🫀 Life Processes in Animals

🌿 What Do Animals Eat? (NCERT)

Animals eat different types of food. Look at these examples:

🔑 Autotrophs vs Heterotrophs

👄 Beginning with the Mouth Cavity

• Teeth — break food by crushing and chewing (mechanical digestion):
  • Incisors (8): cutting
  • Canines (4): tearing
  • Premolars (8): crushing and grinding
  • Molars (12): grinding
• Tongue — mixes food with saliva; helps push food to the back of the mouth for swallowing
• Salivary glands — produce saliva which contains a digestive juice that helps break down starch into sugar — this is why chapati or rice tastes sweet when chewed for 30–60 seconds!
• The well-chewed food mixed with saliva forms a soft ball called a bolus

🔬 Activity — The Chapati Experiment

Take a small piece of chapati or a bite-sized portion of boiled rice and chew it properly for 30–60 seconds.

• At first, the chapati or rice has its usual taste.
• As you continue chewing, the food begins to taste sweet!
• Why? Chapati/rice contains starch (a carbohydrate). Saliva breaks starch down into sugar — hence the sweet taste.

🧪 Activity — Iodine Test for Starch

🦷 Science and Society — Oral Hygiene

A healthy mouth requires good oral hygiene. We should:

• Brush our teeth and clean our tongue twice a day
• Rinse our mouth with water after each meal
• This prevents tooth decay and bad smell in the mouth

🫁 Food Pipe (Oesophagus) — Fig. 9.2

Fig. 9.2 — Movement of food in the food pipe

• A long, flexible tube connecting the mouth to the stomach
• 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 is called peristalsis — it takes place throughout the entire alimentary canal and pushes food forward
• No digestion of food occurs in the oesophagus

🟡 Stomach

Fig. 9.3: Stomach — showing digestive juice, acid and mucus secreted from the stomach wall

• Digestive juice — breaks down proteins into simpler components
• Acid — not only helps break down proteins but also kills many harmful bacteria
• Mucus — protects the stomach lining from the acid, preventing damage

⭐ Fascinating Facts — How did scientists learn about digestion?

In 1822, a man named Alexis St. Martin was accidentally shot in the stomach. He was treated by a doctor, 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.

🟢 Small Intestine

Fig. 9.4 — Alimentary canal if it is stretched out

• Bile (from the liver) — mildly basic in nature; neutralises acids present in food coming from the stomach; breaks down fats into tiny droplets, making fat digestion easier
• Pancreatic juice (from the pancreas) — also basic in nature; neutralises acids in the food; breaks down carbohydrates, proteins, and fats
• Intestinal juice (from the wall of the small intestine) — further breaks down fats, proteins, and partially digested carbohydrates into simpler forms

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.

The inner lining of the small intestine is thin and has thousands of finger-like projections (Fig. 9.5) 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.

Fig. 9.5 — Inner lining of the small intestine showing finger-like projections

🌿 Science and Society — Celiac Disease

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.

🔵 Large Intestine

🌿 Science and Society — Digestion and Good Health

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 also emphasise eating meals at proper timings, practising mindful eating, and avoiding overeating as key factors in maintaining digestive health.

⭐ Fascinating Facts — Bacteria in the Large Intestine

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.

🐄 Ruminants (Cows, Buffaloes)

Fig. 9.6 — Digestive system of a ruminant

• Ruminants have a special stomach chamber called the rumen where partial digestion and storage of grass takes place
• The partially digested food (cud) is regurgitated (brought back up) to the mouth for thorough chewing
• This adaptation helps them digest tough grass and plant fibres that are hard to digest

🐦 Birds — The Gizzard

Fig. 9.7 — Digestive system in birds

• The gizzard acts as a mechanical grinder — it does the job that teeth do in humans
• Birds swallow grit (small stones or sand) which help grind hard seeds and food inside the gizzard

💨 How do we breathe?

• Nostrils — a pair of nasal openings through which we inhale and exhale air
• Nasal passages — air passes through; tiny hair and mucus trap dust and dirt → this is why we should breathe through the nose, not mouth
• Windpipe (trachea) — carries air from nasal passages to the lungs; forms two branches entering the two lungs
• Lungs — branches divide into smaller and finer branches ending in small balloon-like sacs called alveoli (Fig. 9.8); lungs are protected by the rib cage

⚠ Breathing vs Respiration — Important Difference!

🌿 Science and Society — Respiratory Health

While a lot of the dust is filtered out from the inhaled air, often small infectious particles can get through to 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.

🔬 Activity 9.2 — A Model to Show the Mechanism of Breathing

Fig. 9.9 — Model to show mechanism of breathing

• Take a wide transparent plastic bottle with a lid; remove its bottom
• Fix two deflated balloons to the forked ends of a Y-shaped hollow tube; insert through the lid
• Attach a thin rubber sheet tightly to the open base of the bottle
• Pull rubber sheet downwards → balloons inflate (like inhaling)
• Release rubber sheet upwards → balloons deflate (like exhaling)
• The balloons = lungs; the rubber sheet = diaphragm

🫁 Mechanism of Breathing (Fig. 9.10)

Fig. 9.10 — Mechanism of breathing: (a) Inhalation  |  (b) Exhalation

🔬 Activity 9.3 — What do we breathe out?

