CBSE Class 9 · Life on Earth

Biomes Class 9: Terrestrial and Aquatic Biomes and the Biome Pyramid

Updated 17 October 2026 · Fact-checked

A biome is a large natural region where certain plants and animals live under similar climatic conditions. Terrestrial biomes are forest, grassland, desert and tundra; aquatic biomes are freshwater and marine and cover about three-fourths of the Earth. Temperature, precipitation, dominant plants and growth forms decide a biome, and a biome pyramid shows how energy, number and biomass decrease from producers to top predators.

Understand Biomes: Terrestrial, Aquatic and the Biome Pyramid

What is a biome? The Earth is like a patchwork quilt and each patch is a biome, from Greek *bios* (life). A biome is a large natural region with plants and animals living under similar climatic conditions. An ecosystem is a smaller neighbourhood inside a biome, such as a pond, a grove or a patch of grassland, where living things and their non-living surroundings interact. What decides a biome: temperature, precipitation patterns, dominant plant species and the growth forms of vegetation. The world map also shows the taiga (coniferous forests) and the temperate deciduous biome (broad-leaved trees that shed leaves seasonally).

Terrestrial biomes.

Forest (tropical rainforest): near the Equator between the Tropics (23.5 degrees N to 23.5 degrees S); hot and wet all year. Largest in the Amazon Basin, Congo Basin and South-East Asia; smaller in Central America and India's Andaman and Nicobar Islands and North-East. It is a "gene bank" of biodiversity, maintains oxygen and balances climate. Layers from top to bottom: emergent layer, upper canopy, understory (lower canopy) and forest floor.
Grassland: open land with grass and few trees, with moderate rainfall too little for dense forest. *Temperate* grasslands (prairies, steppes) are fertile and often farmed; *tropical* grasslands (savannas) have scattered trees and animals such as lions, elephants and giraffes.
Desert: the driest biome; hot (Sahara) or cold (Gobi). The Rann of Kutch is one of the world's largest salt deserts, marshy in the monsoon and white salt in the dry season. Cacti store water in their stems, while camels, lizards and snakes survive the heat and scarce water by conserving water (for example scaly skin, burrowing, little water loss, and fat storage in camels).
Tundra: the coldest biome, near the Arctic and Antarctic, with long winters and short summers. Permafrost (frozen soil) stops trees; mosses, lichens and small shrubs grow. Reindeer, arctic foxes and polar bears live there; it is very fragile.

Aquatic biomes cover about three-fourths of the Earth's surface.

Freshwater: rivers, lakes, ponds and wetlands; vital for agriculture and drinking water.
Marine: oceans, seas and coral reefs; rich biodiversity; they store and distribute heat, influencing climate, and give food and livelihoods to millions.

The biome pyramid. A diagram of relationships among organisms in terms of energy, number or biomass: producers (plants, algae) at the base capture solar energy by photosynthesis; above them come herbivores (primary consumers), carnivores (secondary consumers) and top predators (tertiary consumers). Going up, number, biomass and energy decrease, because energy is lost as heat at each level during metabolism.

Biomes: Terrestrial, Aquatic and the Biome Pyramid: key facts

Biome definition: Large natural region
Similar climate
Characteristic plants and animals; From Greek bios.
What decides a biome: Temperature
Precipitation patterns
Dominant plant species
Growth forms of vegetation; Four factors.
Terrestrial and aquatic: Terrestrial: forest, grassland, desert, tundra | Aquatic: freshwater, marine; Aquatic is about three-fourths of Earth.
Rainforest layers: Emergent
Upper canopy
Understory
Forest floor; Top down.
Biome pyramid: Producers
Herbivores
Carnivores
Top predators
Energy, number and biomass fall upward; Energy lost as heat.

How to answer Biomes: Terrestrial, Aquatic and the Biome Pyramid questions

Questions ask you to define biome and ecosystem, match features to biomes, describe rainforest layers, explain the pyramid and relate climate to biome type.

1Define biome first and then the difference from an ecosystem (large region versus small neighbourhood).
2For a biome description, give location, climate, vegetation, animals and one importance.
3For the pyramid, name the four levels bottom to top and say why quantities fall.
4For a numerical, follow the pyramid logic: each higher level has less than the one below it.
5Link to people or conservation in the conclusion.

Biomes: Terrestrial, Aquatic and the Biome Pyramid in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

A school pond and a biome

Suppose a class studies a small pond in the school garden and another class studies the whole region's forest.

Which is an ecosystem and which is a biome? Why?

Try it first, then show the solutionSolution

The pond is a small neighbourhood where living things and surroundings interact: an ecosystem.
The region's forest, with similar climate and plants over a large area, is a biome.
A biome can contain many ecosystems.

Answer: The pond is an ecosystem; the larger forest region is a biome. A biome is large and defined by a similar climate, while an ecosystem is a smaller neighbourhood inside it.

Memory hook: Biome is the big quilt patch; ecosystem is the stitch.

