Chapter 6 — Life Processes
Welcome to HSLC Guru! In this article, we present a complete English-medium guide to Class 10 Science Chapter 6 — Life Processes for ASSEB students. You will find a clear chapter summary, all textbook questions and answers, additional MCQs, fill-in-the-blanks, true/false questions, and a glossary table — everything you need to master this chapter and score top marks in your HSLC examination.
Chapter Summary
Life processes are the basic functions performed by living organisms to maintain their life. The essential life processes include nutrition, respiration, transportation, and excretion. Nutrition is the process by which organisms obtain and utilise food. There are two main modes of nutrition — autotrophic (organisms prepare their own food, e.g., green plants) and heterotrophic (organisms depend on others for food). Heterotrophic nutrition is further classified as saprophytic (feeding on dead and decaying matter, e.g., fungi), parasitic (living on or inside a host, e.g., Cuscuta, tapeworm), and holozoic (ingesting solid food, e.g., humans, amoeba).
Photosynthesis is the process by which green plants prepare food using carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen as a by-product. The overall equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. The main events of photosynthesis are absorption of light by chlorophyll, conversion of light energy into chemical energy, splitting of water into hydrogen and oxygen, and reduction of CO₂ to carbohydrates. The human digestive system consists of the alimentary canal (mouth, oesophagus, stomach, small intestine, large intestine, anus) and associated glands (salivary glands, liver, pancreas). Digestion begins in the mouth with saliva (containing salivary amylase), continues in the stomach with gastric juices (HCl, pepsin), and is completed in the small intestine with bile, pancreatic juice, and intestinal juice. Absorption occurs mainly in the small intestine through finger-like projections called villi.
Respiration is the process of breaking down food to release energy in the form of ATP. Aerobic respiration takes place in the presence of oxygen, producing CO₂, water, and large amounts of energy (e.g., in most plants and animals). Anaerobic respiration occurs in the absence of oxygen, producing lactic acid (in muscles) or ethanol and CO₂ (in yeast) with less energy. In humans, breathing involves the nostrils, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli, where gaseous exchange occurs. Transportation in humans is carried out by the circulatory system consisting of blood, blood vessels, and the heart. Blood has plasma, RBCs, WBCs, and platelets. The human heart has four chambers (two atria and two ventricles) and shows double circulation — pulmonary (heart-lungs-heart) and systemic (heart-body-heart) — which keeps oxygenated and deoxygenated blood separate.
In plants, water and minerals are transported through xylem (root → stem → leaves) by the pulling force of transpiration, while food prepared in leaves is transported through phloem by translocation. Excretion is the removal of harmful metabolic waste from the body. The human excretory system consists of two kidneys, two ureters, urinary bladder, and urethra. Each kidney contains around one million filtration units called nephrons. Urine formation involves filtration in the glomerulus, selective reabsorption in the tubule, and secretion. When kidneys fail, an artificial filtration method called dialysis is used. Plants excrete waste products through stomata (gaseous waste), by storing wastes in vacuoles, leaves, bark, or as resins, gums, and latex.
Textbook Questions and Answers
1-Mark Questions
Q1. Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like humans?
Answer: Multicellular organisms have many cells located deep inside the body which are not in direct contact with the environment. Diffusion is too slow to supply oxygen to all such cells, so a specialised transport system is needed.
Q2. What are the criteria used to decide whether something is alive?
Answer: Visible movement, growth, respiration, nutrition, and the presence of life processes that maintain molecular structure are used to decide whether something is alive.
Q3. What are outside raw materials used by an organism?
Answer: The outside raw materials used by an organism are food, water, and oxygen (and carbon dioxide for autotrophs).
Q4. What processes would you consider essential for maintaining life?
Answer: Nutrition, respiration, transportation, and excretion are essential life processes for maintaining life.
Q5. What is the role of saliva in the digestion of food?
Answer: Saliva moistens food for easy swallowing and contains salivary amylase that breaks down starch into sugar (maltose).
Q6. What are the necessary conditions for autotrophic nutrition?
Answer: Carbon dioxide, water, sunlight, and chlorophyll are the necessary conditions for autotrophic nutrition.
Q7. Name the structural and functional unit of the kidney.
Answer: The nephron is the structural and functional unit of the kidney.
Q8. What is the role of the acid in our stomach?
Answer: Hydrochloric acid (HCl) creates an acidic medium that activates pepsin and kills harmful bacteria entering with food.
Q9. Name the green pigment found in leaves.
Answer: Chlorophyll is the green pigment found in leaves.
Q10. What is translocation in plants?
Answer: The transport of soluble products of photosynthesis from leaves to other parts of the plant through phloem is called translocation.
2 to 3-Mark Questions
Q1. Differentiate between autotrophic and heterotrophic nutrition.
Answer: In autotrophic nutrition, organisms prepare their own food from simple inorganic substances using sunlight and chlorophyll (e.g., green plants). In heterotrophic nutrition, organisms depend on other organisms (plants or animals) for food (e.g., humans, animals, fungi). Autotrophs are producers, while heterotrophs are consumers.
