Chapter-12 Nature in Harmony — Online MCQ Test
SCIENCE · Grade 8 · CBSE(NCERT)
Practice Chapter-12 Nature in Harmony with a free chapter-wise online MCQ test.
This chapter covers: ecosystem - food chain - food web - biodiversity - conservation - interdependence.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-12 Nature in Harmony — Important Questions & Answers
What is an ecosystem?
- A. A community of living organisms in an area
- B. A system where living organisms and their physical environment interact together
- C. Only the plants found in a particular region
- D. A group of animals living in the same forest
Answer: B. A system where living organisms and their physical environment interact together
An ecosystem is the interaction between biotic (living) and abiotic (non-living) components in an area.
An ecosystem is the interaction between biotic (living) and abiotic (non-living) components in an area.
Which of the following is a producer in a food chain?
- A. Lion
- B. Grass
- C. Rabbit
- D. Snake
Answer: B. Grass
Producers are autotrophs that make their own food through photosynthesis; grass is a plant producer.
Producers are autotrophs that make their own food through photosynthesis; grass is a plant producer.
What is a food chain?
- A. A sequence of organisms where each feeds on the previous one
- B. A network of interconnected food chains
- C. Only the eating habits of carnivores
- D. The total number of animals in a forest
Answer: A. A sequence of organisms where each feeds on the previous one
A food chain is a linear sequence showing energy transfer from producer to consumers through feeding relationships.
A food chain is a linear sequence showing energy transfer from producer to consumers through feeding relationships.
Which organism is a secondary consumer in the food chain: Grass → Rabbit → Fox?
- A. Grass
- B. Rabbit
- C. Fox
- D. Soil
Answer: B. Rabbit
Secondary consumers eat primary consumers; rabbit eats grass (primary consumer role) and is eaten by fox.
Secondary consumers eat primary consumers; rabbit eats grass (primary consumer role) and is eaten by fox.
In the food chain Plants → Grasshopper → Bird → Cat, how many trophic levels are there?
- A. 2
- B. 3
- C. 4
- D. 5
Answer: D. 5
There are 5 trophic levels: producer (plants), primary consumer (grasshopper), secondary consumer (bird), tertiary consumer (cat), and decomposers.
There are 5 trophic levels: producer (plants), primary consumer (grasshopper), secondary consumer (bird), tertiary consumer (cat), and decomposers.
Why is biodiversity important for the stability of an ecosystem?
- A. It provides more food for humans
- B. It increases the number of predators
- C. Greater biodiversity means more options for organisms to adapt to changes
- D. It prevents all natural disasters
Answer: C. Greater biodiversity means more options for organisms to adapt to changes
High biodiversity ensures ecosystem resilience; if one species fails, others can fill ecological roles and maintain balance.
High biodiversity ensures ecosystem resilience; if one species fails, others can fill ecological roles and maintain balance.
Which of the following represents a correct food chain?
- A. Carnivore → Herbivore → Plant → Sun
- B. Sun → Plant → Herbivore → Carnivore
- C. Plant → Sun → Herbivore → Carnivore
- D. Herbivore → Carnivore → Plant → Sun
Answer: B. Sun → Plant → Herbivore → Carnivore
Energy flows from the sun to plants (producers), then to herbivores (primary consumers), then to carnivores (secondary consumers).
Energy flows from the sun to plants (producers), then to herbivores (primary consumers), then to carnivores (secondary consumers).
In a pond ecosystem, algae are eaten by small fish, which are eaten by large fish, which are eaten by herons. If algae production is reduced due to pollution, what would be the ultimate effect?
- A. Only large fish populations would decrease
- B. All organisms in the food chain would eventually be affected
- C. Only herons would be unaffected
- D. Small fish would thrive without competition
Answer: B. All organisms in the food chain would eventually be affected
Reduction in primary producers (algae) reduces energy input for the entire ecosystem, cascading effects through all trophic levels.
Reduction in primary producers (algae) reduces energy input for the entire ecosystem, cascading effects through all trophic levels.
A researcher studying a temperate forest finds that removing a keystone species (a small rodent that disperses seeds) leads to dramatic ecosystem changes. Why is this seemingly insignificant species so important?
- A. Because it produces the most energy in the ecosystem
- B. Because it has disproportionate effects on ecosystem structure and plant diversity through seed dispersal
- C. Because it is the largest animal in the forest
- D. Because it is a top predator
Answer: B. Because it has disproportionate effects on ecosystem structure and plant diversity through seed dispersal
Keystone species have roles disproportionate to their abundance; the rodent's seed dispersal maintains plant diversity essential for ecosystem function.
Keystone species have roles disproportionate to their abundance; the rodent's seed dispersal maintains plant diversity essential for ecosystem function.
In the context of bioaccumulation, why do organisms at higher trophic levels accumulate more toxins even if they are exposed to lower concentrations?
- A. They have larger bodies that store more toxins
- B. They consume many organisms containing accumulated toxins; toxins concentrate as energy decreases per trophic level
- C. They live longer and have more time to accumulate toxins
- D. Toxins are only present at higher trophic levels
Answer: B. They consume many organisms containing accumulated toxins; toxins concentrate as energy decreases per trophic level
Bioaccumulation occurs because predators consume numerous prey organisms; toxins from all prey accumulate in the predator's tissues.
Bioaccumulation occurs because predators consume numerous prey organisms; toxins from all prey accumulate in the predator's tissues.