10.3 Speciation Flashcards
What is a gene pool?
A gene pool represents the sum total of alleles for all genes present in a sexually reproducing population
What does a large gene pool indicate?
A large gene pool indicates high amounts of genetic diversity, increasing the chances of biological fitness and survival
What does a small gene pool indicate?
A small gene pool indicates low amounts of genetic diversity, reducing biological fitness and increasing chances of extinction
What can gene pools be used to determine?
Gene pools can be used to determine allele frequency – the proportion of a particular allele within a population
What is evolution?
Evolution is the cumulative change in the heritable characteristics of a population across successive generations
What reflects evolution in gene pools?
This requires that allele frequencies change within the gene pool of the population to reflect these evolving characteristics
What 5 key processes may lead to a change in allele frequency
mutation
gene flow
sexual reproduction
genetic drift
natural selection
What is mutation?
A random change in the genetic composition of an organism due to changes in the DNA base sequence
What is gene flow?
The movement of alleles into, or out of, a population as a result of immigration or emigration
What is sexual reproduction?
Sex can introduce new gene combinations and alter allele frequencies if mating is assortative
What is genetic drift?
The change in the composition of a gene pool as a result of a chance or random event
What is natural selection?
The change in the composition of a gene pool as a result of differentially selective environmental pressures
When will genetic drift be faster and more significant?
It will occur faster and be more significant in smaller populations, where chance events have a bigger impact on the gene pool
Why is genetic drift not as significant in larger populations?
Larger populations will be less affected by random events and maintain more stable allele frequencies with low genetic drift
When do allele frequencies change significantly?
Allele frequencies will change significantly when a large population is reduced to a small population
By what two mechanisms may allele frequencies change significantly?
Two mechanisms by which this population change may occur are via population bottlenecks and the founder effect
When do population bottlenecks occur?
Population bottlenecks occur when an event reduces population size by an order of magnitude (~ >50%)
What may bottlenecks be a result of?
These bottlenecks may result from natural occurrences (e.g. fires, floods, etc.) or be human induced (e.g. overhunting)
What does the surviving population exhibit in terms of genetic drift? (bottleneck)
The surviving population has less genetic variability than before and will be subject to a higher level of genetic drift
How will the gene pool vary over time? (bottleneck)
As the surviving members begin to repopulate, the newly developing gene pool will be divergent to the original
What is an example of population bottlenecks?
Example: Northern elephant seals have reduced genetic diversity compared with southern seals due to overhunting
When does the founder effect occur?
The founder effect occurs when a small group breaks away from a larger population to colonise a new territory
What is the small group more subject to? founder
As this population subset does not have the same degree of diversity as a larger population, it is subject to more genetic drift
Consequently, what will happen to the gene pool of the small group? founder
Consequently, as this new colony increases in size, its gene pool will no longer be representative of the original gene pool