Science · Class 7 · Chapter 9

Life Processes in Animals

• Alimentary canal — The tube from mouth to anus where digestion happens.
• Digestion / Absorption — Breaking food down / nutrients entering the blood.
• Egestion — Expelling undigested waste as stool.
• Rumination — Bringing food back up to chew again.
• Gizzard — A bird's muscular food-grinding chamber.
• Breathing — The physical movement of air in and out.
• Respiration — The chemical release of energy from glucose.
• Gills — Organs for exchanging gases with water.

Chapter 9 · Concept 1 of 9

The Alimentary Canal

• Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus

Chapter 9 · Concept 2 of 9

The Mouth and the Stomach

• The mouth — Teeth crush food (mechanical digestion), while saliva chemically breaks starch into sugar — which is why chewed starchy food tastes sweet.
• The stomach — Digestive juice, acid, and mucus break down proteins, kill harmful bacteria, and protect the stomach's own lining.

Chapter 9 · Concept 3 of 9

The Small and Large Intestine

• Small intestine — About 6 metres long. Receives bile (from the liver) and pancreatic juice (from the pancreas), and its own wall absorbs nutrients into the blood through finger-like projections.
• Large intestine — Absorbs water and salts from undigested food, forming stool — stored in the rectum and expelled through the anus.

Chapter 9 · Concept 4 of 9

Rumination in Cows

• Ruminants like cows and buffaloes chew grass partially, swallow it, partially digest it, then bring it back to the mouth to chew thoroughly.
• 8 hours a day — That's roughly how much time a cow spends chewing — including food it already swallowed once.

Chapter 9 · Concept 5 of 9

The Bird's Gizzard

• Grinding without teeth — Birds have a muscular gizzard that grinds food by contracting and relaxing — often with the help of swallowed grit (small stones).

Chapter 9 · Concept 6 of 9

Breathing

• Inhalation — Ribs move up and outward, the diaphragm moves down — chest space increases, and air enters the lungs.
• Exhalation — Ribs move down and inward, the diaphragm moves up — pushing air back out.

Chapter 9 · Concept 7 of 9

Respiration

• The body uses oxygen to break down glucose from digested food, releasing energy.
• Glucose + Oxygen → Carbon dioxide + Water + Energy — This exchange happens at the alveoli — tiny air sacs in the lungs — where oxygen enters the blood and carbon dioxide leaves it.

Chapter 9 · Concept 8 of 9

Breathing Is Not the Same as Respiration

• Breathing — A physical process — the movement of air in and out of the lungs.
• Respiration — A chemical process — releasing energy from glucose, using oxygen, inside cells.

Chapter 9 · Concept 9 of 9

How Other Animals Breathe

• Animal | Breathing organ
• Most land animals (birds, mammals, reptiles) — Lungs
• Fish — Gills
• Frog (tadpole → adult) — Gills → lungs and skin
• Earthworm — Moist skin

Quick Recap

Check Your Understanding

1. 1Complete the journey of food through the alimentary canal: Food → Mouth → ___ → Stomach → ___ → ___ → Anus.
2. 2Unchewed chapati, chewed chapati, and boiled mashed potato are each tested with iodine solution. What would you observe in each, and why?
3. 3What is the role of the diaphragm in breathing? (i) Filtering air (ii) Producing sound (iii) Helping inhalation and exhalation (iv) Absorbing oxygen