Khan Academy Practice Ap Bio Unit 7

Two populations of birds have overlapping geographic ranges. Birds in the two populations look similar, having only small differences in their feather coloring. The populations are classified as being part of a single species. A scientist claims that, according to the biological species concept, the two populations are actually separate species. Which of the following observations would provide the most direct evidence in support of the scientist's claim?

(Choice B, Checked, Correct) CORRECT (SELECTED) Birds from each population mate only with birds from their own population.

A population of European eels (Anguilla anguilla) in an English river have variation in head width. The eels can have a range of head widths, and the size of an eel's head is correlated with its diet and where it eats along the riverbank. Head width in these eels is an inherited trait. European eels travel from the river to the sea to reproduce. Scientists have found that eels with either wide or narrow heads tend to be more successful at this process than eels with intermediate head widths. Based on the information given, which of the following graphs shows the type of selection that is likely to occur in the eel population over time?

CORRECT (SELECTED) According to the text, eels with wide or narrow heads are more likely to reproduce successfully than eels with intermediate head widths. As a result, eels with wide or narrow heads are likely to become more common in the population over time. So, the population's phenotypes will likely shift toward two extremes, which is consistent with the type of selection shown in the graph above.

Which of the following does not describe a human activity that is likely to contribute to extinction in a temperate forest ecosystem?

CORRECT (SELECTED) A nonprofit organization plants millions of trees to help restore logged North American forests. Planting trees to restore forest habitats is likely to protect species in the ecosystem, not contribute to extinction.

Each diagram below shows a set of sedimentary rock layers in the fossil record. A thin, black layer represents an area rich in iridium from volcanic ash, indicating a time of extreme volcanic activity on Earth's surface. Which of the following diagrams shows evidence of a mass extinction event caused by extreme volcanic activity on Earth's surface?

graph 1 (fossils under black line in the middle and then a different color fossil ontop)

The agouti, or banded, fur pattern in cats is primarily controlled by a single gene that encodes a signaling protein involved in hair pigmentation. Cats with agouti fur have at least one copy of the dominant allele (AAA). Non-agouti cats have two copies of the recessive allele (aaa). The numbers of cats with agouti and non-agouti fur in two separate populations are shown in the table below. If the two populations are each in Hardy-Weinberg equilibrium, which of the following graphs shows the correct genotype frequencies for the populations

graph 1 (reflection along center)

In order to study evolutionary relationships, a scientist compared the nucleotide sequences of Gene X in 5 different species. The number of nucleotide differences found between each species pair is summarized in the following table. Which of the following cladograms is best supported by the information above?

graph 1 (start with E and ending with BC with A alone)

Based on the information in the table, which of the following cladograms best represents the evolutionary relationships among the species?

graph 1 (start with French rose with giant sequoia sharing)

Based on the information in the table, which of the following cladograms best represents the evolutionary relationships among the species?

graph 2 (start at gorilla and bonobo and end at shark with cow alone)

A scientist is studying the relationship between genetic diversity and a population's mortality rate. The scientist defines the mortality rate as the percentage of the population that dies over a certain time period following an environmental disturbance. Which of the following graphs best represents the relationship between the genetic diversity within a population and the population's mortality rate?

graph 3 (line down)

The protein mTOR is a central regulator of cell growth and is highly conserved among vertebrates. Scientists compared the amino acid sequences of mTOR from five different vertebrate species, and recorded the number of amino acid differences in mTOR between each species pair. The results are shown in the table below. Which of the following cladograms is best supported by the information in the table?

graph 3 (start with oliva baboon and end at zebrafish but in the middle is dog alone)

A scientist is studying the relationship between genetic diversity and population resilience. The researcher defines resilience as the percentage of a population that survives over a certain time period after the onset of environmental change. Which of the following graphs best represents the relationship between the genetic diversity within a population and the population's resilience?

graph 3 (straight line up)

Some Brassica rapa plants make a pigment called anthocyanin that colors their stems purple. A plant's degree of anthocyanin pigmentation can range from light purple to dark purple, and is largely genetically determined. A group of students grew a population of B. rapa plants, Generation 1, in their classroom and scored the degree of anthocyanin pigmentation for each plant on a scale of 1-5 (Figure 1). Next, the students used the Generation 1 plants with the lowest anthocyanin pigmentation scores as parents for the next generation, Generation 2. The students grew the B. rapa plants of Generation 2 and scored the degree of anthocyanin pigmentation for each plant (Figure 2). Then, the students used the Generation 2 plants with the lowest anthocyanin pigmentation scores as parents for the third generation, Generation 3. Which of the following graphs best predicts the distribution of anthocyanin pigmentation scores in Generation 3?

graph 4 (middle concentration)

In the plant species Brassica rapa, height can vary among individuals and is largely determined by which genes an individual has. A group of students grew a population of B. rapa plants, Generation 1, in their classroom. The students measured the height of each plant in the population and determined the average height for Generation 1 (Figure 1). 001010202030304040Generation 1Plant height (cm) Figure 1: Average height for Generation 1 B. rapa plants. Next, the students used the tallest Generation 1 plants as parents for the next generation, Generation 2. The students grew the B. rapa plants of Generation 2 and determined the average height of the population. Then, the students repeated this process for one more generation, Generation 3. Given the average height for Generation 1 B. rapa plants, which of the following graphs best predicts the average height for Generations 2 and 3?

third graph (increasing trend)

Wheat stem rust (Puccinia graminis) is a fungus that can cause disease in wheat plants. The fungus infects a wheat plant by injecting proteins into the plant's cells. These proteins help the fungus grow and reproduce, harming the plant in the process. To prevent losing crops to this disease, farmers around the world grow wheat plants that are resistant to wheat stem rust. Resistant plants make their own proteins that detect the injected proteins of wheat stem rust and then trigger a physiological response. This response prevents the fungus from growing on the plants and causing disease. In 1999, a new strain of wheat stem rust was discovered in Uganda. This strain, called Ug99, can cause disease on wheat plants that were previously resistant to stem rust. According to the Food and Agriculture Organization of the United Nations, Ug99 is a major threat to global wheat production. Based on the information above, which of the following is most likely true about the ancestry of wheat stem rust strain Ug99?

