The organisms of population a and population b are now incapable of interbreeding and producing offspring which biological process most likely caused this situation to occur

Which of the following is an example of this type of co-evolution

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Will someone me with this.. specialized cells which perform a particular function form: tissues organs or organism