Biology Flashcards: Explain Natural Selection Process

What this deck covers

This deck focuses on Explain Natural Selection Process, 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 outcome defines evolution by natural selection over time?

Answer: Increased frequency of alleles that improve fitness in that environment. Beneficial alleles become more common over successive generations.

Flashcard 2: What is artificial selection?

Answer: Human-directed breeding that increases desired traits. Demonstrates selection principles through deliberate breeding choices.

Flashcard 3: Limited application: If both very small and very large newborns have lower survival, which selection pattern is most likely?

Answer: Stabilizing selection favoring intermediate size. Extreme sizes have survival disadvantage; selection favors intermediate.

Flashcard 4: What is the key difference between natural selection and genetic drift?

Answer: Selection is nonrandom; drift is random change in allele frequencies. Selection has direction; drift is random sampling error.

Flashcard 5: What is meant by "natural selection is not goal-directed"?

Answer: It has no foresight; it favors traits beneficial in current conditions. Selection responds to current conditions, not future needs.

Flashcard 6: Which condition is violated if every individual has the same phenotype for a trait?

Answer: Variation. No differences means selection has nothing to act upon.

Flashcard 7: What is the role of overproduction of offspring in natural selection?

Answer: Creates competition because not all offspring can survive and reproduce. Limited resources force competition, enabling selection to act.

Flashcard 8: What does the term "fitness" mean in evolutionary biology?

Answer: Relative reproductive success in a given environment. Not physical strength, but reproductive output compared to others.

Flashcard 9: Limited application: If a population becomes better camouflaged over time, what must have been true about the trait?

Answer: Camouflage variation was heritable and affected fitness. Improvement over time proves genetic basis and fitness advantage.

Flashcard 10: What is the founder effect?

Answer: Genetic drift when a new population is started by a small group. Small founding group doesn't represent full genetic diversity.

Flashcard 11: What four conditions must be present for natural selection to occur?

Answer: Variation, heritability, overproduction/competition, differential fitness. These prerequisites enable selection to change allele frequencies across generations.

Flashcard 12: What is meant by "heritable variation"?

Answer: Trait differences caused by genes that can be passed to offspring. Genetic basis ensures traits can be transmitted to next generation.

Flashcard 13: What is meant by "heritable variation"?

Answer: Trait differences caused by genes that can be passed to offspring. Genetic basis ensures traits can be transmitted to next generation.

Flashcard 14: Limited application: In a stable environment, which selection type most often maintains the mean phenotype?

Answer: Stabilizing selection. Stable conditions typically favor existing optimal phenotype.

Flashcard 15: Limited application: If a trait increases survival but reduces mating success, what determines its net selection?

Answer: Overall effect on total reproductive success (fitness). Trade-offs require evaluating overall reproductive success.

Flashcard 16: What is a common misconception about need and evolution that you must avoid?

Answer: Individuals do not evolve traits because they need them. Traits don't evolve because organisms want them.

Flashcard 17: What does the term "fitness" mean in evolutionary biology?

Answer: Relative reproductive success in a given environment. Not physical strength, but reproductive output compared to others.

Flashcard 18: What does "survival of the fittest" mean in precise biological terms?

Answer: Those with higher fitness leave more surviving offspring. Fitness measures reproductive success, not physical prowess.

Flashcard 19: Which outcome defines evolution by natural selection over time?

Answer: Increased frequency of alleles that improve fitness in that environment. Beneficial alleles become more common over successive generations.

Flashcard 20: What is meant by "natural selection is not goal-directed"?

Answer: It has no foresight; it favors traits beneficial in current conditions. Selection responds to current conditions, not future needs.

Flashcard 21: What is a selective advantage?

Answer: A trait that increases fitness relative to other variants. Beneficial trait compared to alternatives in same environment.

Flashcard 22: Limited application: A pesticide kills most insects, but resistant insects survive and reproduce. What process is shown?

Answer: Natural selection increasing resistance allele frequency. Resistant survivors reproduce, passing resistance genes to offspring.

Flashcard 23: Limited application: If average-sized seeds are easiest to eat, which selection pattern is most likely?

Answer: Disruptive selection favoring small and large seeds. Intermediate phenotypes experience strongest predation pressure.

Flashcard 24: Which condition is violated if a trait difference is purely environmental and not genetic?

Answer: Heritability. Without genetic basis, traits can't be passed to offspring.

Flashcard 25: What is differential survival in the context of natural selection?

Answer: Individuals with advantageous traits survive at higher rates. Favorable traits increase survival probability compared to alternatives.

Flashcard 26: What does "survival of the fittest" mean in precise biological terms?

Answer: Those with higher fitness leave more surviving offspring. Fitness measures reproductive success, not physical prowess.

Flashcard 27: Which condition is violated if all individuals survive and reproduce equally?

Answer: Differential fitness (differential survival and reproduction). Equal success means no selection pressure exists.

Flashcard 28: What is directional selection?

