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Modern Evolutionary Theory and Genetic Basis of Evolution

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Question 1Question →

A sudden environmental change occurs in a habitat, favoring beetles with darker pigmentation. According to modern evolutionary theory (Neo-Darwinism), which of the following best explains the genetic basis for how this beetle population evolves over successive generations?

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Answer: Pre-existing gene mutations in germ cells provide dark allele variations, increasing in frequency over generations as natural selection favors darker individuals.

Answer

Pre-existing gene mutations in germ cells provide dark allele variations, increasing in frequency over generations as natural selection favors darker individuals.
Modern evolutionary theory (Neo-Darwinism) explains evolution as a change in allele frequencies within a population over time. Gene mutations in germ cells create heritable variations in the gene pool. When environmental conditions change, individuals carrying advantageous alleles experience greater reproductive success, causing those favorable alleles to become more common in the population over successive generations.

Step-by-Step Solution

1
Identify the core principle of Modern Evolutionary Theory (Neo-Darwinism).
Neo-Darwinism integrates Mendelian genetics with Darwinian natural selection, emphasizing that evolution is driven by changes in gene/allele frequencies within a population's gene pool.
Evolution occurs at the population level through genetic inheritance, not at the individual level through somatic modifications.
2
Evaluate the origin and transmission of evolutionary variation.
Random gene mutations occurring in germline cells generate new alleles, creating heritable genetic variation.
Only mutations in germ cells (gametes) are transmissible to offspring, serving as raw material for selection.
3
Determine the effect of natural selection on allele frequencies.
Individuals possessing favorable alleles (darker pigmentation) have higher differential reproductive success, increasing the dark allele frequency in subsequent generations.
Differential survival and reproduction lead to adaptation over generational time.

Key Concept

Modern Evolutionary Theory (Neo-Darwinism) and Population Genetics
Question 2Question →

In a stable mainland population of a wildflower species, the frequency of a recessive allele (aa) causing albino foliage is 0.30.3. A small group of 10 seed-bearing plants is accidentally carried by wind to an isolated oceanic island where no other members of the species exist. In the newly established island colony, the frequency of allele aa is found to be 0.70.7 purely due to sampling chance during colonization. Which evolutionary force best accounts for this rapid change in allele frequency, and what is its primary consequence on the island's gene pool?

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Answer: Genetic drift via the founder effect, which reduces overall genetic variation in the new population regardless of natural selection.

Answer

Genetic drift via the founder effect, which reduces overall genetic variation in the new population regardless of natural selection.
The correct answer identifies the founder effect—a key mechanism of genetic drift in modern evolutionary theory. When a small group of individuals colonizes a new geographical area, the alleles carried by the founders determine the new gene pool. By chance alone, allele frequencies in the colonizing group differ markedly from the source population, which decreases overall genetic diversity independently of natural selection.

Step-by-Step Solution

1
Analyze the cause of the allele frequency shift in the population
A very small sample size (10 plants) colonized an isolated island, shifting the recessive allele frequency from 0.30.3 to 0.70.7 purely due to sampling chance.
When a small fragment of a population colonizes a new area, the allele frequencies of the founders rarely match the ancestral gene pool.
2
Identify the primary evolutionary mechanism
Random fluctuations in allele frequency resulting from small colony founding represent the founder effect, a form of genetic drift.
Genetic drift acts randomly on allele frequencies without regard to reproductive fitness or adaptive advantage.
3
Evaluate option claims against modern evolutionary genetics
The founder effect reduces overall genetic diversity because only a portion of the original population's alleles are represented in the new colony.
Natural selection, direct environmental mutation induction, and gene flow fail to explain an allele frequency shift caused by random sampling during reproductive isolation.

Key Concept

Genetic drift and the Founder effect in Modern Evolutionary Theory
Question 3Question →

Arrange the following steps in the correct chronological sequence to illustrate how modern evolutionary theory (Neo-Darwinism) explains a change in allele frequency within a population.

