Khan Academy unit : Natural Selection
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 timelines highlights the time period when life most likely originated on Earth?
3.5 - 3.9
Based on the cladogram, which of the following derived characters is shared by orangutans and eagles but is not present in salamanders?
Amniotic egg
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.
Crocodiles and birds have eggs that are protected by an amniotic membrane, while frogs do not. Crocodiles and frogs have more nucleotide differences in their homologous DNA sequences than crocodiles and birds do.
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.
Crocodiles and frogs have more nucleotide differences in their homologous DNA sequences than crocodiles and birds do. Crocodiles and birds have eggs that are protected by an amniotic membrane, while frogs do not.
Lemurs are a type of primate found only on Madagascar, an island off the coast of Africa. In general, each species of lemur occupies a different ecological niche within the island's varied landscape. For example, golden bamboo lemurs live in rainforests in southeastern Madagascar, where they eat mostly bamboo. The bamboo contains toxic compounds, but the golden bamboo lemurs have adapted to tolerate these toxins. Other lemurs, such as the crowned sifaka, live in dry forest areas and mangroves in northwestern Madagascar. Crowned sifakas stay mainly near the tops of trees and eat leaves, flowers, and fruit. Based on the information above, which of the following is most likely true about the ancestry of the different lemur species on the island of Madagascar?
Due to variation in the ancestral lemur population, certain individuals were able to better exploit resources and leave more surviving offspring in novel habitats.
Which of the following statements is true about the Miller-Urey experiment?
During the experiment, the scientists generated a variety of amino acids by exposing gases in a chamber to an electric spark
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. Table 1. Number of nucleotide differences in Gene X for five species
E,D,A,C,B
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.
Greater prairie chicken populations in Illinois have little genetic diversity and are therefore at risk of decline. Because of the bottleneck the greater Prairie chick in populations in illinois's are less likely to contain individuals that can withstand a certain environmental pressure
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?
I and II
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?
Introduce a small number of panthers from a genetically distinct population into the at-risk population
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?
Marmosets share a more recent common ancestor with dogs than with tenrecs.
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? Choose 1 answer:Choose 1 answer:
Marmosets share a more recent common ancestor with dogs than with tenrecs.
Which biological molecules were generated during the Miller-Urey experiment?
Only amino acids
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?
Rodents from the two populations interbreed and produce viable offspring
The following graph shows the number of tetrapod (four-limbed animal) families on Earth over time, as indicated by the fossil record. The arrows indicate major mass extinction events. Which of the following statements is consistent with the information provided in the graph?
Tetrapods underwent an adaptive radiation after the end-Cretaceous extinction, likely due to the use of ecological niches made available by the extinction event.
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? Choose 1 answer:Choose 1 answer:
The 2010 population has fewer unique alleles than the 1975 population.
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?
The extinction was due to large-scale ecological changes.
Scientists have found evidence of five major mass extinction events during Earth's history. One of these, the Late Devonian extinction, resulted in the extinction of roughly 75% of Earth's species. These included marine invertebrates and all species of armored fish. One cause of the Late Devonian extinction was the rise of land plants which consumed carbon dioxide from the atmosphere and caused the release of nutrients into the oceans. This led to global cooling, and a reduction in ocean oxygen levels. Which of the following describes how the Late Devonian extinction was similar to Earth's other four major mass extinctions events?
The extinction was due to widespread ecological changes.
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?
The fish population in each lake will become reproductively isolated, resulting in allopatric speciation.
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? Choose 1 answer:Choose 1 answer:
The new population's allele frequencies are different from those in the original population.
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?
The spider population on each side of the lava flow will become reproductively isolated, resulting in 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? Choose 1 answer:Choose 1 answer:
The weed population will evolve resistance to the herbicide, likely through selection of plants with a mutation in the ALS gene.
Which of the following describes two species that exhibit a prezygotic mechanism of reproductive isolation?
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.
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?
They will become more similar as a result of gene flow.
Which of the following describes a postzygotic mechanism of reproductive isolation?
Two species of Ensatina salamanders that occur together in the California foothills can mate and form hybrids, but most of the hybrids die before reaching maturity.
Based on the cladogram, which of the following derived characters is shared by kangaroos and foxes but is not present in platypuses?
Viviparity
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.
Wheat yield remained relatively stable until 1942, and then increased dramatically as farmers bred higher-yielding wheat varieties
Which of the following describes the common ancestor of all eukaryotes, but not the common ancestor of all organisms?
a single-celled organism with membrane-bound organelles, linear chromosomes, and spliceosomal introns
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?
arrow from the bottom left going up to the right top corner
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?
gene flow
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?
line going down from the top left to the bottom right
The following diagram represents the generation of mature mRNA in a prokaryotic cell (A) and a eukaryotic 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?
liner chromosomes,
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?
the fossil of an organism with a sprawling gait and middle ear bones, found in a 250-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?
the fossil of an organism with scaloid scales and a bending neck, found in a 375-million-year-old rock layer
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?
the fossil with feathers and long boney tail
Based on the information in the table, which of the following cladograms best represents the evolutionary relationships among the species?
top to bottom finch all chimp frog tuna lance
The following cladogram shows the evolutionary relationships among several groups of animals. Selected derived characters are labeled on the cladogram. Based on the cladogram, which of the following derived characters is shared by chordates and echinoderms but is not present in cnidarians?
