Of the examples described below, which could NOT be used to test the idea that the feedback mechanism is in response to environmental conditions? A. Stomata on tobacco leaf opens in response to water and light signals B. A mountain climber starts to shiver, which warms him up. C. The arctic foxes have shorter extremities (tails, limbs, and ears) than the desert foxes to keep body heat retained more efficiently. D. Heart rate increases to provide more oxygen to the cells during an exercise.

Acommon kind of mechanical weathering is called

Using meiosis, the sporophyte produces spores that are .

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?