Biology Flashcards: Evaluate Evidence For Population Change

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This deck focuses on Evaluate Evidence For Population Change, giving you a quick way to review the definitions, rules, and examples that matter most for Biology.

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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: Which evidence best supports common ancestry if two species share many identical DNA sequences?

Answer: High DNA sequence similarity (molecular homology). Genetic similarity indicates recent divergence from common ancestor.

Flashcard 2: A population has $p = 0.4$; what is the expected homozygous recessive frequency?

Answer: $q^2 = 0.36$. If $p = 0.4$, then $q = 0.6$, so $q^2 = 0.36$.

Flashcard 3: Calculate $q$ if the recessive phenotype frequency is $q^2 = 0.36$.

Answer: $q = 0.6$. Take the square root of the recessive phenotype frequency.

Flashcard 4: Which conclusion is best supported if a trait is heritable and individuals with it leave more offspring?

Answer: Natural selection can increase the trait’s allele frequency. Heritable traits under selection will increase in frequency over generations.

Flashcard 5: Which mechanism is most consistent with a new allele appearing after replication errors?

Answer: Mutation. DNA replication errors create entirely new genetic variants.

Flashcard 6: Which selection pattern is indicated when the average phenotype becomes more common over time?

Answer: Stabilizing selection. Selection against extremes increases frequency of intermediate phenotypes.

Flashcard 7: Which observation best supports genetic drift if allele frequencies change without fitness differences?

Answer: Random allele frequency shifts, strongest in small populations. Random changes are more pronounced in smaller population sizes.

Flashcard 8: A trait has $p = 0.9$; what is the expected frequency of the recessive allele?

Answer: $q = 0.1$. Allele frequencies must sum to 1, so $q = 1 - 0.9$.

Flashcard 9: Which comparison best supports descent with modification if forelimb bones match across mammals?

Answer: Homologous structures. Same bone pattern across species indicates common ancestral structure.

Flashcard 10: Which evidence best supports convergent evolution if two unrelated species share similar functions but not ancestry?

Answer: Analogous structures. Similar function without shared ancestry indicates independent evolution.

Flashcard 11: Which selection pattern is indicated when one extreme phenotype increases in frequency over time?

Answer: Directional selection. One extreme has higher fitness, shifting the population mean.

Flashcard 12: Which outcome indicates Hardy–Weinberg equilibrium if genotype frequencies match $p^2$, $2pq$, and $q^2$?

Answer: No evidence of evolution for that gene in that population. Matching Hardy-Weinberg expectations indicates no evolutionary forces acting.

Flashcard 13: Find the expected heterozygote frequency if $p = 0.5$ and $q = 0.5$.

Answer: $2pq = 0.5$. When allele frequencies are equal, heterozygotes reach maximum frequency.

Flashcard 14: Which selection pattern is indicated when both extremes increase and intermediates decrease?

Answer: Disruptive selection. Intermediates have lower fitness than either extreme phenotype.

Flashcard 15: Identify the best evidence for recent evolution if pesticide resistance rises in a pest population.

Answer: A measurable increase in resistance allele frequency over generations. Direct measurement of evolutionary change through allele frequency shifts.

Flashcard 16: Which mechanism is most consistent with random allele loss after a population bottleneck?

Answer: Genetic drift. Population bottlenecks reduce size, increasing random sampling effects.

Flashcard 17: Which mechanism is most consistent with increased allele mixing after individuals immigrate?

Answer: Gene flow. Immigration introduces new alleles and increases genetic mixing.

Flashcard 18: Which result best supports natural selection if a heritable trait increases survival and becomes common?

Answer: Trait-associated alleles increase in frequency over time. Higher survival leads to increased reproduction and allele transmission.

Flashcard 19: Which observation best supports gene flow as the cause if two populations become genetically similar?

Answer: Increased migration accompanied by reduced allele frequency differences. Migration homogenizes allele frequencies between previously distinct populations.

Flashcard 20: A trait has $q^2 = 0.04$; what is the expected heterozygote frequency $2pq$?

Answer: $2pq = 0.32$. If $q^2 = 0.04$, then $q = 0.2$, $p = 0.8$, so $2pq = 0.32$.

Flashcard 21: Calculate $p$ if the recessive phenotype frequency is $q^2 = 0.09$.

Answer: $p = 0.7$. If $q^2 = 0.09$, then $q = 0.3$ and $p = 1 - 0.3 = 0.7$.

Flashcard 22: Find the homozygous dominant genotype frequency if $p = 0.6$.

Answer: $p^2 = 0.36$. Square the dominant allele frequency: $0.6^2$.

Flashcard 23: Find the homozygous recessive genotype frequency if $q = 0.1$.

Answer: $q^2 = 0.01$. Square the recessive allele frequency: $0.1^2$.

Flashcard 24: Find the heterozygote frequency if $p = 0.7$ and $q = 0.3$.

Answer: $2pq = 0.42$. Multiply $2 \times 0.7 \times 0.3$ to get heterozygote frequency.

Flashcard 25: Calculate $p$ if the recessive allele frequency is $q = 0.2$.

Answer: $p = 0.8$. Since $p + q = 1$, subtract $q$ from 1.

Flashcard 26: Which result best supports natural selection if a heritable trait increases survival and becomes common?

Answer: Trait-associated alleles increase in frequency over time. Higher survival leads to increased reproduction and allele transmission.

Flashcard 27: Which mechanism is most consistent with increased allele mixing after individuals immigrate?

Answer: Gene flow. Immigration introduces new alleles and increases genetic mixing.

Flashcard 28: Which evidence best supports convergent evolution if two unrelated species share similar functions but not ancestry?

Answer: Analogous structures. Similar function without shared ancestry indicates independent evolution.

Flashcard 29: Find the homozygous recessive genotype frequency if $q = 0.1$.

Answer: $q^2 = 0.01$. Square the recessive allele frequency: $0.1^2$.

Flashcard 30: Calculate $p$ if the recessive phenotype frequency is $q^2 = 0.09$.

Answer: $p = 0.7$. If $q^2 = 0.09$, then $q = 0.3$ and $p = 1 - 0.3 = 0.7$.