Population ICSE Class 10: Population Explosion, Demographic Terms and Control

What Population is about

Weightage: CISCE publishes no chapter or unit weightage for ICSE Biology. Population is in the 4. Population part of the 2027 syllabus and can be asked in both Section A and Section B of the 80-mark paper.Source: CISCE ICSE Biology (Science Paper 3) syllabus, examination year 2027

Key concepts

Demographic terms

• Demography: the statistical study of human populations: their size, density, distribution, birth and death rates, age and sex composition.
• Population density: the number of people living per square kilometre of land.
• Birth rate (natality): the number of live births per 1000 people per year.
• Death rate (mortality): the number of deaths per 1000 people per year.
• Growth rate: the change in population per 1000 people per year: birth rate − death rate (ignoring migration). Dividing by 10 gives it as a percentage.

Worked example

A town of 50,000 people records 1,200 live births and 400 deaths in a year, and covers 25 km². Find the birth rate, death rate, growth rate and density.

Try it first, then show the solutionSolution

1. Birth rate = 1,200 ÷ 50,000 × 1000 = 24 per 1000.
2. Death rate = 400 ÷ 50,000 × 1000 = 8 per 1000.
3. Growth rate = 24 − 8 = 16 per 1000 per year (1.6%).
4. Density = 50,000 ÷ 25 = 2,000 people per km².

Answer: BR 24, DR 8, growth 16 per 1000 (1.6%), density 2,000/km².

Why the population rose sharply

Fall in death rate (the main reason):

• Better medical care, hospitals and medicines (antibiotics).
• Vaccination and control of epidemics such as smallpox, plague and cholera.
• Better nutrition, food supply and sanitation.
• Lower infant mortality and higher life expectancy.

Birth rate staying high:

• Illiteracy and lack of awareness of family planning.
• Early marriage.
• Preference for a male child.
• Children seen as extra earning hands and as support in old age (especially in poor families).
• Some social and religious beliefs.

When death rate drops quickly but birth rate drops slowly, the gap between them, the growth rate, becomes large.

Worked example

Mention two reasons why the birth rate in India has remained high.

Try it first, then show the solutionSolution

1. Early marriage lengthens the child-bearing period.
2. Lack of education and awareness about family planning (or preference for a male child).

Answer: Early marriage; illiteracy/lack of awareness (or son preference).

Problems of population explosion

• Unemployment: jobs do not increase as fast as the number of people seeking work.
• Over-exploitation of natural resources: forests cleared, groundwater over-pumped, soil overused and minerals depleted.
• Low per capita income: national income is shared among more people.
• Price rise: demand for food, housing and goods exceeds supply.
• Pollution: more vehicles, industries, sewage and garbage.
• Unequal distribution of wealth: the gap between rich and poor widens.

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

Worked example

How does a rapid rise in population lead to low per capita income?

Try it first, then show the solutionSolution

1. Per capita income = national income ÷ population.
2. If population grows faster than national income, each person's share falls.

Answer: The same income is divided among more people.

Surgical methods of population control

The syllabus names two permanent surgical (sterilisation) methods:

• Vasectomy (in males): a small part of each vas deferens (sperm duct) is cut and tied. Sperms cannot reach the urethra, so the semen has no sperms. It is a minor operation.
• Tubectomy (in females): a small part of each oviduct (Fallopian tube) is cut and tied. The ovum cannot meet sperms, so fertilisation cannot take place.

Neither operation affects sex hormones or sexual characters; the testes and ovaries keep working.

Worked example

Give the biological term for the surgical method of contraception in human females and describe it.

Try it first, then show the solutionSolution

1. The female method is tubectomy.
2. Each oviduct is cut and tied, so the ovum and sperms cannot meet.

Answer: Tubectomy.

Why control is needed

Resources such as land, fresh water and forests are limited, but a growing population needs ever more food, water, housing, energy, jobs, schools and health care. Slowing growth helps:

• raise the standard of living and per capita income;
• reduce pressure on natural resources and pollution;
• improve health and education of families.

Besides surgical methods, awareness, education (especially of girls) and raising the age of marriage help to bring the birth rate down.

Worked example

Suggest two ways a slower population growth rate benefits the environment.

Try it first, then show the solutionSolution

1. Less demand for land means fewer forests cleared.
2. Fewer vehicles, factories and less waste mean less pollution.

Answer: Less deforestation; less pollution.

Population in real life

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

Topics in this chapter

• Demography: Birth Rate, Death Rate and Growth Rate
• Population Explosion: Causes, Problems and Control

Population: key facts

Birth rate

$BR=\frac{\text{live births in a year}}{\text{population}}\times 1000$

Per 1000 per year.

Death rate

$DR=\frac{\text{deaths in a year}}{\text{population}}\times 1000$

Per 1000 per year.

Growth rate

$GR=BR-DR(\text{per }1000);GR\%=\frac{BR-DR}{10}$

Ignores migration.

Population density

$\text{density}=\frac{\text{population}}{{\text{area in km}}^2}$

People per km².

Population: diagrams to practise

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

How the board asks Population

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

Tricks to remember Population

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

• Vas for the Va-sectomy, Tube for Tubectomy

  VASectomy cuts the VAS deferens (male); TUBEctomy cuts the oviduct TUBEs (female).

  Use it when: Surgical methods.

• Per thousand per year

  Every rate in this chapter is 'per 1000 per year'.

  Use it when: Definitions and calculations.

• Deaths fell first

  Medicine cut deaths quickly; customs kept births high: the gap is the explosion.

  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.

