HUMAN POPULATION

Main ideas Human population growth is exponential Human growth rate has increased dramatically since 1900 due to several factors Growth rate is affected by births, deaths, immigration, and emigration Age structure graphs are used to show the population distribution for a country

I. World population is growing at over 200,000 people per day Current world population is over 7 billion Doubling time is approximately 50 years Human population growth is exponential –We’re on a J-curve of growth More than ½ of world’s population is under 27 (child-bearing age)

Current population growth

Current population growth: Industrialized regions vs. Developing regions

Projected human population

II. Calculating Growth Rate Growth rate is affected by births, deaths, immigration, and emigration –For a country: growth rate = (birth+ immigration) – (death+ emigration) –For the world: growth rate = birth rate – death rate –Negative growth rate means the population is declining

III. What has allowed the human population to grow so fast? Agriculture Technology –Sanitation –Medicine –Refrigeration –Mechanization of agriculture –Nutrition –Etc. All have led to longer life spans

IV. Age Structure Graphs Shows how a population is distributed Shape of graph shows what kind of growth is occurring Wider base = higher growth rate

Shape of graph shows that population is declining