Evolution
55 flashcards covering Evolution for the MCAT Biology & Biochemistry section.
Evolution is the process by which populations of organisms change over time, leading to the diversity of life we see today. It occurs through mechanisms like natural selection, where traits that improve survival and reproduction become more common, genetic mutations that introduce new variations, and other factors such as genetic drift. This concept forms the foundation of modern biology, explaining how species adapt to their environments and how all living things are connected through a shared history.
On the MCAT, evolution questions in the Biology and Biochemistry section often appear as multiple-choice items testing your grasp of key mechanisms, evidence from fossils and DNA, and applications like the evolution of drug resistance. Common traps include confusing evolution with purposeful design or overlooking the role of random events, so be cautious with interpretations of data. Focus on integrating evolution with genetics and ecology to answer questions about speciation and population dynamics effectively.
A concrete tip: Practice applying evolutionary principles to real-world medical scenarios, like pathogen adaptation.
Terms (55)
- 01
Natural Selection
Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring, leading to changes in the population over generations.
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Genetic Drift
Genetic drift is the random change in allele frequencies within a population, especially significant in small populations, and can lead to the loss or fixation of alleles without regard to their adaptive value.
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Gene Flow
Gene flow is the transfer of genetic variation from one population to another through the movement of individuals or gametes, which can introduce new alleles and reduce differences between populations.
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Mutation
Mutation is a change in the DNA sequence of an organism's genome, serving as the ultimate source of genetic variation that can drive evolutionary change when passed to subsequent generations.
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Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species, often due to reproductive isolation and accumulated genetic differences.
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Allopatric Speciation
Allopatric speciation occurs when a population is divided by a geographical barrier, leading to the evolution of reproductive isolation and the formation of new species in separate locations.
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Sympatric Speciation
Sympatric speciation happens within the same geographical area, typically through mechanisms like polyploidy or behavioral changes that cause reproductive isolation without physical barriers.
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Adaptive Radiation
Adaptive radiation is the rapid evolution of diversely adapted species from a common ancestor when new ecological opportunities arise, such as in isolated environments.
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Divergent Evolution
Divergent evolution is the process where related species evolve different traits due to different environmental pressures, resulting in increased differences over time.
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Convergent Evolution
Convergent evolution occurs when unrelated species develop similar traits independently in response to similar environmental challenges, such as the streamlined bodies of sharks and dolphins.
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Coevolution
Coevolution is the mutual evolutionary influence between two species, such as predators and prey, where changes in one species drive adaptations in the other.
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Punctuated Equilibrium
Punctuated equilibrium is a model of evolution proposing that species experience long periods of stability interrupted by short bursts of rapid change, rather than gradual transformation.
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Gradualism
Gradualism is the evolutionary concept that species change slowly and steadily over long periods through the accumulation of small genetic changes.
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Hardy-Weinberg Principle
The Hardy-Weinberg principle states that in a large, randomly mating population with no evolutionary forces, allele and genotype frequencies remain constant across generations, described by the equation p² + 2pq + q² = 1.
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Allele Frequency
Allele frequency is the proportion of a specific allele in a population, which can change over time due to evolutionary forces like selection or drift.
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Genetic Variation
Genetic variation refers to the diversity of alleles and genotypes within a population, providing the raw material for evolution through natural selection.
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Fitness
Fitness in evolutionary terms measures an organism's ability to survive and reproduce in its environment, determining how likely its genes are to be passed on to the next generation.
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Adaptation
Adaptation is a heritable trait that enhances an organism's survival and reproductive success in its specific environment, resulting from natural selection.
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Phylogeny
Phylogeny is the evolutionary history and relationships among organisms or groups of organisms, often represented in tree-like diagrams.
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Cladistics
Cladistics is a method of classifying organisms based on shared derived characteristics, constructing evolutionary trees that reflect common ancestry.
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Homologous Structures
Homologous structures are features in different species that arise from a common ancestor, such as the forelimbs of humans and bats, indicating evolutionary relatedness.
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Analogous Structures
Analogous structures are similar features in unrelated species that evolved independently for similar functions, like the wings of birds and insects.
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Vestigial Structures
Vestigial structures are reduced or nonfunctional traits in an organism that were functional in ancestral species, such as the human appendix, providing evidence for evolution.
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Fossil Record
The fossil record is the collection of fossils that documents the history of life on Earth, showing patterns of evolution, extinction, and diversification over time.
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Comparative Anatomy
Comparative anatomy is the study of similarities and differences in the body structures of different species, revealing evolutionary relationships and common descent.
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Biogeography
Biogeography is the study of the geographical distribution of species and their evolution, explaining patterns like why similar species are found on different continents.
