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Ch. 3: Exuberant Evolution in a Desert Fish Teacher Sheet

Ch. 3: Exuberant Evolution in a Desert Fish Teacher Sheet

Introduction

The "Exuberant Evolution in a Desert Fish" chapter explores the story of the pupfish and their adaptation to both freshwater and saline environments. This chapter explores evolution and how these fish have evolved rather quickly. This teacher sheet provides background information and answers to the questions on the student sheet.


There are many key terms introduced in this chapter that students may not be familiar with. If there are any terms missing on this sheet that you think the students should know, please add them. Use the resources provided to familiarize yourself with this chapter and the concepts presented. The takeaway points of this chapter include:

  • Due to human activity, these fish were moved from one area to another and scientists were then able to observe the adaptations for the fish to survive in both saline and freshwater environments. This provided a great example of evolution that occurred rather quickly. 
  • This chapter addresses the different species concepts out there and the disadvantages of them, hence why there are so many of them. The most common is the biological species concept in which a species is defined as those that can mate and produce viable offspring. For example, a horse cannot mate with an elephant, therefore they are different species. There are some exceptions to this rule in that, in some cases, different species can mate to produce viable offspring, such as a horse and donkey mating to produce a mule. This concept also does not apply to organisms that reproduce through asexual reproduction.
  • Genetic drift is brought up in this chapter. This is where usually a chance event occurs to change the gene pool of the originating population. For example, a bad storm comes through and a random subset of a population is killed and the organisms left now represent the gene pool. In these cases, usually the gene pool left is less diverse than before.    

Key Terms

  • Species – an individual; principal unit of evolution
  • Biological species concept – species are defined on their ability to reproduce and produce viable offspring with the same species (i.e., a giraffe and a horse couldn’t mate therefore they are different species)
  • Phenotypic species concept – species are defined based on shared physical characteristics
  • Genetic drift – random disappearance of genes in a population; resulting gene pool represents less genetic diversity than before
  • Phylogenetic species concept – species are defined based on a common ancestor; this is determined by looking at genetic material such as DNA and RNA
  • Natural selection – driving force of evolution; traits best suited to environment are selected for and over time populations evolve to have these traits as they are passed on to offspring
  • Speciation – generation of new species
  • Rapid evolution – evolution that occurs at a fast rate
  • Contemporary evolution – heritable changes within a few hundred generations
  • Gene flow – movement of genes between different populations through mating

Questions

1. In your own words, explain the dilemma in this chapter.

Answers may vary. Encourage your students to explain their answers.

2. What was the most interesting thing you discovered in this chapter?
Answers may vary. Encourage your students to explain their answers.

3. What was confusing?
Answers may vary. Encourage students to explain their answers.

4. What is the biological species concept? What would be some disadvantages of this concept?
The same species are ones that can produce viable fertile offspring with one another. One disadvantage is that this doesn’t apply to organisms that undergo asexual reproduction.

5. What is the phenotypic species concept? What would be some disadvantages of this concept?
This concept is basing the same species on physical appearance. Different species can look very similar but they are not the same species.

6. What is the phylogenetic species concept? What would be some disadvantages of this concept?
This concept is where species are defined based on a common ancestor and they are closely related based on their genetic information. The disadvantage is it splits species into smaller and smaller groups.

7. Name the four places the pupfish are found in and describe these environments. How do the pupfish morphologically differ in these environments?
Salt Creek (high salinity), Malpais Spring (freshwater), Lost River (high salinity, 3x more than ocean, desert landscape), Mound Spring (freshwater). In a saline environment, the pupfish had more of a streamlined body. In the freshwater environment, pupfish had a deeper body shape.

8. Research any additional information out there on the desert pupfish. How are these fish populations doing today?
Answers may vary. Encourage students to explain their answers.

This teacher sheet is a part of the Resurrection Science lesson.

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