Exam 1
Terms
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- Evolution
- Descent with modification
- Fossils
- Remains or traces of organisms from the past
- Strata
- Layers of rock
- Paleontology
- Study of fossils
- Catastrophism
- The principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present.
- Uniformitarianism
- Principle which stated that mechanisms of change are constant over time.
- Adaptations
- Characteristics of organisms that enhance their survival and reproduction in specific environments
- Natural selection
- A process in which individuals with certain inherited traits leave more offspring than individuals with other traits.
- Artificial selection
- Selecting and breeding individuals that possess desired traits.
- Homology
- Similarity in characteristics resulting from a shared ancestry
- Homologous structures
- Structures in different species that are similar because of common ancestry
- Vestigial structures
- A structure of marginal, if any, importance to an organism. They are historical remnants of structure that had important functions in ancestors.
- Evolutionary tree
- A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms.
- Convergent evolution
- The evolution of similar features in independent evolutionary lineages
- Analogous
- Having characteristics that are similar because of convergent evolution, not homology
- Biogeography
- The study of the past and present distribution of species
- Continental drift
- The slow movement of the continental plates across Earth's surface
- Pangaea
- The supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the land masses together
- Endemic
- Referring to a species that is confined to a specific, relatively small geographic area
- Microevolution
- Evolutionary change below the species level; change in the allele frequencies in a population over generations
- Average heterozygosity
- The percent, on average, of a population's loci that are heterozygous in members of the population
- Geographic variation
- Differences between the gene pools of geographically separate populations or population subgroups
- Cline
- A graded change in a character along a geographic axis
- Mutation
- A change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity. Mutations can arise in the DNA and RNA of a virus.
- Population
- A localized group of individuals of the same species that can interbreed, producing fertile offspring.
- Gene pool
- The aggregate of all the alleles for all the loci in all individuals in a population.
- Hardy-Weinberg principle
- The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendalian segregation and recombination of alleles are at work.
- Hardy-Weinberg equilibrium
- The condition describing a nonevolving population (one that is in genetic equilibrium).
- Genetic drift
- A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.
- Founder effect
- Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
- Bottleneck effect
- Genetic drift that occurs when the size of a population is reduced, as by natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population.
- Gene flow
- The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.
- Relative fitness
- The contribution an individual makes to the gene pool of the next generation, relative to the contributions of others in the population.
- Directional selection
- Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
- Disruptive selection
- Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do other individuals with intermediate phenotypes.
- Stabilizing selection
- Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
- Sexual selection
- A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
- Sexual dimorphism
- Marked differences between the secondary sex characteristics of males and females.
- Intrasexual selection
- A direct competition of individuals of one sex (usually males in vertebrates) for mates of the opposite sex.
- Intersexual selection
- Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.
- Balancing selection
- Natural selection that maintains two or more phenotypic forms in a population.
- Heterozygote advantage
- Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
- Frequency-dependent selection
- A decline in the reproductive success of individuals that have a phenotype that has become too common in a population
- Neutral variation
- Genetic variation that does not appear to provide a selective advantage or disadvantage.
- Speciation
- An evolutionary process in which one species splits into two or more species
- Macroevolution
- Evolutionary change above the species level, including the origin of a new group of organisms or a shift in the broad pattern of evolutionary change over a long period of time.
- Species
- A population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups.
- Reproductive isolation
- The existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring
- Hybrids
- Offspring that results from the mating of individuals from two different species or two true-breeding varieties of the same species.
- Prezygotic barriers
- A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted
- Postzygotic barriers
- A reproductive barrier that prevent hybrid zygotes produced by two different species from developing viable, fertile adults.
- Morphological species concept
- A definition of species in terms of measurable anatomical criteria
- Ecological species concept
- A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.
- Phylogenetic species concept
- A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.
- Allopatric speciation
- The formation of new species in populations that are geographically isolated from one another
- Sympatric speciation
- The formation of new species in a population that live in the same geographical area
- Polyploidy
- A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is a result of an accident of cell division.
- Autopolyploid
- An individual that has more than two chromosome sets that are all derived from a single species.
- Allopolyploid
- A fertile individual that has more than two chromosomes sets as a result of two different species interbreeding and combining their chromosomes
- Hybrid zone
- A geographic region in which members of species meet and mate, producing at least some offspring of mixed ancestry.
