Kerala Syllabus Class 9 Biology Chapter 3 Respiration and Excretion Notes Solutions

A thorough understanding of Kerala Syllabus 9th Standard Biology Textbook Solutions Chapter 3 Respiration and Excretion Notes Questions and Answers English Medium can improve academic performance.

SCERT Class 9 Biology Chapter 3 Notes Questions and Answers Respiration and Excretion

Std 9 Biology Chapter 3 Notes Pdf Kerala Syllabus English Medium Solutions Questions and Answers

Class 9 Biology Chapter 3 Let Us Assess Answers Respiration and Excretion

Question 1.
Which among the following given below is not the characteristic feature of an efficient gaseous exchange surface?
a) Thick cell wall
b) Proximity to blood capillaries
c) Moist membrane
d) Large surface area
Answer:
a. Thick cell wall

Question 2.
Redraw the diagram and label the parts.

Answer:
a) Trachea
b) Lungs
c) Diaphragm

Question 3.
Write the role of each of the following in the exchange of gases.
a) Plasma
b) RBC
c) Haemoglobin
d) Tissue fluid
Answer:
a) Plasma: The cells need oxygen for metabolism, which creates carbon dioxide as a waste product. The carbon dioxide is absorbed from the cells by the blood plasma (some of it binds to hemoglobin too) and is transported back to the lungs in the bloodstream.

b) RBC: Oxygen molecules attach to red blood cells, which travel back to the heart. At the same time, the carbon dioxide molecules in the alveoli are blown out of the body the next time a person exhales.

c) Haemoglobion: Haemoglobin is a molecule that is responsible for carrying almost all of the oxygen in the blood. It is composed of four subunits, each with a heme group plus a globin chain. A single haemoglobin molecule can carry four O₂ molecules along with the blood.

d) Tissue fluid: It is also called lymph or interstitial fluid helps to bring oxygen and nutrients to cells and to remove waste products from them.

Question 4.
Redraw the diagram, label the parts, and write their functions.

Answer:
a) Kidney: They remove waste products from the blood and produce urine. Kidneys control the levels of many substances in the blood. Kidneys help to control our blood pressure.
b) Ureters: The ureters are the part of the urinary system, The ureters’ role in the process is to carry urine from the kidneys to the bladder. Contractions in the ureter force urine away from the kidneys and into the bladder.
c) Urinary bladder: A hollow organ that stores urine from the kidneys before disposal by urination.
d) Urethra: The urethra acts as a passage to expel urine from the urinary bladder to the outside of the body.

Question 5.
Analyse the figure and answer the questions.

a) Write the names of the circulations X and Y.
b) Write the names of the blood vessels i, ii, iii, iv, y.
c) What is the role of these circulations in the exchange and transport of gases?
d) Explain the role of these circulations in the process of excretion.

a) X- Alveolar exchange of gases (Pulmonary circulation), Y – Systemic exchange of gases (Systemic circulation).

b) (i) Inferior vena cava, (ii) Superior vena cava, (iii) Pulmonary artery, (iv) Pulmonary vein, (v) Aorta

c) Pulmonary circulation moves blood between the heart and the lungs. It transports deoxygenated blood to the lungs to absorb oxygen and release carbon dioxide. The oxygenated blood then flows back to the heart. Systemic circulation moves blood between the heart and the rest of the body.

d) The pulmonary veins by pulmonary circulation return oxygenated blood to the heart, which releases CO₂ from the deoxygenated blood to the lungs for gaseous exchange. The release of CO₂ is a kind of excretion. In systemic circulation, blood with oxygen, nutrients, and hormones travels from the heart to the rest of the body. In the veins, the blood picks up waste products as the body uses up oxygen, nutrients, and hormones.

Extended Activities

Question 1.
Visit a primary health centre and conduct an interview with a doctor on diseases affecting the lungs and kidneys.
Answer:
(Hints: Some question answers regarding this topic are given below for your reference.)

1. Can you explain some common lung diseases and their symptoms?
Answer:
Pulmonary fibrosis and sarcoidosis are examples of lung tissue disease.

2. How can lifestyle choices, such as smoking or pollution exposure, impact lung health?
Answer:
Smoking is one of the biggest contributors to lung-related health problems. It damages the airways and structures of the lungs, leading to chronic conditions like chronic bronchitis and emphysema, as well as various types of lung cancer. Quitting smoking is the best way to improve lung health.