To be demonstrated by the teacher

Fig. 9.11 — (a) Air pumped in using syringe  |  (b) Exhaled air blown through straw

🫧 How does the exchange of gases happen? (Fig. 9.12)

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 (Fig. 9.12).

• Blood carries CO₂ from the body to the alveoli, where it is released into the air
• Oxygen from the alveoli passes into the blood and is transported to all parts of the body

Fig. 9.12 — Gas exchange through the alveoli

⚡ How does food give us energy? — Respiration

During breathing, we inhale air and exhale air having more carbon dioxide than the inhaled air. Note that not all the oxygen is used up (Fig. 9.13). Some other animals can use a larger fraction of the oxygen during respiration.

Fig. 9.13 — Percentage of O₂ and CO₂ in inhaled vs exhaled air

This exchange of gases ensures that each part of our body gets oxygen to produce energy and remove waste products.

🚭 Science and Society — Smoking is Harmful

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. Avoiding smoking helps protect both personal health and the well-being of those around us.

🩸 Blood — Liquid Connective Tissue

🔄 Double Circulation

Blood passes through the heart twice per complete circulation → called Double Circulation. Heartbeat: ~70–72 beats/minute. Heart sounds: Lub-Dub (valves closing).

🧪 What is Excreted?

Q1. Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts —
Given: Food, Mouth, Stomach, Anus

Blue boxes = given; Green boxes = filled in answers

Q2. Sahil placed chapati pieces in test tube A; Neha placed chewed chapati in B; Santushti took boiled mashed potato in C. All added iodine solution. What would their observations be? Give reasons.

• Test Tube A (chapati pieces + iodine): Turns blue-black — starch is present, not yet broken down by any enzyme.
• Test Tube B (chewed chapati + iodine): Does NOT turn blue-black — saliva (salivary amylase) has already broken down starch into sugars during chewing, so no starch remains to react with iodine.
• Test Tube C (boiled mashed potato + iodine): Turns blue-black — potato contains starch. Boiling and mashing do not digest starch chemically, so it still reacts with iodine.

Q3. What is the role of the diaphragm in breathing?
(i) To filter the air  (ii) To produce sound  (iii) To help in inhalation and exhalation  (iv) To absorb oxygen

Q4. Match the following

Q5. Anil claims that respiration and breathing are the same process. What questions can Sanvi ask him to make him understand he is not correct?

• "Breathing only involves moving air in and out of the lungs — but can you explain the chemical reaction that provides energy to the body?"
• "Does breathing happen in every cell of the body, or only in the lungs? Respiration happens in every cell — where does breathing happen?"
• "Breathing is a physical process — can you tell me what chemical process produces energy from glucose in our cells?"

Q6. Which statement is correct and why?
Anu: "We inhale air."  |  Shanu: "We inhale oxygen."  |  Tanu: "We inhale air rich in oxygen."

Q7. We often sneeze when we inhale a lot of dust-laden air. What can be possible explanations for this?

• The nasal passages are lined with tiny hairs and a layer of mucus that trap dust and dirt particles from inhaled air.
• When a large amount of dust is inhaled, these particles irritate the sensitive lining (mucous membrane) of the nasal passages.
• The irritation triggers a reflex action — the body forces a sudden burst of air through the nose and mouth to expel the irritant. This is called a sneeze.
• Sneezing is a protective mechanism that clears the nasal passages of dust, pollen, or pathogens before they can reach deeper into the respiratory tract.

Q8. After their morning run, Anusha was breathing faster than Paridhi. Provide at least two possible explanations for why.

• Explanation 1 — More physical exertion: Anusha may have run a longer distance or at a faster speed than Paridhi. Greater exertion means muscles use more oxygen and produce more CO₂, increasing the breathing rate.
• Explanation 2 — Lower fitness level: Anusha may be less physically fit. A less efficient respiratory and circulatory system requires more breaths per minute to supply the same amount of oxygen to muscles.
• Explanation 3 — Health or other factors: Anusha may have a respiratory condition, or environmental factors (running in a dusty area) could have increased her breathing rate.

Q9. Yadu added rice flour (+ water) to test tube A, and rice flour + water + saliva to test tube B. After 35–45 min, he added iodine to both (Fig. 9.15). What does he want to test?

Fig. 9.15 — Experimental Results (Test Tubes A and B)

• What Yadu wants to test: Whether saliva helps in the digestion of starch — specifically, does saliva break down the starch present in rice flour?
• Expected results: Test tube A (no saliva) turns blue-black with iodine — starch is unchanged. Test tube B (with saliva) does NOT turn blue-black — salivary amylase broke down the starch into sugars.
• Conclusion: Saliva contains salivary amylase which digests starch. Digestion of starch begins in the mouth itself.

Q10. Rakshita filled two test tubes with lime water. In test tube A, she passed inhaled (atmospheric) air; in test tube B, she blew exhaled air (Fig. 9.16). What is she investigating? How can she confirm her findings?

Fig. 9.16 — Experimental Setup (Lime Water Test)

• What she is investigating: Whether exhaled air contains more carbon dioxide than inhaled air.
• How to confirm: Lime water (Ca(OH)₂) turns milky white when CO₂ is passed through it, forming calcium carbonate (CaCO₃). Test tube A (inhaled air) will remain clear. Test tube B (exhaled air) will turn milky, confirming that exhaled air is richer in CO₂.
• Conclusion: We exhale more carbon dioxide than we inhale — CO₂ is a waste product of cellular respiration occurring in every cell of the body.