- Reinforcement
- A process in which natural selection strengthens prezygotic barriers to reproduction, thus reducing the chances of hybrid formation. Such a process is likely to occur only if hybrid offspring are less fit than members of the parent species.
- Punctuated equilibria
- In the fossil record, long periods of apparent stasis, in which a species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change.
- Protobionts
- A collection of abiotically produced molecules surrounded by a membrane or membrane-like structure.
- Ribozymes
- An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
- Radiometric dating
- A method for determining the absolute ages of rocks and fossils, based on the half-life of radioactive isotopes.
- Half-life
- The amount of time it takes for 50% of a sample of radioactive isotope to decay.
- Geologic record
- The division of Earth's history into time periods
- Stromatolites
- Layered rock that results from the activities of prokaryotes that bind thin films of sediment together
- Endosymbiosis
- A process in which a unicellular organism (the host) engulfs another cell, which lives within the host cell an ultimately becomes an organelle in the host cell
- Serial endosymbiosis
- A hypothesis for the origin of eurkaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chlorplasts and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells.
- Cambrian explosion
- A relatively brief time in Geologic history, when large hard-bodied forms of animals with most of the major body plans known today appeared in the fossil record.
- Adaptive radiations
- Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill vacant ecological roles in their communities.
- Heterochrony
- Evolutionary change in the timing or rate of an organisms development.
- Paedomorphosis
- The retention in an adult organism of the juvenile features of its evolutionary ancestors.
- Homeotic genes
- Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants and fungi by controlling the developmental fate of groups of cells.
- Phylogeny
- The evolutionary history of a species or group of related species
- Systematics
- A scientific discipline focused on classifying organisms and determining their evolutionary relationships
- Taxonomy
- A scientific discipline concerned with naming and classifying the diverse forms of life.
- Binomial
- The two part latinized name of a species, consisting of the genus and specific epithet
- Taxon
- A named taxonomic unit at any given level of classification
- Order of classifications
- Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
- Phylogenetic tree
- A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms
- PhyloCode
- system of classification of organisms based on evolutionary relationships. Only groups that include a common ancestor and all its descendents are named.
- Branch points
- The representation of on a phylogenetic tree of the divergence of two or more taxa from a common ancestor.
- Sister taxa
- Groups of organisms that share an immediate ancestor and hence are each others closest relatives.
- Polytomy
- In a phylogenetic tree, a branch point from which more than two descendent taxa emerge. It indicates that the evolutionary relationships among the descendent taza are not yet clear.
- Analogy
- Similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.
- Homoplasies
- Similar (homologous) structure or molecular sequence that has evolved independently in two species.
- Molecular systematics
- a scientific discipline that uses nucleic acids or other molecules in different species to infer evolutionary relationships.
- Cladistics
- An approach to systematics in which organisms are placed into groups called clades based primarily on common descent
- Clades
- A group of species that includes an ancestral species and all its descendents.
- Monophyletic
- Pertaining to a group of taxa that consists of a common ancestor and all its descendents. A monophyletic taxa is equivalent to a clade.
- Paraphyletic
- Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendents.
- Polyphyletic
- Pertaining to a group of taxa derived from two or more different ancestors.
- Shared ancestral character
- A character, shared by members of a particular clade, that originated in an ancestor that is not a member of that clade.
- Shared derived character
- An evolutionary novelty that is unique to a particular clade.
- Outgroup
- A species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied.
- Ingroup
- A species or group of species whose evolutionary relationships we seek to determine
- Maximum parsimony
- A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts.
- Maximum likelihood
- As applied to systematics, a principle that states that when considering multiple phylogenetic hypotheses, one should take into account the hypothesis that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time.
- Phylogenetic bracketing
- An approach in which features shared by two groups of organisms are predicted (by parsimony) to be present in their common ancestor and all of its descendents.
- Orthologous genes
- Homologous genes that are found in different species because of speciation
- Paralogous genes
- Homologous genes that are found in the same genome as a result of gene duplication
- Molecular clock
- A method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes appear to evolve at constant rates.
- Neutral theory
- The hypothesis that much evolutionary changes in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection.
- Horizontal gene transfer
- The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.