chapter 3 biology class 6

Case Study: Health and Lifestyle

1. What are the lifestyle habits of Sarah that may contribute to her poor cardiovascular health?
Sarah’s unhealthy lifestyle habits include:

·       Sedentary behavior: She spends most of her time on screen-based activities with little physical movement.

·       Poor diet: Her diet is heavy in processed snacks, fast food, and sugary beverages, lacking fruits, vegetables, and whole grains.

·       Lack of exercise: She does not engage in regular physical activity.

·       Weight gain: She has gained excess weight recently, which is a risk factor for cardiovascular issues.

·       High cholesterol: Her diet and inactivity likely contribute to elevated cholesterol levels.

2. How can regular physical activity benefit Sarah's cardiovascular fitness?
Regular physical activity can:

·       Strengthen the heart muscle, making it pump blood more efficiently.

·       Lower blood pressure and cholesterol levels, reducing the risk of heart disease.

·       Improve circulation and oxygen delivery to tissues.

·       Help manage weight and reduce excess body fat.

·       Boost energy levels and reduce fatigue.

3. What dietary changes are recommended for Sarah to improve her heart health?
Sarah should:

·       Increase intake of fruits and vegetables for vitamins, minerals, and fiber.

·       Choose whole grains (like brown rice, whole wheat bread) over refined grains.

·       Limit processed foods, fast food, and sugary drinks to reduce unhealthy fats and added sugars.

·       Incorporate lean proteins (chicken, fish, beans) and healthy fats (nuts, seeds, olive oil).

·       Reduce salt intake to help control blood pressure.

·       Stay hydrated with water instead of sugary beverages.

Dig in Deep: Healthy Lifestyle

1. What are the components of leading a healthy lifestyle?
A healthy lifestyle includes:

·       Regular physical activity (exercise, sports, walking).

·       Balanced nutrition (variety of foods, adequate fruits and vegetables, limited processed foods).

·       Good hygiene practices (handwashing, oral care).

·       Adequate sleep (7–9 hours per night for teens).

·       Stress management (relaxation, hobbies, meditation).

·       Avoiding harmful substances (tobacco, alcohol, drugs).

·       Regular health check-ups.

2. How does hygiene contribute to a healthy lifestyle?
Good hygiene prevents the spread of infections and diseases, maintains healthy skin and teeth, and supports overall well-being. Practices like regular handwashing reduce exposure to germs, while oral hygiene prevents dental problems and contributes to systemic health.

3. How does regular physical activity keep us fit?
Regular activity:

·       Strengthens muscles, bones, and the cardiovascular system.

·       Improves metabolism, aiding weight management.

·       Boosts mental health by reducing stress and anxiety.

·       Enhances flexibility, balance, and coordination.

·       Increases endurance and energy levels.

4. What are the negative effects of over-consumption of sugar?
Excess sugar intake can lead to:

·       Weight gain and obesity, increasing risk of diabetes and heart disease.

·       Tooth decay and cavities.

·       Increased risk of chronic diseases (type 2 diabetes, heart disease).

·       Energy crashes and poor concentration.

·       Poor nutrition, as sugary foods often replace healthier options.

The Digestive System

Types and Arrangement of Teeth

·       Incisors: 4 in each jaw (total 8). Flat, sharp edges for biting and cutting.

·       Canines: 2 in each jaw (total 4). Pointed for tearing.

·       Premolars: 4 in each jaw (total 8). For crushing and grinding.

·       Molars: 6 in each jaw (total 12, including wisdom teeth). For chewing and grinding.

Permanent teeth: 32 in total (16 per jaw): 8 incisors, 4 canines, 8 premolars, 12 molars.

Care of Teeth

·       Brush twice daily (morning and night).

·       Floss daily to remove plaque between teeth.

·       Limit sugary foods/drinks and rinse mouth if consumed.

·       Eat a balanced diet with plenty of calcium.

·       Drink water to rinse the mouth.

·       Regular dental check-ups.

