Pollen grains are produced directly by
a. carpels.
b. mitosis.
c. meiosis.
d. stigmas.
e. pollen sacs
B
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The best terms for a fish whose body temperature varied between 4oC during the day when it is in deep, cold ocean waters and 26oC during the night when it comes to the surface to feed would be
A. endothermic and homeothermic. B. endothermic and heterothermic. C. ectothermic and homeothermic. D. ectothermic and heterothermic. E. ectothermic and endothermic.
Drosophila eggs acquire an initial asymmetry before fertilization as a result of
A. maternal DNA molecules being deposited in one end of the egg. B. nurse cell migration to one end of the egg. C. production of bicoid proteins in one end of the egg. D. attachments of cadherins to one end of the cell. E. maternal mRNA being deposited in one end of the egg.
Nitric oxide is a signal molecule that can
a. bind to surface receptors and activate second messengers. b. bind to surface receptors and open ion channels. c. diffuse across cell membranes and bind to receptors that regulate transcription. d. diffuse across cell membranes and directly alter the activity of intracellular enzymes.
Petals
A. produce pollen. B. enclose and protect the ovule. C. protect the developing flower. D. attract pollinators. E. are part of the gametophyte.