NCERT Solutions for Class 7th Science Chapter 9 Life Processes in Animals
Updated on 2026-09-19
About this chapter
Nutrition, respiration, circulation, excretion and reproduction are the life processes that keep an animal alive. This chapter takes up nutrition and respiration in detail. Complex food components — carbohydrate, protein and fat — are broken into simpler forms inside a long tube called the alimentary canal , which runs from the mouth to the anus. Digestion begins in the mouth: teeth do mechanical digestion and saliva starts changing starch into sugar. The stomach adds digestive juice, acid and mucus; the liver adds bile and the pancreas adds pancreatic juice. The small intestine (about 6 m) is the longest part of the canal. Its thin inner lining carries thousands of finger-like projections that absorb the digested nutrients into the blood. The large intestine (about 1.5 m) is shorter but w
- .1 Nutrition in Animals
- .1.1 Digestion in human beings
- .1.2 Do all animals digest food the same way as humans do?
- .2.1 Respiration in humans
- .2.2 Do other animals breathe the same way as humans do?
- Chapter exercises
- Interdisciplinary projects
Quick revision
| Term | What it means | Example / detail from the chapter | Point to remember |
|---|---|---|---|
| Alimentary canal | The long tube in which food is digested | Mouth → oesophagus → stomach → small intestine → large intestine → anus | Liver and pancreas are associated parts, not part of the tube |
| Mechanical digestion | Breaking food into fine pieces without changing it chemically | Crushing and chewing by the teeth | Happens mainly in the mouth |
| Saliva | Watery fluid of the mouth that carries a digestive juice | Breaks starch of chapati or rice into sugar — that is why it tastes sweet on long chewing | Iodine test: starch gives blue-black colour |
| Oesophagus (food pipe) | Flexible tube from mouth to stomach | Its walls contract and relax in a wave-like motion | This wave-like movement occurs all along the canal |
| Stomach | Muscular bag that churns food | Secretes digestive juice, acid and mucus | Acid kills bacteria; mucus protects the stomach lining |
| Bile | Mildly basic secretion of the liver | Neutralises the acid coming from the stomach and breaks fat into tiny droplets | Liver is the largest gland of the body |
| Pancreatic juice | Basic juice secreted by the pancreas | Acts on carbohydrate, protein and fat | Also helps neutralise acid in the food |
| Absorption | Passing of digested nutrients into the blood | Through the finger-like projections of the small intestine | The projections increase the surface area |
| Egestion | Removal of undigested waste through the anus | Semi-solid stool stored in the rectum | Fibre-rich food makes stool easier to pass |
| Rumination | Bringing partly digested food back to the mouth for thorough chewing | Cow, buffalo, goat — the ruminants | A cow chews for about 8 hours a day |
| Gizzard | Muscular chamber in birds that grinds food | Works with grit (small stones) the bird swallows | Birds have no teeth |
| Breathing | Taking air in (inhalation) and pushing it out (exhalation) | Ribs move up and out, diaphragm moves down while inhaling | A physical process |
| Alveoli | Balloon-like sacs at the ends of the finest branches in the lungs | Thin walls surrounded by fine blood-carrying tubes | The actual site of gas exchange |
| Respiration | Breakdown of glucose using oxygen to release energy | Glucose + Oxygen → Carbon dioxide + Water + Energy | A chemical process, happens inside the body |
| Gills | Specialised breathing structures of most aquatic animals | Fish, and tadpoles of frogs | Richly supplied with blood vessels |
Exercises
- .1 Nutrition in Animals — In-text Questions Page 1229
- .1.1 Digestion in human beings — In-text Questions Page 1239
- .1.1 Digestion in human beings — Science and Society Page 1239
- .1.1 Digestion in human beings — Activity 9.1: Let us investigate Page 1239
- .1.1 Digestion in human beings — In-text Questions Page 1249
- .1.1 Digestion in human beings — In-text Question Page 1259
- .1.1 Digestion in human beings — In-text Questions Page 1269
- .1.2 Do all animals digest food the same way as humans do? — In-text Question Page 1279
- .2.1 Respiration in humans — In-text Questions Page 1299
- .2.1 Respiration in humans — Activity 9.2: Let us make a model Page 1309
- .2.1 Respiration in humans — In-text Question Page 1319
- .2.1 Respiration in humans — Activity 9.3: Let us explore Page 1319
- .2.1 Respiration in humans — In-text Question Page 1329
- .2.2 Do other animals breathe the same way as humans do? — In-text Question Page 1339
- Chapter exercises — Let Us Enhance Our Learning Page 135 & 136
- Interdisciplinary projects — Exploratory Projects Page 136