Life Processes In Animals

Hello my dear students! Welcome to today's science class. I'm so happy to see you all here, ready to learn something new and exciting. Today, we are going to study Chapter 9 from your science textbook — Life Processes in Animals. This is going to be a fascinating journey as we explore how animals, including humans, obtain energy from food, how they breathe, and how their bodies carry out these amazing processes that keep them alive. So let's begin!

You know, students, if you look around you and observe the animals in your surroundings, you will notice that animals eat different types of food. Bees and sunbirds suck the nectar from flowers. Human babies and the babies of many other animals feed on their mother's milk. Snakes like pythons swallow their prey whole. Some aquatic animals filter tiny food particles floating in the water and feed on them. Isn't it wonderful how different animals have different ways of eating? But no matter what they eat, all animals need to break down their food into simpler forms to get energy from it.

Now, students, let's understand why this happens. Animals, including humans, obtain energy from food, which enables them to carry out various life processes. The food we eat contains complex components like carbohydrates, proteins, and fats. These complex food components have to be broken down into simpler forms before our body can use them. This breaking down process happens in a long tube called the alimentary canal. The process starts in the mouth and ends at the anus. As food moves through this canal, digestive juices secreted at different parts break it down into simpler forms. These simpler forms of food are then absorbed by different parts of our alimentary canal and transported to various parts of our body to carry out various functions.

So students, let's begin our exploration with nutrition in animals. How do the complex food components get broken down into simpler forms and get used by the body in various animals? Is this process the same in all animals or does it vary? Let us first try to understand this process in humans.

### 9.1.1 Digestion in Human Beings

Let's trace the journey of food inside our body as it passes through different parts of the alimentary canal.

#### Beginning with the Mouth Cavity

The journey of the food you eat begins when it enters your mouth. Your teeth break down the food you eat into smaller pieces by the processes of crushing and chewing. This process of initial breakdown of food into fine pieces is called mechanical digestion. Think about your favourite food. Does your mouth feel watery? This happens because more saliva gets released when you recall your favourite food. Have you noticed this? When you think about something delicious, your mouth starts watering!

Now, students, what do you think is the role of saliva in your mouth? What do you feel when you eat other types of food, such as chapati? Let us find out.

Take a small piece of chapati or a bite-sized portion of boiled rice and chew it properly for about 30 to 60 seconds. At first, the chapati or rice has its usual taste, but as you continue chewing, do you notice a change in taste? The food begins to taste sweet! Have you ever wondered why this happens?

Students, chapati or rice contains starch, which is a type of carbohydrate. Our saliva contains a digestive juice that helps break down starch into sugar. This explains why starchy food like chapati tastes sweet when you chew it for a long time. Saliva helps to break down components of food into simpler ones. This is truly amazing, isn't it?

Now, students, let me tell you about the importance of maintaining good oral hygiene. A healthy mouth requires good oral hygiene. We should brush our teeth and clean our tongue twice a day, and rinse our mouth with water after each meal to prevent tooth decay and bad smell in the mouth. This is something our elders have known for generations, and modern science also confirms these practices.

Now, let's perform an interesting activity to understand the action of saliva on starch. This is Activity 9.1 from your textbook.

In this activity, students, we take two test tubes and label them as A and B. In test tube A, we take one teaspoonful of boiled rice. In test tube B, we take one teaspoonful of boiled rice after chewing it for 30 to 60 seconds. Then we add 3 to 4 millilitres of water in both the test tubes. We note the initial colour of the rice-water mixture in the table given in our textbook. Then we add 3 to 4 drops of iodine solution into each test tube with the help of a dropper. We mix the content of each test tube separately and observe.

Now, what do we observe, students? Did you notice that the colour of boiled rice turned blue-black in test tube A, while in test tube B, the chewed boiled rice either did not change colour or turned only a very light blue-black colour? What causes the change of colour in test tube A? In Grade 6, we learned that iodine gives a blue-black colour when it reacts with starch. So in test tube A, the appearance of the blue-black colour indicates the presence of starch. In test tube B, which contains chewed boiled rice, if there is no change in colour, it indicates that the starch is no longer present. If there is only a slight change in colour, it indicates that starch is present only in very small amount. The starch has been broken down into simple sugars by the action of saliva. This is what we call digestion!