3. Can you discuss the relationship between lung health and kidney function?
Answer:
The function of the lungs is also closely linked to the kidneys, both in health and in disease. In fact, regulation of acid-base balance, control of blood pressure, and fluid homeostasis are closely linked to the interaction of the kidneys and lungs.

Question 2.
Construct models of the respiratory system, kidney, and related parts and display them in the class.
Answer:
Materials:
Respiratory System:

• Cardboard boxes (different sizes for various organs)
• Balloons (represent lungs)
• Straws (represent trachea and bronchi)
• Pipe cleaners (represent smaller airways)
• Tape
• Markers/ paints
  Labels

Kidneys:

• Play dough or modeling clay (in different colors)
• Beans or pebbles (represent nephrons)
• Pipe cleaners or string (represent ureters)
• Cardboard or plastic sheet (to create a base)
• Markers/ paints
• Labels

Hints for Construction:

Research: Before diving in, have students research the basic structure and function of the respiratory system and kidneys. This will guide their model building process.

Divide and Conquer: Break the class into groups, each focusing on either the respiratory system or the kidneys. This allows for focused work and better model representation.

Creative Representation: Emphasize creativity! Cardboard boxes can become lungs, balloons can represent their inflation, and straws can depict the airways. Playdough can be molded into kidney shapes, beans as nephrons, and pipe cleaners as ureters.

Labeling is Key: Labels are crucial for understanding. Encourage students to label the different parts of their models (lungs, trachea, bronchi, nephrons, ureters, etc.) with clear descriptions of their function.

Showcase and Explain: Once the models are built, each group can present their work to the class. This allows students to explain the structure and function of the respiratory system or kidneys using their model as a visual aid.

Connect the Systems: Discuss the connection between these two systems. Explain how the respiratory system provides oxygen needed by the kidneys for proper function, and how the kidneys filter waste products produced by the body during respiration.

Question 3.
Organize an awareness class on organ donation.
Answer:
(Hints: important points to be included in the awareness class are given below)

• The Critical Need for Organ Donation
• Types of Organs and Tissues Donated
• The Organ Donation and Transplantation Process
• Dispelling Myths and Misconceptions
• Legal Aspects of Organ Donation

By including these key points, you can create a comprehensive and informative organ donation awareness class that empowers individuals to make informed decisions and potentially save lives.

Question 4.
Organize and implement programs to make your home and school waste-free.
Answer:
Here are some programs you can implement to reduce waste at home and school:

At Home:
Reduce:

• Plan meals: Reduce impulse buys and food waste by planning meals and creating a grocery list.
• Buy in bulk (with caution): Purchase staples like grains or nuts in bulk to minimize packaging, but ensure you’ll use everything before it expires.
• Choose reusable products: Opt for reusable shopping bags, water bottles, and coffee mugs instead of disposable alternatives.
• Fix instead of toss: Try to repair broken items instead of throwing them away.
• Borrow or rent: Instead of buying something you’ll rarely use, consider borrowing it from a friend or renting it.

Reuse:

• Get creative with containers: Repurpose old jars, containers, and boxes for storage or crafting projects.
• Donate or sell unwanted items: Give pre-loved clothes, toys, or furniture a second life through donations or online marketplaces.
• Compost food scraps: Start a compost bin to turn food scraps into nutrient-rich fertilizer for your plants (check local regulations for composting restrictions).

Recycle:

• Learn your local recycling guidelines: Understand what materials your local program accepts and ensure proper sorting.
• Invest in recycling bins: Have designated bins for recyclables (paper, plastic, glass, etc.) to make sorting easier.
• Recycle electronics responsibly: Don’t throw away old electronics; many electronics stores or specialized facilities accept them for proper recycling.

At School:
Reduce:

• Paperless communication: Encourage online communication (school websites, email) for announcements and assignments whenever possible.
• Double-sided printing: Set printers to default to double-sided printing to reduce paper usage.
• Reusable lunchware: Promote reusable lunch containers and water bottles among students and staff.
• Reusable alternatives: Replace single-use items like paper towels with cloth towels in classrooms and kitchens.

Reuse:

• Refill stations: Install water bottle refill stations to discourage the use of disposable water bottles.
• Donate or sell old textbooks: Organize textbook donation drives or sales to give them a second life.
• Creative project materials: Encourage the use of recycled or repurposed materials for art projects.

