Notes Chapter 9 Class 7 Science Curiosity NCERT

Life Processes in Animals

Food provides energy; complex components (carbohydrates, proteins, fats) are broken down in the alimentary canal (mouth to anus).

Mouth: Teeth crush food; saliva breaks starch into sugar.
Oesophagus: Pushes food to stomach via wave-like contractions.
Stomach: Churns food; digestive juice breaks proteins; acid kills bacteria; mucus protects stomach lining.
Small Intestine: Longest part (~6m); liver (bile) and pancreas (pancreatic juice) aid digestion; villi absorb nutrients into blood.
Large Intestine: Absorbs water/salts; forms stool; expelled via anus (egestion).
Tips: Fiber-rich foods (fruits, vegetables) aid digestion; maintain oral hygiene (brush twice daily).

Ruminants (e.g., cows): Partially chew grass, store in rumen, chew again (rumination).
Birds: Use gizzard with grit to grind food (no teeth).

Respiration: Chemical process; breaks glucose with oxygen to release energy.
Breathing: Physical process of inhaling/exhaling air.

Parts: Nostrils, nasal passages (trap dust), windpipe, lungs (with alveoli), rib cage, diaphragm.

Breathing Mechanism:

Gas Exchange: In alveoli, oxygen enters blood, carbon dioxide is exhaled.

Respiration Equation: Glucose + Oxygen → Carbon dioxide + Water + Energy.
Inhaled vs. Exhaled Air: Inhaled (~21% oxygen, ~0.04% CO₂); Exhaled (~16-17% oxygen, ~4-5% CO₂).

Lungs: Birds, mammals, reptiles (structure varies).
Gills: Fish (exchange gases with water).
Skin/Gills: Amphibians (e.g., frogs use gills as tadpoles, lungs/skin as adults).
Skin: Earthworms (moist skin for gas exchange).

Digestion varies by animal diet/habitat.
Breathing is physical;
respiration is chemical.
Good practices: Oral hygiene, fiber-rich diet, breathing exercises (e.g., Pranayama).
Smoking: Harms lungs, causes diseases, affects others via passive smoking.