Samacheer Kalvi Class 9 Social Science Solutions Chapter 5 Biosphere

Get the most accurate TN Board Solutions for Class 9 Social Science Chapter 05 Biosphere here. Updated for the 2026-27 academic session, these solutions are based on the latest TN Board textbooks for Class 9 Social Science. Our expert-created answers for Class 9 Social Science are available for free download in PDF format.

Detailed Chapter 05 Biosphere TN Board Solutions for Class 9 Social Science

For Class 9 students, solving TN Board textbook questions is the most effective way to build a strong conceptual foundation. Our Class 9 Social Science solutions follow a detailed, step-by-step approach to ensure you understand the logic behind every answer. Practicing these Chapter 05 Biosphere solutions will improve your exam performance.

Class 9 Social Science Chapter 05 Biosphere TN Board Solutions PDF

I. Choose the Correct Answer

 

Question 1. The coldest biome on Earth is
(a) Tundra
(c) Desert
(d) Oceans
Answer: (a) Tundra
In simple words: The Tundra is the coldest place on Earth with very little plant growth, making it the chilliest type of natural environment.

🎯 Exam Tip: Remember key features of biomes like temperature, rainfall, and dominant plant/animal life to correctly identify them.

 

Question 2. This is the smallest unit of biosphere
(a) Ecosystems
(b) Biome
(c) Environment
(d) None of the options
Answer: (d) Ecosystems
In simple words: An ecosystem is the smallest part of the biosphere where living things and their non-living surroundings interact. It is a complete working unit.

🎯 Exam Tip: Understand the hierarchy of ecological organization, starting from individual organisms to the entire biosphere.

 

Question 3. Nutrients are recycled in the atmosphere with the help of certain micro organisms, referred to as
(a) Producers
(b) Decomposers
(c) Consumers
(d) None of the options
Answer: (b) Decomposers
In simple words: Tiny living things like bacteria and fungi break down dead matter. This process helps nutrients go back into the soil and air so other plants and animals can use them again.

🎯 Exam Tip: Knowing the roles of producers, consumers, and decomposers is crucial for understanding nutrient cycles.

 

Question 4. To which climatic conditions are Xerophytic plants specifically adapted to?
(a) Saline and sandy
(c) Cold temperature
(d) Humid
Answer: (a) Saline and sandy
In simple words: Xerophytic plants are special plants that can live in dry places where the soil is salty and sandy, like deserts. They have adaptations to save water.

🎯 Exam Tip: Connect plant adaptations to their specific environmental conditions, like xerophytes in dry, salty areas.

 

Question 5. Why is the usage of rainforest biomes for large scale agriculture unsustainable?
a) because it is too wet.
b) because the temperature is too warm,
c) because the soil is too thin.
d) because the soil is poor.
Answer: (d) because the soil is poor
In simple words: Rainforest soils are usually not very rich in nutrients because most of the goodness is held in the plants themselves. So, using them for big farms is not a good idea in the long run.

🎯 Exam Tip: Understand that rainforest soils often lack nutrients because rapid decomposition quickly recycles them into vegetation, making them unsuitable for long-term agriculture.

 

Questions 6-8 are assertion type questions. Directions :
(a) Both assertion (A) and reason(R) are true; R explains A
(b) Both assertion(A) and reason(R) are true; R does not explain A
(c) A is true; R is false
(d) Both A and R are false

 

Question 6. A: Heterotrophs do not produce their own food. R: They depend on autotrophs for their nourishment.
Answer: (a) Both assertion (A) and reason(R) are true; R explains A
In simple words: Heterotrophs are creatures that cannot make their own food, so they must eat other living things, like autotrophs, to get energy. This explains why they cannot make their own food.

🎯 Exam Tip: Remember that heterotrophs (consumers) rely on autotrophs (producers) for food, making the reason a direct explanation of the assertion.

 

Question 7. A: Hotspots are the regions characterised by numerous endemic plants and animal species living in a vulnerable environment.
Answer: (a) Both assertion (A) and reason(R) are true; R explains A
In simple words: Hotspots are special places with many unique plants and animals that are found nowhere else, and they are also in danger. Researchers study them to help protect them more effectively.

🎯 Exam Tip: Focus on the definition of biodiversity hotspots: high biodiversity (especially endemic species) combined with significant threat.

 

Question 8. A: The number of gorillas in Africa has plummeted by 60% in the past twenty years. R : Non intervention of human beings in the forest areas.
Answer: (c) A is true; R is false
In simple words: It is true that gorilla numbers have fallen greatly. However, the reason given is wrong, as human actions like hunting and destroying forests are actually causing the decline, not a lack of human interference.

🎯 Exam Tip: Carefully evaluate both the assertion and the reason, and then consider if the reason accurately explains the assertion, especially in scenarios involving human impact on wildlife.

II. Fill in the Blanks

 

Question 1. An area where animals, plants and micro organisms live and interact with one another is known ___________
Answer: Eco System
In simple words: An ecosystem is a place where all living things, from big animals to tiny germs, live and work together with their environment.

🎯 Exam Tip: Understand that an ecosystem describes the interconnectedness of living organisms and their non-living surroundings.

 

Question 2. ___________ are also called Heterotrophs.
Answer: consumers
In simple words: Consumers are living things that eat other organisms for energy, which is why they are called heterotrophs.

🎯 Exam Tip: Clearly differentiate between producers (autotrophs) and consumers (heterotrophs) based on how they obtain food.

 

Question 3. The chain of transformation of energy from one group of organisms to another through various trophic levels is called a ___________
Answer: Food web
In simple words: A food web shows how energy moves between different living things in an ecosystem, with many feeding connections. It's like many food chains linked together.