So students, now we know that saliva secretion in the mouth helps break down starch into sugars. This process of breaking complex food components into simpler forms in the body is called digestion. Food is partially digested in the mouth. Let us learn how this partially digested food gets further digested through the alimentary canal.

#### Food Pipe (Oesophagus): A Passage from the Mouth to the Stomach

When you chew your food, your saliva not only helps in digesting the starch but also moistens it, making it soft and easy to swallow. Your tongue helps in mixing chewed food with saliva and pushing this softened food into a long, flexible tube called the food pipe or oesophagus.

But how does the food move down, students? The walls of the food pipe gently contract and relax in a wave-like motion to push the food down into the stomach. This movement takes place throughout the alimentary canal and pushes the food forward. This wave-like motion is called peristalsis. Isn't that interesting?

#### Stomach

Now, students, let's move to the stomach. In the stomach, the walls contract and relax to churn the food. The churned food is then mixed with a secretion from the inner lining of the stomach. The secretion from the stomach contains digestive juice, acid, and mucus.

The digestive juice of the stomach breaks down proteins present in the food into simpler components. The acid not only helps break down proteins but also kills many harmful bacteria that might enter our body with food. The mucus protects the stomach lining from the acid, preventing damage. In the stomach, the food is partially digested and transformed into a semi-liquid mass, preparing it for the next stage of digestion.

Here's a fascinating fact for you, students. How did scientists learn about digestion in the human body? The discovery of how the stomach works happened by chance. In 1822, a man named Alexis St. Martin was accidentally shot in the stomach. He was treated by a doctor named William Beaumont. However, his wound never fully healed, leaving a small permanent hole. This opening allowed Dr. Beaumont to observe digestion in the stomach as it happened. He conducted experiments on how different foods were broken down and studied how emotions affect digestion. This was a landmark discovery in the field of science!

#### Small Intestine

After its journey through the stomach, students, the partially digested food moves into the small intestine. Look at the figure in your textbook. It is a sketch of a stretched-out alimentary canal. Guess how long it is. You will be surprised that although it is called the small intestine, it is almost 6 metres long — almost twice the height of your classroom! You will be surprised to know that the small intestine is the longest part of the alimentary canal.

The small intestine receives digestive secretions from three sources — the inner lining of the small intestine itself, and two more structures associated with the alimentary canal — the liver and the pancreas.

The liver secretes bile, which is mildly basic in nature. Do you remember the neutralisation reaction from the chapter on acids, bases, and salts? Bile neutralises acids present in the food moving down from the stomach and breaks down fats into tiny droplets, making its digestion easier.

The pancreas secretes pancreatic juice, which is also basic in nature and helps neutralise acids present in the food. Additionally, pancreatic juice also breaks down carbohydrates, proteins, and fats. The digestive juice secreted by the wall of the small intestine further breaks down fats, proteins, and partially digested carbohydrates into simpler forms.

Now, students, the most important part — the digested nutrients pass on from the small intestine into the blood present in blood vessels found in the walls of the small intestine. This process is called absorption of nutrients. How are these nutrients absorbed from the small intestine? The inner lining of the small intestine is thin and has thousands of finger-like projections that increase the surface area for efficient nutrient absorption. These finger-like projections allow the digested nutrients to pass into the blood, which carries them to different parts of the body. These nutrients provide energy, support growth and repair, and help the body function properly.

Here's something important for you to know, students. Celiac disease is a condition in which the body reacts to gluten, a protein found in wheat, barley, and rye. This reaction damages the inner lining of the small intestine, where nutrients are absorbed. As a result, the intestine cannot function properly. The only way to manage celiac disease is to avoid foods that contain gluten. Millets like jowar, bajra, and ragi are good alternatives because they are naturally gluten-free. This is why our traditional Indian foods are so healthy!

#### Large Intestine

Now, students, after most of the nutrients are digested and absorbed in the small intestine, what happens to the undigested food? It moves into the large intestine. The large intestine is about 1.5 metres in length. It is shorter than the small intestine. Then why is it called the large intestine? The reason is that it is wider than the small intestine.

