Download Symbiosis Powerpoint File

Agenda:
 Species
Interactions
 Ecosystem
Simulation
Life’s Work:
Read chapter 2
and study for
quiz on Tuesday
Objectives:
 SWBAT distinguish between the different
types of symbiotic relationships.
 SWBAT explain the importance of symbiotic
relationships in population control.
Do Now:
 How would you describe a
relationship between a tick and a
dog? Why?
 How would you describe a
relationship between a human and a
dog? Why?
How Do Species Interact?
Predation
Commensalism
Symbiosis:
interaction
between 2 or
more species
Mutualism
Competition
Parasitism
Parasitism:
when one species
(parasite) feeds on
part of another
species (host) by
living on or in it
• Although parasites can harm
their hosts, they can
promote community
biodiversity.
– Some parasites live inside
host (micro-organisms,
tapeworms)
– Some parasites live outside
host (fleas, ticks, mistletoe,
sea lampreys)
– Some have little contact with
host (dump-nesting birds like
cowbirds, some duck species)
Mutualism:
when both species
benefit
Commensalism:
when one species
benefits without
harming or
benefiting the
other
Predation:
when one species
(predator) feeds
off of another
(prey)
The predator and prey cycle, when graphed, is often
called a “Sawtooth Curve.”
Why is predation important?
• Predators usually
kill the sick, weak or
aged.
• Genetic stock is
improved because
the weaker animals
are killed first.
• The surviving prey
get greater access
to limited
resources.
Competition:
when two or more
species compete
for limited
resources
Factors That Affect Competition
Increasing Competition
• Anything that increases
the population, because
the more organisms
there are, the scarcer
the resources
• Examples: increased
birth rates, decreased
death rates, increased
food supply
Decreasing Competition
• Anything that decreases
the population, because
the fewer organisms
there are, the greater
the resources
• Examples: increased
death rate (from
temperature, drought,
disease, predators, etc.)
Your Turn
• Watch the following video clips and classify
the type of relationship between the species.
• http://www.pbs.org/wnet/nature/lessons/sy
mbiotic-strategies/video-segments/1496/