populations
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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POPULATIONS AP Environmental Review
Caroline, Kristina, Lauren, Gwen, Colby
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Populations… All members of a species inhabiting a
specific geographic area (at a time) Size dictated by
Emigration Immigration Birth Death
{(𝑖𝑚𝑚𝑖𝑔𝑟𝑎𝑡𝑖𝑜𝑛+ h𝑏𝑖𝑟𝑡 )−(𝑒𝑚𝑚𝑖𝑔𝑟𝑎𝑡𝑖𝑜𝑛+ h𝑑𝑒𝑎𝑡 𝑠)
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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
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Exponential Growth “Geometric” growth J-shaped Curve Starts slowly but then accelerates with
population increase
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Logistic Curve S-shaped Curve Begins exponential Environmental resistance comes into play Growth slows to accommodate carrying
capacity (K)
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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
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Biotic Potential (r) How a population might grow without
presence of environmental resistance (limiting factors)
Density - independent Exponential
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POPULATION GROWTH REFLECTS REPRODUCTIVE
STRATEGIES
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K Strategists Early reproduction Large bounties of offspring
accounts for high instance of death Little care provided Generally lower tropic levels
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R Strategists Reproduce later in life Few offspring Large energy input for care More prone to extinction More specialized
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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
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Standard Growth Rate
(r) =*100
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Other Growth Rates Crude birth rate
live births occurring (per 1,000) in given timeCBR =
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 size70/r
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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
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GROWTH TRENDS
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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)
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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
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HUMAN POPULATION NUMBERS VARY ACCORDING
TO INDUSTRIALIZATION
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Demographic Transitions Societal change in birth and death rates
Both change as industrialization develops
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Stage 1: Pre Industrial Slow population growth Due to high birth rate and high death rate Living conditions are poor
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Stage 2: Transitional Improvements bring a decline in death
rate Medical, sanitation, food
Birth rate remains high Rapid population growth
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Stage 3: Industrial Birth rate slows
Due to further innovation Meets death rate General growth slows
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Stage 4: Post-Industrial Birth rate falls below death Zero population growth
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Demographic Transition