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Answer

The correct chronological sequence begins with a random germline mutation introducing a new allele, followed by phenotypic expression of a beneficial trait, differential reproductive success of favored individuals, and finally an increase in allele frequency in the population's gene pool.
Modern evolutionary theory specifies that random gene mutations generate novel alleles, which express phenotypic traits. Environmental selective pressures favor individuals bearing advantageous phenotypes, leading to higher reproductive success. Consequently, the frequency of those advantageous alleles increases in the population's gene pool over time.

Step-by-Step Solution

1
Identify the origin of new genetic variation in population genetics.
Random gene mutation in germline cells creates a new allele.
According to the modern synthesis, mutation is the ultimate primary source of novel genetic variation.
2
Determine how the new allele manifests in the organism.
The novel allele is expressed phenotypically and provides an adaptive advantage.
Natural selection operates on phenotypic variations produced by underlying genotypes.
3
Analyze the impact of the adaptive trait on reproduction.
Organisms with the trait survive better and leave more offspring (differential reproduction).
Advantageous traits improve fitness, enabling higher reproductive output.
4
Trace the population-level genetic outcome over generations.
The beneficial allele's frequency rises in the gene pool across generations.
Evolution at the microevolutionary scale is defined as a change in population allele frequencies over time.

Key Concept

Neo-Darwinian Mechanism of Evolution
Question 4Question →

In modern evolutionary biology (Neo-Darwinism), microevolutionary divergence occurs through a specific sequence of genetic and environmental processes within populations. What is the correct chronological sequence of steps by which genetic drift and natural selection cause evolutionary change in a newly isolated population?

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Answer

The correct chronological sequence begins with geographic isolation and the founder effect, followed by the generation of novel alleles through mutation, random allele shifts via genetic drift, differential reproduction driven by natural selection, and culminates in genetic divergence and reproductive isolation.
The correct order follows the Neo-Darwinian framework: geographic separation creates an isolated gene pool via the founder effect; random gene mutations introduce new alleles; genetic drift alters allele frequencies in the small population; natural selection acts on phenotypic variations to favor adaptive traits; and long-term accumulation of these changes produces complete genetic divergence and reproductive isolation.

Step-by-Step Solution

1
Identify the initial event that separates gene pools.
Geographic isolation creates a small founder population with a distinct gene pool.
Before divergence can begin, gene flow with the parent population must be cut off.
2
Determine the origin of new genetic traits.
Random mutations introduce novel alleles into the small isolated gene pool.
Mutation is the ultimate raw source of new genetic variation in modern evolutionary theory.
3
Evaluate early sampling effects in small populations.
Genetic drift causes random shifts in allele frequencies across generations.
Small population size makes the gene pool highly susceptible to random sampling error.
4
Apply environmental filter mechanism.
Natural selection increases the frequency of alleles conferring adaptive advantage.
Environmental selective pressures favor individuals with higher fitness in the local environment.
5
Identify the ultimate evolutionary outcome.
Accumulated genetic differences lead to speciation and reproductive isolation.
Over extensive time periods, accumulated microevolutionary changes prevent interbreeding with the ancestral population.

Key Concept

Modern Evolutionary Theory (Neo-Darwinism) and Mechanisms of Microevolution
Estimated Time:2m 0s
Question 5Question →

According to modern evolutionary theory (Neo-Darwinism), which mechanism serves as the ultimate source of new genetic variations upon which natural selection acts?

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Answer: Gene mutations that alter DNA sequences

Answer

Gene mutations that alter DNA sequences serve as the ultimate source of new genetic variations in Neo-Darwinism.
Modern evolutionary theory (Neo-Darwinism) establishes that random gene mutations (along with genetic recombination) generate new alleles. Natural selection then acts upon this heritable genetic variation.

Step-by-Step Solution

1
Identify the primary source of genetic variation in population genetics.
Gene mutations create brand-new alleles within the gene pool.
Modern evolutionary theory unites Darwinian natural selection with Mendelian genetics, establishing that mutations produce genetic novelty.
2
Distinguish heritable genetic changes from non-heritable modifications.
Only changes in germline DNA (gene mutations) are inherited by subsequent generations.
Acquired somatic traits or environmental phenotypic shifts do not alter germ cells.

Key Concept

Gene Mutation as the Source of Evolutionary Variation
Question 6Question →

In a large, isolated population of a plant species, a catastrophic flood randomly eliminates over 95%95\% of the individuals regardless of their phenotypic traits. The few surviving individuals repopulate the area, resulting in allele frequencies in the restored population that differ significantly from those of the original gene pool. According to modern evolutionary theory (Neo-Darwinism), which mechanism is primarily responsible for this shift in allele frequencies?

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Answer: Genetic drift via the bottleneck effect, where random sampling changes allele frequencies in small surviving populations.

Answer

Genetic drift via the bottleneck effect, where random sampling changes allele frequencies in small surviving populations.
The correct answer correctly identifies genetic drift through the bottleneck effect. When a population undergoes an unselective, catastrophic reduction in size, the small surviving subgroup represents an arbitrary random sample of the original gene pool. As this subgroup reproduces, the resulting allele frequencies differ randomly from the original population, which is a classic demonstration of genetic drift in modern evolutionary biology.

Step-by-Step Solution

1
Analyze the nature of the environmental event described in the stem.
The catastrophe affects individuals randomly without regard to their fitness or phenotypic traits.
This excludes natural selection, which requires differential reproductive success based on adaptive traits.
2
Evaluate the evolutionary impact of drastic population reduction.
A severe reduction in population size leaves a small sample of alleles (a genetic bottleneck).
In small populations, chance events cause substantial random fluctuations in allele frequencies independent of selective advantage.
3
Identify the modern evolutionary mechanism that corresponds to random sampling shifts in small populations.
Genetic drift operating through a population bottleneck.
Neo-Darwinism defines genetic drift as stochastic changes in gene frequency, particularly pronounced following bottleneck events.

Key Concept

Genetic Drift and Bottleneck Effect in Modern Evolutionary Synthesis
Question 7Question →

Arrange the following biological events in the correct chronological sequence to illustrate how a beneficial trait spreads in a population according to modern evolutionary theory.

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Answer

The correct evolutionary sequence begins with a spontaneous gene mutation introducing a new allele, followed by natural selection favoring individuals with the advantageous trait, leading to differential transmission of the allele to offspring, and culminating in a shift in the population's overall allele frequency.
The correct sequence starts with the generation of novel genetic variation via random mutation. Natural selection then acts on this variation by favoring organisms with the advantageous phenotype. These individuals reproduce more successfully, transmitting the allele to their progeny. Over generations, this differential reproduction alters the overall allele frequency of the population's gene pool.

Step-by-Step Solution

1
Identify the origin of new genetic variation.
A random DNA mutation creates a novel allele in the gene pool.
Modern evolutionary theory establishes gene mutation as the primary source of novel genetic material.
2
Apply natural selection to the individual phenotypic trait.
Individuals possessing the beneficial allele demonstrate greater fitness.
Advantageous variations increase an organism's chances of surviving and reproducing.
3
Trace the inheritance of the trait into the next generation.
The favorable allele is passed to a greater proportion of offspring.
Differential reproduction naturally increases the representation of fit alleles in subsequent generations.
4
Determine the population-level genetic outcome.
The overall allele frequency in the gene pool changes over time.
Evolution in modern synthesis is measured by shifts in gene pool allele frequencies across generations.

Key Concept

Sequential mechanism of microevolution through mutation and natural selection
Estimated Time:45s
Question 8Question →

Match each evolutionary concept in modern evolutionary theory (Neo-Darwinism) to its corresponding genetic description or effect.

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Items

Gene mutation
Natural selection
Gene pool
Genetic drift

Matches

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Answer

Gene mutation matches with being the primary source of new genetic variations; Natural selection matches with driving non-random differential reproductive success; Gene pool matches with comprising the total sum of all genes and alleles; Genetic drift matches with causing random changes in allele frequencies in small populations.
In modern evolutionary theory (Neo-Darwinism), gene mutations supply new genetic variation; natural selection non-randomly increases adaptive allele frequencies; the gene pool represents all existing population alleles; and genetic drift causes random frequency changes, especially in small isolated groups.

