Living Creatures: Exploring their Characteristics | CBSE Class 6 Science Notes

This note covers living and non-living things, movement, growth, nutrition, breathing, excretion, responses to stimuli, reproduction, seed germination, growth directions in plants, and the life cycles of bean plants, mosquitoes and frogs.

How can we distinguish living beings from non-living things?

A living being shows the characteristics of life. Movement includes changes in the position of its parts, while growth means an increase in size. Nutrition concerns the food required for growth and development.

Breathing is air moving into and out of the body. It forms part of respiration, a life process shared by living beings. Excretion means removing waste products from the body.

A stimulus is something or an event that prompts a reaction, called a response. Stimuli is the plural of stimulus. Reproduction produces new living beings of the same kind. Living beings eventually undergo death, the ending of life activities.

A non-living thing does not show the essential characteristics of life. A pencil and a book are non-living, while a pigeon and a plant are living. Comparing these examples helps us look beyond a single visible feature.

Why is movement alone insufficient?

A car moves along a road, but movement does not make it a living being. A car does not grow. A plant, on the other hand, does not move from place to place, yet it grows and shows other characteristics of life.

A shell that is not moving could be home to a living snail and is actually part of its body. Therefore, the lack of visible movement at a particular moment does not by itself settle whether a living being is present.

How should a classification be supported?

Begin with an observation, identify a relevant characteristic, and give a reason for the classification. The reason matters as much as the label. Saying that a car moves describes an observation; calling it living on that basis alone overlooks its other features.

The different characteristics are explained separately below. Together they help us recognise living beings, including plants whose movements may be less obvious than those of animals. They also help us investigate a seed instead of deciding from its appearance alone.

How do living beings move, grow and obtain nutrition?

Movement includes changes in the position of parts of a living being. It is not restricted to travelling from one place to another. Plants show movements even though they do not move from place to place as animals do.

What movements can plants show?

The opening of flowers is an example of movement in plants. Climbers are plants that wind themselves around objects placed close to them. These observations show why a plant should not be classified as non-living simply because it stays rooted in one place.

Insectivorous plants are plants that depend on insects for their nutrition. Drosera is an example. Its saucer-shaped leaves have hair-like projections of unequal length, with sticky ends. When an insect enters the saucer, the hairs move inward and trap it.

In Drosera, the part that moves is the hair-like projection on the leaf. The plant need not travel towards the insect for movement to occur. The example links the movement of a plant part with the trapping of an insect.

How are growth and food connected?

Growth is an increase in the size of a living being. Comparing a child's present appearance with a childhood photograph shows growth. Clothes that fitted earlier may no longer fit because the body has become larger. Plants and other living beings also grow.

Nutrition concerns the food living beings need for growth and development. A growing body requires food. Food is therefore another characteristic to consider alongside movement and growth when studying the differences between living beings and non-living things.

Note: Moving from place to place and showing movement are not identical. Opening flowers, inward movement of Drosera hairs and winding of climbers are examples of movement in plants.

Growth is also visible when a seed develops into a young plant. Following such changes over time provides evidence that cannot be obtained by looking briefly at the seed before it begins to grow.

How do breathing and excretion help us recognise living beings?

Breathing is the movement of air into and out of the body. When we inhale, air moves from outside into the body. When we breathe out, air moves from inside the body to the surroundings.

Respiration is a life process of which breathing is a part. All living beings respire. Breathing and respiration should therefore not be treated as two names for exactly the same thing: breathing belongs within the wider process of respiration.

How can breathing be observed?

Count the breaths taken in one minute after a normal walk, a run and a few dance steps. Record and compare the counts, using the same one-minute interval after each activity. Observations should be written down rather than replaced with guessed numbers for the different activities.

In resting animals such as dogs, cats, cows and buffaloes, movement of the abdomen can help us notice breathing. Plants also respire. Stomata are tiny pores on leaf surfaces that help plants take air in and out.

What is removed during excretion?

Definition: Excretion is the removal of waste products from the body. All living beings excrete, including plants.

Sweat contains water and salts removed by the body as waste products. White patches around the armpits of shirts during summer can result from sweat. Urine is also a product of excretion in animals.

Plants can excrete excess water and minerals as small droplets on their leaves. Grasses and roses are examples. The process is still excretion even though its visible form differs from the sweat or urine associated with animals.

How do living beings respond, reproduce and eventually die?

A stimulus is something or an event that prompts a living being to respond. The plural is stimuli. A response is the reaction to a stimulus. All living beings respond to stimuli, including plants.

What are examples of responses?

