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									Symbiotic
Relationships
7th Grade Science
Objectives of the Symbiotic
Relationships Lesson
  Students will investigate how organisms or populations
   interact with one another through symbiotic
   relationships and how some species have become so
   adapted to each other that neither could survive
   without the other. (Ohio Academic Standards LS 7.1)

  Students will be able to define and identify the following
   relationships:
     Parasitism
     Mutualistism
     Commensalism
     Neutralism
     Competition
Symbiotic Relationships:
An Introduction
               Click on the picture
                of the leaf cutter at
                the left or on this link
                to view a video about
                symbiosis.
                Leaf cutter video

               You must be
                connected to the
                Internet to view this
                video.
Symbiotic Relationships

  Definition: A relationship between two
   kinds of organisms that lasts over a
   period of time is called symbiosis.
  The word symbiosis can be broken down
   into two parts to determine its meaning.
    sym means together (like in the words
     sympathy and symphony)
    bio mean life (like in the words biology and
     biome)
Types of Symbiosis
  There are five types    Each relationship
   of symbiotic             can be shown using
   relationships.           + - or 0.
      Parasitism          The chart below
      Mutualism            shows these
      Commensalism         relationships.
      Neutralism
      Competition
Parasitism

  Parasitism is the
   situation where one
   organism benefits
   while the other is
   harmed.
  A + / - relationship.
  Think of a friendship
   where you might feel
                         Parasitic Isopod on fish
   used by your friend.
Commensalism
 Commensalism is
  where one species
  benefits while the
  second species
  remains unaffected.
 A + / 0 relationship
 Think of a friendship
  where one of the         Barnacles adhering to the skin of a
                           whale
  friends benefits while
  the other doesn’t
  change.
     Mutualism
                                                    Mutualism is where
                                                     both organisms
                                                     benefit from the
                                                     relationship.
                                                    A + / + relationship.
                                                    Think of a normal
                                                     friendship where
                                                     both friends gain
The clownfish and sea anemone are an example of      something from the
mutualism. Although these anemones stun and devour
other species of fish, clownfish are not harmed.     friendship.
Clownfishes were thought to be commensal on the
giant sea anemones, but there now is evidence that
the aggressively territorial clownfishes chase away
butterfly fishes, who eat anemone tentacles.
Neutralism and Competition

  Neutralism is the        Competition is where
   situation where both      neither species
   species remain            benefits.
   unaffected.              A - / - relationship.
  A 0 / 0 relationship.    Think of someone
  Think of someone          whom you are
   you sit beside but        constantly at battle
   never show any            with.
   emotional either
   positive or negative.
Now Try this
A lion stalks a herd of antelope wading in a
pond. A flock of water birds on the shore
become startled by the sound of the lion’s
approach and fly away with a great deal of
noise. The bird’s sudden departure gives
warning to the antelope, and they are also
able to escape safely. What type of
relationship exists between the birds and the
antelope?
  a) Competition
  b) Mutualism
  c) Commensalism
  d) Parasitism
Try again

  For a relationship to be competition, the
   end result on both sides of the
   relationship is a negative. This isn’t the
   case in this relationship.

  Return to the question.
Not quite

  If the relationship was mutualistic, then
   both sides of the relationship would have
   a positive result from the relationship.
   While the antelope did have a positive
   from the birds (the warning) the birds
   didn’t get a positive from the antelope.

  Return to the question.
You are CORRECT!

  In the antelope and water bird
   relationship, the antelope gets a warning
   of the coming danger (+) the water birds
   don’t get anything from the antelope
   though.

  Next example
Think about this again

  For a relationship to be parasitic, one
   organism benefits from the relationship
   while the other has negative effects from
   the relationship. In this example the only
   negative is for the lion, but we are looking
   at the antelope and water birds.

  Return to the question.
For Practice
 A lichen is a combination of two organisms, an
 alga and a fungus. The fungus gets its food
 from the alga while the alga gets water from
 the fungus. This is an example of which
 relationship?
   a) Competition
   b) Mutualism
   c) Parasitism
   d) Commensalism
Let’s look at this again

  If this were an example of competition,
   both of the organisms would be effected
   negatively. However, in this example
   neither organism is effected negatively.

  Return to the question.
Good Job!

  You’re right! This is an example of a
   mutualistic relationship. The alga gains
   water from the fungus and the fungus
   gains food from the alga. Both need each
   other to live and gain something from the
   other organism.

  Go to the assignment
It’s interesting that you
think this
  In a parasitic relationship, one organism
   gains a positive while the other organism
   receives a negative. In this example,
   neither organism receives a negative.

  Return to the question.
Can we talk about the
example
  In a commensalistic relationship, one
   organism gains something positive. The
   other organism remains unaffected by
   the relationship. In this example, both
   organisms are effected by the
   relationship.

  Return to the question.
Homework

 For homework, complete the
  “Relationships between Organisms –
  Symbiosis” worksheet.
About the Author
 Dave Burkhart is currently the Computer and
  Multimedia Literacy teacher at West
  Muskingum Middle School in Zanesville, OH.
  Prior to this position he taught 7th and 8th
  grade Science for four years. Symbiotic
  relationships was an area of the Science
  curriculum where information appropriate for
  7th graders was hard to find.
  References
 Abbott, D. (2000, May). Retrieved September 22, 2006, from
     Sybiosis Web site: http://www.ms-
     starship.com/sciencenew/symbiosis.htm
 Examples of Commensalism. Retrieved September 22, 2006,
     Web site:
     http://www.cbu.edu/~seisen/ExamplesOfCommensalism.ht
     m
 Meyer, J. R. (1998, January 3). Symbiotic Relationships.
     Retrieved September 22, 2006, Web site:
     http://www.cals.ncsu.edu/course/ent591k/symbiosis.html
 Mutualism. Retrieved September 22, 2006, Web site:
     http://userwww.sfsu.edu/~biol240/labs/lab_03symbiosis/pa
     ges/mutualism.html
 Symbiotic Relationships. Retrieved September 22, 2006, Web
     site: http://necsi.org/projects/evolution/co-
     evolution/symbiosis/co-evolution_symbiosis.html

								
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