However, if one of the alleles is deleterious in the homozygous form, then this will lead to more exposure of the allele in the deleterious phenotype, and the frequency of this allele will eventually decline to zero. So, over time inbreeding is likely to lead to a decrease in both allele and genotype frequencies. No, there are many other reproductive barriers that can develop among different species. Give an example of each of the three premating isolating mechanisms, and the four postmating isolating mechanisms between species. Sperm transfer, but sperm dies before fertilization.
Fertilization occurs by zygote dies.
Explain the differences between the three modes of speciation. Subpopulations then undergo different process of Genetic Drift and mutation accumulations, leading to different selection pressures within both subpopulations. This process will eventually lead to speciation over many generations if there is little or no gene flow. A difference in selection pressure along a cline can lead to speciation over many generations, particularly if there is a sharp change in phenotype success across one section of the cline. If this leads to a relatively small zone of hybridization between the two subpopulations, then speciation is more likely to occur.