Question 1. What is meant by a habitat?
Answer:
A habitat is the natural place or environment where an organism lives and obtains the conditions necessary for survival.
Question 2. A pond contains fish, frogs, algae, insects and microorganisms. Does this represent a population or a community? Give a reason.
Answer:
It represents a community because it consists of different populations of organisms living and interacting in the same habitat.
Question 3. Differentiate between biotic and abiotic components of an ecosystem.
Answer:
- Biotic components are the living parts of an ecosystem, such as plants, animals and microorganisms.
- Abiotic components are the non-living factors, such as air, water, soil, sunlight and temperature.
Question 4. Why are green plants considered producers?
Answer:
Green plants are called producers because they prepare their own food using sunlight, water and carbon dioxide through photosynthesis.
Question 5. A fish cannot survive in a pond that contains very little dissolved oxygen. Which component of its habitat is lacking?
Answer:
The fish is lacking sufficient dissolved oxygen, which is an important abiotic component required for respiration.
Question 6. What is the difference between a food chain and a food web?
Answer:
- A food chain shows a single, linear pathway through which energy passes from one organism to another.
- A food web consists of several interconnected food chains and shows multiple feeding relationships.
Question 7. Arrange the following organisms in a correct food chain:
Eagle, grass, snake, grasshopper, frog
Answer:
$$
\text{Grass} \rightarrow \text{Grasshopper} \rightarrow \text{Frog} \rightarrow \text{Snake} \rightarrow \text{Eagle}
$$
Question 8. In a food chain, why does the number of organisms generally decrease towards the top?
Answer:
Energy decreases at successive trophic levels. Therefore, fewer organisms can generally be supported at higher trophic levels.
Question 9. What is meant by a trophic level?
Answer:
A trophic level refers to the feeding position occupied by an organism in a food chain.
For example:
- Producers form the first trophic level.
- Herbivores form the second trophic level.
- Small carnivores may form the third trophic level.
Question 10. Why are decomposers essential for maintaining an ecosystem?
Answer:
Decomposers break down dead plants, animals and waste materials into simpler substances. This returns nutrients to the soil, supports plant growth and prevents the accumulation of dead organic matter.
Question 11. What may happen if decomposers disappear from an ecosystem?
Answer:
Dead plants, animals and waste materials would begin to accumulate. Nutrients would not be effectively recycled back into the soil, affecting plant growth and ecosystem balance.
Question 12. A bee obtains food from a flower while helping in pollination. What type of interaction is this?
Answer:
This is an example of mutualism because both organisms benefit from the interaction.
Question 13. An orchid grows on a tree and benefits from support, while the tree is neither helped nor harmed. Identify this interaction.
Answer:
This interaction is called commensalism. One organism benefits, while the other remains unaffected.
Question 14. Ticks obtain nourishment from a dog and may cause harm to it. What type of relationship exists between them?
Answer:
This is parasitism because the tick benefits while the dog is harmed.
Question 15. Why do organisms compete with one another in an ecosystem?
Answer:
Organisms compete when they require the same limited resources, such as food, water, space or sunlight. Competition helps regulate population size and resource use.
Question 16. Explain how plants and abiotic components depend on one another.
Answer:
Plants require abiotic factors such as sunlight, water, carbon dioxide and nutrients from the soil for growth and food production. At the same time, plants can modify environmental conditions by releasing oxygen and helping to protect soil from erosion.
Question 17. A forest area is reduced because of deforestation. Why might animals begin entering nearby villages?
Answer:
When forests shrink, animals may lose access to sufficient food, water and shelter. As a result, they may move towards farms and human settlements in search of resources.
Question 18. Consider the following situation:
Pollution destroys aquatic plants in a pond. Fish begin to die, and the number of insects increases.
Explain how this single disturbance can lead to further changes in the ecosystem.
Answer:
The destruction of aquatic plants can reduce oxygen levels in the pond, causing fish populations to decrease. With fewer fish, insect populations may increase. These insects may then affect nearby crops, leading farmers to use pesticides, which can further pollute the soil and water. This shows that a change in one part of an ecosystem can produce a chain of effects.
Question 19. Why is a food web generally more complex than a food chain?
Answer:
A food web contains several interconnected feeding relationships. An organism may have more than one food source or predator, making the system more complex than a single linear food chain.
Question 20. What is meant by decomposition?
Answer:
Decomposition is the process in which dead plants, animals and waste materials are broken down into simpler substances by decomposers such as bacteria and fungi.
