Living Creatures: Exploring Their Characteristics

Hello students, welcome to today's science lesson. I am so happy to be here with you to learn about living creatures and their characteristics. This is Chapter 10 from your science textbook, and I promise you, by the end of this lesson, you will understand everything about what makes living beings different from non-living things, how plants grow, and how animals go through different stages in their lives. So let's begin together.

Students, have you ever gone for a morning walk with your parents? Just imagine Avadhi and Aayush, two children like you, who go for a morning walk with their parents. One day, Avadhi notices some beautiful shells on the ground. She tries to pick them up because they look pretty. But her mother stops her and says, "Avadhi, don't pick up that shell. It could be the home of a living snail, and the shell is actually a part of its body." Now, isn't that interesting? Avadhi and Aayush were confused. They thought, "How can a shell that is not even moving have a living being inside it?" They wondered about this the whole day. When they went to school, they shared this incident with their friends, and together they approached their science teacher to understand how a shell that doesn't move could be a body part of a living snail. This is exactly what we are going to learn today.

So students, let's start with Activity 10.1. I want you to look around your classroom. What do you see? You see your pencil, your book, maybe a pigeon outside the window, a car passing by on the road, a plant in the corner, and many other things. Now, I want you to think about each of these things and decide whether they are living or non-living. This is a very important exercise because it will help us understand the difference between living beings and non-living things.

Let's fill up Table 10.1 together. In column I, we write the name of the thing. In column II, we write our guess about whether it is living or non-living. In column III, we write the reason for our grouping.

Let's start with a pencil. Is a pencil living or non-living? A pencil is non-living. Why? Because a pencil cannot move by itself, it cannot grow, it cannot eat food, and it cannot reproduce. It is just made of wood and graphite, but it does not have life in it.

What about a book? A book is also non-living. It cannot move on its own, it cannot grow, it does not need food, and it cannot reproduce. It is just paper with printed words.

What about a pigeon? A pigeon is living. Why? Because a pigeon can move, it can fly, it needs food to eat, it breathes, it grows, and it can have baby pigeons. So a pigeon is definitely a living being.

What about a car? A car is non-living. Yes, I know a car can move on the road, but can it grow? Can it eat food? Can it reproduce? No. A car is made of metal and plastic, and it needs fuel to run, but it does not have life. So it is non-living.

What about a plant? A plant is living. A plant can grow, it needs water and sunlight, it breathes, it reproduces by producing seeds, and it responds to stimuli. So plants are living beings.

Now, students, I want you to think about why we called these things living or non-living. What are the characteristics that make a living being different from a non-living thing? Let's discuss this in detail.

Look at Table 10.1. Why do you think a pencil is non-living but a pigeon is living? What are the differences between living beings and non-living things? What similarities do all living beings share with each other?

You may have noticed that movement is one of the similarities among living beings. But wait, students, cars also move on the road. Does that mean a car is living? No, of course not. So movement alone cannot be the deciding factor. Let's think about what else living beings can do that non-living things cannot do.

List the tasks that you can do but a car cannot. You are a wonderful example of a living being. You can think, you can feel, you can grow, you can eat, you can breathe, you can reproduce, and you can respond to your surroundings. Whenever you try to group things around you as living or non-living, you can compare them with yourself. Which characteristics help you in differentiating yourself from a car? For instance, a car does not grow. Does it mean it is non-living? Yes, that is one of the reasons. Now, which characteristics have you used to classify a car as non-living? Let's continue our discussion to identify all the essential characteristics of living beings.

So students, what are the common characteristics that make living beings very different from non-living things? Let me explain each one of them to you.

First, let's talk about movement. 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. The fan in your classroom can move, but it is powered by electricity, so it is not moving by itself. A flying bird can move on its own. A dog running can move on its own. A fish swimming can move on its own. A snake slithering can move on its own. But do you think all five things that you have listed can be considered as living just because they can move on their own? Yes, they are living because they can move by themselves.

