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Darwin's Theory of Natural Selection

11 questions

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Question 1Question →

In a population of moths inhabiting an industrial region, dark-colored individuals became significantly more common over several generations as pollution darkened the tree trunks. According to Charles Darwin's theory of natural selection, which mechanism best accounts for this change in the population?

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Answer: Pre-existing dark genetic variations provided a camouflage advantage against predators, resulting in higher survival and reproduction rates for dark moths.

Answer

Pre-existing dark genetic variations provided a camouflage advantage against predators, resulting in higher survival and reproduction rates for dark moths.
According to Darwin's theory of natural selection, populations contain natural genetic variations. When the environment changed due to industrial pollution, dark moths gained a camouflage advantage. They were preyed upon less frequently by birds, allowing them to survive and pass their dark-pigment genes to the next generation at higher rates.

Step-by-Step Solution

1
Identify the foundation of Darwinian evolution.
Natural selection requires inherited genetic variation to already exist within a population prior to environmental change.
Organisms do not generate intentional phenotypic changes within their lifetime to suit new environments.
2
Analyze the environmental selective pressure.
Soot-covered trees made dark moths less visible to predators compared to light-colored moths.
Selective pressures determine which existing phenotypes offer a survival advantage.
3
Determine the population-level outcome.
Darker moths survived longer and produced more offspring, increasing the proportion of dark moths in future generations.
Differential survival and reproduction cause advantageous alleles to accumulate in the population over time.

Key Concept

Natural Selection and Differential Reproduction
Estimated Time:1m 0s
Question 2Question →

According to Charles Darwin's theory of natural selection, evolutionary changes occur in a specific logical sequence. Arrange the following processes in the correct chronological order in which natural selection acts upon a biological population.

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Answer

The correct logical sequence of natural selection is: Overproduction leading to competition, pre-existing inherited variation, differential survival and reproduction of favored individuals, followed by population adaptation across generations.
Natural selection begins when overproduction of offspring causes competition for limited resources. Pre-existing inherited variations determine which individuals survive environmental pressure. Favorable traits allow greater reproductive success, increasing the trait's frequency in future generations.

Step-by-Step Solution

1
Identify the initiating condition in Darwin's model.
Overproduction of offspring occurs, leading to environmental resource limitation and competition.
Populations naturally produce excess offspring, creating a struggle for existence.
2
Determine the substrate upon which selection acts.
Inherited variation must already exist within the population.
Without pre-existing phenotypic variation, differential survival cannot select for specific traits.
3
Analyze the interaction between variation and environmental pressure.
Individuals with traits favored by the environment survive and reproduce at higher rates.
Differential reproduction ensures favorable alleles are passed to the next generation.
4
Establish the long-term population outcome.
The frequency of advantageous traits increases in subsequent generations.
Evolution by natural selection is defined as a change in population characteristics over time.

Key Concept

Darwinian Mechanism of Evolutionary Change by Natural Selection
Question 3Question →

Match each core concept of Charles Darwin's theory of natural selection on the left with its corresponding description on the right.

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Items

Overproduction
Struggle for existence
Survival of the fittest
Inheritance of variation

Matches

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Answer

Overproduction matches with organisms producing more offspring than the environment can support; Struggle for existence matches with individuals competing for limited environmental resources; Survival of the fittest matches with organisms with advantageous traits being more likely to survive and reproduce; Inheritance of variation matches with favorable inherited traits being transmitted to subsequent generations.
Each core concept of natural selection directly aligns with a key evolutionary process: overproduction creates resource pressure; scarce resources lead to competition (struggle for existence); advantageous traits enable differential reproductive success (survival of the fittest); and passing those favorable traits to offspring alters population characteristics over time.

Step-by-Step Solution

1
Define overproduction within Darwin's theoretical framework.
Species have a natural tendency to produce more offspring than their habitat can sustain.
High reproductive potential creates population pressure against finite natural resources.
2
Identify the primary consequence of overproduction and limited resources.
Organisms must engage in a struggle for existence.
Scarcity of essential resources like food, light, and shelter leads to competition.
3
Relate individual differences to survival outcomes.
Organisms with advantageous variations undergo differential survival (survival of the fittest).
Traits that better adapt an individual to its environment increase its probability of surviving and reproducing.
4
Explain how natural selection affects future generations.
Advantageous variations are inherited by offspring.
Heritable favorable traits become increasingly common in subsequent generations.