Question 21. How does decomposition help maintain soil fertility?
Answer:
During decomposition, nutrients from dead organisms are returned to the soil. These nutrients can then be reused by plants for growth.
Question 22. A farmer continuously uses large quantities of chemical fertilisers and pesticides. Predict two possible effects on the ecosystem.
Answer:
- Soil health and fertility may be affected.
- Beneficial organisms and other useful components of the ecosystem may be harmed.
Question 23. How can knowledge of ecosystems help farmers adopt more sustainable practices?
Answer:
Understanding ecosystems can help farmers select suitable crops, use resources carefully and reduce excessive dependence on chemical fertilisers and pesticides. This can help protect soil health and support long-term food production.
Question 24. Why are different organisms found in different habitats?
Answer:
Different habitats have different conditions, including temperature, water availability, food resources, soil type and sunlight. Organisms survive in habitats to which they are adapted.
Question 25. Give one example each of an aquatic and a terrestrial habitat.
Answer:
- Aquatic habitat: Pond or river
- Terrestrial habitat: Forest or grassland
Question 26. Why is the Sundarbans ecosystem important to humans and the environment?
Answer:
The Sundarbans ecosystem provides important environmental support. It helps protect coastal regions and supports rich biodiversity. Such ecosystems are also important for environmental stability and human survival.
Question 27. What could happen to an ecosystem if one species is completely removed?
Answer:
The removal of one species can disturb feeding relationships and affect the populations of other organisms. In a food web, some organisms may survive by using alternative food links, but the overall ecosystem may still experience changes.
Question 28. A group of deer of the same species lives in a particular forest. What ecological term describes this group?
Answer:
The group is called a population because it consists of organisms of the same species living in a particular area.
Question 29. Why is an ecosystem described as an interconnected system?
Answer:
An ecosystem is interconnected because organisms depend on one another and on non-living components for food, water, oxygen, shelter and other requirements. Therefore, a change in one component can affect several others.
Question 30. Case-Based Question
A pond ecosystem contains aquatic plants, fish, insects and microorganisms. Due to pollution, many aquatic plants die.
(a) Which important resource in the pond may decrease?
(b) How might the fish population be affected?
(c) Which ecological principle is demonstrated by this situation?
Answer:
(a) The level of dissolved oxygen may decrease.
(b) Fish may die or their population may decrease because oxygen availability is affected.
(c) The situation demonstrates the interdependence of organisms and components within an ecosystem, where a disturbance in one part can lead to several other changes.
Question 31. Forest Disturbance and Its Effects
A large number of trees in a forest are cut down to clear land for construction. After some years, the nearby area experiences increased soil erosion and changes in rainfall patterns.
Which explanation best accounts for these changes?
A. Trees increase soil erosion by loosening the soil.
B. Tree roots help hold the soil, and trees also contribute to the water cycle.
C. Cutting trees increases the number of decomposers, causing less rainfall.
D. Trees prevent sunlight from reaching the soil, which causes erosion.
Answer: B
Explanation: Tree roots help bind the soil and reduce soil erosion. Trees also contribute to the water cycle through transpiration, so large-scale removal can affect rainfall patterns.
Question 32. Disturbance in a Pond Food Relationship
In a pond ecosystem, frogs feed on certain larvae. These larvae later develop into dragonflies, which feed on insects such as bees and butterflies.
If all the frogs are removed from the pond, what is the most likely long-term effect?
A. The number of larvae may increase, leading to more dragonflies and a possible decrease in pollinating insects.
B. All insects in the pond will immediately disappear.
C. The number of pollinating insects will definitely increase because frogs are absent.
D. The amount of sunlight available to plants will decrease.
Answer: A
Explanation: Removing frogs can allow the larvae they normally consume to increase. More larvae may develop into more dragonflies, which can reduce populations of insects such as bees and butterflies. This shows how disturbing one part of an ecosystem can affect other organisms.
Question 33. Decomposers and Ecosystem Balance
A farmer notices that dead leaves, animal remains and organic waste are accumulating in a particular area because the population of decomposers has greatly decreased.
Which additional change is most likely to occur over time?
A. Nutrient recycling in the soil may be reduced.
B. Producers will stop requiring sunlight.
C. Herbivores will become decomposers.
D. All abiotic factors will disappear.
Answer: A
Explanation: Decomposers break down dead organic matter and return nutrients to the soil. If their number decreases, dead matter accumulates and nutrient recycling is affected.