CORRECT (SELECTED) A strain of stem rust developed a mutation that changed the structure of its injected proteins so that they were not detected by resistant wheat plants, allowing the strain to grow and reproduce on these plants. Ug99 likely evolved through natural selection: genetic variation in the form of mutation allowed the strain to become reproductively successful on previously-resistant wheat plants. Over time, this strain of wheat stem rust became more common in the population.

The following table lists evolution rate estimates for a set of viruses. The evolution rates are measured as the number of base-pair substitutions per nucleotide site in the virus genome, per year (s/n/y). Which of the following claims is best supported by the data in the table?

CORRECT (SELECTED) A vaccine against the measles virus is likely to be more durable in the population than a vaccine against the influenza A virus. Vaccines trigger the body to make antibodies against certain viral proteins. A lower evolution rate means these proteins are less likely to change over time, making the vaccine more durable in the population. The data in the table shows that the measles virus has a lower evolution rate than the Influenza A virus, so the data supports this claim.

Many plants sense and respond to light with the help of the phytochrome A protein. The phytochrome A protein is encoded by the PhyA gene. Scientists compared the nucleotide sequences of the PhyA gene from five different plant species. To do this, the scientists calculated the percentage of nucleotides in the PhyA gene that were shared by each pair of species. The results are shown in the table below. Which of the following statements is best supported by the data in the table?

CORRECT (SELECTED) A. thaliana is more closely related to C. sinensis than to G. max. Species that are more closely related are likely to have a larger percentage of identical nucleotides in their PhyA genes. According to the table, the PhyA genes of A. thaliana and C. sinensis have 76.5% identical nucleotides, while the PhyA genes of A. thaliana and G. max have 68.6% identical nucleotides. So, A. thaliana is more closely related to C. sinensis than to G. max.

Common carp (Cyprinus carpio) are fish that have small, evenly-spaced scales covering their entire bodies. Fish farmers bred a population of common carp over many generations to have only a few patches of large scales on their bodies. Common carp with this patchy scale phenotype are called mirror carp. Some of these mirror carp escaped captivity and established a wild population in a local lake. A scientist predicted that individuals in this wild mirror carp population would, over time, evolve to have scales covering their entire body due to selective pressures in the wild. To study this, the scientist collected phenotypic data on the wild population at four time points, each ten years apart so as to include multiple generations of carp. The scale phenotypes were categorized as either partial cover (scales covering less than 10\%10%10, percent of the fish's body), intermediate cover, or full cover (scales covering greater than 90\%90%90, percent of the fish's body). These data are shown in the table below. Based on the information given, which of the following graphs best shows the type of selection occurring on the wild carp population?

CORRECT (SELECTED) According to the data table, the population shifted from having mostly fish with partial scale cover to having mostly fish with full scale cover. So, the average phenotype in the population was shifted strongly in one particular direction, which is consistent with the type of selection shown in the graph above.

A scientist is studying two populations of Laysan finches in the Hawaiian islands. The populations are isolated from each other, but live under similar environmental conditions. Over a 20-year period, the scientist gathers allele frequency data for a certain gene, which has alleles BBB and bbb. A subset of the scientist's results for the two populations is shown in the following table. Which of the following statements is best supported by the table?

CORRECT (SELECTED) Allele B became fixed in Population 1 as a result of genetic drift. According to the table, Allele B did become fixed in Population 1, with its frequency increasing to 1.00 over the study period. In contrast, the frequency of Allele B in Population 2 decreased. The populations live in similar environments, so neither change in Allele B frequency can be definitively attributed to environmental conditions. Instead, Allele B likely became fixed in Population 1 as a result of random fluctuations in allele frequencies, which is known as genetic drift.

A scientist is studying two populations of Australian ghost bats. The populations are isolated from each other, but live under similar environmental conditions. Over a 19-year period, the scientist gathers allele frequency data for a certain gene, which has alleles NNN and nnn. A subset of the scientist's results for the two populations is shown in the following table. Which of the following statements is best supported by the table?

CORRECT (SELECTED) Allele NNN was lost from Population 2 as a result of genetic drift. According to the table, Allele NNN was lost from Population 2, with its frequency decreasing to 0.000.000, point, 00 over the study period. In contrast, the frequency of Allele NNN in Population 1 increased. The populations live in similar environments, so neither change in Allele NNN frequency can be definitively attributed to environmental conditions. Instead, Allele NNN was likely lost from Population 2 as a result of random fluctuations in allele frequencies, which is known as genetic drift.

Based on the cladogram, which of the following derived characters is shared by orangutans and eagles but is not present in salamanders?

CORRECT (SELECTED) Amniotic egg According to the position of the label on the cladogram, amniotic eggs are present in the most recent common ancestor of orangutans and eagles, but not in the most recent common ancestor of orangutans, eagles, and salamanders.

Which of the following statements provides evidence that all of Earth's organisms are descended from a common ancestor? 👁️ Note that there are 2 answers to this question.

CORRECT (SELECTED) Bacteria, eukaryotes, and archaea use DNA to encode proteins, which carry out cellular functions. The fact that organisms from all three domains of life share a fundamental cellular process (using DNA to encode proteins) provides evidence that all of Earth's organisms are descended from a common ancestor. CORRECT (SELECTED) Bacteria, eukaryotes, and archaea use ATP to release energy that can be used by the cell. The fact that organisms from all three domains of life share a fundamental cellular process (using ATP to power cell processes) provides evidence that all of Earth's organisms are descended from a common ancestor.

Earth formed approximately 4.5 billion years ago. Until roughly 3.9 billion years ago, the conditions of early Earth were too hostile to support sustained life. The earliest strong evidence of life in the fossil record dates to 3.5 billion years ago. Based on the information above, which of the following describes when life most likely originated on Earth?

