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Bio 182 Exam study guide/168 Answered Questions Distinction Graded
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Bio 182 Exam study guide/168 AnsweredQuestions Distinction Graded
True or False? Natural selection will likely eliminate deleterious alleles more
quickly with sexual reproduction than with asexual reproduction. - -True
-Keypoint 15 - Sex creates genetic variation among offspring, enabling
populations to adapt to environmental changes faster. - -
-True or False? In a rapidly changing environment, a population would likely
benefit more from sexual reproduction than from asexual reproduction. - -
True
-True or False? If a parent passes one copy of each chromosome to
offspring, alleles on the same chromosome would be inherited together. - -
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 - -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 - -True
-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 - -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 - -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 - -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 - -False
-What is the theory of evolution by natural selection - -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? - -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? - -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? - -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? - -directional, disruptive, stabilizing
-What is stabilizing selection? - -favors intermediate variants and acts
against extreme phenotypes
-What is disruptive selection? - -favors individuals at both extremes of the
phenotypic range
-What is directional selection? - -favors individuals at one end of the
phenotypic range
-Explain asexual reproduction - -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 - -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.
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