Which cells have the lifespan of approximately 7.5 days and one-third of their population remains in the spleen (unless needed to fight significant bleeding)?

Platelets

Explanation:

Platelets have a lifespan of approximately 7.5 days. Two-third of their population circulate in the blood and contribute to homeostasis. The remaining one-third is stored in the spleen, where they remain unless needed in cases of severe bleeding.

using the scientific method.

world war i had a devastating effect on german-americans and their cultural heritage. up until that point   german-americans, as a group, had been spared much of the discrimination, abuse, rejection, collective mistrust experienced by so many different racial and ethnic groups in the history of the united states. indeed, over the years, they had been viewed as a well integrated and esteemed part of american society. all of this change with the outbreak of war.