The large intestine absorbs water and some salts from the undigested food, thus making the waste semi-solid. This semi-solid waste is called stool. The stool is then stored in the lower part of the large intestine, called the rectum, until the body is ready to get rid of it. Eating fibre-rich foods like fruits, vegetables, and whole grains helps the large intestine function properly by making the stool easier to pass. Finally, it is expelled through the anus — a process known as egestion. This is how your body removes the waste it does not need, keeping you healthy!

Isn't it fascinating how the digestive system works, students? Let me tell you another amazing fact. The large intestine contains various small living organisms, such as bacteria, that help in digestion. They help in keeping our digestive system healthy. They break down undigested food, especially fibre, and produce essential nutrients. Fibre-rich food, and especially fermented foods like curd, buttermilk, shrikhand, kanji, pickles, gundruk, and poita bhat are good for a healthy digestive system and overall well-being. This is why our Indian fermented foods are so good for us!

The importance of digestion in maintaining good health has been recognised for centuries. The Charaka Samhita, an ancient Ayurvedic text, highlights the role of easily digestible foods and the judicious use of spices like ginger, black pepper, and cumin to enhance digestion. Advances in science in the area of nutrition also emphasise eating meals at proper timings, practising mindful eating, and avoiding overeating as key factors in maintaining digestive health.

So students, let me recap what we have learned so far. We learned that food enters the mouth, where teeth mechanically break it down and saliva begins chemical digestion by breaking down starch into sugars. Then the food passes through the oesophagus to the stomach, where it is mixed with digestive juices, acid, and mucus. From there, it goes to the small intestine, where bile from the liver, pancreatic juice from the pancreas, and digestive juices from the intestinal walls complete the digestion. The nutrients are absorbed through the finger-like projections in the small intestine. Finally, the undigested food goes to the large intestine, which absorbs water and salts, and the waste is egested through the anus.

### 9.1.2 Do All Animals Digest Food the Same Way as Humans Do?

Now, students, let me ask you something. Have you ever seen cows keep chewing the food even when they are not actively grazing or eating anything? Why do you think this happens?

Grass-eating animals such as cows and buffaloes partially chew the grass and swallow it into their stomachs. In the stomach, partial digestion of the food takes place. The partially digested food is brought back to the mouth for gradual chewing. This process is called rumination, and these animals are called ruminants. A cow spends about 8 hours a day just chewing the food! The thoroughly chewed food again passes down the alimentary canal for further digestion. This is why cows seem to be chewing all the time — they are digesting their food properly!

Birds do not have teeth, but they have a chamber called a gizzard. Food is broken down by the contraction and relaxation of the walls of the gizzard, often with the help of grit or small stones that the birds swallow. This shows that animals exhibit variations in the structure and function of the alimentary canal to adapt to different ways of digesting different kinds of food.

So students, we have learned that different animals have different digestive systems suited to their food habits. Now, let's move on to the next important life process — respiration.

## 9.2 Respiration in Animals

We learnt in Grade 6 that all living beings respire. Is the process of respiration the same in all animals? Let us first understand the process of respiration in humans.

### 9.2.1 Respiration in Humans

You know, students, that we breathe in and breathe out air continuously to obtain oxygen and release carbon dioxide. How is this oxygen used in the body? Are breathing and respiration different? Let us find out.

#### How Do We Breathe?

The process of inhaling and exhaling air is called breathing. It is difficult to live without food for a week, without water for a day or two, but without breathing, we usually cannot survive more than a few minutes. Why is that? All of us are alive because we breathe. Not just humans, plants and other animals also breathe. But how do we breathe?

Just as food follows a specific pathway in the digestive system, our body also has a specific system for breathing and respiration. This system is called the respiratory system. The respiratory system consists of various parts as shown in the figure in your textbook. In this system, the exchange of gases follows a specific pathway. The pathway through which the air is inhaled and exhaled involves various parts of the respiratory system assisting in the process of breathing and respiration.

The respiratory system begins with a pair of nasal openings called nostrils through which we inhale and exhale air. The inhaled air passes into a pair of small passages called the nasal passages. Have you noticed tiny hair inside your nostrils? These hair, along with mucus, help trap dust and dirt from the air we breathe in. This is why we should breathe through the nose and not through the mouth. From the nasal passages, the air reaches our lungs through the windpipe. The windpipe forms two branches, which enter the two lungs. In the lungs, these branches further divide into smaller and finer branches that end in small balloon-like sacs called alveoli. Our lungs are protected by the rib cage.