CORRECT (SELECTED) Between 3.9 and 3.5 billion years ago Conditions on Earth could support life beginning around 3.9 billion years ago, and the earliest record of life in the fossil record dates to 3.5 billion years ago. So, life likely originated sometime between these two dates.

One model of the origin of life on Earth hypothesizes that organic molecules arose abiotically from inorganic precursors under certain conditions on early Earth. Some scientists speculate that this could have occurred near the openings of volcanoes. Others think it likely occurred near deep-sea alkaline vents, which release warm, alkaline water. Which of the following questions related to the information above is most scientifically testable?

CORRECT (SELECTED) Can organic molecules be generated abiotically in a warm, high-pH environment, similar to that near an alkaline vent? A testable question can be answered by an experiment that manipulates one or more variables and measures the effect on an outcome. This question can be answered by a laboratory experiment that manipulates temperature and pH, and measures the formation of organic molecules.

One model of the origin of life on Earth hypothesizes that organic molecules arose abiotically under the atmospheric conditions of early Earth. Another model hypothesizes that these organic molecules arrived on Earth from space via a meteorite or other source. Which of the following questions related to the models described above is most scientifically testable?

CORRECT (SELECTED) Can organic molecules be generated abiotically under low temperature and high levels of UV radiation, similar to conditions in space? A testable question can be answered by an experiment that manipulates one or more variables and measures the effect on an outcome. This question can be answered by a laboratory experiment that manipulates temperature and light, and measures the formation of organic molecules.

The productivity of domesticated crop plants is typically measured as yield, or the amount of a crop produced per unit of land. The following table shows the average corn yield measured in tons per hectare in the United States from 1900-2014. Which of the following best explains the data in the table?

CORRECT (SELECTED) Corn yield increased dramatically after 1940 largely because farmers bred new, higher-yielding corn varieties. The data in the table shows that from 1900 to 1940 corn yield was mostly stable, and after 1940 corn yield steadily increased. So, the data supports the explanation that the farmers bred new, higher-yielding corn varieties starting around 1940.

Which of the following statements support the hypothesis that crocodiles are more closely related to birds than to frogs? 👁️ Note that there are 2 answers to this question.

CORRECT (SELECTED) Crocodiles and birds have eggs that are protected by an amniotic membrane, while frogs do not. This statement describes a homologous feature that is shared by crocodiles and birds, but is absent from frogs. So, this statement supports the hypothesis that crocodiles are more closely related to birds than to frogs. (Choice D, Checked, Correct) CORRECT (SELECTED) Crocodiles and frogs have more nucleotide differences in their homologous DNA sequences than crocodiles and birds do. This statement describes a comparison of homologous DNA sequences which tells you that a crocodile's DNA sequences are more similar to a bird's than to a frog's. So, this statement supports the hypothesis that crocodiles are more closely related to birds than to frogs

Which of the following statements support the hypothesis that dolphins are more closely related to humans than to fish? 👁️ Note that there are 2 answers to this question.

CORRECT (SELECTED) Dolphins and fish have more nucleotide differences in their ribosomal RNA gene sequences than dolphins and humans do. This statement describes a comparison of gene sequences which tells you that a dolphin's gene sequence is more similar to a human's than to a fish's. So, this statement supports the hypothesis that dolphins are more closely related to humans than to fish. CORRECT (SELECTED) Dolphins and humans have forelimbs with a similar bone structure, while fish do not. This statement describes a homologous feature that is shared by dolphins and humans, but is absent from fish. So, this statement supports the hypothesis that dolphins are more closely related to humans than to fish.

Which of the following statements is true about the Miller-Urey experiment

CORRECT (SELECTED) During the experiment, the scientists generated a variety of amino acids by exposing gases in a chamber to an electric spark.

Maize, or corn, is a food crop that was domesticated roughly 10,000 years ago. The wild ancestor of maize is a grass called teosinte. Both maize and teosinte make ears, which consist of kernels attached to a central cob. A comparison of ear characteristics in populations of maize and teosinte is presented in the following table. Which of the following statements is best supported by the data in the table?

CORRECT (SELECTED) During the process of maize domestication, humans likely crossed plants with larger than average kernels to create each new generation. The domestication of maize from teosinte occurred through artificial selection. During this type of selection, humans cross individuals with desirable traits, causing those desirable traits to occur more frequently in subsequent generations. The data in the table shows that the maize kernels are larger than teosinte kernels. So, it's likely that humans crossed plants with larger-than-average kernels to create each new generation during the process of maize domestication.

The protein mTOR is a central regulator of cell growth and is highly conserved among vertebrates. Scientists compared the amino acid sequences of mTOR from five different vertebrate species, and recorded the number of amino acid differences in mTOR between each species pair. The results are shown in the table below. Which of the following statements is best supported by the data in the table?

CORRECT (SELECTED) Emperor penguins are more closely related to dogs than to zebrafish. Species that are more closely related are likely to have fewer differences in their mTOR sequences. According to the table, the mTOR sequence in emperor penguins and dogs differs by 117 amino acids, while the mTOR sequence in emperor penguins and zebrafish differs by 244 amino acids. So, emperor penguins are more closely related to dogs than to zebrafish.

Which of the following describes a result of artificial selection?

CORRECT (SELECTED) Fur length in a population of cats has decreased due to selective breeding by humans. Artificial selection is when humans purposefully breed organisms with desirable traits in order to increase the frequency of those traits in the population. So, an increase in fur length due to selective breeding by humans describes a result of artificial selection.

In the 1800's, there were millions of greater prairie chickens in the state of Illinois. However, by 1993 there were fewer than 50 as a result of hunting and the conversion of prairie habitats to farmland. Conservation efforts have helped to increase the number of greater prairie chickens in Illinois, but their numbers are still small. Which two claims are best supported by the information provided above? 👁️ Note that there are 2 answers to this question.