Recycle:

• Clearly labeled recycling bins: Place clearly labeled recycling bins throughout the school for easy sorting of paper, plastic, and other recyclables.
• Composting programs: If feasible, explore starting a school composting program for food scraps (check local regulations).
• Educational campaigns: Organize workshops or presentations to educate students and staff about the importance of waste reduction and recycling.

Respiration and Excretion Class 9 Notes Questions and Answers Kerala Syllabus

Question 1.
What is the role of oxygen in respiration and burning?
Answer:
Oxygen is essential for the respiration of living organisms, and it supports combustion because it is essential for burning components. Burning of candles involves the addition of oxygen to carbon hydrogen which forms carbon dioxide, water vapour and energy in the form of heat and light. Respiration utilises oxygen from the atmosphere to break down glucose in food and release carbon dioxide.

Question 2.
What are the products of respiration and burning?
Answer:
Both processes require oxygen for the production of energy. They produce carbon dioxide as a byproduct.

Question 3.
What is the respiratory surface in human beings? How is it arranged in our body?
Answer:
The respiratory surface in humans is the alveoli. They are tiny ballon-shaped sacs found in the lungs which exchange carbon dioxide and oxygen. The human respiratory system is composed of a pair of external nostrils, nasal chamber, pharynx, larynx, and trachea (the windpipe), which is bifurcated when enters into two lungs, bronchi again divides into fine branches called bronchioles inside the lungs and at the ends of the bronchioles we can find some sac-like structures called the alveoli. Alveoli are covered by thin blood capillaries through this exchange of gases takes place.

Question 4.
Complete the by analyse the description and prepare a short note on the respiratory surface in human beings.
Answer:

• Nostrils
• Nasal Cavity
• Trachea
• Bronchi

The respiratory surface is the area or space where the gas exchanges take place, It should have larger surface-to-volume ratio, moist inner surface, and thin wall in contact with blood capillaries Gaseous exchange in the lungs takes place between alveoli and alveolar blood capillaries. The respiration surface in humans is the alveoli.

Question 5.
Don’t you involved in sports and physical exercises? Is there any change in the rate o ventilation (breathing) during such activities? Do the activity given below?

• Form a group of two children each.
• Take rest for 5 minutes. Both of them record the number of inspirations that happen within a minute during this time.
• Record the time using a stop watch.
• In an interval of one minute, record the number of inspirations two more times.
• Then record the number of inspirations of the two children after running for three minutes as mentioned above.
• Continue to record the number of inspirations in every minute till they reach the normal condition.
• Complete the table given below using the recorded results, draw a line graph and compare the rate of ventilation of both the children.

Answer:

Question 6.
Analyse the figure and illustration and complete the table.

Indicators	Inspiration	Expiration
Action of intercostal muscles
Movement of ribs
Change that occurs to the diaphragm
The volume of the thoracic cavity	Increases	Decreases
The pressure of air in the lungs
Movement of air

Answer:

Indicators	Inspiration	Expiration
Action of intercostal muscles	Contracts	Relaxes
Movement of ribs	Rises	Lowers
Change that occurs to the diaphragm	Contracts	Relaxes
The volume of the thoracic cavity	Increases	Decreases
The pressure of air in the lungs	Decreases	Increases
Movement of air	From outside to the lungs	From lungs to the outside

Question 7.
What are the characteristic features of the walls of the alveolus and blood capillaries?
Answer:
The walls of the alveoli are very thin, which makes it easier for oxygen and CO₂ to pass between the alveoli and very small blood vessels (capillaries). Both are made up of a single layer of cells.

Question 8.
What is the importance of moisture in the wall of the alveolus?
Answer:
Moisture is important for gas exchange because, in order for oxygen and carbon dioxide to effectively cross the alveoli membrane, they must dissolve in an aqueous-like solution. With the right amount of moisture, gas exchange occurs properly.

Question 9.
Mention the concentration level of O₂ and CO₂ in the alveolus and in the blood capillaries.
Answer:
During inspiration, the concentration of oxygen inside the alveoli is more than that in blood capillaries whereas the concentration of carbon dioxide in blood capillaries is more than that in alveoli.

Question 10.
How does the exchange of O₂ and CO₂ between the alveolus and the blood capillaries happen?
Answer:
The exchange of gases (oxygen and carbon dioxide) occurs between the alveoli and blood capillaries by simple diffusion.