While a lot of the dust is filtered out from the inhaled air, often small infectious particles can get through the lungs. For example, during the COVID-19 pandemic, the SARS-CoV-2 virus affected the respiratory system, leading to breathing difficulties and often causing serious lung problems. This shows how important it is to protect our respiratory system.

Now, students, let's understand the mechanism of breathing by making a simple model. This is Activity 9.2 from your textbook.

In this activity, we take a wide transparent plastic bottle with a lid and remove its bottom. We make a hole in the lid of the bottle. We take a Y-shaped hollow tube, as shown in the figure. We fix two deflated balloons to the forked end of the tube and secure them with rubber bands to make them airtight. We insert the straight end of the tube tightly through the lid from the open base of the bottle and seal the lid with clay to make it airtight. To the open base of the bottle, we attach a thin rubber sheet tightly using a large rubber band.

Now, we pull the rubber sheet from the centre of the base downwards and watch the balloons. What do we observe? Then we release the rubber sheet upwards and observe the balloons. What changes do we see in the balloons? When we pull the rubber sheet downwards, the balloons inflate. Conversely, when we release the rubber sheet upwards, the balloons deflate.

Students, when we breathe in or inhale, our chest expands as the ribs move up and outwards. The diaphragm, which is a dome-shaped muscle below the lungs, moves downwards during inhalation. This increases the space inside the chest, and air enters the lungs. When we breathe out or exhale, the ribs move down and inwards, and the diaphragm moves upwards, reducing space and pushing air out of the lungs.

So what do the balloons in the model represent? What does the rubber sheet represent? In this model, the balloons represent the lungs, and the rubber sheet represents the diaphragm. This is a simple but effective model to understand how we breathe!

Breathing exercises have been practiced across different cultures in India and worldwide for centuries. Pranayama is well known for improving respiratory health, mind relaxation, and concentration. In Ladakh, people practice Tummo breathing, a technique that improves lung function and helps keep the body warm even in cold weather. Similarly, deep breathing techniques are used to promote well-being. Some traditions combine deep breathing with chanting, using rhythmic breath control to enhance relaxation and mental clarity.

#### What Do We Breathe Out?

Now, students, let's perform another interesting activity to understand what we breathe out. This is Activity 9.3 from your textbook.

In this activity, to be demonstrated by the teacher, we take an equal amount of freshly prepared lime water in two test tubes, A and B. In test tube A, we pass the air using a syringe or pichkari. This is the same air that we inhale. In test tube B, we repeatedly blow air through our mouth into the lime water using a straw. Do we observe any changes in the colour of the lime water?

The lime water in test tube B turns milky or cloudy, but the lime water in test tube A does not. What does this indicate? Lime water turns milky when it reacts with carbon dioxide. Therefore, this indicates that the exhaled air contains more carbon dioxide than the air we inhale. This is a very important observation, students!

#### How Does the Exchange of Gases Happen?

Now, students, let's understand how the exchange of gases happens. Through the process of breathing, fresh air from outside enters the lungs via a specific pathway and fills the alveoli. The alveoli have thin walls surrounded by fine tubes containing blood. Blood carries carbon dioxide from the body to the alveoli, where it is released into the air. At the same time, oxygen from the alveoli passes into the blood and is transported to all parts of the body.

Have you ever wondered, students, how the food you eat gives you energy? The key is not only the food but also the oxygen we breathe! When we eat food, our body breaks it down into simple substances like sugar or glucose. Oxygen helps break down glucose to release energy. This process is called respiration. The word equation of the process of respiration is as follows:

Glucose plus Oxygen yields Carbon dioxide plus Water plus Energy.

During breathing, we inhale air from our surroundings and exhale air having more carbon dioxide than the inhaled air. Note that not all the oxygen is used up. Some other animals can use a larger fraction of the oxygen during respiration.

This exchange of gases ensures that each segment of our body gets oxygen to produce energy and remove waste products. In simple words, breathing brings in oxygen and removes carbon dioxide, while respiration uses oxygen to break down food and release energy. This energy helps us walk, run, play, and even think!

