The sessile stage of many cnidarians is a
A. larva.
B. polyp.
C. medusa.
D. zygote.
B. polyp.
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Should a genetic abnormality arise, ________ prevent a cell from progressing uncontrollably through the cell cycle.
A. cis-acting elements B. checkpoint proteins C. trans-acting elements D. growth factors E. Ras's
The ________ is the site where lipids, triglycerides, and steroids are synthesized, as well as where calcium is stored within the cell.
A) lysosome B) smooth endoplasmic reticulum C) nucleolus D) mitochondria E) rough endoplasmic reticulum
A primary immune response is the ________
A) production of primary-type antibodies in the first day of exposure to a microorganism
B) immune response elicited by the second exposure of lymphocytes to a particular antigen
C) immune response elicited by the first exposure of lymphocytes to a particular antigen
D) immune response elicited by the first exposure of memory cells to a particular antigen
Many species of snakes lay eggs, but in the forests of northern Minnesota where growing seasons are short, only live-bearing snake species are present. This trend toward species that perform live birth is an example of
A) natural selection. B) sexual selection. C) species selection. D) goal direction in evolution