Teaching about Bottleneck Genes

While interning at the International Crane Foundation, it was my responsibility to lead tours and educate visitors about cranes and the habitat on which they depend. The existing tours focused on general crane habitat, diet, morphology, and the history of the Whooping Crane including the species’ journey back from the brink of extinction and into recovery. After leading this tour several times, I saw an opportunity.

When discussing dwindling populations and extinction, many visitors were able to articulate that a small population is bad for a species. But when I tested their knowledge, and inquired as to why small populations are bad, not many could explain beyond offering 'that a hurricane could wipe out the whole population' which is valid, but only part of the story. In reality, a dwindling population put species at an exponential risk of extinction.

Diversity is essential to the survival of a species. Diversity within a population means that there are enough organisms to continue to producing a variety of genetic combinations within a group.  In the world of “survival of the fittest,” an organism must have the genetic resources that allow it to survive immediate changes in its environment and that allow the species to adapt to long-term changes around it. The only way to ensure this will happen is to make sure that genetic choices in the population are large enough to have the greatest variety of attributes passed along to individuals in the next generation. The best way to ensure a large and healthy population with enough gene choices is to have sufficient habitat to support it. When the number of individuals decreases, the genetic pool also decreases, causing what is called a “bottleneck” in the population, or a limited variety in gene diversity.

To address this gap in knowledge, I created a new program to help explain genetic bottlenecks and the importance of species diversity.

Essentially the game breaks down to this, we have a jar of different colored pony beads. Each participant gets a small number of pony beads which represent an individual crane or a crane population (depending on the size of the group). The color of each bead corresponds to a simplified genetic trait. The participant(s) are then faced with a variety of challenges Whooping Cranes might face in the wild; disease, predators, drought, human intrusion into habitat, etc. Then they are encouraged to discuss how their crane(s) would fair, given the situation at hand.

The purpose of this activity is to demonstrate the importance of genetic variability to health within a species and how this diversity facilitates adjustment to ecosystem changes. Students will simulate what happens when a population of Whooping Cranes begins to decrease in size, and they will examine how this decrease affects the gene diversity within the group. Following the simulation, students will look at the effects of a limited gene diversity, or pool, on the population in a changing ecosystem over the period of a year.

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