1.6 Human Populations

How does the human population growth curve differ from that of most other

organisms?What factors affect the growth and the

size of the human populations?

Population Ecology

• Study of populations in relation to the environment– Environmental influences on density,

dtribution, age structure, and variation in population size

• Population: group of individuals of same species living in the same area at the same time

Factors affecting population size

• The dispersion pattern of a population refers to the way individuals are spaced within their area– Clumped -

– Uniform: – Random: no pattern

Clumped

Diagram

Example

Uniform

Diagram

Example

Random

Diagram

Example

Figure 35.2C

Dispersion

• Pattern of spacing among individuals• Clumped: individuals aggregated in

patches– Plants: soil conditions appropriate

• Uniform: evenly spaced– Territoriality regulates dispersion

• Random: absence of strong attraction or aversion among individuals

Clumped

Uniform

Random

• doubled three times in the last three centuries

• about 6.1 billion and may reach 9.3 billion by the year 2050

• improved health and technology have lowered death rates

THE HUMAN POPULATION

Glossary

Birth rate

Death rate

Life expectancy

Immigration

Emigration

Demographic Transition

Equations

• Population growth:

• Percentage population growth rate (in a given period)

• Birth rate:

• Death rate:

• The history of human population growth

Figure 35.8A

Figure 35.9B

RAPID GROWTH

Kenya

Male Female

Percent of population Percent of population Percent of population

SLOW GROWTH

United States

Male Female

ZERO GROWTH/DECREASE

Italy

Male Female

Ages 45+

Ages 15–44

Under15

Under15

Ages 45+

Ages 15–44

• The age structure of a population is the proportion of individuals in different age-groups