Students, it is very important to understand that breathing is a physical process, while respiration is a chemical process that occurs inside the body. Both the processes are essential for our survival!

Now, our body has a unique system for the transport of nutrients, oxygen, and other substances. This system is called the circulatory system. It includes the heart, blood, and blood vessels. The heart pumps blood through blood vessels, ensuring the transport of nutrients, oxygen, and other substances to all parts of the body, while waste products are carried away.

Now, students, I want to tell you something very important about health. Smoking is extremely harmful to health. It damages the lungs and increases the risk of serious diseases, including lung cancer and other respiratory illnesses. It leads to persistent coughing and frequent infections. In addition to harming the smoker, smoking releases toxic chemicals into the air, putting others at risk. When non-smokers inhale this polluted air, they experience passive smoking, which can be especially dangerous for children, pregnant women, and the elderly. Due to these risks, avoiding smoking helps protect both personal health and the well-being of those around us.

### 9.2.2 Do Other Animals Breathe the Same Way as Humans Do?

Now, students, you have learnt that different animals live in different habitats. You may have observed birds flying and fish swimming. How do they breathe? Animals such as birds, elephants, lions, cows, goats, lizards, and snakes breathe through their lungs. Although all these animals have lungs, the structure of their lungs is quite different.

Most aquatic animals like fish have specialised structures known as gills. These are richly supplied with blood vessels. The exchange of oxygen and carbon dioxide between the blood and the gases dissolved in water takes place across the gills.

Amphibians like frogs live both on land and in water. They use different body parts for breathing at various stages of their life. For example, tadpoles breathe through gills, while adult frogs use lungs for breathing on land and skin for gas exchange when they stay in water. This adaptation helps them survive both in water and on land, showing how animals have adapted over time to different environments.

Earthworms use their moist skin for the exchange of oxygen and carbon dioxide. Thus, different animals have different breathing mechanisms to suit their unique habitats.

So students, let me recap what we have learned in this chapter. We learned about life processes such as nutrition, circulation, respiration, excretion, and reproduction, which are essential for the survival of living beings. We studied the human digestive system consisting of an alimentary canal which includes the mouth, oesophagus, stomach, small intestine, large intestine, and anus, and its associated parts, the liver and the pancreas. We learned that digested food is primarily absorbed through the walls of the small intestine, and the nutrients absorbed are distributed through the blood to different parts of the body. The large intestine absorbs most of the remaining water and some salts from the undigested food.

We also learned about grass-eating animals called ruminants, who chew the food partially and swallow it, and later the partially digested food is returned to the mouth for thorough chewing. We studied that breathing involves the movement of air into the lungs or inhalation and out of the lungs or exhalation. The exchange of oxygen and carbon dioxide occurs in the alveoli of the lungs. Respiration uses oxygen from inhaled air to break down glucose into carbon dioxide and water. The process by which nutrients are converted into usable energy is called respiration. The circulatory system transports nutrients and oxygen to all parts of the body, and we learned that breathing is a physical process while respiration is a chemical process. Different animals have different breathing mechanisms adapted to suit their habitats.

Now, students, let's solve the exercises from your textbook. These are very important for your understanding and will help you revise what we have learned.

### Let Us Enhance Our Learning

**Question 1:** Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts — Food → Mouth → ______ → Stomach → ______ → ______ → Anus

Students, let me help you fill this. The food goes from the mouth to the oesophagus or food pipe, then to the stomach, then to the small intestine, then to the large intestine, and finally to the anus. So the complete journey is: Food → Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus.

**Question 2:** Sahil placed some pieces of chapati in test tube A. Neha placed chewed chapati in test tube B, and Santushti took boiled and mashed potato in test tube C. All of them added a few drops of iodine solution to their test tubes A, B, and C respectively. What would be their observations? Give reasons.

Students, let's think about this. Iodine gives a blue-black colour with starch. Chapati contains starch, so in test tube A, the pieces of chapati will turn blue-black because they contain starch. In test tube B, the chewed chapati has been mixed with saliva, which contains an enzyme that breaks down starch into sugar. So the starch has been partially or fully digested, and therefore, the iodine may show no change or only a very light blue-black colour. In test tube C, boiled and mashed potato also contains starch, so it will turn blue-black. The key point here is that chewing with saliva breaks down starch.

