Life Processes in Animals

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digestion

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starch

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acid

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ruminants

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SARS-CoV-2

gills

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False (they must be broken down into simpler forms first)

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False (it contains digestive juice, acid, and mucus)

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False (bile is secreted by the liver; the pancreas secretes pancreatic juice)

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False (breathing is a physical process of inhaling and exhaling air; respiration is a chemical process of breaking down glucose to release energy)

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False (inhaled air contains nearly 0.04% carbon dioxide; exhaled air contains about 4–5%)

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False (during exhalation the ribs move down and inwards and the diaphragm moves upwards)

(i)–(a), (ii)–(d), (iii)–(b), (iv)–(c), (v)–(e)

(i)–(a), (ii)–(b), (iii)–(c), (iv)–(d), (v)–(e)

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(d) (A is false — the large intestine is called large because it is wider; R is true)

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(a) (Breathing is a physical process; R correctly describes respiration)

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(c) (The projections increase the surface area for efficient nutrient absorption)

Hint: Processes essential for the survival of living beings, e.g., nutrition, respiration, circulation, excretion, reproduction.

Hint: Complex components like carbohydrate, protein, and fat must be broken into simpler forms before the body can use them — for energy, growth, and repair.

Hint: The initial breakdown of food into fine pieces by crushing and chewing (by the teeth); it occurs in the mouth.

Hint: Chapati contains starch; saliva contains a digestive juice that breaks down starch into sugar; hence the sweet taste.

Hint: Glucose + Oxygen → Carbon dioxide + Water + Energy.

Hint: Digestive juice (breaks down proteins), acid (helps break down proteins and kills many harmful bacteria), mucus (protects the stomach lining from the acid).

Hint: It protects the stomach lining from the acid, preventing damage.

Hint: It helps break down proteins and also kills many harmful bacteria present in food.

Hint: The walls of the food pipe gently contract and relax in a wave-like motion, pushing food down into the stomach; this movement takes place throughout the alimentary canal.

Hint: Mouth → oesophagus (food pipe) → stomach → small intestine → large intestine → rectum → anus.

Hint: Liver — secretes bile that neutralises acid and breaks fats into tiny droplets; Pancreas — secretes basic pancreatic juice that neutralises acid and breaks down carbohydrates, proteins, and fats.

Hint: Its inner lining is thin and has thousands of finger-like projections which increase the surface area, allowing digested nutrients to pass into the blood efficiently.

Hint: The large intestine absorbs water and some salts, making the waste semi-solid (stool); stool is stored in the rectum and expelled through the anus (egestion).

Hint: A condition in which the body reacts to gluten (a protein in wheat, barley, and rye), damaging the inner lining of the small intestine; managed by avoiding gluten-containing foods — millets are good gluten-free alternatives.

Hint: The process in which partially digested food is brought back to the mouth for gradual chewing; e.g., cows, buffaloes (goats).

Hint: Birds have no teeth; the gizzard breaks down food by the contraction and relaxation of its walls, often with the help of swallowed grit (small stones).

Hint: Breathing is the physical process of inhaling and exhaling air; respiration is the chemical process in which oxygen breaks down glucose to release energy (carbon dioxide and water are produced).

Hint: A dome-shaped muscle below the lungs; it moves downwards during inhalation (increasing chest space so air enters the lungs) and upwards during exhalation (reducing space and pushing air out).

Hint: Lime water reacts with carbon dioxide to turn milky; exhaled air contains more carbon dioxide than inhaled air, which shows we exhale more CO₂.

Hint: Breathing becomes faster; during running the body needs more energy, so respiration increases and more oxygen is taken in and more carbon dioxide removed quickly.

