Some plants on the coast of the ocean have the unique ability to take in salt water. marsh plants are able to take in the salt water and separate the salt so that they can use the water for photosynthesis. they then excrete the salt onto the surface of their leaves. this trait allows them to survive in a place where many other plants cannot- this is an example of: speciation mutation variation adaptation

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?