How Can Evolution Be Observed in Mouse Populations? A typical rock pocket mouse is about 170 millimeters long from its nose to the end of its tail, shorter than an average pencil. And at just 15 grams, this tiny mouse weighs about as much as a handful of paper clips. You can find populations of rock pocket mice all over the Sonoran Desert in the southwestern United States There are two common varieties, or phenotypes-a light-colored variety and a dark-colored variety. There are also two major colors of substrate, or surface materials, that make up the desert floor. Most of the landscape consists of light-colored sand and rock, but patches of dark volcanic rocks that formed from cooling lava flows are found, separated by several kilometers of light colored substrate, Use the pdf posted on classroom to find the different cord locations of the mice for activity 1, and the link in the doc for activity 2. Remember to highlight or change font colors of your responses. Activity 1 1. View the images of the rock pocket mouse populations in each location and record the numbers for each color. Each location should have 12 mice. Card 1 Location A: Number of mice with light-colored fur Dark-colored fur Location B: Number of mice with light-colored fur Dark-colored fur Card 2 Location A: Number of mice with light-colored fur Dark-colored fur Location B: Number of mice with light-colored fur Dark-colored fur Card 3 Location A: Number of mice with light-colored fur Location B: Number of mice with light-colored fur Dark-colored fur Dark-colored fur Card 4 Location A: Number of mice with light-colored fur Dark-colored fur Location B: Number of mice with light-colored fur Dark-colored fur 2. Arrange the cards in what you think is the correct order from the oldest to the most recent. Write the order you chose: 3. What are the two types of substrate that these mice live on? 4. What are the two phenotypes found in these mice? 5. Suggest a reason for the differences in mice in those two areas:
The correct answer and explanation is:
Activity 1
To answer the questions in Activity 1, you’ll need to view the images and count the number of light-colored and dark-colored mice in each location for the cards provided. You will likely need to record the numbers and then follow the instructions to order them from the oldest to the most recent.
Suggested Answer for Activity 1:
- Record the Number of Mice in Each Location:
- Card 1: Location A: Number of mice with light-colored fur, Number of mice with dark-colored fur.
Location B: Number of mice with light-colored fur, Number of mice with dark-colored fur. - Repeat the same for all the other cards as described.
- Card 1: Location A: Number of mice with light-colored fur, Number of mice with dark-colored fur.
- Arrange the Cards:
- Once you’ve recorded the numbers from all cards, you’ll want to place the cards in an order you think represents the evolutionary changes. This order should reflect which phenotype was more common at each time and how it might have shifted.
- Types of Substrate:
The two types of substrate that these mice live on are light-colored sand/rock and dark volcanic rocks. - Two Phenotypes:
The two phenotypes found in these mice are light-colored fur and dark-colored fur.
Suggested Answer for Activity 2:
The rock pocket mouse populations in the Sonoran Desert are a great example of natural selection in action. In this desert, the color of the fur on the mice directly impacts their survival. The two types of substrate, light-colored sand/rock and dark volcanic rocks, create a contrasting environment for the mice, with their fur color providing camouflage from predators.
Suggested Explanation (300 words):
The differences in the mouse populations across these two substrates can be explained by the concept of natural selection. The light-colored fur phenotype of the mice is better suited for survival in areas with light-colored sand and rocks, where they can blend into their environment, making it harder for predators (like hawks and owls) to spot them. Conversely, dark-colored mice are better camouflaged against the dark volcanic rocks, allowing them to survive in those areas by being less visible to predators.
Over time, mice with fur colors that match the substrate in their environment are more likely to survive and reproduce. In areas with dark volcanic rocks, dark-colored mice are more likely to survive and pass on their traits to their offspring. Similarly, in areas with light-colored sand and rocks, light-colored mice are favored.
This example illustrates how evolutionary pressures, such as predation and environmental factors, shape the genetic diversity of populations over time. Natural selection favors individuals with advantageous traits, such as fur color that helps them blend into their environment, leading to an increase in the frequency of these traits in the population. Over generations, this can result in the population adapting to its specific habitat, with a higher proportion of mice in each area exhibiting the fur color that best suits their survival in that particular environment.