Question 34. Sustainable Farming Situation
A farmer observes that birds regularly feed on insects that damage his crops. Instead of immediately spraying more pesticides, the farmer protects the natural habitat around the farm.
How can this decision support sustainable farming?
A. Birds will increase soil erosion.
B. Natural predators can help control pest populations.
C. The crops will no longer require sunlight.
D. Decomposers will stop recycling nutrients.
Answer: B
Explanation: Birds can act as natural pest controllers by feeding on crop-damaging insects. This may reduce excessive dependence on chemical pesticides and help maintain a healthier farm ecosystem.
Question 35. Analysing an Ecological Interaction
An insect lives on a large tree and uses it mainly for shelter and support. The insect benefits from the arrangement, but the tree is neither helped nor harmed.
Which ecological relationship does this situation represent?
A. Parasitism
B. Mutualism
C. Commensalism
D. Competition
Answer: C
Explanation: In commensalism, one organism benefits while the other organism is neither significantly benefited nor harmed.
Question 1. Which statement about food chains and food webs is correct?
A. A food web consists of only one feeding pathway.
B. Producers depend on consumers for preparing food.
C. Food chains can connect to form a food web.
D. Every organism occupies only one feeding relationship.
Answer: C. Food chains can connect to form a food web
Question 2. Several food chains connected with one another form a:
A. Food web
B. Population
C. Habitat
D. Community
Answer: A. Food web
Question 3. A bee obtains nectar from a flower and, in the process, helps the flower reproduce. This interaction is called:
A. Parasitism
B. Mutualism
C. Competition
D. Predation
Answer: B. Mutualism
Question 4. Which group best represents a population?
A. All living organisms in a forest
B. Different species of fish living in a pond
C. All the deer of one species living in a particular forest
D. Plants, animals and soil in a grassland
Answer: C. All the deer of one species living in a particular forest
Question 5. Which sequence correctly shows the usual flow of feeding relationships?
A. Carnivore → Herbivore → Producer
B. Producer → Herbivore → Carnivore
C. Herbivore → Producer → Decomposer
D. Consumer → Producer → Carnivore
Answer: B. Producer → Herbivore → Carnivore
Question 6. If decomposers become very scarce in an ecosystem, which material is most likely to accumulate?
A. Dead organic matter
B. Sunlight
C. Oxygen
D. Water vapour
Answer: A. Dead organic matter
Question 7. Which process returns nutrients from dead organisms to the soil?
A. Pollination
B. Decomposition
C. Transpiration
D. Predation
Answer: B. Decomposition
Question 8. A mosquito feeds on a human and causes harm to the host. This relationship is an example of:
A. Mutualism
B. Commensalism
C. Parasitism
D. Cooperation
Answer: C. Parasitism
Question 9. What is the primary source of energy for most ecosystems?
A. Soil
B. Sunlight
C. Wind
D. Water
Answer: B. Sunlight
Question 10. Which statement best describes an ecosystem?
A. Only the animals living in an area
B. A group of plants of the same species
C. Living organisms interacting with one another and with non-living factors
D. Only producers and consumers living together
Answer: C. Living organisms interacting with one another and with non-living factors
Question 11. Which interaction occurs when one organism benefits while the other is neither helped nor harmed?
A. Commensalism
B. Mutualism
C. Parasitism
D. Competition
Answer: A. Commensalism
Question 12. Why are green plants known as producers?
A. They consume dead organisms.
B. They prepare their own food using sunlight.
C. They depend on animals for energy.
D. They feed only on herbivores.
Answer: B. They prepare their own food using sunlight.
Question 13. What is a likely result of removing large numbers of trees from a forest?
A. Greater soil stability and more shade
B. Increased rainfall and improved habitat
C. Reduced soil erosion
D. Habitat loss and possible reduction in rainfall
Answer: D. Habitat loss and possible reduction in rainfall
Question 14. Which condition would most likely indicate that an ecosystem is not properly balanced?
A. Presence of producers and consumers
B. Excessive accumulation of waste
C. Abiotic factors supporting life
D. Predators controlling prey populations
Answer: B. Excessive accumulation of waste
Question 15. In a pond, algae are eaten by insects, and insects are eaten by fish. When fish die, decomposers break them down. This sequence mainly helps maintain:
A. Nutrient cycling and energy flow
B. Only the number of fish
C. The amount of sunlight
D. The temperature of the pond
Answer: A. Nutrient cycling and energy flow