5.5 Environmental Effects on Phenotype

Environmental Effects on Phenotype

Natural Selection
Environmental conditions can influence which phenotypes are more prevalent within a species in an ecological community. This ties into the concept of natural selection, where heritable variations lead to differential reproductive success. In other words, individuals with traits or adaptations that improve their fitness are more likely to survive and reproduce, passing these beneficial traits to their offspring.

Every organism has a genotype, which represents the specific combination of alleles (alternative versions or variants of a gene) that determine a particular trait. Offspring inherit their genotype from a combination of alleles from each parent. An individual’s genotype is distinct from their phenotype, which is the physical expression of their genes—essentially the traits they display.

Environmental Changes 🐁
A classic example of how environmental changes can influence phenotype involves certain mouse species. In an environment covered in permafrost for thousands of years, most mice have light-colored fur, allowing them to blend into their surroundings and evade predators. This advantage raises their chances of survival and reproduction, making the light fur phenotype dominant compared to darker fur variants.

However, due to global warming, the permafrost begins to melt, exposing the dark volcanic soil underneath. In this new environment, light-colored mice become more vulnerable to predation since they are easier to spot, while darker-colored mice gain a survival advantage by blending in. As a result, the allele frequency shifts, favoring darker-colored fur in response to the environmental change.

Phenotypic Plasticity
Environmental factors can also directly influence the physical expression of genes, resulting in a phenomenon called phenotypic plasticity. Phenotypic plasticity occurs when individuals with the same genotype display different phenotypes in response to different environmental conditions. This adaptability allows organisms to adjust their appearance, behavior, or physiology to exploit new or changing ecological niches.

Why is phenotypic plasticity significant? It helps individuals adapt to varying environmental conditions and improve their chances of survival. This adaptability can be influenced by both genetic predisposition and environmental conditions, making some organisms more likely to exhibit plasticity than others.

Environmental Changes 🦊
The arctic fox provides a great example of phenotypic plasticity in action. It has adapted to the extreme seasonal changes of the arctic tundra. During the winter, the arctic fox’s coat turns thick and white, helping it blend in with the snow and ice, making it less visible to predators and prey alike. However, in the summer, its coat changes to a brown or gray color, allowing it to blend in with the rocks and vegetation.

This seasonal change in coat color helps the arctic fox adapt to its environment through camouflage, giving it an edge for survival. The change is triggered by differences in daylight and regulated by the hormone melatonin, illustrating how environmental signals can lead to physical changes that improve the organism’s ability to thrive.