Life Processes Class 10: Nutrition, Respiration, Transport, Excretion

What Life Processes is about

Weightage: This chapter is part of Unit II, World of Living, which carries 25 of the 80 theory marks together with Control and Coordination, How do Organisms Reproduce? and Heredity.Source: CBSE Science syllabus 2026-27, Unit II World of Living

In real board papers: asked in 21 of the 21 board papers we hold (2023 to 2026), on average 8.4 marks per paper. See the questions

Key concepts

Life Processes and Why They Are Needed

NCERT section 5.1 What are Life Processes?

Movement you can see is not a good enough test of life. A sleeping dog or a plant that is not visibly growing is still alive. Biologists say the real sign is molecular movement inside the body. Why is it needed? Living things are highly organised: cells make tissues, tissues make organs. The environment keeps breaking this order down, so the body must keep repairing itself, and repair means moving molecules all the time.

The processes that do this maintenance job, even while you sleep, are life processes. Repair needs energy, and that energy comes from outside as food, so you need nutrition. Food must then be broken down, often using oxygen, which is respiration.

A single cell touches its surroundings on all sides, so diffusion is enough. In a large multicellular body, most cells are far from the surface and diffusion is too slow. So food and oxygen are taken in by specialised tissues at one place, and a transport system must carry them everywhere. Harmful by-products must be removed by excretion.

Worked example

An Amoeba has no gut, lungs or kidneys, but a human needs all of these and a heart too. Explain why, using the idea of diffusion. Also explain why a person needs energy even while asleep. (3 marks)

Try it first, then show the solutionSolution

1. In a single-celled organism the entire surface is in contact with the environment, so food, gases and wastes can move by diffusion. (½)
2. In a multicellular human most cells are not in direct contact with the surroundings, so simple diffusion cannot meet the needs of all cells. (1)
3. Food and oxygen are taken in by specialised tissues at one place, so a transport system (heart, blood, vessels) is needed to carry them to all cells, and to carry wastes to a specialised excretory tissue. (1)
4. Even during sleep the ordered body structures keep breaking down and must be repaired; this maintenance needs energy, which comes from food. (½)

Answer: Diffusion works only when every cell touches the surroundings. In a large body it is too slow, so specialised organs for intake and excretion and a transport system are needed. Energy is needed during sleep because maintenance and repair of body structures never stop.

Autotrophic Nutrition and Photosynthesis

NCERT section 5.2.1 Autotrophic Nutrition

Autotrophs (green plants and some bacteria) make their own food from simple inorganic substances: carbon dioxide and water. They do this by photosynthesis, which needs sunlight and chlorophyll and gives carbohydrates and oxygen. Carbohydrates not used at once are stored as starch, the plant's energy reserve (we store energy as glycogen).

Three events happen: (i) chlorophyll absorbs light energy; (ii) light energy becomes chemical energy and water splits into hydrogen and oxygen; (iii) carbon dioxide is reduced to carbohydrates. These need not happen one right after another. Desert plants take in carbon dioxide at night, make an intermediate, and use light energy on it during the day.

Chlorophyll sits in chloroplasts. Carbon dioxide enters mainly through stomata. Guard cells swell when water flows in, opening the pore; they shrink to close it. The plant closes stomata when it does not need carbon dioxide, to save water. Roots take water and minerals such as nitrogen (as nitrates or nitrites), phosphorus, iron and magnesium from the soil.

Worked example

Two similar potted plants are kept in the dark for three days. Each is then placed under a bell-jar sealed with vaseline on a glass plate. A watch-glass of potassium hydroxide is placed beside plant X only. Both are kept in sunlight for two hours, and a leaf from each is tested with iodine. (a) Why were the plants kept in the dark first? (b) Predict the colour of each leaf. (c) What does the activity prove, and why was vaseline used? (3 marks)

Try it first, then show the solutionSolution

1. (a) Keeping the plants in the dark uses up all the stored starch, so any starch found later must have been made during the experiment. (1)
2. (b) The leaf of plant X (with potassium hydroxide) shows little or no blue-black colour; the leaf of plant Y (without potassium hydroxide) turns blue-black, showing starch. (1)
3. (c) Potassium hydroxide absorbs carbon dioxide, so plant X could not make starch: carbon dioxide is essential for photosynthesis. Vaseline makes the set-up air-tight so no outside carbon dioxide can enter. (1)

Answer: Destarching removes old starch; leaf X shows little or no starch, leaf Y turns blue-black; carbon dioxide is essential for photosynthesis, and vaseline keeps the jar air-tight.

Heterotrophic Nutrition and How Organisms Obtain Food

NCERT section 5.2.3 How do Organisms obtain their Nutrition?

Heterotrophs (animals and fungi) cannot use carbon dioxide and water. They take in complex substances made by other organisms and break them down with enzymes. So, directly or indirectly, they depend on autotrophs.

The way an organism feeds depends on its food and surroundings. Grass stays still and a deer runs, so a cow and a lion have very different feeding apparatus. There are three strategies in the text:

• Break food down outside the body and then absorb it: bread mould, yeast, mushrooms.
• Take in whole food and break it down inside: most animals.
• Parasites take food from a living host without killing it: cuscuta (amar-bel), ticks, lice, leeches, tapeworms.