🎯 Exam Tip: While food chains show a single path of energy, a food web illustrates the complex, interconnected feeding relationships.

 

Question 4. ___________ is an extensive large ecosystem.
Answer: A Biome
In simple words: A biome is a very large area on Earth that shares similar weather, plants, and animals, like a big ecosystem.

🎯 Exam Tip: Biomes are major ecological regions characterized by dominant vegetation and climate, covering vast areas.

 

Question 5. The vegetative type commonly found in desert biomes is called ___________
Answer: Xerophytes
In simple words: Plants that live in deserts are called xerophytes because they are specially built to survive with very little water.

🎯 Exam Tip: Relate the term 'xerophyte' directly to plants adapted for dry, desert environments, recalling their unique features.

 

Question 6. ___________ is an aquatic biome that is found where freshh water and salt water mix
Answer: water mix
In simple words: Estuaries are special watery places where fresh river water meets salty ocean water, creating a unique environment.

🎯 Exam Tip: Identify estuaries as crucial transitional zones where freshwater and saltwater habitats meet, supporting unique biodiversity.

III. Answer the following in brief

 

Question 1. What is Biosphere?
Answer: The biosphere is the part of Earth where life exists. It covers the Earth's surface and includes the land (Lithosphere), water (Hydrosphere), and air (Atmosphere). All plants and animals that live on or near the Earth's surface are part of the biosphere. It's like a thin layer of life wrapped around our planet.
In simple words: The biosphere is the part of Earth where all living things, like plants, animals, and humans, can be found. It includes land, water, and air.

🎯 Exam Tip: Define the biosphere as the zone of life on Earth, encompassing all ecosystems and interacting with the lithosphere, hydrosphere, and atmosphere.

 

Question 2. What is an ecosystem?
Answer:
1. An ecosystem is a group of living things that interact with each other and their non-living surroundings, like land, soil, air, and water. This interaction forms a community.
2. Ecosystems can be very tiny, like the life on a tree bark, or very large, like the whole Earth (ecosphere). Examples include croplands, ponds, forests, and deserts.
3. The biosphere contains all of Earth's ecosystems and supports all forms of life, including people. This makes it a complex and vital system.
In simple words: An ecosystem is a place where living things (plants, animals) and non-living things (soil, air, water) work together. They can be small, like a tree's bark, or huge, like a whole desert.

🎯 Exam Tip: When defining an ecosystem, always mention both biotic (living) and abiotic (non-living) components and their interactions.

 

Question 3. What does the term 'biodiversity" mean?
Answer: Biodiversity, or biological diversity, means the huge variety of different living organisms, such as plants, animals, and tiny microbes, that live in a specific place. It is greatly affected by the land's features, climate, and human actions. A rich variety of life forms helps an ecosystem stay healthy and balanced.
In simple words: Biodiversity means having many different kinds of plants, animals, and tiny living things in one area.

🎯 Exam Tip: Emphasize "variety of life" and mention the main types of organisms (plants, animals, microorganisms) for a complete definition.

 

Question 4. What is meant by loss of bio diversity?
Answer:
1. When species of plants and animals disappear because of human actions or natural events, this is called loss of biodiversity. This is a very serious issue for our planet.
2. This loss greatly impacts people and also harms land, water, and air.
3. Destroying habitats by cutting down forests, a growing population, pollution, and global warming are the main reasons for this loss.
4. Sometimes, habitats are lost so quickly or severely that an entire species vanishes from Earth forever. The loss of a single species can affect the entire food web.
In simple words: Loss of biodiversity means when many different kinds of plants and animals disappear from Earth. This happens because of things like cutting down forests, pollution, and climate change.

🎯 Exam Tip: When explaining biodiversity loss, link it to the extinction of species and connect it to major human-caused environmental problems.

 

Question 5. Mention the various terrestrial biomes.
Answer: The main land-based biomes around the world are:
1. Tropical Forest Biomes
2. Tropical Savanna Biomes
3. Desert Biomes
4. Temperate Grassland Biomes
5. Tundra Biomes
Each of these biomes has unique climate, vegetation, and animal life.
In simple words: The main types of land environments are Tropical Forests, Savannas, Deserts, Temperate Grasslands, and Tundra.

🎯 Exam Tip: Memorize the common names of the terrestrial biomes and be ready to briefly describe each if asked.

IV. Give reasons for the following

 

Question 1. Producers are also called autotrophs
Answer: Producers are called autotrophs because they are parts of the ecosystem that can create their own food. They can be found in both land and water environments. For example, plants, algae, and certain bacteria are all producers. They use sunlight or chemicals to make food.
In simple words: Producers are called autotrophs because they make their own food, like plants using sunlight.

🎯 Exam Tip: The key to defining autotrophs is their ability to produce their own food, usually through photosynthesis.

 

Question 2. Biosphere provides a stable ecosystem.
Answer:
1. Ecosystems vary in size, from tiny units that can support life, like a tree bark, to the entire global ecosystem or ecosphere.
2. The biosphere holds all the Earth's ecosystems and supports all forms of life, including humans. This interconnectedness allows the biosphere to provide a stable ecosystem. The balance between different parts helps keep it stable.
In simple words: The biosphere helps keep nature stable because it has all the Earth's ecosystems and supports all life, connecting everything.

🎯 Exam Tip: Emphasize the biosphere's role as the overarching system that integrates all ecosystems, leading to global stability.

