In short: Life Processes is the highest-scoring chapter in CBSE Class 10 Biology, carrying 10-12 marks. It covers four life processes — nutrition, respiration, transportation, and excretion. Diagram-based questions (human heart, nephron, human digestive system, stomata) appear every year. Master the diagrams, learn the differences tables, and know the key equations like photosynthesis and aerobic respiration.
Life Processes is the biggest chapter in CBSE Class 10 Science — both in content and in marks. It covers everything that keeps living organisms alive: how they get food, how they break it down for energy, how they transport materials, and how they remove waste. This chapter alone can carry 10-12 marks in the board exam, and it rewards students who combine diagram practice with clear conceptual understanding.
This guide covers every sub-topic in detail with diagram descriptions, comparison tables, and exam-focused tips. For marks distribution, see the CBSE Class 10 Science chapter-wise marks weightage.
What Are Life Processes?
Life processes are the basic functions that every living organism performs to sustain life. The key life processes are:
- Nutrition — obtaining and utilizing food for energy and growth
- Respiration — breaking down food to release energy
- Transportation — carrying materials (nutrients, oxygen, waste) within the body
- Excretion — removing metabolic waste from the body
Other life processes include growth, movement, and reproduction (covered in a separate chapter).
Nutrition
Nutrition is the process of taking in food, breaking it down, and using it for energy, growth, and repair.
Autotrophic Nutrition
Autotrophs (like green plants) make their own food through photosynthesis.
Photosynthesis equation:
6CO₂ + 6H₂O → (sunlight, chlorophyll) → C₆H₁₂O₆ + 6O₂
Requirements: Carbon dioxide, water, sunlight, and chlorophyll.
Steps of photosynthesis:
- Absorption of light energy by chlorophyll in the leaves.
- Conversion of light energy to chemical energy, and splitting of water molecules into hydrogen and oxygen (photolysis).
- Reduction of carbon dioxide to carbohydrates using the hydrogen from water splitting.
Diagram: Stomata (cross-section of a leaf)
The stomatal apparatus consists of two kidney-shaped guard cells surrounding a pore called the stoma. The guard cells have chloroplasts and a thick inner wall. When guard cells swell with water, the stoma opens (allowing CO₂ in and O₂ out). When guard cells lose water, the stoma closes. The surrounding epidermal cells do not have chloroplasts.
Board Exam Tip: Draw a neat, labeled diagram of the stomatal apparatus. Label: guard cells, stoma (pore), epidermal cells, chloroplast, cell wall. This diagram is asked almost every year for 2-3 marks.
How raw materials are obtained:
- CO₂ enters through stomata on the leaf surface.
- Water is absorbed by roots from the soil and transported through xylem.
- Sunlight is captured by chlorophyll in mesophyll cells.
Heterotrophic Nutrition
Organisms that cannot make their own food depend on others. Types include:
| Type | Description | Examples |
|---|---|---|
| Saprophytic | Feeds on dead, decaying organic matter | Fungi, some bacteria |
| Parasitic | Feeds on a living host, causing harm | Cuscuta, tapeworm, lice |
| Holozoic | Ingests whole food, digests internally | Amoeba, humans |
Human Digestive System
The human digestive system consists of the alimentary canal and associated digestive glands.
Diagram: Human Digestive System
The diagram shows the complete alimentary canal from mouth to anus. Key organs to label: mouth (with teeth, tongue, salivary glands), oesophagus (food pipe), stomach, small intestine (duodenum, jejunum, ileum), large intestine, rectum, and anus. Associated glands: salivary glands, liver (producing bile, stored in gall bladder), and pancreas (secreting pancreatic juice into duodenum).
Step-by-step digestion:
| Organ | Secretion | Action |
|---|---|---|
| Mouth | Salivary amylase | Breaks down starch into maltose |
| Stomach | HCl + Pepsin | HCl kills bacteria, creates acidic medium; pepsin breaks proteins into peptones |
| Small intestine (duodenum) | Bile + Pancreatic juice | Bile emulsifies fats; pancreatic enzymes (trypsin, lipase, amylase) act on proteins, fats, carbohydrates |
| Small intestine (ileum) | Intestinal juice | Final digestion; villi absorb nutrients into blood |
| Large intestine | — | Absorbs water and electrolytes; forms faeces |
Absorption: The inner wall of the small intestine has millions of finger-like projections called villi. Villi increase the surface area for absorption. Each villus has a network of blood capillaries for absorbing nutrients into the bloodstream.
Board Exam Tip: "What is the role of HCl in the stomach?" and "What is the function of villi in the small intestine?" are very common 2-mark questions.
Nutrition in Amoeba
Amoeba feeds by holozoic nutrition through a process involving five steps: ingestion (engulfing food using pseudopodia to form a food vacuole), digestion (enzymes break down food inside the vacuole), absorption (digested food is absorbed into cytoplasm), assimilation (food is used for energy and growth), and egestion (undigested food is expelled by the vacuole reaching the cell surface).