Population: 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 B style)

Read the situation, then answer every part. In the board paper this is a 6-mark question split into 2 + 2 + 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 Population

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

• ✗Mistake: Ten years instead of one

  CISCE examiners' comments, 2024: for birth rate, candidates chose births per thousand in ten years instead of one year.

  Wrong working

  Live births per 1000 in 10 years.

  Right working

  Live births per 1000 people per year.

  ✓Do this: Rates are annual.

  Usually costs: 1 mark.

• ✗Mistake: Mortality for natality

  CISCE examiners' comments, 2025: for the number of live births per thousand per year, candidates wrote mortality or growth rate.

  Wrong working

  Live births per 1000 per year = mortality.

  Right working

  Natality (birth rate); mortality is the death rate.

  ✓Do this: Natal = birth; mortal = death.

  Usually costs: 1 mark.

• ✗Mistake: Vague reasons

  CISCE examiners' comments, 2025: for reasons for rapid growth, candidates wrote 'technology' or 'economy' instead of specific reasons such as medical care or vaccination, and 'everything' or 'oxygen' for the resource under pressure.

  Wrong working

  Population grew because of technology.

  Right working

  Death rate fell because of vaccination and better medical care.

  ✓Do this: Name a specific cause and a specific resource (water, land, forests).

  Usually costs: 1 mark each.

• ✗Mistake: Vasectomy for tubectomy

  CISCE examiners' comments, 2024: for the female surgical method, candidates wrote vasectomy and misspelt tubectomy.

  Wrong working

  Female method: vasectomy.

  Right working

  Tubectomy.

  ✓Do this: Tube = oviduct.

  Usually costs: 1 mark.

Practice questions on Population

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

   Death rate is also called:
   (a) natality
   (b) mortality
   (c) demography
   (d) density

   Hint

   Mortal.

   Answer

   (b)

2. Q2 · 1 mark · MCQBoard level

   Tubectomy involves cutting and tying the:
   (a) vas deferens
   (b) urethra
   (c) oviducts
   (d) ureters

   Hint

   Female method.

   Answer

   (c)

3. Q3 · 1 mark · Assertion-reasonHarder board level

   Assertion (A): Better medical care has contributed to population explosion.
   Reason (R): Better medical care reduces the death rate.
   (a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
   (b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
   (c) (A) is true and (R) is false.
   (d) (A) is false and (R) is true.

   Hint

   Gap widens.

   Answer

   (a)

4. Q4 · 3 marks · Short answerHarder board level

   A city of 80,000 people records 2,000 live births and 640 deaths in a year over 160 km². Calculate the growth rate per 1000 and the density.

   Hint

   BR 25, DR 8.

   Answer

   BR = 25, DR = 8, growth = 17 per 1000 (1.7%); density = 500 per km².

5. Q5 · 2 marks · Short answerHarder board level

   Define (a) demography, (b) growth rate.

   Hint

   Study; difference of rates.

   Answer

   (a) Statistical study of human populations (size, density, distribution, birth and death rates). (b) Birth rate minus death rate, per 1000 people per year.

6. Q6 · 2 marks · Short answerHarder board level

   Explain how population explosion causes pollution and unequal distribution of wealth.

   Hint

   More waste; limited resources.

   Answer

   More people produce more sewage, garbage and vehicle and factory emissions (pollution). Limited resources and jobs are captured by fewer people, widening the gap between rich and poor.

7. Q7 · 2 marks · Short answerHarder board level

   Why do vasectomy and tubectomy not affect a person's secondary sexual characters?

   Hint

   Hormones still made.

   Answer

   Only the ducts are cut; the testes and ovaries continue to produce sex hormones, which control secondary sexual characters.

8. Q8 · 2 marks · Short answerHarder board level

   Give two reasons why poor families in rural areas may have more children.

   Hint

   Economics and awareness.

   Answer

   Children are seen as extra earning hands and support in old age; lack of awareness of family planning (also early marriage, son preference).

9. Q9 · 2 marks · Short answerHOTS / competency

   Two countries have the same growth rate of 15 per 1000. In P, BR = 20 and DR = 5; in Q, BR = 40 and DR = 25. Which country is likely to have better health care? Explain.

   Hint

   Compare death rates.

   Answer

   P: its death rate (5) is much lower, suggesting better medical care, vaccination and nutrition.

10. Q10 · 3 marks · Short answerHOTS / competency

    A student says 'Lowering the death rate is bad because it increases population.' Give a balanced response.

    Hint

    Lower births, not more deaths.

    Answer

    Lowering the death rate is good: people live longer, healthier lives. The solution to rapid growth is to bring the birth rate down too (awareness, education, later marriage, family planning such as vasectomy and tubectomy), not to accept more deaths.

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.Define demography.Show answer

   The statistical study of human populations.

2. 2.Another term for death rate?Show answer

   Mortality.

3. 3.Growth rate formula?Show answer

   Birth rate − death rate (per 1000 per year).

4. 4.Structure cut in vasectomy?Show answer

   Vas deferens.

5. 5.Structure cut in tubectomy?Show answer

   Oviducts (Fallopian tubes).

6. 6.Main reason for population explosion?Show answer

   Sharp fall in death rate while birth rate stayed high.

7. 7.Unit of population density?Show answer

   Persons per km².

Quick revision checklist

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

• ☐Can you define birth rate, death rate, growth rate and density precisely?
• ☐Can you calculate them from data?
• ☐Can you give two reasons each for the fall in death rate and the high birth rate?
• ☐Can you list the six problems of population explosion?
• ☐Can you distinguish vasectomy and tubectomy?

Population: frequently asked questions