Introduction: The human alimentary canal is a long tube that begins at the mouth and ends at the anus, through which food passes and gets digested step by step.
Key Points:
1. Mouth and oesophagus — Teeth break food into smaller pieces; saliva digests starch, and food moves through the oesophagus by wave-like contractions.
2. Stomach — The stomach walls churn food and mix it with digestive juice, acid, and mucus to partially digest proteins.
3. Small and large intestine — The small intestine completes digestion and absorbs nutrients; the large intestine absorbs water and forms stool expelled through the anus.
Conclusion: Thus, food travels through a series of specialised organs that progressively digest it and absorb nutrients before waste is removed.

Introduction: Saliva contains a digestive juice that breaks down starch into simpler sugars, which can be shown using a simple iodine test.
Key Points:
1. Set up test tubes — Take two test tubes A and B; put plain boiled rice in A and chewed boiled rice in B, then add water to both.
2. Add iodine solution — Add 3–4 drops of iodine solution into both test tubes and mix the contents separately.
3. Observe the colour — Test tube A turns blue-black showing starch is present, while test tube B shows little or no colour change as saliva has broken down starch.
Conclusion: This activity proves that saliva digests starch and converts it into simpler sugars.

Introduction: The small intestine is specially structured to maximise the absorption of digested nutrients into the blood.
Key Points:
1. Long length — The small intestine is about 6 metres long, providing a large surface area and enough time for complete digestion and absorption.
2. Thin inner lining — The walls of the small intestine are thin, allowing digested nutrients to easily pass into the blood vessels.
3. Finger-like projections — Thousands of finger-like projections increase the surface area greatly, enabling efficient absorption of nutrients into the blood.
Conclusion: These features make the small intestine highly efficient at absorbing digested food and passing nutrients into the blood.

Introduction: The small intestine receives secretions from the liver and pancreas that play key roles in completing digestion.
Key Points:
1. Bile from liver — Bile is mildly basic; it neutralises stomach acids and breaks down fats into tiny droplets for easier digestion.
2. Pancreatic juice — Pancreatic juice is basic in nature, neutralises acids, and breaks down carbohydrates, proteins, and fats.
3. Combined action — Together with the digestive juice from the small intestine wall, they break down food into simpler absorbable forms.
Conclusion: Bile and pancreatic juice together ensure that fats, proteins, and carbohydrates are fully broken down in the small intestine.

Introduction: Grass-eating animals like cows and buffaloes are called ruminants, and they need to chew their food thoroughly to digest tough grass.
Key Points:
1. Partial chewing and swallowing — Ruminants partially chew the grass and swallow it into the stomach, where partial digestion takes place.
2. Bringing food back to mouth — The partially digested food is brought back to the mouth for gradual and thorough chewing; this is called rumination.
3. Need for long chewing — Grass is tough and fibrous, so a cow spends about 8 hours a day chewing to break it down completely for proper digestion.
Conclusion: Rumination allows ruminants to break down tough plant material thoroughly so that nutrients can be absorbed efficiently.

Introduction: Inhaled air follows a specific pathway through the respiratory system before reaching the lungs for gas exchange.
Key Points:
1. Nostrils and nasal passages — Air enters through the nostrils into the nasal passages, where tiny hair and mucus trap dust and dirt.
2. Windpipe — From the nasal passages, the air travels down the windpipe, which then forms two branches entering the two lungs.
3. Alveoli — Inside the lungs, these branches divide into finer branches ending in balloon-like sacs called alveoli, where gas exchange occurs.
Conclusion: The air travels from nostrils through nasal passages, windpipe, and lung branches to finally reach the alveoli.

Introduction: Breathing involves the movement of air into and out of the lungs, controlled by the ribs and the diaphragm.
Key Points:
1. Inhalation — During inhalation, the ribs move up and outwards and the diaphragm moves downwards, increasing chest space so air enters the lungs.
2. Exhalation — During exhalation, the ribs move down and inwards and the diaphragm moves upwards, reducing chest space and pushing air out.
3. Role of diaphragm — The dome-shaped diaphragm below the lungs is the key muscle that creates the pressure changes needed for breathing.
Conclusion: The coordinated movement of the ribs and diaphragm drives the physical process of breathing in humans.

