Transcript Population Biology

Population Biology
• Under ideal
conditions, populations
will continue to grow at
an increasing rate.
•The highest rate for
any species is called
its biotic potential.
Classic examples: rabbits, yeast have
a high biotic potential
What has a low biotic
potential?
The result is a J-shaped curve.
This assumes . . .
•Unlimited food
•Unlimited space
•NO predation
•NO competition
•NO disease
•NO environmental disruptions
•NO crowding
However, population
growth is usually
restricted by limiting
factors.
abiotic limiting factors
• nutrients
• temperature
• storms
• floods
• drought
biotic limiting factors
• competition
occurs when two organisms
occupy the same niche.
• disease
• parasitism
When a population is limited by
biotic and abiotic factors,
it will not grow out of control.
It will grow until it reaches
carrying capacity.
Carrying capacity is the
number of organisms
of one species that an
environment can support.
A population curve that grows
until it reaches carrying capacity
will be s-shaped.
Populations at carrying capacity will
fluctuate in number. But, overall, birth
rate will equal the death rate.
(immigration = emigration)
This stable state will remain until
some environmental factor changes.
The interaction of predator and prey
result in a predator-prey cycle.