But, Why SEX?






McVeigh, Steve                           Dunbar VHS
5468 N. Lawler Ave                       1-312-567-5437
Chicago, IL 60630
1-312-736-1941

Objectives

1.  To find the importance of sex in the study of continuity of life theme in 
    biology. 
2.  To show the idea of sex offering genetic variability therefore allowing evolution 
    to proceed at a faster rate when necessary. 

Materials

   Various sizes/colors of felt cloth - red, blue, yellow
   Magnets (if chalk board is steel backed) and if NOT, then use pins, tacks, or 
     strips of Velcro tape 
   Colored dittos - red and blue will do

Recommended Strategy

     Ask students the description of the video Pacman game.  Hopefully, they will 
mention monsters, pacman, power pills, maze, etc.  Then develop a "biological" pacman 
maze by using a 3' by 3' piece of RED colored felt. 
     This felt becomes the background environment for the felt pacman shapes that can 
stick to it. 
     Then describe the two pacman types. Each pactype has two traits: eye and skin 
color. One pactype has red colored eyes and blue skin, the other has blue eye color 
and red skin. 
     Arbitrarily decide that blue eye will have superior vision compared to red eye.  
Superior referring to how they can see the power pills/monsters better than red eyes. 
Have the students explain why red skin is superior to blue skin color. The idea is 
that red skin is camouflaged by the RED (maze) environment. 
     Review, if necessary, the idea of genetic information being duplicated and the 
products of this duplication are allocated approximately to the daughter cells so 
that each receives only one copy of each message. 

Activities

1. Have a yellow circle of felt as a nucleus placed within the pacman. Then have two 
   felt chromosomes of different shapes and colors to represent the two traits and 
   the alleles for that trait.  Ask the students what would happen to the 
   chromosomes, if to reproduce, the pacman will undergo binary fission. Use smaller 
   felt pacmen for the daughter cells formed.  Do this reproduction for both 
   pactypes. 

2. Ask what traits would "Super Pacman" have, and what process would allow two 
   monoploid pactypes to produce an offspring with both beneficial characteristics, 
   i.e., superior vision and camouflage in the environment. Point out importance of 
   sexual reproduction in offering genetic variability. 

3. Using colored ditto masters make an activity sheet that the student can mark in 
   the traits, chromosomes, and offspring pactypes, for both asexual & sexual 
   reproduction. However, this time have a BLUE maze environment, and let red eye be 
   superior to blue eye. 

  (Note: in any of the above activities, students can come to the felt maze and move 
         the pactypes and their offspring) 

Reference

   Article by A. Journet in Science Teacher, Oct' 84, page 50.