Question
Directional selection and discruptive selection example
Answers
GPT-4o mini
Directional selection and disruptive selection are two types of natural selection that can lead to changes in a population over time. Here are examples of each:
### Directional Selection:
**Example: Pepper Moths (Biston betularia)**
In England during the Industrial Revolution, the environment changed due to pollution; tree bark became darker due to soot. The lighter-colored pepper moths, which were previously common, became more visible to predators on the darkened trees. Consequently, the darker variants of the pepper moths had a survival advantage and were more likely to reproduce. Over time, the population shifted to a higher frequency of darker moths, demonstrating directional selection towards the trait of darker coloration.
### Disruptive Selection:
**Example: African Seedcracker Finches (Pyrenestes ostrinus)**
In certain environments with a variety of seed types, African seedcracker finches exhibit disruptive selection. These finches have either large or small beaks, which allows them to exploit different types of seeds available in their habitat. Birds with medium-sized beaks are less efficient at cracking seeds compared to those with large or small beaks since they cannot specialize in either type. As a result, over time, the population diverges, leading to an increase in the frequency of both large and small beaked individuals, and a decrease in medium beaked birds, reflecting disruptive selection.
Both examples illustrate how different forms of natural selection can drive the evolutionary trajectories of populations based on their environments and available resources.
### Directional Selection:
**Example: Pepper Moths (Biston betularia)**
In England during the Industrial Revolution, the environment changed due to pollution; tree bark became darker due to soot. The lighter-colored pepper moths, which were previously common, became more visible to predators on the darkened trees. Consequently, the darker variants of the pepper moths had a survival advantage and were more likely to reproduce. Over time, the population shifted to a higher frequency of darker moths, demonstrating directional selection towards the trait of darker coloration.
### Disruptive Selection:
**Example: African Seedcracker Finches (Pyrenestes ostrinus)**
In certain environments with a variety of seed types, African seedcracker finches exhibit disruptive selection. These finches have either large or small beaks, which allows them to exploit different types of seeds available in their habitat. Birds with medium-sized beaks are less efficient at cracking seeds compared to those with large or small beaks since they cannot specialize in either type. As a result, over time, the population diverges, leading to an increase in the frequency of both large and small beaked individuals, and a decrease in medium beaked birds, reflecting disruptive selection.
Both examples illustrate how different forms of natural selection can drive the evolutionary trajectories of populations based on their environments and available resources.