CORRECT (SELECTED) Greater prairie chicken populations in Illinois have little genetic diversity and are therefore at risk of decline. Because of the population bottleneck, the greater prairie chicken populations in Illinois have very little genetic diversity. Populations with little genetic diversity are at greater risk of decline. CORRECT (SELECTED) Because of the bottleneck, the greater prairie chicken populations in Illinois are less likely to contain individuals that can withstand a certain environmental pressure. Because of the population bottleneck, the greater prairie chicken populations in Illinois have very little genetic diversity. Populations with little genetic diversity have a smaller range of phenotypes, making them less likely to contain individuals that can withstand a given environmental pressure.

Marine iguanas (Amblyrhynchus cristatus) are found only on the Galápagos Islands, which are located off the coast of Ecuador. These lizards are unique in that they forage for food in the ocean. Compared to land iguanas, marine iguanas have certain adaptations that allow them to survive in their coastal habitat. These adaptations include a long, flattened tail used for swimming and dense leg bones that give the iguanas stability underwater. Scientists believe the land-dwelling ancestors of the marine iguana floated on vegetative debris from Central America to the Galápagos Islands about 4.5 million years ago. Based on the information given above, which of the following is most likely true about the ancestry of the marine iguana?

CORRECT (SELECTED) Iguanas with phenotypes that were better suited for swimming were able to exploit a novel food source, so they left more surviving offspring over time. Marine iguanas likely evolved through natural selection: variation in the population of iguanas that first reached the islands allowed some individuals to be more reproductively successful in a marine environment. Over time, this allowed marine-adapted traits to become more common in the population.

Cane toads (Rhinella marina) have a toxin in their skin that can kill their predators. These toads were introduced into Australia in 1935. Since then, Australian populations of cane toads have grown considerably, and the toads are now considered an invasive species. Australian red-bellied black snakes (Pseudechis porphyriacus) eat small animals, including toads. These snakes had not been exposed to cane toads prior to 1935. Researchers predicted that the introduction of cane toads would have placed a selective pressure on Australian snake populations that would favor snakes with inheritable resistance to the cane toad toxin. To test their prediction, the researchers determined levels of toxin resistance in several populations of red-bellied black snakes that had been exposed to cane toads for different amounts of time. Resistance levels were approximated by measuring how much the snakes' swimming speed was reduced after being exposed to a non-lethal dose of the cane toad toxin. A smaller reduction in swimming speed meant a higher resistance to the toxin. The data are shown in Figure 1. Based on the experimental results, which of the following statements about red-bellied black snake evolutionary fitness is true?

CORRECT (SELECTED) In areas with cane toads, snakes with higher toxin resistance produced more offspring than snakes with lower resistance. The graph shows that snake populations exposed to cane toads for longer periods of time had smaller reductions in swimming speed and, therefore, higher levels of toxin resistance. This indicates that, over time, natural selection favored toxin resistance in these snakes.

Destruction of swamplands has reduced the area inhabited by a certain panther population. As a result, the panther population is small, highly inbred, and at risk of extinction. Which of the following actions can humans take to decrease the panther population's risk of extinction?

CORRECT (SELECTED) Introduce a small number of panthers from a genetically distinct population into the at-risk population. Because the panther population is highly inbred, it has little genetic diversity, putting it at risk of extinction. To help decrease this risk, humans can increase the population's genetic diversity through the introduction of individuals from a separate population.

The RNA World Hypothesis proposes that RNA was the earliest self-replicating biological molecule, performing functions in early cells that are now fulfilled by other biological molecules. One piece of evidence in support of the RNA World Hypothesis is that RNA molecules can catalyze chemical reactions. This provides support for the idea that, in early cells, RNA carried out a function similar to that of proteins. Which of the following is an additional piece of evidence in support of the RNA World Hypothesis?

CORRECT (SELECTED) Like DNA, RNA can encode genetic information. Like DNA, RNA is made up of a series of nucleotides that can vary in sequence and be replicated. This provides support for the idea that, in early cells, RNA carried out a function similar to that of DNA.

The RNA World Hypothesis proposes that RNA was the earliest self-replicating biological molecule, performing functions in early cells that are now fulfilled by other biological molecules. One piece of evidence in support of the RNA World Hypothesis is that RNA molecules can encode genetic information. This provides support for the idea that, in early cells, RNA carried out a function similar to that of DNA. Which of the following is an additional piece of evidence in support of the RNA World Hypothesis?

CORRECT (SELECTED) Like proteins, RNA can carry out catalytic activities. Ribozymes are RNA molecules that, like protein enzymes, can catalyze chemical reactions. This provides support for the idea that, in early cells, RNA carried out a function similar to that of proteins.

Roughly 66 million years ago, the Cretaceous-Paleogene mass extinction event caused all non-avian dinosaurs and some mammal groups to go extinct. In the 10 million years following the extinction event, roughly 4,000 new species of mammals evolved, including the first fully aquatic mammals and flying mammals. Which of the following statements is most consistent with the information provided in the text above?

CORRECT (SELECTED) Mammals underwent an adaptive radiation after the mass extinction event, likely due to the use of newly available ecological niches. According to the text, the number of mammal species rapidly increased after the mass extinction event. This increase in species diversity represents an adaptive radiation, which can occur after mass extinction events as groups of organisms adapt to newly available ecological niches.

According to this cladogram, marmosets are more closely related to dogs than to tenrecs. Which of the following statements provides the best justification for this relationship?

CORRECT (SELECTED) Marmosets share a more recent common ancestor with dogs than with tenrecs. According to the cladogram, marmosets and dogs share a common ancestor that is not shared by tenrecs. Based on its position, this common ancestor existed in the more recent past than the common ancestor shared by marmosets, dogs, and tenrecs.

As a result of adaptive radiation, there are more than 50 species of honeycreeper birds found on the Hawaiian islands. These species differ in their beak shapes, food sources, and feeding behaviors. Which of the following statements best explains how adaptive radiation could have led to the diversity of honeycreeper species found on the Hawaiian islands?

CORRECT (SELECTED) Members of a single bird species came to the islands from the mainland. Over time, this species diverged into many species as groups of birds adapted to different habitat niches on the islands.

