AP Biology : Identify evolutionary change mechanisms

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #251 : Evolution And Genetics

What conclusion did Darwin draw from the finches he observed at the Galapagos Islands?

Possible Answers:

Birds reserve a herd mentality, and will aspire to remain similar in appearance to one another.

The larger organisms have a large advantage in nature and will out-compete the smaller organisms.

Finches will all live in the same area of a tree, regardless of species type.

Organisms will evolve in order to fill unoccupied niches in their environment.

Correct answer:

Organisms will evolve in order to fill unoccupied niches in their environment.

Explanation:

Darwin observed that the finches found on the Galapagos had adapted different sized beaks to eat different diets. By doing this, the birds had evolved to eat diets that would be inedible by other finches. This concept of a "niche" means that different species will exploit and use their environment in different ways.

Example Question #233 : Evolution And Genetics

Which of the following was not part of Darwin's theory of evolution?

Possible Answers:

Organisms of the same species display a variety of different traits

None of these - Darwin did not develop a theory of evolution

Organisms that are best adapted to their environments are most likely to survive and reproduce

Over time, traits that are beneficial to an organism in a given environment are likely to accumulate in a population

The inheritance of traits in discrete units called alleles

Correct answer:

The inheritance of traits in discrete units called alleles

Explanation:

The inheritance of traits through discrete units called alleles was not a part of Darwin's theory of evolution. A monk named Gregor Mendel developed the theory of inheritance through alleles. Darwin's theory did not propose a method of inheritance, and Darwin was unaware of Mendel’s work. The works of Darwin and Mendel were later combined by scientists to create the modern theory of evolution.

Example Question #251 : Evolution And Genetics

Charles Darwin is well-known for his work on Galapagos finches. He found that the finches' beaks had different sizes and shapes that corresponded to their preferred food source. Which of the following phenomenon does this best illustrate?

Possible Answers:

Acclimation

Stabilizing selection

Adaptation

Heredity

Correct answer:

Adaptation

Explanation:

The finches' beaks are highly adapted to their preferred diet. Therefore, this is an excellent example of adaptation. Acclimation occurs on a very short-term basis and does not apply to speciation. Stabilizing selection decreases the amount of genetic diversity among a population, and does not promote speciation as seen among finches. Heredity is simply the degree to which a parent's genes are passed to its offspring and is not demonstrated by this example.

Example Question #1 : Identify Evolutionary Change Mechanisms

The various species of Galapagos finches utilize their beaks to access food resources in many ways. Those with longer beaks use their beaks to penetrate cactus fruit and eat the inside, while those with short beaks tear apart the base of the cactus and eat insect larvae and pupae.

Cacti in the Galapagos fail to produce any fruit for several generations, causing finches with long beaks to die. With these environmental changes, selection will favor those with short beaks over those with long beaks. What type of selection is described?

Possible Answers:

Sexual selection

Disruptive selection

Stabilizing selection

Directional selection

Correct answer:

Directional selection

Explanation:

The answer is directional selection. This environmental change will cause a shift in the mean beak size of the population towards smaller beaks because their food resource was not affected. There is selection against long beak size only.

Example Question #241 : Evolution And Genetics

Which of the following is an outcome of artificial selection?

Possible Answers:

Artificial selection increases the variation of traits within a population 

Artificial selection tends to favor wild type traits

Artificial selection increases the compatibility between organisms and their environment

Artificial selection can result in dramatic changes to a species in a relatively short period of time

Correct answer:

Artificial selection can result in dramatic changes to a species in a relatively short period of time

Explanation:

Artificial selection is a process by which humans have modified species over many generations by selecting and breeding individuals that possess desired traits. The result of such a selection is a narrowing of the traits originally present from its ancestors. The goal of artificial selection is generally to make certain desired traits fixed in the population, with an allele frequency of 100%. These traits are relatively arbitrary, and may be wild type, recessive, advantageous, or disadvantageous. The key factor is a decrease in genetic variability in a small population.

Examples of artificial selection include the derivation of individual breeds of dog and the production of genetically specific lab mice.

Example Question #242 : Evolution And Genetics

A species of moth that has a predominantly darker coloration in industrial urban areas, predominantly lighter coloration in rural areas, and limited intermediate coloration in both habitats. This is an example of what type of selection?