Recall and Unwind (True/False)

1.    False. There are two canines in each jaw, not four.

2.  False. The alimentary canal is also called the food canal, not wind canal.

3.  True. The tongue helps in swallowing food.

4.  True. Teeth are fixed to the gums.

5.   False. All teeth do not have the same shape and size.

Digestive System: Organs and Functions

Organ	Function
Mouth	Ingestion, chewing, mixing with saliva, initial starch digestion
Oesophagus	Transports food to stomach via peristalsis
Stomach	Churns food, secretes gastric juice (HCl, pepsin), partial protein digestion
Small Intestine	Completes digestion, absorbs nutrients via villi
Large Intestine	Absorbs water, forms feces
Rectum & Anus	Stores and expels feces
Liver	Produces bile (emulsifies fats), stores glycogen, detoxifies
Pancreas	Secretes pancreatic juice (enzymes for carbs, proteins, fats)
Salivary Glands	Secrete saliva (moistens, digests starch)

 

Fact Check (Correct/Incorrect)

1.    Incorrect. The oesophagus is a muscular tube, not a bag-like organ (that’s the stomach).

2.  Incorrect. Stomach secretes hydrochloric acid, not sulphuric acid.

3.  Correct. Digestion and absorption mainly occur in the small intestine.

4.  Incorrect. The liver is the largest gland, not the smallest.

5.   Correct. Sucrase converts sucrose to glucose and fructose.

Enzymes in Digestion

Organ	Enzyme	Substrate	Product(s)
Mouth	Salivary amylase	Starch	Maltose
Stomach	Pepsin	Proteins	Proteoses, peptones
Small Intestine	Trypsin	Proteins	Polypeptides
Small Intestine	Amylase	Starch	Maltose
Small Intestine	Lipase	Fats	Fatty acids, glycerol
Small Intestine	Erepsin	Peptones/peptides	Amino acids
Small Intestine	Maltase	Maltose	Glucose
Small Intestine	Sucrase	Sucrose	Glucose + fructose
Small Intestine	Lactase	Lactose	Glucose + galactose

 

Maintaining Digestive Health

·       Eat a balanced diet (variety, fiber, lean proteins, healthy fats).

·       Stay hydrated (drink plenty of water).

·       Chew food thoroughly.

·       Practice portion control and regular meal timings.

·       Limit processed foods, sugar, unhealthy fats, and alcohol.

·       Exercise regularly and manage stress.

·       Maintain good hygiene (handwashing, clean utensils).

·       Get enough sleep and avoid smoking.

The Respiratory System

Organs: Nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, lungs, diaphragm.

Functions:

·       Nose/Nasal Cavity: Filters, warms, and moistens air; traps dust and germs.

·       Pharynx: Passage for air and food.

·       Larynx: Voice production.

·       Trachea: Conducts air to bronchi.

·       Bronchi/Bronchioles: Conduct air deeper into lungs.

·       Alveoli: Site of gas exchange (oxygen in, carbon dioxide out).

·       Lungs: Main organs of respiration; expand and contract with breathing.

·       Diaphragm: Muscle that aids breathing by moving up and down.

Mechanism of Breathing

·       Inhalation: Diaphragm contracts (moves down), ribs move out; chest cavity expands, air rushes in.

·       Exhalation: Diaphragm relaxes (moves up), ribs move in; chest cavity decreases, air is pushed out.

Differences Between Inhalation and Exhalation

Inhalation	Exhalation
Ribs move up and out	Ribs move down and in
Diaphragm contracts (moves down)	Diaphragm relaxes (moves up)
Chest cavity increases	Chest cavity decreases
Air pressure in lungs decreases	Air pressure in lungs increases
Air rich in oxygen enters lungs	Air rich in CO₂ leaves lungs

 

Gaseous Transport & Cellular Respiration

·       Gaseous Transport: Oxygen binds to hemoglobin in RBCs, forming oxyhemoglobin; CO₂ is carried as carbaminohaemoglobin.

·       Cellular Respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP).

