True or False 15 Fossil evidence suggests that the earliest fishes were freshwat

Question

True or False 15 Fossil evidence suggests that the earliest fishes were freshwater chordates (craniates). 16 Ostracoderms provided the first undoubted evidence of bone in fishes. 17 The boneless condition of lampreys represents the secondary loss of ancestral bony armor. 18 According to the fin-fold theory, the predecessors of fins were lateral folds on each side of the a. TRUE b. FALSE a. TRUE b. FALSE a. TRUE b. FALSE presumably tadpole-like early fishes. The folds would be used as stabilizers while swimming. The fin- fold became subdivided into controllable segments, and eventually, the intermediate segments were lost, leaving the two standard sets of paired fins. This classic theory, however, may not fit recent observations of paired were not necessary as an intermediate stage and that pectoral and pelvic fins may have evolved independently a. TRUE . FALSE fins in fossil placoderms and modern fish embryos. These observations suggest that fin-folds Multiple Choice 19 Acquisition/evolution of hinged jaws in was one of the key events in the history of fishes/vertebrates, as it revolutionized the mode of feeding and led to the diversification of vertebrates. Hinged jaws of vertebrates evolved from the a. first two (most anterior) gill arches b. pharyngeal (5th and 6) gill arches penultimate and ultimate gill arches modified vertebrae of hypural arches c. d.

Explanation / Answer

15. True: young craniates lived in freshwater and then later migrated to the sea for breeding.

16.True: Ostracoderms were the first fishes whichdisplayed not only armor but also bones.

17. True: Lampreys represent the secondary loss of armor

18. True:It is thought the pectoral and the pelvic fin were developed during fin development by the presence of hox genes.

19.the first two anterior gill support/arches, therefore answer is option a.

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