10/12 10 Evolution by Natural Selection Free Online FlashCards

What is evolution?

Evolution is descent with modification: populations accumulate heritable changes across generations, producing biological diversity and differences among lineages.

What is the population-level definition of evolution?

Populations evolve when allele frequencies change across generations. Individual organisms may develop or acclimate during their lifetimes, but they do not evolve individually.

What do transitional fossils show?

Transitional fossils have combinations of traits that connect major groups; they are not half-finished organisms. Tiktaalik, for example, links fish and early limbed vertebrates.

What is a homologous structure?

Homologous structures share an underlying developmental or anatomical origin because of common ancestry, even when their functions differ.

What are analogous structures?

Analogous structures perform similar functions but evolved independently. They commonly illustrate convergent evolution under similar environmental pressures.

What four conditions are required for natural selection?

Natural selection requires variation, heritability, competition or limited resources, and differential reproductive success.

What does fitness mean in evolutionary biology?

Fitness is relative reproductive success: an organism has higher fitness if it contributes more viable, fertile offspring to future generations under the conditions studied.

What is an adaptation?

An adaptation is a heritable trait that increases fitness in a particular environment, or the evolutionary process by which a population becomes better suited to recurring conditions.

How does acclimation differ from adaptation?

Acclimation is a reversible physiological or behavioral adjustment by an individual. Adaptation is a heritable population-level change accumulated across generations.

What is mutation’s evolutionary role?

Mutation is the ultimate source of new alleles. Mutations do not occur because an organism needs a particular trait; their effects may be neutral, harmful, or beneficial in a given environment.

What is genetic drift?

Genetic drift changes allele frequencies by chance and is especially influential in small populations. Founder effects and bottlenecks are important examples.

What are the Hardy–Weinberg equations for two alleles?

For two alleles, p + q = 1 and p² + 2pq + q² = 1. The terms represent allele frequencies and expected AA, Aa, and aa genotype frequencies.