Changes In Population Size (Copy)
8.2 Changes in Population Size – Cheat Sheet
Population Growth Curve (S-Shaped / Logistic)
| Stage | Description | Example |
|---|---|---|
| Lag Phase | Slow growth → population adapting to environment | Early settlement of new land |
| Exponential (Log) Phase | Rapid growth as resources plentiful, high birth rate > death rate | Industrial Revolution Europe |
| Carrying Capacity | Growth slows/stabilises when environment cannot support more people | Modern MEDCs with stable populations |
Human Population Changes
| Factor | Effect on Birth Rate | Effect on Death Rate |
|---|---|---|
| Healthcare | Better maternity care lowers infant mortality → fewer births needed | Vaccinations & hospitals reduce deaths |
| Food Supply | Abundant food → higher survival, fewer famines | Malnutrition increases death rates |
| Education | Female literacy reduces fertility (contraception, later marriage) | Health awareness reduces mortality |
| Economic Development | Rising living standards → fewer children needed as workers | Affluence → better healthcare, longer life expectancy |
| War/Conflict | Often reduces birth rate; disrupts families | Direct deaths + poor conditions increase mortality |
| Migration | Immigration increases local population size | Emigration decreases local population size |
Migration Factors
| Type | Push Factors | Pull Factors |
|---|---|---|
| International/Regional | Poverty, war, natural disasters, unemployment | Jobs, safety, education, healthcare |
Quick Pointers
- Human populations follow lag → exponential → stabilisation (carrying capacity).
- MEDCs: low birth & death rates → slow growth.
- LEDCs: high birth rates, falling death rates → rapid growth.
- Migration reshapes local and global population distribution.
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Environmental Management Full Scale Course