Relationships between organisms
Connections between organisms
• All living things on the earth
are connected in some way.
• This unit we will study these
relationships:
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–
–
–
Producer/consumer/decomposer
Predator/Prey
Competition
Symbiosis
Producer/consumer/decomposer
• We’ve already learned
that a producer is able
to use the sun’s energy
to make food.
• We’ve also learned that
a consumer has to get
food by eating
producers (herbivore)
or other consumers
(carnivore) or both,
(omnivore).
Producer/consumer/decomposer
• Producers (autotrophs)
capture the energy that
all other organisms rely
on to survive.
• Without producers, the
sun’s energy couldn’t be
used by living things.
Producer/consumer/decomposer
• A decomposer is an
organism that breaks
down waste and dead
organisms.
• Decomposers help to
recycle nutrients.
• Without decomposers,
dead things would pile
up, and nutrients would
run out.
Producer/consumer/decomposer
• Are each of these
organisms a producer,
consumer, or
decomposer?
Consumers - Predator/Prey
• An organism that kills
and eats another
organism for food is
called a predator.
• An organism that gets
killed and eaten by a
predator is called the
prey.
Predator/Prey
• Predator populations rise
and fall in relation to the
prey they eat.
– (If there is a decrease in
the amount of prey, there
will soon be a decrease in
the amount of predators).
– (If there is an increase in
the amount of prey, there
will soon be an increase in
the amount of predators).
Predator/Prey
• Example: Voles vs.
Birds of Prey in Cache
Valley
– Christmas Bird Count
2011
– Wet Spring led to record
low number of voles
– Fewer birds of prey
reported that Christmas.
Competition
• Competition occurs
when 2 or more
organisms are both
trying to use the same
limited resource.
Competition
• Competition could
occur between
producers or consumers
• Competition might
occur between
organisms of the same
species, or different
species.
Competition
• Competition might
occur because of
limited:
–
–
–
–
–
Food
Space
Sunlight
Mates
Or any other limited
resource
Carrying capacity
• The maximum amount
of individuals of a
certain species that an
environment can
support is called the
carrying capacity.
Carrying capacity
• Example: Eurasian
Collared Doves in Cache
Valley
Limiting factor
• The resource that runs
out when a population
reaches its carrying
capacity is called the
limiting factor.
• Limiting factors lead to
competition between
organisms.
Symbiosis
• Symbiosis is when two
different species of
organisms live closely
together for an extended
period of time.
– “Sym” = same
– “bio” = life
• There are 3 types of
symbiosis:
– Mutualism
– Commensalism
– Parasitism
Symbiosis - Mutualism
• Mutualism is when the
2 organisms both
benefit from the
relationship. (They help
each other.)
• +
Symbiosis – Mutualism - Examples
Symbiosis - Commensalism
• Commensalism is when
one of the organisms
benefits from the
relationship, and the
other is not helped or
harmed by it.
•  + unaffected
Symbiosis – Commensalism Examples
Symbiosis - Parasitism
• Parasitism is when one
organism benefits from
the relationship, and
the other organism is
harmed.
• +
Symbiosis – Parasitism - examples
Symbiosis - ?
• Why don’t we have a
word for a relationship
where both organisms
are harmed by the
relationship?
Symbiosis and you
• What is one example of
mutualism that a
person might be
involved in?
• What is one example of
commensalism that a
person might be
involved in?
• What is one example of
parasitism that a person
might be involved in?
Symbiosis and you
• Think about your
friends.
– What would a mutualist
friend be like?
– What would a
commensalist friend be
like?
– What would a parasitic
friend be like?
– What type of friend are
you?