Chapter Exam

Chapter 13: Our Environment — Online MCQ Test

Q: Which of the following is a biodegradable substance?

Answer: C. Vegetable peel — Vegetable peels can be broken down by microorganisms into simpler substances, so they are biodegradable.

Q: In a food chain, green plants usually occupy the:

Answer: A. First trophic level — Green plants are producers because they make food by photosynthesis, so they form the first trophic level.

Q: Ozone is a molecule made up of:

Answer: C. Three oxygen atoms — Ozone has the molecular formula O3, meaning it contains three oxygen atoms.

Q: In the food chain grass → deer → tiger, the deer represents the:

Answer: B. Primary consumer — The deer feeds directly on grass, a producer, so it is a primary consumer.

Q: Which of the following correctly represents a food chain?

Answer: B. Grass → Insect → Frog → Snake — Energy flows from producers to herbivores and then to carnivores, so the correct sequence is grass, insect, frog, snake.

Q: A student writes the food chain: grass → grasshopper → frog → snake → eagle. If grass has 10,000 J of energy, how much energy will be available to the frog according to the 10 percent law?

Answer: C. 100 J — Grasshopper gets 10 percent of 10,000 J, which is 1,000 J, and frog gets 10 percent of 1,000 J, which is 100 J.

Q: In the food chain phytoplankton → small fish → large fish → bird, which organism is most likely to show the highest level of a non-biodegradable pesticide?

Answer: D. Bird — Due to biomagnification, pesticide concentration increases at each trophic level and becomes highest in the top consumer.

Q: Consider the food chain: plants → insects → frogs → snakes. If 20,000 J of energy is available in plants, what is the approximate energy available to snakes?

Answer: A. 20 J — Insects get 2,000 J, frogs get 200 J and snakes get 20 J according to the 10 percent law.

SCIENCE · Grade 10 · CBSE(NCERT)

Practice Chapter 13: Our Environment with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 10 SCIENCE. This chapter covers: Ecosystem Food chain Food web Trophic level Biodegradable Non biodegradable Ozone layer Ozone depletion Biomagnification Environmental conservation. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 13: Our Environment — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 10 SCIENCE — Chapter 13: Our Environment, with answers and explanations. These are sample questions; the exam has its own separate question set.

An ecosystem consists of which of the following?

A. Only living organisms in an area
B. Only non-living things in an area
C. Living organisms and their physical environment interacting together ✓
D. Only plants and animals in a forest

Answer: C. Living organisms and their physical environment interacting together
An ecosystem includes biotic components like plants and animals and abiotic components like air, water and soil interacting as a system.

Which of the following is a biodegradable substance?

A. Plastic bag
B. Glass bottle
C. Vegetable peel ✓
D. Aluminium foil

Answer: C. Vegetable peel
Vegetable peels can be broken down by microorganisms into simpler substances, so they are biodegradable.

In a food chain, green plants usually occupy the:

A. First trophic level ✓
B. Second trophic level
C. Third trophic level
D. Fourth trophic level

Answer: A. First trophic level
Green plants are producers because they make food by photosynthesis, so they form the first trophic level.

Ozone is a molecule made up of:

A. One oxygen atom
B. Two oxygen atoms
C. Three oxygen atoms ✓
D. Four oxygen atoms

Answer: C. Three oxygen atoms
Ozone has the molecular formula O3, meaning it contains three oxygen atoms.

In the food chain grass → deer → tiger, the deer represents the:

A. Producer
B. Primary consumer ✓
C. Secondary consumer
D. Decomposer

Answer: B. Primary consumer
The deer feeds directly on grass, a producer, so it is a primary consumer.

Which of the following correctly represents a food chain?

A. Frog → Grass → Insect → Snake
B. Grass → Insect → Frog → Snake ✓
C. Snake → Frog → Insect → Grass
D. Insect → Grass → Frog → Snake

Answer: B. Grass → Insect → Frog → Snake
Energy flows from producers to herbivores and then to carnivores, so the correct sequence is grass, insect, frog, snake.

A student writes the food chain: grass → grasshopper → frog → snake → eagle. If grass has 10,000 J of energy, how much energy will be available to the frog according to the 10 percent law?

A. 10,000 J
B. 1,000 J
C. 100 J ✓
D. 10 J

Answer: C. 100 J
Grasshopper gets 10 percent of 10,000 J, which is 1,000 J, and frog gets 10 percent of 1,000 J, which is 100 J.

In the food chain phytoplankton → small fish → large fish → bird, which organism is most likely to show the highest level of a non-biodegradable pesticide?

A. Phytoplankton
B. Small fish
C. Large fish
D. Bird ✓

Answer: D. Bird
Due to biomagnification, pesticide concentration increases at each trophic level and becomes highest in the top consumer.

A lake contains algae, zooplankton, small fish and large fish. A non-biodegradable pollutant enters the lake water. Which statement is most accurate?

A. The pollutant concentration will be equal in all organisms
B. Algae will always have the highest concentration because they absorb it first
C. Large fish will have the highest concentration due to biomagnification ✓
D. Zooplankton will remove the pollutant completely by digestion

Answer: C. Large fish will have the highest concentration due to biomagnification
Non-biodegradable pollutants accumulate in bodies and increase in concentration at higher trophic levels.

Consider the food chain: plants → insects → frogs → snakes. If 20,000 J of energy is available in plants, what is the approximate energy available to snakes?