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.
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.
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.