As a result of adaptive radiation, there are roughly 150 species of Anolis lizards found on islands in the Caribbean sea. These species differ in their physical features, behavior, and habitat use. Which of the following statements best explains how adaptive radiation could have led to the diversity of Anolis species found on the Caribbean islands?

CORRECT (SELECTED) Members of a single lizard species floated to the islands from the mainland. Over time, this species diverged into many species as groups of lizards adapted to different habitat niches on the islands.

In 1953, the scientists Stanley Miller and Harold Urey conducted an experiment that provided support for the hypothesis that molecules important to life could have formed abiotically under Earth's early conditions. The apparatus used in the experiment is pictured below. Which biological molecules were generated during the Miller-Urey experiment?

CORRECT (SELECTED) Only amino acids The experiment generated amino acids.

The brown anole (Anolis sagrei) is a type of lizard that is native to islands in the Caribbean Sea. These lizards can live in a variety of habitats. Ground-dwelling populations of brown anoles live on lower parts of tree trunks and on the ground. These populations have long legs that help with jumping. Other anole lizard populations live higher up on tree trunks. These populations have short legs that help with perching. Curly-tailed lizards (Leiocephalus carinatus) are a predator of the brown anole. A group of researchers introduced these predatory lizards into the habitat of certain ground-dwelling brown anoles. To avoid these predators, many individuals from the ground-dwelling populations of brown anoles began to move higher into trees. Based on the information above, which of the following is the best prediction for what will happen over time to the populations of ground-dwelling brown anoles in areas where curly-tailed lizards were introduced?

CORRECT (SELECTED) Over many generations, the brown anole populations will likely develop shorter legs as they adapt to living higher in trees. The passage tells us that tree-dwelling brown anoles have short legs that are adapted for perching. So, it is likely that if the ground-dwelling brown anoles begin living higher in trees, the process of natural selection will lead to short legs becoming more common in the population over time.

Rock pocket mice (Chaetodipus intermedius) in the American Southwest can have light brown fur or dark brown fur. These mice live on a landscape that includes light sand and dark lava rock. Mice that are camouflaged in the landscape are less likely to be caught by owls, which are their main predators. Scientists determined that dark brown fur in rock pocket mice is caused by a mutation in a gene called Mc1r. Mice with dark brown fur have this mutation, whereas mice with light brown fur do not. If a population made up of light and dark mice was moved from an area with light sand and dark rock to an area with only light sand, which of the following describes the most likely result?

CORRECT (SELECTED) Over many generations, the percentage of the population with the Mc1r gene mutation will decrease.

According to this cladogram, oystercatchers are more closely related to flamingos than to penguins. Which of the following statements provides the best justification for this relationship?

CORRECT (SELECTED) Oystercatchers share a more recent common ancestor with flamingos than with penguins. According to the cladogram, oystercatchers and flamingos share a common ancestor that is not shared by penguins. Based on its position, this common ancestor existed in the more recent past than the common ancestor shared by oystercatchers, flamingos, and penguins.

Babiana ringens is a flowering plant found in South Africa. B. ringens plants have flowers that bloom close to the ground, and a stalk that projects upwards above the flowers. The stalk is not a significant source of photosynthetic carbon for the plant. Malachite sunbirds (Nectarina famosa) use the stalk of B. ringens as a perch when gathering nectar from the plant's flowers. The stalk positions the birds so that their bodies rub the flowers when they reach down with their beaks to gather nectar. A group of scientists carried out an experiment in which they removed the stalks from B. ringens plants early in the plants' development. When the plants flowered, the researchers counted how many times sunbirds visited the plants with stalks removed compared to plants that still had their stalks present. In addition, the scientists measured the seed set, or the number of seeds produced, for each plant. The results are shown below in Table 1 and Figure 1.

CORRECT (SELECTED) Plants with stalks attract more pollinators, enabling them to produce more offspring in each generation than plants without stalks. The data shows that plants with stalks present had more sunbird visits and a higher seed set than plants without stalks. This indicates that, over time, natural selection likely favored the presence of stalks because they increased the number of visits by pollinators and, therefore, the number of offspring produced per plant.

A scientist is studying two populations of rodents: one that lives at an altitude of 5,000 feet, and another at 5,200 feet. Rodents in the two populations have some small differences in their fur coloring, and are classified as being two separate species. The scientist claims that, according to the biological species concept, the two populations actually represent a single species. Which of the following observations would provide the most direct evidence in support of the scientist's claim?

CORRECT (SELECTED) Rodents from the two populations interbreed and produce viable offspring.

Consider the following statements: A. Bacteria, eukaryotes, and archaea use DNA to encode proteins. B. All prokaryotes and eukaryotes can be grown and studied under similar laboratory conditions. C. Organisms from all domains use ATP to release energy that can be used by the cell. Which of the statements provide evidence that all of Earth's organisms are descended from a common ancestor?

CORRECT (SELECTED) Statements A and C Statements A and C tell us that organisms from all three domains of life share fundamental cellular processes (using DNA to encode proteins and using ATP to release energy for the cell), providing evidence that all of Earth's organisms are descended from a common ancestor

Consider the following statements: I. A pollen grain from one population is blown to the area of another population where it lands on the pistil of a flower, fertilizing it. II. A bacterium's gene sequence changes due to a DNA replication error, giving the bacterium resistance to a certain antibiotic. Which of the statements describes at least one new allele entering a population?

CORRECT (SELECTED) Statements I and II

Consider the following statements: I. Due to a DNA replication error during gamete formation, a rabbit passes a mutated gene to its baby, and the baby has light-colored fur as a result. II. A small number of water snakes from a mainland population swim to an island where they mate with snakes from the island's population. III. A bacterium from one population transfers a toxin-encoding gene to a bacterium in another population via horizontal gene transfer. Which of the statements describes at least one new allele entering a population?

CORRECT (SELECTED) Statements I, II, and III

Between 1975 and 2010, the habitat range of an island lizard population was greatly reduced as a result of human activity (Figure 1). This reduction in habitat range also greatly reduced the number of individuals in the lizard population. Which of the following statements is most likely true about the lizard population in 2010?