Now, what about plants? Unlike animals, plants do not move from one place to another. Do you consider them as living? Yes, plants are living beings even though they do not move from one place to another. But wait, students, plants do show certain types of movements. Opening of flowers is one of the examples of movement in plants. Have you seen a sunflower that follows the sun? That is movement. 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 insectivorous plant. Drosera has saucer-shaped leaves with many hair-like projections of unequal length with sticky ends. Whenever an insect enters the saucer, the hairs move inward and trap the insect with their sticky ends. Climbers also wind themselves around any object placed close to them. That means, even though plants do not move from one place to another, they do show some movements. So movement is a characteristic of living beings, but not the only one.

Now, let's talk about growth. Compare yourself with a picture of your childhood. Can you wear the dress that you used to wear four years ago? No, because you have become larger in size. 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? Yes, definitely. All living beings grow. A baby grows into an adult. A puppy grows into a dog. A seedling grows into a big plant. So growth is another characteristic of living beings.

Now, let's talk about nutrition. Living beings need food for their growth and development. List five living beings that require food to grow. You need food to grow. A dog needs food. A cow needs grass. A bird needs seeds. A fish needs smaller fish or fish food. A plant needs water and minerals from the soil. So nutrition is essential for all living beings.

Now, let's talk about respiration. 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? Yes, after running or dancing, you breathe faster because your body needs more oxygen. 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. Yes, they also breathe. 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? Yes, they do. There are tiny pores called stomata on the surface of leaves. These pores help plants in taking air in and out. All living beings respire.

Now, let's talk about excretion. Have you noticed white patches forming on shirts around the armpits during summers? 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. You might have seen water droplets on grass blades in the morning. These are called dew, but some of these droplets are actually water excreted by the plants. All living beings excrete.

Now, let's talk about response to stimuli. What is your reaction if you unexpectedly step on a sharp object, such as a thorn, while walking without shoes, or you accidentally touch a hot cup of tea? You immediately pull your foot away or jerk your hand back. 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 and your body's instant response to them. If you touch something hot, you pull your hand away. If a bright light is flashed in your eyes, you close your eyes. If someone shouts unexpectedly, you get startled. These are all responses to stimuli.

Do plants also respond to stimuli? Yes, plants also respond to stimuli. For example, touch-me-not, also called mimosa, chhui-mui, or 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 amla, which is Indian gooseberry tree. All living beings respond to stimuli. Find a few more plants in your neighbourhood which fold their leaves after sunset.

Why do the leaves of chhui-mui and amla plants respond in this way? Which stimulus could be responsible for their behaviour? The stimulus is the absence of light, which indicates that it is night time. The plants fold their leaves to protect themselves or to reduce water loss.

Now, let's talk about reproduction. Have you seen young ones of cats, dogs, or other animals? List young ones of five different animals. A cat has kittens, a dog has puppies, a cow has a calf, a hen has chicks, a fish has fry. Have you seen young ones of any non-living things such as a pencil, a chair, or an electric bulb? No, because non-living things cannot reproduce. All living beings reproduce. Reproduction is the process of producing new ones of one's own kind. Why is reproduction necessary? It is necessary for the continuity of life. If living beings did not reproduce, they would become extinct.

Now, let's talk about death. 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. For example, if a person stops breathing, their heart stops, and they cannot respond to any stimuli, they are said to be dead.

So students, from the above discussion, we can understand that all living beings share some common characteristics. All living beings show movement, they need food, and they grow. They also respire, reproduce, excrete, respond to stimuli, and eventually die. 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, which are column IV and column V of Table 10.1, and complete the activity. In column IV, write the correct answer, and in column V, write the reason for the correct answer.

Now, here is an interesting question for you. In which category would you place a seed, living or non-living? Why? This is a tricky question. Let's think about it. A seed does not move on its own. It does not breathe like we do. But does it grow? Not unless it gets water and suitable conditions. Does it respire? Very slowly, yes. Does it respond to stimuli? Not obviously. So is a seed living or non-living? Actually, a seed is living because it contains a tiny embryo inside it, which can grow into a new plant when given the right conditions. A seed is in a dormant state, which means it is alive but not actively growing. So a seed is a living thing.

Now, let's explore how a seed germinates to observe some of these essential characteristics in plants. This brings us to Activity 10.2.

Have you observed a seed germinating? You might have wondered what conditions are required for germination of a seed. What conditions do you think are required for seed germination? How will you investigate whether these conditions have an effect on the germination of a seed?

