Transcript Population and Communities

Lesson 2
Populations
and
Communities
Populations and Communities
• limiting factor
• niche
• biotic potential
• symbiotic
relationship
• carrying capacity
• habitat
Populations
• The area in which a population lives
can be very large, such as the
population of all the fish in the ocean,
or very small, like fish in a lake.
• If either biotic or abiotic factors that
affect an organism change, that
organism’s population can also
change.
The area a population lives in can be
large or small.
Populations (cont.)
• Sometimes the size of a population
changes because the ecosystem
changes.
• Population density describes the number
of organisms in the population relative to
the amount of space available.
• If a population is very dense, organisms
might have a hard time finding enough
resources to survive.
The size of a population can change in
different ways.
Limiting factors are factors that can
limit the growth of a population.
Populations (cont.)
• Biotic potential is the potential growth
of a population if it could grow in perfect
conditions with no limiting factors.
• Carrying capacity is the largest number
of individuals that can survive in an area
over a long time.
• The limiting factors of an area determine
the area’s carrying capacity.
Populations (cont.)
• Overpopulation is when a population’s
size grows beyond the ability of the area
to support it.
• This often results in overcrowding, a lack
of resources, and an unhealthy
environment.
Communities
All the populations in the same area
interact as a community.
Symbiotic Relationships
• Each population has different ways to
stay alive and reproduce.
• All of the populations in a community
share a habitat, the physical place
where a population or organism lives.
• A niche is the unique ways an organism
survives, obtains food and shelter, and
avoids danger in its habitat.
Symbiotic Relationships (cont.)
• A symbiotic relationship is one in
which two different species live together
and interact closely over a long period of
time.
• These relationships can be beneficial to
both organisms, beneficial to one and
harmful to the other, or beneficial to one
and neutral to the other.
Types of Symbiotic Relationships
• Mutualism—two species in a community
benefit from the relationship.
• Parasitism—one species (the parasite)
benefits while another (the host) is
harmed.
• Commensalism—one species benefits
and the other is neither helped nor
harmed.
• The factors that limit the
size a population of
organisms can reach
are called limiting factors.
• A habitat is the physical environment
where a population of organisms lives.
• A symbiotic relationship exists when
two different species of organisms live
together in a close relationship over a
long period of time.