Key Concept

Core Concepts and Principles of Natural Selection
Question 4Question →

A farmer repeatedly sprays a synthetic insecticide on a vegetable farm over several growing seasons. Initially, the chemical kills nearly all target pests, but after several years, the insecticide loses its effectiveness and pest populations surge. According to Darwin's theory of natural selection, which of the following statements best explains how resistance arose in this insect population?

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Answer: A small fraction of insects possessed pre-existing genetic variations for resistance, enabling them to survive the chemical, reproduce, and transmit the resistant genes to subsequent generations.

Answer

Pre-existing genetic variation allowed resistant individuals to survive, reproduce, and pass advantageous alleles to their offspring.
According to Charles Darwin's theory of natural selection, evolution operates on pre-existing genetic variations within a population. When an environmental selective pressure (such as an insecticide) is introduced, individuals already possessing alleles for resistance are more likely to survive and reproduce. Over successive generations, these advantageous alleles become more common, increasing overall resistance in the population.

Step-by-Step Solution

1
Identify the key mechanism of Darwinian natural selection
Natural selection relies on natural, pre-existing genetic variation present within a population prior to environmental change.
Environmental factors act as selective pressures rather than mutational triggers or causes of physiological adaptation during an individual's lifespan.
2
Apply selective pressure to the population
The insecticide acts as a selective agent, destroying susceptible individuals while resistant individuals survive (differential survival).
Survival is determined by inherited traits that confer a reproductive advantage under specific environmental conditions.
3
Trace the frequency of the advantageous trait across generations
Surviving resistant individuals reproduce, increasing the frequency of resistance alleles in future generations.
Over time, the population shifts towards a higher proportion of resistant individuals, resulting in microevolution.

Key Concept

Darwinian Natural Selection and Antibiotic/Pesticide Resistance
Question 5Question →

Match each core observation or premise of Charles Darwin's theory of natural selection on the left with its corresponding logical deduction or ecological outcome on the right.

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Items

Organisms produce far more offspring than the environment can support (Overproduction)
Natural populations exhibit heritable differences among individuals (Variation)
Environmental resources such as food, space, and mates remain limited

Matches

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Answer

The correct matches pair overproduction of offspring with the intense struggle for existence; heritable variation among individuals with differential survival and reproduction; and limited environmental resources with the maintenance of stable population numbers.
Matching overproduction with the struggle for existence reflects Darwin's observation that population growth outpaces resources. Matching heritable variation with differential survival correctly identifies how natural selection favors adapted individuals. Matching limited resources with stable population numbers accurately describes ecological population regulation.

Step-by-Step Solution

1
Connect the concept of overproduction to population competition.
Producing more offspring than the habitat can sustain creates severe competition.
High birth rates exceeding resource availability trigger a struggle for survival among offspring.
2
Relate heritable variations within a population to survival success.
Differences among individuals determine which organisms are better adapted to survive and pass on their traits.
Natural selection acts on pre-existing phenotypic variations to favor individuals with adaptive advantages.
3
Analyze how limited environmental resources affect population dynamics.
Restricted resources prevent unlimited population growth, leading to stable population numbers.
Carrying capacity limitations regulate and balance population size over generations.

Key Concept

Darwin's Premises and Deductions of Natural Selection
Question 6Question →

In a natural population of tortoises living on an island, individuals with longer necks can reach higher leaves on tall bushes during dry seasons, whereas short-necked tortoises struggle to find food. Over several generations, the proportion of long-necked tortoises in the population increases significantly. According to Charles Darwin's theory of natural selection, which of the following best explains this change?

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Answer: Tortoises with naturally longer necks had higher survival rates and produced more offspring, passing on their advantageous trait.

Answer

Tortoises with naturally longer necks had higher survival rates and produced more offspring, passing on their advantageous trait.
Darwin's theory of natural selection states that variations exist naturally within a population. When environmental conditions create competition for resources (such as food scarcity during dry seasons), individuals possessing favorable inherited traits (such as longer necks) are better adapted, survive longer, and reproduce more successfully. Over generations, these advantageous traits become more prevalent in the population.

Step-by-Step Solution

1
Identify the biological observation
Longer-necked tortoises survive dry seasons better because they can reach food.
This establishes differential survival based on a specific trait.
2
Apply Darwin's core principles of natural selection
Pre-existing variation → Environmental pressure (food scarcity) → Differential survival & reproduction → Trait becomes more common.
Darwin's theory relies on inherited variation and differential reproductive success.
3
Distinguish Darwinian mechanism from Lamarckian views
Avoid options suggesting acquired traits through stretching or goal-directed mutations.
Darwinian evolution does not involve inheritance of traits acquired during an organism's lifetime.

