The ranges of black bears and brown bears overlap. However, black bears spend most of their time in the woods and
brown bears spend most of their time along the river. Which of the following best describes why black and brown bears
do not interbreed?
a. habitat isolation
b. temporal isolation
c. biological isolation
d. evolutionary isolation
e. environmental isolation
a
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A mutation in the gene encoding the enzyme that cuts F factor DNA during conjugation would result in
A. an inability to separate the recipient DNA from the donor DNA. B. an inability to draw the conjugated cells close enough to allow DNA transfer. C. the transfer of single-stranded DNA instead of double-stranded DNA. D. the inability of the donor DNA to move through the pilus. E. the inability of the recipient cell to replicate the F factor after transfer.
Chytrids are unique among fungi because they are the only ones that have ________
a. symbiotic relationships in lichens b. flagellated cells c. zygospores d. sexual reproduction
If adenine bonds with guanine, and thymine bonds with cytosine, the DNA molecule would
a. be constricted along its entire length. b. bulge where cytosine bonds with thymine. c. constrict where adenine bonds with guanine. d. partially constrict and partially bulge along its length. e. be highly reactive.
In birds, sex is determined by a ZW chromosome scheme that is much like the typical XY scheme seen in humans and many other organisms, except that the system is reversed:
Males are ZZ (similar to XX in humans) and females are ZW (similar to XY in humans). A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female? A) 1:1 male to female B) 3:1 male to female C) 1:2 male to female D) 2:1 male to female