3. characteristics that are harmful to a species tend to decrease in frequency from generation to generation because these characteristics usually

This is because these characteristics normally have a low survival value for the species. Natural selection is a process that causes heritable traits that are helpful for survival and reproduction to become more common, and more harmful traits to become rare. This occurs because organisms with advantageous traits pass on more of these heritable traits to the next generation.

They are both used to view parts of the cell