Which of the following is NOT a unique characteristic of chordates at some time in their life history?
Select one:
a. a dorsal notochord
b. a ventral hollow nerve cord
c. pharyngeal pouches
d. gill clefts
e. a postanal tail
d. gill clefts
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The types of bonds found in nucleic acids are:
A. phosphodiester bonds. B. peptide bonds. C. ionic bonds. D. non-polar covalent bonds.
Sodium has 11 electrons arranged in three energy levels. In order to become stable, sodium forms an ion with:
A. no charge. B. -1 charge. C. +8 charge. D. +1 charge. E. -8 charge.
Which of the following mechanisms are causal explanations for bird song?
A. Young males learned their song from their fathers. B. Songs are used by males to attract a mate. C. The ritualization of the vocalization became species specific. D. Air passing through a bird's specialized singing organ, the syrinx, vibrates the surrounding organs.
The most common etiologic agent of septic arthritis accounting for approximately 70% of infections is:
a. Streptococcus pyogenes. b. H. influenzae. c. S. aureus. d. Streptococcus mitis.