Class 6 Science Chapter 10 Notes Living Creatures: Exploring their Characteristics

→ The objects around us can be categorized into two types living and non-living.

→ The essential features of living beings are that they move, eat, grow, breathe, excrete, respond to stimuli, reproduce, and die. The absence of any of these features indicates that they are not living beings.

→ Each living being goes through several stages during its life.

→ Germination of seeds depends upon the availability of water, air, and suitable light and/or dark conditions.

→ During germination of seeds, roots generally grow downwards, while shoots grow upwards.

→ A plant’s life cycle starts with seed germination, followed by several stages of its growth and development. These include flowering and seed production. Seeds produced during their life cycle would germinate into new plants and the cycle continues.

→ The life cycle of an animal as a result of reproduction, begins with a newborn that undergoes various stages of growth and development followed by an adult stage and finally death. The process of reproduction maintains the continuity of its kind.

→ Mosquitoes pass through the stages of egg, larva, pupa and adult. The life stages of a frog include eggs, tadpoles, froglets, and adults.

→ In some living beings, such as mosquitoes and frogs, significant changes occur during the various stages of their life cycles. These changes can be seen in body shape, structure, and sometimes even in the habitat.

Avadhi and Aayush go for a morning walk with their parents. Avadhi notices some shells and tries to pick them up. Her mother advises her not to do so and explains that the shell could be home to a living snail and is a part of its body. Avadhi and Aayush wonder how the shell that is not even moving could have a living being inside! Later that day in school, Avadhi and Aayush share this incident with their friends. They approach the teacher to understand how a shell that is not even moving could be a body part of a living snail. The teacher initiates a discussion in the class on living and non-living.

Activity 10.1 Let Us Record
We are surrounded by numerous things. Just look around in your classroom and you may find many examples – the pencil that you are holding, the book that you are reading, or the pigeon near the window.

• List them in the Table and identify each of them as living or non-living based on your understanding in column II.
• Write a reason for grouping them as living or non-living in column III.

What Sets the Living Apart from the Non-living?

Look at Table. Why do you think a pencil is non-living but a pigeon is living? What do you think are the differences between living beings and non-living things according to you? What similarities do the identified living beings share? You may have identified movement as one of the similarities among living beings. You have also seen cars moving on the road. Does it mean that a car is living? List the tasks that you can do but a car cannot. You are a wonderful example of a living being.

Whenever you attempt to group things around you as living or non-living, you can compare them with yourself. Which characteristics help you differentiate yourself from a car? For instance, a car does not grow. Does it mean it is non-living? Now, which characteristics have you used to classify a car as non-living? Continue your discussion in a similar way to identify the essential characteristics of living beings. What are some common characteristics that make living beings very different from non-living things? Let us learn about them.

Can we consider movement as one of the characteristics to differentiate between the living and the non-living? List five things around you that can move on their own. Do you think that all fie things that you have listed can be considered as living just because they can move on their own? However, unlike animals, plants do not move from one place to another. Do you consider them as living?

Even though plants do not move from one place to another, they do show certain types of movements. The opening of flowers is one of the examples of movement in plants. Another example of movement in plants is seen in insectivorous plants. Insectivorous plants are dependent on insects for their nutrition. Drosera is one of the examples of an insectivore. Drosera is featured with saucer-shaped leaves having many hair-like projections of unequal length with sticky ends. Whenever an insect enters the saucer, hairs move inward and trap the insect with their sticky ends. Try to observe the mechanism of movement in other insectivorous plants. Climbers also wind themselves around any object placed close to them. That means, that even though plants do not move from one place to another, they do show some movements.

Compare yourself with the picture of your childhood. Can you wear the dress that you used to wear four years ago? No, because you have become larger. This is due to growth in your body. Plants and other living beings also grow. Can we consider growth as a characteristic of living beings? Living beings need food (nutrition) for their growth and development. List five living beings that require food to grow.

