The rhizobia in root nodules fix ________, which accounts for ________ fixed annually on Earth
a. N2 / one-fourth of the N2
b. N2 / half of the N2
c. O2 / one-fourth of the O2
d. O2 / half of the O2
Answer: A
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Suppose the pair-rule genes were inactivated in Drosophila embryos. What is the likely result of the experiment?
A) The embryos would develop normally. B) The embryos would lack several segments. C) The embryos would have impaired anterior-posterior polarity. D) The embryos would have missing alternate segments.
Melatonin is secreted by
a. pancreatic islet cells. b. the thyroid gland. c. the pituitary gland. d. the pineal gland. e. the kidneys.
Cnidarians are __________, meaning they have two tissue layers
A. diploid B. protostomes C. diploblastic D. bilateral E. hermaphroditic
Which of the following is NOT a property/process of all living cells?
a. transcription b. differentiation c. evolution d. metabolism