Q2. What are the differences between aerobic and anaerobic respiration?
Answer: Aerobic respiration takes place in the presence of oxygen, completely breaks down glucose into CO₂ and water, and releases a large amount of energy (38 ATP). Anaerobic respiration takes place in the absence of oxygen, partially breaks down glucose into ethanol/lactic acid and CO₂, and releases a small amount of energy (2 ATP).
Q3. How is oxygen and carbon dioxide transported in human beings?
Answer: Oxygen is mostly transported by red blood cells (RBCs) bound to haemoglobin as oxyhaemoglobin from the lungs to the body tissues. Carbon dioxide is more soluble than oxygen and is mostly transported in the dissolved form in the blood plasma from the tissues back to the lungs to be expelled.
Q4. How are fats digested in our bodies? Where does this process take place?
Answer: Fat digestion takes place in the small intestine. Bile from the liver emulsifies large fat globules into smaller ones (a process called emulsification). Then pancreatic and intestinal lipase enzymes break down emulsified fats into fatty acids and glycerol, which are absorbed by intestinal villi.
Q5. What is the role of saliva in the digestion of food? Describe with the help of an experiment.
Answer: Saliva contains the enzyme salivary amylase which breaks down starch into maltose (sugar). Take a small amount of cooked rice, chew it well for some time. Initially it tastes bland, but after chewing it tastes slightly sweet. This is because salivary amylase converts starch in rice into sugar.
Q6. Why is transpiration important for plants?
Answer: Transpiration is important for plants because (i) it helps in the absorption and upward movement of water and minerals from roots to leaves, (ii) it cools the plant, and (iii) it maintains the water balance in plants.
5 to 6-Mark Questions
Q1. Describe the human digestive system with the help of a labelled diagram.
Answer: The human digestive system has two main parts — (a) the alimentary canal and (b) digestive glands.
(i) Mouth — Food is chewed by teeth and mixed with saliva (which contains salivary amylase) to form a bolus.
(ii) Oesophagus — Carries food to the stomach by peristaltic movement.
(iii) Stomach — Gastric glands secrete HCl, pepsin, and mucus. HCl creates an acidic medium, pepsin digests proteins, and mucus protects the stomach lining.
(iv) Small intestine — Site of complete digestion. Bile from the liver emulsifies fats; pancreatic juice contains trypsin, lipase, amylase; intestinal juice completes digestion. Absorption occurs through villi.
(v) Large intestine — Absorbs water; undigested food passes out through the anus.
Q2. Explain the structure and working of the human heart with double circulation.
Answer: The human heart is a four-chambered muscular organ — right atrium, right ventricle, left atrium, and left ventricle. Deoxygenated blood from the body enters the right atrium through the vena cava, passes to the right ventricle, and is pumped to the lungs through the pulmonary artery. In the lungs, blood gets oxygenated and returns to the left atrium through pulmonary veins. From the left atrium it passes to the left ventricle and is pumped to the entire body through the aorta. Thus blood passes twice through the heart in one complete cycle — this is called double circulation. It includes pulmonary circulation (heart → lungs → heart) and systemic circulation (heart → body → heart). Double circulation prevents the mixing of oxygenated and deoxygenated blood and ensures efficient oxygen supply to body tissues.
Q3. Describe the process of urine formation in human kidneys.
Answer: Urine is formed in the nephrons of the kidneys in three steps: (i) Glomerular filtration — Blood enters the glomerulus under high pressure, and water, salts, glucose, urea, and other small molecules are filtered into the Bowman’s capsule, forming filtrate. (ii) Selective reabsorption — As the filtrate passes through the tubule, useful substances such as glucose, amino acids, most water, and salts are reabsorbed into the blood. (iii) Tubular secretion — Extra ions and waste materials are secreted into the tubule. The remaining liquid is urine, which collects in the collecting duct and passes through the ureter to the urinary bladder, and is finally expelled through the urethra.
Q4. Explain photosynthesis. Write its equation and describe its main events.
Answer: Photosynthesis is the process by which green plants prepare food using carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen as a by-product.
Equation: 6CO₂ + 6H₂O → (sunlight, chlorophyll) → C₆H₁₂O₆ + 6O₂
The main events of photosynthesis are: (i) absorption of light energy by chlorophyll; (ii) conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen; (iii) reduction of carbon dioxide to carbohydrates (glucose). The raw materials are CO₂ (from the atmosphere through stomata) and water (absorbed from soil through roots). Sunlight is the source of energy and chlorophyll absorbs it. Photosynthesis takes place in the chloroplasts of leaves.
Q5. Describe transportation in plants — xylem, phloem, and transpiration.
