Life Processes in Animals

Key Concepts

Animals obtain energy from food containing complex components (carbohydrates, proteins, fats).

Digestion: The process of breaking down complex food components into simpler forms.
Human Digestive System:
- Alimentary Canal: Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus.
- Mouth: Mechanical digestion (chewing) and chemical digestion (saliva breaks starch into sugar).
- Stomach: Churns food; secretes acid (kills bacteria) and digestive juices (breaks proteins). Mucus protects the stomach wall.
- Small Intestine: ~6 metres long. Receives bile (from liver, neutralizes acid/digests fats) and pancreatic juice (from pancreas). Digested nutrients are absorbed by finger-like villi.
- Large Intestine: ~1.5 metres long. Absorbs water and salts. Waste stored in rectum and expelled via anus (egestion).

Ruminants (e.g., Cows): Swallow grass partially chewed into the rumen. Food is later brought back to the mouth as cud for thorough chewing (rumination).
Birds: Have a gizzard where food is crushed with the help of swallowed grit (small stones).

The process of breaking down nutrients (like glucose) to release energy.

Breathing vs. Respiration:
- Breathing: Physical process of inhaling (O2 rich air) and exhaling (CO2 rich air).
- Respiration: Chemical process inside cells: Glucose + Oxygen → Carbon dioxide + Water + Energy.
Human Respiratory System:
- Pathway: Nostrils → Nasal passage (hair/mucus trap dust) → Windpipe (trachea) → Lungs → Alveoli (balloon-like sacs where gas exchange occurs).
Mechanism of Breathing:
- Inhalation: Ribs move out, diaphragm moves down, increasing space; air enters.
- Exhalation: Ribs move back, diaphragm moves up, decreasing space; air is forced out.

Includes the heart, blood, and blood vessels. Transports nutrients and oxygen to all body parts and removes waste.

Note on Smoking: Extremely harmful; damages lungs and causes respiratory illnesses. Affects others via passive smoking.