Now, think of a process without which we cannot live. Count the number of breaths you take per minute after a normal walk, after a run, and after a few dance steps. Record the data and observe. Do you notice any difference in the number of breaths after each situation? Do you notice the process of breathing in other animals like dogs, cats, cows, and buffaloes? Notice the movement of their abdomen while they are taking rest.

In the process of breathing, when we inhale, the air moves from outside to inside our body. When we breathe out, the air moves from inside our body to outside. Breathing is part of a process called respiration. Do plants also respire? There are tiny pores called stomata on the surface of leaves. These pores help plants take air in and out. Interact with senior class students in your school and request if they can demonstrate stomata using a microscope in your class. All living beings respire.

Have you noticed white patches forming on shirts around the armpits during summer? These patches are formed due to sweat. The sweat consists of water and salts removed by the body as waste products. Removal of waste products from the body is called excretion. Urine is also formed as a product of excretion in animals. Do you know that plants also excrete? You may notice plants excrete excess water and minerals in the form of small droplets on leaves. For example, grasses and roses. All living beings excrete.

Let us look at another characteristic. What is your reaction if you unexpectedly step on a sharp object, such as a thorn, while walking without shoes, or if you accidentally touch a hot cup of tea? Stepping on a thorn and touching a hot object are stimuli. Anything or any event that prompts living beings to respond is called a stimulus. List three stimuli (plural of stimulus) and your body’s instant response to them.

Do plants also respond to stimuli? Yes, plants also respond to stimuli. For example, touch me-not (mimosa, chai-mui, lajjalu) plants fold their leaves when we touch them. Have you also observed that certain plants fold their leaves after sunset? Specifically, the leaves of certain plants facing each other tend to come together. This can be observed in the sleeping leaves of the amla (Indian gooseberry) tree. All living beings respond to stimuli. Find a few more plants in your neighborhood that fold their leaves after sunset.

Why do the leaves of chai-mui and amla plants respond in this way? Which stimulus could be responsible for their behavior? Have you seen young ones of cats, dogs or other animals? List young ones of fie different animals. Have you seen young ones of any non-living things such as a pencil, a chair or an electric bulb? All living beings reproduce. Reproduction is the process of producing new ones of one’s kind. Why is reproduction necessary? It is necessary for the continuity of life.

When a living being is not able to exhibit all of the above-mentioned characteristics, despite the availability of all resources (like food, air, and water) needed for being alive, it is said to be dead. From the above discussion, we can understand that all living beings share some common characteristics. For example, all living beings show movement, they need food, and they grow. They also respire, reproduce, excrete, respond to stimuli, and eventually, die. The absence of any of these features indicates that they are non-living things. Now that you know how to identify a living being, fill up the remaining two columns (IV and V) of Table 10.1 and complete the activity. In which category would you place a seed-living or nonliving? Why? Let us explore how a seed germinates to observe some of these essential characteristics in plants.

Essential Conditions for Germination of a Seed

Have you observed a seed germinating? You might have wondered what conditions are required for the germination of a seed. What conditions do you think are required for seed germination? How will you investigate whether these conditions have an effct on the germination of a seed? Let us find out by performing Activity 10.2.

Activity 10.2 Let Us Experiment
Take four identical pots filled with garden soil. Sow four bean seeds in each pot. Now, keep these pots in the following conditions for 15 days.

• Pot A: Do not water the soil. Place this pot in direct sunlight.
• Pot B: Add excess water to the soil such that water is always present above the soil. Keep adding water regularly if water reduces. Place this pot in direct sunlight.
• Pot C: Keep the soil in this pot slightly moist by adding a moderate amount of water regularly. Place this pot in a dark location.
• Pot D: Maintain the soil in this pot slightly moist by adding a moderate amount of water regularly. Place this pot in direct sunlight.