Let's find out by performing Activity 10.2. This is a very interesting experiment, students.

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 on a regular basis 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 on a regular basis. Place this pot in a dark location.

Pot D: Maintain the soil in this pot slightly moist by adding a moderate amount of water on a regular basis. Place this pot in direct sunlight.

Now, indicate the availability of air, sunlight, and water for the seeds in each of these cases in Table 10.2.

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 10.2.

Now, let's fill up the table together. For Pot A, which is kept in direct sunlight but has no water, what are the conditions? Air is available because the soil has air in it. Sunlight is available. Water is not available. So the seed will not germinate because it needs water.

For Pot B, which is kept in direct sunlight but has excess water, what are the conditions? Air is not available because the soil is completely waterlogged, and there are no air spaces. Sunlight is available. Water is available in excess. So the seed will not germinate because it needs air to breathe.

For Pot C, which is kept in the dark but has moist soil, what are the conditions? Air is available. Sunlight is not available. Water is available in moderate amounts. So the seed might germinate because it has air and water, but it might not grow properly because it needs sunlight for photosynthesis after germination.

For Pot D, which is kept in direct sunlight and has moist soil, what are the conditions? Air is available. Sunlight is available. Water is available in moderate amounts. So the seed will germinate properly.

Now, regularly observe the pots for 7 to 10 days to check the status of germination of the seeds. Record your observations in Table 10.2. Compare your predictions with your observations.

Now, let's answer some questions based on this activity. Do you think sunlight is necessary for germination of seeds? From our experiment, we can see that Pot C, which was in the dark, also had germination, so sunlight is not necessary for germination of bean seeds. But after germination, sunlight is required for further growth of the seedling.

Do the seeds in all the pots receive air, water, and sunlight? No. Pot A has air and sunlight but no water. Pot B has water and sunlight but no air. Pot C has air and water but no sunlight. Pot D has all three.

Is there any pot in which air is not available to the seeds? Yes, Pot B has excess water, so there is no air in the soil.

What happens to the seeds in the pot where water is provided in excess? They do not germinate because they do not get air.

Which seeds receive both air and water? Pot C and Pot D receive both air and water.

Identify the pots where you can notice the germination of seeds. Pot C and Pot D should show germination.

Do your observations match with your predictions? Write possible reasons in favour of your observations in Table 10.2. Based on your observations, state the conditions which favour seed germination. The conditions that favour seed germination are the right amount of water and air. Sunlight is not essential for germination but is needed for further growth.

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? Yes, if any of these conditions is missing, germination may not occur.

Now, let's 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 learnt that for the bean seeds, presence of light is not essential for their germination. In general, most seeds do not require light for germination. But after germination, sunlight is required for further growth of the seedling.

Do you know? 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 learnt that human beings need a balanced diet for good health and proper growth. Similarly, plants too need favourable conditions and nutrients for their proper growth and development.

Now, how would you categorise a seed, as living or non-living? A seed is living because it contains a living embryo inside it. When given the right conditions, it germinates and grows into a new plant.

What other conditions do you think would affect seed germination? Temperature is also an important factor. Seeds germinate best at a certain temperature range. Also, the quality of the seed matters. Old or damaged seeds may not germinate.

In Activity 10.1, what are the characteristics of living beings which made you place plants in living beings? Plants show movement, growth, nutrition, respiration, excretion, response to stimuli, and reproduction. Do plants show growth in Activity 10.2? Yes, when the seeds germinate, they grow into seedlings. Are there any other characteristics of living beings that these plants show? Yes, they respire, they excrete, and they respond to stimuli.

Now, let's study another characteristic that can be seen clearly in plants, which is growth and movement. This is Section 10.3.

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?

Let's perform Activity 10.3 to find out.

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.

Now, 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 the figure, ensuring that the plant is not damaged.

Now, place one glass plate upright with a seedling attached into each of the beaker A and beaker C. In beaker B, arrange the plate such that the shoot of a seedling is directed downwards and the root is directed upwards. This is an inverted position.

Pour water into all the 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. Position beaker C as shown in the figure. Place a cardboard box in such a way that the seedling gets light from one direction only through a small circular hole.

Fill Table 10.3 with your predictions and observations.

