BiologyICSE Class 10 · Population

Population Explosion: Causes, Problems and Surgical Methods of Control (ICSE Class 10)

Updated 16 October 2026 · Fact-checked

Population explosion is a very rapid rise in population, caused mainly by a sharp fall in the death rate (better medicine, vaccination, food and sanitation) while the birth rate stayed high (illiteracy, early marriage, desire for sons). It causes unemployment, over-use of resources, low per capita income, price rise and pollution. Vasectomy and tubectomy are surgical control methods.

Notice that the death rate falls steeply while the birth rate stays high, and the growing gap between them is the population explosion.

Illustration drawn for QuestionBuddy.

Understand Population Explosion: Causes, Problems and Control

What is population explosion? A population explosion is a sudden, very rapid increase in the size of a population, so large that food, water, housing, jobs and services cannot keep up. The world's population grew slowly for thousands of years and then shot up in the last two centuries; India's population has grown in the same way.

Why it happened: the gap between births and deaths. Growth rate = birth rate − death rate. For centuries both were high, so growth was slow. Then the death rate fell sharply while the birth rate fell only slowly, so the gap (the growth rate) became large.

Reasons for the fall in death rate.

Better medical facilities, hospitals and medicines such as antibiotics.
Vaccination and control of epidemics (smallpox, plague, cholera).
Better nutrition and food supply; fewer famines.
Clean drinking water, sanitation and hygiene.
Fewer deaths of infants and mothers at childbirth; longer life expectancy.

Reasons the birth rate stayed high.

Illiteracy and lack of awareness of family planning.
Early marriage, which lengthens the child-bearing period.
Desire for a male child, so families keep having children until a son is born.
Children seen as extra hands to earn and as support in old age, especially in poor families.
Belief that children are a gift of God; social and religious customs.
High infant mortality in the past, so parents had more children to make sure some survived.

Problems caused by population explosion (syllabus list):

Problem	How it arises
Unemployment	jobs do not grow as fast as the number of people seeking work
Over-exploitation of natural resources	forests cut, groundwater over-pumped, soil overused, minerals and fuels used up
Low per capita income	national income is shared among more people
Price rise	demand for food, housing and goods grows faster than supply
Pollution	more vehicles, factories, sewage and garbage
Unequal distribution of wealth	the gap between rich and poor widens

Other strains: shortage of housing (slums), crowded schools, hospitals and transport.

Resources under pressure: land, fresh water, food, forests, fossil fuels and minerals.

Methods of population control. The ICSE 2027 syllabus names the surgical methods (sterilisation), which are permanent:

Vasectomy (males): a small part of each vas deferens is cut and tied. Sperms can no longer reach the urethra, so the semen contains no sperms. Because the vasa deferentia lie just under the skin of the scrotum, this is a minor operation.
Tubectomy (females): a small part of each oviduct (Fallopian tube) is cut and tied, through a small cut in the abdomen. The ovum cannot meet sperms, so fertilisation cannot occur.

Neither operation stops the testes or ovaries from making hormones, so sexual characters are unaffected. Because they are permanent, couples usually choose them after their family is complete.

Why control is needed. Slower growth raises income per person, eases pressure on resources and the environment, and allows better health and education for each child. Awareness, education (especially of girls) and a later age of marriage also help lower the birth rate.

Population Explosion: Causes, Problems and Control: key facts

Death rate fell: Better medical care and antibiotics
Vaccination, control of epidemics
Better food supply
Clean water and sanitation; Main cause of the explosion.
Birth rate stayed high: Illiteracy, little awareness of family planning
Early marriage
Desire for a male child
Children as earning hands and old-age support; Give specific reasons, not 'technology'.
Six problems: Unemployment
Over-exploitation of natural resources
Low per capita income
Price rise
Pollution
Unequal distribution of wealth; Syllabus list.
Surgical control: Vasectomy: males, vas deferens cut and tied | Tubectomy: females, oviducts cut and tied; Permanent; hormones unaffected.

