True or False? Natural selection will likely eliminate deleterious alleles more quickly with sexual reproduction than with asexual reproduction. - ANSWER True
Keypoint 15 - Sex creates genetic variation among offspring, enabling populations to adapt to environmental changes faster. - ANSWER
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Bio 182 Exam study
guide Correct 100%
True or False? Natural selection will likely eliminate deleterious alleles more quickly with sexual
reproduction than with asexual reproduction. - ANSWER True
Keypoint 15 - Sex creates genetic variation among offspring, enabling populations to adapt to
environmental changes faster. - ANSWER
True or False? In a rapidly changing environment, a population would likely benefit more from sexual
reproduction than from asexual reproduction. - ANSWER True
True or False? If a parent passes one copy of each chromosome to offspring, alleles on the same
chromosome would be inherited together. - ANSWER True
Use this information and your knowledge of biology to answer the following questions.
In the fruit fly, Drosophila melanogaster, a phenotype known as barred eyes sometimes appears, in
which the eyes are shaped like thin bars instead of being round. Additional crosses revealed that a
dominant allele on the X chromosome causes barred eyes. Oddly, however, the allele arises only when
two flies with normal eyes are crossed. In this case, fewer than 1% of the offspring will have barred eyes.
Male offspring never develop barred eyes. Researchers hypothesized that the allele forms when the X
chromosomes of a female cross over unequally during meiosis, leading to one long and one short
chromosome. This allele lies at a locus directly next to a locus called B but on the opposite end of the
chromosome from locus A.
If the researchers are correct, the X chromosomes likely cross over at the locus that controls normal or
barred - ANSWER True
After crossing over, both chromosomes will contain new alleles at the point of crossover.
, a. True
b. False
c. I don't know the answer - ANSWER True
What is the theory of evolution by natural selection - ANSWER stems from the observation that some
individuals in a population are more likely to survive longer and have more offspring than others. Thus,
they will pass on more of their genes to the next generation.
What is genetic drift? - ANSWER Populations can also evolve randomly through a process
By chance, some individuals have more offspring than others—not from an advantage conferred by
alleles, but just because some individuals happened to be in the right place at the right time (e.g., when
food was abundant).
Or even because other individuals happened to be in the wrong place at the wrong time (e.g., when a
predator was hunting).
Smaller populations evolve rapidly by genetic drift
Thus, a large population evolves more by natural selection than by genetic drift.
What is bottle neck effect? - ANSWER Any event that randomly eliminates a large fraction of a
population will magnify genetic drift (see figure below). Biologists use the term bottleneck effect to
describe this loss of genetic diversity following a sudden drop in a population. A bottleneck effect can
occur in a single generation when a small number of individuals survive a natural disaster. In one fell
swoop, the gene pool of the population becomes those alleles carried by the individuals that remain,
which may differ from the alleles carried by the individuals that disappeared.
What is the founder effect? - ANSWER the reduced genetic diversity that results when a population is
descended from a small number of colonizing ancestors.
, What are the three modes of selection? - ANSWER directional, disruptive, stabilizing
What is stabilizing selection? - ANSWER favors intermediate variants and acts against extreme
phenotypes
If the chromosomes crossed over equally, the resulting gametes would likely have the same number of
genes.
a. True
b. False
c. I don't know the answer - ANSWER True
An allele at locus A is more likely than an allele at locus B to remain linked to the allele for barred eyes.
a. True
b. False
c. I don't know the answer - ANSWER False
The allele at locus B is likely to be lethal when combined with the allele for barred eyes.
a. True
b. False
c. I don't know the answer - ANSWER False
, If the X chromosome crosses over with the Y chromosome, the resulting gametes are likely to generate
healthy offspring.
a. True
b. False
c. I don't know the answer - ANSWER False
What is disruptive selection? - ANSWER favors individuals at both extremes of the phenotypic range
What is directional selection? - ANSWER favors individuals at one end of the phenotypic range
Explain asexual reproduction - ANSWER in asexual reproduction, the offspring originates form a single
cell, yielding all cells produced to be identical.
it simply directs cells to divide and develop into new tissues and organs. This process takes time and
energy, but these resources go directly into the production of offspring
Explain sexual reproduction - ANSWER in sexual reproduction, two cells contribute genetic material to
the daughter cells, resulting in significantly greater variation. these two cells find and fertilize each other
randomly, making it virtually impossible for cells to be alike.
an organism must spend much more time and energy than that required to build an offspring. The
additional expense arises because sex requires a mate. Time and energy must be spent to find a suitable
partner and convincing that individual to share the genetic benefits of sex.
Explain courtship - ANSWER through which one sex (often, the male) convinces a member of the
opposite sex that a partnership would yield viable offspring.
Courtship can involve risky behaviors or expensive gifts, which signal the quality of the male's alleles to
his desired mate. Males end up paying dearly to court females because eggs are a limited commodity.
Sperm, on the other hand, is cheap and plentiful. One male could fertilize many females in a brief period
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