Download Population Density • Population – the members of a species living

Population Density | DAT
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Population Density
• Population – the members of a
species living within a defined
geographic area
• Population density – the number
of individuals of a species living
within a defined geographic area
Survivorship Curve
• A survivorship curve indicates
the number of living individuals
at each age within a population
• A type I survivorship curve is
one in which most individuals
survive until old age
o Typical of humans
A type III survivorship curve is
one in which individuals are
most susceptible to death at a
young age (perhaps by predation)
o But, if they overcome that
high-vulnerability age,
they will likely live into
old age
o Typical of frogs
Type III Survivorship Curve
Individuals are highly susceptible to death early
in life- perhaps due to predation. But, if they live
through their childhood, they will likely live into
old age.
r/K Selection Theory
• r/K selection theory is a theory
that attempts to explain
reproductive patterns within
populations
o It has recently fallen
under much scientific
scrutiny
• r-strategists are species that:
o Are very vulnerable to
death (type III)
Predation
Environmental
disasters
o Reproduce in vast
numbers
Ensuring that at
least some will
survive to
adulthood
Type I Survivorship Curve
Most individuals live until old age.
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A type II survivorship curve is
one in which the age at which
individuals are equally
vulnerable to death at any stage
in life
o Typical of songbirds
Type II Survivorship Curve
Individuals are equally susceptible to death at
any age.
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© 2017 J Co Review, Inc., Accessed by Guest on 04-29-2017
Population Density | DAT
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o Do not have the resources
to offer parental care to
their many offspring
K-strategists are species that:
o Are more protected
against their
environments (type I)
o Reproduce in smaller
numbers
Since there is such
a low mortality
rate
o Are able to offer parental
care to their few offspring
Carrying capacity can be
increased if the population
increases its territory
o Thereby availing itself to
new resources
o This is one reason that
some species migrate
seasonally
Carrying Capacity
• Populations have a carrying
capacity, which is the number of
individuals that can be sustained
by the environment
• A population will typically grow
until it reaches the carrying
capacity
• As the population size
approaches the carrying capacity,
it will taper off
o At this point, it becomes
more difficult to feed and
nurture one’s offspring
So individuals are
dissuaded from
having children
Carrying Capacity
As the population size (y-axis) approaches the
carrying capacity (dotted line), individuals will
be less-inclined to have children and the
population size will level off.
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© 2017 J Co Review, Inc., Accessed by Guest on 04-29-2017