Class 10 Science Notes — Chapter 5: Life Processes
Nutrition, respiration, transport, and excretion in plants and animals.
Detailed NCERT notes
- Life processes = basic functions maintaining life: nutrition, respiration, transportation, excretion, control-coordination, reproduction, growth.
- Autotrophic nutrition: organisms make food from simple inorganic substances (photosynthesis in plants).
- Photosynthesis: 6CO₂ + 6H₂O →(sunlight, chlorophyll) C₆H₁₂O₆ + 6O₂. Occurs in chloroplasts; site = stroma (Calvin cycle) & grana (light reaction).
- Steps of photosynthesis: absorption of light by chlorophyll → conversion to chemical energy → splitting of water (H₂ + O₂) → reduction of CO₂ to carbohydrate.
- Stomata: pores on leaves; open/close via guard cells; control gas exchange and transpiration.
- Heterotrophic nutrition: holozoic (ingesting, e.g., humans, Amoeba), saprophytic (dead matter, e.g., fungi), parasitic (host, e.g., Cuscuta).
- Human digestive system: mouth (saliva has amylase → starch to maltose) → oesophagus → stomach (HCl kills germs, activates pepsin → protein digestion, mucus protects) → small intestine (bile from liver emulsifies fats, pancreatic juice + intestinal juice complete digestion, absorption via villi) → large intestine (water absorption) → rectum (egestion).
- Respiration: breakdown of glucose to release energy (ATP).
- Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP.
- Anaerobic (yeast): glucose → ethanol + CO₂ + 2 ATP.
- Muscles (lack of O₂): glucose → lactic acid + 2 ATP → cramps.
- Human respiratory system: nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli (site of gas exchange, large surface area).
- Transportation in humans: heart (4 chambers), double circulation (pulmonary + systemic), keeps oxygenated & deoxygenated blood separate.
- Blood: plasma + RBCs (carry O₂ via haemoglobin) + WBCs + platelets. Blood vessels: arteries (thick, elastic, no valves), veins (thinner, valves), capillaries (single cell thick, exchange).
- Lymph: colourless, no RBCs; drains excess fluid to blood.
- Transportation in plants: xylem carries water + minerals up (transpiration pull, root pressure); phloem carries food (translocation, needs ATP, both directions).
- Excretion in humans: kidneys → nephrons filter blood (glomerulus + Bowman's capsule + tubule) → reabsorb useful substances → urine to bladder via ureter → out via urethra.
- Excretion in plants: gases via stomata, water via transpiration, waste in vacuoles/old xylem, gum/resin, fallen leaves.
Formulas & key results
- Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
- Anaerobic (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
Mind map
- Nutrition (auto/hetero) → digestion → respiration → transportation → excretion
- Xylem vs phloem
- Nephron & double circulation
Tricks & shortcuts
- Xylem = water (one way, up); Phloem = food (both ways, needs ATP).
- Bile emulsifies fat; pancreatic juice digests all three (carb, protein, fat).
Common mistakes to avoid
- Confusing anaerobic products (lactic acid in muscles vs ethanol in yeast).
- Left vs right heart chambers (left pumps to body, right to lungs).
Competency-based questions & answers
- Q. Why is double circulation necessary in humans?A. Keeps oxygenated and deoxygenated blood separate → efficient O₂ supply → supports high energy demands of warm-blooded animals.
- Q. Why do we get cramps after heavy exercise?A. Insufficient O₂ in muscles → anaerobic respiration → lactic acid accumulates → cramps.
- Q. How is the small intestine designed for absorption?A. Very long, highly folded, lined with villi (finger-like projections) with rich blood supply → huge surface area.