Introduction: The alveoli are tiny balloon-like sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.
Key Points:
1. Thin walls and blood vessels — Alveoli have thin walls surrounded by fine tubes containing blood, allowing easy gas exchange.
2. Oxygen enters blood — Oxygen from the air in the alveoli passes into the blood and is transported to all parts of the body.
3. Carbon dioxide released — Blood carrying carbon dioxide from the body releases it into the alveoli to be exhaled out.
Conclusion: The alveoli efficiently exchange oxygen and carbon dioxide between the air and the blood.

Introduction: A simple working model can be built to demonstrate the mechanism of breathing in humans.
Key Points:
1. Balloons represent lungs — The two balloons attached to the forked end of the Y-tube represent the two lungs in the human body.
2. Rubber sheet represents diaphragm — The thin rubber sheet at the base of the bottle represents the dome-shaped diaphragm muscle.
3. Working of the model — Pulling the rubber sheet downwards inflates the balloons (inhalation); releasing it upwards deflates them (exhalation).
Conclusion: This model clearly shows how the diaphragm's movement causes air to enter and leave the lungs during breathing.

Introduction: The composition of inhaled and exhaled air differs, which shows how the body uses oxygen and produces carbon dioxide.
Key Points:
1. Oxygen content — Inhaled air contains nearly 21% oxygen, while exhaled air contains about 16–17% oxygen, showing that the body uses some oxygen.
2. Carbon dioxide content — Inhaled air has about 0.04% carbon dioxide, while exhaled air has about 4–5% carbon dioxide, showing that the body produces carbon dioxide.
3. What it tells us — This difference shows that the body takes in oxygen for respiration and releases carbon dioxide as a waste product.
Conclusion: The comparison proves that respiration uses oxygen from inhaled air and releases more carbon dioxide in exhaled air.

Introduction: Different animals have developed different breathing mechanisms suited to the habitats in which they live.
Key Points:
1. Fish — Fish live in water and breathe through gills, which are richly supplied with blood vessels for exchanging gases dissolved in water.
2. Frog — Frogs are amphibians; tadpoles breathe through gills, while adult frogs use lungs on land and moist skin for gas exchange in water.
3. Earthworm — Earthworms live in soil and use their moist skin for the exchange of oxygen and carbon dioxide.
Conclusion: Animals have adapted their breathing organs to suit their specific habitats and ways of life.

Introduction: The circulatory system is the body's transport system that carries essential substances to all parts of the body.
Key Points:
1. Components — The circulatory system includes the heart, blood, and blood vessels, which work together to transport substances.
2. Transport of nutrients and oxygen — The heart pumps blood through blood vessels to deliver nutrients and oxygen to every part of the body.
3. Removal of waste — The circulatory system also carries away waste products such as carbon dioxide from the body cells.
Conclusion: The circulatory system ensures that nutrients, oxygen, and waste products are transported efficiently throughout the body.

Introduction: Smoking is extremely harmful to health as it damages the lungs and causes serious diseases.
Key Points:
1. Harm to smoker — Smoking damages the lungs and increases the risk of lung cancer, respiratory illnesses, persistent coughing, and frequent infections.
2. Passive smoking — Passive smoking occurs when non-smokers inhale toxic chemicals released into the air by someone else's smoking.
3. Who is at risk — Passive smoking is especially dangerous for children, pregnant women, and the elderly who breathe in the polluted air.
Conclusion: Avoiding smoking protects both personal health and the well-being of those around us.

Introduction: A simple lime water experiment shows that exhaled air contains more carbon dioxide than inhaled air.
Key Points:
1. Set up two test tubes — Take freshly prepared lime water in two test tubes A and B in equal amounts.
2. Pass different air — Pass inhaled air into test tube A using a syringe or pichkari, and blow exhaled air into test tube B through a straw.
3. Observe the colour — The lime water in test tube B turns milky while test tube A does not, proving exhaled air has more carbon dioxide.
Conclusion: Since lime water turns milky with carbon dioxide, the experiment proves we exhale more carbon dioxide than we inhale.

