CBSE Questions for Class 12 Medical Biology Evolution Quiz 15 - MCQExams.com

A large population of zebrafish has been allowed to breed randomly for a number of generations in a laboratory.
After ten generations, 25% of the fish display a recessive genotype (dd), the same percentage as at the beginning of the breeding program. The rest of the fish show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What is the most reasonable explanation of the fact that the frequency of the recessive genotype (dd) at generation ten is the same as the frequency of the recessive genotype (dd) at generation one?
  • Sexual selection occurred that favoured allele d
  • The genotype DD is lethal
  • The population is undergoing genetic drift
  • The two phenotypes are equally adaptive under laboratory conditions
One way to classify humans is by their blood type. There are over two dozen ways to group blood types. One of them is by the presence of the D antigen on the surface of blood cells. If an individual expresses the D antigen, they are referred to as Rh positive. This is controlled by an autosomal dominant allele. In a given town, 16% of the population is considered Rh negative.
If this town's high school has 2,000 students, how many would you expect to be heterozygous for the D antigen?
  • 160
  • 320
  • 720
  • 960
The medium ground finch is a species of bird endemic to the Galapagos Islands that eats by cracking seeds open with their beaks to obtain the food inside. Finch beak size (depth) is controlled by the BMP4 gene, which produces a growth factor known as bone morphogenic protein. In 1977 the Galapagos Islands experienced an intense drought, which severely reduced the population of small seeds and the plants that produced them.
Figure 1 above illustrates the changes in the distributions of finch beak depths (size) before and after the drought ofThe mean depth is indicated above the caret symbol (^).
Which of the following statements best explains the trend in finch beak size during 1976 - 1978?
525235_282345e2b9f1447a9c094fb680aaec18.png
  • Finches with larger beaks must have a higher degree of expression of the BMP4 gene, and are better adapted to cracking larger seeds and producing more surviving offspring.
  • Finches with larger beaks are the result of a mutation that prevents expression of the BMP4 gene, and are better adapted to cracking larger seeds and producing more surviving offspring
  • Finches that have a higher degree of expression of the BMP4 gene have smaller beaks that are better adapted to cracking small seeds, producing a larger proportion of offspring with smaller beaks.
  • Higher expression of the BMP4 gene leads to better scavenging behaviors, which allows finches to locate seeds more easily, and produce more surviving offspring.
Thale cress (Arabidopsis thaliana) is a small, quickly reproducing, edible plant. It has a gene locus with an allele that results in a tolerance to heavy metals, which can leech into the soil as a result of mining operations.
A genetics professor has been using a population of thale cress for a Spring semester class to practice genetic analysis skills. The professor continues using the population after a mine in started near the collection location. The professor tracks their data from year to year. The graph displays the data for the allele frequencies for a heavy metal tolerance gene. Based on the evidence, during what year was the mine built?
525197_ca249c796edc4f4ab582869f14c30d71.png
  • 2002
  • 2003
  • 2005
  • 2006
In a hypothetical situation, the Vermont State Park Service decides to build a pedestrian bridge over the Rock River in the town of Newfane. Upon completion, the pedestrian bridge will enable the passage of two closely related populations of mud lizards that had previously existed either on the eastern or the western side of the river but had been unable to cross the river.
Just before completion of the bridge and then fifteen years after the completion of the bridge, graduate students from the University of Vermont collected twenty-five lizards from each side of the river, took blood samples, and determined the frequencies of alleles that were unique to the two types of mud lizards. The results of their sampling are shown in the graphs below.
The data from the students' investigation show which of the following?
525271_aca913cb691245279ef2dd962e7c45d2.png
  • The completion of the bridge allowed for the formation of a hybrid zone between the Eastern and Western mud lizards.
  • The Eastern and Western mud lizards did not intermix despite the construction of the bridge.
  • Gene flow occurred from the Eastern mud lizard gene pool into the Western mud lizard pool.
  • The two mud lizard populations intermixed after the completion of the bridge, but they did not hybridize.
A large population of zebrafish has been allowed to breed randomly for a number of generations in a laboratory.
