But, Why SEX?

McVeigh, Steve Dunbar VHS

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.
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