A terrarium is a small, enclosed ecosystem. If you change certain aspects of the terrarium, the climate that exists inside it will also change. Examine the image of a terrarium. Then identify one attribute of the terrarium that you could change to alter the climate inside. How would this change mimic the climate changes that we see on Earth?

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?