Now, let's understand what we are testing here. In beaker A, the plant is kept upright, and it gets light from all directions. In beaker B, the plant is inverted, and it gets light from all directions. In beaker C, the plant is kept upright, but it gets light from only one direction.

Now, let's make predictions. For beaker A, the plant is upright, so we predict that the root will grow downwards and the shoot will grow upwards. For beaker B, the plant is inverted, so we predict that the root might grow upwards and the shoot might grow downwards. But actually, what happens? Let's see.

From the results of this experiment, we note that when the plant is kept upright, the root grows downwards and the shoot grows upwards. When the plant is kept inverted, the root bends and grows downwards. Also, the shoot bends and grows upwards. When the plant gets sunlight only from one direction, the shoot grows in the direction of light while the root continues to grow downwards.

So students, what is the direction of growth of root and shoot in beakers A, B, and C based on your observations? In beaker A, the root grows downwards and the shoot grows upwards. In beaker B, the root initially grows upwards but then bends downwards, and the shoot initially grows downwards but then bends upwards. In beaker C, the root grows downwards, and the shoot grows towards the light.

Do your predictions match your observations? What do you conclude from this activity?

We can conclude that shoots of plants grow upward and exhibit movement towards sunlight, but roots of plants grow downwards. This phenomenon is called phototropism for shoots, which means movement towards light, and geotropism for roots, which means movement towards gravity.

Now, students, let me tell you about a famous Indian scientist. Jagadish Chandra Bose 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. He was a pioneer in the field of plant physiology, and his work showed that plants are indeed living beings that respond to their environment.

Now, let's move on to Section 10.4, which is about the Life Cycle of a Plant.

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

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

Here are some questions to answer. How long does it take for any change to occur? Make sketches of various changes that you observe. 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 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?

Now, let's understand the life cycle of a plant. A seed grows into a young plant and matures to produce flowers and fruit. The fruit, in this case a pod, contains seeds which 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. 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.

So students, the life cycle of a plant includes the following stages. First, the seed is sown. Then, the seed germinates, and a seedling emerges. The seedling grows into a young plant. The young plant grows into a mature plant. The mature plant produces flowers. The flowers develop into fruits. The fruits contain seeds. The seeds can be sown again to grow new plants. And so the cycle continues.

Now, let's move on to Section 10.5, which is about the Life Cycle of Animals.

We have learnt 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.

Let's learn about the life cycle of a mosquito first.

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 learnt 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? Yes, because mosquitoes lay their eggs in stagnant water.

Conduct a safety audit in your school, or at your home and surroundings to check for stagnant water. 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. They are larva and pupa, two distinct life stages during the development of a mosquito. 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 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.

Now, let's solve an interesting puzzle in Activity 10.5. 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 own activity.

Step 1: I have a water container with mosquito larvae and pupae.

Step 2: I will separate 4 to 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 the 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 which 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?

You could observe the container daily and note which stage transforms into an adult mosquito first. If you see adult mosquitoes emerging from the container, you can note which stage was present in the container just before the adult appeared.

Now, let's learn more about these stages in the life cycle of a mosquito. Mosquitoes pass through four stages in their life cycle, which are egg, larva, pupa, and adult.

The adult mosquito that emerges from the pupa rests briefly on the surface of 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, which is stage I. The egg develops into a larva, which is stage II. The larva grows into a pupa, which is stage III. The pupa transforms into an adult mosquito, which is 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 in 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? It might seem strange, but it is true.

Do you know? The silk moth also passes through four life stages, which are 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 fibres that are used to make silk fabric. In India, the Khadi and Village Industries Commission has set up several centres for silk production.

Now, let's learn about the life cycle of a frog.

Let's perform Activity 10.6. Avadhi and Aayush are dressed up in full-sleeve 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 water towards the edge of the pond. This may also be attached to plants growing in or around the water. This jelly-like substance is actually a cluster of eggs of a frog and is known as spawn.

Observe the features of all the stages of a frog. How will you decide the sequence of the given stages? Some of the stages show distinct changes in their initial and final shapes. Record these changes in Table 10.5.

Based on the observations, draw the life cycle of a frog. Compare the figure drawn by you with the figure in your textbook.

