Chapter 2 — The Living World

How do we decide what is living?
We call something living when it shows the features of life. These are actions or processes that living things do by themselves, such as taking food, growing, showing movements, reacting to the environment and producing new individuals. In everyday life you meet many things and asking the question 'Is it living?' helps you sort them. A plant, a dog and a tiny insect are living. A stone, a chair or a toy are not living. But some things can look like they move or change; for example, fire moves and spreads, and crystals grow; yet these are not living because they do not carry out all life processes from within a cell-based system.

Simple tests to check living status
You can think of short observations: does it grow over time? does it need food or water to survive? does it respond when touched or when light changes? does it make more individuals of its kind? If answer is yes to many of these, it is likely living. For example, a seed kept in soil with water will sprout and show growth, while a stone kept in the same soil will remain unchanged.

Special cases and careful thinking
Sometimes things like a cut tree trunk may show no growth yet may still be part of a living organism until it is completely dead. A toy dog moves when you push it but cannot take food or reproduce. Microorganisms are living but tiny and invisible to the eye; you need a magnifier or microscope. Learning the idea of 'living' helps you understand what needs care and protection in nature, and how different life forms are related by the processes they carry out.

Common characteristics
Living organisms share several important features that help us recognise them. These features are: nutrition, respiration, movement, sensitivity (response), growth, reproduction and excretion. Each of these plays a role in keeping the organism alive and healthy. Nutrition provides building material and energy. Respiration releases energy from food. Movement helps an organism change position or move its parts. Sensitivity allows organisms to react to changes such as light or touch. Growth is the increase in size or number of cells. Reproduction produces new individuals and excretion removes waste materials from the body.

Why these features matter
These features are not isolated; they work together. For example, nutrition supplies the material needed for growth and reproduction. Respiration provides the energy required for movement and active processes. Excretion prevents harmful waste build-up that would stop normal functioning. Observing these characteristics in class or at home helps students understand that life is organised and maintained by continuous activities.

How to observe characteristics
Students can perform simple observations: watch a plant for growth, measure how a sprouted seedling increases in height; observe a pet eating and breathing to notice nutrition and respiration; touch a sensitive plant like Mimosa pudica to see rapid response. Discuss examples where a single feature is present alone (like fire showing movement but not reproduction) to reinforce why all features together define living.

Class activity ideas
Make a chart with the seven characteristics. For each classroom organism or picture, tick the features it shows. Use everyday examples — a sprouting bean, a goldfish, a piece of bread with mould — to discuss which features are present and why mould is living while bread without mould is not.

Why study levels?
Living bodies are not a random collection of parts. They are organised in levels so that small units form larger systems which together perform complex tasks. This organisation helps maintenance, repair and specialised working. By studying levels we can understand how small parts help the whole organism live and function.

The levels explained
The smallest unit of life is the cell. Cells with the same shape and job join to form a tissue. Different tissues combine to make an organ, which performs a specific function. Several organs working together form an organ system. Many organ systems together make a complete organism. Each level increases complexity and specialisation: cells do simple tasks, while organs and systems do more complex jobs that single cells cannot do alone.

Examples from plants and animals
In plants, many photosynthetic cells form leaf tissue; the leaf (an organ) makes food. The stem and root are other organs; together they form the plant body. In animals, muscle cells form muscle tissue; heart tissue forms the heart organ that pumps blood; the heart, blood vessels and blood form the circulatory system. The nervous system, digestive system and others work with the circulatory system to keep the animal alive.

Importance for study and health
Understanding organisation helps in simple medical and botanical thinking. If cells are damaged, tissues can repair or replace them. If an organ fails, other organs or treatments can help. Class activities like observing onion peel cells under a microscope, feeling different tissues (paper-like, cotton-like) and drawing the level diagram make the concept clear and memorable.

What is a cell?
A cell is the smallest unit that can do the work of life. It can take in food, use energy, grow and reproduce. Some living things are made of only one cell; others, like plants and animals, are made of many. Learning about cells helps us see how life operates at the smallest level.