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Respiration
Respiration is the process of breaking down glucose to release energy in the form of ATP (adenosine triphosphate).
Aerobic Respiration
Occurs in the presence of oxygen, in the mitochondria of cells.
Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)
Produces a large amount of energy (38 ATP molecules per glucose molecule).
Anaerobic Respiration
Occurs in the absence of oxygen.
In yeast (fermentation):
C₆H₁₂O₆ → 2C₂H₅OH (ethanol) + 2CO₂ + Energy
In muscles (during vigorous exercise):
Glucose → Lactic acid + Energy
This is why muscles cramp after intense exercise — lactic acid builds up.
Aerobic vs Anaerobic Respiration
| Feature | Aerobic | Anaerobic |
|---|---|---|
| Oxygen | Required | Not required |
| End products | CO₂ + H₂O | Ethanol + CO₂ (yeast) or Lactic acid (muscles) |
| Energy released | Large amount (38 ATP) | Small amount (2 ATP) |
| Where it occurs | Mitochondria | Cytoplasm |
| Complete breakdown | Yes | No (partial) |
Human Respiratory System
Air enters through nostrils, passes through the nasal cavity (where it is filtered, warmed, and moistened), then through the pharynx, larynx, trachea, bronchi, and finally into the bronchioles in the lungs. The bronchioles end in tiny air sacs called alveoli.
Alveoli are the functional units of the lungs. They provide a massive surface area for gas exchange. The walls of alveoli are one cell thick and surrounded by blood capillaries. Oxygen diffuses from alveoli into blood, and CO₂ diffuses from blood into alveoli.
Mechanism of breathing:
- Inhalation: Diaphragm contracts and flattens, ribs move upward and outward, chest cavity expands, air rushes in.
- Exhalation: Diaphragm relaxes and moves upward, ribs move downward and inward, chest cavity reduces, air is pushed out.
Transportation
Transportation in Humans — The Circulatory System
The human circulatory system consists of the heart, blood vessels (arteries, veins, capillaries), and blood.
Blood components:
| Component | Function |
|---|---|
| Plasma | Liquid part (55%); transports food, CO₂, nitrogenous waste |
| Red blood cells (RBC) | Contain haemoglobin; transport oxygen |
| White blood cells (WBC) | Fight infections; part of the immune system |
| Platelets | Help in blood clotting at wound sites |
Human Heart — Structure and Function
Diagram: Human Heart (longitudinal section)
The heart has four chambers: right atrium (RA), right ventricle (RV), left atrium (LA), and left ventricle (LV). The right side receives deoxygenated blood and sends it to the lungs. The left side receives oxygenated blood from the lungs and pumps it to the body.
Key structures to label: superior vena cava, inferior vena cava (bring deoxygenated blood to RA), pulmonary artery (carries deoxygenated blood from RV to lungs), pulmonary veins (carry oxygenated blood from lungs to LA), aorta (carries oxygenated blood from LV to body), septum (wall separating left and right sides), tricuspid valve (between RA and RV), bicuspid/mitral valve (between LA and LV).
Board Exam Tip: The heart diagram is one of the most important diagrams in all of Class 10 Science. Label at least 8 parts clearly: four chambers, aorta, vena cava, pulmonary artery, and pulmonary veins.
Double Circulation
Humans have double circulation — blood passes through the heart twice in one complete cycle.
- Pulmonary circulation: Right ventricle → Pulmonary artery → Lungs (CO₂ released, O₂ absorbed) → Pulmonary veins → Left atrium.
- Systemic circulation: Left ventricle → Aorta → Body organs (O₂ delivered, CO₂ collected) → Vena cava → Right atrium.
Double circulation ensures that oxygenated and deoxygenated blood do not mix, maintaining efficient oxygen supply — essential for warm-blooded animals that need a lot of energy.
Arteries vs Veins
| Feature | Arteries | Veins |
|---|---|---|
| Carry | Oxygenated blood (exception: pulmonary artery) | Deoxygenated blood (exception: pulmonary vein) |
| Direction | Away from heart | Toward heart |
| Walls | Thick, elastic | Thin, less elastic |
| Valves | No valves | Have valves to prevent backflow |
| Blood pressure | High | Low |
| Position | Deep inside body | Near the surface |
Transportation in Plants
Plants have two transport systems — xylem and phloem.
Xylem: Transports water and dissolved minerals upward from roots to leaves. The transport is unidirectional. Xylem consists of tracheids and vessels (both are dead cells). Water moves upward due to transpiration pull — as water evaporates from leaves (transpiration), it creates a suction that pulls water upward through the xylem.
Phloem: Transports food (sucrose, amino acids) from leaves to other parts of the plant. The transport is bidirectional. Phloem consists of sieve tubes and companion cells (living cells). Food is transported by translocation, which uses energy from ATP.