In single cells, food can enter through the surface. Amoeba pushes out temporary finger-like extensions that fuse around a food particle, forming a food vacuole. Food is digested inside it, the simple substances diffuse into the cytoplasm, and waste is thrown out at the surface. Paramoecium has a definite shape, so food enters at one specific spot, moved there by cilia covering the cell.

Worked example

(a) Name one organism that digests its food outside its body and one parasite that takes food from a plant. (b) Explain how food is taken in and digested in Amoeba, and how Paramoecium differs. (3 marks)

Try it first, then show the solutionSolution

1. (a) Outside the body: bread mould, yeast or mushroom (any one). (½)
2. (a) Plant parasite: cuscuta (amar-bel). (½)
3. (b) Amoeba forms temporary finger-like extensions that fuse over the food particle to make a food vacuole; complex substances are broken down inside it and diffuse into the cytoplasm; undigested matter is moved to the surface and thrown out. (1)
4. (b) Paramoecium has a definite shape, so food is taken in only at a specific spot; cilia covering the whole surface move the food to this spot. (1)

Answer: (a) Bread mould (or yeast or mushroom); cuscuta. (b) Amoeba engulfs food anywhere using temporary extensions and digests it in a food vacuole; Paramoecium takes food in at one fixed spot, swept there by cilia.

Nutrition in Human Beings

NCERT section 5.2.4 Nutrition in Human Beings

The alimentary canal is a long tube from mouth to anus, with each region doing a different job. Food is moved along by peristalsis, rhythmic contraction of muscles in the wall.

• Mouth: teeth crush food; saliva wets it; salivary amylase breaks starch into simple sugar; the tongue mixes it.
• Oesophagus: carries food to the stomach.
• Stomach: gastric glands release hydrochloric acid (makes the medium acidic so pepsin can digest proteins), pepsin and mucus (protects the lining from the acid). A sphincter lets food into the small intestine in small amounts.
• Small intestine: longest part; complete digestion of carbohydrates, proteins and fats. Bile from the liver makes the acidic food alkaline for pancreatic enzymes and breaks fat into small globules. Pancreatic juice has trypsin (proteins) and lipase (emulsified fats). Intestinal juice finishes the job: proteins to amino acids, carbohydrates to glucose, fats to fatty acids and glycerol. Villi increase the surface for absorption and carry food into blood.
• Large intestine: absorbs water; waste leaves through the anus, controlled by the anal sphincter.

Herbivores have a longer small intestine to digest cellulose; carnivores like tigers have a shorter one.

Worked example

A student eats chapati (mostly starch), dal (protein) and ghee (fat). Trace the digestion of each component through the alimentary canal, naming the enzymes, the role of bile and acid, the end products and how they are absorbed. (5 marks)

Try it first, then show the solutionSolution

1. Mouth: salivary amylase in saliva breaks starch into simple sugar while the tongue mixes the food. (1)
2. Stomach: gastric glands release HCl, which makes the medium acidic for pepsin; pepsin begins protein digestion; mucus protects the stomach lining from the acid. (1)
3. Small intestine: bile from the liver makes the acidic food alkaline so pancreatic enzymes can act, and bile salts break large fat globules into smaller ones. (1)
4. Pancreatic juice: trypsin digests proteins, lipase breaks down emulsified fats; intestinal juice finally converts proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol. (1)
5. Villi of the small intestine increase the surface area and, being rich in blood vessels, absorb the digested food; the large intestine absorbs water and the waste leaves via the anus. (1)

Answer: Starch: amylase in the mouth, finished to glucose in the small intestine. Protein: pepsin in the stomach, trypsin and intestinal juice to amino acids. Fat: emulsified by bile, digested by lipase to fatty acids and glycerol. All are absorbed by villi.

Respiration: Breakdown of Glucose

NCERT section 5.3 Respiration

Respiration releases energy from food inside cells. In every organism, the first step is the same: glucose (6-carbon) is broken into pyruvate (3-carbon) in the cytoplasm. What happens to pyruvate depends on oxygen:

• Anaerobic (yeast, fermentation): no oxygen; pyruvate becomes ethanol and carbon dioxide.
• Aerobic: with oxygen, in the mitochondria; pyruvate gives carbon dioxide and water. This releases a lot more energy than the anaerobic route.
• Lack of oxygen in muscle: during sudden activity, pyruvate becomes lactic acid (also 3-carbon). Its build-up causes cramps.

The energy released is used at once to make ATP, which powers other activities in the cell. When ATP is broken down it gives a fixed amount of energy for endothermic reactions.

Why does aerobic respiration need good oxygen supply? Because it depends on oxygen, aerobic organisms must take in enough of it. That is why breathing organs and transport systems matter. You can show that you breathe out carbon dioxide (Activity 5.4) and that yeast gives out carbon dioxide (Activity 5.5), since both turn lime water milky.