Introduction: Breathing and respiration are two different processes, and the right questions can help Sahil understand the difference.
Key Points:
1. Question on nature of process — "Is breathing just the physical movement of air in and out of the lungs, while respiration is a chemical process that releases energy from food?"
2. Question on where it happens — "Does breathing happen only in the lungs, while respiration occurs inside the cells of the body where glucose is broken down?"
Conclusion: These questions help Sahil see that breathing is a physical process, while respiration is a chemical process that releases energy.

Hint: (a) The action of saliva in breaking down starch. (b) Test tube A turns blue-black; test tube B shows no blue-black colour (or very light). (c) Starch is present in A, but in B saliva has broken down the starch into simple sugars, showing that saliva digests starch; digestion of starch begins in the mouth.

Hint: (a) Oesophagus (food pipe). (b) Saliva moistens the chewed food and the tongue mixes it, making a softened mass. (c) Wave-like contraction and relaxation of the walls pushes food forward throughout the alimentary canal — it is not merely gravity — so yes, the wave-like movement can still push food towards the stomach.

Hint: (a) Alveoli. (b) Trap dust and dirt from the air we breathe in. (c) Rib cage — protects the lungs; diaphragm — a dome-shaped muscle whose movement helps in inhalation and exhalation.

Hint: (a) Running muscles need more energy, so more oxygen is required to break down glucose and more carbon dioxide must be removed. (b) Respiration. (c) Possible reasons: Anusha ran faster/for a longer distance; she is less used to exercise so her body needed more effort; different fitness levels of the two girls.

Hint: (a) Protects the stomach lining from the acid, preventing damage. (b) Proteins. (c) The food we eat may carry harmful bacteria — the acid prevents them from harming us; without mucus, the acid would damage the stomach's own lining, since the acid also helps break down proteins.

Hint: (a) Stool. (b) Rectum. (c) Fibre-rich foods make the stool easier to pass, helping the large intestine function properly; the expulsion process is called egestion (through the anus).

Hint: (a) Rumination. (b) Ruminants. (c) The gizzard grinds food using muscular contraction and relaxation along with swallowed grit; animals show variations in the structure and function of the alimentary canal to adapt to different ways of digesting different kinds of food.

Hint: (a) Thin walls allow easy passage/exchange of gases. (b) Carbon dioxide. (c) They are small, balloon-like sacs with thin walls surrounded by fine blood tubes — gases can diffuse quickly between air and blood; oxygen is carried to all body parts by the circulatory system (blood pumped by the heart through blood vessels).

Hint: (a) Through gills. (b) Skin. (c) Gases must dissolve in moisture to pass through the skin — a moist skin allows exchange of oxygen and carbon dioxide; the frog uses lungs on land and skin in water, which helps it survive both on land and in water, showing adaptation over time to different environments.

Hint: (a) The respiratory system. (b) Non-smokers inhaling polluted air containing toxic chemicals released by smokers. (c) Damages the lungs; increases risk of lung cancer and other respiratory illnesses; persistent coughing and frequent infections; children, pregnant women, and the elderly are especially at risk from passive smoking.

Introduction: The human digestive system consists of the alimentary canal and associated glands that together break down food and absorb nutrients.
Key Points:
1. Mouth — Teeth break food into smaller pieces by chewing; saliva moistens food and breaks down starch into sugars, beginning digestion.
2. Oesophagus — The food pipe pushes the softened food down to the stomach through wave-like contractions and relaxations of its walls.
3. Stomach — The stomach walls churn food and mix it with digestive juice, acid, and mucus; proteins are partially digested and bacteria are killed.
4. Small intestine — It receives bile and pancreatic juice, completes the digestion of carbohydrates, proteins, and fats, and absorbs nutrients into the blood.
5. Large intestine and anus — The large intestine absorbs water and salts from undigested food, forming stool stored in the rectum and expelled through the anus.
Conclusion: Each part of the alimentary canal has a specialised function that ensures food is digested, nutrients are absorbed, and waste is removed.