V. Distinguish between the following.

 

Question 1. Producers and Decomposers.
Answer:
Producers:
1. Producers are the parts of the ecosystem that make their own food.
2. They are also known as autotrophs.
3. They live on both land and in water. Examples include plants, algae, and bacteria. Plants use sunlight to create food.
Decomposers:
1. Decomposers are organisms that cannot make their own food.
2. They get their energy by living on dead and decaying plants and animals.
3. Because of this, they are called saprotrophs. Examples include fungi and mushrooms. They help recycle nutrients back into the ecosystem.
In simple words: Producers make their own food, like plants. Decomposers eat dead plants and animals, like fungi, to break them down.

🎯 Exam Tip: For distinctions, always provide clear, contrasting points for each category, defining their roles in energy flow.

 

Question 2. Terrestrial biomes and Aquatic biomes.
Answer:
Terrestrial biomes:
1. Terrestrial biomes are groups of living organisms that interact and live on land.
2. Their conditions are mainly decided by temperature and rainfall. Forests, grasslands, and deserts are examples.
3. Some major terrestrial biomes globally are Tropical Forest Biomes, Tropical Savanna Biomes, Desert Biomes, Temperate Grassland Biomes, and Tundra Biomes. These cover vast areas of land.
Aquatic biomes:
1. Aquatic biomes are groups of living organisms that interact and live in water. They rely on their water environment for food and safety.
2. Just like land biomes, aquatic biomes are shaped by non-living factors like water temperature, saltiness, and light.
3. They are broadly divided into freshwater biomes and marine biomes. Aquatic biomes are crucial for the global water cycle.
In simple words: Terrestrial biomes are places where living things live on land, affected by how hot it is and how much it rains. Aquatic biomes are places where living things live in water, affected by things like water temperature and saltiness.

🎯 Exam Tip: Highlight the primary medium (land vs. water) and the key abiotic factors (temperature/rainfall for terrestrial, water properties for aquatic) that define each biome type.

 

Question 3. Tropical vegetation and Desert vegetation.
Answer:
Tropical vegetation:
1. Tropical forests have the most diverse life forms and produce the most energy among all land biomes. This high productivity supports many species.
2. These areas have very thick forests.
3. Important trees found here include rubber, bamboo, and ebony.
Desert vegetation:
1. Because there is very little rainfall and dry conditions, these areas do not have much vegetation, but they do have a special type of plant called xerophytes.
2. Since the soil is sandy and salty, deserts are not good for farming.
3. You can find drought-resistant thorny bushes, scrubs, and palm trees here. These plants have adapted to survive with minimal water.
In simple words: Tropical areas have thick, diverse forests with trees like rubber. Deserts have very little plant life, mostly thorny bushes and palms, because it's dry and sandy.

🎯 Exam Tip: Focus on the differences in density, type, and adaptations of plants in response to the distinct climatic conditions (wet and hot vs. dry and arid).

 

Question 4. Savannas and Tundra.
Answer:
Savannas:
1. Tropical savannas are usually found between tropical forests and deserts.
2. These biomes are located between 10° to 20° North and South latitudes.
3. Savanna biomes are generally hot and dry, receiving moderate to low rainfall. This climate supports specific types of grass.
4. The grass that grows here is tall and sharp.
Tundra:
1. Tundra lowlands are found in places where the ground stays frozen all year.
2. These regions include Greenland, the Arctic and Antarctic, and northern parts of Asia and Canada. Permafrost defines this biome.
3. These areas are also known as barren lands because little can grow there.
4. The tundra experiences long, harsh winters and short, cool summers. Plants here are typically low-growing.
In simple words: Savannas are hot, dry grasslands with tall grass, found between forests and deserts. Tundras are very cold places with frozen ground and short summers, found in polar regions.

🎯 Exam Tip: Distinguish savannas by their hot, dry climate and tall grasses, and tundra by its permafrost, cold temperatures, and short growing season.

VI. Answer the following in a paragraph

 

Question 1. Explain the various components of the ecosystem.
Answer: An ecosystem is a community where all living things interact with each other and with their non-living surroundings like land, soil, air, and water. Ecosystems range from tiny units, like the life on a tree bark, to the whole global ecosystem. The biosphere contains all Earth's ecosystems and supports all life. Ecosystems are made of three basic parts:
A) Abiotic Components: These are the non-living parts of the environment. They include inorganic, physical, and chemical factors like land, air, water, calcium, and iron. These factors determine what kind of life can exist there.
B) Biotic Components: These are the living parts, including plants, animals, and microorganisms. Biotic components are further divided into three types:
• Producers are self-nourishing parts that make their own food, like plants and algae. They are also called autotrophs.
• Consumers are organisms that depend on producers (or other consumers) for food, directly or indirectly. They are called heterotrophs.
• Decomposers break down dead organic matter, recycling nutrients. They are crucial for maintaining soil fertility.
C) Energy Components: All living things in the biosphere use energy. The Sun is the main source of energy for the entire biosphere. Solar energy changes into other forms as it moves through the ecosystem's parts. Producers, consumers, and decomposers all play a big part in how energy flows through an ecosystem.
In simple words: An ecosystem has three main parts: non-living things like land and water (abiotic), living things like plants and animals (biotic), and energy, mostly from the sun, that moves through all of them.

🎯 Exam Tip: When explaining ecosystem components, clearly define and provide examples for abiotic, biotic (producers, consumers, decomposers), and energy flow, highlighting their interdependence.

