What is genetic drift?
Random increase or decrease of alleles (alleles may increase or decrease by chance). In small populations, the effect can be very strong and influence evolution
What is the founder effect?
A type of genetic drift that occurs when allele frequencies in a group of migrating individuals are (by chance) not the same as the population of origin
What is the bottleneck effect?
A type of genetic drift that occurs when the population undergoes a dramatic decrease in size
What are some examples of causes of the bottleneck effect?
Natural catastrophe, predation, or disease. Destructive geological or meteorological events may also contribute
What is the movement of individuals between populations and what is the result?
Gene flow. The result is the removal of alleles from a population when they leave (emigration) and the addition of alleles when they enter (immigration)
What is an example of the founder effect?
The Amish community's large presence of the allele for polydactylism (more than five fingers or toes on a limb). The number of cases for this exceed the number of cases that occur in the world's remaining population
What are the four effects of genetic drift?
1). Significant in small populations 2). Allele frequencies change at random 3). Loss of genetic variation within populations 4). Harmful alleles may become fixed
What are the three effects of gene flow?
1). Reduces the genetic variation between populations 2). Results in two populations combining into a single population with a common gene pool 3). Affects adaptations to local environmental conditions
What is an example of gene flow?
Adaptational differences between birds born on different parts of an island that carry on throughout life
How are humans affecting gene flow?
The easier movement of people leads to mating with populations that had never before come in contact. This leads to an exchange of alleles and fewer genetic differences
Which form of genetic drift most likely accounts for the relatively high frequency of certain inherited disorders?
The founder effect