AP Biology : Evolution and Genetics
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Example Question #121 : Evolution And Genetics
Which of the following is true regarding speciation?
It is an outcome of evolution
Allopatric and sympatric speciation are two major types of speciation
Barriers to reproduction are critical in speciation
All of these
All of these
Speciation is a process in which one species diverges into two. Two major types of speciation are allopatric and sympatric speciation, with each type featuring a unique barrier to reproduction that halts genetic exchange between populations.
Example Question #1622 : Ap Biology
Which of the following is not an example of a reproductive barrier?
Two species of cicada live in the same area. Species A is sexually mature every 7 years. Species B is sexually mature every 2 years.
For a certain species of walrus, males defend large groups of females called harems. Typically, one male's harem will consist of about 20 females, and he will mate with all of them. Some male walruses don't have harems.
Horses and donkeys are different species, but can breed with each other to produce mules. However, mules are sterile (they cannot have offspring of their own).
Two species of birds live in the same area. Species A has dull gray plumage and has developed an elaborate courtship dance. Species B has vibrant orange plumage and has no courtship dance. Females from Species A choose mates based on their dance, and females from Species B choose mates based on their plumage.
For a certain species of walrus, males defend large groups of females called harems. Typically, one male's harem will consist of about 20 females, and he will mate with all of them. Some male walruses don't have harems.
A reproductive barrier is something that prevents two populations from interbreeding, eventually leading to speciation. The cicada populations are an example of temporal isolation--the two species do not interbreed because they do not breed at the same time. The horse and donkey example shows hybrid sterility--the two species can produce offspring, but the offspring cannot have offspring of their own. The bird species are an example of behavioral isolation--the two species have different courtship rituals (dance vs. plumage) which leads to minimal interbreeding.
Example Question #12 : Understanding Reproductive Barriers
Which of the following is an example of a post-zygotic reproductive barrier?
Two species of toads do not interbreed because one species breeds in the summer and the other breeds in the spring.
Two species of beetle do not interbreed because the males have different pheromones.
Two species of sticklebacks do not interbreed because one species lives in fresh water and the other lives in coastal estuaries.
A horse and a donkey breed successfully to produce a mule, which is sterile.
A horse and a donkey breed successfully to produce a mule, which is sterile.
A post-zygotic reproductive barrier occurs after fertilization has occurred. That is, the two individuals have already mated but either the offspring has died or it is sterile. A pre-zygotic barrier occurs before fertilization occurs. Pre-zygotic barriers are those that prevent individuals of different species from mating in the first place.
Example Question #13 : Understanding Reproductive Barriers
There was once a population on planet M311, called the Freg, who lived on a planet not unlike Earth. At the height of the Fregs technology and evolution, a collection of asteroids bombarded the planet and the devastation was so great that the planet was split in two, as was the Freg population. Much of the Freg population died, but many still survived on both pieces of M311.
Thousands of years ago, the environment on M311 was almost entirely dry and the Freg had evolved to suit that environment. Over time, the environment became more water-based and the Freg developed webbed feet and gills. However, as a result of the asteroid catastrophe, the climate returned to a more hot, dry, desert-like climate. As a result, the Freg began to to lose their webbed feet and gills. What is this process called?
Anti-evolution
Devolution
Amphibiatory genesis
Regressive growth
Hydrocorporeal restoration
Devolution
The correct answer to this question is devolution. Devolution refers to when a species reverts to an earlier, more primitive physical form as a result of environmental demands.
Example Question #1 : Understanding Hardy Weinberg Assumptions And Calculations
Which of the following is NOT an assumption required for Hardy-Weinberg equilibrium?
No migration
Population size must fluctuate
Random mating
No selection is occurring
No mutations
Population size must fluctuate
Hardy-Weinberg states that for a population to be in equilibrium, it must not be experiencing migration, genetic drift, mutation, or selection. By this definition, population size cannot fluctuate.
Example Question #1 : Population Genetics
According to Hardy-Weinberg calculations, a population's allele frequency will remain the same from generation to generation as long as evolution is not occurring. There are five conditions that must be met for equilibrium to remain in effect in a population.
Which of the following is not a condition for Hardy-Weinberg equilibrium to remain in effect?
The population must be large
Nonrandom mating must occur
No mutations may occur
No selection may occur
No gene flow may occur
Nonrandom mating must occur
Random mating must occur in the population in order for the equilibrium to remain. If nonrandom mating occurred, allele frequency in the population would change. The alleles frequency of those mating the most would increase, while that of those mating less would decrease.
Large populations must be used to minimize the effects of genetic drift. Mustations cannot occur, as these could introduce new alleles.
It is important to note that no natural populations exist in Hardy-Weinberg equilibrium. This is simply a theoretical tool.
Example Question #3 : Population Genetics
Imagine that a population is in Hardy-Weinberg equilibrium. A certain gene presents as two different alleles, and 49% of the population is homozygous dominant.
What percentage of the population is homozygous recessive?
51%
42%
9%
Further information is needed to solve the problem
9%
When a population is in Hardy-Weinberg equilibrium, we can quantitatively determine how the alleles are distributed in the population. P2 is equal to the proprtion of the population that is homozygous dominant based on the equation p2 + 2pq + q2 = 1. We also know that p + q = 1.
Since P2 = 0.49 in this case, we know that p is equal to 0.7. Since there are only two alleles for this gene, we know that the other allele, q in this case, is 0.3. Since homozygous recessive is referred to as q2 in the equation, we can plug in the value of 0.3 and determine that q2 = 0.09. As a result, we confirm that 9% of the population is homozygous recessive.
Example Question #1 : Population Genetics
In a population of fruit flies, the allele for red eyes is dominant to the allele for white eyes. If 50% the population is heterozygous and 25% is homozygous for white eyes, what is the frequency of the allele for red eyes?
We must remember our two equations for allele frequency, according to Hardy-Weinberg equilibrium.
We know that, in the first equation, each term represents a total percentage of homozygotes or heterozygotes. 
Using the information from the question, we can solve for 
The frequency of each allele is 0.50.
Example Question #1 : Population Genetics
The allele frequencies for a population displaying Hardy-Weinberg equilibrium were found to be 
For this question we are going to need to make use of the Hardy-Weinberg equilibrium equations. The equation we need to use is:
These numbers represent the percentages of each genotype found in a given population. We were given the values of 
After plugging the numbers into the equation, we can find the value of 
Example Question #1 : Population Genetics
A population of snails is in Hardy-Weinberg equilibrium. The snails come in two different colors: red, the dominant phenotype, and white, the recessive phenotype. There are sixteen homozygous dominant, forty-eight heterozygous, and thirty-six homozygous recessive snails.
What are the allele frequencies for this population?
We can solve this question using the Hardy-Weinberg equations:
In the second equation, 
We can find the values of 
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