Describe how natural selection can sometimes lead to persistence of harmful or even lethal allele include exampple

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Explanation:

This question may have made it seem like natural selection is a harmful process -- be wary of this. To understand this, you have to note something known as heterozygote advantage. All this means is that the heterozygotes, the organism that expresses both the dominant and recessive alleles, rather than the homozygotes, organisms that express both dominant or both recessive alleles, have an advantage. An example is with sickle cell disease. People heterozygous for the sickle cell trait are more resistant to malaria for some reason, whereas the homozygotes are not. Because heterozygotes (which have a harmful allele and normal allele) have the advantage, natural selection selects for this trait and favors it. This leads to the "persistence of harmful or even lethal allele[s]." Again, just because the organism has a lethal allele isn't necessary always a bad thing. :)

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.

you go to account and hit delete!

explanation: