Assignment task: Evolution and its Mechanisms
INSTRUCTIONS: Answer the following three questions for each of the five evolutionary scenarios.
- Identify the mechanism of evolution at play in the scenario.
- What key element within the scenario description helped you identify the mechanism?
- Describe how the evolutionary mechanisms impact the traits present in the population(s).
Mechanisms of Evolution:
- Gene Flow
- Genetic Drift - Founder Effect
- Genetic Drift - Bottleneck
- Natural Selection
Current genetic evidence has demonstrated that 1 - 4% of the DNA of modern humans is shared with Neanderthal hominins. This indicates that during the modern human migration out of Africa (c. 65,000 years ago), they encountered and interbred with the robust Archaic hominin Neanderthals in the Middle East and beyond.
The Cajuns are descended from 300 French Canadians who moved to Louisiana from the Acadia region (the area around modern Nova Scotia). These immigrants carried the Tay-Sachs allele in their gene pool. Tay-Sachs is a genetic disorder that causes gradual destruction of nerve cells in the brain and spinal cord. Since the Cajun community was established, it has remained relatively isolated with its members often marrying people who are more closely related to them than would be seen in the general US population. The incidence of Tay-Sachs in Cajun populations is exceptionally high, 1 in every 3,500 newborns are affected by the condition. In the broader US population, the incidence of Tay-Sachs is about 1 in 320,000 newborns.
The sickle cell gene mutation in human populations appears in high frequencies in areas of Africa where malaria parasitic infections are common. This genetic mutation makes those with the condition resistant to malaria. If an individual with the sickle cell mutation contracts malaria, they do not die from it.
In the 1530s the Spaniards made contact with the Inca Empire and brought the smallpox virus with them. Having no immunity to this European disease, 60 - 94% of the Incan population was wiped out in just a few years. The genetic diversity in the surviving Incan population was dramatically reduced.
In January 1946, the US Army officially began "Operation War Bride." The operation provided transport to the US for the foreign wives and babies of US WWII servicemen stationed in Europe and the Pacific. It is estimated that as many as 1 million women from 50 countries wed Americans during the war or the occupation that followed.