The convergence in external morphology of sharks, penguins, and porpoises is attributed to
a. reduced genetic variability in these groups.
b. selection pressures that are common to these groups.
c. reproductive isolation of these groups.
d. identical genes in all three groups.
e. use and disuse of the limbs.
ANSWER: b
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Select all of the following that are names of immature stages in various animals.
_____ nauplius. _____ trochophore ._____ caterpillar. _____ nymph. _____ swimmeret.
Within an existing population, new alleles arise solely by ________
a. crossing over during meiosis b. mutation c. changes in chromosome number or structure d. independent assortment
As temperature increases, the rate of diffusion ________
a. increases. b. decreases. c. remains the same.
What is the advantage of the highly condensed state of the DNA of mitotic chromosomes?
a) The condensed state allows replication to occur more rapidly as the cell enters mitosis. b) The highly condensed state favors delivery of an intact package of DNA to each daughter cell. c) The condensed state favors DNA repair prior to mitosis. d) This state allows gene expression needed during mitosis. e) The condensed state allows chromosomes to fuse more easily.