CORRECT (SELECTED) The 2010 population has fewer unique alleles than the 1975 population. According to the information presented above, the lizard's habitat and population size were reduced between 1975 and 2010. Because there are many fewer individuals in the 2010 population, there is likely less genetic diversity in the 2010 population. So, the 2010 population likely has fewer unique alleles compared to the 1975 population.

The following table lists evolution rate estimates for a set of viruses. The evolution rates are measured as the number of base-pair substitutions per nucleotide site in the virus genome, per year (s/n/y). Which of the following claims is best supported by the data in the table?

CORRECT (SELECTED) The SARS coronavirus is more likely to evolve antiviral drug resistance over a given time period than the human hepatitis B virus. The higher a virus's evolution rate, the more likely the virus is to develop new traits in a given time period, including resistance to antiviral drugs. The data in the table shows that the SARS coronavirus has a higher evolution rate than the human hepatitis B virus, so the data supports this claim.

The pitcher-plant mosquito (Wyeomyia smithii) has a genetically-controlled behavioral response to changing seasons: these mosquitos transition from an active period of growth and reproduction in warmer months to diapause, or dormancy, in cooler months. The environmental cue that induces mosquitos to enter diapause is daylength, which gets shorter towards the end of the mosquitos' active period. In the habitat range of the pitcher-plant mosquito, regions that are further south tend to have longer periods of warmth than regions that are further north. So, the active period for mosquitos in southern regions lasts later into the year, when the days are shorter. As a result, the daylengths that induce diapause in southern mosquito populations are, on average, shorter than the daylengths that induce diapause in northern mosquito populations. Researchers have observed that climate change has led to longer periods of warmth in the pitcher-plant mosquito's northern range. Based on the information above, which of the following best predicts the effect of climate change on the northern populations of pitcher-plant mosquitos?

CORRECT (SELECTED) The average daylength that induces diapause in northern mosquitos will decrease because the longer periods of warmth will allow the mosquitos to be active later into the year. Climate change has led to longer periods of warmth in the pitcher-plant mosquitos' northern range, which should allow the populations in the north to remain active later into the year when the days are shorter. Mosquitos that remain active longer are likely to reproduce more, so natural selection will likely lead to a decrease in the average daylength that induces diapause in these populations.

Penicillin and other beta-lactam antibiotics are routinely given to farm animals at low doses to prevent infection. These antibiotics cause bacterial cell death by binding to cell wall-synthesis proteins, including the protein PBP2. This binding inhibits proper cell wall synthesis, and causes the cell to burst. Which of the following best predicts what will happen to a population of bacteria in a farm setting that is, over time, consistently exposed to beta-lactam antibiotics?

CORRECT (SELECTED) The bacteria population will evolve resistance to the antibiotics, likely through selection of individuals with a mutation in the PBP2 gene. Natural selection will likely cause the bacteria population to evolve antibiotic resistance because of the antibiotic's strong selective pressure. One way that resistance is likely to occur is through a mutation in the PBP2 gene. For example, a mutation in the PBP2 gene may cause a change in the structure of the PBP2 protein such that it can no longer be bound by the antibiotic.

The following table lists evolution rate estimates for a set of plant viruses. The evolution rates are measured as the number of base-pair substitutions per nucleotide site in the virus genome, per year (s/n/y). Which of the following claims is best supported by the data in the table?

CORRECT (SELECTED) The barley yellow dwarf virus is more likely to overcome engineered virus resistance in plants than the maize streak virus is. The higher a virus's evolution rate, the more likely the virus is to develop new traits in a given time period, including overcoming engineered virus resistance in plants. The data in the table shows that the barley yellow dwarf virus has a higher evolution rate than the maize streak virus, so the data supports this claim.

Scientists have found evidence of five major mass extinction events during Earth's history. One of these, the end-Permian extinction, resulted in the extinction of roughly 96% of Earth's species. These species included many early reptiles, amphibians and the last species of trilobites. One cause of the end-Permian extinction was extreme volcanic activity that generated huge clouds of sulfur dioxide and carbon dioxide. The presence of these gases in the atmosphere led to acid rain, ocean acidification, and global warming. Which of the following describes how the end-Permian extinction was similar to Earth's other four major mass extinctions events?

CORRECT (SELECTED) The extinction was due to large-scale ecological changes. All of Earth's mass extinction events were caused by large-scale ecological changes. These changes caused ecological stress that affected many species at once. In the case of the end-Permian extinction, the ecological stress was caused by acid rain, ocean acidification, and global warming.

A group of researchers is studying fish populations in two small, adjacent mountain lakes. Historically, seasonal flooding temporarily joined the lakes, allowing for repeated cycles of interbreeding and isolation between the lakes' fish populations. The area's climate has become drier, so the seasonal flooding no longer occurs. Which of the following best predicts how the lack of seasonal flooding will affect the fish populations in the lakes over time?

CORRECT (SELECTED) The fish population in each lake will become reproductively isolated, resulting in allopatric speciation. The lack of seasonal flooding has caused the populations to become geographically isolated. With no gene flow between the populations, they will become reproductively isolated due to selective forces, genetic drift, and random mutations. Eventually, they will evolve into separate species. This type of speciation due to geographic separation is called allopatric speciation.

Sunflower (Helianthus annuus) is a plant species with both wild and domesticated varieties. The domesticated varieties are grown largely for their edible seeds, which are housed inside of a hard fruit called an achene. A comparison of achene size in wild and domesticated sunflower populations is presented in the following table. Which of the following statements is best supported by the data in the table?

CORRECT (SELECTED) The genes for having long achenes became more common in the domesticated sunflower population over time due to selection of the long achene trait by humans. Plant domestication occurs through artificial selection, during which humans selectively cross individuals with desirable traits. As a result, those desirable traits (and the genes responsible for them) occur more frequently in subsequent generations. The data in the table shows that achenes in the domesticated sunflower population are longer than achenes in the wild population. So, it's likely that the genes for having long achenes became more common in the domesticated sunflower population over time as humans selected for the long achene trait.