Indicators	Glycolysis	Krebs cycle
Site of activity
Substances that take part in the chemical process
Products
Requirement of oxygen

Answer:

Indicators	Glycolysis	Krebs cycle
Site of activity	Cytoplasm	Mitochondria
Substances that take part in the chemical process	Glucose converted into pyruvic avid	Pyruvic acid is converted into carbon dioxide and water
Products	Pyruvic acid and 2 ATP molecules	Carbon dioxide, water and 28 ATPs
Requirement of oxygen	Oxygen is not required	Oxygen is required

Question 11.
Complete the chemical process illustrated below by including the missing reactants required for cellular respiration and the products formed.

Answer:

Question 12.
Photosynthesis and respiration are metabolic processes that take place in the living world. Compare these two processes and revise Table replacing glycolysis and Krebs cycle with photosynthesis and respiration respectively.
Answer:

Indicators	Photosynthesis	Respiration
Site of activity	Chloroplast	Mitochondria
Substances that take part in the chemical process	CO2 , Water, Sunlight, Chlorophyll	Glucose
Products	Cilucose, Water, Energy	CO2, Water, Energy
Requirement of oxygen	Oxygen not required	Oxygen is required

Question 13.
What are the conditions that lead to the decrease in the level of haemoglobin? What are the different types of anaemia? Find out.
Answer:
Conditions that lead to the decrease in the level of haemoglobin:

• Blood loss, which can occur because of: Bleeding in your digestive tract, such as from ulcers, cancers, etc.
• Frequent blood donation
• Heavy menstrual bleeding

Different types of anaemia:

• Haemolytic anaemia
• Vitamin deficiency anaemia
• Iron deficiency anaemia
• Sickle cell anaemia, etc.

Question 14.
What are the healthy habits that can be followed to prevent anaemia? Discuss.
Answer:

• Eat foods rich in iron and B vitamins.
• Eat fruits and vegetables high in vitamin C, which helps your body absorb iron.
• Ask your doctor about iron supplements if you don’t get enough iron in your diet.
• Get checked every year or 2 if you’re a woman of childbearing age who has heavy menstrual periods or a previous diagnosis of anaemia.

Question 15.
Analyse illustration and description. Now prepare a short note on respiration in plants.

Answer:
Plants do not have a respiratory system or separate organs for the transport of gases. But they have special features in leaf, stem, and root for the exchange of gases.

The small pores on the surface of leaves and young stems are called stomata. Stomata remain open in the daytime and close at night. During the day photosynthesis and respiration take place simultaneously in the mesophyll cells of leaves. Since the rate of photosynthesis is high during the day, oxygen formed is used for respiration and the excess oxygen is expelled. CO₂ formed as a result of respiration is utilized for photosynthesis and insufficient CO₂ is received from the atmosphere. At night when stomata close, respiratory gas exchange occurs through diffusion.

Lenticels are the lens-shaped openings found on the surface of mature stems and roots. They also help in gaseous exchange in plants. Plant roots have special cells that perform gaseous exchange with the air that is present in the soil particles.

Question 16.
Does anaerobic respiration take place in human beings? Find out.
Answer:
Yes. In humans, aerobic respiration takes place in all cells as part of energy production in mitochondria. But in certain conditions, our cells lack oxygen to produce enough energy. For example, when we are doing strenuous exercises or something like that, our muscle cells lack oxygen. In such situations, muscle cells respire without oxygen which results in the production of lactic acid in cells.

Question 17.
Mention the differences in the cellular respiratory processes in bacteria and yeast.
Answer:
Both bacteria and yeast respire anaerobically within the cytoplasm of the cell. In both cases, the respiratory substances are the same, ie, glucose. But the end products are different. In lactobacillus, glucose is anaerobically broken down with the production of 2 molecules of ATP.

This breaking produces lactic acid through an intermediate production of pyruvic acid. In the case of yeast cells, alcohol and CO₂ are the end products of anaerobic respiration. Here also glucose is first converted into pyruvic acid with the production of two ATP molecules and then to alcohol and CO₂.

Question 18.
Some situations in daily life are given below. Discuss how anaerobic respiration is beneficial in such situations and prepare short notes on the same.
a) Yeast is added to leaven the dough.
b) Curd is added to milk to prepare curd.
Answer:
a) Yeast is added to leaven the dough:
Yeasts ferment the sugar and produce carbon dioxide in the process. Fermentation is otherwise called anaerobic respiration. Carbon dioxide results in the leavening or rising of the dough to three times its original size.

b) Curd is added to milk to prepare curd:
A teaspoon of curd is added to milk contains the bacteria Lactobacillus. As the bacteria gets more lactose, it will produce lactic acid in the milk converting the entire milk into curd.

