Population Growth
•Exponential growth:
Population (numbers of individuals)
–The total number of individuals increases as the number of reproducing
females in the population increases.
–Shows a “J” shaped (exponential) curve
Lag phase
Growth is slow due to
small population size.
Generations
Exponential growth
phase
Growth accelerating.
Environmental Limits on Population Growth
•Logistic growth:
Population (numbers of individuals)
–Populations are dependent upon finite resources for survival.
–This will limit the exponential growth phase of a population curve
–Shows an “S” shaped (sigmoidal) curve
Equilibrium phase
Deceleration phase
Exponential growth phase
Lag phase
Generations
Carrying capacity (K)
-The total number of
individuals an
environment can hold.
Population (numbers of individuals)
r and k strategists
r- strategist
Generations
k- strategist
r and k strategists
r-strategists
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Populations never move from the
“r” phase of the growth curve.
Produce far more offspring than
will survive
Population never reaches
“reproductive potential.”
Give no care to offspring
Population is controlled by
density independent factors (i.e.
climatic events, fire, etc.)
Resources are stable and
plentiful.
i.e. bacteria, fungi, insects, small
rodents.
k-strategists
•Populations exist at or near the “k”
phase of the growth curve.
•Expand tremendous energy raising
few offspring.
•Give a lot of care to offspring
•Population is near “reproductive
capacity.”
•Population is controlled by density
dependent factors (i.e. competition
predation, etc.)
•There is a high degree of competition
for limited resources.
•i.e. long lived plants, large mammals,
humans, raptors.