**Question 3:** What is the role of the diaphragm in breathing? (i) To filter the air (ii) To help in inhalation and exhalation (iii) To produce sound (iv) To absorb oxygen

Students, the correct answer is (ii) To help in inhalation and exhalation. The diaphragm is a dome-shaped muscle below the lungs. When it moves downwards during inhalation, it increases the space in the chest and air enters the lungs. When it moves upwards during exhalation, it reduces the space and pushes air out of the lungs.

**Question 4:** Match the following:

Let's match each part with its function: (i) Nostrils — (a) fresh air from outside enters (ii) Nasal passages — (d) tiny hair and mucus help to trap dust and dirt from the air we breathe (iii) Windpipe — (e) air reaches our lungs through this part (iv) Alveoli — (b) exchange of gases occurs (v) Ribcage — (c) protects lungs

So the correct matching is: (i) with (a), (ii) with (d), (iii) with (e), (iv) with (b), (v) with (c).

**Question 5:** Anil claims to his friend Sanvi that respiration and breathing are the same process. What question(s) can Sanvi ask him to make him understand that he is not correct?

Students, Sanvi can ask Anil several questions. For example, she can ask: "Is breathing a physical or chemical process?" Breathing is a physical process involving the movement of air in and out of the lungs. She can also ask: "What happens to the glucose in our body during respiration?" During respiration, glucose is broken down to release energy. She can ask: "Does breathing involve the exchange of gases in the cells?" No, breathing is just the intake of air, while respiration occurs in the cells where oxygen is used to break down glucose. These questions will help Anil understand that breathing and respiration are different processes.

**Question 6:** Which of the following statements is correct and why? Anu: We inhale air. Shanu: We inhale oxygen. Tanu: We inhale air rich in oxygen.

Students, let's think about this. The air we inhale is not pure oxygen. It is air that contains about 21% oxygen, along with nitrogen and other gases. So the most accurate statement is Tanu's — we inhale air rich in oxygen. Anu's statement is partially correct because we do inhale air, but it's not specific. Shanu's statement is incorrect because we don't inhale pure oxygen; we inhale air that contains oxygen.

**Question 7:** We often sneeze when we inhale a lot of dust-laden air. What can be possible explanations for this?

Students, when we inhale dust-laden air, the dust particles irritate the nasal passages. The body responds by forcing a sudden, forceful expulsion of air through the nose and mouth to remove the irritants. This is the sneeze reflex. The tiny hairs and mucus in our nostrils trap some dust, but when there is too much dust, the irritant reaches deeper into the nasal passages, triggering the sneeze. This is a protective mechanism of our body to keep our respiratory system clean.

**Question 8:** Paridhi and Anusha of Grade 7 started running for their morning workout. After they completed their running, they counted their breaths per minute. Anusha was breathing faster than Paridhi. Provide at least two possible explanations for why Anusha was breathing faster than Paridhi.

Students, there could be several reasons why Anusha was breathing faster than Paridhi. First, Anusha might have a lower fitness level than Paridhi, so her body needed more oxygen to recover from the exercise, leading to faster breathing. Second, Anusha might have run faster or longer than Paridhi, causing her to need more oxygen. Third, Anusha might have a higher metabolic rate, so her body responds more quickly to the need for oxygen. Fourth, Anusha might have been more anxious or excited during the run, which can also increase breathing rate. These are all possible explanations.

**Question 9:** Yadu conducted an experiment to test his idea. He took two test tubes, A and B, and added a pinch of rice flour to the test tubes, half-filled with water and stirred them properly. To test tube B, he added a few drops of saliva. He left the two test tubes for 35 to 45 minutes. After that, he added iodine solution into both the test tubes. Experimental results are as shown in the figure. What do you think he wants to test?

Students, Yadu wants to test whether saliva helps break down starch. Rice flour contains starch. In test tube A, without saliva, the starch remains, so when iodine is added, it will turn blue-black. In test tube B, with saliva, the starch is broken down into sugars, so when iodine is added, there will be no change or only a slight change in colour. This experiment is similar to the activity we discussed earlier about the action of saliva on starch.