Structure in simple words
Cells have an outer covering that protects them and controls what enters and leaves. Inside, they have cytoplasm where many activities happen. Plant cells usually have a rigid cell wall outside the cell membrane which gives shape and support. Plant cells also contain chloroplasts, the green parts where photosynthesis occurs. Animal cells do not have a cell wall or chloroplasts and often have a rounder shape. At this class level we do not go into many parts but knowing the wall, membrane and chloroplasts helps explain plant behaviour.

Seeing cells
Using a simple microscope or magnifier, students can look at thin layers called peels from an onion, or the inner skin of a banana. Under the microscope, plant cells may look like a brick wall made of repeated units. Pond water samples may show tiny single-celled organisms moving about. It is good practice to draw what you observe and label the visible parts. Stains such as iodine help show parts more clearly but should be used under teacher supervision.

Why cells matter
Cells are the building blocks of life. Health problems happen when cells are damaged; growth occurs when cells divide and multiply. When we heal a cut, cells multiply to repair the wound. Knowing about cells also lays the groundwork for later learning about tissues, organs and systems. Simple classroom experiments and drawing exercises make the idea of the cell clear and interesting for young learners.

Major parts of a typical flowering plant
Most common plants have roots, stems, leaves, flowers, fruits and seeds. Each part has a clear job that helps the plant survive and reproduce. Roots keep the plant anchored in the soil, absorb water and minerals, and sometimes store food. The stem holds the plant upright, transports water and food between roots and leaves, and stores some food. Leaves are the main site of photosynthesis where plants make food using sunlight. Flowers are reproductive structures that help make seeds; fruits protect seeds and help spread them. Seeds contain the embryo of a new plant and stored food to support early growth.

Variation and special features
Not all plants show these parts in the same way. Roots can be of two main types: taproot (a main central root with smaller branches) or fibrous roots (many similar roots). Some stems are green and soft, others are woody and hard. Leaves can be simple or compound, large or tiny, and have features like waxy coatings or hair to reduce water loss. Flowers have parts such as petals, sepals, stamens (male parts) and pistils (female parts) which help in pollination. Fruits come in many shapes and help spread seeds by wind, water or animals.

How parts help plant life
Each part works with others: roots absorb water that the stem carries to leaves for photosynthesis. Food made in leaves moves to stems, roots and growing parts through specialised tissues. If any part is damaged, plant growth and reproduction can be affected. Simple classroom activities like dissecting a small plant, observing root hairs under magnification and comparing leaves of different plants make it easy to understand the roles of parts.

External parts and their uses
Animals show a variety of body parts suited to their way of life. Most have head, trunk and limbs or appendages that help them move, eat and sense the world. Body coverings such as fur, feathers, scales or skin protect the body and help with temperature control, camouflage or movement. Mouthparts vary widely: sharp teeth or beaks help predators catch and eat prey, flat grinding teeth help herbivores chew plants, and specialised tongues or proboscises help some insects feed on nectar.

Internal organs and systems
Inside animals are organs made of tissues. The heart pumps blood, lungs or gills take in oxygen, the stomach and intestines break down food for nutrition, and the brain controls sensing and movement. These organs work in organ systems: the digestive system handles food, the respiratory system handles breathing and gas exchange, the circulatory system moves materials around the body, and the nervous system coordinates actions and responses. Insects have a simple blood system and a network of nerves and sense organs suited to their small size.

Adaptation to habitat
Animal body parts are adapted to habitat and lifestyle. Water animals have streamlined bodies and fins or flippers to swim. Tree-climbing animals have claws or adhesive pads. Birds have hollow bones and wings for flight. No single body plan fits all animals; evolution has shaped different structures for feeding, moving, protecting and reproducing. Studying a few local animals and comparing features makes these ideas clear.

Class activity
Examine pictures or simple models of different animals and list the external and internal parts you can identify. Match each part with its function: teeth → type of food; limbs → mode of movement. This helps students see why animals differ and yet share similar organ systems to perform life processes.

What is nutrition?
Nutrition is the process by which living things obtain and use materials needed for growth, repair and energy. While plants and animals both need materials, they get and use them in different ways. Understanding nutrition helps us learn why plants need sunlight and why animals eat specific foods.

