Life processes Animated class10 Biology Class 10 Science Chapter 6 CBSE NUTRITION IN PLANTS

Life Processes: Nutrition, Respiration, Transport, and Excretion

All living organisms perform certain basic functions that distinguish them from non-living matter. These life processes — nutrition, respiration, transportation, and excretion — are essential for maintaining life, growth, and reproduction. This chapter in CBSE Class 10 Science explores each of these processes in detail, comparing how they occur in plants and animals, and connecting them to the structures and organs specialised for each function.

Nutrition is the process by which organisms obtain and utilise food for energy and growth. Autotrophic nutrition (performed by green plants) involves photosynthesis — plants use sunlight, carbon dioxide, and water to produce glucose and oxygen: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. This occurs in chloroplasts where chlorophyll captures light energy. Heterotrophic nutrition involves obtaining food from other organisms. In humans, the digestive system breaks down complex food into absorbable units: the mouth (mechanical digestion by teeth, chemical by salivary amylase), the oesophagus (peristalsis moves food), the stomach (gastric juice with HCl, pepsin, and mucus), the small intestine (bile from the liver emulsifies fats, pancreatic juice with trypsin and lipase, and intestinal juice completes digestion), and the large intestine (absorbs water). The villi in the small intestine increase the surface area for absorption. Respiration is the biochemical process that releases energy from food. Cellular respiration occurs in mitochondria: aerobic respiration (with oxygen) breaks glucose down completely to CO₂ and H₂O, releasing 38 ATP molecules per glucose molecule (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy). Anaerobic respiration in yeast produces ethanol and CO₂ (fermentation, used in brewing and baking), while in human muscle cells during intense exercise it produces lactic acid, causing cramps.

Transportation moves nutrients, gases, hormones, and waste products throughout the body. In humans, the circulatory system consists of the heart (a muscular pump with four chambers — two atria and two ventricles), blood vessels (arteries carry blood away from the heart, veins return it, and capillaries enable exchange with tissues), and blood (red blood cells carry oxygen via haemoglobin, white blood cells fight infection, platelets help in clotting, and plasma transports dissolved substances). The heart follows a double circulation pattern: pulmonary circulation (heart → lungs → heart) oxygenates blood, and systemic circulation (heart → body → heart) delivers oxygen to tissues. In plants, transportation occurs through two types of vascular tissue: xylem transports water and dissolved minerals upward from roots to leaves (driven by root pressure and transpiration pull), and phloem transports synthesised organic nutrients (sucrose) from leaves to all other parts of the plant — this is called translocation. Excretion is the removal of metabolic waste from the body. The human excretory system consists of a pair of kidneys (each containing about one million nephrons — the functional filtering units), ureters (tubes carrying urine from kidneys to the bladder), the urinary bladder (stores urine), and the urethra (releases urine). Each nephron filters blood in the glomerulus (a knot of capillaries inside Bowman's capsule), reabsorbs useful substances (glucose, amino acids, water, salts) in the tubule, and secretes additional waste into the filtrate. The final urine contains urea, excess salts, and water. Plants excrete through stomata (gaseous wastes), lenticels, and by storing waste in leaves that are later shed.

• Nutrition: autotrophic (photosynthesis in plants) and heterotrophic (digestion in humans — mouth to small intestine with enzyme action at each stage).
• Respiration: aerobic (glucose + O₂ → CO₂ + H₂O + 38 ATP) and anaerobic (fermentation in yeast or lactic acid in muscles).
• Transport: human circulatory system (heart, blood vessels, blood with double circulation) and plant vascular tissue (xylem for water, phloem for food).
• Excretion: nephrons in kidneys filter blood, reabsorb useful substances, and produce urine; plants excrete via stomata and leaf shedding.
• Each life process is supported by specialised structures — chloroplasts for photosynthesis, mitochondria for respiration, xylem/phloem for transport, and nephrons for excretion.