Which mechanism is used to encourage the movement of water over gills?
a. beating of cilia
b. contraction of the diaphragm
c. relaxation of a muscular mantle
d. a fish swimming with its mouth closed
e. relaxation of body muscles
ANSWER: a
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Genetic drift will have a progressively larger impact on allele frequencies in a population as
a. gene flow increases. b. population size decreases. c. mutation rate decreases. d. the number of heterozygous loci increases. e. random mating increases.
The process by which undigested material is removed from the gastrointestinal tract is
A) secretion. B) urination. C) mechanical processing. D) elimination. E) absorption.
The nonporous, flexible central region of a tracheid wall pit in conifers is called
a. resin duct b. torus c. end wall d. sorus e. xylet
How do saltwater fishes conserve water?
a) Their kidneys produce small amounts of concentrated uric acid b) Their kidneys produce small amounts of concentrated urine c) Their kidneys produce large amounts of dilute urine d) they absorb extra water from their environment