Plant nutrition — making food
Green plants make their own food in their leaves through photosynthesis. In this process, chlorophyll captures sunlight and uses its energy to convert carbon dioxide from air and water from soil into sugar (a form of food) and oxygen. The sugar is used for energy and to build plant parts. Roots absorb water and minerals which are vital for photosynthesis and growth. Some plants also store extra food in roots, tubers or stems which can be used later.

Animal nutrition — taking prepared food
Animals cannot make their own food. They must eat plants or other animals. Based on their feeding habits, animals are classified as herbivores (eat plants), carnivores (eat other animals) or omnivores (eat both). Food enters the body through the mouth, is broken down in the digestive system into smaller molecules like sugars, amino acids and fats, and then absorbed into the blood to be carried to cells. Excess food can be stored as fat for later use.

Connections and classroom experiments
Plants produce oxygen and food that animals need; animals give carbon dioxide and waste that plants can use. Simple experiments show nutrition: keep two similar plants, one in light and one in dark— the plant in light stays green and healthy, the dark plant becomes weak because it cannot photosynthesise. Observe different animals and record what they eat, linking mouthparts and digestive structures to diet. These observations show how nutrition supports life and how plant and animal nutrition are connected.

Respiration — getting energy
Respiration is the process by which cells get energy from food. In most living things this happens using oxygen: food is broken down to release energy, and carbon dioxide and water are produced as waste. Plants respire day and night, although during daylight the oxygen they release by photosynthesis may exceed what they use. Animals breathe air or use gills to get oxygen from water.

Transport — moving materials inside
Transport systems move water, food and gases to all parts of the organism. In plants, xylem vessels carry water and dissolved minerals from roots to leaves, while phloem vessels carry the food made in leaves to other parts. In animals, blood transports oxygen, nutrients and wastes. The heart pumps blood through blood vessels, ensuring that every cell receives what it needs.

Excretion — removing wastes
Excretion keeps the body clean by removing harmful or excess waste products. In animals, excretion is done through kidneys (which make urine), lungs (which expel carbon dioxide), skin (which removes sweat) and liver (which processes many wastes). Plants remove some waste through leaves or store harmful substances in bark or older leaves. Efficient excretion is essential because buildup of wastes can harm cells.

Simple classroom demonstrations
Use a balloon-lung model to show breathing: when the diaphragm (a balloon) is pulled, air enters the lung balloon; when it is released, air leaves. Show water transport in a celery or stem using coloured water: the color rises up the stem, demonstrating xylem action. Discuss how balance between respiration and excretion helps keep organisms healthy and how transport links nutrition and respiration to all parts of the body.

Movement in living things
Movement is a feature of many living organisms. Animals show obvious movement — they walk, run, swim or fly to find food, mates and shelter. Plants move too, though usually slower. Movement in plants includes growth towards or away from stimuli: stems often grow towards light and roots grow downwards into the soil. Movement can be whole-body movement or movement of parts, such as leaves opening and closing or flowers turning toward the sun.

Response or sensitivity
Sensitivity is the ability to detect and react to changes in the environment. Plants and animals sense stimuli like light, temperature, touch, smell and gravity. A sensitive plant (Mimosa pudica) folds its leaves when touched. A dog hears a sound and looks toward it. These responses improve chances of survival by helping organisms find food, avoid danger or reproduce.

Types of plant movements
Plant movements include tropisms and nastic movements. Tropisms are directional growth responses: phototropism is growth toward light, geotropism is growth influenced by gravity (roots growing downward). Nastic movements are non-directional responses to stimuli, like a flower opening at day and closing at night. These actions are slower than animal movements but important for life functions such as maximizing light capture or protecting reproductive parts.

Activities and observations
Students can observe phototropism by placing a potted plant near a window and noting how it bends toward the light. Simple games can explore animal responses: clap and watch how students react, or play a sound and see which direction animals turn. Discuss how movement and response together help organisms adapt to changing conditions and survive in their habitats.

What is growth?
Growth is the increase in size, mass or cell number of an organism. In plants, growth occurs at special regions called meristems at root and shoot tips where cells divide actively. In animals, growth occurs by cell division and by increase in cell size until adult form is reached. Growth can be measured by comparing height, weight or size over time. Proper nutrition and favourable conditions help healthy growth.