Stepping on a thorn or accidentally touching a hot cup of tea provides a stimulus to the body. These examples connect a particular event with a reaction. Identifying both parts helps distinguish the stimulus from the response it produces.

The touch-me-not plant, also called mimosa or chhui-mui, folds its leaves when touched. Here, touch is the stimulus and folding of the leaves is the response. This is evidence that plants respond to changes around them.

Certain plants fold their leaves after sunset. In amla, or Indian gooseberry, leaves facing each other tend to come together. Keep the qualification certain plants: this description does not mean that every plant folds its leaves after sunset.

Why is reproduction necessary?

Reproduction means producing new living beings of one's own kind. Cats and dogs have young ones, while a pencil, chair or electric bulb does not. Reproduction maintains the continuity of life by producing a new generation.

Growth and reproduction are connected with different changes. Growth concerns the increase in size of a living being. Reproduction concerns the production of new ones of its kind. The new generation can then undergo its own growth and development.

What does death mean?

Death is the ending of life activities. A living being is considered dead when it can no longer exhibit the characteristics of life despite the availability of resources, such as food, air and water, needed to remain alive.

For a plant, growth stops and its life activities gradually end. The continued availability of suitable conditions matters in this description. A single observation of stillness should not be confused with evidence that all its life activities have ended.

What conditions are needed for a seed to germinate?

Germination occurs when a seed turns into a sprout. A seedling is the young plant that develops. Watching germination allows us to see growth and other characteristics of life in a seed that initially shows little visible change.

Why do seeds need water and air?

The seed coat is the outer covering of a seed. Water softens it and enables the processes needed for growth. Inside is a tiny embryo, the developing young plant, which can grow into a plant when the conditions are suitable.

Seeds require air for germination. In soil, air is available in the spaces between soil particles. These spaces also allow roots to grow easily. Bean seeds need the right amount of water and air, rather than an unlimited supply of water.

A root is the plant part that generally grows downwards during germination. The shoot is the part that grows upwards. These terms distinguish the two growing parts when observing a germinated seed or setting up a plant-growth experiment.

Is light essential for every seed?

Bean seeds do not require light for germination. In general, most seeds do not require light for germination. After germination, however, sunlight is required for the further growth of the seedling. Germination and later growth must therefore be distinguished.

Some flowering plants, such as Coleus and Petunia, have seeds that require light to germinate. Covering these seeds with soil inhibits sprouting. Calendula and Zinnia have seeds that need darkness and should be covered with sufficient soil.

Note: The statement that most seeds do not need light for germination does not mean that all seeds behave alike. Suitable light and/or dark conditions depend on the seed.

Water, air and suitable light and/or dark conditions are thus considered together when investigating germination. The bean-seed experiment helps separate the effect of water supply from the question of whether light is essential for that seed.

How does the four-pot experiment investigate germination?

Use four identical pots containing garden soil, and sow four bean seeds in each. Label the pots A, B, C and D; these letters identify the four treatments. Keep them under the specified conditions for 15 days.

What should be predicted and recorded?

A prediction states what is expected before an experiment is completed. An observation records what actually happens. Keep these separate, so that an expected result is not mistaken for something that has already been seen.

1. Record whether air, water and sunlight are available to the seeds in each pot.
2. Predict whether the seeds in each of the four pots will germinate.
3. Observe the pots regularly for 7 to 10 days and record whether sprouts appear.
4. Compare the observations with the predictions and give possible reasons for the results.

How are the treatments interpreted?

Pot A lacks the water required for germination. In pot B, excess water prevents the seeds from receiving the air they need from spaces in the soil. More water therefore does not necessarily create better conditions for germination.

Pots C and D provide moist soil and air. Germination is expected in both because bean seeds do not need light for germination. The contrast between them concerns darkness and sunlight, while both receive a moderate amount of water.

Compare pots A and D to consider the need for water, and pots B and D to consider excess watering. Compare pots C and D to investigate light. Record actual observations even if they differ from the prediction, then discuss the possible reasons.

Note: The treatment period is 15 days, while the instruction for checking germination is regular observation for 7 to 10 days. These are separate timings in the activity.

How do roots and shoots grow in different positions?

Plant growth can be investigated by changing the position of a seedling and the direction from which it receives light. In this experiment, labels A, B and C identify three separate beakers containing seedlings arranged under different conditions.

How is the experiment arranged?

1. Germinate bean or gram seeds on moist cloth or tissue paper until each seedling has a small root and shoot.
2. Attach thick blotting paper, absorbent paper that takes up water, to each of three glass plates with thick, soft cotton thread. Fix a seedling to each without damaging it.
3. Place the seedlings upright in beakers A and C. Invert the seedling in B, with its shoot downwards and root upwards.
4. Add water with each seedling above the water level. Let the lower end of the blotting paper soak up water, providing moisture to the seedling.
5. Expose A and B to sunlight. Put C in a cardboard box with a small circular hole, allowing light to reach it from one direction only.