Respiratory Diseases

Disease	Cause	Symptoms	Treatment
Asthma	Inflammation, narrowing of airways	Wheezing, shortness of breath	Bronchodilators, anti-inflammatory meds
Bronchitis	Infection (viral/bacterial), irritants	Cough, mucus, chest tightness	Rest, fluids, cough meds, sometimes antibiotics
Pneumonia	Infection (bacteria, virus, fungi)	Cough, fever, chest pain	Antibiotics/antivirals, supportive care
Tuberculosis	Bacteria (Mycobacterium tuberculosis)	Persistent cough, weight loss	Long-term antibiotics, BCG vaccine

 

Recall and Unwind (Fill in the Blanks)

1.    The sticky fluid present in the nasal cavity is called mucus.

2.  The windpipe is also called trachea.

3.  Bronchioles end into microscopic air sacs called alveoli.

4.  Breathing is a physical process.

5.   During respiration, energy is stored in the form of ATP.

The Circulatory System

Components: Heart, blood vessels (arteries, veins, capillaries), blood.

Heart Structure:

·       Four chambers: Right atrium, right ventricle, left atrium, left ventricle.

·       Valves: Prevent backflow (tricuspid, bicuspid, pulmonary, aortic).

·       Septum: Separates left and right sides, preventing mixing of oxygenated and deoxygenated blood.

Blood Vessels

Type	Direction	Wall Thickness	Valves	Blood Type Carried	Example
Artery	Away from heart	Thick, elastic	Absent	Oxygenated (except pulmonary)	Aorta
Vein	Toward heart	Thin	Present	Deoxygenated (except pulmonary)	Vena cava
Capillary	Between artery & vein	Very thin	Absent	Both	Capillary beds

 

Blood Components

·       Plasma: Liquid part, carries nutrients, hormones, wastes.

·       Red Blood Cells (RBCs): Carry oxygen (hemoglobin), no nucleus.

·       White Blood Cells (WBCs): Fight infection, have nucleus.

·       Platelets: Help in clotting, no nucleus.

Blood Groups

Group	Antigen	Antibody	Can Donate To	Can Receive From
A	A	B	A, AB	A, O
B	B	A	B, AB	B, O
AB	A, B	None	AB	All
O	None	A, B	All	O

 

Circulation of Blood

·       Pulmonary circulation: Heart → Lungs → Heart (oxygenation).

·       Systemic circulation: Heart → Body → Heart (delivers oxygen, collects CO₂).

·       Double circulation: Blood passes through the heart twice in one complete circuit.

Blood Pressure, Heartbeat, and Pulse

·       Blood pressure: Force of blood on vessel walls; measured with sphygmomanometer.

·       Heartbeat: Lub (atria contract), dub (ventricles contract); normal rate ~72/min.

·       Pulse: Throbbing in arteries; can be felt at wrist, neck.

Keeping the Heart Healthy

·       Balanced diet (fruits, veggies, whole grains, lean proteins, healthy fats).

·       Limit saturated/trans fats, salt, and sugar.

·       Portion control and regular hydration.

·       Regular exercise (walking, swimming, cycling).

·       Avoid smoking and limit alcohol.

·       Manage stress and ensure adequate sleep.