Worked example

Complete the pathways and identify P to V.
Glucose → (in P) → Q + energy
Q → (absence of oxygen, in yeast) → R + energy
Q → (presence of oxygen, in T) → carbon dioxide + water + energy
Q → (lack of oxygen, in U) → V + energy
(3 marks)

Try it first, then show the solutionSolution

1. P = cytoplasm. (½)
2. Q = pyruvate, a three-carbon molecule. (½)
3. R = ethanol and carbon dioxide. (½)
4. T = mitochondria. (½)
5. U = muscle cells. (½)
6. V = lactic acid. (½)

Answer: P cytoplasm, Q pyruvate, R ethanol + carbon dioxide, T mitochondria, U muscle cells, V lactic acid.

Breathing and Exchange of Gases

NCERT section 5.3 Respiration

Plants exchange gases through stomata, and large intercellular spaces keep every cell in touch with air. The direction of diffusion depends on need. At night there is no photosynthesis, so releasing carbon dioxide is the main exchange. By day, carbon dioxide from respiration is used for photosynthesis, so oxygen release is the main event.

Fish use oxygen dissolved in water. Dissolved oxygen is fairly low compared with oxygen in air, so aquatic animals breathe much faster. Fish take water in through the mouth and push it over the gills.

Humans: air enters the nostrils, where fine hairs and mucus filter it. It passes through the throat, where rings of cartilage stop the passage collapsing, and into the lungs. The tubes divide into smaller tubes ending in alveoli, balloon-like sacs with thin walls and a rich network of blood vessels. To breathe in, you lift your ribs and flatten your diaphragm; the chest cavity enlarges and air is sucked in. The lungs always keep a residual volume of air, giving time for exchange. Haemoglobin in red blood corpuscles has a high affinity for oxygen and carries it. Carbon dioxide is more soluble in water, so it travels mostly dissolved in blood.

Worked example

(a) Describe how air enters the lungs when you breathe in. (b) How are gases exchanged in the alveoli? (c) Diffusion alone would take far too long to move oxygen from the lungs to the toes. How is oxygen actually delivered to all body parts? (3 marks)

Try it first, then show the solutionSolution

1. (a) We lift our ribs and flatten the diaphragm; the chest cavity becomes larger, so air is sucked into the lungs and fills the expanded alveoli. (1)
2. (b) The alveoli have thin walls and an extensive network of blood vessels; blood releases carbon dioxide into the alveoli and takes up oxygen from the alveolar air. (1)
3. (c) The respiratory pigment haemoglobin in red blood corpuscles has a very high affinity for oxygen; it picks up oxygen in the lungs and releases it in tissues that lack oxygen, as blood is pumped around the body. (1)

Answer: Inhalation enlarges the chest cavity so air rushes in; gases diffuse across thin, blood-rich alveolar walls; haemoglobin in RBCs carries oxygen to all tissues.

Transportation in Human Beings

NCERT section 5.4.1 Transportation in Human Beings

Blood is a fluid connective tissue. Plasma carries food, carbon dioxide and nitrogenous wastes in dissolved form, and salts too. Red blood corpuscles carry oxygen. The system needs a pump (heart), tubes (blood vessels) and a repair system (platelets).

The heart is a muscular organ about the size of your fist with four chambers, so oxygen-rich and carbon dioxide-rich blood do not mix. The path is: body → right atrium → right ventricle → lungs → left atrium → left ventricle → body. Ventricles have thicker walls than atria because they pump blood out to organs. Valves stop backflow.

Blood passes through the heart twice in one round of the body: double circulation. This gives a highly efficient oxygen supply, useful for birds and mammals, which use energy constantly to keep body temperature steady. Amphibians and many reptiles have three chambers and allow some mixing; fish have two chambers and blood passes once.

Arteries carry blood away from the heart under high pressure, so they have thick, elastic walls. Veins bring blood back and have valves. Capillaries are one cell thick, where exchange happens. Platelets help clot blood at injuries. Lymph (colourless, less protein) carries absorbed fat from the intestine and drains excess tissue fluid back into blood.

Worked example

Describe the path of blood through the human heart, starting from the lungs. Why do ventricles have thicker walls than atria? What is double circulation, and why is it needed in birds and mammals but not in fish? (5 marks)

Try it first, then show the solutionSolution

1. Oxygen-rich blood from the lungs enters the left atrium as it relaxes; the left atrium contracts and the left ventricle relaxes to receive it; the left ventricle contracts and pumps blood to the body. (1)
2. Deoxygenated blood from the body enters the right atrium; it contracts and passes blood to the dilating right ventricle, which pumps it to the lungs for oxygenation. (1)
3. Ventricles pump blood to various organs, so they need thicker muscular walls than atria; valves prevent backward flow. (1)
4. Double circulation: blood passes through the heart twice in each complete cycle through the body (once for the lungs, once for the body). (1)
5. Separating oxygenated and deoxygenated blood gives a highly efficient oxygen supply, needed by birds and mammals, which use energy constantly to maintain body temperature; fish have a two-chambered heart and blood goes through it only once per cycle. (1)

Answer: Lungs → left atrium → left ventricle → body → right atrium → right ventricle → lungs. Ventricles are thicker because they pump to organs. Double circulation keeps the two types of blood apart, giving the efficient oxygen supply that warm-blooded birds and mammals need.