Here, inverted means turned upside down. Record predictions about the directions of growth before observing the results. Pay attention to the root and shoot separately because they do not respond by growing in the same direction.

The drawing shows an upright seedling, an inverted seedling with bending parts, and an upright seedling inside a box. The box has a labelled hole, and the shoot bends towards it.

See Fig. 10.3 in your NCERT textbook

What do the results show?

Turning a seedling upside down does not make its root continue upwards. Its growing parts bend so that the root grows downwards and the shoot upwards. With light from one direction, the shoot grows towards that light.

During seed germination, roots generally grow downwards while shoots grow upwards. The experiment also makes plant movement visible through growth. A plant can remain in one place while its root and shoot change their directions.

What happens during the life cycle of a bean plant?

A life cycle describes the stages through which a living being passes. For a plant, the sequence from a seed to a plant and then to the next generation of seeds forms its life cycle.

How can the changes be followed?

Plant a bean seed, provide suitable growth conditions and observe it regularly for three months. Record the date whenever a change becomes visible. Sketching the changes helps preserve the sequence instead of relying on memory at the end.

Note when the first flower appears. Continue observing after some flower parts dry. Watch the remaining parts develop into a fruit. In the bean plant, the fruit is a pod, a structure that contains seeds.

1. A seed begins the sequence and germinates under suitable conditions.
2. The young plant grows, and leaves appear as its development continues.
3. The plant matures and produces flowers.
4. Fruits develop; the bean pods contain seeds.
5. The seeds can produce a new generation of bean plants, continuing the cycle.

Arrows link the seed, germination, appearance of leaves, flowers and fruits. A pod containing seeds connects the fruiting plant to the next seed. A separate arrow leads from the fruiting plant to a dry plant labelled “Death of plant”.

See Fig. 10.4 in your NCERT textbook

How are reproduction and death connected with the cycle?

Sow the seeds obtained from the bean plant to observe the next generation. This links the original plant's development with the growth of new plants. The cycle continues through the seeds produced during the life of the parent plant.

Continue observing the original plant after fruit formation, including whether it becomes yellow and dry despite watering. A plant is considered dead when it stops growing and its life activities gradually end even though all necessary conditions remain available.

The end of one plant's life and the continuation of its kind are therefore different parts of the sequence. Reproduction allows new plants to develop, while the original plant eventually reaches the end of its own life.

How does a mosquito develop through its life cycle?

A mosquito passes through four stages: egg, larva, pupa and adult. A larva is the stage that develops from the egg; pupa names the following stage, from which the adult emerges. Their plurals are larvae and pupae.

What happens at each stage?

1. The adult female lays eggs directly on or near water.
2. An egg develops into a larva living in water.
3. The larva grows into a pupa, another stage that lives in water.
4. The adult emerges from the pupa, rests briefly on the water surface and then flies away.

The adult mosquito may survive for 10 to 15 days. The word “may” matters: the period should not be rewritten as an exact lifetime for every adult. The adult female produces eggs, allowing the life cycle to continue.

The drawing labels four successive stages: egg, larva, pupa and adult mosquito. Arrows connect these stages across the water and the area above it.

See Fig. 10.6 in your NCERT textbook

Why are water and air relevant?

Stagnant water is water that remains standing. It can collect in desert coolers, planted pots and open containers. Two different worm-like forms may be noticed in it: mosquito larvae and pupae. Their body shapes differ.

Larvae and pupae live in water but require air to respire. They repeatedly come to the surface to obtain air. Living in water therefore does not remove their need for air during these stages of development.

How can the order of stages be investigated?

The sequence can be studied by separating larvae and pupae into containers with the same water and observing them daily. If larvae change into pupae, that observation places the larval stage first. Comparing which container produces an adult first gives further evidence.

Observing a change directly is more useful than guessing the order from size or appearance. Significant changes in shape and structure occur between egg, larva, pupa and adult, so neighbouring stages need not closely resemble one another.

How does a frog's life cycle compare with other life cycles?

Spawn is a cluster of frog eggs in a jelly-like substance. It may be seen near the edge of a pond or attached to plants in or around water. The developing organism inside the egg is the embryo.

A tadpole is the young stage with a tail, initially without legs. A froglet is a little frog developing from a tadpole. The four main stages are egg, tadpole, froglet and adult, with changes occurring within the first two stages.

What changes occur in shape and habitat?