 

Question 2. Write a paragraph on the functions of an ecosystem.
Answer:
1. Living organisms in an ecosystem form an interacting group of plants and animals. These are organized into different feeding levels, creating food chains and food webs.
2. An ecosystem works by having energy flow through it. This energy flow helps spread and move organic and inorganic matter within the ecosystem.
3. Energy generally moves in a step-by-step order through different levels in an ecosystem. This is a fundamental process for life.
4. These different levels are called trophic levels, showing who eats whom.
5. A food chain is the path of energy transfer from one group of organisms to another through various trophic levels.
6. Many interconnected and dependent food chains form a food web. This complex web ensures stability and nutrient cycling.
In simple words: An ecosystem works by moving energy and matter around. Living things form food chains and food webs, where energy passes from one level to the next, like a big, connected system.

🎯 Exam Tip: Focus on the two main functions of an ecosystem: energy flow and nutrient cycling, and explain how food chains and food webs are integral to these processes.

 

Question 3. Explain about the aquatic biomes on Earth.
Answer: An aquatic biome is a community of living things that interact with each other and their water environment to get nutrients and shelter. Just like land biomes, water biomes are shaped by non-living factors. They are broadly divided into freshwater biomes and marine biomes.
A. Freshwater Biomes: These include lakes, ponds, rivers, streams, and wetlands. Various non-living factors like water volume, flow, oxygen levels, and temperature influence them. Humans rely on freshwater biomes for drinking, farming, and sanitation. Common plants include water lilies and lotus, while animals include trout, salmon, turtles, and crocodiles. These biomes are vital for human survival.
B. Marine Biomes: These are the largest water biomes on Earth, made of continuous bodies of saltwater. They offer a wide variety of places for marine plants and animals to live. Coral reefs are another type of marine biome in the ocean. Estuaries, where salt and fresh water mix, form unique marine biomes. Water allows marine organisms to move easily, helping nutrients circulate faster than in land biomes. Besides animals, plants like kelp, algae, and phytoplankton also grow in water. Aquatic biomes are important for both plants, animals, and humans, providing water, food, and recreation. However, overfishing, pollution, and rising sea levels threaten these biomes. Protecting them is critical for planetary health.
In simple words: Aquatic biomes are water environments where living things interact. They are either freshwater (like rivers) or saltwater (like oceans). They are very important for plants, animals, and people, but they are also facing threats like pollution.

🎯 Exam Tip: Differentiate freshwater and marine biomes by their water type and key examples, and discuss their ecological importance as well as human impacts and threats.

VII. Find out the dates for the following

 

Question 1.
1. World Wild Life Day - ___
2. International Day of Forest – ___
3. World Water Day – ___
4. Earth Day – ___
5. World Environment Day – ___
6. World Oceans Day – ___
Answer:
1. 3rd March
2. 21st March
3. 22nd March
4. 22nd April
5. June 5th
6. 8th June
These days are observed globally to raise awareness about environmental issues and the importance of conservation.
In simple words: These are special days when people around the world learn about and try to protect wildlife, forests, water, Earth, the environment, and oceans.

🎯 Exam Tip: Memorize these important environmental dates, as they are often asked in general knowledge or environmental awareness sections.

VIII. Map Study

 

Question 1. Locate the following on the world outline map.
1. Prairies
2. Downs
3. Tundra Biomes
4. Equatorial Biomes

Answer: A forest ecosystem is a big area of land covered with many trees and other woody plants, filled with different kinds of animals. There are three main types of forests: tropical rain forests, deciduous forests, and coniferous forests. Tropical rain forests are found near the Earth's middle line (equator) and are always warm. It rains almost every day there, and many animals live in its different layers. Deciduous forests have trees that drop their leaves in autumn; these areas have rich soil, warm summers, and cold winters. Animals like worms, snails, spiders, raccoons, rabbits, and squirrels are common here; some animals sleep through winter or fly to warmer places. Coniferous forests have evergreen trees with needles or scales, found in places with long winters and moderate to high rainfall. Understanding these ecosystems helps us appreciate the diverse life forms and their interactions with the environment.
In simple words: A forest ecosystem is a big area with trees and animals. There are different types like rain forests (always warm and wet), deciduous forests (trees lose leaves in autumn), and coniferous forests (needle trees, long winters). Each type has special plants and animals.

🎯 Exam Tip: When describing ecosystems, always mention the key characteristics of the vegetation, climate, and typical animal life found there.

 

Question 2. Find the etymology of Herbivores, carnivores, omnivores and scavengers using dictionary
Answer: Etymology is the study of where words come from and how their meanings have changed over time. For these words:
1. Herbivores: The word "Herba" means plant, and "Vorare" means to swallow. So, herbivores are animals that eat plants.
2. Carnivores: "Carni" means flesh, and "Vorare" means to swallow. Carnivores are animals that eat meat.
3. Omnivores: "Omni" means all, and "Vorare" means to swallow. Omnivores are animals that eat both plants and meat.
4. Scavengers: "Scavage" means to search or inspect through rubbish. Scavengers are animals that feed on dead plants, animals, or refuse. Studying word origins helps us better understand their precise scientific definitions.
In simple words: Etymology tells us where words come from. Herbivores eat plants (Herba = plant), carnivores eat meat (Carni = flesh), omnivores eat both (Omni = all), and scavengers eat dead things (Scavage = search rubbish).

🎯 Exam Tip: For etymology questions, break down the word into its root parts and explain the meaning of each part to show a clear understanding.

 

Samacheer Kalvi 9th Social Science Biosphere Additional Important Questions and Answers

I. Fill in the Blanks

 

Question 1. All living things large or small are grouped into ______
Answer: Species. All living organisms, from the smallest bacteria to the largest whales, are categorized into distinct groups called species, allowing scientists to study their characteristics and relationships more easily.
In simple words: All living things, big or small, are sorted into groups called species.

