Why does natural selection act on the phenotypes rather than the genotypes of an organism?

Answer 1

This seems to be an odd question to ask...

Unless I'm mistaken, the phenotype of a given organism is governed by its genotype, and changed a fair amount by the organism's environment.

Consider the following circumstances:

Organism A has a long set of arms, and has a "long arm" allele. Organism B has short arms and a "short arm" allele. For example, A's genotype has the "long arm" allele, and seen in its phenotype it has long arms. The converse is true for B.

Judging by your usage of technical terms in your question, I'm sure I don't need to tell you that A will out-compete B, assuming they are in a food-is-up-high environment.

So, A will end up with more offspring than B, again assuming that A and B are members of different species. Eventually organism A will become prevalent, and natural selection will have caused there to be more organisms with the "long arms" phenotype, and the "long arm" allele in their genotype.

In summation, Genotype governs Phenotype, and the best geno- and phenotypes will be chosen by natural selection. By an organism having a superior phenotype, it also has a superior genotype.

Answer 2

Depending on the trait, there may be more than one genotype for a phenotype, meaning both homozygous dominant and heterozygous individuals have an equal chance of survival (so natural selection favors both genotypes). It doesn't really matter whether a plant is homozygous dominant for high sugar content or heterozygous for high sugar content as long as it ends up with a high sugar content and that attracts animals to eat its fruit and spread its seeds.

Answer 3

Phenotype is the way an animal expresses its genotype. You can think of phenotype as the way an organism ultimately looks and acts rather than what dna it is carrying around. In terms of selection, fitness is only determined by how well an animal can survive and reproduce. In terms of survival, there is no difference to an organism if its genotype has recessive genes or not. Detrimental recessive genes do become more rare however because the organism will give birth to less viable offspring.

Answer 4

Natural selection acts on the way that replicators interact with the world around them. In virtually all organisms, the genome does not interact with the environment directly, but does so via intermediaries like proteins, which affect behaviour at the cellular level and ultimately at the level of the organism.

Answer 5

Natural selection works because of the interaction between replicators and their environment. Genes generally do not directly interact with the environment, but through intermediaries, such as proteins and other chemicals, which affect the behaviour of their 'host'.

Answer 6

The environment can act directly on phenotypes, which are, of course the variations presented by genotypes.

Answer 7

Because the phenotype is what exists to react with the environment,

the genes only code for proteins.