Step-by-Step Solution

1
Identify the origin of new genetic diversity.
Gene mutation is recognized as the ultimate source of novel alleles.
Mutations introduce new genetic changes into the DNA of organisms.
2
Identify the mechanism that acts selectively on beneficial phenotypes.
Natural selection leads to differential reproductive success based on fitness.
Organisms best adapted to their environment pass on advantageous traits to offspring.
3
Define the collective genetic material of a population.
The gene pool consists of all alleles present across all individuals in the population.
Evolution in modern synthesis is defined as changes in allele frequencies within this gene pool.
4
Identify the mechanism of random, chance-based genetic frequency changes.
Genetic drift produces random fluctuations in allele frequencies, most notably in small populations.
Chance events rather than environmental adaptation govern genetic drift.

Key Concept

Mechanisms of Modern Evolutionary Synthesis and Population Genetics
Question 9Question →

According to modern evolutionary theory, which statement correctly describes the primary contribution of sexual reproduction to genetic variation within a population?

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Answer: It reshuffles existing alleles into unique combinations through crossing over and independent assortment.

Answer

Sexual reproduction reshuffles existing alleles into unique combinations through crossing over and independent assortment.
In modern evolutionary theory (Neo-Darwinism), sexual reproduction contributes to genetic diversity mainly by shuffling existing alleles during meiosis (crossing over and independent assortment) and random fertilization. This creates new genotypic combinations without generating brand-new genetic alleles.

Step-by-Step Solution

1
Distinguish between sources of new alleles and sources of genetic recombination.
Gene mutations are the ultimate source of novel alleles, whereas sexual reproduction rearranges existing alleles.
Modern synthesis clearly separates mutation (creation of new genetic material) from recombination (shuffling of existing alleles).
2
Identify the key mechanisms of genetic variation during sexual reproduction.
Processes such as crossing over during meiosis, independent assortment of chromosomes, and random fertilization generate new genotype combinations.
These mechanisms create unique offspring phenotypes without altering the fundamental genetic code of individual alleles.

Key Concept

Role of Sexual Reproduction and Recombination in Modern Evolutionary Theory
Question 10Question →

Match each microevolutionary genetic phenomenon on the left with its corresponding population genetics mechanism or outcome on the right.

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Items

Persistent retention of a deleterious or lethal recessive allele in a gene pool despite strong negative selection against homozygotes
Stochastic shifts in allele frequencies resulting from a severe, non-selective reduction in population size
Bimodal distribution of phenotypic traits caused by simultaneous selection against intermediate heterozygous or median phenotypes
Alteration of allele frequencies and reduction of genetic divergence between sub-populations caused by inter-population movement of fertile individuals

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Answer

The phenomenon of retaining a deleterious recessive allele corresponds to balancing selection via heterozygote advantage. Stochastic allele frequency shifts after population reduction correspond to genetic drift via the bottleneck effect. Bimodal distribution of traits corresponds to disruptive selection. The movement of individuals reducing divergence between populations corresponds to gene flow via migration.
The retention of deleterious alleles occurs through balancing selection because heterozygous carriers gain a survival advantage (e.g., malaria resistance in sickle-cell heterozygotes). Sudden random allele changes following a drastic population drop constitute genetic drift operating through the bottleneck effect. Selection favoring both extreme phenotypes while penalizing intermediate forms defines disruptive selection. The exchange of genetic material between distinct populations through migration defines gene flow.

Step-by-Step Solution

1
Analyze the retention of lethal recessive alleles in a population.
Identify that when heterozygous individuals possess higher fitness than either homozygous form, the recessive allele is preserved in the population (balancing selection / heterozygote superiority).
This explains why negative selection against homozygotes fails to eliminate harmful recessive alleles.
2
Examine random frequency changes due to catastrophic size reduction.
Map non-selective population drop to sampling error and random allele loss/fixation known as genetic drift (bottleneck effect).
When population size drops precipitously, survival is stochastic rather than fitness-based.
3
Evaluate the mechanism generating a bimodal phenotypic distribution.
Pair selective pressure against intermediate phenotypes with disruptive selection.
Disruptive selection acts against average phenotypes, favoring both extreme tail traits.
4
Determine the effect of inter-population movement of individuals.
Connect movement of gametes or breeding individuals between populations to gene flow.
Gene flow introduces new alleles and homogenizes gene pools across geographic regions.