🎯 Exam Tip: Remember that 'species' is a basic unit of biological classification, crucial for understanding biodiversity.

 

Question 2. The area in which an animal, plant or micro organisms lives is called its ______
Answer: Habitat. A habitat is the natural home or environment where an animal, plant, or microorganism usually lives. It provides everything an organism needs to survive, such as food, water, and shelter.
In simple words: The place where an animal, plant, or tiny organism lives is called its habitat.

🎯 Exam Tip: Clearly define habitat as the natural home, emphasizing that it provides necessary resources for survival.

 

Question 3. The chain of transformation of energy from one group of organisms to another through various trophic levels is called a ______
Answer: Food chain. A food chain shows how energy moves from one living thing to another when they eat each other. It describes who eats whom in an ecosystem.
In simple words: Energy moving from one living thing to another when they eat each other is called a food chain.

🎯 Exam Tip: Focus on 'energy transfer' and 'trophic levels' as key terms when defining a food chain.

 

Question 4. The Extinction of species is called ______
Answer: Loss of Biodiversity. When a type of animal or plant completely dies out and is no longer found anywhere on Earth, it is called the loss of biodiversity. This is a permanent and irreversible event, leading to a reduction in the variety of life on our planet.
In simple words: When all of one kind of plant or animal die out, it's called loss of biodiversity.

🎯 Exam Tip: Understand that extinction is a natural process but accelerated loss of biodiversity due to human activity is a major concern.

 

Question 5. In Temperate Grass Lands Biome higher precipitation leads to ______ grass.
Answer: Tall and soft. In temperate grasslands, more rain means taller and softer grass can grow. This allows different types of vegetation to flourish.
In simple words: More rain in temperate grasslands makes the grass grow tall and soft.

🎯 Exam Tip: Remember the relationship: higher precipitation supports denser and taller vegetation in grasslands.

 

Question 6. In Temperate Grassland Biomes lower precipitation leads to ______ grass.
Answer: Short and soft. If there is less rain in temperate grasslands, the grass that grows there will be shorter and softer. This adaptation helps plants survive in drier conditions.
In simple words: Less rain in temperate grasslands means the grass will be short and soft.

🎯 Exam Tip: Conversely, lower precipitation limits vegetation growth, resulting in shorter and sparser grass.

 

Question 7. Tundra Biomes are also called ______
Answer: Barren Lands. Tundra biomes are often called barren lands because they are very cold and dry, making it hard for many plants to grow. This harsh environment is characterized by permafrost and low-growing vegetation.
In simple words: Tundra areas are also known as barren lands because they are cold and don't have many plants.

🎯 Exam Tip: Associate 'Tundra' with 'Barren Lands' due to its cold, dry, and low-vegetation characteristics.

 

Question 8. Lakes, ponds, rivers, streams, wetlands together known as ______ biomes.
Answer: Freshwater. All these bodies of water – lakes, ponds, rivers, streams, and wetlands – are grouped together as freshwater biomes. They are crucial habitats for many species and provide vital resources.
In simple words: Lakes, ponds, rivers, streams, and wetlands are all parts of freshwater biomes.

🎯 Exam Tip: Classify water bodies into freshwater or marine biomes based on salinity.

 

Question 9. In aquatic ecosystem, there is abundant water with limited ______ supply.
Answer: Oxygen. In many aquatic ecosystems, while there is plenty of water, the amount of dissolved oxygen can be limited, especially in deeper or polluted areas. Oxygen availability is a critical factor for aquatic life.
In simple words: In water environments, there is a lot of water but often not enough oxygen.

🎯 Exam Tip: Remember that dissolved oxygen is a key limiting factor for life in aquatic environments, not just the water itself.

 

Question 10. Terrestrial animals use only 1 – 2% of energy to obtain ______
Answer: Oxygen. Terrestrial animals only use a small percentage (1-2%) of their total energy intake to get oxygen from the air. This shows how efficient their respiratory systems are compared to other metabolic processes.
In simple words: Animals on land use only a tiny bit of their energy (1-2%) to get oxygen.

🎯 Exam Tip: Understand that energy expenditure for respiration is relatively low for terrestrial animals due to the high oxygen concentration in the atmosphere.

 

Question 11. The wide variety of living organisms that are found on the planet is called ______
Answer: Biodiversity. The term biodiversity refers to the huge variety of all living things, including plants, animals, and microorganisms, found on Earth. This diversity is essential for the health of our planet.
In simple words: The many different kinds of living things on Earth are called biodiversity.

🎯 Exam Tip: Define biodiversity as the variety of life at all levels, from genes to ecosystems.

 

Question 12. The study about freshwater ecosystem is called ______
Answer: Limnology. Limnology is the scientific study of inland waters, including lakes, rivers, ponds, and wetlands. It covers their physical, chemical, and biological features.
In simple words: The study of freshwater places like lakes and rivers is called limnology.

🎯 Exam Tip: Distinguish limnology (inland waters) from oceanography (marine waters).

 

Question 13. The study of the sources, development and history of a word is called ______
Answer: Etymology. Etymology is the study of how words have changed over time, including their origins and historical development. It helps us understand the roots and evolution of language.
In simple words: Learning where words come from and how they changed is called etymology.

🎯 Exam Tip: Connect etymology to the historical evolution of language and the meanings of words.

