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Grade: Middle
Subject: Science

#1581. Natural Selection

Science, level: Middle
Posted Tue Nov 7 07:39:06 PST 2000 by Brad Bessetti (bbessetti@hotmail.com).
Indiana University of Pennsylvania,
Materials Required: colored paper, scissors, colored markers
Activity Time: 25 min

Specific Student Learning Objectives
1.Students should be able to construct a simple definition of evolution.
2.Students can expect to list the key points of Darwin’s theory of natural selection.
There is variation within populations.
Some variations are favorable.
More young are produced in each generation than can survive.
Those that survive and reproduce are those with favorable variations.
3.Students should be able to cite the peppered moth as an example of natural selection as a result of environmental change.

Sequence of Teaching Procedures
1.Look at root word of evolution- evolve. Knowing the definition of evolve, construct a definition for evolution.
2.Go through the outline of the natural selection theory.
Discuss some variations, which ones are favorable, and why they are favorable. Discuss the importance of the high number of offspring produced in each generation.
Explain that if you do not survive, you cannot pass your genes to your offspring.
3.Present background of peppered moth.
Live in forested areas, during day clung to the trees which were covered with light gray lichens, most moths were colored gray which blends in perfectly with the gray tree trunks. Black moths also born into the population, these moths are easily seen against the light gray trunks and are quickly eaten by birds

Industrial Revolution caused pollution that killed lichens making the black moths more abundant because they were better camouflaged against the dark tree trunks. The light gray moths were now more readily seen and eaten by birds.
Pre-industrial 90% light gray, 10% black, Post-industrial 20% light gray, 80% black

Activity
Take half the students into another room. Have the other half cut out paper moths, color them, and hide them all over the room. When all moths are hidden, have the other half of the class find the hidden moths. Students should grasp the concept that the moths that are better camouflaged against their background would be more difficult to see for potential predators.