Key Concept

Differential Survival and Reproduction based on Inherited Variation
Question 7Question →

A population of bacteria exhibits variation in antibiotic resistance traits. Arrange the following events describing the evolutionary process of antibiotic resistance according to Darwin's theory of natural selection in the correct chronological sequence, from first to last.

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Answer

The correct chronological sequence is: 1) Pre-existing variation in resistance traits, 2) Overproduction leading to competition, 3) Antibiotic selection causing differential survival, 4) Inheritance of resistance traits through reproduction, 5) Shift in population trait frequency.
Darwin's theory of natural selection operates through a strict logical progression. First, pre-existing variations arise spontaneously in the population. Second, overproduction of offspring leads to competition for limited resources. Third, an environmental selective agent (such as an antibiotic) causes differential survival, favoring individuals with advantageous traits. Fourth, survivors reproduce and transmit these traits to their offspring. Finally, over multiple generations, the trait frequency shifts, resulting in population adaptation.

Step-by-Step Solution

1
Identify the initial genetic state of the population.
Random genetic variations exist prior to environmental selection.
Darwinian natural selection requires pre-existing variation upon which selection acts.
2
Analyze the impact of reproductive capacity.
Overproduction of offspring creates a struggle for existence.
Organisms produce more offspring than available environmental resources can support.
3
Apply the environmental selective pressure.
Exposure to the antibiotic results in differential survival.
Selective pressure eliminates susceptible organisms while favoring individuals with adapted variations.
4
Trace the transmission of advantageous traits.
Surviving resistant bacteria reproduce and pass beneficial traits to their progeny.
Differential reproduction ensures that favorable inherited traits increase in frequency.
5
Evaluate the evolutionary outcome at the population level.
The entire bacterial population becomes predominantly resistant over generations.
Evolution is defined as a cumulative change in allele/trait frequencies in a population over time.

Key Concept

Darwin's Theory of Natural Selection (Logical Sequence)
Question 8Question →

A population of wild grass growing near an abandoned copper mine displays variation in copper tolerance. Over several generations, the proportion of copper-tolerant grass plants increased significantly in the contaminated soil surrounding the mine. According to Charles Darwin's theory of natural selection, which of the following best explains how this population evolved?

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Answer: Plants with pre-existing variation for copper tolerance survived and reproduced more successfully in the contaminated soil, passing the beneficial trait to their offspring.

Answer

Plants with pre-existing variation for copper tolerance survived and reproduced more successfully in the contaminated soil, passing the beneficial trait to their offspring.
According to Darwin's theory of natural selection, populations contain pre-existing variations. When an environmental challenge (such as copper toxicity in the soil) arises, individuals possessing traits that confer resistance are more likely to survive and reproduce. Over successive generations, differential survival and reproduction increase the proportion of advantageous traits within the population.

Step-by-Step Solution

1
Identify the core mechanism of Darwin's theory of natural selection.
Natural selection acts on existing phenotypic/genetic variation within a population subject to environmental pressure.
Environmental factors select for traits that grant differential survival and reproductive advantage.
2
Analyze the scenario of grass plants near the copper mine.
The contaminated soil acts as a selective agent favoring copper-tolerant individuals over non-tolerant ones.
Tolerant plants survive to reproduce, increasing the frequency of the tolerance trait in subsequent generations.
3
Differentiate Darwinian selection from Lamarckian acquired traits and teleological misconceptions.
Individual organisms do not acquire inherited adaptations during their lifetime, nor do environments induce directional targeted mutations.
Darwinian evolution requires natural selection acting on pre-existing inherited variations.

Key Concept

Darwin's Theory of Natural Selection
Question 9Question →

Match each biological observation of Charles Darwin's theory of natural selection on the left with its corresponding ecological or evolutionary outcome on the right.

Click a left item, then click its matching right item

Items

High reproductive potential of species (Overproduction)
Constancy of environmental resources and carrying capacity
Inherited phenotypic variation among individuals
Differential survival and reproductive success

Matches

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Answer

High reproductive potential matches with preventing unchecked exponential population growth; Constancy of environmental resources matches with inducing an intense struggle for existence; Inherited phenotypic variation matches with providing the essential raw material upon which natural selection operates; Differential survival and reproductive success matches with gradually increasing the proportion of favorable adaptive traits.
High reproductive potential paired with limited resources keeps population sizes stable by causing a struggle for existence. Inherited phenotypic variation acts as the raw material for selection, and differential survival ensures that beneficial adaptations increase in frequency over generations.

