Why does natural selection act on the phenotype and not the genotype of an organism?

Question

Why does natural selection act on the phenotype and not the genotype of an organism?

Answer 1

Because the phenotype is the portion of the genetic code available for natural selection to work on.  The genotype is all of the genetic potential of the organism while the phenotype is that portion of the genotype that is expressed.

Answer 2

Genotype is the actual alleles you have.  So, if we use an imaginary trait with a dominant and recessive allele, let's say, tails.  If you have the dominant allele, T, you have a tail, but if you're homozygous recessive, tt, you don't.  

If you are missing a tail, you are at a selective disadvantage because when a predator is chasing you, you can't use your tail to keep your balance as easily.  So, if you are missing a tail, then you have a greater chance of being eaten.

Let's say that your mom had no tail and managed to escape predation.  But, you and your siblings all have tails.  Your genotypes have to be Tt.  So, even though you carry the t allele as part of your genotype, natural selection can't work against it in you because your phenotype is having a tail.

Natural selection can only work on what is expressed.  If a gene is not expressed because it's being masked by another gene's expression, then natural selection cannot work against it.

Answer 3

Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes.

Answer 4

The phenotype is due to the genotype of the individual!  So natural selection is acting on the genotype as well as the phenotype.  If an individual survives to reproduce then its genes will be passed on to the next generation.

Answer 5

It's because the phenotype are the physical characteristics (how they look, how well an animal hears, how efficient it burns fat, etc).  The genotype is the "code" for the phenotype.  

Natural selection will act on whatever characteristics are beneficial/non-beneficial, so it's the outward showing phenotype which matters.