Class 8 Science: How Nature Works in Harmony MCQs (NCERT)

110 practice questions on How Nature Works in Harmony, a chapter in the NCERT Class 8 Science textbook. Every question includes a written explanation. Try the samples below - the answer stays hidden until you ask for it.

Sample questions

Q1
hard
If all the decomposers in a forest suddenly vanished, the most likely long-term result would be that
  1. A nothing would change, since decomposers feed only on waste
  2. B dead leaves and remains would pile up and the soil would grow poorer in nutrients
  3. C plants would grow faster, because decomposers would no longer compete with them for food
  4. D every herbivore in the forest would die within a day
Show answer and explanation

Correct answer: B - dead leaves and remains would pile up and the soil would grow poorer in nutrients

Decomposers break down dead matter and hand its nutrients back to the soil, so without them the remains would collect while the soil slowly lost its supply of nutrients. Plants would suffer rather than benefit from that loss. The change would be large, not nothing, but it would build up over months, not kill herbivores in a day.
Q2
easy
Pollination is important for our food supply because
  1. A pollination kills the pests that attack a crop's leaves
  2. B pollination adds nutrients to the soil of a field as pollen falls from the flowers
  3. C many crops form fruits and seeds only after their flowers are pollinated
  4. D pollination supplies water to the growing crop
Show answer and explanation

Correct answer: C - many crops form fruits and seeds only after their flowers are pollinated

Pollen must reach a flower before fruits and seeds can develop, and fruits and seeds are what we harvest from many crops. Watering and feeding the crop are quite separate matters handled by rain, irrigation and manure. Pollination does nothing to control pests.
Q3
medium
Assertion (A): A pond is an example of an ecosystem. Reason (R): Water plants in a pond make their own food using sunlight.
  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: B - Both A and R are true, but R is not the correct explanation of A

Both statements are true. However, a pond counts as an ecosystem because its living things and its water, mud, air and sunlight all interact as one unit, not because of what its plants happen to eat. Food-making by water plants is one activity inside the pond, so R does not explain A.
Q4
medium
Plastic bags thrown into open drains in a town commonly lead to
  1. A more dissolved oxygen in the drain water
  2. B a faster flow of water through the drains
  3. C cleaner drains that need less maintenance
  4. D blocked drains and water logging during heavy rain
Show answer and explanation

Correct answer: D - blocked drains and water logging during heavy rain

Bags collect at bends and gratings and trap other rubbish, so the drain chokes and rainwater backs up into the streets. Adding waste to a drain cannot clean it or speed the flow. Rotting waste in blocked water reduces the oxygen in it rather than adding to it.
Q5
easy
Green plants are called producers because
  1. A they make their own food using sunlight
  2. B they release oxygen only at night
  3. C they take in ready-made food from the soil
  4. D they are rooted in one place
Show answer and explanation

Correct answer: A - they make their own food using sunlight

Producers are organisms that build their own food, and green plants do this using sunlight, water and carbon dioxide. They absorb water and minerals from the soil but not ready-made food. Oxygen is released during the day when food is being made, and staying rooted has nothing to do with the name.
Q6
easy
Non-biodegradable waste is waste that
  1. A breaks down completely within a few days
  2. B is always in liquid form
  3. C cannot be broken down by decomposers
  4. D is always dangerous to touch
Show answer and explanation

Correct answer: C - cannot be broken down by decomposers

The word describes waste that decomposers are unable to break down, so it remains in the soil or water for years. Waste that disappears in a few days is biodegradable instead. Such waste may be solid or liquid, and much of it, such as a glass bottle, is quite safe to handle.

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More Class 8 Science chapters

The Invisible Living World: Beyond Our Naked Eye 112 Health: The Ultimate Treasure 105 Electricity: Magnetic and Heating Effects 110 Exploring Forces 115 Pressure, Winds, Storms, and Cyclones 115 Particulate Nature of Matter 100 Nature of Matter: Elements, Compounds, and Mixtures 110 The Amazing World of Solutes, Solvents, and Solutions 110 Light: Mirrors and Lenses 116 Our Home: Earth, a Unique Life Sustaining Planet 105