Possible Answers:

Disruptive selection

Stabilizing selection

Directional selection

Artificial selection

Correct answer:

Disruptive selection

Explanation:

Disruptive selection occurs when conditions in a habitat favor individuals that are on the extremes of the phenotypic range, instead of individuals with intermediate phenotypic traits. In the example provided in the question, dark-colored moths and light-colored moths each have regions of the habitat where they gain an advantage, but intermediate grey coloring is not favored in any region of the habitat. As a result, both extremes will experience positive selection, while the intermediate will decrease, giving rise to a disruptive selection trend.

Stabilizing occurs when the intermediate phenotype is favored over either extreme. Directional selection occurs when a single extreme is favored over any other phenotype. Artificial selection is the result of human manipulation of breeding, selecting for chosen traits.

Example Question #243 : Evolution And Genetics

Which type of selection is depicted by the graph if the solid line represents the original population and the dashed line is the population following selection?

Stabilizing_selection_image

Possible Answers:

Directional selection

Artificial selection

Disruptive selection

Stabilizing selection

Correct answer:

Stabilizing selection

Explanation:

Stabilizing selection removes extreme variants, as they do not provide a survival advantage in a given environment, and increases the frequency of the intermediate phenotype. For example, the bone density of a species of bird is likely to experience stabilizing selection. Bones that are too dense will inhibit the bird's ability to fly, and bones that are too light will be brittle and prone to injury. Stabilizing selection moderates the influence of these two factors and selects for the intermediate phenotype that is neither too heavy, nor too weak.

Disruptive selection shows an increase the in the frequency of extreme traits and a decline in the intermediate trait. For example, if two extremes are white and black coloration, disruptive selection will act against grey coloration and favor both white and back. Directional selection favors only one extreme, for example favoring black over grey and grey over white. Artificial selection occurs when humans interfere with breeding habits to promote the inheritance of a specific trait.

Example Question #1 : Understanding Types Of Selection

The various species of Galapagos finches utilize their beaks to access food resources in many ways. Those with longer beaks use their beaks to penetrate cactus fruit and eat the inside, while those with short beaks tear apart the base of the cactus and eat insect larvae and pupae.

Finches with medium beak size feed on seeds. These birds aren't specialized to feed on insect larvae or cactus fruit like finches with short or long beaks. What type of selection would be observed if deforestation removed all the trees from the area where these birds obtained seeds?

Possible Answers:

Stabilizing selection

Multi-directional selection

Directional selection

Sexual selection

Disruptive selection

Correct answer:

Disruptive selection

Explanation:

In this example the extreme beak sizes are favored over the mean; however the mean beak size does not change. There is selection against the mean, without affecting the value of the mean. This type of selection is known as disruptive selection.

Example Question #1 : Natural Selection

Due to the abundance of blue-bellied lizards, they are easier for predators to find. Predators such as hawks become adapted to spotting these blue-bellied lizards and prey on them more frequently than yellow-bellied lizards. When the blue-bellied lizard population begins to decline, the yellow-bellied lizard population begins to rise (due to more abundant resources and the fact that they are preyed on less than the blue-bellies). Which of the following best describes the relationship between the two types of lizards?

Possible Answers:

Heterozygote advantage

Disruptive selection 

Relative fitness 

Intersexual selection

Frequency-dependent selection

Correct answer:

Frequency-dependent selection

Explanation:

This relationship displays a frequency-dependent selection. Frequency-dependent selection occurs when the fitness of a phenotype depends on how common it is in the population. When blue-bellied lizards are preyed on the most because they are most abundant, the yellow-bellied lizard population grows quickly. However, as the blue-bellied lizard population declines, predators will begin to prey on the yellow-bellied lizards. As the yellow-bellied lizard population declines, the blue-bellied lizard population will increase, and so on. The number of blue or yellow-bellied lizards depends on the relative amount of lizards of a different phenotype, demonstrating frequency-dependent selection.  

Example Question #1 : Identify Evolutionary Change Mechanisms

What is true regarding mutations?

Possible Answers:

Mutations may be harmful

All of these

Mutations are changes to a cell's genome

Duplications, inversions, and translocations are all types of mutations

Correct answer:

All of these

Explanation:

Mutations are changes to a cell’s genome and include inversions, duplications, translocations, and deletions, among other unplanned changes to the DNA. Mutations can be harmful to the organism, but can also have beneficial or neutral impacts. Mutation is an important means of evolution because it introduces new genetic combinations into a genome, allowing for the potential of new functions. 

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