Now, let's understand the life cycle of a frog. There are four stages in the life cycle of a frog. The first stage is the egg stage, which progresses to the embryo stage. The second stage is the tadpole stage, consisting of an early stage with a tail and no legs, and a late stage with hind legs. The third stage is the froglet stage, and the fourth stage is the adult frog stage.

In the egg stage, the female frog lays eggs in water. The eggs are covered with a jelly-like substance. The eggs hatch into tadpoles. The tadpole stage is the second stage. Initially, the tadpole has a tail and no legs. It lives in water and breathes through gills. Gradually, the tadpole develops hind legs first, and then forelegs. This is the third stage, which is the froglet stage. The froglet still has a tail but looks more like a frog. It begins to spend some time on land. Finally, the tail disappears, and the froglet becomes an adult frog. The adult frog lives both in water and on land.

Now, let's discuss some points in class. How are these eggs of a frog different from the other eggs that you may have seen? Frog eggs are laid in water and are covered with a jelly-like substance, unlike chicken eggs, which are laid on land and have a hard shell.

Which stage has the shortest duration? The duration varies, but generally, the egg stage is relatively short, lasting a few days.

Is there a change in the habitat during the various stages in the life cycle of a frog? Yes, initially, the eggs and tadpoles live entirely in water. The froglet starts spending some time on land, and the adult frog lives both in water and on land.

How do the special features support that stage? The tail in the tadpole helps it swim in water. The gills help it breathe in water. As it grows into a frog, it develops legs for jumping, and its lungs develop for breathing air.

Now, students, do you think that birds also show significant changes in the various stages of their life cycle? Yes, birds also go through changes, but the changes are not as dramatic as in frogs or mosquitoes. Baby birds look like smaller versions of adult birds, whereas tadpoles look very different from adult frogs.

How does the life cycle of animals differ from that of plants? Plants start from seeds, while animals start from eggs or are born from their mothers. Plants usually stay in one place, while animals can move around. Both go through growth and development stages.

Plants and animals are a part of the living world. They go through various changes during the course of their lives. We have learnt that a tiny plant grows and develops into a big tree. We have also learnt 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 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.

Now, students, let's go through the keywords and then the exercises.

The keywords are breathing, movement, conclude, death, non-living, excretion, nutrition, froglet, pupa, germination, reproduction, growth, larva, life cycle, tadpole, living, response, stimulus, and non-living.

Now, let's solve the exercises in the Let Us Enhance Our Learning section.

Question 1: List the similarities and differences in life cycles of plants and animals.

Similarities: Both plants and animals start life, grow, develop, reproduce to produce new individuals, and eventually die. Both require certain conditions for their growth and development.

Differences: Plants usually start from seeds, while animals start from eggs or are born from their mothers. Plants are usually stationary, while animals can move around. In plants, the changes are more gradual, while in some animals like frogs and mosquitoes, the changes are dramatic, which is called metamorphosis.

Question 2: The table shows some data. Study the data and try to find out examples appropriate for the conditions given in the second and third columns. If you think that an example for any of the conditions given below is not possible, explain why.

The table has four rows. Row 1: Does it grow? No. Does it respire? No. Example: A rock. A rock does not grow and does not respire because it is non-living.

Row 2: Does it grow? No. Does it respire? Yes. Example: This is not possible because if something respires, it is living, and all living things grow. So there cannot be something that respires but does not grow.

Row 3: Does it grow? Yes. Does it respire? No. Example: This is not possible because if something grows, it is living, and all living things respire. So there cannot be something that grows but does not respire.

Row 4: Does it grow? Yes. Does it respire? Yes. Example: A plant, an animal, a human being. These are all living things that grow and respire.

Question 3: You have learnt that different conditions are required for seed germination. How can we use this knowledge for proper storage of grains and pulses?

For proper storage of grains and pulses, we should keep them in a dry and cool place. This is because moisture and warmth can cause the seeds to germinate, which would spoil the grains. We should also ensure that there is proper ventilation so that the seeds do not get too much humidity. By controlling the conditions of air, water, and temperature, we can prevent the grains from germinating and keep them fresh for a long time.

Question 4: You have learnt that a tail is present in a tadpole but it disappears as it grows into a frog. What is the advantage of having a tail in the tadpole stage?