 

Question 14. There are ______ Biosphere Reserves in India.
Answer: 18. India currently has 18 designated biosphere reserves, which are special protected areas for the conservation of biodiversity. These reserves help protect various ecosystems and species.
In simple words: India has 18 special places called Biosphere Reserves to protect nature.

🎯 Exam Tip: Be aware of the current number of biosphere reserves in your country for factual accuracy.

II. Choose the correct answer

 

Question 1. The life-supporting layer is known as
(a) Atmosphere
(b) Hydrosphere
(c) Lithosphere
(d) Biosphere
Answer: (d) Biosphere
In simple words: The biosphere is the part of Earth where all life exists, including the air, water, and land.

🎯 Exam Tip: Remember that the biosphere encompasses all regions of Earth where life can be found, interacting with the atmosphere, hydrosphere, and lithosphere.

 

Question 2. The branch of science that deals with an ecosystem are called
(a) Etymology
(b) Geology
(c) Limnology
(d) Ecology
Answer: (d) Ecology
In simple words: Ecology is the science that studies how living things interact with each other and their environment.

🎯 Exam Tip: Clearly define ecology as the study of ecosystems, focusing on interactions between organisms and their environment.

 

Question 3. Abiotic components include
(a) Non-living things
(b) Living things
(c) only plants
(d) only animals
Answer: (a) Non-living things
In simple words: Abiotic parts of an ecosystem are things that are not alive, like rocks, water, and air.

🎯 Exam Tip: Differentiate clearly between 'abiotic' (non-living) and 'biotic' (living) components of an ecosystem.

 

Question 4. Zebra and goat come under ______ consumers.
(a) Primary
(b) Secondary
(c) Tertiary
(d) None of the options
Answer: (a) Primary
In simple words: Zebras and goats eat plants, so they are primary consumers, the first level of animals in a food chain.

🎯 Exam Tip: Primary consumers are herbivores that feed directly on producers (plants).

 

Question 5. A healthy ecosystem provides
(a) clean water
(b) enriched soil
(c) raw materials
(d) All of the options
Answer: (d) All of the options
In simple words: A good ecosystem gives us clean water, rich soil for plants, and useful raw materials from nature.

🎯 Exam Tip: Understand that healthy ecosystems provide a wide range of 'ecosystem services' that benefit humans and the environment.

 

Question 6. Assertion (A): A stable biosphere has to be conserved. Reason (R): The loss of biodiversity affects land, water, air etc.
Answer: (a) Both assertion (A) and reason (R) are true; R explains A
In simple words: It is true that a healthy biosphere must be protected, and the reason is that losing different kinds of life harms the land, water, and air.

🎯 Exam Tip: For assertion-reason questions, first check if both statements are individually true, then determine if the reason correctly explains the assertion.

 

Question 7. Assertion (A): In temperate grassland biomes pastoral industry becomes the main occupation. Reason (R): Apart from wheat cultivation, tall and short soft grass are grown in the temperate grassland biomes.
Answer: (a) Both assertion (A) and reason (R) are true; R explains A
In simple words: It is true that farming animals is a main job in temperate grasslands, and this is because various kinds of soft grasses grow there, besides wheat.

🎯 Exam Tip: Link the natural vegetation (grass) of a biome to its predominant economic activity (pastoral farming) for a strong explanation.

 

Question 8. Assertion (A): Biosphere Reserves are established in India. Reason (R): Today's loss of biodiversity is habitat alteration caused by human activities.
Answer: (a) Both assertion (A) and reason(R) are true; R explains A
In simple words: Both statements are correct: India has biosphere reserves, and the main reason for losing different types of life today is human activity changing natural habitats.

🎯 Exam Tip: Recognize that biosphere reserves are a conservation strategy, and human-induced habitat alteration is a primary driver of biodiversity loss.

III. Match the following

 

Question. Match the following
1. World wild life day
2. International day of forest
3. World water day
4. Earth day
5. World oceans day
(a) 8th June
(b) 22nd April
(c) 3rd March
(d) 22nd March
(e) 21st March
Answer:
1. (c) 3rd March
2. (e) 21st March
3. (d) 22nd March
4. (b) 22nd April
5. (a) 8th June
In simple words: We match each important day to its correct date. This helps us remember key environmental and wildlife observance dates.

🎯 Exam Tip: Carefully cross-reference each item in column A with its corresponding match in column B, paying attention to specific dates and events.

IV. Give short answers

 

Question 1. What is considered a hotspot?
Answer: An ecological region is called a hotspot if it has lost more than 70% of its original natural habitat. These areas are crucial for biodiversity but are under severe threat. Hotspots are identified for urgent conservation efforts due to their high biodiversity and vulnerability.
In simple words: A hotspot is a natural area that has lost over 70% of its original natural land.

🎯 Exam Tip: The key criteria for an ecological hotspot are high biodiversity and significant habitat loss (over 70%).

 

Question 2. In India where do we find hot spots?
Answer: In India, we find biodiversity hotspots in the Himalayas, the Western Ghats, the Indo-Burma Region, and Sundaland. These regions are rich in unique species but face significant threats. Each hotspot boasts a unique set of flora and fauna, making their conservation particularly vital.
In simple words: Hotspots in India are in the Himalayas, Western Ghats, Indo-Burma Region, and Sundaland.

🎯 Exam Tip: Remember the four major biodiversity hotspots located within or bordering India for a complete answer.

 

Question 3. Mention the human settlement in the Tropical Forest Biomes.
Answer: Tropical Forest Biomes have very dense forests, so human settlements there are usually scattered. People living in these areas get their food, fish, cut timber, and practice shifting cultivation to support themselves. Their way of life is closely linked to the forest resources.
In simple words: People live scattered in tropical forests because they are very thick. They get food, fish, cut wood, and farm by moving from place to place.

