The risk for Down syndrome increases ____
a. when the mother is over thirty-five years old
b. when the father is over thirty-five years old
c. when the father is over fifty years old
d. for dizygotic twins
e. for monozygotic twins
a
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Caterpillars of the same species on a large leaf each chew as much leaf as they can. This is an example of
A. amensalism. B. interference competition. C. exploitation competition. D. commensalism. E. interspecific competition.
Parasitic helminths have a highly developed ________ system to enhance host transmission.
A. nervous B. reproductive C. respiratory D. digestive E. muscular
UV light _____ vitamin D.
A. decreases the body's production of B. increases the body's production of C. destroys existing D. has no effect on E. alters the structure of
Which of the following are parasites?
a. some pathogensi b. a few birds c. a few plants d. some flatworms and roundworms e. all of these