# 4.1: Natural Selection Lab

- Page ID
- 138518

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## Natural Selection

### Supplies Needed

- Calculator

### Readings

- Alveshere, Andrea J. 2019. Chapter 4: Forces of Evolution.
*Explorations.* - Coty-Barker, Valencia.
__How to Form a Hypothesis__.

### Introduction

### Steps

- Review dependent and independent variables, as well as key content from chapter four including natural selection, selective pressures, allele frequencies, and microevolution.
- Distribute student handouts. Students can work through the handout independently or in small groups.

### Conclusion

### Adapting for Online Learning

### References

### Image Attributions

## Natural Selection: Worksheet

### Step One: Hypothesis

- How do the ants vary?
- What is the selective pressure?
- What is the dependent variable?
- What is the independent variable?
- Now, write a hypothesis for the following question: During the rainy season, which allele frequency (brown or green) will increase over time?

### Step Two: The Rainy Season Data

#### Table 1: Number of ants collected during the rainy season

Generation of ants |
Brown ants |
Green ants |
Total ants |

Generation 1 | 100 | 100 | 200 |

Generation 2 | 90 | 120 | 210 |

Generation 3 | 75 | 150 | 225 |

Generation 4 | 65 | 170 | 235 |

- Calculate the number of brown alleles by multiplying the number of brown ants (from Table 1) by 2. Calculate the number of green alleles by multiplying the number of green ants (from Table 1) by 2. Write in Table 2.
- Calculate the total number of alleles by adding the number of brown alleles and the number of green alleles. Write in Table 2.
- Calculate the brown allele frequency by dividing the number of brown alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 2.
- Calculate the green allele frequency by dividing the number of green alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 2.
- Check your math by calculating the total allele frequency. Write in Table 2.

#### Table 2: Allele frequencies in the rainy season

Generation 1 |
Generation 2 |
Generation 3 |
Generation 4 |
|||||

brown | green | brown | green | brown | green | brown | green | |

Number of alleles | ||||||||

Total # alleles in generation (brown + green) | ||||||||

Allele frequency | ||||||||

Total allele frequency in generation (brown + green) |

- What was the general trend (comparing Generation 1 to Generation 4) of the brown allele frequency over the four generations? Did the brown allele frequency increase or decrease? Write the actual numbers for each generation here in support of your answer.
- What was the general trend (comparing Generation 1 to Generation 4) in the green allele frequency over the four generations? Did the green allele frequency increase or decrease? Write the actual numbers for each generation here in support of your answer.
- Was your hypothesis in Question 1 supported? Explain why or why not.

### Step Three: The Dry Season Data

- In this environment, which allele frequency (brown or green) do you hypothesize will increase over time?

#### Table 3: Number of ants collected during the dry season

Generation of ants |
Brown ants |
Green ants |
Total ants |

Generation 1 | 65 | 170 | 235 |

Generation 2 | 90 | 150 | 240 |

Generation 3 | 125 | 120 | 245 |

Generation 4 | 150 | 100 | 250 |

- Calculate the number of brown alleles by multiplying the number of brown ants (from Table 3) by 2. Calculate the number of green alleles by multiplying the number of green ants (from Table 3) by 2. Write in Table 4.
- Calculate the total number of alleles by adding the number of brown alleles and the number of green alleles. Write in Table 4.
- Calculate the brown allele frequency by dividing the number of brown alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 4.
- Calculate the green allele frequency by dividing the number of green alleles by the total number of alleles. Round to the nearest thousandths. Write in Table 4.
- Check your math by calculating the total allele frequency. Write in Table 4.

#### Table 4: Allele frequencies in the dry season

Generation 1 | Generation 2 | Generation 3 | Generation 4 | |||||

brown | green | brown | green | brown | green | brown | green | |

Number of alleles | ||||||||

Total # alleles in generation (brown + green) | ||||||||

Allele frequency | ||||||||

Total allele frequency in generation (brown + green) |

- What was the general trend (comparing Generation 1 to Generation 4) in allele frequency that you observed for the brown allele over the four generations? Did the brown allele increase or decrease in allele frequency? Write the actual numbers for each generation here in support of your answer.
- What was the general trend (comparing Generation 1 to Generation 4) in allele frequency you observed for the green allele over the four generations? Did the green allele increase or decrease in allele frequency? Write the actual numbers for each generation here in support of your answer.
- Was your hypothesis at the beginning of Step Three supported? Explain why or why not.

### Step Four: Wrap Up

- How did the ants in this population vary? In other words, what is the main difference between them?
- Why is variation necessary for natural selection to work?
- Explain selective pressure. What was the selective pressure in this simulation?
- What is the definition of allele frequency? How are allele frequencies related to the idea of evolution?
- Because some individuals in a population are more fit than others, the ultimate result of natural selection is a population that is better adapted to its environment. a. What trait was adaptive in the rainy season?

b. What trait was adaptive in the dry season?

c. Are your answers for a) and b) the same or different? If different, what changed between the two seasons to cause this difference? - Define microevolution. Define macroevolution. Which did you observe in this ant population? Explain why?