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McREL Standards Activity

One of These Things Is Not Like the Other

Purpose:As a result of this activity, students will be able to determine the characteristics that distinguish groups of organisms.
Related Standard & Benchmarks:
 Standard 7.Understands biological evolution and the diversity of life
   Level II [Grade 3-5]
   Benchmark 2. Knows different ways in which living things can be grouped (e.g., plants/animals, bones/no bones, insects/spiders, live on land/live in water) and purposes of different groupings
Student Product:Group participation; assignment sheet
Material & Resources:
  • Numerous pictures of a variety of organisms (e.g., cut out from nature magazines)
  • Glue or paste
  • Construction paper
Teacher's Note:Organisms should include a variety of animals and plants, and could also include mushrooms.  See the "Before Class" section of the activity description for more detailed suggestions.
Students should already be familiar with common taxonomic groupings (e.g., plants and animals; fish, reptiles, etc.).  In this activity, students will look at sets of four or five organisms and determine which organism in each set doesn’t "belong."  They will then determine a variety of characteristics that explain why it doesn’t belong.  The primary goal of this activity is to go beyond the ability to group things and to understand the basis for a given grouping.

Before Class:
Prepare sets of organisms by cutting out pictures of a variety of organisms from nature magazines or other sources.  Organize these pictures into sets of four or five organisms such that all but one fit into a common taxonomic grouping; glue them onto a piece of construction paper.  Possible groupings include plants (exception could be an animal or a mushroom), animals (exception could be a plant or a mushroom), insects (exception could be a reptile or a bird--don’t use spiders here*), birds (exception could be a bat or flying squirrel).  Throw in some organisms that might not be difficult to classify, but might make it harder to determine the distinguishing characteristics.  For example, an "obvious" difference between plants and animals is that plants are green.  However, there are also green animals (e.g., some snakes and insects), and some plants are not green.  And, of course, birds fly:  but so do some mammals--and some birds (e.g., penguins, ostriches) do not fly!  Mushrooms would provide an interesting challenge:  while they are not green like plants, they do not move from place to place like animals.  While it might seem obvious that they are not plants or animals, it will likely prove quite difficult to conclusively determine why.  The point is to organize sets that will require the students to consider many aspects of the organisms to determine their differences--they should find some challenging.  Prepare a final set to be used for the individual assessment; make a reduced copy for each student to work with.
*Differentiating insects and spiders is almost too easy:  the number of legs always works--it is not necessary to consider other characteristics to differentiate them.

In class:
Begin the activity by doing one set of organisms as a class.  Have students suggest which one doesn’t belong.  Then have them explain why it doesn’t belong:  what is it, exactly, about a plant that makes it different from an animal?  Provide guidance.

Let the students divide into small groups and give each group a set of organisms.  They should discuss specific characteristics that distinguish one organism from the rest.  Each group should trade their set with other groups two or three times.  Spend time with each group and guide them in the process.  Encourage the students to look beyond the external appearance of organisms and to find other distinctions (e.g., the presence or absence of a stomach).  It is okay if they cannot find solid distinctions--the important thing is that they think critically and understand the types of characteristics that are used to group organisms.  As the instructor, you can point out characteristics that the students might not yet be aware of.

Have students break out of their groups.  Display the final set of organisms so that all students can see it (or pass it around) and hand out the assignment sheet.  The students should work individually to evaluate the organisms’ characteristics to determine which one does not group with the others.  They should mark that organism on their sheet and then list or describe those characteristics that distinguish that organism from the rest.