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Population Dynamics. - the study of how populations change in size, density and age distribution. Populations in Nature. Population Density Most populations clump together: for resources, for protection, for mating, for effective hunting Population Growth =

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population dynamics

Population Dynamics

- the study of how populations change in size, density and age distribution

populations in nature
Populations in Nature
  • Population Density
    • Most populations clump together: for resources, for protection, for mating, for effective hunting
  • Population Growth =
    • (births + immigration) – (deaths + emmigration)
r selected species and exponential growth
R-selected species and Exponential Growth
  • R = intrinsic rate of increase = biotic potential
    • Each individual has maximum number of offspring
  • Population is well below available resources
  • Reproductive (life-history strategies)
    • Reproduce early in life span
    • Reproduce many offspring
    • Provide minimum care for offspring
  • Exponential Growth
k selected species and logistic growth
K-selected species and Logistic Growth
  • K = carrying capacity= environmental resistance
    • Maximum population an ecosystem can sustainably support
  • Population at or near available resources
  • Reproductive (life-history strategies)
    • Reproduce late in life span
    • Reproduce few offspring
    • Provide a lot of care for offspring
  • Logistic Growth
limiting factors
Limiting Factors
  • Resources limit population growth
    • Density dependent limiting factors
    • Density-independent limiting factors
history of the human population
History of the Human Population
  • Hunter Gatherer Societies (5 m.y.a. – 8,000 b.c.)
    • Food, water, shelter, etc.were limiting factors
    • Total population less than a few million
  • Rise of Agriculture (8,000 b.c. – 1800 a.d.)
    • Ability to store food improved lifespan
    • First major increase in population
  • Industrial Revolution (1800 – present)
    • Rapid population increase due to sanitation, medicine, and transportation technologies
changes in population
Changes in Population
  • Change in population =

(births + immigration) – (deaths + emigration)

  • Age structure diagrams (population pyramids)

Predict future population growth

what factors determine fertility rate
What factors determine fertility rate?
  • Fertility Rate = number of children a woman has
    • Total fertility rate
  • What determines fertility rate?
    • Cost of raising children and how early they begin work
    • Availability of private & public pension (retirement)
    • Urbanization: access to medical care, contraceptives education, and employment for women
    • Culture, religion, including average age of marriage
    • Availability of legal abortions
what factors affect mortality rates
What factors affect mortality rates?
  • Mortality rate = number of deaths
    • Indicators of quality of life:
    • Life expectancy
    • Infant mortality
  • What determines mortality rate?
    • Nutrition
    • Medical advances
    • Improved sanitation and safe water
demographic transition
Demographic Transition
  • Stage 1: Pre-Industrial Age
    • High birth rate, high death rate
  • Stage 2: Agricultural/Industrial Age
    • Death rate declines: improved sanitation, nutrition
  • Stage 3: Industrial Age
    • Birth rate declines: social changes
  • Stage 4: Post-Industrial Age
    • Low birth rate, low death rate
the classic stages of demographic transition
The Classic Stages of Demographic Transition

Note: Natural increase is produced from the excess of births over deaths.

challenges of population growth
Challenges of Population Growth
  • Infrastructure: public water, sewer, power plants, power lines, roads, schools, etc.
    • Clean water
    • Resource shortages (fuel, wood)
    • Agriculture can deplete soil
    • Urban sprawl: traffic, habitat destruction
slide15

Population Structures by Age and Sex, 2005

Millions

Less Developed Regions

More Developed Regions

Age

80+ 75-79 70-74 65-69 60-64 55-59 50-54 45-49 40-44 35-39 30-34 25-29 20-24 15-19 10-14 5-9

0-4

Male

Female

Male

Female

Source: United Nations, World Population Prospects: The 2004 Revision, 2005.

world population growth through history
World Population Growth Through History

12

11

2100

10

9

Modern

Age

Old

8

Iron

Middle

Bronze

Stone

Age

New Stone Age

Ages

Age

Age

7

Future

6

2000

Billions

5

4

1975

3

1950

2

1900

1

1800

Black Death

The Plague

2000

1+ million

7000

6000

5000

3000

1000

A.D.

4000

A.D.

A.D.

A.D.

A.D.

A.D.

years

B.C.

B.C.

B.C.

B.C.

B.C.

B.C.

B.C.

1

1000

2000

3000

4000

5000

Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).