Indicate the availability of air, sunlight, and water for the seeds in each of these cases in Table. When a seed turns into a sprout, it is said to have germinated. Predict whether the seeds in each pot will germinate. Record your predictions for each pot kept under different conditions in Table. Regularly observe the pots for 7-10 days to check the status of germination of the seeds. Record your observations in Table. Compare your predictions with your observations.

Do you think sunlight is necessary for the germination of seeds? Do the seeds in all the pots receive air, water, and sunlight? Is there any pot in which air is not available to the seeds? If so, why is it not available? What happens to the seeds in the pot where water is provided in excess? Which seeds receive both air and water? Identify the pots where you can notice the germination of seeds. Do your observations match with your predictions? Write possible reasons in favor of your observations in Table.

Based on your observations, state the conditions that favor seed germination. Which of the following are essential for seed germination – air, water, and sunlight? Compare the available conditions in each pot. Germination of bean seeds requires the right amount of water and air. Why do seeds require these conditions for germination? Do you think that the absence of one or more of these conditions will affect seed germination? Let us understand how these conditions help in seed germination. The effects of the following conditions have been seen in Activity 10.2.

Water:
Seeds require water for germination. Water enables the seeds to carry out the processes necessary for their growth. The outer covering of the seed is called the seed coat. Water softens the seed coat and helps the tiny embryo inside it to develop into a plant.

Air and Soil:
Seeds need air for germination. They use the air available in the spaces between soil particles. Moreover, spaces between the soil particles allow roots to grow easily.

Light and/or Dark Conditions:
We have learned that for the bean seeds, the presence of light is not essential for their germination. In general, most seeds do not require light for germination. However, after germination, sunlight is required for further growth of the seedling.

Some seeds of flowering plants, like Coleus and Petunia, require light to germinate. Covering these seeds with soil inhibits their sprouting. Seeds of flowering plants, like Calendula and Zinnia, need darkness to germinate. These seeds should be covered with sufficient soil.

In the Chapter ‘Mindful Eating: A Path to a Healthy Body’, you have learned that human beings need a balanced diet for good health and proper growth. Similarly, plants too need favorable conditions and nutrients for their proper growth and development. What other conditions do you think would affect seed germination?

In Activity 10.1, what are the characteristics of living beings that made you place plants in living beings? Do plants show growth in Activity 10.2? Are there any other characteristics of living beings that these plants show? Let us study another characteristic that can be seen clearly in plants – growth and movement.

Growth and Movement in Plants

How do plants respond to sunlight? Does sunlight affect the direction of growth of different parts of plants? In which direction would the root and shoot of a plant grow and move if the plant is placed inverted? How would you design an activity to find answers to these questions?

Activity 10.3 Let Us Design
Take some bean or gram seeds and allow them to germinate on a moist cloth or a moist tissue paper. Let them germinate until each of them develops into a seedling having a small root and a small shoot. Now, take three glass beakers or tumblers, and label them as A, B, and C. Take three glass plates and attach a thick blotting paper to one side of each plate using a thick soft cotton thread. Fix one seedling on each plate using a thick soft cotton thread, as shown in Figure, ensuring that the plant is not damaged. Now, place one glass plate upright with a seedling attached to each of beaker A and beaker C, as shown in Fig. a and Fig. c. In beaker B, arrange the plate such that the shoot of a seedling is directed downwards and the root is directed upwards, as shown in Fig. b.

Pour water into all three beakers to ensure that the seedling in each beaker remains above the water level. In each case, let the bottom of the blotting paper get completely wet by soaking in the water. In this way, the seedling will get the moisture from the wet blotting paper. Place beaker A and beaker B in sunlight as shown in Fig. a and Fig. b. Position beaker C as shown in Fig. c. Place a cardboard box in such a way that the seedling gets light from one direction only through a small circular hole. Fill the Table with your predictions and observations.

What is the direction of growth of root and shoot in beakers A, B, and C based on your observations? Do your predictions match your observations? What do you conclude from this activity?