Key Concept

Mechanisms of Microevolution and Population Genetics
Estimated Time:2m 0s
Question 11Question →

Match each microevolutionary mechanism of modern evolutionary theory on the left with its precise effect on population genetics on the right.

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Items

Genetic drift in small isolated populations
Natural selection acting on phenotypic variation
Gene flow between distinct populations
Germline DNA sequence mutation

Matches

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Answer

Genetic drift in small isolated populations matches stochastic non-adaptive fluctuations in allele frequencies; Natural selection acting on phenotypic variation matches systematically increasing the frequency of alleles conferring higher relative fitness; Gene flow between distinct populations matches increasing internal genetic diversity while reducing divergence between populations; Germline DNA sequence mutation matches serving as the ultimate source of brand-new alleles.
In Neo-Darwinian synthesis, microevolutionary changes are driven by distinct genetic mechanisms: germline mutations supply raw genetic material by producing new alleles; genetic drift alters allele frequencies by chance in small populations; natural selection systematically promotes alleles conferring relative fitness; and gene flow exchanges genetic alleles across population boundaries.

Step-by-Step Solution

1
Analyze the impact of small population size on allele sampling.
Identify that small sample sizes produce random, non-adaptive sampling errors.
Genetic drift alters gene pools purely through chance events rather than survival advantage.
2
Evaluate how differential reproductive success affects gene frequencies.
Connect natural selection to directional, adaptive shifts in allele frequencies.
Organisms bearing beneficial phenotypic traits leave more offspring, systematically propagating their alleles.
3
Determine the population genetic consequences of allele movement between populations.
Match gene flow to homogenization between populations and increased variation within the receiving population.
Immigration introduces novel alleles into the recipient gene pool while reducing genetic distance between source and sink groups.
4
Identify the primary origin of completely new genetic alleles.
Match germline mutation to the creation of novel genetic material.
Recombination reshuffles existing alleles, whereas mutation is the sole mechanism capable of generating new molecular alleles.

Key Concept

Microevolutionary Mechanisms and Population Genetics
Estimated Time:2m 0s
Question 12Question →

A population of crop-damaging insects was repeatedly sprayed with a synthetic chemical insecticide over several years. Initially, the chemical killed almost all insects, but after consecutive generations, the population became predominantly resistant to the chemical. According to modern evolutionary theory, which of the following best explains how this resistance developed within the gene pool?

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Answer: Pre-existing random gene mutations provided resistance in a few individuals, and natural selection increased the frequency of these resistant alleles over generations.

Answer

Pre-existing random gene mutations provided resistance in a few individuals, and natural selection increased the frequency of these resistant alleles over generations.
According to modern evolutionary theory, random gene mutations introduce variation into a gene pool independently of environmental needs. When an environmental stressor such as an insecticide is introduced, it acts as a selective pressure. Individuals already possessing the resistant allele survive and reproduce, passing the genetic trait to their offspring. Over generations, the frequency of the resistant allele increases within the population.

Step-by-Step Solution

1
Identify the source of variation in modern evolutionary theory (Neo-Darwinism).
Gene mutations occur randomly in the gene pool before any environmental change occurs.
Evolutionary changes rely on pre-existing genetic variation in germ cells rather than post-exposure adaptations.
2
Analyze the role of the environmental factor (the insecticide).
The insecticide acts as a selective agent, eliminating susceptible individuals while resistant individuals survive.
Natural selection shifts allele frequencies in favor of advantageous traits already present.
3
Evaluate population gene pool shifts across generations.
Surviving resistant individuals reproduce and pass resistant alleles to offspring, increasing the allele frequency.
Differential reproductive success leads to microevolutionary change in the population.

Key Concept

Modern Evolutionary Theory (Neo-Darwinism) and Natural Selection on Genetic Variation
Question 13Question →

In modern evolutionary theory (Neo-Darwinism), natural selection operates on genetic variation within a population in distinct ways depending on selective pressures. Match each mode of natural selection on the left with its corresponding effect on phenotypic distribution and allele frequencies on the right.