A population of potato plants is growing in a farmer's field. The potatoes were propagated vegetatively, so they are all genetic clones of each other. Nearby, a population of wild potato plants is growing on a hillside. Plants in this population reproduce primarily through sexual reproduction. Both potato plant populations have similar population densities. A fungus-like, oomycete pathogen is introduced to the area and infects both populations at roughly the same time. Which of the following is the best prediction for how the oomycete pathogen will affect the two potato plant populations?

CORRECT (SELECTED) The hillside population will be less severely affected because it is more likely to have individuals with some level of resistance to the pathogen. The hillside population reproduces sexually, and therefore has more genetic diversity than the asexually propagated field population. Because of its higher genetic diversity, the hillside population is more likely to have individuals with some level of genetic resistance.

Island 1 is home to a large population of birds. During a storm, a few individuals from the Island 1 population are blown to Island 2, where they establish a new population. This event is represented in the following diagram. Which of the following statements is most likely true about the new bird population immediately after the storm?

CORRECT (SELECTED) The new population's allele frequencies are different from those in the original population. According to the text, a storm blew a few individuals (and their alleles) to Island 2. Because the group of birds blown to Island 2 was not a representative sample of individuals from the original population, some alleles are likely over- or under-represented in the new population. So, the allele frequencies in the new population are likely different from those in the original population.

A population of banana plants is growing in an orchard. The banana plants were propagated vegetatively, so they are all genetic clones of each other. Nearby, a population of wild banana plants is growing in a jungle habitat. Plants in this population reproduce primarily through sexual reproduction. Both banana plant populations have similar population densities. A fungal pathogen is introduced to the area and infects both populations at roughly the same time. Which of the following is the best prediction for how the fungal pathogen will affect the two banana plant populations?

CORRECT (SELECTED) The orchard population will be more severely affected because it has less allelic diversity than the jungle population. The orchard population reproduces asexually, and therefore has less allelic diversity than the sexually-reproducing jungle population. So, the orchard population will be more severely affected because it is less likely to have individuals with some level of resistance to the pathogen.

The following graph shows the size of a plant population in a forest. The population was recently affected by a wildfire, as indicated in the graph. Which of the following statements is most likely true about the plant population immediately after the wildfire?

CORRECT (SELECTED) The population is more likely to be significantly impacted by ongoing genetic drift. According to the graph, the wildfire greatly reduced the size of the plant population. Because genetic drift has a stronger effect in small populations, the plant population will be more likely to be significantly impacted by ongoing genetic drift after the wildfire.

A group of scientists is studying Tetragnatha spiders on the island of Hawaii. A large lava flow has divided the spiders' forest habitat into two parts. As a result, a population of Tetragnatha spiders has become isolated on either side of the hardened lava. Which of the following best predicts how the lava flow will affect the spider populations over time?

CORRECT (SELECTED) The spider population on each side of the lava flow will become reproductively isolated, resulting in allopatric speciation. The lava flow has caused the spider populations to become geographically isolated. With no gene flow between the populations, they will become reproductively isolated due to selective forces, genetic drift, and random mutations. Eventually, they will evolve into separate species. This type of speciation due to geographic separation is called allopatric speciation.

Weeds growing among crop plants can cause significant losses in crop yields. One way that farmers can remove weeds from their fields is through the use of herbicides. One class of herbicides, the acetolactate synthase (ALS)-inhibitors, target the enzyme ALS. Normally, the ALS enzyme carries out the first step of valine, leucine, and isoleucine synthesis. However, when a plant's ALS enzymes are inhibited, the plant cannot make these amino acids and dies. Which of the following best predicts what will happen to a weed population in a field that is, over time, consistently sprayed with an ALS-inhibiting herbicide?

CORRECT (SELECTED) The weed population will evolve resistance to the herbicide, likely through selection of plants with a mutation in the ALS gene. Natural selection will likely cause the weed population to evolve herbicide resistance because of the herbicide's strong selective pressure. One way that resistance is likely to occur is through a mutation in the ALS gene. For example, a mutation in the ALS gene may cause a change in the structure of the ALS enzyme such that it can no longer be targeted by the herbicide.

Which of the following describes two species that exhibit a prezygotic mechanism of reproductive isolation?

CORRECT (SELECTED) The western spotted skunk (Spilogale gracilis) and the eastern spotted skunk (S. putorius) have overlapping geographic ranges, but S. gracilis mates in late summer and S. putorius mates in late winter. These two skunk species do not interbreed because each species mates at a different time of year. This is an example of a prezygotic mechanism of reproductive isolation because it prevents fertilization from occurring between the two skunk species.

A scientist is studying two large populations of corals in a reef ecosystem. The scientist collects data on the number of individuals with different genotypes. The data for the two populations is presented in the tables below. The scientist also notes that the populations are able to exchange gametes, but this happens at a low frequency. Assuming there is no selective pressure on the AAA and aaa alleles, which of the following best predicts what will happen over time to the populations' genotype frequencies?

CORRECT (SELECTED) They will become more similar as a result of gene flow. Gene flow is the transfer of alleles from one population to another. According to the text, the coral populations described above are able to exchange gametes (and their alleles), so gene flow is occurring between the populations. As a result, the populations' genotype frequencies will likely become more similar over time.

The Ozark mountains contain habitats called glades, which are hot, open patches of land surrounded by forest. Glades are home to many animal species, including the collared lizard. In a certain region, scientists have found that the collared lizard populations in neighboring glades are small and lacking in genetic diversity, which puts them at risk of extinction. The populations are isolated from each other by thick forest undergrowth. Historically, this undergrowth was removed by periodic wildfires, but humans have been actively preventing wildfires in the area. Which of the following actions can humans take to decrease the risk of extinction for the collared lizard populations?

CORRECT (SELECTED) Use controlled fires to remove forest undergrowth between glades to promote interbreeding between populations. The collared lizard populations lack genetic diversity, which puts them at risk of extinction. To help decrease this risk, humans can promote gene flow among the populations, which will increase their genetic diversity.

