Biology Flashcards: Evaluate Evidence For Population Change

What this deck covers

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.

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: Which type of selection maintains multiple alleles because heterozygotes have highest fitness?

Answer: Heterozygote advantage (balancing selection). Heterozygotes outperform both homozygotes, preserving both alleles.

Flashcard 2: Which outcome indicates a population is evolving when compared to Hardy–Weinberg expectations?

Answer: Observed genotype frequencies differ from expected frequencies. Deviations from Hardy-Weinberg predictions indicate evolutionary forces acting.

Flashcard 3: 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 4: 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 5: 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 6: 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 7: What is the definition of allele frequency in a population?

Answer: Proportion of all gene copies that are a specific allele. Calculated by dividing copies of one allele by total gene copies in the population.

Flashcard 8: Which mechanism is most consistent with a new allele appearing after replication errors?

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

Flashcard 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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 15: 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 16: 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 17: Which selection pattern is indicated when both extremes increase and intermediates decrease?

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

Flashcard 18: 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 19: 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 20: Which mechanism is most consistent with increased allele mixing after individuals immigrate?

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

Flashcard 21: 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 22: 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 23: Which statement best defines evolution at the population level?

Answer: Change in allele frequencies over time. Evolution occurs when allele proportions shift between generations.

Flashcard 24: What is the Hardy–Weinberg principle used to evaluate in populations?

Answer: Whether a population is evolving (deviating from equilibrium). Compares observed frequencies to equilibrium expectations to detect evolution.

Flashcard 25: What are the five conditions required for Hardy–Weinberg equilibrium?

Answer: No selection, no mutation, no migration, random mating, very large $N$. These conditions prevent allele frequency changes, maintaining equilibrium.

Flashcard 26: State the Hardy–Weinberg allele frequency equation.

Answer: $p + q = 1$. For a two-allele system, frequencies must sum to one.

Flashcard 27: Which term describes a change in allele frequencies in a population across generations?

Answer: Microevolution. Evolution within a population, as opposed to macroevolution between species.

Flashcard 28: State the Hardy–Weinberg genotype frequency equation.

Answer: $p^2 + 2pq + q^2 = 1$. Expansion of $(p + q)^2$ gives genotype frequencies for diploid organisms.

Flashcard 29: 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 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 $p = 1 - 0.3 = 0.7$.