1. What is life?

The term "living" applies to organisms that show certain specific features that non-living things do not. Living creatures — including plants, animals and microorganisms — carry out functions that keep them alive. Non-living things may show some of these features (for example, a car moves) but do not show them all and cannot perform life processes independently.

2. Key characteristics of living organisms

NCERT lists several features that help us recognise living things. Each characteristic is important and can be observed directly or experimentally in simple classroom activities.

• Movement (locomotion and movement of parts): Most animals move from place to place (locomotion). Plants do not usually move from place to place, but they show movement of parts — for example, roots grow downwards and stems grow upwards; leaves and flowers may respond to light. Movement is often obvious in animals (walking, flying, swimming) and in plants as growth-based movements.
• Respiration: All living things respire — they break down food to release energy. Respiration may be visible as breathing in animals (inhaling and exhaling). In plants, respiration occurs continuously at a cellular level. A simple classroom activity: placing a small plant in a sealed container and measuring carbon dioxide produced with limewater indicates respiration (advanced activity under supervision).
• Sensitivity or response to stimuli: Living organisms respond to changes in their environment. Plants bend towards light (phototropism); a person pulls back a hand from a hot object — these are responses to stimuli. Observing how a touch-sensitive plant (Mimosa pudica) folds its leaves when touched is a classic demonstration.
• Growth: Living things grow — increase in size and often in complexity. Growth in plants and animals may be slow or fast, but it is a continuous process. Seeds germinate into seedlings, which grow into mature plants; baby animals grow into adults. Growth is irreversible and requires nutrients and energy.
• Reproduction: Living organisms reproduce to give rise to new organisms of the same kind. Reproduction may be sexual (involving two parents and the formation of seeds, eggs or embryos) or asexual (single parent gives rise to offspring, e.g., budding in yeast or vegetative propagation in plants). Reproduction ensures survival of the species.
• Excretion: Waste products formed during life processes must be removed. Animals excrete substances like carbon dioxide, urine and sweat; plants excrete oxygen (a byproduct of photosynthesis) and other waste products through leaves or roots. Excretion prevents toxic build-up inside organisms.
• Nutrition: Living organisms obtain food for energy and growth. Plants make their own food by photosynthesis (autotrophic nutrition) using sunlight, water and carbon dioxide. Animals obtain food by eating plants or other animals (heterotrophic nutrition). Fungi absorb nutrients from dead matter (saprophytic nutrition).

Tip: For quick recall in exams, remember the mnemonic MR. SGERN (Movement, Respiration, Sensitivity, Growth, Excretion, Reproduction, Nutrition) or create your own memory aid.

3. Simple classroom activities to observe characteristics

Short, safe activities strengthen understanding. A few suggestions:

• Movement: Observe a potted plant under a window and note how stems/leaves bend toward light over days. For animals, watch ants or earthworms and note locomotion.
• Response to stimuli: Use a small amount of light or touch to see how plants or sensitive leaves respond. Record observations with dates.
• Growth: Germinate seeds in a transparent container and observe root and shoot development over time.
• Nutrition: Compare a green leaf kept in sunlight and one kept in shade; after testing with iodine (teacher-supervised), differences in starch indicate photosynthesis.
• Excretion and respiration: Simple breathing exercises and observing condensation on a cold surface after exhaling show breathing and gas exchange.

4. Classification — An introduction (Vertebrates & Invertebrates)

Classification organises living things into groups with similar features. At this stage, students learn a simple and useful division: vertebrates (animals with backbone) and invertebrates (without backbone).

Vertebrates: Examples include fishes, amphibians, reptiles, birds and mammals. These animals have a backbone (vertebral column). They show varied adaptations — fins in fish for swimming, wings in birds for flying, fur in mammals for warmth.

Invertebrates: Examples include insects, worms, molluscs, and arthropods. They lack a backbone and often have simpler body structures. Insects, for example, typically have three body parts (head, thorax, abdomen) and six legs.

Exam tip: Learn a few clear examples from each group and one or two distinguishing features (e.g., birds have feathers and lay eggs; mammals usually have hair and produce milk).

5. Important differences between living and non-living things

While some non-living things may move or change shape when acted upon (a thrown ball), living things perform life processes themselves. Key differences include:

• Living things grow, reproduce and breathe; non-living things do not.
• Living things respond to surroundings; non-living things only change when external forces act on them.
• Living organisms need food and can excrete waste; non-living things have no metabolic activities.

6. Sample short-answer points for revision

These quick points are model answers for common short questions in CBSE assessments:

• Define a living organism: An organism that shows life processes such as growth, respiration, reproduction and response to stimuli.
• Name five life processes: Movement, respiration, sensitivity, growth, reproduction, nutrition and excretion (students may list any important six).
• Give one difference between vertebrates and invertebrates: Vertebrates have a backbone; invertebrates do not.
• Give an example of a plant movement: Directional growth of shoots towards light (phototropism).