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Class 10 Science Chapter 13: Our Environment MCQs with answers

10 multiple-choice questions on Our Environment, each with its answer and the reason, written from the NCERT chapter. Open a question's solution to check your working; then take the free test to find your next chapter.

Question 1
A student surveying a village pond in Assam records the following. Which of them is an abiotic component of the pond?
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Answer: (c) dissolved minerals

Minerals are a physical factor, an abiotic component; the plant, tadpoles and bacteria are living, so biotic.

Question 2
Which of these is a human-made ecosystem?
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Answer: (d) a paddy field in Punjab

Crop-fields are human-made ecosystems; swamps, lakes and natural grasslands are natural ones.

Question 3
On a rocky seashore in Ratnagiri, the organisms that make sugar from inorganic substances using sunlight are the
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Answer: (c) seaweeds

Seaweeds are green, carry chlorophyll and photosynthesise, so they are producers. Crabs and snails are consumers; fungi are decomposers.

Question 4
A fallen log in the Western Ghats crumbles over a few years and disappears into the forest floor. The organisms chiefly responsible are
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Answer: (c) fungi and bacteria

Decomposers, the bacteria and fungi, break down dead remains. Deer and boar are herbivores or omnivores, algae are producers, and woodpeckers feed on insects.

Question 5
When decomposers act on the dead leaves under a mango tree, the substances they return to the soil are
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Answer: (a) simple inorganic substances that plants take up again

Decomposers break complex organic matter into simple inorganic substances which go into the soil and are used again by plants. Starch is what they break down, not what they return.

Question 6
In the sea food chain phytoplankton → zooplankton → sardine → tuna, the sardine occupies the
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Answer: (b) third trophic level

Phytoplankton are producers (first), zooplankton herbivores (second), the sardine feeds on them and is at the third level; tuna is fourth.

Question 7
A tapeworm living in the intestine of a dog draws its food from the dog. As a consumer it is classed as a
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Answer: (b) parasite

It feeds on a living host without killing it at once, so it is a parasite, one of the four kinds of consumer.

Question 8
In a farm food chain paddy → rat → snake → eagle, the tertiary consumer is the
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Answer: (a) eagle

Paddy is the producer, the rat the primary consumer, the snake the secondary consumer and the eagle, the larger carnivore at the fourth level, the tertiary consumer.

Question 9
When a neem tree makes food, the energy change that takes place in its leaves is
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Answer: (b) light energy to chemical energy

Autotrophs capture the energy of sunlight and convert it into chemical energy stored in food.

Question 10
About 50 000 J of sunlight falls on the leaves of a sugarcane crop in a day. The food energy the crop makes from it is closest to
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Answer: (a) 500 J

Terrestrial green plants capture about 1% of the sunlight falling on their leaves: 1% of 50 000 J = 500 J. 5000 J applies the 10% rule by mistake.

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