After ten generations, 25% of the fish display a recessive genotype (dd), the same percentage as at the beginning of the breeding program. The rest of the fish show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What is the most reasonable explanation of the fact that the frequency of the recessive genotype (dd) at generation ten is the same as the frequency of the recessive genotype (dd) at generation one?
  • Sexual selection occurred that favored allele d.
  • The genotype DD is lethal.
  • The population is undergoing genetic drift.
  • The two phenotypes are equally adaptive under laboratory conditions.
It makes sense that a human with excessive body odour may have trouble convincing other people to date them. Beyond that, most people probably don't think that smell is a major factor in deciding who to date or have children with.
However, evidence suggests that there is a connection between personal odor and immune genes. Studies indicate that humans prefer the odor of individuals whose immune system genes are different than their own.
What could be the evolutionary benefit of people with different immune system alleles mating?
  • Over time, the number of individuals with the dominant phenotype for immune genes will increase, strengthening the population.
  • The number of individuals that are homozygous for immune genes will increase in the population, making it more likely that an advantageous trait will be passed on in future generations.
  • The resulting offspring will have a more diverse set of immune genes, protecting the population against a wider range of diseases.
  • The resulting offspring will smell better and will be sexually selected for, increasing the more pleasant smelling individuals in the population.
The Hardy-Weinberg equation for a gene with two alleles is as follows:
$$p^2+2pq+q^2=p+q=1$$
Which part of the equation represents the frequency of one of the alleles?
  • $$2pq$$
  • $$p$$
  • $$p^2$$
  • $$p^2+2pq$$
In 2012, Ryan Clark of the Pittsburgh Steelers was forced by his coach to sit out of a playoff game in Denver due to health concerns. Clark is a heterozygote for sickle cell anemia.
Sickle cell anemia is a recessive condition that results in misshapen red blood cells due to a mutation in the hemoglobin gene. The condition greatly reduces the ability of red blood cells to carry oxygen.
Heterozygotes generally do not have symptoms of the condition, but will sometimes have problems when dehydrated or at high altitudes. In addition to reduced oxygen carrying ability, the sickle cell allele has another trait; resistance to malaria.
Some areas of the world have a sickle cell allele frequency of up to nearly 20%. What would you expect to find in areas of the world with high sickle cell frequencies?
  • Dry climate
  • High altitude
  • Low rates of malaria
  • Low atmospheric oxygen
A fictional lizard population has a gene called FireThe dominant allele of this gene allows the lizard to produce a combustion reaction from glands in the back of their throat. A second gene, Fire 2, codes for a protein that suppresses the expression of the Fire 1 gene.
The lizard population is not fire breathing, but genetic analysis reveals that a majority of the lizards have at least one copy of the dominant Fire 1 allele. Which of the following would be expected if a mutagen that targets the Fire 2 gene was released into the lizard's environment?
  • Genetic variation will decrease as new mutations occur.
  • Phenotypic variation will decrease as the frequency of fire breathing lizards decrease.
  • Phenotypic variation will increase as some lizards will express the fire breathing trait.
  • Variation will not change because any mutations that occur will not affect the Fire 1 gene.
Scientists discover a unicellular organism growing on the surface of a meteorite recently recovered from a site in Russia. The meteorite struck the planet just seven days prior to being discovered, and the scientists wonder whether or not the organism is extraterrestrial.
Which of the following observations about the organism provides the best evidence that the organism evolved on earth?
  • The organism is able to lower the activation energy of many spontaneous reactions so that they progress at temperatures low enough to support life.
  • The organism is able to synthesize polymer molecules by joining monomer molecules in sequence.
  • The organism requires a constant input of energy from its environment to survive.
  • The organism uses ATP molecules to drive many of its anabolic reactions.
In certain African countries, 4% of the newborn babies have sickle cell anemia, which is caused by a recessive version of the hemoglobin gene. Twenty years later, only 0.3% of the population have this homozygous genotype.
Which of the following is the best explanation for this change in genotypic frequency?
  • Members of the population that have the homozygous recessive genotype emigrated from their country of birth.
  • Many individuals that are homozygous recessive did not survive the early years of development due to the complications associated with sickle cell anemia phenotype.
