Population Ecology
Chapter 52
• Population - group of individuals
living in same area at same time.
• Population density - # of individuals
per unit area.
• Population dispersion - arrangement
of population in area.
• Dispersion patterns happen 3 ways.
• 1Clumped dispersion - individuals in
groups.
• 2Uniform dispersion – individuals
evenly spaced out.
• 3Random dispersion - individuals live
regardless of where other
individuals live.
CLUMPED
UNIFORM
RANDOM
• Demography - study of statistics of
a population.
• Life tables - show summary of
specific ages of population and
survival rates.
• Survivorship curve - can see how
many individuals are alive at
specific ages.
• Reproductive tables - reproductive
rates at various ages.
• Focus only on females and not males
in these tables.
• Life history - traits that affect
organism’s schedule of reproduction
and survival.
• 1Big-bang reproduction (produce
large number of offspring
sometimes followed by the
organism’s death)
• Known as semelparity.
The agave plant
• 2Repeated reproductive episode organism produces smaller numbers
of offspring.
• This is also known as iteroparity.
• Change in population - # of births
minus # of deaths during that same
time.
• Equation : N/t = r; r= difference
between birth and death rates, N=
change in population size, and t=
change in time.
• Limitations on population growth
due to resources.
• K = carrying capacity.
• Carrying capacity – max # of
individuals an area can handle based
on resources.
• Logistic population growth model incorporates affect of population
density on rate of increase.
• Carrying capacity cannot be
exceeded - graph is S-shaped.
Carrying capacity
equals change in
population size
Carrying
capacity
Cannot exceed
carrying capacity
• Life histories - predict how
population will reproduce.
• 1K-selection - live and reproduce
around K.
• 2r-selection - high rates of
reproduction, but live in
environments where populations are
well below K.
• 2 factors determine the growth of
a population.
• 1Density-dependent factors
increase their effect as density
increases (negative feedback)
• 2Density-independent factors - not
affected by density increase.
• Negative feedback - caused by
several different factors.
• One - resources (force populations
to stop reproducing if conditions
are crowded)
As # of planted seeds increase,
# reproducing decreases
• Competition for resources can
force decreased reproduction
rates.
• Need to defend space can reduce
population size.
• Predation can decrease the size.
• Human population has been steadily
growing since 1650.
• Zero transition growth # of births
= # of deaths.
• Only way to steady out population
growth.
• One of the difficulties with
population growth is looking at the
distribution of ages.
• The problem is that the carrying
capacity of Earth has not been
determined.
• http://www.youtube.com/watch?v=GECJc
W2Ifm4