**Question 10:** Rakshita designed an experiment taking two clean test tubes, A and B and filled them with lime water as shown in the figure. In test tube A, the surrounding air that we inhale was passed on by sucking air from the pipe, and in test tube B, the exhaled air was blown through the pipe. What do you think she is trying to investigate? How can she confirm her findings?

Students, Rakshita is trying to investigate the difference between inhaled air and exhaled air. She wants to show that exhaled air contains more carbon dioxide than inhaled air. She can confirm her findings by observing that the lime water in test tube B turns milky or cloudy because of the carbon dioxide in the exhaled air, while the lime water in test tube A remains clear or changes very little. This is exactly what we learned in Activity 9.3.

Now, students, let's look at the exploratory projects. These are interesting activities that will help you learn more about the topics we have covered.

For the first project, you need to find out what are the good practices for maintaining oral hygiene. Try to gather information from books, newspapers, or conversations with elders. Prepare a report. Some good practices include brushing teeth twice a day, cleaning the tongue, rinsing mouth after meals, avoiding too much sugar, and visiting a dentist regularly.

For the second project, find out different ways to maintain a healthy digestive system. Suggest some food items that help maintain good digestive health. Make a report and present it in class. Some food items that help digestion include yogurt, buttermilk, fruits, vegetables, whole grains, and fermented foods.

For the third project, using coloured clay, prepare a 3-D model of the digestive system and label all parts of the digestive system using black paper strips. This will help you understand the digestive system better.

For the fourth project, what is air quality and AQI? Find out the effect of air quality on the respiratory systems of people working in various fields — farmers, factory workers, or street vendors. AQI stands for Air Quality Index, which measures how clean or polluted the air is. Poor air quality can cause respiratory problems like asthma, bronchitis, and other lung diseases.

For the fifth project, try to read about the box-breathing technique. What are its benefits? Box breathing is a breathing technique that involves breathing in, holding, breathing out, and holding again, each for a count of four. It helps reduce stress, improve concentration, and calm the mind.

For the sixth project, both birds and mammals have lungs for breathing, but birds can fly at high altitudes where oxygen levels are low. How might their respiratory system be adapted to help them survive in such conditions? Students, birds have a more efficient respiratory system than mammals. They have air sacs that help in a continuous flow of air through the lungs, allowing for more efficient oxygen exchange. This helps them survive in low-oxygen conditions at high altitudes.

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

## Summary

In this chapter on Life Processes in Animals, we learned about the following important concepts:

First, we learned about nutrition in animals. All animals need to obtain energy from food, and this food contains complex components like carbohydrates, proteins, and fats that need to be broken down into simpler forms. This process is called digestion, and it takes place in the alimentary canal.

In humans, digestion begins in the mouth, where mechanical digestion breaks food into smaller pieces and saliva begins chemical digestion by breaking down starch into sugars. The food then passes through the oesophagus to the stomach, where it is mixed with digestive juices, acid, and mucus. The partially digested food then moves to the small intestine, where bile from the liver, pancreatic juice from the pancreas, and digestive juices from the intestinal walls complete the digestion. The nutrients are absorbed through the finger-like projections in the small intestine. The undigested food goes to the large intestine, which absorbs water and salts, and the waste is egested through the anus.

We also learned that different animals have different digestive systems. Ruminants like cows chew their food partially, swallow it, bring it back to the mouth later for thorough chewing, and then digest it further. Birds have a gizzard to break down food.

Then we learned about respiration. Breathing is the physical process of inhaling and exhaling air, while respiration is the chemical process that uses oxygen to break down glucose and release energy. The respiratory system includes the nostrils, nasal passages, windpipe, lungs, and alveoli. The exchange of oxygen and carbon dioxide occurs in the alveoli. The diaphragm helps in breathing by moving up and down.

Different animals have different breathing mechanisms. Fish breathe through gills, frogs can breathe through their skin and lungs, and earthworms breathe through their moist skin.

We also learned about the circulatory system, which transports nutrients and oxygen to all parts of the body through the heart, blood, and blood vessels.

Finally, we learned about the importance of maintaining good health practices, including oral hygiene, healthy eating, and avoiding harmful habits like smoking.

This concludes our lesson on Chapter 9: Life Processes in Animals. I hope you all have understood these concepts well. Remember, these life processes are essential for the survival of all living beings, including us humans. Thank you for your attention, and I'll see you in the next class!