  • Malaria killed off all those with sickle cell anemia, as having the homozygous recessive genotype makes an individual more susceptible to that disease.
  • The population was in Hardy-Weinberg equilibrium.
Ellis-van Craved syndrome is an inherited condition affecting bone growth. The primary symptom is short stature. Other symptoms include abnormal numbers of finger and toes, and tooth and nail abnormalities. Some individuals with the condition have heart abnormalities.
The frequency of the condition in most populations is low. However, the condition occurs at a much higher rate in the Amish population descended from a group who migrated from Europe to Pennsylvania in the 1700's.
Which of the following explains the difference between the Amish frequency of the condition and the frequency of the population they migrated from?
  • An early member of the migrant population was a carrier for the condition.
  • Inbreeding in the migrant population caused new mutations leading to the condition.
  • The difference in environment between Europe and Pennsylvania caused the Ellis-van Craved alleles to be selected for, increasing the frequency.
  • The frequency of Ellis-van Craved syndrome had been higher in the worldwide population in the 1700's. The frequency stayed the same in the Amish population while decreasing in the rest of the world.
A population of squirrels has 100 black individuals and 400 grey individuals.
What is the phenotype frequency of black squirrels?
  • 0.04
  • 0.2
  • 0.25
  • 0.45
One way to classify humans is by their blood type. There are over two dozen ways to group blood types. One of them is by the presence of the D antigen on the surface of blood cells. If an individual expresses the D antigen, they are referred to as Rh positive. This is controlled by an autosomal dominant allele. In a given town, 16% of the population is considered Rh negative.
If this town's high school has 2,000 students, how many would you expect to have the homozygous recessive genotype?
  • $$160$$
  • $$320$$
  • $$480$$
  • $$720$$
In the late 1970's, the Galapagos Islands experienced a severe drought that sharply reduced the finch population living there. It was discovered that only finches with large, thick beaks survived the drought as they subsisted on cactus, which are drought tolerant plants.
In the early 1980's, the Galapagos Islands underwent an El Nino event that led to higher annual levels of precipitation than normal. This climate event occurred just a few years after the drought. The increase in rainfall led to a dramatic increase in growth of seed-producing plants, which led to an abundance of foods for seed-eating finches, which have small, short beaks.
The increase in rainfall also decreased the availability of cactuses on the islands. Which of the following would you predict occurred in the finch population as a result of the second change in climate? 
  • The variety present in the finch population did not change due to changes in climate.
  • The population of short-beaked finches increased while the population of large beaked birds decreased.
  • The large-beaked finches increased in number while the short-beaked finches decreased in number.
  • The number of finches of each type both decreased due to the change in climate.
  • The large-beaked finches hybridized with the short-beaked finches.
In prairie chickens the gene for throat sac size shows simple dominant-recessive inheritance. A recessive allele causes small throat sacks and a dominant allele causes large throat sacks. In a certain population of chickens, 264 chickens show the recessive phenotype and 788 chickens show the dominant phenotype.
What is the frequency of the homozygous recessive genotype?
  • $$0.75$$
  • $$0.5$$
  • $$0.25$$
  • $$1$$
In The Princess Bride Inigo Montoya has spent his adult life seeking revenge on the six fingered man who killed his father. Polydactyly, the presence of extra fingers or toes, is caused by a dominant allele.
If five individuals per 1000 births is affected by the condition, what is the frequency of the polydactyly allele?
  • 0.003
  • 0.005
  • 0.071
  • 0.995
Human earwax texture is determined by a single gene with two alleles, wet and dry. Dry is recessive and wet is dominant.
Evidence suggests that the dry allele first appeared in Eastern Asia about 2,000 generations ago. The frequency of the dry allele in a European population is .What percentage of this population is expected to have the wet earwax phenotype?
  • 0.02
  • 0.26
  • 0.72
  • 0.85
In a particular population of mice that lives in the Southwestern United States, there are two fur color variants: black and light brown. The black fur is a dominant trait in these mice. The population described lives in an area dominated by dark-colored rock and that is populated by owls that prey upon mice that do not blend into the environment. The frequency of the black fur allele in this particular population is 0.6.