A made-up energy count

Suppose in a meadow the plants capture 10,000 units of energy, the grasshoppers hold 1,000 units, the frogs 100 and the snakes 10.

What does this show about the biome pyramid?

Try it first, then show the solutionSolution

Energy falls at every higher level.
Energy is lost as heat in metabolism.
So there can be only a few top predators.

Answer: The numbers fall at each level, as in the biome pyramid, because energy is lost as heat at each step; so few top predators are supported. These figures are invented to illustrate the idea.

Memory hook: Each step up has less.

Tricks to remember Biomes: Terrestrial, Aquatic and the Biome Pyramid

Short memory aids. Say each one aloud once, then use it on a question the same day.

Four land biomes: F-G-D-T
Forest, Grassland, Desert, Tundra.
Use it when: Terrestrial biomes.
Rainforest layers: E-U-U-F
Emergent, Upper canopy, Understory, Floor.
Use it when: Top to bottom.
Pyramid: P-H-C-T
Producers, Herbivores, Carnivores, Top predators.
Use it when: Bottom to top.

Biomes: Terrestrial, Aquatic and the Biome Pyramid: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Which biome? · 1 mark · MCQBoard level

Permafrost, mosses and reindeer are found in which biome?
(a) Tundra
(b) Rainforest
(c) Savanna
(d) Marine

Try it first, then show the solutionSolution

Permafrost and lichens belong to tundra (1 mark).

Answer: (a) Tundra

Example 2: Biome and ecosystem (2 marks) · 2 marks · Very short answerBoard level

Distinguish between a biome and an ecosystem. (2 marks)

Try it first, then show the solutionSolution

Biome: large natural region with similar climate and typical plants and animals (1 mark).
Ecosystem: smaller neighbourhood such as a pond, where living and non-living things interact (1 mark).

Answer: A biome is a large natural region where certain plants and animals live under similar climatic conditions. An ecosystem is a smaller neighbourhood within a biome, such as a pond or grove, where living things and their non-living surroundings interact.

Example 3: Rainforest (3 marks) · 3 marks · Short answerHarder board level

Where are tropical rainforests found, and why are they called a "gene bank"? Name the four layers from top to bottom. (3 marks)

Try it first, then show the solutionSolution

Near the Equator between the Tropics, hot and wet all year; e.g. Amazon Basin, Congo Basin (1 mark).
Richest biodiversity, so a gene bank (1 mark).
Layers: emergent, upper canopy, understory, forest floor (1 mark).

Answer: Tropical rainforests lie near the Equator between the Tropics and are hot and wet throughout the year; the Amazon Basin and the Congo Basin are examples. They hold the richest store of biodiversity, so they are called a gene bank. The layers from top to bottom are the emergent layer, upper canopy, understory and forest floor.

Example 4: Assertion-reason: pyramid · 1 mark · Assertion-reasonHarder board level

Assertion (A): There are fewer top predators than herbivores in a biome.
Reason (R): Energy is lost as heat at each level, so less energy remains for higher levels.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Try it first, then show the solutionSolution

Energy decreases up the pyramid, which limits numbers at higher levels (1 mark).

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Example 5: Compare two biomes (5 marks) · 5 marks · Long answerHOTS / competency

Compare desert and tundra on climate, vegetation, animals and one threat or fragility. (5 marks)

Try it first, then show the solutionSolution

Desert: driest, hot (Sahara) or cold (Gobi); tundra: coldest, near the poles, long winters (1 mark).
Vegetation: desert cacti and shrubs; tundra mosses, lichens, small shrubs; permafrost stops trees (1 mark).
Animals: camels, lizards, snakes; reindeer, arctic foxes, polar bears (1 mark).
Adaptation: desert plants store or conserve water and animals conserve water and withstand heat, versus cold tolerance in tundra (1 mark).
Tundra is very fragile; deserts may hold minerals and oil (1 mark).

Answer: A desert is the driest biome, hot like the Sahara or cold like the Gobi, whereas the tundra is the coldest biome near the poles with long winters and short summers. Deserts have cacti and shrubs, while permafrost in the tundra stops trees and allows only mosses, lichens and small shrubs. Camels, lizards and snakes live in deserts; reindeer, arctic foxes and polar bears live in the tundra. Desert plants store or conserve water and animals conserve water and withstand heat, while tundra life copes with cold. The tundra is very fragile, and deserts may contain minerals and oil.

Example 6: Case: the Rann · 4 marks · Case-basedHOTS / competency

Read the case and answer the questions.

A geography class reads that the Rann of Kutch is marshy during the monsoon and covered with white salt in the dry season. A student says it cannot be a desert because deserts must be sandy and hot.

(i) Which biome does the Rann belong to? (1)
(ii) Is the student right that all deserts are hot? Give one example from the chapter. (1)
(iii) Name two ways in which desert life copes with scarce water. (2)

Try it first, then show the solutionSolution

(i) Desert, one of the world's largest salt deserts (1 mark).
(ii) No; cold deserts like the Gobi exist (1 mark).
(iii) Any two water-related ways: cacti (plants) store water in their stems; animals conserve water, for example through scaly skin, burrowing or being active at night (2 marks).