How to answer Population Explosion: Causes, Problems and Control questions

Questions on this topic ask for reasons, problems or control methods; marks go to specific, named points.

1Decide what is asked: a reason for the fall in death rate, a reason for the high birth rate, a problem, or a control method.
2Give a specific reason (vaccination, early marriage), never a vague word (technology, economy).
3For a problem, link cause and effect in one line: more people → same income shared → low per capita income.
4For a resource under pressure, name it: water, land, forests, food, fossil fuels.
5For control, match the sex, the tube and the result: vasectomy, vas deferens; tubectomy, oviducts.

Population Explosion: Causes, Problems and Control in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

A crowded job fair

Suppose a town's job fair offers 200 posts and 5,000 young people turn up.

How many applicants are there for each post, and which problem of population explosion does this show?

Try it first, then show the solutionSolution

5,000 ÷ 200 = 25 applicants for each post.
4,800 people go home without a job.
Jobs have not grown as fast as the number of people of working age: unemployment.

Answer: 25 applicants per post; unemployment.

Memory hook: More hands than jobs.

Children as old-age support

Imagine a small farmer without savings or a pension says he wants many children, especially sons, to help on the farm and look after him in old age.

Which reasons for a high birth rate does this show, and what could change his view?

Try it first, then show the solutionSolution

Children are seen as extra earning hands and support in old age; there is a desire for sons.
Old-age pensions or savings would reduce the need for many children.
Education and awareness that most children now survive would also encourage a smaller family.

Answer: Children as earning hands and old-age support, desire for sons; pensions and education could change it.

Memory hook: Security from savings, not from sons.

Tricks to remember Population Explosion: Causes, Problems and Control

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

Deaths dropped, births stayed
The explosion is the gap: medicine cut deaths fast; customs kept births high.
Use it when: Explaining the cause.
U-O-L-P-P-U
Unemployment, Over-exploitation, Low income, Price rise, Pollution, Unequal wealth.
Use it when: Listing the problems.
VAS for men, TUBE for women
VASectomy cuts the VAS deferens; TUBEctomy cuts the Fallopian TUBEs.
Use it when: Surgical methods.

Population Explosion: Causes, Problems and Control: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Falling deaths · 1 mark · MCQBoard level

Which of the following lowers the death rate rather than raising the birth rate?
(a) early marriage
(b) desire for a male child
(c) vaccination against epidemics
(d) lack of awareness of family planning

Try it first, then show the solutionSolution

Vaccination prevents deaths; the others keep the birth rate high.

Answer: (c) vaccination against epidemics

Example 2: Causes or problems? · 2 marks · Short answerBoard level

A student lists four 'problems caused by population explosion': early marriage, unemployment, vaccination, price rise. Which two are really problems caused by it? What are the other two?

Try it first, then show the solutionSolution

Problems caused by population explosion: unemployment and price rise. (1)
Early marriage is a reason the birth rate stays high, and vaccination is a reason the death rate fell: both are causes, not problems. (1)

Answer: Problems: unemployment, price rise. Early marriage and vaccination are causes.

Example 3: Income per person · 3 marks · Short answerHarder board level

Suppose a town's total yearly income is ₹60 crore and its population is 2,00,000. Ten years later its income has risen to ₹66 crore but its population has risen to 2,50,000.
(a) Find the per capita income at both times.
(b) By what percentage has it changed?
(c) Name the problem this shows.

Try it first, then show the solutionSolution

(a) Before: ₹60,00,00,000 ÷ 2,00,000 = ₹3,000; after: ₹66,00,00,000 ÷ 2,50,000 = ₹2,640. (1)
(b) Fall of ₹360, which is 360 ÷ 3,000 × 100 = 12%. (1)
(c) Low per capita income: income grew by 10% but population by 25%. (1)

Answer: (a) ₹3,000 and ₹2,640 (b) 12% fall (c) Low per capita income

Example 4: Water for a growing town · 3 marks · Short answerHarder board level

Suppose each person in a town needs 135 litres of water a day, and the town's supply is 30 million litres a day. (a) Is the supply enough for 2,00,000 people? (b) What is the shortfall when the population reaches 2,40,000? (c) How might the town then over-exploit a natural resource?

