Arthropod exoskeletons are composed primarily of

A. chitin.
B. calcium carbonate.
C. collagen.
D. cartilage.
E. sclerotin.


A. chitin.

Biology & Microbiology

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Which of the following is not an impact of acid

rain? a. It stops fish egg development b. It can burn foliage. c. It releases toxins in the soil. d. It causes eutrophication e. It can kill adult aquatic organisms

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RNA interference functions by

A) degrading the protein encoded by a specific mRNA. B) degrading the RNA strand that is encoded by the Slicer gene. C) transcribing double-stranded RNA into protein. D) disrupting the chromosomal copy of the gene. E) degrading the RNA complementary to the short, double-stranded RNA.

Biology & Microbiology

Which of the following are arranged in the sequence in which the various taxa first appeared in time?

A. prokaryotes, protists, mosses, streptophytes, conifers, ferns, angiosperms B. prokaryotes, protists, streptophytes, mosses, ferns, conifers, angiosperms C. bacteria, streptophytes, protists, mosses, angiosperms, cycads D. protists, prokaryotes, streptophytes, ferns, mosses, angiosperms, conifers E. bacteria, protists, liverworts, lycophytes, streptophytes, angiosperms, gnetophytes

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What is the process in which impulses jump from node to node?

A. Incomplete transfer B. Saltatory conduction C. Repolarization D. Refractory action E. Facilitated transmission

Biology & Microbiology