Transportation in Plants

NCERT section 5.4.2 Transportation in Plants

Plants have low energy needs because they do not move and many of their cells are dead, so slow transport works. But distances in tall trees are large, so diffusion is not enough. Two separate tubes do the job:

• Xylem carries water and minerals up from the roots. Vessels and tracheids of roots, stems and leaves join into one continuous channel.
• Phloem carries food from leaves to other parts.

Water transport: root cells actively take up ions, creating a concentration difference, so water moves in from the soil. This pushes a column of water up (root pressure), but that alone cannot lift water to the top of a tree. Water evaporating from leaf cells through stomata (transpiration) creates a suction that pulls water up from the roots. Transpiration also helps temperature regulation. Root pressure matters more at night; by day, with stomata open, transpiration pull is the main force.

Translocation: soluble products of photosynthesis, amino acids and other substances move in phloem sieve tubes, helped by companion cells, upwards and downwards. Unlike xylem, it uses energy (ATP): sucrose is loaded into phloem, osmotic pressure rises, water enters, and pressure pushes material to tissues with lower pressure, such as buds in spring.

Worked example

In Activity 5.8, one pot has a plant and another has a stick of the same height. The soil in both is covered with plastic, both are covered with plastic sheets, and they are kept in bright sunlight for half an hour. (a) What difference is seen and what does it show? (b) Why was the soil covered? (c) Which force mainly moves water up the plant by day, and which matters more at night? (3 marks)

Try it first, then show the solutionSolution

1. (a) Water droplets/moisture collect on the plastic covering the plant but not on the one covering the stick; this shows the plant loses water as vapour from its aerial parts (transpiration). (1)
2. (b) Covering the soil stops moisture escaping from the soil by evaporation, so any water seen must come from the plant. (½)
3. (c) By day, stomata are open and transpiration pull is the major driving force for water movement in xylem. (1)
4. (c) At night, root pressure is more important. (½)

Answer: Only the plant's cover shows moisture, proving transpiration; soil was covered to rule out evaporation from soil; transpiration pull dominates by day and root pressure at night.

Excretion in Human Beings and Plants

NCERT section 5.5.1 Excretion in Human Beings

Excretion removes harmful metabolic wastes, especially nitrogenous ones. Many single-celled organisms simply let wastes diffuse into the water around them. Complex organisms use special organs.

Humans: the excretory system has two kidneys (in the abdomen, one on each side of the backbone), two ureters, a urinary bladder and a urethra. The working unit is the nephron. Each has a cluster of thin-walled capillaries sitting in the cup-shaped Bowman's capsule, which collects the filtrate. Just as lungs remove carbon dioxide from blood, kidneys remove urea or uric acid. As the filtrate moves along the tube, the body takes back the things it still needs: glucose, amino acids, salts and most of the water. How much water is taken back depends on how much extra water the body holds and how much dissolved waste has to go. That is how urine volume is regulated. Urine goes through the ureter to the bladder, which is muscular and under nervous control, so we can hold the urge, and leaves through the urethra.

Plants: they lose oxygen and excess water (transpiration), store wastes in vacuoles, in leaves that fall off, and as resins and gums in old xylem, and release some wastes into the soil.

Worked example

(a) Describe the structure of a nephron and how it forms urine. (b) How is the amount of urine regulated? (c) Give two ways in which plants get rid of wastes. (3 marks)

Try it first, then show the solutionSolution

1. (a) A nephron has a cluster of very thin-walled blood capillaries associated with the cup-shaped Bowman's capsule at the start of a coiled tube; the capsule collects the filtrate from blood. (1)
2. (a) As the filtrate moves along the tubule, the body takes back its useful contents (glucose, amino acids, salts and most of the water); what remains is urine. (½)
3. (b) The amount of water re-absorbed depends on how much excess water is in the body and how much dissolved waste has to be excreted. (½)
4. (c) Any two: storing wastes in cell vacuoles; in leaves that fall off; as resins and gums in old xylem; excreting wastes into the soil; losing excess water by transpiration. (1)

Answer: Nephron = capillary cluster + Bowman's capsule + tubule; filtration then selective re-absorption; urine volume depends on body water and waste load; plants store wastes in vacuoles, falling leaves, gums and resins, or release them into soil.

Science in real life: Life Processes

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

Topics in this chapter

• What are Life Processes?Coming soon
• Nutrition in Plants and Animals
• Respiration
• Transportation in Human Beings
• Transportation in PlantsComing soon
• Excretion in Humans and PlantsComing soon

Life Processes: formulas and key facts

Photosynthesis equation

$6C{O}_2+12H_{2}O\underset{\text{Sunlight}}{\overset{\text{Chlorophyll}}{\to }}{C}_6{H}_{12}{O}_6+6O_2+6H_{2}O$

Write it when asked for the raw materials, conditions or products of autotrophic nutrition. Carbon dioxide is reduced to glucose; water is split and gives oxygen.

