Parasitic Nutrition: Organisms (parasites) live on or inside another living organism (host) and derive nutrition from it, often harming the host. (e.g., Cuscuta (dodder plant), ticks, lice, tapeworms, Plasmodium).

2.2 Nutrition in Amoeba (Holozoic) (NCERT Page 96, Fig 6.4)

Process: Phagocytosis (cell eating).
Steps:
1. Ingestion: Amoeba extends temporary finger-like projections called pseudopodia to engulf the food particle, forming a food cup.
2. Formation of Food Vacuole: The food particle, along with a small amount of water, is enclosed within a food vacuole.
3. Digestion: Lysosomes containing digestive enzymes fuse with the food vacuole and break down complex food substances into simpler ones.
4. Absorption: The digested food diffuses from the food vacuole into the cytoplasm.
5. Assimilation: The absorbed food is used for energy, growth, and repair.
6. Egestion: The undigested waste material is expelled out of the cell by rupturing the cell membrane at any point.

2.3 Nutrition in Humans (NCERT Page 97-100, Fig 6.6)

Human Digestive System: Consists of the alimentary canal and associated digestive glands.
Alimentary Canal (approx. 9m long):
1. Mouth:
  - Ingestion: Food taken in.
  - Mechanical Digestion: Chewing (mastication) by teeth.
  - Chemical Digestion: Saliva (from salivary glands) contains salivary amylase (ptyalin) which breaks down complex starch into simpler sugars (maltose). Mucus lubricates food.
2. Pharynx: Common passage for food and air.
3. Oesophagus (Food Pipe): Connects pharynx to stomach. Food moves by peristalsis (rhythmic contraction and relaxation of muscular walls).
4. Stomach: J-shaped muscular organ.
  - Gastric Glands: Secrete gastric juice containing:
    - Hydrochloric Acid (HCl): Kills bacteria, provides acidic medium ($pH \approx 1.5-3.5$) for pepsin, denatures proteins.
    - Pepsin: Enzyme that begins protein digestion (breaks proteins into peptones and proteoses).
    - Mucus: Protects the stomach lining from the corrosive action of HCl.
  - Food churned for several hours, forming a semi-digested paste called chyme.
5. Small Intestine: Longest part (approx. 6.5m), highly coiled. Site of complete digestion and absorption.
  - Sphincter Muscles: Pyloric sphincter controls release of chyme into small intestine.
  - Receives secretions from:
    - Liver: Produces bile (stored in gallbladder). Bile emulsifies fats (breaks large fat globules into smaller ones), making them accessible for lipase. It also provides an alkaline medium.
    - Pancreas: Produces pancreatic juice containing:
      - Pancreatic Amylase: Continues starch digestion.
      - Trypsin: Digests proteins.
      - Lipase: Digests emulsified fats.
  - Intestinal Glands: Secrete intestinal juice (succus entericus) containing enzymes that complete digestion:
    - Maltase, Sucrase, Lactase: B