🎯 Exam Tip: Highlight the dispersed nature of settlements in dense forests and list the primary subsistence activities like hunting, fishing, and shifting cultivation.

 

Question 4. What threat is posed by the savanna grasslands?
Answer: Lately, parts of the savanna grasslands are being turned into farmlands. This change creates a big danger for many kinds of animals that live there. For example, the number of large cats like cheetahs and lions is quickly going down because they are losing their natural hunting grounds. This conversion to agriculture severely disrupts the delicate balance of the savanna ecosystem.
In simple words: Savanna grasslands are being turned into farms. This harms many animals, like big cats whose numbers are falling fast.

🎯 Exam Tip: Focus on 'habitat loss due to conversion to farmlands' and its direct impact on wildlife, particularly apex predators.

 

Question 5. What has been identified by the U.S. National Cancer Institute?
Answer: The U.S. National Cancer Institute has found that about 70% of the plants used to treat cancer come from rain forests. These valuable plants are primarily found only in rain forests. This discovery highlights the immense medicinal value of rainforest biodiversity and the importance of preserving these ecosystems.
In simple words: The U.S. National Cancer Institute found that 70% of cancer-fighting plants grow only in rain forests.

🎯 Exam Tip: The key point is the high percentage of medicinal plants, especially for cancer treatment, originating from rainforests.

 

Question 6. Name the common animals found in the Tropical Savanna Biomes.
Answer: In the Tropical Savanna biomes, common animals include lions, leopards, tigers, deer, zebras, and giraffes. Additionally, plants like Rhodes grass, red oats grass, and lemon grass are typical flora in this biome. These animals and plants are well-adapted to the seasonal dry and wet conditions of the savanna.
In simple words: Lions, leopards, tigers, deer, zebras, and giraffes are common animals in Tropical Savannas.

🎯 Exam Tip: When listing animals and plants, ensure they are characteristic species of the specific biome mentioned.

 

Question 7. Write about Oasis.
Answer: An oasis is a fertile area in a desert or semi-arid region where there is a fresh water source. These oases are fed by underground springs. Around these water sources, crops like date palms, figs, citrus fruits, and maize are grown. Oases are vital for life in harsh desert environments, providing refuge and resources.
In simple words: An oasis is a green, fertile spot in the desert with fresh water from springs. Date palms and other crops grow there.

🎯 Exam Tip: Define an oasis by its key features: a fertile area, fresh water source (springs), and its location in deserts.

 

Question 8. Mention the different names of the Temperate grass lands.
Answer: Temperate grasslands are known by different names in various parts of the world. For example, they are called Prairies in North America, Steppes in Eurasia, Pampas in Argentina and Uruguay, and Downs in Australia and New Zealand. These regional names reflect the diverse geographic distribution of these biomes. Each name tells us about the local characteristics and history of these areas.
In simple words: Temperate grasslands have different names around the world, like Prairies (North America), Steppes (Eurasia), Pampas (Argentina/Uruguay), and Downs (Australia/New Zealand).

🎯 Exam Tip: Be sure to list at least 3-4 distinct regional names for temperate grasslands along with their locations.

 

Question 9. What is a Biosphere Reserve?
Answer: A Biosphere Reserve is a special protected area or environment designed to conserve flora and fauna that need protection and care. It's like a living laboratory for sustainable development and biodiversity conservation. India has 18 such Biosphere Reserves, aiming to protect unique ecosystems and promote research and education.
In simple words: A Biosphere Reserve is a special area where plants and animals are protected and cared for. India has 18 such reserves.

🎯 Exam Tip: Emphasize that biosphere reserves are designated areas for both conservation and sustainable human development.

 

Question 10. Explain the following terms
(a) Herbivorous
(b) Carnivorous
(c) Omnivorous
(d) Scavengers
Answer:
(a) Herbivorous: A herbivore is an animal that gets its energy by eating only plants. Many herbivores have special digestive systems that help them break down plant matter, like deer, rabbits, cows, sheep, goats, elephants, giraffes, horses, and pandas. Their diet focuses exclusively on plant-based foods.
(b) Carnivorous: A carnivore is an animal that obtains food by hunting and eating other animals. They also scavenge on dead flesh. Examples include hyenas, wolves, mountain lions, and polar bears. Carnivores play an important role in controlling populations of other animals.
(c) Omnivorous: An omnivore is an animal that eats both other animals and plants. Raccoons, pigs, rats, chickens, and crows are examples. This flexible diet allows omnivores to adapt to various food sources in different environments.
(d) Scavengers: Scavengers are animals that primarily feed on the bodies of dead animals or decaying plant material. Jackals, leopards, lions, and vultures are examples. By consuming dead matter, scavengers help clean up ecosystems and recycle nutrients.
In simple words: Herbivores eat only plants. Carnivores hunt and eat other animals. Omnivores eat both plants and animals. Scavengers eat dead animals or plants.

🎯 Exam Tip: Clearly define each term by its primary food source and provide diverse examples for each category.

V. Distinguish between the following.

 

Question 1. Tropical Grasslands and Temperate grassland.
Answer:
Tropical Grasslands:
1. Tropical grasslands are usually found between tropical forests and deserts.
2. These areas are typically hot and dry, experiencing moderate to low rainfall.
3. The grass that grows here is generally tall and sharp. The high temperatures and distinct wet/dry seasons define this biome.
Temperate Grasslands:
1. Temperate grasslands are commonly found in the interior parts of continents.
2. They have large seasonal temperature changes, with warm summers and cold winters.
3. The type of grass in these regions depends heavily on the amount of precipitation. Higher rainfall leads to tall, soft grass, while less rain results in short, soft grass. These biomes are crucial for agriculture and grazing.
In simple words: Tropical grasslands are hot and dry, found near forests and deserts, with tall, sharp grass. Temperate grasslands are in the middle of continents, have warm summers and cold winters, and their grass height depends on rain.