Xylem vs Phloem
| Feature | Xylem | Phloem |
|---|---|---|
| Transports | Water and minerals | Food (sucrose) |
| Direction | Upward (unidirectional) | Bidirectional |
| Cell type | Dead cells (tracheids, vessels) | Living cells (sieve tubes, companion cells) |
| Driving force | Transpiration pull | ATP energy (active process) |
Excretion
Excretion is the removal of harmful metabolic waste products from the body.
Human Excretory System
The excretory system consists of two kidneys, two ureters, a urinary bladder, and a urethra.
Kidneys are bean-shaped organs located on either side of the spine. Each kidney contains about one million filtration units called nephrons.
Diagram: Nephron (functional unit of the kidney)
A nephron consists of: Bowman's capsule (cup-shaped structure surrounding a cluster of capillaries called the glomerulus), proximal convoluted tubule, loop of Henle (U-shaped), distal convoluted tubule, and collecting duct. The renal artery brings blood to the glomerulus, and the renal vein takes filtered blood away.
Urine Formation — Three Steps
| Step | Where | What Happens |
|---|---|---|
| Glomerular filtration | Bowman's capsule | Blood is filtered under pressure; glucose, amino acids, salts, water, and urea pass into Bowman's capsule |
| Selective reabsorption | Proximal tubule, Loop of Henle | Useful substances (glucose, amino acids, salts, most water) are reabsorbed back into blood |
| Tubular secretion | Distal tubule | Additional waste (K⁺ ions, H⁺ ions) is secreted into the tubule |
The remaining liquid is urine, which flows through the collecting duct → renal pelvis → ureter → urinary bladder → urethra.
Board Exam Tip: "Describe the process of urine formation" is a very common 3-mark or 5-mark question. Structure your answer in three steps: filtration, reabsorption, and secretion. Drawing a labeled nephron diagram adds value.
Excretion in Plants
Plants do not have a dedicated excretory system. They use several strategies:
- Excess water is removed by transpiration through stomata.
- Waste products are stored in leaves, which eventually fall off.
- Resins and gums are stored in old xylem.
- Some waste is released into the soil through roots.
Tips for Scoring Full Marks in Life Processes
Practice all diagrams regularly — human heart, nephron, digestive system, stomata, and the structure of alveoli. For descriptive questions, use headings and numbered points rather than long paragraphs. For differences (arteries vs veins, xylem vs phloem, aerobic vs anaerobic), learn them in table format and reproduce them as tables in the exam. Know the key equations: photosynthesis and respiration (both aerobic and anaerobic).
For more diagram practice strategies across chapters, see the CBSE Class 12 Biology diagrams complete list — many concepts from Class 10 extend into Class 12.
Frequently Asked Questions
How many marks does Life Processes carry in CBSE Class 10?
Life Processes typically carries 10 to 12 marks, making it the highest-scoring single chapter in Class 10 Science. Questions include diagram-based questions (heart, nephron, digestive system), differences tables, process descriptions, and 1-mark MCQs. Thorough preparation of this one chapter can significantly boost your Science score.
Which diagrams are most important from Life Processes?
The five most important diagrams are: (1) Human heart showing all four chambers and major vessels, (2) Nephron showing Bowman's capsule, glomerulus, tubules, and collecting duct, (3) Human digestive system, (4) Stomatal apparatus showing guard cells, and (5) Structure of alveoli. The heart and nephron diagrams appear most frequently in board exams.
What is double circulation and why is it important?
Double circulation means blood passes through the heart twice in one complete cycle — once through the pulmonary circuit (heart to lungs and back) and once through the systemic circuit (heart to body and back). It ensures that oxygenated and deoxygenated blood remain completely separated, which allows efficient oxygen delivery. This is critical for warm-blooded animals like humans who need a constant, high level of energy.
How should I answer the "describe the process of digestion in humans" question?
Structure your answer organ by organ: start with the mouth (salivary amylase breaks starch into maltose), then the stomach (HCl and pepsin break down proteins), then the small intestine (bile emulsifies fats, pancreatic and intestinal enzymes complete digestion, villi absorb nutrients), and finally the large intestine (water absorption, faeces formation). Using this step-by-step approach with specific enzyme names earns full marks.
What is the difference between respiration and breathing?
Breathing is the physical process of inhaling and exhaling air — it involves the lungs, diaphragm, and ribcage. Respiration is the chemical process of breaking down glucose to release energy — it happens inside cells (specifically mitochondria for aerobic respiration). Breathing provides oxygen for respiration and removes the CO₂ produced by it. This distinction is a commonly asked 2-mark question.
Why do plants not need a dedicated excretory system?
Plants have a much lower metabolic rate than animals, so they produce less waste. They handle waste through several passive mechanisms: excess water is lost through transpiration, waste products are stored in vacuoles or in leaves that eventually fall off, and some waste (like resins and gums) is stored in dead tissue like old xylem. Oxygen (a by-product of photosynthesis) is actually useful and is released through stomata.
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