Answer: Selection favors one extreme phenotype, shifting the population mean. Pushes population toward one extreme in response to environmental pressure.

Flashcard 29: What process shuffles existing alleles into new combinations in sexual reproduction?

Answer: Recombination (crossing over and independent assortment). Increases genetic diversity by creating new allele combinations.

Flashcard 30: Limited application: If a beneficial trait is heritable, what happens to its allele frequency over generations?

Answer: It tends to increase in frequency. Selection increases frequency of advantageous heritable traits.

Flashcard 31: Which condition is violated if a trait difference is purely environmental and not genetic?

Answer: Heritability. Without genetic basis, traits can't be passed to offspring.

Flashcard 32: What is the difference between adaptation and acclimation?

Answer: Adaptation is genetic across generations; acclimation is within-lifetime change. Adaptation requires genetic change; acclimation is physiological adjustment.

Flashcard 33: What is meant by "relative fitness"?

Answer: Fitness compared with other individuals in the same population. Fitness is always measured relative to population members.

Flashcard 34: What is the original source of new alleles that selection can act on?

Answer: Mutation. Creates genetic variation necessary for natural selection to operate.

Flashcard 35: What is meant by "selection acts on phenotypes"?

Answer: The environment favors observable traits, not alleles directly. Environment selects based on what organisms look/act like.

Flashcard 36: What is the relationship between phenotype and genotype in natural selection?

Answer: Selection favors phenotypes; evolution occurs via genotype (allele) changes. Observable traits are selected, but genetic changes drive evolution.

Flashcard 37: Limited application: If a beneficial trait is heritable, what happens to its allele frequency over generations?

Answer: It tends to increase in frequency. Selection increases frequency of advantageous heritable traits.

Flashcard 38: Limited application: If a population experiences a sudden drought, what changes first: individuals or allele frequencies?

Answer: Individuals are filtered first; allele frequencies change across generations. Selection acts immediately; evolution requires generational change.

Flashcard 39: Limited application: In a stable environment, which selection type most often maintains the mean phenotype?

Answer: Stabilizing selection. Stable conditions typically favor existing optimal phenotype.

Flashcard 40: What is the environment's role in natural selection?

Answer: It determines which phenotypes have higher fitness. Environmental conditions determine which traits are advantageous.

Flashcard 41: Limited application: If a trait increases survival but reduces mating success, what determines its net selection?

Answer: Overall effect on total reproductive success (fitness). Trade-offs require evaluating overall reproductive success.

Flashcard 42: Limited application: If a trait is advantageous but not heritable, will natural selection cause evolution of that trait?

Answer: No, because allele frequencies will not change. Without heritability, beneficial traits can't increase in frequency.

Flashcard 43: What four conditions must be present for natural selection to occur?

Answer: Variation, heritability, overproduction/competition, differential fitness. These prerequisites enable selection to change allele frequencies across generations.

Flashcard 44: What changes over generations during natural selection: traits in individuals or allele frequencies in populations?

Answer: Allele frequencies in populations. Evolution is defined as changes in genetic composition of populations.

Flashcard 45: What is the correct sequence of events in natural selection?

Answer: Variation → heritability → competition → differential reproduction → allele change. Standard order from initial variation to evolutionary change.

Flashcard 46: What is a selection coefficient in general terms?

Answer: A measure of the strength of selection against a genotype. Quantifies how strongly selection acts against certain genotypes.

Flashcard 47: Identify the correct statement: selection creates variation or selection sorts existing variation?

Answer: Selection sorts existing heritable variation. Selection filters existing traits; mutation creates new variation.

Flashcard 48: What is differential reproduction in the context of natural selection?

Answer: Individuals with advantageous traits produce more surviving offspring. Favorable traits lead to more offspring reaching reproductive age.

Flashcard 49: What is meant by "relative fitness"?

Answer: Fitness compared with other individuals in the same population. Fitness is always measured relative to population members.

Flashcard 50: Limited application: If a population becomes better camouflaged over time, what must have been true about the trait?

Answer: Camouflage variation was heritable and affected fitness. Improvement over time proves genetic basis and fitness advantage.

Flashcard 51: Limited application: If both very small and very large newborns have lower survival, which selection pattern is most likely?

Answer: Stabilizing selection favoring intermediate size. Extreme sizes have survival disadvantage; selection favors intermediate.

Flashcard 52: Limited application: If predators remove the slowest prey, which selection pattern is most likely?

Answer: Directional selection favoring faster individuals. Predation creates strong selection pressure favoring speed.

Flashcard 53: What is the unit of evolution: individual organism or population?

Answer: Population. Individuals don't evolve; populations change allele frequencies over time.

Flashcard 54: What is the correct sequence of events in natural selection?

Answer: Variation → heritability → competition → differential reproduction → allele change. Standard order from initial variation to evolutionary change.

Flashcard 55: Which condition is violated if all individuals survive and reproduce equally?

Answer: Differential fitness (differential survival and reproduction). Equal success means no selection pressure exists.