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Molecular Clock
The molecular clock is a technique using the constant rate of molecular evolution to estimate the time since two species diverged from a common ancestor.
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Darwin's Finches
Darwin's finches are a group of bird species in the Galápagos Islands that evolved from a common ancestor, with beak variations adapted to different food sources, illustrating adaptive radiation.
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Industrial Melanism
Industrial melanism is the darkening of peppered moth populations during the Industrial Revolution due to natural selection favoring darker individuals in polluted environments.
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Antibiotic Resistance
Antibiotic resistance is the evolution of bacteria that can survive exposure to antibiotics, driven by mechanisms like mutation and selection, posing challenges in medicine.
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Peppered Moth Example
The peppered moth example demonstrates natural selection, where the proportion of dark moths increased in polluted areas because they were less visible to predators on soot-covered trees.
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Lamarck's Theory
Lamarck's theory proposed that organisms acquire traits during their lifetime and pass them to offspring, such as giraffes stretching their necks, but it has been discredited by modern genetics.
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Darwin's Theory of Evolution
Darwin's theory of evolution by natural selection posits that species originate from a common ancestor through gradual changes driven by variation, inheritance, and differential survival.
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Wallace's Contributions
Alfred Russel Wallace independently developed the idea of natural selection, similar to Darwin, and contributed to biogeography and the concept of species distribution.
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Sexual Selection
Sexual selection is a form of natural selection where traits that increase mating success, such as bright plumage in birds, are favored, even if they reduce overall survival.
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Stabilizing Selection
Stabilizing selection favors intermediate phenotypes and reduces extremes in a population, such as human birth weight, leading to less variation over time.
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Directional Selection
Directional selection favors one extreme phenotype over others, shifting the population's traits in that direction, like the evolution of longer necks in giraffes.
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Disruptive Selection
Disruptive selection favors both extreme phenotypes over the intermediate, potentially leading to speciation, as seen in finches with different beak sizes.
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Bottleneck Effect
The bottleneck effect is a type of genetic drift where a population is drastically reduced, reducing genetic variation, and the surviving population may differ randomly from the original.
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Founder Effect
The founder effect occurs when a small group from a larger population establishes a new one, leading to reduced genetic diversity due to the limited alleles in the founders.
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Inbreeding
Inbreeding is the mating between closely related individuals, which increases homozygosity and can expose deleterious recessive alleles, affecting population evolution.
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Outbreeding
Outbreeding is mating between unrelated individuals, which increases genetic variation and can enhance evolutionary adaptability through hybrid vigor.
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Reproductive Isolation
Reproductive isolation is any factor that prevents interbreeding between populations, a key step in speciation, and can be prezygotic or postzygotic.
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Prezygotic Isolation
Prezygotic isolation prevents mating or fertilization between species, such as through temporal differences or behavioral incompatibilities, maintaining species boundaries.
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Postzygotic Isolation
Postzygotic isolation occurs after fertilization, where hybrid offspring are infertile or have reduced fitness, reinforcing species separation through natural selection.
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Hybrid Zones
Hybrid zones are regions where two closely related species interbreed, producing hybrids, and can serve as areas to study the dynamics of speciation and gene flow.
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Macroevolution
Macroevolution refers to large-scale evolutionary patterns and processes above the species level, such as the origin of major groups, as opposed to microevolution.
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Microevolution
Microevolution is the change in allele frequencies within a population over a short period, driven by mechanisms like selection and mutation, and is the basis for larger evolutionary changes.
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Evolutionary Arms Race
The evolutionary arms race is the ongoing reciprocal adaptation between interacting species, like predators and prey, where each evolves countermeasures to the other's traits.
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Neutral Theory of Evolution
The neutral theory posits that much of molecular evolution is due to genetic drift of neutral mutations rather than natural selection, explaining some genetic variations.
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Kin Selection
Kin selection is a form of natural selection that favors behaviors benefiting relatives, increasing the individual's inclusive fitness even if it reduces personal reproduction.
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Altruism in Evolution
Altruism in evolution refers to behaviors that benefit others at a cost to the individual, explained by kin selection or reciprocal altruism, promoting gene survival.
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Common Trap: Lamarck vs. Darwin
A common trap is confusing Lamarck's idea of acquired traits being inherited with Darwin's natural selection, where only heritable variations are passed on and selected.
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Strategy for Hardy-Weinberg Problems
To solve Hardy-Weinberg problems, ensure conditions like no mutation or selection are met, use the equation p + q = 1 to find frequencies, and calculate probabilities for genotypes.
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Evidence from DNA Sequences
DNA sequence comparisons provide evidence for evolution by showing similarities proportional to relatedness, such as humans sharing about 98% of DNA with chimpanzees.