of formation of new organic matter by consumers
✅ Explanation: Secondary productivity refers to the amount of biomass produced by heterotrophs (consumers) per unit time. It depends on how efficiently consumers convert their food into body mass.
Question 3:
Which biogeochemical cycle does NOT include a gaseous phase?
A) Carbon cycle
B) Nitrogen cycle
C) Phosphorus cycle
D) Oxygen cycle
Answer: C) Phosphorus cycle
✅ Explanation: Unlike carbon, oxygen, and nitrogen, the phosphorus cycle lacks a gaseous phase. It primarily occurs through rock weathering, soil absorption, plant uptake, and sedimentation in water bodies.
Question 4:
Identify the correct link (A) in this food chain:
Phytoplankton → “A” → Fish → Large Fish → Bird
A) Zooplankton
B) Benthos
C) Algae
D) Insect larvae
Answer: A) Zooplankton
✅ Explanation: Phytoplankton (producers) are consumed by zooplankton (primary consumers). These, in turn, are eaten by fish (secondary consumers). Thus, zooplankton is the missing link in this food chain.
Question 5:
Which of the following ecological pyramids is inverted?
A) Pyramid of numbers in grassland
B) Pyramid of energy
C) Pyramid of biomass in a forest
D) Pyramid of biomass in an aquatic ecosystem
Answer: D) Pyramid of biomass in an aquatic ecosystem
✅ Explanation: In aquatic ecosystems, phytoplankton have a small biomass but a high turnover rate. As a result, their biomass is less than that of zooplankton, leading to an inverted biomass pyramid.
2. Assertion-Reason Questions – Concept Clarity
Question 6:
✅ Assertion: Energy flow in an ecosystem is unidirectional.
✅ Reason: Energy captured by autotrophs does not return to the sun.
A) Both Assertion and Reason are true, and Reason explains Assertion.
B) Both Assertion and Reason are true, but Reason does not explain Assertion.
C) Assertion is true, but Reason is false.
D) Both Assertion and Reason are false.
Answer: A) Both Assertion and Reason are true, and Reason explains Assertion.
✅ Explanation: Energy moves from the sun → producers → consumers → decomposers but never back to the sun. This follows the second law of thermodynamics, where energy is lost as heat at each level.
Question 7:
✅ Assertion: Decomposers are essential for nutrient cycling.
✅ Reason: They convert organic material into inorganic forms, making nutrients available to producers.
A) Both Assertion and Reason are true, and Reason explains Assertion.
B) Both Assertion and Reason are true, but Reason does not explain Assertion.
C) Assertion is true, but Reason is false.
D) Both Assertion and Reason are false.
Answer: A) Both Assertion and Reason are true, and Reason explains Assertion.
✅ Explanation: Decomposers (bacteria, fungi) break down dead organisms, releasing minerals and nutrients back into the soil, which plants reuse.
3. Match the Following – Reinforce Your Learning
Question 8:
Match the components with their ecological roles.
| Component | Role |
|---|---|
| A) Producers | I) Convert organic matter into nutrients |
| B) Consumers | II) Convert sunlight into energy |
| C) Decomposers | III) Depend on producers for food |
✅ Answer:
- A → II (Producers: Convert sunlight into energy)
- B → III (Consumers: Depend on producers)
- C → I (Decomposers: Convert organic matter into nutrients)
4. Fill in the Blanks – Quick Recap
Question 9: The primary source of energy in an ecosystem is the ________.
✅ Answer: Sun
Explanation: The sun provides energy, which is harnessed by producers through photosynthesis.
Question 10: The process of water loss from plants through stomata is called ________.
✅ Answer: Transpiration
Explanation: Transpiration is crucial in the water cycle, helping in cooling plants and maintaining water balance.
5. True or False – Quick Check
Question 11: The pyramid of energy can never be inverted.
✅ Answer: True
Explanation: The energy pyramid is always upright because energy is lost at each trophic level due to respiration and metabolic activities.