Question 19.
Which are the major excretory substances in our body?
Answer:
The main excretory product generated by the human body is urea. The urea is excreted out of the body via urine. Sweat is another excretory substance from skin.

Question 20.
If CO₂ is not eliminated on time, how does it adversely affect the body? Find out.
Answer:
CO₂ transported through our body in three different ways, such as bicarbonate ions, as Carbonic acid when combine with water, then as CO₂ as such. Whern excess CO₂ accumulated in the body it will combines with water molecules which are abaundant in our body results in the formation of excess amount of carbonic acid. Presence of carbonic acid increases the acid content in our body.

Question 21.
How does the formation of ammonia happens?
Answer:
Amino acids are formed by the breakdown of proteins in the cells. As a result of the metabolic activities of amino acids, several nitrogenous by-products are formed. The most harmful among these is ammonia.

Question 22.
Name the organ where urea is synthesised?
Answer:
Liver

Question 23.
How does Urea synthesis happens?
Answer:
The ammonia formed in tissues diffuses into blood through tissue fluids and blood transports it to the liver. In liver with the help of certain enzymes, ammonia combines with carbon dioxide and water to form urea.

Question 24.
Explain the elimination of urea.
Answer:
Kidneys play a major role in the excretion of urine which contains waste materials including urea. Urea is made when foods containing protein (such as meat, poultry, and certain vegetables) are broken down in the body. Urea is carried in the blood to the kidneys. This is where it is removed, along with water and other wastes in the form of urine

Question 25.
Which are the excretory organs in our body?
Answer:

• Kidney – Excretes water and salts through urine.
• Liver – Synthesises urea
• Skin – Secretes sweat
• Lungs – Eliminates Carbon dioxide

Question 26.
Analyze illustrations based on the hints and find out how the structure of kidneys and nephrons are suitable to remove waste materials and complete the given table.

Hints	Parts
Blood vessel which carries blood to the kidneys
Blood vessel which carries blood away from the kidneys
Ultra filters present in the kidneys
The double walled cup-shaped structure present at one end of the nephron
Network of minute capillaries present in the Bowman’s capsule
Blood vessel which carries bkxxl to the capillary network
Blood vessel which carries blood away from the capillary- network
The long tubule which connects the Bowman’s capsule and the collecting duct
The part where renal tubules enter, collects urine and carries it to the pelvis.
The initial part of ureter
Part that carry urine to urinary bladder.

Answer:

Hints	Parts
Blood vessel which carries blood to the kidneys	Renal artery
Blood vessel which carries blood away from the kidneys	Renal vein
Ultra filters present in the kidneys	Nephron
The double-walled cup-shaped structure present at one end of the nephron	Bowman’s capsule
A network of minute capillaries present in the Bowman’s capsule	Glomerulus
Blood vessel which carries blood to the capillary network	Afferent vessel
Blood vessel which carries blood away from the capillary network	Efferent vessel
The long tubule that connects the Bowman’s capsule and the collecting duct	Renal tubules
The part where renal tubules enter, collects urine and carries it to the pelvis.	Collecting duct
The initial part of the ureter	Pelvis
The part that carry urine to the urinary’ bladder	Ureters

Question 27.
Analyze the illustration and complete the given worksheet using the hints.


Answer:

Question 28.
Why all components in the glomerular filtrate are not present in urine? Find out the components that are reabsorbed and the components that are secreted.
Answer:
Because some of the components in the glomerular filtrate are reabsorbed into the blood and some are secreted into the renal tubules. so that all compoments in the glomerular fillrate are not present in urine.
Components that are reabsorbed: Glucose, amino acids, NaCl , and other essential salts
Components which are secreted: Hydrogen ions, potassium ions, etc

Question 29.
Is diagnosis of diseases possible through urine tests?
Answer:
Yes. Urine as a Sample to Diagnose Sexually Transmitted Diseases. Urine is extremely useful to diagnose infections of the reproductive tract.

