Monthly Archives: August 2013

D.2b: Allopatric Speciation

evolution: defined as the cumulative change in the heritable characteristics of a population
alternate definition: a change in allele frequency over time
commonly accepted definition of species: biological species concept, which defines a species as a group of a potentially interbreeding populations, with a common gene pool that is reproductively isolated from other populations
speciation: formation of a new species by splitting of an existing species, when various barriers isolate the gene pool from one population, speciation occurs
allopatric speciation: when isolation occurs because of geographic separation of species


D.2a: Microevolution


gene pool: all of the genes in an interbreeding population at a certain time
alleles: varieties of a gene
polymorphic: if more than one allele is common in a population
balanced polymorphism: if two alleles carry a survival advantage on an organism, there is a high chance that the alleles will be carried on
allele frequency: a number between 0.0 and 1.0 indicates the proportion of a specific allele to all of the alleles of a gene in a population
sickle-cell hemoglobin: form of hemoglobin in which the shape can be altered in low-oxygen conditions, which disable the function of the hemoglobin
– shape of red blood cells that have hemoglobin can also be changed when there is low oxygen
– a transient polymorphism is not table because one of the alleles is less advantageous, and the allele goes extinct from the population caused by selection pressure


1) The number of yellow snails eaten decreased whereas the number of brown banded snails eaten increased. The yellow snails hit an all time low at the 10th day (time). And the brown banded snails started to increase greatly at the 9th day.
2) The color of the snails and the environment around it must have changed for the number of snails eaten to increase or decrease.
3) I do not think the two have interbred since the two separate colors have grown and shrunk at different times. Furthermore, the distinct colors of snails would not interbred since their offspring would not have an easy adaptation.
4) This is an example of transient polymorphism.  This is because one is not stable, and one of the alleles are less advantageous. And, the allele is removed from the population over time.