Which embryonic cell layer develops into the lining of the gut in most eumetazoans?
a. mesoderm
b. epiderm
c. mesoglea
d. endoderm
e. ectoderm
ANSWER: d
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The fossil record documents ____, providing clear evidence of ongoing change in biological lineages
a. the occurrence of nonmorphologicalevolution b. the disconnect between living and extinct organisms c. disruptions in evolutionary processes d. continuity in morphological characteristics e. discontinuity in morphological features
When calcium levels rise, the __________ secrete(s)
__________, which __________ osteoclast activity. a. parathyroids; calcitonin; suppresses b. thyroid; calcitonin; suppresses c. thyroid; calcitonin; enhances d. thyroid; PTH; suppresses e. parathyroids; PTH; enhances
A population genetic study of a certain insect revealed four alleles for the GPI (glucose-phosphate isomerase) locus. How many different genotypic classes should be found?
A) 4 B) 8 C) 10 D) 16 E) 20
Uranium is a metallic element that is used in nuclear reactors and nuclear weapons. The vast majority of uranium found on Earth is in the form of uranium-238, an isotope with a mass number of 238, while the uranium that is used for nuclear reactors and weapons is uranium-235, an isotope with a mass number of 235. What is the atomic difference between uranium-235 and uranium-238?
A. uranium-235 has three fewer protons than uranium-238 B. uranium-235 has three fewer neutrons than uranium-238. C. uranium-235 has three fewer electrons than uranium-238. D. uranium-235 has three fewer atoms than uranium-238.