An isolated african canyon community in which cheetahs and leopards consume only impala antelopes is being observed. if the number of leopards increases, whichof the following change is most likely to be the first to occur after the leopard population increase? a. the impala population will decrease. b. the cheetah population will increase. c. the cheetah population will decrease. d. the impala population will remain the same.

Of the pollutants that form acids in the atmosphere, which is easiest to reduce? a. sulfur dioxide b. nitrogen dioxide c. ozone d. carbon monoxide

What are antigens and antibodies? how are they involved in the body’s response to incompatible blood?

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?