Unit 3 Notes

Elijah Grant
September 30, 2023
EVR1001- Environmental Science
Unit 3 Notes


Chapter 6- Populations
Population Ecology
 Population size, the number of
organisms in an area at a given time,
will grow when resources are
abundant and natural enemies are few.
oDeclines due to resource loss,
natural disaster, or impacts from
another species.

, oThe North American passenger
pigeon and went extinct due to
overhunting.
Carrying Capacity
 Carrying capacity (K)- the maximum
population size of a species that its
environment can sustain.
oAn S-shaped logistic growth curve
 Limiting factors slow and stop
exponential growth.
oCarrying capacity changes.
Limiting factors restrain growth
 Eventually, every population is
constrained by physical, chemical,
and biological limiting factors in the
environment.

, oThese factors determine carrying
capacity, the maximum population
size of a species that an
environment can sustain.
 Population growth slows as it reaches
the carrying capacity. This produces
an S-shaped curve called
logistic growth.
When a population exceeds its habitat’s
carrying capacity, its population can
crash
 Carrying capacity: not fixed
 Reproductive time lag may lead to
overshooting.
 Dieback (crash)
 Damage may reduce area’s carrying
capacity.