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Items

Stabilizing selection
Directional selection
Disruptive selection
Balancing selection

Matches

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Answer

Stabilizing selection matches selecting against extremes to narrow genetic variance; Directional selection matches shifting allele frequencies toward one phenotypic extreme; Disruptive selection matches favoring extreme phenotypes over intermediate forms; Balancing selection matches preserving multiple alleles in a gene pool due to heterozygote advantage.
Stabilizing selection lowers variance by favoring intermediate phenotypes; directional selection pushes trait means toward one extreme; disruptive selection favors both phenotypic extremes causing a bimodal distribution; balancing selection retains genetic variation through mechanisms like heterozygote superiority.

Step-by-Step Solution

1
Analyze how stabilizing selection alters phenotypic variance in population genetics.
Establish that stabilizing selection eliminates extreme phenotypes and maintains the average phenotype, thereby narrowing variation around the mean.
In unchanging environments, intermediate phenotypes yield optimal fitness.
2
Analyze the population genetic outcome of directional selection.
Establish that persistent selection for a specific extreme phenotype shifts the allele frequencies in the direction of that adaptive trait.
Environmental shifts create selective pressure favoring one phenotypic tail.
3
Analyze the impact of disruptive selection on population structure.
Establish that selection against the intermediate form favors both phenotypic extremes, splitting the trait distribution into two distinct peaks.
Heterogeneous environments or varied resource partitioning can favor extreme adaptations.
4
Analyze how balancing selection maintains gene pool diversity.
Establish that mechanisms like overdominance (heterozygote advantage) actively retain alternative alleles rather than driving any single allele to fixation.
Heterozygotes possessing higher selective value preserve both alleles in equilibrium.

Key Concept

Modes of Natural Selection in Population Genetics
Question 14Question →

A large, randomly mating population of beetles exists in a stable environment where no genetic mutation, gene flow through migration, or natural selection takes place. According to modern evolutionary theory, what will happen to the allele frequencies within the gene pool of this population over successive generations?

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Answer: The allele and genotype frequencies in the population will remain constant from generation to generation.

Answer

The allele and genotype frequencies in the population will remain constant from generation to generation.
According to modern evolutionary theory and population genetics (Hardy-Weinberg principle), a large, randomly mating population free from evolutionary forces such as natural selection, gene flow, genetic drift, and mutation will maintain constant allele and genotype frequencies across generations, resulting in genetic equilibrium.

Step-by-Step Solution

1
Analyze the conditions given in the population scenario
The population is large, randomly mating, and experiences no mutation, migration, or natural selection.
These conditions meet the prerequisites for genetic equilibrium under modern synthesis and population genetics.
2
Apply the Hardy-Weinberg principle of modern evolutionary theory
When evolutionary forces are absent, allele and genotype frequencies do not change over generations.
Microevolution is defined as a shift in gene pool allele frequencies over time; without evolutionary drivers, the gene pool remains stable.

Key Concept

Hardy-Weinberg Equilibrium and Gene Pool Dynamics
Estimated Time:1m 0s
Question 15Question →

In a wild rodent population inhabiting a grassland region, individuals display variation in coat color ranging from light beige to dark brown due to multiple alleles. Following dark soot deposition across the habitat from nearby industrial activity, light-colored rodents become significantly more vulnerable to visual predators. According to modern evolutionary theory (Neo-Darwinism), which mechanism explains the resulting change in coat color distribution over successive generations?

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Answer: Differential survival and reproduction of individuals carrying pre-existing dark coat alleles, resulting in an increased frequency of dark alleles in the gene pool.

Answer

Natural selection acting on pre-existing genetic variation, leading to an increased frequency of advantageous alleles in the gene pool over generations.
Under modern evolutionary theory (Neo-Darwinism), natural selection acts upon pre-existing genetic variations in the population. Rodents carrying alleles for darker coats possess a selective advantage due to improved camouflage against soot-covered substrate, allowing them to survive, reproduce, and pass those beneficial alleles to the next generation, thereby increasing the dark allele frequency in the gene pool.