If the rock were to become covered by sand dunes, what change in the population would you predict? 
  • The frequency of the dark fur color would increase.
  • The frequency of the light fur color would decrease.
  • The frequency of the dark fur color would decrease.
  • The frequency of the allele for fur color would remain the same.
  • The allele .frequencies for dark and light fur color would become equai.
Examine the data showing the percent identity of the GAPDH gene and protein sequences between humans and the three species shown below.
SpeciesGene IdentityProtein Identity
Chimpanzee99.6%100%
Fruit Fry72.4%76.7%
Roundworm68.2%74.3%
Provide a plausible reason for why the percent identity between gene sequences is lower than the percent identity of protein sequences.
  • Multiple codons code for the same amino acid.
  • Introns are likely to have different sequences.
  • Differences in DNA sequences are edited when the mRNA is transcribed.
  • Amino acids cannot be substituted without consequence.
Lake Victoria is home to hundreds of species of cichlids, a brightly colored variety of freshwater fish commonly kept as an aquarium pet. Each species has slightly different diets, behaviors, and habitats within the lake.
These fishes likely diverged from a common ancestor as the result of 
  • Sexual selection
  • Convergent evolution
  • Genetic drift
  • Gene flow
  • Isolation
The CCR5 gene codes for a protein on the surface of T cells. The CCR5 protein is used by Human Immunodeficiency Virus (HIV) to enter T cells, which ultimately leads to Acquired Immunodeficiency Syndrome (AIDS). AIDS was first reported in the European population in the early 1980s.
About 3000 years ago in Central-Western Europe a mutation occurred that prevents normal expression of the surface protein. People with one copy of the mutated allele have delayed onset of AIDS. Homozygotes for the mutation are resistant to HIV infection.
Evidence suggests that the trait also protects individuals from the smallpox virus. Smallpox was common in the European population from the Middle Ages until the early 1900s, causing several major epidemics with high death rates. It was eradicated through widespread vaccination.

The frequency of the allele is 16% in Scandinavia and 4% in Greece. What are the expected frequencies of HIV-resistant individuals in each population and which evolutionary explanation for the difference is most plausible?
  • The frequency of resistant individuals is expected to be .0256 in Scandinavia and .0016 in Greece. Environmental factors caused historically higher mutation rates in the Scandinavian population, leading to the formation of more copies of the resistance allele.
  • The frequency of resistant individuals is expected to be .0256 in Scandinavia and .0016 in Greece. Higher rates of smallpox infections in Scandinavia created a selection pressure for the resistance allele.
  • The frequency of resistant individuals is expected to be .2688 in Scandinavia and .0768 in Greece. HIV is causing natural selection for the resistance allele.
  • The frequency of resistant individuals is expected to be .2688 in Scandinavia and .0768 in Greece. Scandinavian populations were isolated for much of European history, leading to genetic drift and increasing the frequency of the resistance allele.
One way to classify humans is by their blood type. There are over two dozen ways to group blood types. One of them is by the presence of the D antigen on the surface of blood cells. If an individual expresses the D antigen, they are referred to as Rh positive. This is controlled by an autosomal dominant allele. In a given town, 16% of the student population is considered Rh negative.
If this town's high school has 2,000 students, how many would you expect to be heterozygous for the D antigen?
  • $$160$$
  • $$320$$
  • $$720$$
  • $$538$$
Which of the following questions would best be tested using mathematical modeling?
  • How has climate change affected the survival rate of polar bear cubs?
  • If 75% of individuals with a dominant phenotype do not reproduce, how many generations will it take for the dominant allele to be eliminated from the population?
  • What is the inheritance pattern of a newly discovered fruit fly eye color trait?
  • What is the minimum concentration of DDT that will kill mosquitoes?
At a particular locus, frequency of '$$A$$' allele is $$0.6$$ and that of '$$a$$' is $$0.4$$. What would be the frequency of heterozygotes in a randomly mating population of equilibrium?
  • $$0.16$$
  • $$0.36$$
  • $$0.48$$
  • $$0.24$$
Find the mis-match from the following pairs.