From the results of this experiment (Table and Figure), we note that-

1. When the plant is kept upright, the root grows downwards and the shoot grows upwards.
2. When the plant is kept inverted, the root bends and grows downwards. Also, the shoot bends and grows upwards.
3. When the plant gets sunlight only from one direction, the shoot grows in the direction of light while the root continues to grow downwards.

After conducting Activity 10.3, we can conclude that the shoots of plants grow upward and exhibit movement toward sunlight but the roots of plants grow downward.

Jagadish Chandra Bose (1858-1937) was an Indian scientist who did some fascinating experiments with plants. He built a machine called a crescograph to record how plants respond to stimuli like light, heat, electricity, and gravity. With this machine, he could measure how fast plants grow. He also showed that plants can sense and respond to stimuli.

Life Cycle of a Plant

We have learned about the conditions required for germination and how plants grow and exhibit movement. Let us now explore the changes a plant undergoes in its whole life.

Activity 10.4 Let Us Explore
Plant a bean seed and provide suitable conditions for its growth. Observe regularly for three months. Record your observations in Table as and when changes become visible. Note the date when any change is observed. Record answers for the following questions:

• How long does it take for any change to occur? Make sketches of various changes that you observe in Table.
• After how many days does the first flower appear?
• After some parts of the flower have dried, can you see any further growth?
• Which structure do the remaining parts of the flower develop into?
• Can you notice a pod or a fruit with seeds develop from a flower?
• What happens to the plant after the fruits containing seeds are formed?

Go through the observations you recorded regarding the growth of the bean plant in Table. What changes do you observe after the fruits are formed? Does the plant become yellow and dry even when you continue watering it? Sow the seeds obtained from your bean plant. Watch how the seeds give rise to a new generation of bean plants. Compare the sketches that you have drawn in Table with Figure.

A seed grows into a young plant and matures to produce flowers and fruit. The fruit, in this case, a pod, contains seeds that give rise to a new generation of bean plants. The entire process from a seed to a plant, and then, to the next generation of seeds is called the life cycle of a plant (Figure). When a plant stops growing and all activities of life gradually come to an end, even after the availability of all the necessary conditions, the plant is considered dead.

Life Cycle of Animals

We have learned about the life cycle of a plant. We have seen that a plant goes through many changes in its life cycle. Have you ever observed how animals grow over time? Draw sketches of their young ones and name them.

Life Cycle of a Mosquito
Mosquitoes buzzing around is a common experience for all of us. Female mosquitoes are bloodsucking insects that transmit several diseases like malaria, dengue, and chikungunya. You might have learned from newspapers, school noticeboards, or awareness campaigns that mosquito breeding should be prevented. We are advised not to allow water to stagnate anywhere in our surroundings. Why is it so? Does stagnant water have any relation with mosquitoes laying eggs?

Conduct a safety audit in your school, or at your home and surroundings to check for stagnant water (if available, carry a hand lens to observe any small creatures). Some common places where stagnant water is likely to gather are desert coolers, planted pots, and any open container. You may find two different types of worm-like creatures (Figure). They are larva and pupa, two distinct life stages during the development of mosquitoes. In case you observe larvae and pupae, report to your teacher. Discuss with the teacher and classmates about the necessary measures one can take to prevent the breeding of mosquitoes. What differences do you observe in the shape of larvae and pupae?

Mosquito larvae and pupae observed in water bodies repeatedly come to the water surface. What can be the reason for this? Mosquito larvae and pupae live in water and require air to respire. They move to the surface of the water for air.

Activity 10.5 Let us Analyse
Let us solve an interesting puzzle. How will you decide which stage (larva or pupa) comes immediately after the egg stage? Suppose you are given a container with water from a puddle containing larvae and pupae. Design an activity to find out the correct sequence of these stages.

You can take help of the following activity designed by Avadhi to create your activity-

• Step 1: I have a water container with mosquito larvae and pupae.
• Step 2: I will separate 4-5 larvae and pupae into two separate containers with the same water.
• Step 3: I will observe them every day until I see them changing to the next stage.
• Step 4: If the larvae change into pupae, it would mean that the larval stage comes before the pupal stage or vice-versa.
• Step 5: I will keep watching both containers to see in which one a mosquito appears first.

