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Populations

Populations . AP Environmental Review Caroline, Kristina, Lauren, Gwen, Colby . Populations…. All members of a species inhabiting a specific geographic area (at a time) Size dictated by Emigration Immigration Birth Death. Density. Individuals in a population per unit habitat area

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Populations

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  1. Populations AP Environmental Review Caroline, Kristina, Lauren, Gwen, Colby

  2. Populations… • All members of a species inhabiting a specific geographic area (at a time) • Size dictated by • Emigration • Immigration • Birth • Death

  3. Density • Individuals in a population per unit habitat area • Dependent on • social/population structure • mating • time of year Density= • Distribution/Dispersion types • Random • Clumping – uneven groups • Uniform – rare, even

  4. Exponential Growth • “Geometric” growth • J-shaped Curve • Starts slowly but then accelerates with population increase

  5. Logistic Curve • S-shaped Curve • Begins exponential • Environmental resistance comes into play • Growth slows to accommodate carrying capacity (K)

  6. Carrying Capacity (k) • Maximum number of species which may survive together at a given time • Determined by resources and biotic potential • Exceeding leads to a dieback or crash

  7. Biotic Potential (r) • How a population might grow without presence of environmental resistance (limiting factors) • Density - independent • Exponential

  8. Population growth Reflects Reproductive Strategies

  9. K Strategists • Early reproduction • Large bounties of offspring • accounts for high instance of death • Little care provided • Generally lower tropic levels

  10. R Strategists • Reproduce later in life • Few offspring • Large energy input for care • More prone to extinction • More specialized

  11. Survivorship Curves • Show the number/proportion of group individuals surviving at specific ages • Reflection of reproductive strategies • I. Late loss: K-strategist that produce few young and care for them until they reach reproductive age, reducing juvenile mortality. • II. Constant loss: Intermediate reproductive strategist with fairly constant mortality. • III. Early loss: r- strategists with high infant mortality

  12. Standard Growth Rate (r)=*100

  13. Other Growth Rates • Crude birth rate • live births occurring (per 1,000) in given time CBR = • Crude death rate • amount of deaths (per 1,000) in given time CDR= • Doubling Time (Rule of 70) • Time it would take for a population to double in size 70/r

  14. Total Fertility Rate (TFR) • Average offspring a woman will have in her lifetime • Replacement Fertility Rate • Number of children which must be born to replace those creating them

  15. Growth Trends

  16. Zero Growth • The ultimate goal of a population • Occurs at two phases • When both rates (birth/death) are equally high • When both are equally low (birth+ immigration)= (death+ emigration)

  17. Rapid Growth • Appears “bottom-heavy” • Large portion of population which will soon move to the reproductive stage • Slow Growth • General evenness with growth • Negative Growth • Large portion of population post-reproductive • Small portion to move into reproductive

  18. Human Population Numbers vary according to Industrialization

  19. Demographic Transitions • Societal change in birth and death rates • Both change as industrialization develops

  20. Stage 1: Pre Industrial • Slow population growth • Due to high birth rate and high death rate • Living conditions are poor

  21. Stage 2: Transitional • Improvements bring a decline in death rate • Medical, sanitation, food • Birth rate remains high • Rapid population growth

  22. Stage 3: Industrial • Birth rate slows • Due to further innovation • Meets death rate • General growth slows

  23. Stage 4: Post-Industrial • Birth rate falls below death • Zero population growth

  24. Demographic Transition

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