Transcript Characteristics of Populations

3000 Km off the
coast of Chile
 5th century – 400
people
 Created Moai…had
food and war was
unknown
 Several centuries
later…15000!
 Not enough
food…rats
introduced…
destroyed the forest!
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Video clip - Attenborough Explains
Easter Island
What can be learned from this?
ARE YOU READY…PAGE 646!!
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Habitat: place where organisms/species
normally live
Species: Organisms that resemble one
another in chemistry, appearance, behaviour,
and genetic makeup, which have the ability to
interbreed with each other to produce fertile
offspring
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Population size: refers to the number of
individuals of a particular species that occupy
a given area or volume at a given time
Population Density: refers to the number of
individuals of the same species that occur per
unit area or volume.
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D = Population Density
N = total numbers counted
S = space occupied by population
N
D
S
Example: 600 deer living in 620 hectare
region of a conservation park would be
calculated as follows…
600 deer
D
 0.967 deer / ha
620 ha
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Small organisms usually have higher
population densities than larger organisms
Population density can be difficult to
establish due to unusable space within a
habitat, so ecologists use two different forms
of calculations…
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Crude Density: the number of individuals of
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Ecological Density: number of individuals of
the same species per total unit area or
volume
the same species per unit area or volume
actually used by the individuals.
Environmental conditions differ throughout a population’s
geographic range causing population dispersion of organisms
within a population to vary throughout the range!
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Is the general pattern in which individuals are
distributed through a specific area
3 main dispersion patters in wild populations
◦ clumped (most common – organisms densely
grouped in areas of habitat with favourable
conditions)
◦ uniform (individuals evenly distributed throughout
habitat)
◦ random (individuals minimally influenced by
interactions with other individuals; habitat conditions
virtually uniform)
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Most populations are dynamic
Numbers and geographic locations change
over time
Sample of the population used to estimate
population size and density using variety of
sampling techniques
Why Measure?
Conservation strategies, harvest rates etc
◦ Quadrat is a sampling frame used for estimating
population size for large areas.
 number of individuals counted within each
quadrat
 total population size estimated via calculations
within a representative area
 most effective for stationary species
 Page 654…
average sample density =
total number of individuals
total sample area
estimated population size = (estimated population density)(total size of study area)
 Used for mobile populations
 Sample of animal captured, marked, released,
 After time to allow animals to mix randomly
with unmarked animals in populations, second
sample captured
 Marked to unmarked in second sample used to
estimate size of entire population
M m
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N
n
M (Total Marked)
N (Total Pop)
N = Mn
m
=
m (# of recaptures)
n (size of recap sample)
N = Mn
m
N=?
M=26
n = 21
m=3
N = 26 x 21
3
N = 182
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Mark-Recapture Demo
Page 567
 sample of animal captured, marked with radio
collars, satellite-linked devices, etc.
 animals tracked for their migration and
behaviour patterns across their geographic
range
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Ethics…
◦ CCAC…Reduce, Refine, Replace
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