Populations

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Populations

• Population- group of individuals of the same
  species occupying a given area
• Increase
• Birth
• Immigration
• Decrease
• Death
• Emigration

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Populations Change

• Populations increase
• Birth rate gt Death Rate
• Immigration gt Emmigration
• Populations Decrease
• Birthrate lt Death Rate
• Immigration ltEmmigration

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Exponential Growth

• r Net Reproduction per individual
• Growth (r) x (N)umber of individuals
• Ex Bacteria r 100 per ½ hour
• Ex Humans r 2-5 /yr
• Doubling Time- Length of time it takes for a
  population to double in size

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Exponential Growth
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Notes on Exponential Growth

• The more of something there is, the more it can
  produce.
• Population Growth Must be Limited
• Limiting Factors
• Food
• Space
• Predators
• Disease
• Polluted Environment

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Carrying Capacity (K)

• Carrying Capacity (K)- Maximum number of
  individuals of a population that a given
  environment can sustain
• This leads to Logistic Growth

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Overshooting K
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History of Human Population
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Figure 28.1Page 499
Three generalized patterns of population
distribution
clumped
nearly uniform
random
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Figure 28.2Page 500
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Demography

• Demography (People Measure)- encompasses
  vital statistics about people, such as births,
  deaths, number of males and females, age
  structure, as well as total population size.
• Age Structure- How many people of there are of
  various ages

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General age structure diagrams
Rapid Growth
Slow Growth
Zero Growth
Negative Growth
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Males Females
Canada
United States
India
Australia
Mexico
China
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Community Ecology

• Community- Several different populations existing
  in the same ecosystem
• Community Ecology- Study of interactions of all
  populations living in the ecosystem

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energy input from sun
PHOTOAUTOTROPHS (plants, other producers)
nutrient cycling
HETEROTROPHS (consumers, decomposers)
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energy output (mainly heat)
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marsh hawk
Sampling of connections in a tallgrass prairie
food web
Higher Trophic Levels
crow
upland sandpiper
garter snake
frog
weasel
badger
coyote
spider
Second Trophic Level
sparrow
ground squirrel
pocket gopher
prairie vole
earthworms, insects
First Trophic Level
grasses, composites
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Energy Input
Energy Input
Transfers
Transfers
Producers (photosynthesizers)
Producers (photosynthesizers)

energy losses as metabolic heat as net export
from ecosystem
energy in organic wastes, remains
energy in organic wastes, remains
energy losses as metabolic heat as net export
from ecosystem
herbivores
decomposers
decomposers
carnivores
detritivores
detritivores
decomposers
Detrital Food Web
Grazing Food Web
Energy Output
Energy Output
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Pyramid of energy flow through Silver Springs,
Florida (kilocalories/square meter/year)
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top carnivores
decomposers detritivores 5,060
carnivores
383
herbivores
3,368
20,810
producers
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Figure 30.8bPage 544
Annual energy flow for Silver Springs, Florida,
ecosystem
20,810 1,679,190