Determining factors for
population size
Mrs. Stewart
Honors Biology
Environment vs Habitat
• Many species can
survive in more than
one environment.
• But each species
has its “home” or
habitat.
– Fish may be able to
live in fish tanks, but
would rather live in
the wild
What do organisms need to
survive?
• Basic requirements
for survival include:
– Food
– Water
– Shelter
Competition
• An important
aspect of the
struggle for survival
involves
competition for
limited resources
–
–
–
–
Food
Water
Shelter
Sunlight
Limiting Factors
• Limiting factors are
factors that affect
the population size
of a species in a
specific
environment.
• They can be abiotic
or biotic.
Predator – Prey relationship
• Predators are a
biotic limiting factor.
• They control
population size by
feeding on prey.
• There is a delicate
balance that needs
to be maintained.
Carrying Capacity
• When all the limiting
factors are
considered
together we can
determine the
maximum number
of organisms that
can survive in an
area.
How do we determine the
Carrying Capacity of a Species?
• All limiting factors
must be taken into
consideration.
• It is very difficult to
determine the
actual carrying
capacity.
The Lesson of the Kaibab Deer
• Purpose:
– to graph data on the
Kaibab deer population
of Arizona from
1905~1939
– to analyze the methods
responsible for the
changes in the deer
population
– to propose a
management plan for
the Kaibab deer
population
Kaibab Forest: North Rim of the
Grand Canyon
Key Idea
• All organisms have
the ability to
produce
populations of
unlimited size
• But their
environment keeps
their numbers in
check.
• THINK-PAIR-SHARE
– How?
– List examples of
limiting factors.
– 3 minutes
How Many Bears??
• Class Activity