Types of reproduction
Reproduction is the process of producing new individuals. It ensures continuation of a species. There are two broad types: asexual and sexual reproduction. In asexual reproduction, a single parent produces offspring that are similar to itself. Examples include budding in hydra and vegetative propagation in plants such as taking cuttings or tubers. Sexual reproduction involves two parents (male and female) and fusion of gametes; offspring often show a mixture of traits from both parents.

Why reproduction and growth are linked
Growth is necessary for a young organism to reach adult form capable of reproduction. Reproduction produces new offspring which then grow. Different organisms reproduce at different rates: some like bacteria multiply very quickly, while others like elephants reproduce slowly with long care for young. Understanding these differences helps explain population changes in nature and the need for care of young in many species.

Class activities
Observe and record growth of germinating seeds over days to see growth in action. Demonstrate vegetative reproduction using a stem cutting of a houseplant. Draw simple life cycles of plants and animals showing stages from birth to reproduction and back to next generation. These activities make the ideas of growth and reproduction concrete and relatable for students.

Understanding habitat
A habitat is the natural home or environment of an organism where it finds food, water, shelter and mates. Habitats vary widely: ponds, rivers, forests, deserts, grasslands, mountains and human-made gardens all provide different living conditions. The characteristics of a habitat — such as temperature, amount of water, type of soil and available shelter — determine which organisms can live there.

Adaptations help survival
Adaptations are features or behaviours that help an organism live in its habitat. These can be structural, like body shape and coverings; behavioural, like migration or nocturnal activity; or physiological, like the ability to conserve water. For instance, fish have gills to extract oxygen from water, while birds have light hollow bones for flight. Cacti have thick stems to store water and spines instead of leaves to reduce water loss, a structural adaptation to desert life.

Local and seasonal adaptations
Many animals migrate to find food or to breed; some hibernate in winter to conserve energy. Plants may shed leaves during dry or cold seasons to reduce water loss. Even humans adapt by wearing suitable clothes and building shelters. Adaptations evolve over generations and match the lifestyle and food habits of the organism. Observing local plants and animals helps students link feature to function and see adaptation as a response to habitat demands.

Activities to explore adaptation
Ask students to pick three local organisms and list physical or behavioural traits that help each survive. Discuss how a frog’s webbed feet suit swimming, or how bright flower colours attract pollinators. Simple drawing and role-play activities bring understanding: students can act as desert animals conserving water or as migratory birds flying to warmer areas, reinforcing the link between habitat and adaptation.

What is biodiversity?
Biodiversity means the variety of living forms in an area — the many kinds of plants, animals and microbes that share an environment. Even a small garden has many different organisms: grasses, herbs, shrubs, birds, insects and microbes. This variety is important because different organisms do different jobs in nature, such as making food, decomposing waste, pollination and providing food for other creatures.

Why classify living things?
Because there are so many kinds of organisms, scientists group them using classification. For Class 6 we use simple and practical groups: divide life broadly into plants and animals, then into subgroups that are easy to observe — for plants: herbs, shrubs and trees; for animals: fishes, birds, mammals, reptiles, amphibians and insects. Grouping is based on visible features such as body covering (feathers, fur, scales), presence of flowers, or whether they live in water or on land. Classification helps us study, remember and communicate about organisms.

How diversity helps people and nature
Different organisms support human life in many ways. Plants give us food, clothing material and medicines; animals provide milk, eggs, meat and labour; microbes help in making curd and decomposing waste. A balanced variety keeps ecosystems stable: predators control herbivore numbers, plants provide oxygen and habitats, and decomposers recycle nutrients. Losing species can upset this balance and harm human well-being.

Protecting the living world
Understanding diversity leads to caring for the environment. Simple actions — planting native trees, avoiding harm to local water bodies, recycling and reducing pollution — help protect biodiversity. Class activities can include making a list of local species, grouping them by observable features, and creating posters on why each species matters. These exercises build respect for life and show how each organism, big or small, is part of a connected living world.