Stabilizing Selection:
Stabilizing selection is a type of natural selection that favors the average of a specific trait. This means that individuals with traits closer to the average value are more likely to survive and reproduce, while those with extreme traits are less likely to survive and reproduce.
For example, consider a population of lizards that live in a desert environment. These lizards have different variations in body size, ranging from small to large. The small lizards have a higher surface area to volume ratio, which means they can lose heat faster and are better adapted to hot temperatures. The large lizards, on the other hand, have a lower surface area to volume ratio, which means they can retain heat better and are better adapted to cold temperatures.
Over time, the population of lizards experiences stabilizing selection because the average body size is most advantageous in the desert environment. The small lizards are at a disadvantage because they lose heat too quickly and are more susceptible to dehydration. The large lizards are also at a disadvantage because they retain heat too well and are more susceptible to overheating. As a result, the lizards with the average body size are more likely to survive and reproduce, passing on their genes for the average body size to the next generation.
This scenario models stabilizing selection because it favors the average of a specific trait (body size) and selects against extreme traits. The individuals with the average body size are better adapted to the desert environment and have a higher fitness, while the individuals with extreme body sizes have lower fitness and are less likely to survive and reproduce. As a result, the population shifts towards the average body size, which becomes more common over time.