Bilateral symmetry
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?
A & C
Which of the following does not describe a human activity that is likely to contribute to extinction in a coral reef ecosystem?
A government establishes a marine protected area that restricts the types of activities that can be carried out in and around the coral reef.
Which of the following does not describe a human activity that is likely to contribute to extinction in a river ecosystem?
A group of organizations works together to remove a dam, opening up miles of river for spawning fish.
After analyzing the data, the scientists determined that because the allele frequencies changed, the wolf population was not in Hardy-Weinberg equilibrium during the time period studied. Which of the following is the most likely reason that the population deviated from Hardy-Weinberg expectations during the study period? Choose 1 answer:Choose 1 answer:
A group of wolves from a separate geographic area migrated into the population.
Which of the following does not describe a human activity that is likely to contribute to extinction in a temperate forest ecosystem?
A nonprofit organization plants millions of trees to help restore logged North American forests.
Which of the following is an example of gene flow?
A sea anemone egg floats from the area inhabited by one population to the area inhabited by another sea anemone population, where it is fertilized.
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?
Allele BBB became fixed in Population 1 as a result of 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. Choose 1 answer:Choose 1 answer:
Allele NNN was lost from Population 2 as a result of genetic drift.
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 statements best expresses the relationship between a population's genetic diversity and its resilience?
As genetic diversity increases, so does resilience.
Which of the following statements support the hypothesis that bats are more closely related to gorillas than to birds? 👁️ Note that there are 2 answers to this question. Choose 2 answers:Choose 2 answers:
Bats and gorillas have one hole behind each eye socket in the skull, while birds have two. Bats and birds have more nucleotide differences in their mitochondrial DNA sequences than bats and gorillas do
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.
Because of the bottleneck, the wild California condor populations are less likely to contain individuals that can withstand a certain environmental change. Wild California condor populations have little genetic diversity and are therefore at risk of decline.
The black-footed ferret is a species of North American mammal that nearly went extinct in the 1980s as a result of habitat destruction and disease. Through captive breeding and reintroduction of populations into their natural habitats, the number of wild black-footed ferrets is slowly increasing. However, because of the population bottleneck, all of the black-footed ferrets that currently exist in the wild are descended from a breeding population of just seven individuals. Which two claims are best supported by the information provided above? 👁️ Note that there are 2 answers to this question.
Because of the bottleneck, the wild black-footed ferret populations are less likely to contain individuals that can withstand changes to their habitats. Wild black-footed ferret populations have little genetic diversity and are therefore still at risk of extinction.
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? Choose 1 answer:Choose 1 a
Birds from each population mate only with birds from their own population.
Which of the following describes a result of artificial selection?
Body size in a population of sheep has decreased due to selective breeding by humans.
Researchers have found that elk populations in a certain national park are small and lacking in genetic diversity, which puts them at risk of extinction. These populations are isolated from each other by busy highways that cut through the national park's land. Which of the following actions can humans take to decrease the risk of extinction for the elk populations?
Build walkways for the elks over highways to promote interbreeding among the populations.
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?
Can organic molecules be generated abiotically in a warm, high-pH environment, similar to that near an alkaline vent?
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?
Can organic molecules be generated abiotically under low temperature and high levels of UV radiation, similar to conditions in space?
Which of the following describes a postzygotic mechanism of reproductive isolation?
Crosses between two species of dwarf hamsters, Phodopus campbelli and P. sungorus, result in embryos with severe developmental defects.
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. Which two of the following pieces of evidence support the RNA World Hypothesis? 👁️ Note that there are 2 answers to this question.
Like DNA, RNA can encode genetic information. Like proteins, RNA can carry out catalytic activities.
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?
Like proteins, RNA can carry out catalytic activities.
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?
Mammals underwent an adaptive radiation after the mass extinction event, likely due to the use of newly available ecological niches.
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?
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? Choose 1 answer:Choose 1 answer:
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.
As a result of adaptive radiation, there are more than 70 species of Bulimulus snails found on the Galápagos islands. These species differ in their shell shape, shell color, and habitat use . Which of the following statements best explains how adaptive radiation could have led to the diversity of Bulimulus snail species found on the Galápagos islands?
Members of a single snail species floated to the islands on debris from the mainland. Over time, this species diverged into many species as groups of snails adapted to different habitat niches on the islands.