A habitat is the place where a living being lives. Tadpoles live in water, and their tails help them swim. Later they develop hind legs, meaning the rear legs, while still retaining their tails. They gradually grow to resemble little frogs.

Froglets still live in water but begin spending some time on land. As they grow, they lose their tails completely. Their legs become strong enough to help them jump and land. Fully developed adult frogs live both in water and on land.

The drawing connects spawn, embryo, tadpole with tail, tadpole with legs, froglet and adult frog. Labels give Day 1, Day 3-4, Day 7-10, 8-10 weeks, 12 weeks and 14 weeks respectively.

See Fig. 10.8 in your NCERT textbook

What is shared, and what differs?

All these living beings pass through stages of growth and development. Reproduction maintains the continuity of their kind, while individual lives eventually end. The particular stages, body changes and places where the stages live differ.

In mosquitoes and frogs, changes in appearance are especially noticeable. Following the sequence helps connect very different-looking stages to the same animal. Caring for living beings and their homes helps preserve the living world in which these cycles continue.

Glossary

• Growth — Increase in the size of a living being as it develops.
• Nutrition — The food requirement of living beings for their growth and development.
• Breathing — Movement of air into and out of the body, forming part of respiration.
• Stomata — Tiny pores on leaf surfaces that help plants take air in and out.
• Excretion — Removal of waste products from the body of a living being.
• Stimulus — Something or an event that prompts a living being to respond.
• Reproduction — Production of new living beings of one's own kind, maintaining continuity of life.
• Germination — The change in which a seed turns into a sprout.
• Seed coat — The outer covering of a seed, softened by water during germination.
• Life cycle — The sequence of stages through which a living being passes during its life.
• Larva — The stage after the egg in a mosquito's life cycle, preceding the pupa.
• Pupa — The mosquito stage following the larva and giving rise to the adult.
• Spawn — A cluster of frog eggs appearing as a jelly-like substance in water.
• Tadpole — A young frog stage with a tail, initially without legs and later developing hind legs.
• Froglet — A little frog developing from a tadpole, beginning to spend some time on land.

Common errors and misconceptions

• Misconception: Anything that moves is living. Correct: A car moves but does not grow. Movement alone is insufficient for classifying something as living.
• Misconception: Plants show no movement because they remain in one place. Correct: Flowers open, Drosera hairs move inward, and climbers wind around nearby objects.
• Misconception: Breathing and respiration mean exactly the same thing. Correct: Breathing is the movement of air into and out of the body and forms part of respiration.
• Misconception: Touch is the response of a touch-me-not plant. Correct: Touch is the stimulus; folding of the leaves is the response.
• Misconception: Every seed requires light to germinate. Correct: Most seeds do not require light for germination. Bean seeds can germinate without light, while some other seeds require it.
• Misconception: Excess water must improve germination. Correct: Bean seeds need the right amount of water and air. Excess water can prevent access to air in soil spaces.
• Misconception: A mosquito develops from an egg into a pupa and then a larva. Correct: Its order is egg, larva, pupa and adult.
• Misconception: A tadpole's tail remains throughout the frog's life. Correct: The tail helps a tadpole swim, but it is lost completely as the frog develops.

Exam-style questions with model answers

Q1. A car moves but does not grow. A plant stays in one place but grows and its flowers open. Explain in two points why movement alone cannot identify living beings. [2 marks]

1. The car's movement does not make it living; its failure to grow shows why other characteristics must also be considered.
2. The plant is living despite remaining in one place. Its growth and opening flowers show characteristics of life, including movement of parts.

Q2. A touch-me-not plant folds its leaves when touched. Define stimulus and response using this observation, and explain what it shows about plants. [3 marks]

1. A stimulus is something or an event that prompts a living being to respond. In this observation, touching the plant provides the stimulus.
2. A response is the reaction to the stimulus. Here, the folding of the plant's leaves is the response to touch.
3. The observation shows that plants respond to stimuli. They do not need to move from place to place to show this characteristic of life.

Q3. Four identical pots each contain garden soil and four bean seeds. Pot A is dry in sunlight; B has excess water above the soil in sunlight; C has slightly moist soil in darkness; D has slightly moist soil in sunlight. Predict germination in each pot and explain each prediction. [4 marks]

1. Pot A is not expected to show germination because the seeds lack water, which is required for the processes involved in growth.
2. Pot B is not expected to show germination because excess water prevents access to the air required by the seeds.
3. Pot C is expected to show germination because it provides moisture and air. Bean seeds do not require light to germinate.
4. Pot D is expected to show germination because moisture and air are available. Its sunlight does not prevent bean-seed germination.

