1 markIn a population of deer, individuals with thicker fur are more likely to survive and reproduce in a colder environment. Over several generations, the frequency of the thick-fur trait increases in the population.
What does this scenario best illustrate?
Genetic drift
Natural selection
Artificial selection
Founder effect
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1 markA bacterial population is exposed to an antibiotic. While most bacteria die, some survive due to a pre-existing resistance gene. Over generations, the proportion of antibiotic-resistant bacteria increases.
What best explains the increase in antibiotic resistance?
The bacteria developed resistance because they needed to survive
The bacteria acquired resistance by exchanging genetic material
The resistant bacteria had a genetic advantage that was passed to their offspring
All bacteria mutated at the same rate in response to the antibiotic
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1 markA population of rabbits lives in a snowy environment. Over generations, the proportion of white-furred rabbits increases while the number of brown-furred rabbits decreases.
What is the most likely explanation for this change?
White rabbits have higher fitness because they are less visible to predators.
Brown rabbits changed their fur color in response to the snowy environment.
White rabbits developed their coloration due to a mutation caused by snow.
The change was due to random genetic drift with no connection to the environment.
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1 markDifferent species can evolve similar traits due to similar selective pressures in their environments, even though they do not share a recent common ancestor.
Which of the following scenarios best represents convergent evolution?
A population of salamanders is split into two groups by a river. Over time, the two groups develop different coloration patterns due to changes in predation.
Bats and birds both have wings, which allow them to fly, despite their ancestors not being closely related.
Two closely related species of lizard in a desert environment evolve to have longer legs, making them better suited to their habitat.
A species of butterfly evolves a new color pattern due to a random genetic mutation that spreads through the population.
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1 markA deadly fungal disease spreads through a population of frogs. Some frogs have a genetic mutation that makes them resistant to the fungus, while others do not. Over several generations, the percentage of resistant frogs in the population increases.
Why is genetic variation important for the survival of the frog population?
It allows some individuals to survive and reproduce when environmental conditions change.
It prevents natural selection from acting on the population.
It ensures that all individuals in the population will survive a disease outbreak.
It causes mutations to occur in response to environmental changes.
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1 markScientists studied the effects of a drought on a population of seed-eating finches living on an island in the Galapagos. They assessed beak depth data prior to the drought, collected in 1976, and compared it to beak depth data recorded after the drought in 1978. Their results are shown in Figure 1 below.
Which of the following is the most likely explanation for the results shown in Figure 1?
Finches with the mean beak depth in 1976 had the greatest reproductive fitness after the period of drought.
Plants that produced smaller seeds were killed by the drought, changing the favorable beak phenotype.
The finch population in 1976 had little phenotypic variation, limiting the rate of natural selection.
The drought caused a mutation in the gene for beak length in finches, resulting in a new favorable phenotype.
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1 markAfrican lions face challenges in their natural habitat, including competition for food, a hot climate and limited water sources. These factors contribute to population regulation.
Which of the following best describes these challenges in the context of natural selection?
Artificial selection pressures
Evolutionary fitness indicators
Environmental factors
Phenotypic variations
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1 markThe rock pocket mouse (Chaetodipus intermedius) is found in rocky areas of the southwestern United States and Mexico. These mice typically have a light-colored coat that blends with the rocks in their habitat. However, in some areas with dark lava rocks, populations of dark-colored mice are found. Researchers conducted a study to investigate the relationship between rock color and mouse coat color. They surveyed mouse populations in four different locations with varying proportions of dark lava rock coverage. Figure 1 shows the results of their study.
Which of the following best explains the relationship observed in Figure 1?
Researchers carried out artificial selection to breed dark-colored mice.
The abiotic environment is fluctuating, resulting in natural selection.
Natural selection is acting on phenotypic variation in the mouse population.
Natural selection is acting on phenotypic variation in the predators of the mouse population.
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1 markA breeder is interested in improving the sprinting speed of racehorses. They test the speed of two groups of horses over five generations. Group A consists of horses selectively bred for sprinting, while group B consists of randomly selected horses. The table below shows the average sprint speed for each group across five generations:
Generation | Average sprinting speed (m/s) | |
|---|---|---|
Group A | Group B | |
1 | 15 | 14 |
2 | 16 | 14 |
3 | 17 | 14 |
4 | 18 | 15 |
5 | 19 | 15 |
Which of the following conclusions can be drawn from the data?
All offspring that are selectively bred have alleles for fast sprinting speed.
Random breeding increases sprinting speed at the same rate as selective breeding.
Selective breeding increases sprinting speed at a higher rate than random breeding.