As a result of adaptive radiation, there are more than 70 species of Bulimulus snails found on the Galápagos islands. These species differ in their shell shape, shell color, and habitat use. Which of the following statements best explains how adaptive radiation could have led to the diversity of Bulimulus snail species found on the Galápagos islands? Choose 1 answer:Choose 1 answer:
Members of a single snail species floated to the islands on debris from the mainland. Over time, this species diverged into many species as groups of snails adapted to different habitat niches on the islands.
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? Choose 1 answer:Choose 1 answer:
Oystercatchers share a more recent common ancestor with flamingos than with penguins.
Based on the experimental results, which of the following is the best evolutionary explanation for the presence of a stalk on B. ringens plants?
Plants with stalks attract more pollinators, enabling them to produce more offspring in each generation than plants without stalks.
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.
Population 2 was likely smaller than Population 1 during the study period.
A group of researchers grows two populations of rice in separate, equal-sized fields. Population 1 is made up of multiple varieties of rice, each variety having a unique set of traits. Population 2 is made up of a single variety. Both rice plant populations have similar population densities. The researchers introduce a fungal pathogen to both populations, making sure to apply roughly equal numbers of spores to each field. Which of the following is the best prediction for how the fungal pathogen will affect the two rice populations?
Population 2 will be more severely affected because it has less allelic diversity than Population 1.
Coral gobies are a type of fish that rely on coral for shelter and breeding sites. A scientist is studying populations of coral gobies within a single reef off the coast of Papua New Guinea. Most of the populations in the reef prefer the coral species Acropora tenuis. However, the researchers have found that one population, referred to as Population B, has recently shifted hosts, now preferring the coral A. caroliniana. Coral gobies strongly prefer their host corals as breeding sites, so it is unlikely that Population B will continue to interbreed with the other populations in the reef. Which of the following best predicts how the shift in coral host will affect Population B over time?
Population B will become reproductively isolated from the other coral goby populations, resulting in sympatric speciation.
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 statements is best supported by the data in the table?
Species D is more closely related to Species A than to Species E.
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?
Statements I, II, and III
Consider the following statements: I. Eukaryotes and prokaryotes exist on every continent on Earth. II. Bacteria, eukaryotes, and archaea use ATP to power cell processes. III. Organisms from all domains use DNA to encode proteins, which carry out cellular functions. Which of the statements provide evidence that all of Earth's organisms are descended from a common ancestor? Choose 1 answer:Choose 1 answer:
Statements II and III
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?
The SARS coronavirus is more likely to evolve antiviral drug resistance over a given time period than the human hepatitis B virus.
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? Choose 1 answer:Choose 1 answer:
The bacteria population will evolve resistance to the antibiotics, likely through selection of individuals with a mutation in the PBP2 gene.
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?
The barley yellow dwarf virus is more likely to overcome engineered virus resistance in plants than the maize streak virus is.
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?
The hillside population will be less severely affected because it is more likely to have individuals with some level of resistance to the pathogen.
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?
The orchard population will be more severely affected because it has less allelic diversity than the jungle population.
The following graph shows species number over time for a certain class of organisms. A mass extinction event is indicated by an arrow. Which of the following statements is most consistent with the information provided in the graph?
The organisms underwent an adaptive radiation after the mass extinction event, likely due to the use of newly available ecological niches.
Pink bollworms are a major pest of cotton, causing huge crop losses around the world. To prevent pink bollworm infestation, some farmers grow cotton plants that have been engineered to produce the insecticide Bt. When a bollworm feeds on a Bt-producing cotton plant, the Bt enters the insect's midgut and binds to proteins called cadherins. This binding damages the insect's midgut, eventually causing death. Which of the following best predicts what will happen over time to a pink bollworm population in a field that is planted entirely with Bt-producing cotton plants?
The pink bollworm population will evolve resistance to Bt, likely through selection of bollworms with a mutation in the cadherin gene
Which of the following statements is most likely true about the plant population immediately after the wildfire?
The population is more likely to be significantly impacted by ongoing genetic drift.
According to this cladogram, tigers are more closely related to snow leopards than to jaguars. Which of the following statements provides the best justification for this relationship?
Tigers share a more recent common ancestor with snow leopards than with jaguars.
A population of yarrow plants is growing in a meadow. In one plant, a mutation occurs in the egg cell of a flower. Meanwhile, a pollen grain from a separate, hillside yarrow population is brought to the meadow on the leg of a bee. This pollen grain fertilizes a yarrow plant in the meadow population. Does the passage describe any new alleles entering the meadow population of yarrow plants?
Yes, both the mutation and the movement of the pollen grain introduce new alleles.
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 barley yield measured in tons per hectare in Chile from 1945-2010.
Barley yield began to increase dramatically after 1975 due to selective breeding of higher-yielding barley plants.