Life Processes in Animals

About this chapter

Life Processes in Animals is Chapter 9 of Class 7 Curiosity. Building on the Grade 6 idea that nutrition, respiration, excretion and reproduction are collectively called life processes, this chapter goes deep into two of them — nutrition and respiration — and connects them to the circulatory system. Students trace food through the human alimentary canal: mouth (teeth crush food, saliva begins starch digestion), oesophagus (wave-like contractions push food to the stomach), stomach (digestive juice with acid and mucus breaks down protein), small intestine (about 6 m long, receives bile from the liver and pancreatic juice from the pancreas, has finger-like projections that absorb nutrients into the blood), large intestine (about 1.5 m, absorbs water and forms stool stored in the rectum, expelled through the anus — a process called egestion). Variations across animals: cows and buffaloes are ruminants that bring partially-digested food back for rumination; birds use a muscular gizzard with swallowed grit. Respiration: nostrils, nasal passage, windpipe, two lungs with alveoli; the diaphragm and ribs power breathing; lime water turns milky on contact with exhaled air, proving more carbon dioxide is breathed out; respiration equation Glucose + Oxygen → Carbon dioxide + Water + Energy; inhaled air has nearly 21% oxygen and exhaled air nearly 16–17%. Other animals: fish use gills, frogs (amphibians) use lungs, skin and (as tadpoles) gills, earthworms use moist skin. Breathing is physical; respiration is chemical. The circulatory system with heart, blood and blood vessels carries nutrients, oxygen and wastes. CTET Paper 2 Science tests this chapter through alimentary-canal ordering, juice–part matching (bile–liver, pancreatic juice–pancreas), gizzard–grit, ruminant rumination, diaphragm–rib mechanism, lime-water test and breathing-organs-by-animal pairings. The four tests — Practice 15, Quiz 15, Hard 15, Mastery 30 — cover these ideas at exam depth.