Question 12: In a food chain, tertiary consumers are typically herbivores.
✅ Answer: False
Explanation: Tertiary consumers are usually carnivores or omnivores that eat secondary consumers (e.g., tigers, eagles, sharks).
6. Short Answer Questions – In-Depth Understanding
Question 13:
Explain the 10% Law of energy transfer.
✅ Answer: The 10% Law, given by Raymond Lindeman, states that only 10% of energy is transferred from one trophic level to the next. The rest is lost as heat and metabolic processes.
🔹 Example: If 1000 kcal of energy is available at the producer level, only 100 kcal reaches primary consumers, and so on.
Question 14:
What is the role of a keystone species in an ecosystem?
✅ Answer: Keystone species have a disproportionate effect on ecosystem structure. Their removal disrupts ecological balance.
🔹 Example: Wolves in Yellowstone Park help regulate deer populations, maintaining forest health.
7. Long Answer Questions – Deep Dive into Ecosystem Concepts
Question 15:
Describe the flow of energy in an ecosystem and explain why it is unidirectional.
✅ Answer: The flow of energy in an ecosystem follows a linear path from the sun to producers, then to consumers, and finally to decomposers. This is known as the unidirectional flow of energy because energy is not recycled like nutrients; instead, it is lost as heat at each level.
🔹 Steps of Energy Flow:
- Producers (Autotrophs) – Capture solar energy through photosynthesis and convert it into chemical energy stored in organic compounds (e.g., glucose).
- Primary Consumers (Herbivores) – Eat producers and gain chemical energy.
- Secondary Consumers (Carnivores/Omnivores) – Consume primary consumers.
- Tertiary Consumers (Top Predators) – Feed on secondary consumers and are at the highest trophic level.
- Decomposers (Fungi, Bacteria) – Break down dead organisms, recycling nutrients but not energy.
🔹 Why is it Unidirectional?
- According to the Second Law of Thermodynamics, energy is lost as heat at each trophic level.
- Energy does not return to the sun or lower trophic levels, making it unidirectional.
- Only 10% of energy is transferred from one level to the next, as per the 10% Law.
Question 16:
Discuss the importance of decomposers in an ecosystem.
✅ Answer: Decomposers are essential for maintaining ecosystem balance because they break down dead organic matter and recycle nutrients.
🔹 Roles of Decomposers:
- Nutrient Cycling: Convert complex organic material into simple inorganic substances like nitrogen, phosphorus, and carbon.
- Soil Fertility: Release essential minerals back into the soil, helping plants grow.
- Waste Decomposition: Prevent the accumulation of dead organisms, keeping the environment clean.
- Carbon Cycle Contribution: Release carbon dioxide (CO₂) during decomposition, aiding in photosynthesis.
🔹 Examples of Decomposers:
- Bacteria – Decompose organic matter in soil and water.
- Fungi – Break down lignin and cellulose in plant matter.
- Earthworms – Improve soil aeration and nutrient availability.
📌 Without decomposers, ecosystems would collapse due to waste buildup and nutrient depletion.
Question 17:
Compare and contrast grazing and detritus food chains with examples.
✅ Answer: The Grazing Food Chain (GFC) and Detritus Food Chain (DFC) are two primary energy flow pathways in an ecosystem.
🔹 Grazing Food Chain (GFC):
- Begins with living autotrophs (producers).
- Energy source: Sunlight.
- Example: Grass → Grasshopper → Frog → Snake → Hawk
🔹 Detritus Food Chain (DFC):
- Begins with dead organic matter (detritus).
- Energy source: Organic material from decomposing plants/animals.
- Example: Dead leaves → Earthworms → Insects → Birds
🔹 Key Differences:
| Feature | Grazing Food Chain | Detritus Food Chain |
|---|---|---|
| Starting Point | Living producers (plants, algae) | Dead organic matter |
| Energy Flow | From sunlight | From detritus |
| Example | Grass → Rabbit → Fox | Dead leaves → Fungi → Earthworm |
| Role in Ecosystem | Major pathway for energy transfer | Important for nutrient recycling |
📌 Both food chains are interconnected through decomposers, forming the food web.
