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Ch35: Population Change Higher Human Biology. Population. A population is a group of individuals of the same species which makes up part of the community in an ecosystem. - PowerPoint PPT Presentation
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Ch35: Population ChangeCh35: Population Change
Higher Human BiologyHigher Human Biology
PopulationPopulationA population is a group of individuals of the same species which makes up part of the community in an ecosystem.
When a population colonises a new environment the population increases rapidly until it reaches the carrying capacity - the maximum population size that can be maintained by the environmental conditions.
Populations terminologyPopulations terminologyPopulation density – the number of individuals of the same type present per unit area (or volume) of a habitat.Birth rate – the number of new individuals produced by a population during a certain time interval.
Death rate – the number of individuals within a population that have died during the same time interval.
Population Growth CurvePopulation Growth Curve
Time
Number of Individuals
Carrying capacity
Exponential growth
Rapid increase in population size
Birth = Death rate ratePopulation
colonising a new
environment
Population StabilityPopulation StabilityWhen the population reaches the level that the available environmental recourses can just maintain the population becomes stable. At this stage it is in a state of dynamic equilibrium (there are very slight changes but overall it is relatively balanced) and the population has reached its carrying capacity and birth rate equals death rate.Human interference has caused many populations to become unstable or threatened.
The carrying capacity is determined by: Population RegulationPopulation Regulation
• Food• Oxygen• Water• Space
If one is limited it prevents the population increasing
Regulatory Effect
• Predation• Disease• Pollution by organism’s waste
Population decrease
Death by….
Regulation of population sizeRegulation of population size
Population at Carrying capacity
(maximum supported by the environment)
factor limited e.g. food, water
Population
decrease
Population
increase
Population decrease
Death rate increases
Factor plentiful e.g. food, water
Population increase Birth rate increases
Agricultural
Humans have overcome causes of mortality (e.g. predation) so have increased our carrying capacity & have increased exponential growth.
Human Population ExplosionHuman Population Explosion
Revolutionary changes
Rapid population increase
Industrial
• Totally dependent on immediate environment for food, water, shelter.• Live ‘hand to mouth’• No agriculture• No modern technology
Undeveloped SocietiesUndeveloped Societies
Kalahari Bushmen(Africa)
Aborigines(Australia)
e.g. Hunter-gatherers• remote locations• low carrying capacity• low population density• shared society
Arctic Inuit (Eskimos) Population limited by water
availabilityPopulation limited by
low temperature
Influence of modern society on Influence of modern society on undeveloped societiesundeveloped societies
Modern societies have introduced: • tools• technology• disease – led to a population declineCaused problems:• Less land to live off• Traditional cultures are disappearing• Economic & social problems
• Grow crops on own land to meet the families own needs. • Store excess crop for use during times of shortage• Rarely sell any crops or animals• Use basic tools• Use family labour
Subsistence farmingSubsistence farming
Common in Latin
America, Africa &
Asia
• Low standard of living • Often no electricity or sanitation
• Lifestyle similar to 10,000 y.a. at start of agricultural revolution• Population denser than hunter-gatherers
Subsistence Subsistence farming (cont’d)farming (cont’d)
Piped water
Immunisation against diseases e.g. smallpox &
polio
Better housin
g
Effect of Science on Human Effect of Science on Human Population GrowthPopulation Growth
Antibiotics
Modern sanitation
Improvements in child
careEfficient food production
Effect of Science on Human Effect of Science on Human Population GrowthPopulation Growth
1650 AD Advances in
science
Scientific discoverie
s & Inventions
Industrial revolution
Advances in
medicine
These advances have contributed to a human population boom by removing limiting factors that in the past regulated the
population.
Exponential Growth Exponential Growth of Human Populationof Human Population
The human population is now growing exponentially due to:
Overcoming predation (due to guns)
Less child mortality
Increase in life expectancy
Increased female fertility
Fertilisers
Exponential GrowthExponential GrowthAlso due to…
Increased food availabilityMachinery
Pesticides
Change in Cultural HabitsChange in Cultural HabitsWomen tend to suckle their young for less time, as ovulation is inhibited during breast-feeding, women are more likely to conceive their next child sooner.
Births no longer spaced
outBirth rate increases
Doubling Doubling timetime… the length of time for the worlds
population to double.
In 1980s doubling time
was decreasing
steadily thus the world
population was rapidly
increasing
Actually the population growth rate is slowing
down due to…
• use of contraception• social pressures (e.g. China)• deaths from AIDS
World’s wealth is not distributed evenly
The highest population growth is in the poorest
nations so 50% of the world population live in poverty!