Evolution
87 flashcards by MentisLibrary
How natural selection, drift, and gene flow actually change populations, and how new species form. Includes the fossil, molecular, and biogeographic evidence, human origins, and the misconceptions that trip almost everyone up.
- What is the biological definition of evolution?
- A change in the heritable characteristics, or allele frequencies, of a population over generations
- Who published On the Origin of Species and in what year?
- Charles Darwin, in 1859
- Which naturalist independently reached the same theory and prompted Darwin to publish?
- Alfred Russel Wallace
- What are the four conditions required for natural selection?
- Variation, heritability, differential survival or reproduction, and more offspring than can survive
- What is fitness in evolutionary terms?
- Reproductive success, meaning the number of offspring an individual contributes to the next generation
- What is an adaptation?
- A heritable trait that increases an organism's fitness in its environment
- What is the difference between artificial and natural selection?
- In artificial selection humans choose which individuals reproduce; in natural selection the environment does
- What is directional selection?
- Selection that favors one extreme of a trait, shifting the population mean toward it
- What is stabilizing selection?
- Selection that favors intermediate values and removes both extremes
- What is disruptive selection?
- Selection that favors both extremes over the intermediate, potentially splitting a population
- What is sexual selection?
- Selection driven by differences in mating success rather than survival
- What is a sexual dimorphism?
- A consistent difference in appearance between males and females of the same species
- What is kin selection?
- Selection favoring behavior that helps relatives, because relatives share genes
- What is genetic drift?
- Random change in allele frequencies from chance sampling of who reproduces
- What is the founder effect?
- Reduced and shifted genetic variation when a small group establishes a new population
- What is a population bottleneck?
- A sharp reduction in population size that removes much of the genetic variation by chance
- What is gene flow?
- The movement of alleles between populations through migration and interbreeding
- What is the ultimate source of all new genetic variation?
- Mutation
- Are mutations directed toward what an organism needs?
- No, mutations occur regardless of whether they would be useful
- What is the biological species concept?
- A species is a group of populations whose members can interbreed and produce fertile offspring
- What is allopatric speciation?
- Speciation that occurs after a physical barrier geographically separates populations
- What is sympatric speciation?
- Speciation without geographic separation
- What is a prezygotic isolating mechanism?
- A barrier that prevents mating or fertilization from happening at all
- What is a postzygotic isolating mechanism?
- A barrier that acts after fertilization, reducing hybrid viability or fertility
- What is adaptive radiation?
- Rapid diversification of one lineage into many species filling different ecological roles
- What is a ring species?
- A chain of connected populations that interbreed with neighbors but not at the ends where the chain meets
- What is convergent evolution?
- Unrelated lineages independently evolving similar traits under similar selective pressures
- What is a homologous structure?
- A structure shared by different species because it was inherited from a common ancestor
- What is an analogous structure?
- A structure with similar function but separate evolutionary origins
- What is a vestigial structure?
- A reduced structure that retains little or no function compared with its ancestral role