Scientists look at thousands of mutagenized flies, one at a time, under a microscope. they are looking for flies that don't look like they have developed normally. they find a remarkable fly with an extra thorax and a complete extra set of wings. this is an example of

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

b. to discover aspects of the natural world.

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