3.1.1-.2 human pop growth
DESCRIPTION
3.1.1-.2 Human Pop Growth. Human population growth. This question is difficult to answer. Estimates are usually based on food, but human agriculture limits assumptions on available amounts. Human population growth rate has been growing more than exponentially. . - PowerPoint PPT PresentationTRANSCRIPT
3.1.1-.2 HUMAN POP GROWTH
HUMAN POPULATION GROWTH
This question is difficult to answer.
• Estimates are usually based on food, but human agriculture limits assumptions on available amounts.
• Human population growth rate has been growing more than exponentially.
What is the carrying capacity of Earth for humans?
HUMAN POPULATION GROWTH
1999
1975
domestication of plants, animals 9000 B.C. (about 11,000
years ago)
agriculturally based urban
societies
beginning of industrial, scientific
revolutions
INCREASE IN GROWTH RATE:• Expansion of habitat• Increased capacity in existing
habitats• Substituting and importing resources• Population has sidestepped limiting
factors:Technology (agriculture)Medicine
POPULATION SIZE HAS LIMITS BEYOND WHICH EVEN HUMANS CAN EASILY CONTROL: The availability of food and water Invasion of parasites, pathogens,
or disease Over-crowding Severe or sudden climatic changes Pollution of air, soil and water
If we do not take steps to control
human population growth, it is
likely that one or more of
these growth-limiting factors will eventually
kick in to forcibly reduce our numbers.
MEASURING POPULATION GROWTH
Crude birth rate = the number of births per thousand individuals in a population per year.
Crude death rate = the number of deaths per thousand individuals in a population per year.
Fertility = the potential of reproduction exhibited in a population.
Developed Nations
Developing Nations
MEASURING POPULATION GROWTH
Natural increase rate = the form in which human population growth rates are usually expressed
Crude birth rate – crude death rate10
GROWTH RATEHuman Population growth = 1.4% per yearDeveloping nations = 1.7%Developed nations = 1.0%
1950 1970 1990 2010 2030
4.5
3.0
1.5
0
Popu
lati
on (
billi
ons) Developing
Countries
Developed Countries
Projections
DOUBLING TIME
Doubling time (T) = 70 .
annual percentage rate (g)Doubling time (T) = 70 . = 50 years
1.4
Doubling time = the number of years it would take a population to double its size at its current growth rate.