Try it first, then show the solutionSolution

(a) Need = 2,00,000 × 135 = 27 million litres a day: enough. (1)
(b) Need = 2,40,000 × 135 = 32.4 million litres; shortfall = 2.4 million litres a day. (1)
(c) By pumping groundwater faster than rain can refill it, so wells and the water table fall. (1)

Answer: (a) Yes (27 ML) (b) 2.4 million litres a day (c) Over-pumping groundwater

Example 5: Why vasectomy is simpler · 2 marks · Short answerHarder board level

Both vasectomy and tubectomy are permanent methods of population control. (a) Explain why vasectomy is the simpler operation. (b) After a vasectomy, semen is still produced. What is missing from it, and why?

Try it first, then show the solutionSolution

(a) The vasa deferentia lie just under the skin of the scrotum, so they are easily reached; the oviducts lie inside the abdomen, which must be opened by a cut. (1)
(b) Sperms: the cut and tied vasa deferentia stop sperms from the testes reaching the urethra, though the glands still add their secretions. (1)

Answer: (a) The vas deferens is easy to reach; the oviducts need an abdominal cut. (b) Sperms are missing.

Example 6: Case study: raising the age of marriage · 4 marks · Case-basedHOTS / competency

Suppose a state runs a campaign to keep girls in school and to raise the age of marriage.
(a) Give two ways this lowers the birth rate.
(b) Sterilisation does not change the death rate. How, then, does it reduce the growth rate?
(c) Give one reason why the campaign would take many years to slow the growth of the population.

Try it first, then show the solutionSolution

(a) A later marriage shortens the years in which children are born; educated women are more aware of family planning and tend to have fewer children. (2)
(b) Growth rate = birth rate − death rate; sterilisation lowers the birth rate, so the gap narrows. (1)
(c) The girls now in school will marry and have children only years later, and the many young people already born will still have families, so the population keeps growing for some time. (1)

Answer: (a) Shorter child-bearing period; awareness, fewer children (b) It lowers the birth rate (c) Its effect on births comes years later, and many young people are already born

Where students lose marks in Population Explosion: Causes, Problems and Control

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

Mistake: Vasectomy written for tubectomy
CISCE examiners' comments, 2024 Q4(i): asked for the surgical method of contraception in human females, candidates wrote vasectomy, and misspelt tubectomy (e.g. 'tubecotomy').
Wrong working
Female method: vasectomy.
Right working
Female method: tubectomy (oviducts cut and tied).
Do this: Tube = Fallopian tube = female; vas = vas deferens = male. Learn the spelling.
Usually costs: 1 mark.
Mistake: Vague reasons and resources
CISCE examiners' comments, 2025 Q7(ii): for a reason for the reduction in death rate, candidates wrote 'technology' or 'economy' (or an increase in birth rate); for a resource under pressure, they wrote 'everything' or 'oxygen'.
Wrong working
Death rate fell because of technology; resource under pressure: everything.
Right working
Death rate fell because of vaccination and better medical care; resource under pressure: fresh water (or land, forests, food).
Do this: Name one specific cause and one specific resource.
Usually costs: 1 mark each.
Mistake: Mixing causes with problems
Writing 'unemployment' as a reason for population explosion, or 'early marriage' as a problem, swaps cause and effect.
Wrong working
Reason for high birth rate: unemployment.
Right working
Reason: early marriage. Problem: unemployment.
Do this: Causes come before the explosion; problems come after it.
Usually costs: 1 mark.

Exam tips

Keep two separate lists: reasons for the fall in death rate, and reasons the birth rate stayed high.
Use the six syllabus problems by name.
For control methods, give the sex, the duct cut and tied, and the result.
Spell tubectomy and vasectomy correctly.

