Middle School Life Science Flashcards: Natural Selection Effects

What this deck covers

This deck focuses on Natural Selection Effects, giving you a quick way to review the definitions, rules, and examples that matter most for Middle School Life Science.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is natural selection?

Answer: Differential survival and reproduction based on heritable traits. Organisms with favorable traits survive and reproduce more.

Flashcard 2: What condition must be true for natural selection to change trait frequencies?

Answer: Trait variation must be heritable and affect fitness. Only heritable traits that impact survival/reproduction can evolve.

Flashcard 3: What does fitness mean in natural selection?

Answer: Relative reproductive success in a specific environment. Measures how well an organism reproduces compared to others.

Flashcard 4: What is the difference between genotype and phenotype?

Answer: Genotype is genetic makeup; phenotype is observable traits. Genes determine genotype; their expression creates phenotype.

Flashcard 5: What is directional selection?

Answer: Selection that favors one extreme, shifting the average trait value. Pushes population toward one extreme trait value.

Flashcard 6: What is stabilizing selection?

Answer: Selection that favors intermediate traits, reducing variation. Eliminates extremes, maintaining average trait values.

Flashcard 7: What is disruptive selection?

Answer: Selection that favors both extremes, increasing variation. Eliminates intermediate values, creating two distinct groups.

Flashcard 8: Which evidence best supports natural selection: individuals change or populations change?

Answer: Populations change in trait frequencies over generations. Evolution occurs at population level, not individual level.

Flashcard 9: Identify the best conclusion: A heritable trait increases from $20\%$ to $60\%$ after drought.

Answer: The trait likely increased fitness under drought conditions. Large frequency increase suggests strong selective advantage.

Flashcard 10: Which option is the strongest evidence that a trait is heritable: similarity to parents or to habitat?

Answer: Similarity to parents (offspring resemble parents for the trait). Parent-offspring resemblance indicates genetic inheritance.

Flashcard 11: Identify the selection type: the darkest mice become most common on dark lava rock.

Answer: Directional selection. One extreme (darkest) is favored over lighter colors.

Flashcard 12: Identify the selection type: average beak size increases as only large seeds remain.

Answer: Directional selection. Larger beaks are favored when only large seeds are available.

Flashcard 13: Identify the selection type: very small and very large individuals survive poorly; medium survives best.

Answer: Stabilizing selection. Medium size has highest fitness; extremes are selected against.

Flashcard 14: Identify the selection type: only very small and very large beaks succeed; medium beaks decline.

Answer: Disruptive selection. Both extremes succeed while intermediate forms are selected against.

Flashcard 15: Which conclusion is supported: Trait A has $2\times$ higher offspring survival than Trait B for 5 generations.

Answer: Trait A frequency should increase over generations. Higher reproductive success leads to increased frequency over time.

Flashcard 16: What is the main difference between natural selection and genetic drift?

Answer: Selection is nonrandom; drift changes frequencies by chance. Selection is fitness-based; drift is random sampling error.

Flashcard 17: Identify the best conclusion: after a drought, deeper-beaked birds leave more offspring.

Answer: Drought favored deeper beaks, so deep-beak frequency should rise. Environmental change created selection for the adaptive trait.

Flashcard 18: Which option is the best evidence for selection: A) random change B) trait linked to higher offspring number?

Answer: B) Trait linked to higher offspring number. Reproductive advantage directly demonstrates natural selection.

Flashcard 19: What is disruptive selection?

Answer: Selection favors both extremes over the average phenotype. Can split a population into two distinct groups.

Flashcard 20: What is the difference between phenotype and genotype?

Answer: Phenotype is expressed traits; genotype is genetic makeup. Phenotype is observable; genotype is the underlying DNA.

Flashcard 21: Identify the evidence-based conclusion: a trait increases from $20\%$ to $60\%$ in 10 generations.

Answer: The trait likely increased fitness under the current conditions. Large frequency increase suggests strong positive selection.

Flashcard 22: Which statement best explains why individuals do not evolve by natural selection?

Answer: Selection changes trait frequencies in populations, not individuals. Evolution acts on populations through differential reproduction.

Flashcard 23: Identify the correct claim: natural selection acts on individuals or changes populations over generations?

Answer: It changes populations over generations. Selection acts on individuals but evolution occurs in populations.

Flashcard 24: What is the difference between genotype and phenotype?

Answer: Genotype is genetic makeup; phenotype is observable traits. Genotype determines phenotype through gene expression.

Flashcard 25: Identify the type of selection: in patchy habitat, light and dark mice survive; medium mice are seen.

Answer: Disruptive selection. Different habitats favor different camouflage colors.

Flashcard 26: What is the role of variation in natural selection?

Answer: Variation provides different traits for selection to act upon. No variation means no differential survival or reproduction.

Flashcard 27: Which type of evidence best supports natural selection in a population over time?

Answer: A consistent change in trait frequency across generations. Shows non-random change driven by differential fitness.

Flashcard 28: Which option is the strongest evidence that a trait is adaptive: A) common trait B) trait increases survival?

Answer: B) Trait increases survival (and reproduction) in that environment. Fitness advantage is the defining feature of adaptations.

Flashcard 29: Identify the correct claim: Natural selection acts on individuals or on populations?

Answer: Individuals are selected; populations evolve (trait frequencies change). Selection affects individual fitness; evolution occurs in populations.

Flashcard 30: Identify the correct statement about evolution: Does natural selection create new traits?

Answer: No; it selects among existing heritable variation. Selection only acts on variation from mutation and recombination.