The tail helps the tadpole swim in water. It acts like a paddle or a fin, allowing the tadpole to move around in the water and escape from predators. As the tadpole grows into a frog, it develops legs for jumping, and the tail is no longer needed, so it disappears.

Question 5: Charan says that a wooden log is non-living as it cannot move. Charu counters it by saying that it is living because it is made of wood obtained from trees. Give your arguments in favour or against the two statements given by Charan and Charu.

Charan's argument: A wooden log cannot move by itself, it cannot grow, it cannot respire, it cannot reproduce, and it cannot respond to stimuli. Therefore, it is non-living. This argument is correct.

Charu's argument: A wooden log is made of wood obtained from trees, which are living beings. However, once the wood is cut from the tree, it no longer has life processes. Therefore, the wooden log is non-living. This argument is incorrect because the log itself is not alive, even though it came from a living tree.

Question 6: What are the similarities and distinguishing features in the life cycles of a mosquito and a frog?

Similarities: Both mosquitoes and frogs lay their eggs in or near water. Both go through four distinct stages in their life cycle. Both undergo significant changes in their body shape and structure during their life cycle. Both start their life in water.

Differences: Mosquitoes lay eggs on the surface of water, while frogs lay eggs in clusters called spawn in water. Mosquito larvae and pupae live in water and breathe air from the surface, while frog tadpoles breathe through gills. Mosquitoes complete their life cycle in a few weeks, while frogs take several months. Mosquitoes can fly as adults, while frogs cannot fly.

Question 7: A plant is provided with all the conditions suitable for its growth. Draw what you expect to see in the shoot and the root of the plant after one week. Write down the reasons.

If a plant is provided with all the suitable conditions, the root will grow downwards, and the shoot will grow upwards. The root grows downwards because of geotropism, which is the response to gravity. The shoot grows upwards because of phototropism, which is the response to light. The plant will show new leaves and stems, and the overall size will increase.

Question 8: Tara and Vijay set up the experiment shown in the picture. What do you think they want to find out? How will they know if they are correct?

Without the picture, I cannot say exactly what Tara and Vijay's experiment is about. But based on the context, they might be testing the effect of light on plant growth. They will know if they are correct by observing the direction of growth of the plant. If the plant grows towards light, then light does affect the direction of growth.

Question 9: Design an experiment to check if temperature has an effect on seed germination.

To check if temperature has an effect on seed germination, we can set up an experiment with three pots of seeds. Keep one pot in a refrigerator, which is cold. Keep one pot at room temperature. Keep one pot in a warm place, like near a heater. Give all three pots the same amount of water and air. Observe which pot shows germination first and which ones do not germinate at all. This will help us understand the effect of temperature on seed germination.

Now, let's do the Let Us Create activity. Add more lines to the incomplete poem given below. Include information on the different stages in development of a frog. You may also draw and paint each stage as it appears in your poem.

Here is the poem:

In shaded and grassy bogs, There lived a group of frogs. They happily sang from dusk to dawn, In double bass going on and on. One day sitting beside a reed, Female frogs think it's time to breed.

Now, let me add more lines:

They lay their eggs in the water bright, In jelly-like clusters, a wonderful sight. The eggs hatch into tiny tadpoles, With long tails for swimming, they follow no rules. They breathe with gills in the pond so clear, Growing legs as the days appear.

First hind legs, then forelegs too, Changing shape in every view. The tail gets shorter, the body grows wide, A froglet emerges with pride. Now it can hop on the land nearby, And breathe the air from the sky.

As days pass by, the tail disappears, The froglet grows into an adult, it cheers. It can live in water and on the ground too, The life cycle is complete, brand new. And so the frogs go on their way, Singing songs night and day.

Now, students, let me give you a complete summary of everything we have learned in this chapter.

First, we learned that the objects around us can be categorised into two types: living and non-living. Living beings have certain characteristics that non-living things do not have.

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

Each living being goes through several stages during its life, which is called the life cycle.

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.

So students, that brings us to the end of this chapter. I hope you have understood everything about living creatures and their characteristics. Remember, all living beings are special, and we should take care of them and their homes. Thank you for listening, and see you in the next lesson.