Introduction: The small intestine is where most of the digestion and absorption of food takes place in the human body.
Key Points:
1. Secretions from liver — The liver secretes bile, which is mildly basic, neutralises stomach acids, and breaks down fats into tiny droplets for easier digestion.
2. Secretions from pancreas — The pancreas secretes basic pancreatic juice that neutralises acids and breaks down carbohydrates, proteins, and fats.
3. Intestinal juice — The wall of the small intestine secretes digestive juice that further breaks down fats, proteins, and partially digested carbohydrates into simpler forms.
4. Absorption of nutrients — Digested nutrients pass through the thin walls and finger-like projections into the blood vessels, which carry them to all body parts.
5. Longest part — The small intestine is about 6 metres long, making it the longest part of the alimentary canal, which allows complete digestion and absorption.
Conclusion: The small intestine's length, secretions, and finger-like projections make it the main site of digestion and nutrient absorption.

Introduction: Respiration is the process by which the body uses oxygen to break down food and release energy needed for all life activities.
Key Points:
1. Breathing in air — We inhale air through the nostrils; it travels through the windpipe into the lungs and reaches the alveoli.
2. Gas exchange in alveoli — In the alveoli, oxygen passes into the blood and carbon dioxide from the blood is released into the air to be exhaled.
3. Transport of oxygen — Blood carries oxygen from the lungs to all parts of the body where it is needed by the cells.
4. Breakdown of glucose — Inside the body, oxygen helps break down glucose from digested food to release energy.
5. Word equation — Glucose + Oxygen → Carbon dioxide + Water + Energy.
Conclusion: Respiration combines breathing and the chemical breakdown of glucose to release energy that powers all body activities.

Introduction: A working model of breathing can be made using simple materials to show how the diaphragm and lungs function.
Key Points:
1. Prepare the bottle — Take a wide transparent plastic bottle, remove its bottom, and make a hole in the lid.
2. Attach balloons to Y-tube — Fix two deflated balloons to the forked end of a Y-shaped hollow tube and secure them with rubber bands.
3. Insert tube and seal — Pass the straight end of the tube through the lid, seal the lid with clay, and attach a thin rubber sheet tightly over the open base.
4. Operate the model — Pull the rubber sheet downwards and the balloons inflate; release it upwards and the balloons deflate.
5. What each part represents — The balloons represent the lungs, the Y-tube represents the windpipe, and the rubber sheet represents the diaphragm.
Conclusion: This model demonstrates how the diaphragm's movement changes chest space to draw air into and push air out of the lungs.

Introduction: Inhaled and exhaled air differ in the amounts of oxygen and carbon dioxide they contain, which can be shown by a lime water experiment.
Key Points:
1. Oxygen content — Inhaled air has nearly 21% oxygen, while exhaled air has about 16–17% oxygen, as the body uses some oxygen during respiration.
2. Carbon dioxide content — Inhaled air has about 0.04% carbon dioxide, while exhaled air has about 4–5% carbon dioxide, showing the body produces it.
3. Lime water experiment setup — Take freshly prepared lime water equally in two test tubes A and B.
4. Passing air — Pass inhaled air into test tube A using a syringe or pichkari and blow exhaled air into test tube B through a straw.
5. Observation — The lime water in test tube B turns milky while test tube A does not, proving exhaled air has more carbon dioxide.
Conclusion: The comparison and the lime water experiment together prove that we use oxygen and release more carbon dioxide during respiration.

