Let’s talk Tasmanian devils. (Not the cartoon character, the marsupial native to Australia). You may have heard how Tasmanian devils have been driven to the brink of extinction by an infectious cancer that scientists first noticed in 1996. The cancer spreads through bites, which are common in these aggressive animals, and creates massive facial tumors. These tumors grow so large that they eventually cause the devil to suffocate or starve. However, there’s new hope for these amazing animals, and it’s a story of modern day natural selection.

“Tasmanian Devil” by Chen Wu is licensed under CC BY 2.0

As recently reported in Science News for Students (Say, 2016), there are some Tasmanian devils that can survive even after exposure to the cancer. After studying the genes of these survivors, scientists have found variations in DNA that are more common in the surviving population of than in the original population. Scientists think that the devils with these DNA sequences were more likely to survive long enough to reproduce, thus increasing the frequency of these genes in the population. Scientists still don’t know which of the genes might be the most important in helping the devils survive the cancer or even how they work. However, the search is on to find out more about these “resistance genes” and save the Tasmanian devils from extinction.

Say, T. (2016, Oct 17). Tasmanian devils begin to resist infectious cancer. Science News for Students. Retrieved from https://www.sciencenewsforstudents.org/article/tasmanian-devils-begin-resist-infectious-cancer

5-E Integration

• Engage: Often we introduce students to natural selection using historical examples that reinforce the misconception that natural selection is something that only happened in the past. Alternatively, use the story of the Tasmanian devils to ground class discussion about natural selection in the present. Use the map provided in the Science News for Students article to introduce the narrative around the discovery of the infectious cancer and the scientists’ search to find out key differences in the devil population before and after the cancer arrived.

• Elaborate: After learning about natural selection in another context, have students read the article and explain how natural selection is producing a change in the Tasmanian devil populations.

Related Standards

TEKS 7.11 Organisms and environments. The student knows that populations and species demonstrate variation and inherit many of their unique traits through gradual processes over many generations. The student is expected to:

• (C) identify some changes in genetic traits that have occurred over several generations through natural selection and selective breeding such as the Galapagos Medium Ground Finch (Geospiza fortis) or domestic animals.

TEKS 7.14 Organisms and environments. The student knows that reproduction is a characteristic of living organisms and that the instructions for traits are governed in the genetic material. The student is expected to:

• (A)  define heredity as the passage of genetic instructions from one generation to the next generation;
• (C)  recognize that inherited traits of individuals are governed in the genetic material found in the genes within chromosomes in the nucleus.

TEKS Biology.7 Science concepts. The student knows evolutionary theory is a scientific explanation for the unity and diversity of life. The student is expected to:

• (C)  analyze and evaluate how natural selection produces change in populations, not individuals;
• (D)  analyze and evaluate how the elements of natural selection, including inherited variation, the potential of a population to produce more offspring than can survive, and a finite supply of environmental resources, result in differential reproductive success;