Genotypes and Phenotypes

 Genotypes and Phenotypes

How does it make sense that selection acts on the phenotype when we know that the genotype is what is passed to the next generation:

To answer this question, I think that it is important that we first illustrate the differences between a phenotype and a genotype. A genotype is an organism's genes. This is the molecular makeup of their being, their code for everything that makes them, well, them. Genotypes change throughout generations and are susceptible to mutations and recombination. Both of these factors cause genotypes to shift and change, creating changes in the organism and their offspring. Phenotypes are the physical representation of these genes. We see phenotypes through the traits that an organism has. Someone might have brunette or blonde hair, but they have it due to the combination and order of their specific genome. Examples of phenotypes include colors of petals, skin, and eyes, length of legs, blood type, stem thickness, etc. 

When looking at selection, or "survival of the good enough", the traits that are good enough to allow an organism to survive, will be the traits that are passed down to new offspring if and when the organisms reproduce. We know that the genotype is what is behind the scenes making these traits exist, but it is the traits themselves that are in competition against each other. For example. Some frogs might have a genotype that gave them the phenotype of sticky toepads, and another frog has a genotype that encoded for normal, non-sticky toepads. If having sticky toepads allows frogs to better climb and reach nutrients, they will be more likely to survive because they will have more food and a higher chance of reproduction compared to the normal frogs. In this scenario, selection is acting on the presence or absence of sticky toepads in order to determine which one leads to the most fitness. The better phenotype will then reproduce, where we see their genotype getting passed on.

Selection puts pressures on different traits to compete. The traits that are more successful and better suited for their environment will lead to a greater chance of survival for the organism. This allows for the coding of the trait, or the genotype, to get passed along. Ultimately producing evolutionary change.