These observations will help us to learn the correct sequence of growth. Now, suppose you are given a container filled with water from a puddle that contains larvae and pupae. Without separating them from the container, how would you design an activity to decide which stage, out of the two, gives way to the next?

Let us learn more about these stages in the life cycle of a mosquito. Mosquitoes pass through four stages in their life cycle – egg, larva, pupa, and adult (Figure). The adult mosquito that emerges from the pupa rests briefly on the surface of the water and then flies away. The adult mosquito may survive for 10 to 15 days. We have seen that a mosquito begins its life as an egg (stage I), the egg develops into a larva (stage II), the larva grows into a pupa (stage III), and the pupa transforms into an adult mosquito (stage IV). The adult female mosquito lays eggs directly on or near water, and the cycle continues.

Significant changes occur in the appearance, body shape, and structure during the various stages of the life cycle of a mosquito. The shape of the egg is quite different from the larva; the larva appears very different from the pupa. The pupa appears very distinct from the adult mosquito. Is it easy to imagine that a mosquito emerges from a pupa?

The silk moth also passes through four life stages – egg, larva, pupa, and adult. Eggs hatch into larvae, which then grow in size. Larvae secrete thread-like material which they wrap around themselves, before changing to pupae. These are the fires that are used to make silk fabric. In India, the Khadi and Village Industries Commission (KVIC) has set up several centers for silk production.

Life Cycle of a Frog

Activity 10.6 Let us Analyse
Avadhi and Aayush are dressed up in full-sleeved shirts and full pants today. It has been raining intermittently for a week. They are going out with their classmates for an activity. After a brief walk led by their science teacher, they reach a shallow pond. It is surrounded by trees and tall grasses. The teacher cautions them to watch everything from a distance without causing any disturbance. You may also go to a small water body during the rainy season with a facilitator and explore it by taking due safety precautions.

You may notice a white jelly-like substance on the surface of the water towards the edge of the pond (Figure). This may also be attached to plants growing in or around the water. This jelly-like substance is a cluster of eggs of a frog and is known as spawn. Observe the features of all the stages of a frog shown in Figure. How will you decide the sequence of the given stages (A, B, C, D, E, F)? Some of the stages show distinct changes in their initial and final shapes. Record these changes in Table.

Based on the observations listed in Table, draw the life cycle of a frog. Compare the figure drawn by you with the Figure.

Some of the stages have been clubbed together, for example, stages A and F in Figure have been kept under stage I. You will find four stages in the life cycle of a frog – the egg stage, which progresses to the embryo stage; the tadpole stage, consisting of an early stage with a tail and no legs, and a late stage with hind legs; the froglet stage, and the adult frog stage (Figure).

Discuss in the class the following points:

• How are these eggs of a frog different from the other eggs that you may have seen?
• Which stage has the shortest duration?
• Is there a change in the habitat during the various stages in the life cycle of a frog?
• How do the special features support that stage?

Observe Figure. You will see that tadpoles develop legs but still have tails. Tails help them swim in water. Tadpoles grow gradually and start looking like little frogs called froglets. They still live in water but begin to spend some time on land. They continue to grow and lose their tails completely. Their legs become strong to help them jump and land. They become fully developed adult frogs living both in water and on land.

Plants and animals are a part of the living world. They go through various changes during their lives. We have learned that a tiny plant grows and develops into a big tree. We have also learned how animals grow and change from young ones to adults. This journey varies for each animal, making it unique and special. We have seen pupae change into insects, and tadpoles change into frogs. Such changes are important for plants and animals to survive and to maintain the continuity of their kind. We should also take care of them and their homes. By nurturing and preserving their homes, we contribute to this flourishing living world.

Class 6 Science Notes

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