Answer: (i) It is a desert, one of the largest salt deserts in the world. (ii) The student is wrong; deserts may be hot, like the Sahara, or cold, like the Gobi. (iii) Cacti store water in their stems, and desert animals such as lizards and snakes conserve water, for example by having scaly skin, burrowing or being active at night, so they can cope with scarce water.

Where students lose marks in Biomes: Terrestrial, Aquatic and the Biome Pyramid

The slips examiners see most often, and what to write instead.

Mistake: Confusing biome and ecosystem
Treating them as synonyms.
Wrong working
A biome is a pond.
Right working
A pond is an ecosystem; a biome is a large region.
Do this: Large versus small.
Usually costs: 1 mark.
Mistake: Layers in wrong order
Starting from the ground.
Wrong working
Forest floor, understory, canopy, emergent (labelled as top-down).
Right working
Top-down: emergent, upper canopy, understory, forest floor.
Do this: State "top to bottom".
Usually costs: 1 mark.
Mistake: Calling all deserts hot
Ignoring cold deserts.
Wrong working
Deserts are always hot.
Right working
Deserts may be hot (Sahara) or cold (Gobi).
Do this: Give both.
Usually costs: 1 mark.
Mistake: Pyramid explanation missing heat loss
Stating only that numbers fall.
Wrong working
Fewer predators because they are strong.
Right working
Energy is lost as heat at each level.
Do this: Quote the energy reason.
Usually costs: 1-2 marks.

Exam tips

Learn the four biome factors: temperature, precipitation, dominant plants and growth forms.
For each biome write location, climate, plants, animals and a significance line.
When using numbers for the pyramid, say that they are illustrative.
Name specific places from the chapter: Amazon Basin, Congo Basin, Sahara, Gobi, Rann of Kutch.

Practice questions on Biomes: Terrestrial, Aquatic and the Biome Pyramid

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which biome covers about three-fourths of the Earth's surface?
(a) Terrestrial
(b) Aquatic
(c) Tundra
(d) Grassland
Hint
Water.
Answer
(b) Aquatic
Q2 · 2 marks · Very short answerBoard level
Name the two types of aquatic biomes and give one example of each. (2 marks)
Hint
Fresh and marine.
Answer
Freshwater, such as rivers, lakes or ponds, and marine, such as oceans, seas or coral reefs.
Q3 · 3 marks · Short answerHarder board level
Differentiate between temperate and tropical grasslands with examples. (3 marks)
Hint
Prairies, savannas.
Answer
Temperate grasslands, such as the prairies of North America and the steppes of Asia, have fertile soil and are often farmed. Tropical grasslands, or savannas, as in Africa, have scattered trees and animals such as lions, elephants and giraffes. Both receive moderate rainfall, too little for dense forest.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Tundra is a fragile biome.
Reason (R): Permafrost and a very short summer limit plant growth and make recovery slow.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Hint
Frozen soil.
Answer
(a) Both A and R are true, and R is the correct explanation of A.
Q5 · 5 marks · Long answerHarder board level
Explain the biome pyramid with a diagram description and say why numbers, biomass and energy decrease upward. (5 marks)
Hint
Producers to tertiary consumers; energy lost as heat.
Answer
The biome pyramid shows relationships among organisms in terms of energy, number or biomass. At the base are producers such as plants and algae that capture solar energy by photosynthesis. Above them are herbivores (primary consumers), then carnivores (secondary consumers) and at the top the top predators (tertiary consumers). Number, biomass and energy decrease at each level going up because energy is lost as heat during metabolism, leaving less for the next level. So a biome supports many producers but few top predators.
Q6 · 3 marks · Short answerHOTS / competency
Suppose a forest in a hot, wet region is cleared and replaced by a farm. Using what you know about rainforests, list two likely losses and explain which layers would be affected most. (3 marks)
Hint
Gene bank; layers.
Answer
Likely losses are biodiversity (the gene bank) and the role in maintaining oxygen and balancing climate. The emergent layer and upper canopy, which hold the tallest trees and much of the life, are removed first, followed by the understory and forest floor communities that depend on their shade and food.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What does "biome" come from?Show answer
The Greek word bios, meaning life.
2.What is permafrost?Show answer
Permanently frozen soil that prevents trees in the tundra.
3.Which are the terrestrial biomes?Show answer
Forest, grassland, desert and tundra.
4.Name the producers in a biome pyramid.Show answer
Plants and algae.
5.What fraction of Earth do aquatic biomes cover?Show answer
About three-fourths.

Biomes: Terrestrial, Aquatic and the Biome Pyramid: frequently asked questions

What is a biome?

A large natural region where certain plants and animals live under similar climatic conditions.

What are the types of terrestrial biomes?

Forest, grassland, desert and tundra.

What are the layers of a rainforest?

Emergent layer, upper canopy, understory and forest floor.

Why do energy and numbers fall in a biome pyramid?

Because energy is lost as heat at each level during metabolism.