8. Important Diagram-Based Questions
Question 18:
Draw and explain an Ecological Pyramid of Biomass in a forest ecosystem.
✅ Answer: The Pyramid of Biomass represents the total dry mass of organisms at each trophic level.
🔹 Forest Ecosystem Biomass Pyramid:
plaintextCopyEdit 🦅 Tertiary Consumers (Eagle)
🐍 Secondary Consumers (Snake)
🐁 Primary Consumers (Rodent)
🌳 Producers (Trees & Plants)
📌 Characteristics:
- In forests, biomass is highest at the producer level and decreases at higher levels.
- Energy is lost at each step due to metabolism, heat loss, and respiration.
- Unlike aquatic ecosystems, biomass pyramids in forests are upright.
Question 19:
Illustrate and explain the Nitrogen Cycle.
✅ Answer: The Nitrogen Cycle shows the movement of nitrogen through air, soil, and living organisms.
🔹 Steps of the Nitrogen Cycle:
- Nitrogen Fixation:
- Atmospheric N₂ is converted into ammonia (NH₃) by nitrogen-fixing bacteria (Rhizobium, Azotobacter).
- Nitrification:
- Ammonia is converted to nitrites (NO₂⁻) and then to nitrates (NO₃⁻) by Nitrosomonas and Nitrobacter.
- Assimilation:
- Plants absorb nitrates from the soil and use them to make proteins.
- Ammonification:
- Decomposers break down dead organisms, releasing ammonia.
- Denitrification:
- Anaerobic bacteria (Pseudomonas) convert nitrates back to nitrogen gas (N₂), returning it to the atmosphere.
📌 Importance:
- Essential for protein synthesis in living organisms.
- Maintains soil fertility and nitrogen balance.
9. Application-Based Questions
Question 20:
How does human activity impact the carbon cycle?
✅ Answer: Human activities disrupt the natural carbon cycle, leading to climate change.
🔹 Major Human Impacts:
- Fossil Fuel Burning:
- Releases excess CO₂, increasing greenhouse gas levels.
- Deforestation:
- Reduces carbon absorption by trees, raising atmospheric CO₂.
- Agriculture & Livestock:
- Produces methane (CH₄), a potent greenhouse gas.
- Industrial Activities:
- Increase carbon emissions from cement production and factories.
📌 Effects:
- Global warming & climate change
- Ocean acidification (due to excess CO₂ absorption)
- Loss of biodiversity
10. Conclusion – Mastering Ecosystem for NEET
Ecosystems form the foundation of ecological studies in NEET. Understanding energy flow, nutrient cycles, food chains, and environmental pyramids is crucial for scoring high in the exam.
✅ Key Takeaways:
- Energy flow is unidirectional and follows the 10% Law.
- Biogeochemical cycles maintain ecosystem stability.
- Decomposers are vital for nutrient recycling.
- Pyramids of energy, biomass, and numbers illustrate trophic relationships.
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11. Frequently Asked Questions (FAQs)
Q1: What is the difference between a food web and a food chain?
✅ A food chain follows a single pathway of energy flow, whereas a food web shows interconnected chains.
Q2: Why is the pyramid of energy always upright?
✅ Because energy is lost as heat at each trophic level, making higher levels receive less energy.
Q3: What happens if decomposers disappear from an ecosystem?
✅ Dead matter will accumulate, nutrients won’t be recycled, and food chains will collapse.
Q4: How can we conserve ecosystems?
✅ Reduce pollution, plant trees, and protect wildlife habitats.
Q5: Why is biodiversity important in ecosystems?
✅ It ensures stability, resilience, and ecosystem services like pollination and climate regulation.
