POPULATIONS
Dec 28, 2015
POPULATIONS
POPULATIONS
What is a population?
A group of organisms belonging to the same species that live in a particular area
POPULATIONS
Described based on:•Size•Density•Distribution
POPULATION DENSITY
Measures the number of individual organisms living in a defined space.
Regulation of a population is affected by limiting factors
POPULATION GROWTHFACTORS THAT AFFECT POPULATION
SIZE:• Birth rate• Death rate• Movement into or out of the
population
CHANGES IN POPULATION
IMMIGRATION• Individuals move into an area• Results: The population grows
EMIGRATION• Individuals move out of an area• Results: The population decreases
EXPONENTIAL GROWTH• Occurs when individuals in a population
reproduce at a constant rate• Under ideal conditions with unlimited
resources• But in the real world resources are
limited…
J-Shaped Curve
LOGISTIC GROWTH• Occurs when a population’s growth
slows or stops following a period of exponential growth
• Population growth slows:• Death rate = birth rate• Immigration = emigration
CARRYING CAPACITY
• The largest number of individuals that the given environment can support
S-Shaped Curve
LIMITING FACTORS
LIMITING FACTORS• A factor that causes the
population growth to decrease• Affects may vary depending on
the population and the limiting factor
LIMITING FACTORS1. DENSITY-DEPENDENT FACTORS
2. DENSITY-INDEPENDENT FACTORS
3. BIOTIC & ABIOTIC FACTORS
DENSITY-DEPENDENT
• Depends on the size of the population
• Operate most strongly when a population is large and dense
DENSITY-DEPENDENT1. Competition
•Food, water, space, sunlight, etc.
2. Predation
3. Parasitism
4. Disease
DENSITY-INDEPENDENT• Occurs regardless of how large
the population is• Reduce the size of all populations
in an area by the same proportion
DENSITY-INDEPENDENT• Unusual weather• Natural disasters
• Fires, Floods, etc.• Human activities
• Pollution, Cutting down forests, damming rivers, etc.
ABIOTIC & BIOTIC FACTORS• A change in an abiotic or biotic
factor may decrease the size of a population if it cannot adapt to or migrate from the change.
HUMAN POPULATIONS
POPULATION GROWTH• Human population world-wide has
grown exponentially.• Based on current trends,
scientists predict the population to continue grow at a rapid rate.
POPULATION GROWTH• Population growth slows as it
nears Earth’s carrying capacity because of:• Food and water shortages• Pollution• Spread of diseases
POPULATION GROWTH• An increasing population can
have an effect on:• The amount of clean water• The amount of waste produced• The amount of available fertile soil
for agriculture (food resources)
FERTILE SOIL / AGRICULTURE
• Worldwide demand for land has led to deforestation• Fewer trees to absorb CO2, increase
CO2 contributes to global warming
• Increases the rate of erosion• Decreases the rate of soil
generation
FERTILE SOIL / AGRICULTURE
• Soil has 4 distinct components:• Inorganic minerals• Organic matter• Water• Air
• Soil erosion and deposition—natural processes that move soil from one location to another
CONSUMPTION OF RESOURCES
• As the population increases, so does the demand for resources.
• There is a limited supply of these resources available to sustain the human population
RESOURCES
• Renewable resources• Can be produced at roughly the
same rate that they are consumed
• Food, clean water, timber
RESOURCES
• Nonrenewable resources• Cannot be produced at the same
rate that they are consumed• Fossil fuels, minerals, metals,
ores
RESOURCES
• Sustainable use of resources can be accomplished by:• Reducing consumption• Reusing products• Recycling waste
WASTE
• An increasing population increases the amount of waste produced.• More waste is being produced than can
be managed effectively• Some waste products require
complicated and costly means for removal once introduced into the environment
TECHNOLOGY• Technology has benefited humankind—
But has contributed to the pollution of air, water and land.• Agricultural• Industrial• Alternative energy
*Advances can have a positive or negative impact on Earth
AGRICULTURAL TECHNOLOGY
• Improved ability to grow crops (+)• Conserve fertile soil and reduce erosion (+)• Farm machinery consumes nonrenewable
resources (-)• Contributes to erosion & air pollution (-)• Fertilizers, pesticides, fungicides, etc. can
alter soil composition and effect water, carbon or nitrogen cycles (+/-)
INDUSTRIAL TECHNOLOGY
• Developments in communication, transportation and industry (+)
• Chemicals (CFC’s) deplete ozone layer (-)• Disposal of outdated/damaged equipment (-)• Increases greenhouse gases (mainly CO2) (-)
• Produces acid rain (-)
ALTERNATIVE ENERGY
• Uses natural renewable resources (wind, water, geothermal, solar energy) (+)
• Decreases burning of fossil fuels (+)• Nuclear energy technology is another
alternative—does not impact the atmosphere, but waste produced is a concern (-)
can be
represented bycharacterized by characterized by represented by
which cause a
Go to Section:
PopulationGrowth
can be
represented bycharacterized by characterized by represented by
which cause a
Fallinggrowth rate
S-shapedcurve
Limits ongrowth
No limits on growth
J-shapedcurve
Constantgrowth rate
Unlimitedresources
Go to Section:
Exponentialgrowth
Logisticgrowth