What is a tree in a food chain with a tree catepillar and a bird

Beth’s hygrometer is reading a temperature of 30 c and a relative humidity of 65%. the humidity in the air is?

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

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?