Three events of photosynthesis

Absorption of light by chlorophyll → conversion of light to chemical energy and splitting of water into hydrogen and oxygen → reduction of $C{O}_2$ to carbohydrates

Asked as a 2- or 3-mark list. The steps need not follow one another at once: desert plants take in $C{O}_2$ at night.

First step of respiration (all organisms)

$\text{Glucose (6C)}\stackrel{\text{in cytoplasm}}{\to }\text{Pyruvate (3C)}+\text{Energy}$

Common to aerobic and anaerobic routes. Its place is the cytoplasm, not the mitochondria.

Anaerobic respiration in yeast (fermentation)

$\text{Pyruvate}\underset{\text{in yeast}}{\overset{\text{absence of oxygen}}{\to }}\text{Ethanol}+\text{Carbon dioxide}+\text{Energy}$

Less energy is released than in aerobic respiration.

Aerobic respiration

$\text{Pyruvate}\underset{\text{in mitochondria}}{\overset{\text{presence of oxygen}}{\to }}\text{Carbon dioxide}+\text{Water}+\text{Energy}$

Releases a lot more energy than the anaerobic route.

Lack of oxygen in muscles

$\text{Pyruvate}\underset{\text{in muscle cells}}{\overset{\text{lack of oxygen}}{\to }}\text{Lactic acid (3C)}+\text{Energy}$

Build-up of lactic acid during sudden activity causes muscle cramps.

Lime water test for carbon dioxide

$Ca(OH{)}_2+C{O}_2\to CaC{O}_3+H_{2}O$

Lime water turns milky (calcium carbonate forms). Used in Activity 5.4 (exhaled air turns it milky faster than air from a pichkari) and Activity 5.5 (yeast fermentation).

Iodine test for starch

Starch + dilute iodine solution → blue-black colour

Used in Activity 5.1 (variegated leaf: only green parts turn blue-black) and Activity 5.3 (saliva digests starch, so the tube with saliva does not change colour).

End products of digestion

1. 1.Carbohydrates
2. 2.glucose; proteins
3. 3.amino acids; fats
4. 4.fatty acids + glycerol

Completed in the small intestine by intestinal juice. Salivary amylase, pepsin, trypsin and lipase do the earlier steps.

Digestive juices and their jobs

Saliva	amylase (starch → sugar)
gastric juice	HCl, pepsin, mucus
bile	makes food alkaline, emulsifies fats
pancreatic juice	trypsin (proteins), lipase (fats)

Use for 'role of' questions. Bile breaks fats into small globules; lipase actually digests them.

Path of blood (double circulation)

1. 1.Body
2. 2.right atrium
3. 3.right ventricle
4. 4.lungs
5. 5.left atrium
6. 6.left ventricle
7. 7.body

Blood passes the heart twice per cycle. Left side = oxygen-rich, right side = deoxygenated.

Blood vessels

Arteries: away from heart, thick elastic walls; veins: to heart, valves; capillaries: walls one cell thick, exchange site

Use in comparison questions and to explain why arteries need thick walls (high pressure).

Stomata opening and closing

1. 1.Guard cells swell (water flows in)
2. 2.pore opens; guard cells shrink
3. 3.pore closes

Plants close stomata when $C{O}_2$ is not needed, to save water.

Water transport forces

Root pressure (more important at night) + transpiration pull (main force by day, when stomata are open)

Transpiration is loss of water as vapour from aerial parts; it also helps temperature regulation.

Xylem versus phloem

Xylem: water and minerals, upward, physical forces; phloem: food and amino acids (translocation), up and down, uses energy from ATP

Phloem moves material through sieve tubes with help from companion cells.

Urine formation

1. 1.Filtration in Bowman's capsule
2. 2.selective re-absorption of glucose, amino acids, salts and water in the tubule
3. 3.urine to ureter
4. 4.bladder
5. 5.urethra

Amount of water re-absorbed depends on excess water in the body and the amount of dissolved waste.

Life Processes: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the board asks Life Processes

The question patterns to expect, and the method that works for each.

Tricks to remember Life Processes

Short memory aids. Say each one aloud once, then use it on a question the same day.

• ASR for photosynthesis

  Absorb light, Split water, Reduce carbon dioxide.

  Use it when: Lists the three events of photosynthesis in the right order for a 3-mark answer.

• Cytoplasm first, then three roads

  Every glucose goes to Pyruvate in the Cytoplasm (PC). Then: Yeast → Ethanol (YE), Muscle → Lactic acid (ML), Mitochondria → most energy (CO2 + water).

  Use it when: Fills any glucose-breakdown pathway question and stops you swapping yeast and muscle products.

• Right is used, Left leaves

  Right side gets used (deoxygenated) blood from the body; Left side Leaves for the body with fresh oxygen. Order: RA, RV, Lungs, LA, LV, Body.

  Use it when: Tracing double circulation and labelling the heart.

• Arteries go Away

  Arteries carry blood Away from the heart; Veins have Valves.

