Evolution Blog

Genetic drift is RANDOM. Examples of genetic drift include the Founder Effect and the Bottleneck effect.   Natural selection is NOT an example of genetic drift because it is not random. 

 Phenotypic plasticity is the ability of an organism to alter its phenotype in response to the environment without altering its genotype. In "The Genetic Basis of Adaptation following Plastic Changes in Coloration in a Novel Environment," a study was done on lizards that live on lava rocks. When on these lava rocks, the lizards expressed a dark color that was similar to that of the lava rock. However, researchers found that when taken off the lava rocks and put into sand, the lizard's expressed a lighter color in response to the change of substrate.  Additionally, the researchers compared the lava rock lizards to lizards not living on the lava rocks. They found that both groups of lizards expressed dark phenotypes when on the rocks. However, the lizards that already lived on those rocks had a darker phenotype than those who did not. When placed on the sand, researchers found that both groups of lizards expressed the same color of lightness.  Phenotypic plasticity is what ...

 There are three types of selection to be discussed today. 1. Directional Selection     This occurs when the extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. In the example drawn, the shark is looking for a tasty dinner. He swims over by a coral reef where a red fish and an orange & purple fish are trying to hide from him. In this case, the red fish blends in well enough to survive, while the orange & purple fish is not hidden enough and will be the shark's dinner. Therefore, the phenotypic frequency is shifted toward the population of the red fish.  2. Stabilizing Selection          Stabilizing selection occurs when the average phenotypic frequency is favored, rather than either of the extremes. An example of this occurs in birds. When birds lay eggs, the number of offspring they produce is called "clutch size." Birds want to lay as many ...

S= Selection coefficient Delta P= change in allele frequency P= frequency of allele q= frequency of 1-p