Population dynamics
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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

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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


Survivorship curves

Survivorship Curves


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


Population dynamics

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).


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