The productivity of domesticated crop plants is typically measured as yield, or the amount of a crop produced per unit of land. The following table shows the average wheat yield measured in tons per hectare in the United Kingdom during select years between 1885-2010. Which of the following best explains the data in the table?

CORRECT (SELECTED) Wheat yield remained relatively stable until 1942, and then increased dramatically as farmers bred higher-yielding wheat varieties. According to the table, wheat yield was mostly stable from 1885 to 1942, and then increased dramatically between 1942 and 2010. So, the data supports the explanation that wheat yield increased after 1942 as farmers bred higher-yielding varieties.

California condors are large, North American vultures that nearly went extinct in the 1980s as a result of habitat destruction. Through captive breeding and reintroduction of populations into the wild, the number of wild California condors is slowly increasing. However, because of the population bottleneck, all of the condor populations that currently exist in the wild are descended from a breeding population of just 14 individuals. Which two claims are best supported by the information provided above? 👁️ Note that there are 2 answers to this question.

CORRECT (SELECTED) Wild California condor populations have little genetic diversity and are therefore at risk of decline. Because all living California condors inherited their alleles from a small bottleneck population, the current wild populations have very little genetic diversity. Populations with little genetic diversity are at greater risk of decline. CORRECT (SELECTED) Because of the bottleneck, the wild California condor populations are less likely to contain individuals that can withstand a certain environmental change. Because California condors experienced a genetic bottleneck, the current wild populations have very little genetic diversity. Populations with little genetic diversity have a smaller range of phenotypes, making them less likely to contain individuals that can withstand a given environmental change.

Which of the following describes the common ancestor of all eukaryotes, but not the common ancestor of all organisms?

CORRECT (SELECTED) a single-celled organism with membrane-bound organelles, linear chromosomes, and spliceosomal introns

The data about which trait provides the strongest evidence that all of the animal species in the table share a common ancestor?

CORRECT (SELECTED) four limbs

In a certain population of mosquitoes, an individual was born with a mutation conferring resistance to an insecticide, a chemical that is used to kill insects. Because the population lives in an area where insecticides are used heavily, the mutation quickly became common in the population. A resistant mosquito from this population got trapped in a person's car and was accidentally transported to a different region. This mosquito then mated with an individual in the local mosquito population. Over time, the mutation for insecticide resistance became common in that population, too. By which of the following processes did the mutation spread between mosquito populations?

CORRECT (SELECTED) gene flow According to the text, the mutation spread between populations when a mosquito from the original population mated with a mosquito from the other population. This type of transfer of genetic material between populations is called gene flow.

The following diagrams represent the generation of mature mRNA in a eukaryotic cell (A) and a prokaryotic cell (B). Of the structures depicted in the diagrams, which were likely present in the common ancestor of all eukaryotes, but not in the common ancestor of all organisms?

CORRECT (SELECTED) spliceosomal introns, membrane-bound organelles, and linear chromosomes

Mammals are part of a group of organisms called synapsids. Synapsids are characterized by having a temporal fenestra, which is a hole in the skull behind the eye socket. All modern mammals are descended from early non-mammalian synapsids. Fossils of the earliest non-mammalian synapsids can be found in rock layers from roughly 305 million year ago. In contrast, true mammals first appear in the fossil record roughly 178 million years ago. The following table provides information about the presence of certain traits in early non-mammalian synapsids and mammals. The presence of a trait is indicated by a checkmark. Each answer choice below describes a specific fossil. Which fossil provides the strongest evidence for the discovery of a transitional species between early non-mammalian synapsids and mammals?

CORRECT (SELECTED) the fossil of an organism with a sprawling gait and middle ear bones, found in a 250-million-year-old rock layer

All modern birds are descended from a group of dinosaurs called theropods. Theropods first appear in the fossil record during the late Triassic to early Jurassic period, roughly 200 million years ago. In contrast, fossils of taxa similar to modern birds can be found in the fossil record by the end of the Cretaceous period, roughly 66 million years ago. The following table provides information about the presence of certain traits in theropods and modern birds. The presence of a trait is indicated by a checkmark. Each answer choice below describes a specific fossil. Which fossil provides the strongest evidence for the discovery of a transitional species between theropods and modern birds?

CORRECT (SELECTED) the fossil of an organism with feathers and a long, bony tail, found in a 145-million-year-old rock layer

All modern tetrapods (amphibians, reptiles, birds, and mammals) are descended from lobe-finned fish. Fossils of early lobe-finned fish can be found in rock layers that are at least 380 million years old. In contrast, true tetrapods first appear in the fossil record roughly 363 million years ago. The following table provides information about the presence of certain traits in early lobe-finned fish and tetrapods. The presence of a trait is indicated by a checkmark. Each answer choice below describes a specific fossil. Which fossil provides the strongest evidence for the discovery of a transitional species between early lobe-finned fish and tetrapods?

CORRECT (SELECTED) the fossil of an organism with scaloid scales and a bending neck, found in a 375-million-year-old rock layer

The data about which trait provides the strongest evidence that all of the plant species in the table share a common ancestor?

CORRECT (SELECTED) vascular tissue

The following table indicates the presence or absence of selected traits for a set of animal species. The data about which trait provides the strongest evidence that all of the animal species in the table share a common ancestor?

CORRECT (SELECTED) vertebrae

A scientist is studying two populations of newts in California's Sierra Nevada mountains. The populations are isolated from each other, but live under similar environmental conditions. Over a 23-year period, the scientist gathers allele frequency data for a certain gene, which has alleles HHH and hhh. A subset of the scientist's results for the two populations is shown in the following table.

CORRECT (SELECTED) Population 2 was likely smaller than Population 1 during the study period. According to the table, Allele H became fixed in Population 2 during the study period, likely because of genetic drift. Significant effects of genetic drift, like the fixation of an allele, typically happen in small populations. Since Population 1 didn't see the same level of impact from genetic drift, it's likely that Population 2 was smaller than Population 1 during the study period.