8.2 Changes in population size Flashcards
what does the growth curve of
populations consists of
- Lag phase
- Log/exponential phase
- Stationary phase
Lag phase:
the period in population growth when an organism is adapting to its new environment and the growth is slow.
Log/exponential phase
when the growth rate of a population increases over time as all requirements are in superabundance.
Stationary phase
no growth – population remains stable It is at the carrying capacity
Carrying capacity:
the maximum size of a population that an environment can support in terms of food, water and other resources.
birth rate
the number of live births per thousand of the population per year.
death rate
the number of deaths per thousand of the population per year.
calculation for national increase
BR-DR/10
calculation for national decrease
DR-BR/10
REASONS FOR HIGH BIRTH RATE
- Pro-natalist policies (governments encouraging couples to have more children)
- High infant mortality (if some babies may die, couples will be tempted to have more children)
- Lack of contraception
- In farming economies of many LEDCs, more people are needed for manual labour; hence families tend to be larger
- No care homes or pensions so old dependents will need their children to care for them in old age.
REASONS FOR LOW BIRTH RATE
- Availability and affordability of contraception
- Reduced infant mortality
- Anti-natalist policies e.g. China’s one child policy
- High cost of raising children
- As pensions are provided, they do not need children to take care of them in their old age.
REASONS FOR HIGH DEATH RATE
7
- Natural disasters
- Poor medical care
- Poor hygiene and sanitation
- Poor diet
- Lack of exercise
- Shortage of clean water
- Diseases
REASONS FOR LOW DEATH RATE
- Good housing conditions
- Safe water supplies
- More than enough food to eat
- Advanced medical services which are easy to access
- Improved levels of exercise
migration
the movement of people into (immigration) or out of (emigration) a region, country or area
Population growth calculation:
- birth rate – death rate
- (birth rate + immigration) – (death rate + emigration)
