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Case One | Case Two | Key Concepts

A current focus in science education is applying the science practices to real-world scientific scenarios. CSI Wildlife is a perfect tool to do just that. Students are guided through the analysis and interpretation of data, the use of computational thinking, and the evaluation of evidence to draw conclusions, as they explore two actual case studies (adapted to be approachable by students) in which scientists use DNA profiling to investigate the poaching of African elephants.

Case One provides a robust introduction to the methods of polymerase chain reaction, gel electrophoresis, and DNA profiling, as well as to conservation biology efforts. This case is strongly aligned to the objectives of the major biology curricula (NGSS, AP Biology, AP Environmental Science, and IB Biology). Case Two builds on that knowledge with additional links to more advanced curricula. Along with the science practices, students will experience the inherent connections between major content areas, such as molecular genetics, biotechnology, forensics, and conservation biology.

The cases investigated by students are based on recently published results (Wasser, S. K., Brown, L., Mailand, C., Mondol, S., Clark, W., Laurie, C., and Weir, B. S. Genetic assignment of large seizures of elephant ivory reveals Africa’s major poaching hotspots. Science, 349: 84-87, 2015) and the underlying data are available on the Dryad Digital Repository.

The maps of the African elephant range are based on data collected by different organizations and compiled by the International Union for Conservation of Nature (IUCN). The first high-quality, standardized survey of savanna elephants is currently being conducted through The Great Elephant Census project.

Case One

In Case One, students are introduced to the plight of African elephants and how the ivory trade causes poaching of this iconic species. Videos highlight scientists at work on these issues. Students learn how officials in Africa discovered 12 illegally harvested elephant tusks and want to know if the tusks came from a group of slaughtered elephants in a nearby national park. To solve the case, students first learn about the technique of DNA profiling, or fingerprinting, using variable regions of DNA called short tandem repeats (STRs). Students learn to interpret patterns from gel electrophoresis to determine the size of STRs for multiple markers and then determine the alleles present in individual elephants. Students apply what they learned to solve the case concerning the seized tusks and the slain elephants. After conducting the investigation, students explore how scientists use mathematics to estimate allele frequencies in populations and to make claims about the probability of two elephants in a population sharing the same genetic profile.

Case Two

In Case Two, students learn about another large shipment of elephant tusks seized from a shipping container that originated in Tanzania. The goal of the investigation is for students to use an understanding of elephant population genetics to determine the geographical origin of the slain elephants. Students first learn about how scientists determine genetic profiles of multiple individuals in multiple populations to create a reference genetic map that outlines allele frequencies for populations across a landscape. Students then apply what they learned to start to zero in on the location of the poached elephants. Determining the source location of the seized tusks is broken down into manageable problems for students that increase in complexity. After solving the case, student learn why conservation biology and genetic studies are so valuable for targeting law enforcement efforts to help reduce poaching and protect elephants.

Key Concepts

This activity addresses the following key concepts:

  • Variation (differences) in stretches of DNA can be used to identify individual organisms and relationships between populations.
  • Biological techniques such as the polymerase chain reaction and gel electrophoresis can be used to generate genetic profiles for individuals and populations.
  • Science contributes to society in many ways, including helping conserve wildlife.
  • Scientists use probability to determine the chances of two individuals sharing a genetic profile.
  • Scientists use empirical data and mathematical models to estimate allele frequencies in different populations across a geographic range.

Students will be able to

  • describe some of the major challenges facing African elephant populations;
  • describe how the process of DNA profiling or DNA fingerprinting works;
  • calculate the probability of two individuals sharing the same genetic profile;
  • analyze and interpret gel electrophoresis results to determine relationships between individuals and populations;
  • identify patterns in gel electrophoresis results to solve a crime scene;
  • explain the relationship between the geographical and genetic distance between two populations; and
  • describe how genetic data helps law enforcement officers and conservationists decide where to target their efforts.