Biology, Eighth Edition (Raven)

Chapter 20: Genes Within Populations

Post Test

Relatively high levels of genetic variation have been found at the biochemical level (e.g. enzymes). This shows that: (p. 397)
A)there is variation among individuals for the different morphs of enzymes.
B)there are fitness differences among individuals based on the enzyme morphs.
C)selection must be occurring.
D)both a and b
Suppose there is a population of cats with the following numbers of genotypes; BB 50; Bb 20; bb 30. If the population is in Hardy-Weinberg equilibrium, then the numbers of the genotypes would be: (p. 398)
A)BB 30; Bb 50; bb 20
B)BB 50; Bb 10; bb 40
C)BB 16; Bb 48; bb 36
D)BB 36; Bb 48; bb 16
E)BB 50; Bb 20; bb 30
Pesticide resistance has evolved in over 500 species of pest. Resistance is likely to evolve in a species because: (p. 403)
A)some susceptible individuals are always missed by the pesticide application.
B)a few individuals have a mutation that confers resistance to that pesticide.
C)of genetic drift.
D)the pesticide does not work very well.
E)none of the above
Large female fish and frogs lay more eggs than small ones. Will there be continual selection for increased size in these population? (p. 404)
B)No, because there is a trade-off between size and survival; large individuals do not live as long as smaller ones.
C)No, because only a small proportion of eggs survive anyway because of predation, etc..
D)No, because egg production is not a genetically determined trait.
E)none of the above
Two or more alleles for a gene may be maintained in a population by the balance between: (p. 405 )
A)mutation and selection.
B)drift and selection.
C)selection and gene flow.
D)none of the above
E)all of the above
A few individuals of a new yellow morph of a species of waterboatman is introduced into a population. Its frequency increases to about 50% then remains constant. This is an example of: (p. 406)
A)directional selection.
B)negative frequency-dependent selection.
C)a balance between drift and selection.
D)positive frequency-dependent selection.
E)impossible to tell
It is observed in a population that the variance of a trait has decreased over time and then remains constant. This is likely the result of: (p.408)
A)directional selection.
C)stabilizing selection.
D)disruptive selection.
E)none of the above
Suppose that you found a new mutant type of guppy that had bright coloration but that was also extremely good at avoiding predation. You introduce a few of these into pools below waterfalls containing the pike cichlid predator and the drab form of guppy. What do you predict will happen? (p.411)
A)The new form will remain at low frequency.
B)The new form will completely replace the drab form.
C)The new form will increase to an intermediate frequency.
D)anything can happen
It is found that artificial selection to increase beak length in chickens also reduces skull thickness. This is an example of: (p. 412)
A)bad luck.
B)stabilizing selection.
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