  Use it when: Quick check for blood vessel comparisons.

• Xylem up, Phloem Food both ways

  Xylem = water climbs up (one way, physical forces). Phloem = Food that flows up and down and pays with ATP.

  Use it when: Difference between xylem and phloem transport.

• KUBU for urine

  Kidney → Ureter → Bladder → Urethra.

  Use it when: Path of urine and labelling the excretory system.

Life Processes: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In the board paper this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Life Processes

The slips examiners see most often, and what to write instead.

• ✗Mistake: Placing the first step of respiration in the mitochondria

  Students link all respiration to mitochondria and forget glucose is split before oxygen is involved.

  Wrong working

  Glucose is broken down into pyruvate in the mitochondria.

  Right working

  Glucose (6C) is broken into pyruvate (3C) in the cytoplasm; only the aerobic breakdown of pyruvate happens in the mitochondria.

  ✓Do this: Learn the chain as 'cytoplasm first, then mitochondria only if oxygen is present'.

  Usually costs: ½ to 1 mark in MCQs and pathway questions.

• ✗Mistake: Swapping the products of yeast and muscle

  Both are routes without enough oxygen, so they get mixed up.

  Wrong working

  In muscles, pyruvate forms ethanol and carbon dioxide; in yeast it forms lactic acid.

  Right working

  In yeast, pyruvate forms ethanol and carbon dioxide; in muscle cells short of oxygen, it forms lactic acid, which causes cramps.

  ✓Do this: Use YE and ML: Yeast-Ethanol, Muscle-Lactic.

  Usually costs: 1 mark per blank, often 1 to 2 marks in a pathway question.

• ✗Mistake: Saying bile digests fats with an enzyme

  Bile acts on fats, so students assume it is the fat-digesting enzyme.

  Wrong working

  Bile contains lipase, which digests fats into fatty acids.

  Right working

  Bile makes the food alkaline and its bile salts break large fat globules into smaller ones (emulsification); lipase from the pancreas then digests the emulsified fats.

  ✓Do this: Remember the pair: bile breaks up fat, lipase breaks down fat.

  Usually costs: 1 mark in a 3- or 5-mark digestion answer.

• ✗Mistake: Saying haemoglobin carries most carbon dioxide

  Students know haemoglobin carries gases and assume it carries both equally.

  Wrong working

  Haemoglobin has a high affinity for carbon dioxide and carries it to the lungs.

  Right working

  Haemoglobin has a very high affinity for oxygen. Carbon dioxide is more soluble in water, so it is mostly carried dissolved in the blood (plasma).

  ✓Do this: Link: haemoglobin = oxygen; plasma = dissolved carbon dioxide.

  Usually costs: 1 mark in assertion-reason or transport questions.

• ✗Mistake: Getting stomata opening backwards

  It feels natural that a pore opens when cells shrink and make room.

  Wrong working

  Stomata open when guard cells lose water and shrink.

  Right working

  When water flows into the guard cells they swell and the pore opens; when they shrink the pore closes.

  ✓Do this: Think 'swell to open'.

  Usually costs: 1 mark in MCQs or 2-mark questions on stomata.

• ✗Mistake: Saying phloem moves food only downwards and without energy

  Students copy the xylem idea of a one-way, physical process.

  Wrong working

  Phloem carries food downward from leaves to roots by simple diffusion.

  Right working

  Translocation in phloem moves food both upward and downward through sieve tubes, helped by companion cells, and uses energy from ATP to load sucrose and raise osmotic pressure.

  ✓Do this: In any xylem-phloem comparison, state direction and energy use for both.

  Usually costs: 1 to 2 marks in a 3-mark comparison.

• ✗Mistake: Writing only the path of blood, not the reason for double circulation

  Students describe chambers and stop, missing the 'why' part of the question.

  Wrong working

  Blood goes from the right atrium to the right ventricle to the lungs, then to the left atrium and left ventricle.

  Right working

  Add: blood passes the heart twice per cycle; this keeps oxygenated and deoxygenated blood apart, giving an efficient oxygen supply for birds and mammals, which need energy to keep body temperature steady.

  ✓Do this: For every 'describe' question, check if it also says 'why' and give a separate line for it.

  Usually costs: 1 to 2 marks in a 5-mark answer.

NCERT exercise guide: Life Processes

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Life Processes: previous year questions

• Asked in 21 of the 21 board papers we hold (2023 to 2026), on average 8.4 marks per paper; 111 questions in all, counting OR alternatives. In 4 of 4 sample papers.

Counted from the real papers on our previous year papers page, not estimated. Average marks are over every board paper we hold, with an OR pair counted once. Chapter tags are ours.

Solved board questions from Life Processes

Real questions from recent papers. Try each one first, then open our step-by-step solution with marks per step.

Every Life Processes question, by year

Practice questions on Life Processes

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which statement about lymph is correct?
   (a) It is red and contains more protein than plasma
   (b) It carries digested and absorbed fat from the intestine
   (c) It is pumped directly from the heart into the arteries
   (d) It is the fluid collected by Bowman's capsule

   Hint

   Think about where lymph forms and where it finally drains.