Question 30.
Kidney stone, nephritis, uraemia etc. are some diseases affecting the kidneys. Prepare a presentation including the causes, symptoms, etc of these diseases and present it in the class.
Answer:

Diseases	Causes	Symptoms
Kidney stone	Not drinking enough water	Severe pain in your back or side, Blood in urine, A burning feeling when urinating.
Nephritis	Diabetes, genetic disorder link that affects the kidneys.	Decreased urine output, High blood pressure, urine appears dark, tea-coloured, or cloudy
Uraemia	Diabetes, High blood pressure	Nausea, Vomiting, Loss of appetite

Question 31.
Analyze the illustration and prepare a short note on how hemodialysis is done.

Answer:
Hemodialysis is a process of filtering the blood of a person whose kidneys are not working normally. Hemodialysis helps control blood pressure and balance important minerals, such as potassium, sodium, and calcium, in your blood. In this process, blood with a high quantity of waste materials is passed to the dialysis unit after adding heparin to prevent coagulation.

When blood flows through the dialysis unit the waste materials in the blood diffuse into the dialysis fluid. This fluid is removed in due course. Antiheparin is added to the purified blood and is returned to the body.

Question 32.
Why is the dialysis fluid removed from the dialysis unit in due course of time?
Answer:
If the dialysis fluid is not removed properly, it can cause swelling and increase your blood pressure, which makes your heart work harder. Too much fluid can build up in the lungs, making breathing difficult. Hemodialysis removes fluid as the blood is filtered through the dialysis machine.

Question 33.
When is kidney transplantation required?
Answer:
Kidney transplantation is done when a person whose kidneys no longer function properly.

Question 34.
Complete the given table by collecting information about the main excretory products and excretory organs of the organisms.

Organism	Main excretory product	Main excretory organ/mechanism
Amoeba	Ammonia	Contractile vacuole
Earthworm
Insects
Frog
Reptiles
Birds

Answer:

• The kidney is the main excretory organ in human beings, but it is different in various organisms.
• Plants do not have special excretory systems like animals.
• The Hydathodes are also known as the water stomata

The excretory material is different in each organism depending on its life processes. The kidney is the main excretory organ in human beings, but it is different in various organisms.

Organism	Main excretory product	Main excretory organ/Mechanism
Amoeba Earthworm Insects Fishes Frogs Reptiles Birds	Ammonia Urea Uric acid Ammonia Urea Uric acid Uric acid	Contractile vacuole Nephridia Malpighian tubules Kidney Kidney Kidney Kidney

Question 35.
Analyze illustration and prepare a short note on excretion in plants.

Answer:
Animals have extensive systems for excretion. But plants do not have special excretory systems like animals. The different plant structures that eliminate different forms of waste are leaves, stems, ageing tissues, xylem, roots, bark, fruits, and flowers.

The process of excretion in plants occurs in the following ways: Through the stomata of leaves and lenticels of stems, oxygen, carbon dioxide, and water vapour are expelled as gaseous wastes. Some waste materials are gathered in tree bark and leaves. The wastes are removed when the leaves and bark are shed.The Hydathodes are also known as the water stomata; they are found at the tips of the veins of the leaves and help in the removal of water and salts from plants.

Question 36.
Analyze illustration and prepare a short note on how the excretory organs help in maintaining homeostasis.

Answer:
The excretory organs includes of the kidneys, liver, skin, large intestine, and the lungs. The excretory system maintains homeostasis through the elimination of excess water and wastes from the body.
Refer to topic 9 for more information.

Maintenance of homeostasis is the sign of life. The excretory system maintains homeostasis through the elimination of excess water and wastes from the body. The excretory structures consists of the kidneys, liver, skin, large intestine, and the lungs.

Kidneys:

• Regulate Salt and water balance.
• Regulation of blood pressure.
• Regulation of pH
• Expels waste

Liver:

• Regulates metabolism.
• Neutralises toxins.

Skin:

• Regulation of temperature, salt, and water.

Lungs:

• Elimination of CO₂
• Regulation of O₂ level.
• Regulation of pH

Any change in the internal environment disrupts homeostasis. The major factors that may cause a change in the internal environment are:

• Improper lifestyles
• Wrong food habits
• Over-nutrition and under-nutrition,
• Lack of exercise
• Mental stress
• Alcoholism
• Smoking and the use of addictive drugs
• Pollution
• Lack of hygiene
• The abundance of pathogens
• Improper use of medicines, and contact with toxic substances.

The external environment is also as important as the internal environment. The External environment should be kept waste-free for the well-being of living organisms. Every individual should develop the right attitude towards this. Prepare a master plan for making the school and its surroundings waste-free on behalf of the health club and implement it as part of the school master plan.