Q4. Three bean seedlings receive moisture from wet blotting paper while remaining above the water level. A is upright in sunlight from all directions; B is inverted in the same light; C is upright in a box receiving light through one hole. Give the expected root and shoot directions for A, B and C separately, then explain why moisture is available and what C demonstrates. [5 marks]

1. In A, the root grows downwards and the shoot grows upwards. The upright position allows the two directions to be observed directly.
2. In B, the root bends and grows downwards, while the shoot bends and grows upwards, although the seedling began upside down.
3. In C, the shoot grows towards the light entering through the hole, while the root continues growing downwards.
4. Moisture reaches the seedlings through the wet blotting paper. The seedlings remain above the water level while the paper supplies the moisture.
5. Beaker C demonstrates movement towards sunlight through shoot growth. The root and shoot do not both grow towards the opening that admits light.

Q5. Arrange these bean-plant stages in life-cycle order and explain each briefly: appearance of fruits containing seeds, appearance of flowers, seed, appearance of leaves, seed germination. Include how the next generation begins. [5 marks]

1. The seed comes first. It contains the tiny embryo that can develop into a plant when suitable conditions for germination are available.
2. Seed germination follows. The seed turns into a sprout, beginning the visible development of the young plant under suitable conditions.
3. Leaves appear as the young bean plant grows. This stage comes before the plant matures sufficiently to produce its flowers.
4. Flowers appear on the maturing plant. Further changes follow, including the development of fruits from the flowers.
5. Fruits appear as pods containing seeds. These seeds can germinate into a new generation of bean plants, continuing the life cycle.

Q6. A mosquito's life stages are egg, larva, pupa and adult. Describe the sequence in four points, including where the female lays eggs and what happens immediately after the adult emerges. [4 marks]

1. The adult female mosquito lays eggs directly on or near water. The egg is the first stage of the life cycle.
2. The egg develops into a larva. The larva lives in water and comes to the surface to obtain air for respiration.
3. The larva grows into a pupa. This stage also lives in water and requires access to air at the surface.
4. The adult emerges from the pupa, rests briefly on the water surface and then flies away. Egg laying continues the cycle.

Q7. Compare a tadpole, froglet and adult frog in three points. Relate the tail and legs to their movement and describe where each stage lives. [3 marks]

1. A tadpole lives in water. Its tail helps it swim; an early tadpole has no legs, while a later tadpole develops hind legs.
2. A froglet has legs and a remaining tail that helps it swim. It still lives in water but begins spending time on land; as it grows, its tail disappears and its legs strengthen for jumping.
3. An adult frog has lost its tail completely. Strong legs help it jump and land, and it lives both in water and on land.

Q8. Sweat contains water and salts removed as waste. Grasses and roses can release excess water and minerals as leaf droplets. What common life process do these illustrate? Explain using both observations. [2 marks]

1. Both illustrate excretion, the removal of waste products. In the body, sweat carries away water and salts as wastes.
2. Grasses and roses also excrete, releasing excess water and minerals in small leaf droplets. Excretion occurs in plants as well as animals.

Key takeaways

• Living beings move, need food, grow, respire, excrete, respond to stimuli, reproduce and eventually die.
• Plants show movements in their parts even though they do not move from place to place.
• Breathing forms part of respiration, while excretion removes waste products from the bodies of living beings.
• Bean seeds need the right amount of water and air; most seeds do not require light for germination.
• During germination, roots generally grow downwards and shoots upwards; shoots can also grow towards sunlight.
• A bean plant develops from a seed and produces new seeds inside pods, continuing its life cycle.
• Mosquitoes develop through egg, larva, pupa and adult stages, with larvae and pupae living in water.
• Frogs develop through egg, tadpole, froglet and adult stages, with changes in their tails, legs and habitat.

Test yourself

What is the difference between a stimulus and a response in touch-me-not?

Touch is the stimulus that prompts a reaction. Folding of the leaves is the plant's response.

How do stomata help plants?

Stomata are tiny pores on leaf surfaces that help plants take air in and out.

What does water do to the seed coat?

Water softens the seed coat and helps the tiny embryo inside develop into a plant.

Why should germination not be confused with later seedling growth?

Bean seeds can germinate without light, but sunlight is required for the seedling's further growth after germination.

What happens when a growing seedling is inverted?

The root bends and grows downwards, while the shoot bends and grows upwards.

Why do mosquito larvae and pupae come to the water surface?

They live in water but need air for respiration, so they come to the surface for air.

What is spawn?

Spawn is a cluster of frog eggs appearing as a jelly-like substance in water.

How does reproduction maintain continuity of life?

It produces new living beings of the same kind, allowing another generation to grow and develop.