🎯 Exam Tip: For distinguishing between biomes, compare their geographical location, climate characteristics (temperature, rainfall), and typical vegetation structure.

VI. Give reasons for the following

 

Question 1. In tropical savannas the chief occupation is herding.
Answer: In tropical savannas, the main job is herding because these areas have low rainfall and tall, sharp grass. This type of vegetation is perfect for grazing animals like cattle. Since there isn't enough rain for extensive crop farming, raising livestock becomes the most practical way for people to earn a living. The wide-open spaces and abundant grass support large herds, making herding a sustainable practice.
In simple words: Herding is the main job in tropical savannas because there isn't much rain, but there's lots of tall grass good for animals to eat.

🎯 Exam Tip: Link the climatic conditions (low rainfall) and vegetation (tall grass) directly to the dominant economic activity (herding) in the savanna.

 

Question 2. Tropical Forest Biomes have economic importance.
Answer: Tropical Forest Biomes, like those in the Amazon basin, Congo basin, and Indonesian islands, are economically important because they have very dense forests. These forests provide valuable resources such as rubber, bamboo, and ebony trees. The rich biodiversity also offers potential for new medicines and scientific discoveries. These resources are vital for various industries and local communities.
In simple words: Tropical forests are important for money because they are very dense and give us useful things like rubber, bamboo, and ebony wood.

🎯 Exam Tip: When discussing economic importance, list specific valuable resources or products derived from the biome.

 

Question 3. Why do people in Tundra region shift their settlement frequently?
Answer: People in the Tundra region often move their settlements because the environment is very harsh. They are nomadic, meaning they move from place to place. Their survival depends on hunting and fishing, which requires them to follow animal migrations and seasonal fishing spots. The population in these areas is very sparse, and resources are limited, making frequent movement necessary to find food and shelter. This nomadic lifestyle is an adaptation to the extreme climate and scarce resources.
In simple words: People in the Tundra move often because the weather is harsh and they need to follow animals for hunting and fishing to find food.

🎯 Exam Tip: Connect the harsh environmental conditions and the availability of migratory resources (hunting, fishing) directly to the nomadic lifestyle of Tundra inhabitants.

VII. Answer in detail

 

Question 1. Write a note on Biodiversity.
Answer:
(a) Biodiversity:
1. Biodiversity, or biological diversity, means the wide variety of living organisms, including plants, animals, and microorganisms, that live in a particular habitat.
2. It is greatly affected by the land's features, climate, and human activities.
3. Biodiversity shows how strong and rich the biological resources are in a specific place on Earth. It is a measure of the health and resilience of an ecosystem.
4. In biodiversity, every species, no matter how big or small, plays an important role in the ecosystem.
5. It helps maintain the ecological balance and provides social benefits like tourism, education, and research across an area.
(b) Loss of biodiversity:
1. The extinction of species (plants and animals) due to human actions and natural events is called the loss of biodiversity.
2. This loss has a big impact on people and also harms land, water, and air.
3. Major causes for biodiversity loss include habitat destruction from deforestation, rapid population growth, pollution, and global warming. These human activities are leading to a rapid decline in species.
4. Sometimes, habitat loss is so severe or happens so quickly that it causes a species to disappear completely from the planet.
5. Scientists are still trying to understand what caused the mass extinction of dinosaurs, which was a massive loss of biodiversity in the past.
In simple words: Biodiversity is all the different kinds of life (plants, animals, tiny living things) in a place. It's important for nature's balance. Losing biodiversity means species die out, often because of humans destroying habitats, pollution, or climate change.

🎯 Exam Tip: When explaining biodiversity, cover both its definition and importance, and then detail the causes and impacts of its loss, using clear examples.

 

Question 2. Explain the need for conservation.
Answer:
1. The biosphere stretches from the deepest ocean trenches to the richest rainforests, showing the vast interconnectedness of life. This means life exists across many different environments.
2. People have a crucial role in making sure energy flows properly through the biosphere, as every action has an impact.
3. However, the main reason for today's loss of biodiversity is human activities changing natural habitats.
4. The increasing human population leads to over-using natural biological resources, putting a strain on ecosystems.
5. This overuse has a bad effect on all plants and animals on Earth. It upsets the natural balance and can lead to species extinction.
6. There are biologically rich areas on Earth that are also seriously threatened, needing urgent protection.
7. Therefore, it is everyone's job to protect and care for Earth to make it a better place for all living things to live. Conservation is about managing resources wisely for future generations.
In simple words: We need conservation because life is everywhere, but humans are harming it by destroying homes and using too many resources. It's our job to protect the Earth and its many living things so we all have a good place to live.

🎯 Exam Tip: Focus your explanation of conservation on the threats to biodiversity (human impact, overexploitation) and the ethical responsibility to protect ecosystems and species.

Free study material for Social Science

TN Board Solutions Class 9 Social Science Chapter 05 Biosphere

Students can now access the TN Board Solutions for Chapter 05 Biosphere prepared by teachers on our website. These solutions cover all questions in exercise in your Class 9 Social Science textbook. Each answer is updated based on the current academic session as per the latest TN Board syllabus.

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