Answer: Plants have two transport tissues — xylem and phloem. Xylem transports water and minerals from roots to all parts of the plant. The transport in xylem is unidirectional (upward) and is driven by transpiration pull. Transpiration is the loss of water vapour from aerial parts of plants, mainly through stomata. As water evaporates from leaves, a suction force is created which pulls water up from the roots through xylem. Phloem transports food (sucrose) from leaves to other parts of the plant — a process called translocation. Phloem transport is bidirectional and requires energy (ATP). Together, xylem and phloem perform the function of transportation in plants.
Additional Multiple Choice Questions (MCQs)
Q1. Which of the following is an autotroph?
(a) Mushroom (b) Green plant (c) Lion (d) Tapeworm
Answer: (b) Green plant
Q2. The site of photosynthesis in a plant cell is —
(a) Mitochondria (b) Ribosome (c) Chloroplast (d) Nucleus
Answer: (c) Chloroplast
Q3. Cuscuta is an example of —
(a) Autotroph (b) Saprophyte (c) Parasite (d) Holozoic
Answer: (c) Parasite
Q4. The opening through which gaseous exchange occurs in leaves is —
(a) Lenticel (b) Stomata (c) Vacuole (d) Vein
Answer: (b) Stomata
Q5. The main excretory organ in human beings is —
(a) Liver (b) Skin (c) Kidney (d) Lungs
Answer: (c) Kidney
Q6. The structural and functional unit of the kidney is —
(a) Neuron (b) Nephron (c) Alveolus (d) Villus
Answer: (b) Nephron
Q7. Which of the following is NOT a digestive enzyme?
(a) Pepsin (b) Trypsin (c) Insulin (d) Lipase
Answer: (c) Insulin
Q8. The fluid in the lymphatic system is called —
(a) Blood (b) Plasma (c) Lymph (d) Serum
Answer: (c) Lymph
Q9. The number of chambers in the human heart is —
(a) Two (b) Three (c) Four (d) Five
Answer: (c) Four
Q10. Anaerobic respiration in yeast produces —
(a) Lactic acid (b) Ethanol and CO₂ (c) Water (d) Glucose
Answer: (b) Ethanol and CO₂
Fill in the Blanks
Q1. ____________ is the green pigment in plants that captures light energy.
Answer: Chlorophyll
Q2. The exchange of gases in human lungs takes place in tiny sacs called ____________.
Answer: Alveoli
Q3. ____________ transports food in plants from leaves to other parts.
Answer: Phloem
Q4. The process of removal of nitrogenous wastes is called ____________.
Answer: Excretion
Q5. The artificial method of filtering blood when the kidneys fail is called ____________.
Answer: Dialysis
True or False
Q1. Photosynthesis releases carbon dioxide as a by-product.
Answer: False (it releases oxygen).
Q2. Aerobic respiration produces more energy than anaerobic respiration.
Answer: True
Q3. Xylem transports food in plants.
Answer: False (xylem transports water and minerals; phloem transports food).
Q4. The human heart has four chambers.
Answer: True
Q5. Bile contains digestive enzymes.
Answer: False (bile contains no enzymes; it only emulsifies fats).
Glossary
| Term | Meaning |
|---|---|
| Life Processes | Basic functions performed by living organisms to maintain life. |
| Nutrition | The process of taking and utilising food for energy and growth. |
| Autotrophic Nutrition | Mode of nutrition in which organisms make their own food (e.g., plants). |
| Heterotrophic Nutrition | Mode of nutrition in which organisms depend on others for food. |
| Saprophytic | Feeding on dead and decaying matter (e.g., fungi). |
| Parasitic | Living on or in a host and deriving nutrition from it. |
| Holozoic | Ingestion of solid food (e.g., humans, amoeba). |
| Photosynthesis | Process of food preparation by green plants using CO₂, water, sunlight, and chlorophyll. |
| Chlorophyll | Green pigment in plants that absorbs light energy. |
| Stomata | Tiny pores on leaf surface for gaseous exchange and transpiration. |
| Respiration | Breakdown of food in cells to release energy as ATP. |
| Aerobic Respiration | Respiration in the presence of oxygen, producing CO₂, water, and energy. |
| Anaerobic Respiration | Respiration without oxygen, producing lactic acid or ethanol with less energy. |
| Alveoli | Tiny air sacs in lungs where gas exchange occurs. |
| Haemoglobin | Iron-rich pigment in RBCs that carries oxygen. |
| Double Circulation | Blood passing twice through the heart in one complete cycle. |
| Xylem | Plant tissue that transports water and minerals from roots to leaves. |
| Phloem | Plant tissue that transports food from leaves to other parts. |
| Transpiration | Loss of water vapour from aerial parts of plants. |
| Translocation | Movement of food in phloem from leaves to other parts of the plant. |
| Excretion | Removal of metabolic wastes from the body. |
| Nephron | Structural and functional unit of the kidney. |
| Glomerulus | Cluster of capillaries inside Bowman’s capsule where blood is filtered. |
| Dialysis | Artificial method of filtering blood when kidneys fail. |
| Bile | Greenish-yellow fluid from the liver that emulsifies fats. |
| Villi | Finger-like projections in small intestine that absorb digested food. |