   Answer

   (b) It carries digested and absorbed fat from the intestine. Lymph is colourless, contains less protein than plasma, forms from fluid escaping through capillary pores, and drains into larger veins.

2. Q2 · 1 mark · Assertion-reasonBoard level

   Assertion (A): Arteries have thick, elastic walls.
   Reason (R): Blood leaves the heart and enters the arteries under high pressure.
   (a) Both A and R are true and R is the correct explanation of A.
   (b) Both A and R are true but R is not the correct explanation of A.
   (c) A is true but R is false.
   (d) A is false but R is true.

   Hint

   Ask why a vessel would need a strong wall.

   Answer

   (a) Both A and R are true and R is the correct explanation of A. The thick, elastic walls withstand the high pressure of blood pumped out of the heart.

3. Q3 · 2 marks · Very short answerBoard level

   Name the two conducting tissues of a flowering plant and state what each one transports. (2 marks)

   Hint

   One tissue carries what comes up from the soil, the other carries what the leaves make.

   Answer

   Xylem transports water and minerals from the soil (1). Phloem transports products of photosynthesis, amino acids and other substances from the leaves to other parts of the plant (1).

4. Q4 · 3 marks · Short answerHarder board level

   Explain how the opening and closing of stomata is controlled. Why does a plant close its stomata at times? Is gas exchange possible when they are closed? (3 marks)

   Hint

   Think of what happens to the guard cells when water flows in or out.

   Answer

   When water flows into the guard cells they swell and the pore opens. When the guard cells shrink, the pore closes (1). Large amounts of water can be lost through stomata, so the plant closes them when it does not need carbon dioxide for photosynthesis (1). Some gas exchange still happens across the surface of stems, roots and leaves (1).

5. Q5 · 3 marks · Short answerHarder board level

   A small cut on your hand bleeds and then stops. Why must leaks in the blood vessels be sealed, and how is this done? Also explain how lymph forms and give its two functions. (3 marks)

   Hint

   A leak causes two problems: loss of blood and loss of something the pump needs.

   Answer

   A leak loses blood and lowers pressure, which reduces the efficiency of the heart's pumping (½). Platelets plug the leak by helping the blood to clot at the injury (½). Some plasma, proteins and blood cells escape through pores in capillary walls into intercellular spaces to form lymph, which drains into lymphatic capillaries and vessels that open into larger veins (1). Lymph carries absorbed fat from the intestine and drains excess fluid from the spaces between cells back into the blood (1).

6. Q6 · 5 marks · Long answerHarder board level

   Copy and complete the pathways:
   Glucose → (in A) → B + energy
   B → (absence of oxygen, in yeast) → C + D + energy
   B → (presence of oxygen, in E) → carbon dioxide + water + energy
   B → (lack of oxygen, in muscle cells) → F + energy
   Then state which pathway releases the most energy, how this energy is made usable by the cell, and why muscles cramp after a sudden sprint. (5 marks)

   Hint

   Each pathway starts by splitting the six-carbon glucose molecule in two.

   Answer

   A = cytoplasm, B = pyruvate (three-carbon), C and D = ethanol and carbon dioxide, E = mitochondria, F = lactic acid (3). The aerobic pathway in the mitochondria releases the most energy (½). The released energy is used to make ATP, which is broken down to drive other reactions in the cell (1). During sudden activity, muscle cells lack oxygen, so lactic acid builds up and causes cramps (½).

7. Q7 · 3 marks · Short answerBoard level

   Compare how a bread mould, an Amoeba and cuscuta (amar-bel) obtain their food. (3 marks)

   Hint

   Ask where each one breaks down its food, and whether it kills its food source.

   Answer

   Bread mould breaks down food outside its body and then absorbs it (1). Amoeba surrounds a food particle with finger-like extensions that form a food vacuole. Food is digested inside the vacuole, simple substances diffuse into the cytoplasm and undigested matter is thrown out (1). Cuscuta is a parasite that takes nutrition from a host plant without killing it (1).

8. Q8 · 5 marks · Long answerHarder board level

   Suppose three hearts are described to you. Heart A has four chambers with the right and left sides fully separated. Heart B has three chambers in which some oxygenated and deoxygenated blood mix. Heart C has two chambers and pumps blood to the gills, from where it goes straight to the body.
   (a) Name one animal group for each heart.
   (b) In which heart does blood pass through only once in one cycle through the body? Explain.
   (c) Trace the path of blood through heart A, starting from the lungs and returning to the lungs.
   (d) Explain why animals with heart A need full separation, while animals with heart B can manage with some mixing. (5 marks)

   Hint

   Link the number of chambers to how much the animal spends on keeping its body temperature steady.