  • Divergent evolution $$\rightarrow$$ Thorn from of bougainvillea and tendril of Cucurbita
  • Adaptive radiation $$\rightarrow$$ Australian marsupials
  • Natural selection $$\rightarrow$$ Industrial melanism
  • Genetic drift $$\rightarrow$$ Constant gene frequency
During which geological period of evolution did the greatest diversification of life occurred on the earth?
  • Permian
  • Jurassic
  • Cambrian
  • Ordovician
9% of Hardy-Weinberg population of 800 individual recessives. How many of this population are heterozygous?
  • 336
  • 392
  • 372
  • 362
Thorns of Bougainvillea and tendrils of Cucurbita are examples for 
  • Retrogressive evolution
  • Analogous organs  
  • Homologous organs
  • Vestigial organs
All plants and animals were created and perpetuated themselves without any change, is the theory of genesis given by
  • Hulton
  • Cuvier
  • Haldane
  • Oparin
Convergent evolution in closely related species is called 
  • Adaptive radiation
  • Divergent evolution
  • Parallel evolution
  • Both A and C
Identify the correct equation for Hardy-Weinberg law.
  • $$p + q = 1$$
  • $$p - q = 1$$
  • $$(p + q)^3 = 1$$
  • $$(p - q)^2 = 1$$
The Hardy-Weinbury principle cannot operate if
  • The population is very large
  • Frequent mutations occur in the population
  • The population has no chance of interaction with other populations
  • Free interbreeding occurs among all members of the population
Fossils of early vascular plants have been discovered in the rocks of
  • Cambrian
  • Silurian
  • Devonian
  • Jurassic
Dinosaurs became extinct in
  • Permian
  • Jurassic
  • Triassic
  • Cretaceous
Frequency of an autosomal recessive lethal gene is $$0.4$$. Frequency of carrier in a population of $$200$$ individuals is?
  • $$72$$
  • $$96$$
  • $$104$$
  • $$36$$
Long neck of camels is due to:
  • Increase in number of cervical vertebrate.
  • Increase in length of cervical vertebrate.
  • Development of muscular pads between successive vertebrae.
  • Development of extra bony plates between successive vertebrae.
Which process of inheritance is in violation of Hardy-Weinberg law?
  • Lamarckian process of inheritance
  • H.J. Muller's concept
  • Sewal Wright effect
  • G.L. Stebbin's concept
Rhynia belongs to
  • Silurian
  • Devonian
  • Carboniferous
  • Permian
Members of hominidae are
  • Man, Lemur, Ape
  • Man, Chimpanzee, Gorilla
  • Monkey, Ape, Lemur
  • Chimpanzee, Lemur, Ape
Mesozoic era was dominated by
  • Gymnosperms
  • Mammals
  • Dinosaurs
  • Fishes
As evidence from records which era had no life
  • Azoic
  • Proterozoic
  • Paleozoic
  • Coenozoic
Identify the correct order from the given options.
  • Palaeozoic $$\rightarrow $$ Archaeozoic $$\rightarrow $$ Coenozoic
  • Archaeozoic $$\rightarrow $$ Palaeozoic $$\rightarrow $$ Proterozoic
  • Palaeozoic $$\rightarrow $$ Mesozoic $$\rightarrow $$ Coenozoic
  • Mesozoic $$\rightarrow $$ Archaeozoic $$\rightarrow $$ Proterozoic
The epoch of man in geological period is 
  • Pliocene
  • Oligocene
  • Miocene
  • Pleistocene
In which period of paleozoic era first vertebrate appeared 
  • Ordovician
  • Devonian
  • Silurian
  • Mississipian
Which animal dominated in paleozoic era?
  • Reptiles
  • Fishes
  • Birds
  • Mammals
Geological time scale was first developed by 
  • Leonardo da Vinci
  • Georges Caviar
  • Giovanni Avaduina
  • Boltwood
Golden Age of Dinosaurs'/Age of reptiles was 
  • Mesozoic
  • Coenozoic
  • Palaeozoic
  • Psychozoic
Birds and mammals in geological development of earth arose in period
  • Permian
  • Carboniferous
  • Jurassic
  • Oligocene and Eocene
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