Chapter 9: Life Processes in Animals
Why does chapati taste sweet when you chew it long, why does a cow keep chewing, and how does the air we breathe give us energy? In this chapter we follow food along the alimentary canal, test starch with iodine, see how ruminants and birds digest food differently, build a model of breathing, and compare how humans, fish, frogs and earthworms breathe.
In this chapter you will
- trace food through the human digestive system
- describe digestion in ruminants and birds
- explain breathing, gas exchange and respiration
- compare breathing organs of different animals
Topics
- Digestion in Human Beings NCERT 9.1.1
Digestion: mouth (chewing, saliva on starch) → food pipe → stomach (acid, protein) → small intestine (bile, pancreatic juice, absorption).
- Nutrition in Other Animals NCERT 9.1.2
Ruminants like cows partly digest grass in the rumen, then bring it back to chew again.
- Respiration in Humans NCERT 9.2.1
Air: nostrils → windpipe → lungs → alveoli, where oxygen enters blood and CO₂ leaves.
- Breathing in Other Animals NCERT 9.2.2
Land animals use lungs; fish use gills to take oxygen dissolved in water.
Key words
- Alimentary canal
- the food tube from mouth to anus
- Digestion
- breaking food into simple substances
- Absorption
- digested food passing into the blood
- Rumination
- chewing food brought back from the stomach
- Alveoli
- tiny air sacs in the lungs for gas exchange
- Respiration
- breaking glucose with oxygen to release energy
- Gills
- breathing organs of fish
Summary
- Digestion runs mouth → food pipe → stomach → small intestine (absorption) → large intestine (water) → anus.
- Saliva digests starch; stomach acid kills germs; bile and pancreatic juice neutralise acid.
- Ruminants chew the cud; birds grind food in a gizzard.
- Gas exchange happens in the alveoli; respiration releases energy; fish use gills, earthworms their skin.