Step-by-Step Solution

1
Identify the source of variation according to modern evolutionary theory.
Genetic variation (such as coat color alleles) exists prior to environmental change due to random mutations and genetic recombination.
Neo-Darwinism establishes that evolution relies on germline genetic mutations, not environmentally directed somatic adaptations.
2
Analyze the effect of the environmental change (soot deposition) on differential survival.
Dark-colored rodents have higher camouflage, resulting in higher survival rates and reproductive output compared to light-colored rodents.
Natural selection favors phenotypes that provide selective advantages under specific environmental pressures.
3
Determine the population genetics outcome across generations.
Dark coat alleles are transmitted to offspring at higher rates, causing dark coat allele frequency in the gene pool to rise.
Microevolution is defined in modern evolutionary theory as a change in allele frequencies within a population gene pool over time.

Key Concept

Neo-Darwinian Natural Selection and Gene Pool Allele Frequencies
Question 16Question →

In a plant population growing in soil contaminated with heavy metals, a rare pre-existing gene mutation enables certain individuals to tolerate high toxicity. According to the modern synthetic theory of evolution, how does this trait become predominant in subsequent generations?

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Answer: Natural selection acts on the genetic variation, increasing the frequency of the favorable allele in the gene pool over time.

Answer

Natural selection acts on the genetic variation, increasing the frequency of the favorable allele in the gene pool over time.
According to modern evolutionary theory (Neo-Darwinism), natural selection operates on pre-existing genetic variation produced by mutations. Individuals possessing the favorable allele survive heavy metal toxicity and reproduce more successfully, resulting in an increased allele frequency within the population's gene pool over time.

Step-by-Step Solution

1
Identify the source of variation in the population according to Neo-Darwinism.
The pre-existing gene mutation provides random, heritable genetic variation within the gene pool.
Modern evolutionary theory establishes gene mutation and recombination as the primary sources of genetic variation.
2
Evaluate the mechanism of evolutionary change acting on this variation.
Individuals carrying the resistant mutant allele have a higher survival and reproductive success rate in the presence of heavy metal stress.
Differential reproductive success (natural selection) favors advantageous phenotypes.
3
Determine the long-term impact on population genetics.
The frequency of the mutant allele increases in the gene pool over successive generations.
Evolution in the modern synthesis is defined as a change in allele frequencies within a population over time.

Key Concept

Modern Evolutionary Theory (Neo-Darwinism) and Population Genetics
Question 17Question →

In modern evolutionary theory (Neo-Darwinism), specific mechanisms alter allele frequencies and genetic variation within population gene pools. Match each evolutionary mechanism on the left with its corresponding impact on population genetics on the right.

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Items

Genetic Drift (Bottleneck Effect)
Gene Flow
Stabilizing Selection
Directional Selection

Matches

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Answer

Genetic Drift (Bottleneck Effect) pairs with random allele shifts following severe population crashes; Gene Flow pairs with allele exchange between migrating populations; Stabilizing Selection pairs with favoring intermediate traits over extremes; Directional Selection pairs with shifting population traits toward one extreme.
Each microevolutionary mechanism has a distinct outcome: the bottleneck effect causes random loss of alleles during population crashes; gene flow introduces or homogenizes genetic variation between populations through migration; stabilizing selection preserves the average phenotype; and directional selection drives allele frequencies toward a specific phenotypic extreme.

Step-by-Step Solution

1
Identify the mechanism operating through random population reductions.
Genetic Drift (Bottleneck Effect) corresponds to random shifts after catastrophic population size decline.
Populations recovering from severe crashes experience random sampling loss of alleles.
2
Identify the movement of genetic material across population boundaries.
Gene Flow matches the transfer of alleles via migration.
Immigration and emigration carry alleles between isolated gene pools.
3
Distinguish between modes of natural selection based on phenotypic outcomes.
Stabilizing selection favors intermediate forms, whereas directional selection favors one extreme trait.
Stabilizing reduces phenotypic variance, while directional shifts the mean phenotype toward an extreme allele.

Key Concept

Mechanisms of Microevolution and Neo-Darwinian Genetics
Modern Evolutionary Theory and Genetic Basis of Evolution Practice Questions — JAMB UTME | Examkin