Introduction: Animals have different digestive systems adapted to the kind of food they eat, as seen in ruminants and birds.
Key Points:
1. Ruminant stomach and rumen — Grass-eating animals like cows partially chew grass and swallow it into the rumen, where partial digestion takes place.
2. Rumination process — The partially digested food is brought back to the mouth for thorough chewing; a cow spends about 8 hours a day chewing.
3. Need for adaptation — Grass is tough and fibrous, so the ruminant digestive system is designed to break it down slowly through repeated chewing.
4. Birds' digestive system — Birds do not have teeth; they have a chamber called a gizzard where food is broken down by wall contractions and swallowed grit.
5. Key difference — Ruminants re-chew partially digested food through rumination, while birds use a gizzard with small stones instead of teeth to grind food.
Conclusion: Ruminants and birds have differently structured digestive systems, each adapted to the type of food they consume.

Introduction: The human respiratory system is a set of organs that work together to bring oxygen into the body and remove carbon dioxide.
Key Points:
1. Nostrils and nasal passages — Air enters through the nostrils into the nasal passages, where tiny hair and mucus trap dust and dirt from the air.
2. Windpipe — The windpipe carries air from the nasal passages down into the lungs and branches into two tubes, one for each lung.
3. Lungs and alveoli — Inside the lungs, the branches divide into finer tubes ending in balloon-like sacs called alveoli where gas exchange occurs.
4. Rib cage — The lungs are protected by the rib cage, which also helps in the movement of breathing.
5. Diaphragm — The dome-shaped diaphragm muscle below the lungs moves down during inhalation and up during exhalation to drive breathing.
Conclusion: The human respiratory system, with its nostrils, windpipe, lungs, alveoli, rib cage, and diaphragm, ensures efficient breathing and gas exchange.

Introduction: Although breathing and respiration are closely linked, they are fundamentally different in nature and function.
Key Points:
1. Breathing is physical — Breathing is the physical movement of air into and out of the lungs involving the ribs and the diaphragm.
2. No chemical change in breathing — During breathing, air is simply taken in and pushed out; no new substances are formed in the lungs.
3. Respiration is chemical — Respiration is a chemical process inside the body where oxygen breaks down glucose to release energy.
4. New substances formed — In respiration, glucose and oxygen are converted into carbon dioxide, water, and energy, which are new substances.
5. Example — When we run, breathing brings in oxygen (physical), while respiration uses that oxygen to break down food and release energy (chemical).
Conclusion: Breathing is a physical act of moving air, while respiration is a chemical reaction that releases energy from food using that air.

Introduction: Different animals have different breathing organs adapted to the habitats in which they live.
Key Points:
1. Fish — Fish live in water and breathe through gills richly supplied with blood vessels that exchange gases dissolved in water.
2. Frog — Frogs are amphibians; tadpoles breathe through gills, while adult frogs use lungs on land and moist skin for gas exchange in water.
3. Earthworm — Earthworms live in soil and use their moist skin for the exchange of oxygen and carbon dioxide.
4. Birds — Birds breathe through lungs; although their lung structure differs from humans, they are adapted to fly at high altitudes with low oxygen.
5. Adaptation to habitat — Each animal's breathing organ is suited to its surroundings, whether in water, on land, or in the air.
Conclusion: Animals have evolved different breathing mechanisms and organs that suit the specific habitats in which they live.

Introduction: The circulatory system works with the digestive and respiratory systems to ensure the body receives the energy it needs.
Key Points:
1. Digestive system — The digestive system breaks down food into simple nutrients like glucose, which are absorbed into the blood in the small intestine.
2. Respiratory system — The respiratory system brings in oxygen through breathing, and gas exchange in the alveoli puts oxygen into the blood.
3. Circulatory system — The circulatory system, made of the heart, blood, and blood vessels, transports nutrients and oxygen to all body parts.
4. Release of energy — Inside the cells, oxygen breaks down glucose to release energy through the chemical process of respiration.
5. Removal of waste — The circulatory system also carries away waste products like carbon dioxide from the cells to the lungs for removal.
Conclusion: The three systems work together so that nutrients and oxygen reach every cell, energy is released, and waste is carried away.