Human population growthIB MYP Biology: Revision notes
Section 1
How the human population grows
The human population changes through births and deaths (and migration in a particular region). If more people are born than die, the population grows.
For most of history the population grew slowly. The world's population was about 1 billion in 1800, about 2.5 billion in 1950 and about 8 billion in 2022. Growth has become much faster, because the death rate fell while the birth rate stayed high.
Section 2
Causes of population growth
- Better medicine: vaccines, antibiotics and hospitals mean fewer people die from infectious diseases, and more babies survive to adulthood.
- Better food supply: improved farming (fertilisers, pesticides, irrigation, machinery) produces more food, so fewer people die from starvation.
- Clean water and sanitation reduce the spread of disease.
All of these lower the death rate. People also live longer. With births still higher than deaths, the population rises.
Do not write that the population grew 'because people had more babies'. In most cases the key change was that the death rate fell.
Section 3
Pressure on resources
A larger population uses more resources:
- more food, so more farming and fishing
- more water for drinking, washing, farming and industry
- more energy, so more fossil fuels are burnt
- more raw materials, such as metals, wood and stone
Some resources are non-renewable and will run out. Others, such as fresh water, are renewable but may be used faster than they are replaced.
Section 4
Land use
People need land for housing, farming, industry, roads and quarrying. As the population grows, more land is used and this often destroys natural habitats.
Examples:
- forests are cleared for farmland (deforestation)
- wetlands and mangroves are drained for building
- farmland is covered with housing and roads
The result is a loss of habitats and a fall in biodiversity, and fewer carbon dioxide-absorbing trees.
Section 5
Waste
More people produce more waste:
- household waste, which is buried in landfill sites or burnt
- sewage, which can pollute rivers and seas if untreated
- industrial waste, including toxic chemicals
- plastics, which last a long time and harm wildlife
- greenhouse gases from burning fuels
Waste can pollute the land, water and air. Recycling, reusing and reducing consumption can lessen the problem.
Must know
- Population grows when births exceed deaths.
- Better medicine and food supply lowered the death rate, so the population grew rapidly.
- A bigger population increases the use of food, water and energy.
- It also increases land use and loss of habitats.
- It increases waste, which pollutes land, water and air.
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Human population growth
- A country in South-East Asia introduced free vaccination for children, clean piped water and better farming methods in the 1960s. Its death rate fell quickly, but its birth rate stayed high for several decades. The population doubled in about 40 years.Explain how the vaccination programme helped the population to grow.2 marks
- A coastal city in Vietnam grew from 1 million to 4 million people in 40 years. Mangrove forests and farmland around the city were cleared to build housing and factories. The city now produces much more household waste and uses far more water from the local river.Explain why the growing population puts pressure on the city's water supply.2 marks
- Demographers estimate that the world's human population was about 1 billion in 1800, about 2.5 billion in 1950 and about 8 billion in 2022.Describe how the rate of growth of the world's human population has changed.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).