Class 10 Science · Original EZT practice
Life Processes (Class 10 Science Chapter 5): the four jobs every living body must do
Staying alive is work: your body must take in food, release energy from it, move materials around, and throw out waste. This chapter groups that work into four life processes - nutrition, respiration, transport and excretion - in plants and in us. Below: the ideas in plain words, then original EZT practice with worked answers. (Note: this is original practice, not a textbook exercise key.)
10 original worked examples, 10 fresh self-check questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 17 October 2026:
1. Nutrition: making or taking food
Green plants make their own food by photosynthesis: carbon dioxide and water, with sunlight trapped by chlorophyll, become glucose and oxygen. Animals cannot make food this way - they eat ready-made food and then ingest, digest, absorb, assimilate and egest it.
2. Respiration: releasing energy from food
Respiration breaks down glucose to release usable energy. Aerobic respiration uses oxygen and releases much more energy. Without oxygen, yeast produces alcohol and carbon dioxide, while hard-working muscles produce lactic acid.
3. Transport: moving materials
In humans, the heart pumps blood through two loops - one to the lungs and one to the body - so oxygen-rich and oxygen-poor blood are kept separate in the heart. In plants, xylem carries water and minerals up from roots, while phloem moves food from leaves to other parts.
4. Excretion: removing waste
Kidneys filter blood through millions of nephrons. Useful substances such as glucose, most water and salts are reabsorbed, while urea dissolved in water leaves as urine. Plants release oxygen and water vapour through stomata and can store some waste in old leaves.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Explain why leaves are green
Choose the method: Connect leaf colour with the pigment that absorbs light for food making.
EZT practice question
Why are most leaves green, and why does that matter for nutrition?
Show the worked solution
- Leaves contain chlorophyll.
- Chlorophyll traps sunlight for photosynthesis.
Answer: Most leaves are green because they contain chlorophyll, the pigment that traps sunlight - the energy source for photosynthesis.
Check: Photosynthesis needs light energy, and chlorophyll is the pigment that absorbs it.
Watch for this: Green colour is not food itself; it is the sign of the pigment that captures light.
Now try it yourself
Why does a variegated leaf usually photosynthesise fastest in its green parts?
Check your answer
The green parts contain chlorophyll.
Chlorophyll absorbs the light energy needed for photosynthesis.
State the role of stomata
Choose the method: Name the pore first, then link it to gas exchange.
EZT practice question
What do stomata do in photosynthesis?
Show the worked solution
- Stomata are tiny pores, mostly on the leaf underside.
- They let carbon dioxide enter and oxygen leave.
Answer: Stomata are tiny leaf pores that take in carbon dioxide and release oxygen; guard cells open and close them.
Check: The gases in photosynthesis move through these pores.
Watch for this: Do not call stomata cells; they are pores controlled by guard cells.
Now try it yourself
Why may stomata close on a very hot, dry afternoon?
Check your answer
To reduce water loss.
Closed pores slow the escape of water vapour.
Arrange holozoic nutrition steps
Choose the method: Follow food from entry to leftover removal.
EZT practice question
Arrange the steps of holozoic nutrition in an amoeba: absorption, ingestion, digestion, egestion, assimilation.
Show the worked solution
- Food is first engulfed into a food vacuole.
- It is then digested, absorbed, used and finally egested.
Answer: Ingestion, digestion, absorption, assimilation, egestion.
Check: An amoeba must take food in before it can digest or absorb it.
Watch for this: Absorption comes before assimilation; absorbed nutrients are then built into the cell.
Now try it yourself
Which step removes undigested residue?
Check your answer
Egestion.
Egestion is the removal of undigested material.
Explain a muscle cramp
Choose the method: Check oxygen supply, then name the product of incomplete breakdown.
EZT practice question
Why do muscles cramp after very hard exercise?
Show the worked solution
- During very hard exercise, oxygen supply can fall short.
- Muscles respire anaerobically and lactic acid builds up.
Answer: Oxygen supply falls short, so muscles switch to anaerobic respiration; the lactic acid produced builds up and causes cramps.
Check: Lactic acid is the product named for anaerobic respiration in muscles.
Watch for this: The cramp is not caused by carbon dioxide alone; lactic acid is the key product.
Now try it yourself
Why does rest ease a lactic-acid cramp?
Check your answer
Oxygen supply recovers and the lactic acid can be cleared.
The muscle no longer depends as heavily on anaerobic respiration.
Connect yeast and rising dough
Choose the method: Identify the gas released by yeast in low-oxygen conditions.
EZT practice question
Bread dough rises when yeast is added. Explain.
Show the worked solution
- Yeast respires anaerobically in the dough.
- It releases carbon dioxide.
Answer: Yeast respires anaerobically and releases carbon dioxide; the gas bubbles puff up the dough.
Check: Carbon dioxide gas creates the spaces in the dough.
Watch for this: Yeast does not make the dough rise by producing alcohol alone; the gas matters.
