Natural Selection Effects - Middle School Life Science
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What is natural selection?
What is natural selection?
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Differential survival and reproduction based on heritable traits. Organisms with favorable traits survive and reproduce more.
Differential survival and reproduction based on heritable traits. Organisms with favorable traits survive and reproduce more.
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What condition must be true for natural selection to change trait frequencies?
What condition must be true for natural selection to change trait frequencies?
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Trait variation must be heritable and affect fitness. Only heritable traits that impact survival/reproduction can evolve.
Trait variation must be heritable and affect fitness. Only heritable traits that impact survival/reproduction can evolve.
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What does fitness mean in natural selection?
What does fitness mean in natural selection?
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Relative reproductive success in a specific environment. Measures how well an organism reproduces compared to others.
Relative reproductive success in a specific environment. Measures how well an organism reproduces compared to others.
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What is the difference between genotype and phenotype?
What is the difference between genotype and phenotype?
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Genotype is genetic makeup; phenotype is observable traits. Genes determine genotype; their expression creates phenotype.
Genotype is genetic makeup; phenotype is observable traits. Genes determine genotype; their expression creates phenotype.
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What is directional selection?
What is directional selection?
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Selection that favors one extreme, shifting the average trait value. Pushes population toward one extreme trait value.
Selection that favors one extreme, shifting the average trait value. Pushes population toward one extreme trait value.
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What is stabilizing selection?
What is stabilizing selection?
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Selection that favors intermediate traits, reducing variation. Eliminates extremes, maintaining average trait values.
Selection that favors intermediate traits, reducing variation. Eliminates extremes, maintaining average trait values.
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What is disruptive selection?
What is disruptive selection?
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Selection that favors both extremes, increasing variation. Eliminates intermediate values, creating two distinct groups.
Selection that favors both extremes, increasing variation. Eliminates intermediate values, creating two distinct groups.
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Which evidence best supports natural selection: individuals change or populations change?
Which evidence best supports natural selection: individuals change or populations change?
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Populations change in trait frequencies over generations. Evolution occurs at population level, not individual level.
Populations change in trait frequencies over generations. Evolution occurs at population level, not individual level.
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Identify the best conclusion: A heritable trait increases from $20%$ to $60%$ after drought.
Identify the best conclusion: A heritable trait increases from $20%$ to $60%$ after drought.
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The trait likely increased fitness under drought conditions. Large frequency increase suggests strong selective advantage.
The trait likely increased fitness under drought conditions. Large frequency increase suggests strong selective advantage.
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Which option is the strongest evidence that a trait is heritable: similarity to parents or to habitat?
Which option is the strongest evidence that a trait is heritable: similarity to parents or to habitat?
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Similarity to parents (offspring resemble parents for the trait). Parent-offspring resemblance indicates genetic inheritance.
Similarity to parents (offspring resemble parents for the trait). Parent-offspring resemblance indicates genetic inheritance.
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Identify the selection type: the darkest mice become most common on dark lava rock.
Identify the selection type: the darkest mice become most common on dark lava rock.
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Directional selection. One extreme (darkest) is favored over lighter colors.
Directional selection. One extreme (darkest) is favored over lighter colors.
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Identify the selection type: average beak size increases as only large seeds remain.
Identify the selection type: average beak size increases as only large seeds remain.
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Directional selection. Larger beaks are favored when only large seeds are available.
Directional selection. Larger beaks are favored when only large seeds are available.
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Identify the selection type: very small and very large individuals survive poorly; medium survives best.
Identify the selection type: very small and very large individuals survive poorly; medium survives best.
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Stabilizing selection. Medium size has highest fitness; extremes are selected against.
Stabilizing selection. Medium size has highest fitness; extremes are selected against.
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Identify the selection type: only very small and very large beaks succeed; medium beaks decline.
Identify the selection type: only very small and very large beaks succeed; medium beaks decline.
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Disruptive selection. Both extremes succeed while intermediate forms are selected against.
Disruptive selection. Both extremes succeed while intermediate forms are selected against.
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Which conclusion is supported: Trait A has $2\times$ higher offspring survival than Trait B for 5 generations.
Which conclusion is supported: Trait A has $2\times$ higher offspring survival than Trait B for 5 generations.
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Trait A frequency should increase over generations. Higher reproductive success leads to increased frequency over time.
Trait A frequency should increase over generations. Higher reproductive success leads to increased frequency over time.
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What is the main difference between natural selection and genetic drift?
What is the main difference between natural selection and genetic drift?
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Selection is nonrandom; drift changes frequencies by chance. Selection is fitness-based; drift is random sampling error.
Selection is nonrandom; drift changes frequencies by chance. Selection is fitness-based; drift is random sampling error.
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Identify the best conclusion: after a drought, deeper-beaked birds leave more offspring.
Identify the best conclusion: after a drought, deeper-beaked birds leave more offspring.
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Drought favored deeper beaks, so deep-beak frequency should rise. Environmental change created selection for the adaptive trait.
Drought favored deeper beaks, so deep-beak frequency should rise. Environmental change created selection for the adaptive trait.
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Which option is the best evidence for selection: A) random change B) trait linked to higher offspring number?
Which option is the best evidence for selection: A) random change B) trait linked to higher offspring number?
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B) Trait linked to higher offspring number. Reproductive advantage directly demonstrates natural selection.
B) Trait linked to higher offspring number. Reproductive advantage directly demonstrates natural selection.
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What is disruptive selection?
What is disruptive selection?
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Selection favors both extremes over the average phenotype. Can split a population into two distinct groups.
Selection favors both extremes over the average phenotype. Can split a population into two distinct groups.
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What is the difference between phenotype and genotype?
What is the difference between phenotype and genotype?
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Phenotype is expressed traits; genotype is genetic makeup. Phenotype is observable; genotype is the underlying DNA.
Phenotype is expressed traits; genotype is genetic makeup. Phenotype is observable; genotype is the underlying DNA.
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Identify the evidence-based conclusion: a trait increases from $20%$ to $60%$ in 10 generations.
Identify the evidence-based conclusion: a trait increases from $20%$ to $60%$ in 10 generations.
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The trait likely increased fitness under the current conditions. Large frequency increase suggests strong positive selection.
The trait likely increased fitness under the current conditions. Large frequency increase suggests strong positive selection.
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Which statement best explains why individuals do not evolve by natural selection?
Which statement best explains why individuals do not evolve by natural selection?
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Selection changes trait frequencies in populations, not individuals. Evolution acts on populations through differential reproduction.
Selection changes trait frequencies in populations, not individuals. Evolution acts on populations through differential reproduction.
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Identify the correct claim: natural selection acts on individuals or changes populations over generations?
Identify the correct claim: natural selection acts on individuals or changes populations over generations?
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It changes populations over generations. Selection acts on individuals but evolution occurs in populations.
It changes populations over generations. Selection acts on individuals but evolution occurs in populations.
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What is the difference between genotype and phenotype?
What is the difference between genotype and phenotype?
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Genotype is genetic makeup; phenotype is observable traits. Genotype determines phenotype through gene expression.
Genotype is genetic makeup; phenotype is observable traits. Genotype determines phenotype through gene expression.
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Identify the type of selection: in patchy habitat, light and dark mice survive; medium mice are seen.
Identify the type of selection: in patchy habitat, light and dark mice survive; medium mice are seen.
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Disruptive selection. Different habitats favor different camouflage colors.
Disruptive selection. Different habitats favor different camouflage colors.
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