Apply Your Knowledge

A. Fill in the blanks.

1.    Pepsin acts on proteins to form proteoses and peptones.

2.  Lipase acts on fats to form fatty acids and glycerol.

3.  The upper chamber of the heart is called atrium and the lower chamber is called ventricle.

4.  Blood is composed of plasma, RBCs, WBCs and platelets.

5.   The BCG vaccine can be taken to prevent tuberculosis.

B. State whether the given statements are true (T) or false (F). Correct the false statements by changing only one word.

1.    False. Digestion is completed in the small intestine.

2.  False. Bile juice is secreted by the liver.

3.  True.

4.  True.

5.   True.

C. Choose the correct answer.

1.    Maltose

2.  Canines

3.  Left auricle

4.  Alveolus

5.   Pulmonary artery

D. Match the columns.

1.    Universal donor – (e) Blood group O

2.  Systole – (c) Contraction phase of the heart

3.  Pepsin – (b) Present in gastric juice

4.  Mucus – (a) Sticky fluid which lines the nasal cavity

5.   Cellular respiration – (d) Chemical process

E. Circle the odd one out and give reason for your choice.

1.    Mouth (others are processes; mouth is an organ)

2.  Lung (others are digestive organs; lung is respiratory)

3.  Mindful eating (others are negative; mindful eating is positive)

4.  Indigestion (others are respiratory diseases; indigestion is digestive)

F. Answer in one word.

1.    Liver

2.  Villi

3.  Haemoglobin

4.  Breathing

5.   Platelets

G. Define the following terms.

1.    Oesophagus: A muscular tube that carries food from the mouth to the stomach.

2.  Digestion: The process of breaking down complex food into simpler substances that can be absorbed by the body.

3.  Arteries: Blood vessels that carry blood away from the heart to the body.

4.  Heartbeat: The rhythmic contraction and relaxation of the heart.

5.   Egestion: The removal of undigested food from the body through the anus.

H. Answer the following questions in brief.

1.    Nasal cavity lined with hairs to trap dust and germs, preventing them from entering the lungs.

2.  Air pollution causes respiratory illness by introducing harmful particles and chemicals that irritate and damage the respiratory tract.

3.  RBCs are red due to the presence of hemoglobin, which binds oxygen.

4.  Veins enter the heart (superior/inferior vena cava, pulmonary veins); arteries leave the heart (aorta, pulmonary artery). Veins bring blood to the heart; arteries carry blood away.

5.   Saliva moistens food, begins starch digestion, and cleans the mouth.

I. Answer the following questions in detail.
(Diagrams should be drawn as per textbook illustrations.)

·       Types of teeth: Incisors (cutting), canines (tearing), premolars & molars (grinding).

·       Blood cells: RBCs (carry oxygen), WBCs (fight infection), platelets (clotting).

·       Tongue: Shows taste buds for sweet, salty, sour, bitter.

·       Blood vessels: Artery (thick, away from heart), vein (thin, to heart), capillary (very thin, exchange site).

Functions of digestive organs: (See table above.)
Undigested food in large intestine: Water is absorbed; remaining material is stored as feces and egested.
Circulation of blood: (See double circulation explanation above.)
Respiratory diseases: (See table above for causes and treatments.)

5. What role does diet play in controlling heart diseases?
A healthy diet (low in saturated/trans fats, salt, and sugar; high in fruits, vegetables, whole grains, and healthy fats) helps control cholesterol, blood pressure, and weight, reducing heart disease risk.

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1. Build Your Skills

Complete the Flow Chart (Enzymes of Digestion)

Mouth:

• Enzyme: Salivary amylase (ptyalin)

• Substrate: Starch

• Product: Maltose

Stomach:

• Enzyme: Pepsin

• Substrate: Proteins

• Product: Peptones/Proteoses

Duodenum:
(Enzymes from liver and pancreas act here)

• Bile (from Liver):

  • Function: Emulsifies fats (no enzyme)

  • Substrate: Large fat globules

  • Product: Small fat globules

• Pancreatic amylase:

  • Substrate: Starch

  • Product: Maltose

• Trypsin:

  • Substrate: Proteins/peptones

  • Product: Peptides

• Lipase:

  • Substrate: Fats

  • Product: Fatty acids and glycerol

Ileum (Small Intestine):
(Contains intestinal juices: succus entericus)

• Maltase:

  • Substrate: Maltose

  • Product: Glucose

• Sucrase:

  • Substrate: Sucrose

  • Product: Glucose and fructose

• Lactase:

  • Substrate: Lactose

  • Product: Glucose and galactose

• Peptidase (Erepsin):

  • Substrate: Peptides

  • Product: Amino acids

Picture Study (Digestive System - Fill in the Blanks)

Refer to the image to identify the organs:

A – Salivary gland
B – Stomach
C – Liver
D – Gall bladder
E – Pancreas
F – Small intestine

1. ‘A’ secretes a watery substance called saliva.

