The presence of the immune complexes leads to the activity of the neutrophils. What factor links these two?
A. complement
B. cytokines
C. mast cells
D. helper T cells
Answer: A. complement
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Four of the five glands listed below belong to the
endocrine system. Select the exception. a. thymus b. salivary c. parathyroid d. thyroid e. pituitary
Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A. Natural selection cannot account for losses, only for innovations. B. Natural selection accounts for these losses by the principle of use and disuse. C. The ancestors of these organisms experienced harmful mutations that forced them to find new habitats that these species had not previously used. D. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
Sometimes, splitting of the pre-embryo is incomplete during the development of twins, and ________ twins result
Fill in the blank(s) with correct word
What factor most limits a person's maximal increase in cardiac output during exercise?
A. The time it takes for electrical impulses to reach all parts of the heart B. The time available to fill the heart chambers with blood as the heart rate increases C. The total amount of blood in an individual D. The rate at which cardiac muscle contracts E. The rate at which oxygen is delivered to the cardiac muscle cells