The basic unit of contraction in a skeletal muscle is the:
a. myofibril
b. sarcomere
c. muscle fiber
d. myosin filament
e. actin filament
b
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What do you think would result if nitrogen-fixing cyanobacteria populations suddenly declined?
A. Aquatic primary production would decline, particularly in regions not subject to fertilizer runoff. B. Legumes would cease to grow, but other types of plants would be unaffected. C. Both the aquatic and terrestrial populations of autotrophs would collapse. D. Populations of denitrifying bacteria would expand to take over their role, creating only a temporary disruption. E. More nitrogen would become available for other aquatic autotrophs.
Which of the following choices is not a function of the lymph vascular system?
a. delivers fats from food to the blood b. transports oxygen to cells and removes carbon dioxide c. returns water and plasma proteins to circulatory system d. transports cellular debris and pathogens to lymph nodes
Research published in January 2017 presented an estimate of the prevalence of HPV infection in American males at 45%. Adult males are an unvaccinated population. What are the consequences of HPV infection in males?
A. Males can develop genitourinary tract cancer from HPV infection. B. There are no long-term consequences; a course of antiviral medication will clear up the infection. C. HPV-infected males should also be screened for gonorrhea, as the two often co-infect. D. Males with HPV have a significantly higher likelihood of developing prostate cancer.
Root hairs grow actively in which area of the developing roots?
A. zone of maturation B. zone of elongation C. endodermis D. root cap E. zone of cell division