2. The inner wall of ‘B’ secretes gastric juices which contain hydrochloric acid and pepsin.

3. The juice secreted by ‘C’ helps in the digestion of fats.

4. The organ ‘D’ temporarily stores bile secreted by ‘C’.

5. The pancreatic juice secreted by ‘E’ acts on proteins, starch, and fats and converts them into simpler substances.

6. Absorption of digested food takes place in the organ ‘F’.

2. Make It Error-Free (Heart Passage)

Original Error-Filled Passage:
The human heart is part of the respiratory system. The heart is a bony organ located in the chest cavity. It is slightly tilted to the right. There are three chambers in the human heart. The two lower chambers are called atria and the two upper chambers are called ventricles. There are valves between the auricle and ventricle on each side. The valves allow blood to flow in both direction. The heart acts as a pump which brings about the collection of blood throughout the body.

Incorrect	Correct
respiratory system	circulatory system
bony	muscular
three	four
atria/ventricles	atria = upper,
	ventricles = lower
both direction	one direction
collection	circulation

Corrections explained:

• Heart is part of the circulatory, not respiratory, system.

• It is a muscular organ, not bony.

• Has four chambers (2 atria, 2 ventricles), not three.

• The upper chambers: atria; lower: ventricles.

• Valves allow blood flow in one direction, not both.

• It circulates (not collects) blood.

Label and Answer (Respiratory System Image)

1. Which organ system is shown in the image?
Respiratory system.

2. How are dust particles prevented from entering organ 1 (Nose)?
The nose has hair and mucus that trap dust, germs, and other particles.

3. What is the opening of organ 2 (trachea) called?
Glottis (or ‘windpipe’ for more general answer).

4. The organ 2 gets divided into two branches between the two lungs. What is 3 called then?
Bronchi (each branch is a bronchus; plural is bronchi).

5. What is the function of the two-layered membrane on organ 4 (lungs)?
Pleural membrane reduces friction and protects the lungs during breathing.

6. What happens to organ 5 (diaphragm) during inhalation and exhalation?

• Inhalation: Diaphragm contracts and moves downward, increasing chest volume.

• Exhalation: Diaphragm relaxes and moves upward, reducing chest volume.

3. Activities and Projects

1. Digestive System Model

• Make and label all organs: Mouth, salivary glands, esophagus, stomach, liver, gall bladder, pancreas, small and large intestine, rectum, anus.

• Each part’s function:

  • Mouth: Chewing, mixing with saliva.

  • Esophagus: Peristaltic movement.

  • Stomach: Acid and enzyme breakdown.

  • Liver: Makes bile; Gall bladder: stores it.

  • Pancreas: Makes digestive enzymes.

  • Small intestine: Complete digestion, nutrient absorption.

  • Large intestine: Water absorption.

  • Rectum/Anus: Store and remove waste.

2. Food Habits Survey

• Design a table: positive (+) or negative (–) habits.

  • Washing hands: healthy

  • Junk food, sugary food, fat-rich: unhealthy

  • Regular exercise, enough water, timely meals: healthy

• Suggest improvements: Replace junk with fruits, drink more water, exercise regularly, eat less processed/fatty foods.

3. Working Stethoscope & Heartbeat Activity

• Follow the steps to make the stethoscope.

• Measure heartbeat at rest and after running; record in table.

• Average heartbeat: Count all readings, divide by number of students.

4. Observation/Research-Based Questions

Respiratory System Working Model

• Use Internet to learn about the respiratory system.

• Make a model with labelled parts: nasal passage, trachea, bronchi, lungs, diaphragm.

• Demonstrate breathing process: Air in (diaphragm down, chest expands), air out (diaphragm up, chest contracts).

Computer Corner: Dorothy Hodgkin

• Dorothy Hodgkin: Nobel laureate, determined structures of important biochemical substances (like penicillin, vitamin B12) using X-ray crystallography.

5. Life Skills

1. How is asthma caused?
Asthma is caused by inflammation and narrowing of the airways, often triggered by allergens, pollution, exercise, or respiratory infections.

2. Write two measures to prevent asthma.

• Avoid exposure to known allergens (e.g., dust, pollen, smoke).

• Take prescribed medication and monitor breathing regularly.

3. What is blood pressure?
Blood pressure is the force exerted by circulating blood on the walls of the arteries.

4. Name the instrument to measure blood pressure.
Sphygmomanometer.

6. HOTS Corner

1. Why do people experience muscle cramps after heavy exercise?
Due to accumulation of lactic acid when muscles carry out anaerobic respiration from lack of oxygen.

