Mike grows vegetables on his farm. the tomatoes that he grows are of good quality, but they are small. what can he do to increase the size of the tomatoes?
a) spray the plants with abscisic acid.
b) spray the plants with gibberellins.
c) spray the plants with ethylene.

Lucia is walking barefoot in her yard. she accidentally steps on a nail. how will her nervous system work to generate a reaction? arrange the eventschronologically.

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.

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?