Bottleneck Genes lab
Names: _______________________________________________________________
Background
Diversity is essential to the survival of a species. The ability for an individual to survive
changes in the environment comes from the extent of genetic diversity the individual has,
giving it the ability to adapt to those variations. Diversity within a population means that
there are enough organisms to continue producing a variety of genetic combinations
within the group.
In the world of “survival of the fittest,” organisms must have the genetic resources that
allow it to survive immediate changes in its environment and for the species to adapt to
long-term changes around it. The only way to ensure this will happen is to make sure
that the genetic choices in the population are large enough to have the greatest variety of
attributes passed along to individuals in the next generation. 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.
A specific example of a bottleneck has occurred with South Dakota’s
native species, the black-footed ferret. Black-footed ferrets belong to
the family of animals called the mustelids along with skunks, weasels,
badgers and other like animals. Black-footed ferrets’ diet consists of
about 90% prairie dogs and often they will then use their burrows. The
ferret also prefers short grass prairies so
that they can see approaching predators
better. At one time the range of the blackfooted ferret went all the way from
Canada down to Texas (see map), but due
to the loss of habitat and the extermination
of prairie dogs the black-footed ferret has
become one of the most endangered
mammals of North America. They
became so rare in fact, that in 1979 they were declared
extinct until a dog brought a ferret it had killed to a farmer
in Wyoming two years later. A small population of only
129 ferrets was found but in 1985 the sylvatic plague hit the
population and it was reduced to only 18 black-footed ferrets in the world! (Severe
bottleneck) Since that time, efforts are being made to increase the population through
captive breeding programs and releases to the wild. The most successful places to release
these animals have been in two counties in South Dakota.
Your job will be to see how a bottleneck affects the Black-footed ferret populations
ability to survive in a variety of environmental situations.
Key to Genetic Characteristics for the Black-Footed Ferret:
Green = Camouflage
Purple = Accurate sense of smell
Red = Healthy jaw formation
Black = Acute hearing
Orange = Immunity to sylvatic plague
Blue = Precise Vision
Pink = Strong claws and forearms
White = Agility
Yellow = Healthy rate of reproduction
1. On your key to Genetic Characteristics, circle which beads/genes your population
received through the bottleneck.
2. Calculate the percentage of genetic diversity of your population.
One of each type of gene/bead (9 of 9) represents 100 percent genetic diversity in
the original population.
_______ gene types received/ 9 original gene types = _______ x 100 = _______%
3. List the genetic characteristics (colors) your population received through the
bottleneck.
4. List the genetic characteristics your population lost when it came through the
bottleneck.
5. Draw three environmental situations from the bag, write a prediction about what
happens to your population during the coming year. Consider the following in
your answer: Is the population genetically equipped to survive in its environment?
How well or how poorly? How does a high or low percentage of genetic diversity
affect the population’s survival? How do random changes in the environment
affect the populations?
Situation # ______:
Situation # ______:
Situation # ______:
Discuss the following questions:
6. Why does gene diversity help protect a population?
7. Why would a smaller population have a higher risk of being eliminated than a
large population?
8. Why do you think smaller populations have a harder time surviving disease?
9. Why do recessive traits (need two recessive genes) become more prevalent in
bottlenecked populations where interbreeding (mating with close relatives)
becomes necessary to continue the population?
10. Do a little research and discuss how bottleneck has affected the cheetah
population.
(Adapted from the Project WILD K-12 Curriculum and Activity Guide. Bottleneck Genes.)