2. Why should we breathe through the nose, not mouth?
The nose warms, moistens, and filters the air, trapping dust and germs, protecting lungs.

3. How are valves between auricle and ventricle helpful?
They prevent backflow of blood, ensuring it moves in the correct direction through the heart.

4. Does mixing of oxygenated and deoxygenated blood happen in humans?
No; heart has a septum separating left (oxygenated) and right (deoxygenated) sides, maintaining efficient circulation.

5. Why does the doctor advise not to eat fatty foods?
Fatty foods can raise cholesterol, clog arteries, and increase heart disease risk.

6. Why are arteries thick, muscular, and elastic?
They withstand high pressure as blood is pumped from the heart and need elasticity to stretch and accommodate pulsatile blood flow.

7. Why does the heart send blood to the lungs during circulation?
To oxygenate it; lungs remove CO₂ and add O₂ for delivery to the body.

8. Can a person with AB blood group donate to O? Why/why not?
No; AB blood has both A and B antigens, which would react with antibodies in O blood (which has neither antigen but both antibodies), causing a transfusion reaction.

case study

1. What is the percentage of death due to heart ailments in rural areas?

   The percentage of deaths due to heart ailments in rural areas is 22.9%. This information is directly highlighted in the infographic, where it mentions "22.9% deaths occur because of ailments in rural areas."

2. Are women at higher risk of heart disease than men? If yes, then what are the possible reasons?

   The provided text and infographic do not supply a direct comparison between women and men regarding the risk of heart disease. Generally, epidemiological studies indicate that men are at a higher risk at younger ages, but women's risk increases significantly post-menopause due to hormonal changes, especially the drop in estrogen which is believed to have a protective effect on the heart. Additional risk factors for women can include:

   • Lifestyle changes post-menopause

   • Higher rates of undiagnosed hypertension or diabetes

   • Lack of regular physical activity

   • Delayed diagnosis due to less "classic" symptoms compared to men

   Note: These reasons are based on established medical knowledge, not directly from the provided image.

3. Why do you think people are getting heart diseases at a young age?

   The infographic states "900 people under 30 die due to heart disease in India every day," showing a significant burden among young people. The likely reasons include:

   • Lifestyle factors: Increased consumption of processed foods high in unhealthy fats, salt, and sugar.

   • Sedentary lifestyle: Less physical activity amongst youth due to digital entertainment and academic or work pressures.

   • High stress: Rising mental health issues and stress levels.

   • Smoking and substance abuse: Early initiation increases lifetime risk.

   • Genetic predisposition: South Asians have a higher risk of heart diseases at a younger age.

   These explanations are based on well-established trends in public health research.

4. How can heart diseases be prevented?

   Heart diseases can be effectively prevented by adopting the following measures:

   • Regular physical activity: At least 30–60 minutes of moderate exercise most days of the week.

   • Healthy diet: Emphasize fruits, vegetables, whole grains, lean protein, and healthy fats while avoiding trans fats, excess salt, and sugars.

   • Avoid tobacco and excessive alcohol: Both are major independent risk factors.

   • Stress management: Engaging in relaxation techniques, hobbies, and social support.

   • Regular health check-ups: Early detection and control of blood pressure, blood sugar, and cholesterol.

   • Adequate sleep: Poor sleep increases cardiovascular risk.

5. What role does diet play in controlling heart diseases?

   Diet has a significant role in controlling and preventing heart diseases:

   • A diet low in saturated and trans fats, salt, and sugar helps lower cholesterol levels, blood pressure, and prevents obesity.

   • High intake of fiber (from whole grains, fruits, and vegetables) can help reduce blood cholesterol and improve heart health.

   • Omega-3 fatty acids (from fish, flaxseeds, walnuts) are known to reduce inflammation and lower cardiovascular risk.

   • Avoidance of processed and fast foods reduces intake of unhealthy fats and empty calories.

   • Moderation: Eating the right portion sizes and balancing calories also helps in weight management, which is crucial for heart health.