Now try it yourself
Why is dough left covered in a warm place?
Check your answer
Warmth supports yeast respiration and carbon dioxide release.
Active yeast produces gas faster within a suitable temperature range.
Compare aerobic and anaerobic yield
Choose the method: Check whether glucose is broken down completely.
EZT practice question
Which releases more energy from the same glucose - aerobic or anaerobic respiration?
Show the worked solution
- Aerobic respiration uses oxygen and breaks glucose down completely.
- Anaerobic respiration is partial.
Answer: Aerobic respiration releases far more energy because oxygen allows glucose to be broken down more completely.
Check: Anaerobic products such as lactic acid or alcohol still hold usable energy.
Watch for this: Do not compare speed here; compare total energy released from the same glucose.
Now try it yourself
Why does yeast still leave energy in alcohol?
Check your answer
The glucose breakdown is incomplete without oxygen.
Some chemical energy remains locked in the alcohol.
Trace one double circulation path
Choose the method: Start at the body and follow the right side, lungs, left side and aorta.
EZT practice question
Trace one drop of blood from the body back to the body.
Show the worked solution
- Body blood enters the right atrium through the vena cava.
- It passes to the lungs, returns to the left side and is pumped through the aorta.
Answer: Body -> vena cava -> right atrium -> right ventricle -> lungs -> left atrium -> left ventricle -> aorta -> body.
Check: The path contains both the lung loop and the body loop.
Watch for this: Blood does not move directly from the right ventricle to the left ventricle.
Now try it yourself
Which chamber pumps oxygen-rich blood to the aorta?
Check your answer
The left ventricle.
The left ventricle sends blood into the body loop.
Match vessel design to pressure
Choose the method: Compare pressure and direction of blood flow.
EZT practice question
Why do arteries have thick, elastic walls while veins have valves?
Show the worked solution
- Arteries receive high-pressure blood directly from the heart.
- Veins carry lower-pressure blood back toward the heart.
Answer: Arteries need thick elastic walls for high-pressure blood; veins need valves to stop low-pressure blood flowing backwards.
Check: Arteries carry blood away from the heart and veins carry it back.
Watch for this: Do not say every artery carries oxygen-rich blood; the pulmonary artery is the exception.
Now try it yourself
Why do leg veins especially need valves?
Check your answer
Blood must return upward against gravity.
Valves prevent backflow between heartbeats.
Identify the tissue cut by ringing
Choose the method: Recall which food-carrying tissue lies in the bark.
EZT practice question
Ringing a tree - removing a strip of bark all around - kills it slowly. Which tissue is cut and what stops?
Show the worked solution
- Phloem lies in the bark region.
- Removing the ring stops food transport from leaves to roots.
Answer: The phloem is cut, so food made in the leaves can no longer reach the roots.
Check: Xylem in the deeper wood can still carry water for some time.
Watch for this: Water transport is not the first thing stopped; food transport is.
Now try it yourself
Why may leaves remain alive briefly after a tree is ringed?
Check your answer
Xylem can still supply water.
The deeper xylem is not removed with the bark ring.
Interpret glucose in urine
Choose the method: Start from normal nephron reabsorption.
EZT practice question
A urine report shows glucose present. What does that suggest about the nephrons or blood sugar?
Show the worked solution
- Nephrons normally reabsorb glucose.
- Glucose appears when the filtered amount is too high for complete reabsorption.
Answer: It suggests blood glucose was too high for full reabsorption, a sign doctors check when assessing diabetes.
Check: Normally useful glucose is returned to the blood in the nephron.
Watch for this: Do not diagnose from one line alone; a doctor interprets the full report.
Now try it yourself
Name two useful substances normally reabsorbed by nephrons.
Check your answer
Glucose and most of the water; salts are also reabsorbed.
Reabsorption returns useful filtrate substances to the blood.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- Write the word equation for photosynthesis.
- Give one difference between aerobic and anaerobic respiration.
- Why is human circulation called double circulation?
- Name the unit of the kidney that filters blood.
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Questions about this practice page
- What are the four main life processes?
- Nutrition, respiration, transport and excretion - every living organism takes in or makes food, releases energy, moves materials and removes waste.
- What is the equation for photosynthesis?
- Carbon dioxide and water, using sunlight trapped by chlorophyll, give glucose and oxygen: 6CO2 + 6H2O -> C6H12O6 + 6O2.
- How is aerobic respiration different from anaerobic?
- Aerobic respiration uses oxygen and releases much more energy; anaerobic respiration works without oxygen, producing lactic acid in muscles or alcohol and carbon dioxide in yeast.
- What is double circulation?
- Blood passes through the heart twice in one circuit - one loop goes to the lungs and one to the body - keeping oxygen-rich and oxygen-poor blood separate in the heart.
- Are these the NCERT exercise questions for Life Processes?
- No. EZT pages are original practice on this chapter - use them to prepare for the textbook exercises, not as a substitute for your book.