Practice questions on Population Explosion: Causes, Problems and Control

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

Q1 · 1 mark · MCQBoard level
When a country's income is shared among a rapidly growing number of people, the result is:
(a) price rise
(b) low per capita income
(c) pollution
(d) higher death rate
Hint
Income per head.
Answer
(b) low per capita income
Q2 · 2 marks · Short answerBoard level
What is meant by over-exploitation of natural resources? Give one example caused by a rising population.
Hint
Using faster than it is replaced.
Answer
Using a natural resource faster than it can be replaced. Example: cutting forests for farmland and firewood faster than they regrow (or pumping out groundwater).
Q3 · 2 marks · Short answerBoard level
A family of 4 shares a monthly income of ₹24,000. Two more children are born, but the income stays the same. Find the income per person before and after, and name the problem of population explosion this illustrates.
Hint
Divide the income by the number of people.
Answer
Before: ₹24,000 ÷ 4 = ₹6,000 per person; after: ₹24,000 ÷ 6 = ₹4,000 per person. This shows low per capita income.
Q4 · 2 marks · Short answerHarder board level
Explain how rapid population growth in villages can lead to the growth of slums in cities.
Hint
Land and jobs.
Answer
Farmland is divided among more people and village jobs are too few, so many move to cities in search of work. Housing in cities cannot grow fast enough, so they live in crowded, unplanned settlements without proper water and sanitation: slums.
Q5 · 2 marks · Short answerHarder board level
Suppose a country's total income rises by 5% in a year while its population rises by 2%. Does its per capita income rise or fall, and by about how much?
Hint
Divide 1.05 by 1.02.
Answer
It rises: 1.05 ÷ 1.02 ≈ 1.029, an increase of about 2.9%.
Q6 · 2 marks · Short answerHarder board level
Suppose a town can supply 18 million litres of water a day and each person needs 150 litres. What is the largest population it can support? What happens if the population grows beyond this?
Hint
Divide supply by need.
Answer
18,000,000 ÷ 150 = 1,20,000 people. Beyond this there is a water shortage, and groundwater or rivers are over-exploited.
Q7 · 3 marks · Short answerHOTS / competency
Better medical care at first speeds up population growth in a poor country. Explain why, and how in the long run it can help slow growth down.
Hint
Child survival.
Answer
At first fewer people, especially infants, die while the birth rate stays high, so the growth rate rises. Later, when parents see that their children survive, they no longer need many children to be sure of some surviving, so the birth rate also falls.
Q8 · 3 marks · Short answerHOTS / competency
A health poster says 'Small family, happy family'. Give two ways a smaller family helps each child, and one reason why couples choose sterilisation only after their family is complete.
Hint
Share of resources; permanence.
Answer
Each child gets a larger share of food and care, so health improves; the family can afford better education for each child. Vasectomy and tubectomy are permanent, so they are chosen only when no more children are wanted.

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.Term for a country's income divided by its population?Show answer
Per capita income.
2.Why does early marriage raise the birth rate?Show answer
It lengthens the child-bearing period.
3.Is sterilisation a temporary or a permanent method?Show answer
Permanent.
4.One problem of population explosion seen in cities?Show answer
Slums and housing shortage (also crowded transport).
5.One social measure, besides surgery, that lowers the birth rate?Show answer
Education of girls (or a later age of marriage).

Population Explosion: Causes, Problems and Control: frequently asked questions

Why did the world population grow so slowly for thousands of years?

Both the birth rate and the death rate were high. Epidemics, famines and poor medical care killed many people, especially infants, so the gap between births and deaths, the growth rate, stayed small.

Is India's population still growing?

Yes, though more slowly. India's birth rate has been falling for decades, so its growth rate has come down, but births still outnumber deaths and the population continues to rise.

Do vasectomy and tubectomy protect against infections?

No. They only stop sperm and ovum from meeting. They give no protection against sexually transmitted infections.