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Benchmark 5.
[spacer] 5F Evolution of Life #3
Natural selection provides the following mechanism for evolution: Some variation in heritable characteristics exists within every species, some of these characteristics give individuals an advantage over others in surviving and reproducing, and the advantaged offspring, in turn, are more likely than others to survive and reproduce....

5F Evolution of Life #4
Heritable characteristics can be observed at molecular and whole-organism levels in structure, chemistry, or behavior....

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Genetic Diversity

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Purpose

To develop an understanding of genetic diversity and how heritable characteristics can influence an organism's ability to survive and reproduce.

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Context

This lesson builds upon prerequisite middle-school benchmarks, especially the ideas that individual organisms with certain traits are more likely than others to survive and have offspring and that changes in environmental conditions can affect the survival of individual organisms and entire species. At the high-school level, students need to shift from thinking in terms of selection of individuals with a trait to changing proportions of a trait in populations.

In this lesson, students will look at genetic diversity and how it affects the survival of species. If the genetic diversity of a species becomes low, that species becomes increasingly at risk. There is a substantial amount of research related to the benchmark ideas in this lesson, and it is recommended that teachers familiarize themselves with these findings to help them guide student understanding.

Particularly relevant are the findings that students have difficulties understanding that changing a population results from the survival of a few individuals that preferentially reproduce, not from the gradual change of all individuals in the population. Explanations about “insects or germs becoming more resistant” rather than “more insects or germs becoming resistant” may reinforce these misunderstandings. (Benchmarks for Science Literacy, pp. 343-344 .)

Prerequisite skills: In order to complete this activity successfully, students need to have learned basic Mendelian genetics concepts. For example, they will be asked to use their knowledge of Punnett Squares to solve one of the challenges. 

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Planning Ahead

Materials:



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Motivation

Have students read the Why Does the Cheetah Lack Genetic Diversity? article on the Cheetah Conservation Fund website.

Then discuss the following questions:

  • Why is genetic diversity important? 
  • How did the cheetahs lose genetic diversity? 
  • How does the genetic diversity of cheetahs compare with that of other species of mammals?
  • What are some examples of genetic diversity in other species? In humans? In dogs? In cats?
  • How are zoos trying to increase genetic diversity in cheetahs?


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Development

This lesson is based on Why is Genetic Diversity Important?, a problem-solving activity from the Genetic Science Learning Center. This activity includes the Genetic diversity worksheet, on which students should record their answers.

Divide the class into small groups and have each group work through the four scenarios described in the activity. The scenarios involve a fictional species of bears (Pink-Eared Blue Bears) whose populations in a given environment have mutations that cause a variance in size. Students are asked to consider which variants are advantaged or disadvantaged due to differing scenarios, including the introduction of a new predator and extreme changes in climate.

In the final challenge, students are asked to decide what information they would need to know to preserve the genetic diversity of Pink-Eared Blue Bears' population.


After the groups have completed the activity, discuss the following questions with the class:
  • Did the advantageous characteristics for the blue bears remain the same in each scenario? How did they change, and why? 
  • What heritable traits are mentioned in the activity?
  • What is the interplay between heritable traits and environmental changes?


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Assessment

Using the information they developed in the final challenge in the activity, have each student complete the following assessment:

Pretend you are a conservation biologist who has been given the responsibility of managing the Pink-Eared Blue Bears' population. Write a letter to your supervisor in which you outline your plans to ensure the genetic diversity of the Pink-Eared Blue Bears' population.

Encourage students to refer to the more detailed background information that can be found in What is Conservation Genetics? on the Genetic Science Learning Center website.  

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Extensions
More detailed background information can be found in an article called Genetic Diversity on the World Resources Institute website.

For more information about genetic diversity in cheetahs, use the Saving the Cheetah: Race Against Time resource on the Smithsonian Institution Conservation and Research Center webpage. This site talks about what is being done to save the cheetah.

The following resources will help you extend the ideas in this lesson in the context of dog breeding:

 

Created :10/20/2001

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