Sprinting speed does not change over time in randomly bred horses.
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1 markClimate change is affecting the phenology (timing of life cycle events) of many species, an observation that some scientists believe could be driven by natural selection. Researchers studied the effects of warming temperatures on the egg-laying dates of great tits (Parus major) in the Netherlands between 1955-2012. They also monitored the peak abundance of winter moth caterpillars, the primary food source for great tit chicks. Figure 2 shows the results of their long-term study.
Which of the following correctly describes the data in Figure 2?
The average spring temperature increased at an average rate of around 0.14 °F year-1 across the period of the study.
The date of peak caterpillar abundance is always earlier in the year than the average egg-laying date of the great tits.
The average great tit egg-laying date in 2010 is April 1st.
Caterpillar abundance and average egg-laying date of great tits become earlier each year at the same average rate.
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1 markThe graph shows the result from a study on two populations of wheat plants that have undergone artificial selection for drought resistance.
Which of the following best explains the data seen in the graph?
Population A underwent more frequent mutations than Population B.
Population A had a greater range of genetic variation for drought resistance traits.
Artificial selection caused new beneficial alleles to arise in Population A.
Population B experienced genetic drift, which eliminated drought resistance alleles.
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1 markA group of biologists studies a population of fish in a lake over 50 years. Initially, the population consists of a mix of small-bodied and large-bodied individuals. After a predatory species is introduced to the lake, the scientists observe a shift toward a higher frequency of small-bodied individuals in the population.
Which of the following experimental designs would best test whether this change is due to natural selection?
Measuring body size and predation rates over multiple generations while controlling for environmental variables.
Removing all predators from the lake and measuring fish body size in the next generation.
Comparing the body size of fish in the lake to fish in another lake without predators.
Genetically modifying fish to produce only large-bodied individuals and observing survival rates.
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1 markTwo species of fish live in separate rivers but have evolved similar streamlined body shapes and specialized gill structures that allow them to survive in fast-moving water. A student claims that these traits are an example of convergent evolution.
Which of the following would best support the student’s claim?
Genetic analysis shows that the two species share a recent common ancestor.
The two fish species occupy different ecological niches within their respective rivers.
Fossil evidence shows that ancestors of the two fish species had different body shapes.
The two species exhibit similar body structures, but one is an amphibian and the other is a reptile.
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1 markFigure 1. below shows allele frequencies of two alleles in three different populations changed over several generations.
Which of the graphs depict changes in allele frequency that indicate evolution is occurring?
II only
II and III only
III only
I, II and III
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1 markMalaria, a life-threatening disease, is caused by a parasite that attacks red blood cells. In the West African country of Burkina Faso, scientists have found a link between hemoglobin formation in red blood cells, and susceptibility to malaria. They studied two alleles involved in hemoglobin synthesis.
HbA is a healthy allele
HbC is a mutated allele which results in mild anemia in homozygous individuals
The graph below shows the effect of the HbC allele on the percentage of individuals contracting malaria.
Which of the following best explains the evolutionary advantage of the HbC allele in certain human populations?
The HbC allele provides a selection pressure in malaria-prone regions leading to an increase in allele frquency.
A homozygous HbC genotype offers a 95% reduction in malarial infection but evolutionary fitness cannot be determined without more information about reproductive success of homozygous individuals.
The increasing frequency of HbCHbC is due to genetic drift, where random fluctuations in allele frequencies—rather than natural selection—lead to its rise in populations affected by malaria.
Heterozygous individuals show the strongest resistance to malaria due to heterozygote advantage, which directly selects for the allele’s spread in populations with high malaria prevalence.
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1 markIn adult humans, the ability to digest the lactose sugar in milk depends on the presence of an allele known as -13910*T. Individuals with this allele continue to produce the enzyme lactase into adulthood; this is known as lactase persistence. Individuals without this allele are not able to produce lactase after infancy and cannot digest lactose as adults. The table below shows the frequency of the -13910*T allele in European Neolithic hunter-gatherers who lived around 5 000 years ago and in modern Europeans.
| European Neolithic hunter-gatherers | Modern Europeans |
Frequency of -13910*T allele | 0.03 (+/- 0.11) | 0.74 (+/- 0.06) |
Which of the following can be concluded from the table?
There is no significant difference in the frequency of the -13910*T allele between Neolithic hunter-gatherers and modern day humans in Europe.
Lactase persistence gave a survival advantage to humans at some stage between Neolithic and modern-day times.
Lactase persistence gave a survival advantage to European Neolithic hunter-gatherers.
Adult European Neolithic hunter-gatherers did not consume milk.
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