In the southeastern U.S., two species of wild lettuce (Lactuca) do not usually form hybrids, because they bloom at different seasons. The means of isolation appears to be
A. prezygotic and mechanical.
B. prezygotic and temporal.
C. prezygotic and geographical.
D. postzygotic and ecological.
E. postzygotic and behavioral.
Answer: B
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The primary reservoir for calcium that is released during excitation-contraction coupling in a skeletal muscle fiber is
A. sarcoplasmic reticulum. B. endoplasmic reticulum. C. transverse tubules. D. Golgi bodies. E. troponin.
A self-regenerating action potential generally depends on opening of _______ channels.
Fill in the blank(s) with the appropriate word(s).
Which of the following is the only bacteria to photosynthesize by a pathway that produces oxygen as a by-product?
A. Eukaryotic bacteria B. Aerobic bacteria C. Cyanobacteria D. Protocells E. Archeans
If you wanted a grass plant to bend to the right, where would you want to apply auxin?
A. on the left side of the tip of the grass B. on the left side of the grass, a few centimeters down from the tip C. on the right side of the grass, a few centimeters down from the tip D. on the right side of the tip of the grass