Human Population and Environment
What this domain tests
Human Population and Environment tests demographic concepts and their environmental links: growth rates, doubling time, age structure, demographic transition, migration, urbanisation and carrying capacity. Expect simple calculations and interpretation of population pyramids.
Core rules and concepts
- Population growth = (births + immigration) − (deaths + emigration). Growth rate is usually expressed per 1,000 or as a percentage.
- Exponential growth occurs with unlimited resources; logistic growth shows an S-curve and levels at carrying capacity (K).
- Doubling time ≈ 70 / annual percentage growth rate (rule of 70).
- Age structure: a broad base indicates high dependency and future growth momentum; an ageing population has different needs.
- Demographic transition: high birth and death rates → falling death rates → falling birth rates → low stable rates.
- TFR, infant mortality, literacy (especially female), and contraceptive access shape fertility.
- Environmental links: population × affluence × technology (IPAT) affects resource use and pollution; urbanisation increases demand for water, housing, transport and waste services.
- Rajasthan has regional contrasts: high growth and water scarcity in some desert districts, and rapid urbanisation around Jaipur.
Worked example
A country has a 2% annual growth rate and a population of 50 million. Doubling time ≈ 70/2 = 35 years. In 35 years the population would be about 100 million if the rate stays constant. Reasoning: the rule of 70 comes from the exponential formula; it is an approximation. A falling growth rate does not immediately stop growth because of population momentum from a young age structure.
Traps
Confusing growth rate with absolute numbers; using 100/rate for doubling time; assuming a falling birth rate means a falling population; ignoring immigration. Read whether the question asks for annual increase or total population.