Step-by-Step Solution

1
Analyze the concept of overproduction of offspring in natural populations.
Overproduction combined with environmental limits restricts population sizes.
Darwin noted that living organisms produce far more gametes and offspring than ever reach reproductive maturity.
2
Relate resource availability to population competition.
Limited food, space, and mates create a continuous struggle for existence.
Since carrying capacity is finite, individuals must compete for essential resources to survive.
3
Identify the role of pre-existing variations within a species.
Phenotypic variations serve as the substrate sorted by environmental pressures.
Without inherited differences between organisms, selection cannot favor specific traits over others.
4
Determine the long-term population outcome of natural selection.
Adaptive traits become more common in successive generations.
Organisms bearing advantageous traits leave more surviving offspring, shifting the population's genetic and phenotypic profile.

Key Concept

Darwinian Principles of Natural Selection
Question 10Question →

A population of desert pocket mice primarily displays light coat coloration. Following a volcanic eruption, dark basalt rock is exposed in their habitat, creating a new environment. Arrange the following steps describing the evolutionary adaptation of dark fur in this population according to Charles Darwin's theory of natural selection in their correct sequence, from first to last.

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Answer

The correct sequence of events is: (1) Random genetic variation introduces dark fur traits -> (2) Volcanic basalt rock establishes selective pressure from visual predators -> (3) Dark-furred mice experience higher survival and reproduction rates -> (4) The frequency of dark-furred mice increases in the population over generations.
Darwin's theory of natural selection follows a strict logical sequence: heritable variation arises randomly first, an environmental change creates selective pressure, individuals with advantageous variation experience differential survival and reproduction, and finally, the population undergoes evolutionary change as the advantageous trait becomes predominant.

Step-by-Step Solution

1
Identify the initial source of variation
Random mutations produce pre-existing variation (dark fur) within the light-furred population.
Natural selection can only act upon traits that already exist in a population's gene pool.
2
Identify the selective pressure
The exposure of dark basalt rock creates selective pressure via visual predation by owls and hawks.
Selective pressures determine which pre-existing variations offer a survival advantage.
3
Determine differential reproduction
Dark mice are camouflaged and thus survive predation at higher rates, producing more offspring.
Individuals with favorable adaptations contribute more offspring to the next generation.
4
Evaluate long-term population change
The frequency of the dark fur phenotype increases in the population across generations.
Evolution by natural selection is a change in allele frequencies within a population over time.

Key Concept

Logical progression of Darwinian natural selection (Variation -> Selective Pressure -> Differential Survival/Reproduction -> Population Adaptation)
Estimated Time:1m 30s
Question 11Question →

During a prolonged drought on an isolated island, small soft seeds became scarce, while large hard-shelled seeds remained abundant. Researchers observed that birds with deeper, stronger beaks survived and reproduced at higher rates than those with shallower beaks. Over subsequent generations, the average beak depth in the population increased. According to Charles Darwin's theory of natural selection, which mechanism best accounts for this evolutionary change?

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Answer: Natural selection acted on pre-existing variation in beak depth, favoring individuals with advantageous traits to reproduce.

Answer

Natural selection acted on pre-existing variation in beak depth, favoring individuals with advantageous traits to reproduce.
According to Darwin's theory of natural selection, populations possess pre-existing variation. When environmental conditions change (such as a drought reducing soft seeds), individuals possessing advantageous variations (deeper beaks suitable for hard seeds) exhibit higher survival and reproductive rates. Consequently, the advantageous trait becomes more prevalent in subsequent generations.

Step-by-Step Solution

1
Identify the initial population condition in the scenario.
The initial population already contained variation in beak depth (some birds had shallow beaks, others deeper beaks).
Darwinian natural selection requires pre-existing heritable variation in the population before selective pressure is applied.
2
Analyze the environmental change and selective pressure.
Drought changed the food availability to predominantly large, hard seeds, creating a survival challenge.
Environmental factors act as selective forces that determine which phenotypes have higher fitness.
3
Evaluate the differential survival and reproduction.
Birds with deeper beaks survived and reproduced more effectively, passing the alleles for deeper beaks to the next generation.
Differential reproduction leads to an shift in allele frequencies across generations toward the favorable trait.

Key Concept

Natural Selection via Differential Survival and Pre-existing Variation
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