Which of the following best explains why the diversity of organisms decreases as you move from shallow seas to deep oceans? The levels of oxygen in the deep ocean are too high for many organisms to thrive.
The low temperatures of the deep ocean would freeze most organisms.
The salinity of the deep ocean is too high for most organisms to live.
The lack of sunlight in the deep ocean limits the types of organisms that can survive.

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?