Evolution and Natural Selection
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40 terms
Terms | Definitions |
|---|---|
 Plato | philosopher that believed organisms have a perfect divine form, but on earth they slightly deviate |
| Aristotle | philosopher that believed that 1. species are fixed types, and 2. some species are more complex than others |
| Lamarck | biologist that believed species change through time via the inheritance of acquired characteristics; evolution occurred through simple organisms originating from spontaneous generation; evolution is progressive |
| evolution | what occurs because traits vary among the individual in a population (according to Darwin and Wallace) and because certain traits leave more offspring than others do |
| population | individuals of the same species living in the same area at the same time |
| population thinking | Darwin's idea that variation among individuals in a population is the key to understanding the nature of species |
| descent with modification | species that lived in the past are ancestors of species living today, and that species with their descendant species change through time |
| extant | species living today |
| extinct | a species that no longer exists |
| vestigial trait | Reduced or incompletely developed structure in an organism that has no function or reduced function, but is clearly similar to functioning organs or structures in closely related species |
| genetic drift | random change in allele frequencies that occurs in small populations |
| homology | similarity that exists in species because they both inherited the trait from a common ancestor |
| fitness | the ability of an individual to produce surviving offspring, relative to that ability in other individuals in the population |
| adaptation | a heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait |
| genetic variation | the number and frequency of alleles that are present in a particular population |
| directional selection | form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve |
| purifying selection | when disadventageous alleles decline in frequency |
| stabilizing selection | a form of natural selection that favors intermediate variants by acting against extreme phenotypes |
| disruptive selection | form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle |
| balancing selection | a form of natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism) |
| natural selection | process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest |
| typological thinking | species are unchanging types, and unimportant/misleading..The concept that living organisms conform to a specific norm, and that variation in organisms is abnormal |
| transitional forms | fossils that connect ancestral species with their descendants through a series of tiny steps |
| genetic homology | Similarity in the DNA sequences of genes from different species |
| developmental homology | species that differ as adults often bear striking similarities during embryonic stages |
| structural homology | traits in two organisms that are similar because they were derived from a single trait in a common ancestor (vertebrate limb bones) |
| genetic constraints | selection was not able to optomize all aspects of a trait; genetic correlation |
| fitness trade offs | occur because every individual has a restricted amount of time and energy at its disposal- its resources are limited |
| historical constraints | all traits have evolved from pre existing traits |
| gene pool | consists of all genes, including all the different alleles, that are present in a population |
| Hardy-Weinberg principle | is used to describe a gene pool of a population that is not evolving |
| heterozygote advantage | Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools. |
| sampling error | the accidental selection of a unrepresentative sample from some larger population, due to chance |
| genetic marker | a specific gene that produces a recognizable trait and can be used in family or population studies |
| founder effect | change in allele frequencies that occurs when a new population is established |
| genetic bottleneck | The concept that, when populations are severely reduced in size, they may lose some of their genetic diversity |
| gene flow | movement of alleles into or out of a population due to the migration of individuals to or from the population |
| mutation | a random error, evolutionary mechanism in gene replication that leads to an increased genetic diversity in a population |
| deleterious allele | a version of a gene that on average, decreased the fitness of the organism carrying it. |
| inbreeding | the act of mating closely related individuals, form of selective breeding |
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