Vidaara.orgClass 12 · Mathematics
CodeVID-M12-WS
Ecosystem — Practice Worksheet
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Choose the correct option (A, B, C or D) for each question.
- The answer key is at the end — try the paper first!
Section A — Multiple Choice (1 mark each)
17 × 1 = 17 marks
1.
A unit where organisms interact with each other and the non-living environment is an:
- A.Ecosystem
- B.Atom
- C.Organ
- D.Cell
2.
Sunlight, water and soil in an ecosystem are:
- A.Biotic components
- B.Abiotic components
- C.Producers
- D.Consumers
3.
Green plants that make their own food are:
- A.Producers
- B.Consumers
- C.Decomposers
- D.Predators
4.
Animals that eat only plants are:
- A.Carnivores
- B.Herbivores
- C.Decomposers
- D.Producers
5.
Bacteria and fungi that recycle nutrients are:
- A.Producers
- B.Decomposers
- C.Herbivores
- D.Carnivores
6.
The passage of food from one organism to the next is a:
- A.Food chain
- B.Life cycle
- C.Water cycle
- D.Pyramid
7.
Each feeding step in a food chain is a:
- A.Trophic level
- B.Habitat
- C.Niche
- D.Population
8.
Many interconnected food chains form a:
- A.Food web
- B.Pyramid
- C.Cycle
- D.Habitat
9.
The ultimate source of energy for most ecosystems is the:
- A.Soil
- B.Sun
- C.Wind
- D.Moon
10.
According to the 10% law, energy transferred to the next trophic level is about:
- A.10%
- B.50%
- C.90%
- D.100%
11.
Energy flow in an ecosystem is:
- A.One-way (does not cycle)
- B.Circular
- C.Backward
- D.Zero
12.
The pyramid of energy is always:
- A.Upright
- B.Inverted
- C.Flat
- D.Circular
13.
Nutrients move through the ecosystem in:
- A.One-way flow
- B.Biogeochemical cycles
- C.Straight lines
- D.No path
14.
Which is a biogeochemical cycle?
- A.Carbon cycle
- B.Food chain
- C.Trophic level
- D.Pyramid
15.
Clean air, pollination and climate regulation provided by nature are:
- A.Ecosystem services
- B.Pollutants
- C.Food webs
- D.Trophic levels
16.
The rate at which producers make biomass by photosynthesis is the:
- A.Primary productivity
- B.Secondary productivity
- C.Decomposition
- D.Succession
17.
Succession that begins on a bare area such as bare rock, with lichens as pioneers, is:
- A.Primary succession
- B.Secondary succession
- C.Decomposition
- D.Mineralisation
Section B — Challenge / Olympiad (2 marks each)
7 × 2 = 14 marks
18.
Food chains are usually only 4-5 links long mainly because:
- A.So much energy is lost at each level (10% law)
- B.Animals dislike long chains
- C.There is no Sun
- D.Plants are rare
19.
If all decomposers were removed from an ecosystem, the most direct result would be that:
- A.Dead matter and nutrients would not be recycled
- B.More sunlight would arrive
- C.Plants would grow faster
- D.Energy would cycle
20.
The pyramid of energy can never be inverted because:
- A.Energy always decreases from one level to the next
- B.Energy increases upward
- C.Producers have the least energy
- D.Top predators store all energy
21.
Burning fossil fuels adds extra carbon to the air, disturbing the:
- A.Carbon cycle
- B.Food chain length
- C.Number of trophic levels
- D.Sun's output
22.
Protecting forests is important partly because they provide the ecosystem service of:
- A.Releasing oxygen and regulating climate
- B.Making plastic
- C.Producing fossil fuels quickly
- D.Stopping all rain
23.
A pyramid of numbers can sometimes look inverted (e.g. one big tree supporting many insects), but the pyramid of energy stays upright because it measures:
- A.The actual energy, which always falls up the chain
- B.Only the count of organisms
- C.The size of organisms only
- D.Nothing real
24.
Secondary succession (e.g. on an abandoned field) is faster than primary succession because:
- A.Soil is already present
- B.There is no sunlight
- C.There are no seeds anywhere
- D.It needs no producers
Answer Key
Section A — Multiple Choice (1 mark each)
- (A) Ecosystem
- (B) Abiotic components
- (A) Producers
- (B) Herbivores
- (B) Decomposers
- (A) Food chain
- (A) Trophic level
- (A) Food web
- (B) Sun
- (A) 10%
- (A) One-way (does not cycle)
- (A) Upright
- (B) Biogeochemical cycles
- (A) Carbon cycle
- (A) Ecosystem services
- (A) Primary productivity
- (A) Primary succession
Section B — Challenge / Olympiad (2 marks each)
- (A) So much energy is lost at each level (10% law)
- (A) Dead matter and nutrients would not be recycled
- (A) Energy always decreases from one level to the next
- (A) Carbon cycle
- (A) Releasing oxygen and regulating climate
- (A) The actual energy, which always falls up the chain
- (A) Soil is already present
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