   Answer

   (a) A: birds or mammals; B: amphibians or many reptiles; C: fishes (1½). (b) Heart C, because blood from the heart is oxygenated in the gills and goes directly to the body before returning, so it passes the heart once per cycle (½). (c) Lungs → left atrium → left ventricle → body → right atrium → right ventricle → lungs; the thicker-walled ventricles pump blood out, and valves stop it flowing backwards (1½). (d) Full separation keeps oxygenated and deoxygenated blood apart, giving a highly efficient oxygen supply; birds and mammals constantly use energy to keep their body temperature steady, so they need it. Amphibians and many reptiles take their body temperature from the environment, so they can tolerate some mixing (1½).

9. Q9 · 3 marks · Short answerHOTS / competency

   Suppose a student coats both surfaces of every leaf of a well-watered potted plant with vaseline and keeps it in bright sunlight. Predict and explain two effects on the plant over the next few hours. (3 marks)

   Hint

   Vaseline blocks the stomata. List everything that passes through stomata.

   Answer

   Transpiration from the leaves stops, so the suction that pulls water and dissolved minerals up the xylem is lost. Only the weaker root pressure remains, so upward movement slows, and the cooling effect of transpiration is also lost (1½). Carbon dioxide cannot enter the leaves through the stomata, so photosynthesis falls and less starch is made (1½).

10. Q10 · 3 marks · Short answerHOTS / competency

    Suppose a boy plays football for two hours on a hot afternoon, losing a lot of water as sweat and drinking very little. That evening he passes only a small amount of dark urine. Explain this using the working of the nephron. (3 marks)

    Hint

    The amount of water re-absorbed depends on how much excess water the body has.

    Answer

    Blood is filtered into Bowman's capsule, and as the filtrate flows along the tubule, water, glucose, amino acids and salts are taken back into the body (1). The amount of water re-absorbed depends on how much excess water is in the body. After heavy water loss there is little excess, so more water is re-absorbed (1). Less water is left in the urine while the same dissolved wastes, such as urea, must be removed, so the urine is small in volume and concentrated (1).

11. Q11 · 3 marks · Short answerHarder board level

    Compare the alveoli in the lungs and the nephrons in the kidneys under three headings: (i) the blood vessels involved, (ii) what is removed from the blood, and (iii) what is taken into or back into the blood. (3 marks)

    Hint

    Both are filtering or exchanging units built around very thin-walled capillaries.

    Answer

    (i) Both depend on very thin-walled blood capillaries: an extensive network on the alveolar walls, and a capillary cluster inside Bowman's capsule in the nephron (1). (ii) Alveoli remove carbon dioxide from the blood; nephrons remove nitrogenous wastes such as urea or uric acid (1). (iii) In the alveoli, blood takes up oxygen from the air; in the nephron, glucose, amino acids, salts and most of the water are re-absorbed from the filtrate (1).

12. Q12 · 3 marks · Short answerHOTS / competency

    A classmate says, 'Transpiration only wastes water, so a tall plant would be better off without it.' Evaluate this claim. (3 marks)

    Hint

    Think about how water reaches the top of a tall plant during the day.

    Answer

    The claim is only partly true: water is lost, which is why plants close their stomata when they do not need carbon dioxide (1). But evaporation of water from leaf cells creates a suction that pulls water and dissolved minerals up the xylem from the roots; root pressure alone is unlikely to lift water to the heights seen in plants, and by day transpiration pull is the main driving force (1½). Transpiration also helps in temperature regulation, so the plant would be worse off without it (½).

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Where does the breakdown of glucose into pyruvate take place?Show answer

   In the cytoplasm.

2. 2.What are the products of anaerobic respiration in yeast?Show answer

   Ethanol, carbon dioxide and energy.

3. 3.Which enzyme in saliva digests starch?Show answer

   Salivary amylase; it breaks starch into simple sugar.

4. 4.What is the role of hydrochloric acid in the stomach?Show answer

   It creates an acidic medium that helps the enzyme pepsin digest proteins.

5. 5.What increases the surface area for absorption in the small intestine?Show answer

   Villi, finger-like projections rich in blood vessels.

6. 6.Why do ventricles have thicker walls than atria?Show answer

   They pump blood out to the body or lungs, so they need stronger muscles.

7. 7.What is translocation?Show answer

   Transport of soluble products of photosynthesis (and amino acids) through phloem, using energy.

8. 8.What is the basic filtration unit of the kidney?Show answer

   The nephron, with a capillary cluster inside the cup-shaped Bowman's capsule.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you list the four life processes and say why a multicellular body needs a transport system?
• ☐Can you write the balanced photosynthesis equation and the three events of photosynthesis?
• ☐Can you explain how guard cells open and close the stomatal pore?
• ☐Can you trace starch, protein and fat through the gut, naming each enzyme and end product?
• ☐Can you draw the glucose breakdown chart with places (cytoplasm, mitochondria, yeast, muscle) and products?
• ☐Can you explain why fish breathe faster than land animals and how alveoli suit gas exchange?
• ☐Can you trace blood through all four chambers and explain why double circulation matters in birds and mammals?
• ☐Can you compare arteries, veins and capillaries and state what platelets and lymph do?
• ☐Can you explain root pressure, transpiration pull and translocation, and say when each matters most?
• ☐Can you describe the nephron and explain how the amount of urine is regulated?

Life Processes: frequently asked questions