Why are valves important in veins?
What will be an ideal response?
Valves prevent backflow. Because pressure in the veins is rather low, gravity can cause backflow. With one-way valves, if skeletal muscle contracts and pushes against veins, blood can only flow in one direction and cannot flow back when the muscles relax.
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A. competition B. predation C. obligate mutalism D. facultative mutalism E. commensalism
Which type of forensic evidence was available for scientists studying the case of the Romanovs?
A) fingerprint B) toxicology C) DNA D) footprint
Where in a host's body do most typical tapeworms live and reproduce?
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Which physician realized that doctors were causing maternal deaths by failing to wash their hands while assisting during childbirth?
A) Girolamo Fracastoro B) Joseph Lister C) Louis Pasteur D) Ignaz Semmelweis