Mastering Biology Exam 2 Flashcards
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?
.09
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals that are heterozygous for this allele?
.32
In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?
.8
Evolution
can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.
If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of
both the first and third of these. (genetic drift & founder effect)
Which type of selection tends to increase genetic variation?
Disruptive selection
In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?
The value of a particular characteristic; characteristics of an organism can include such traits as size and color
True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.
False
Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in “neck wrestling” contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?
Directional selection
Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?
Stabilizing selection
Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?
Disruptive selection
Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?
Stabilizing selection
In evolutionary terms, an organism’s fitness is measured by its _____.
contribution to the gene pool of the next generation
Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.
directional selection
What is the only evolutionary mechanism that consistently leads to adaptive evolution?
natural selection
Sexual dimorphism is most often a result of
intersexual selection.
What is genetic drift?
A change in allele frequencies caused by random events
Why are the large finches now living on the Galápagos Islands different from the original source population from a nearby island?
All three answers are correct.
True or false? The last ice age produced many different species mainly because populations dispersed and colonized new habitats.
False
Which of the following statements about reinforcement is true?
Reinforcement is a type of natural selection.
A subset of a population of birds leaves its habitat on the mainland and colonizes a nearby island. The birds, after a period of time, become reproductively isolated. The island sinks and the population of birds that lived on the island returns to its original habitat. Which of the following statements about these bird populations is true?
The populations will not be able to interbreed because they are different species.
A population of birds colonizes an area in which the insects upon which they feed live inside trees. Which of the following events accounts for an observed increase in average beak size in the bird population over time?
Increased fitness of large-beaked birds, leading to natural selection
True or false? A flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopatric speciation.
True
Which of these is an example of temporal isolation?
One species is nocturnal, and the other species is not.
