BIO152 EVOLUTION TERMS

Biogeography: the geographic distribution of living organisms

Common ancestry: the concept that if you trace back the lineages of living species far enough in time, those species will converge to a shared ancestor

Evolution: the change in frequency of genetic variants in a population over

Fixation: the loss of all variants except one from a population

Homology: traits whose similarities are explained by common ancestry

Natural selection: the tendency for genetic variants that enhance fitness to go to fixation and variants that reduce fitness to be lost from populations

Nested classification: a pattern of groups nested within groups (without overlaps) as seen in taxonomies

Polymorphism: the existence of multiples variants within a population

Transitional fossil: fossil taxa that have some, but not all, of the derived traits of a living group

Speciation: lineage splitting that ultimately leads to taxa that are classified as different species

Branch: the lines that make up a tree diagram, which represent population lineages

Clade: all descendants of an ancestral lineage

Node: branching points of a tree diagram, which represent lineage splitting

Tip: the top of a tree, with taxon

Root: the base of a tree, representing the common ancestral lineage of all taxa in the tree

Taxon: named group of biologic organisms, often shown at the tips of trees

Most-recent common ancestor:

Pruning: remove tips or clades from a tree without changing the topology

Tree topology: a list of all the clades that the tree contains

Ancestral state reconstruction: the act of figuring out what an ancestral species could have looked like based on the traits of its “children”

Gains: a new trait or structure gained by evolution

Convergent evolution: phenomenon observed in phylogenetic trees where the same trait evolves separately in more than one lineage; although they appear similar, these traits are not homologous

Homologous: a descriptor of a character shared in separate species that was inherited from the common ancestor of those species

Losses: an old trait or structure is lost by evolution

Parsimony: the idea that given multiple hypotheses, the most likely hypothesis is the one that makes the fewest assumptions; in relation to phylogenetics, parsimony favors the scenario that invokes the minimum number of evolutionary changes (character loss/gain)

Reversal: the phenomenon in which an ancestral trait was lost and then re-evolved along a lineage

Allele: a particular variant of a gene

Allele frequency: in a population, the proportion of all alleles at a locus that are of a particular type

Evolution: change in the genetic composition of a population overtime

Locus: a place in the genome where alleles reside; in diploids, each individual has two alleles per locus

Phenotype: the physical and behavioral characteristics of an organism that result from the interaction of the organism’s genotype and its environment

Fixed/fixation: an allele that has a frequency of 1.0 in a population

Genotype: genetic makeup of an organism

Hardy-Weinberg law: the law that, when a few key assumptions hold, makes it possible to predict the genotype frequencies in a population for the next generation, based on the allele frequencies in the current generation

Plasticity: change that is caused by the environment and does not have a genetic component

Polymorphic: when more than one allele is found at a given locus in a population

Heterozygous: having inherited two different alleles

Homozygous: having inherited two of the same alleles

Population: a group of interbreeding organisms

Beneficial mutation: a new allele that enhances the fitness of organisms

Deleterious mutation: a new allele that decreases organismal fitness

Directional selection: selection that arises when one allele consistently raises fitness; eventually the beneficial allele is expected to become fixed in the population

Local adaptation mutation:

Natural selection:the process of allele frequency change due to fitness variation among genotypes at that locus

Neutral mutation: a new allele with neither a beneficial nor a deleterious effect

Relative fitness: the fitness of a given genotype divided by the fitness of a reference genotype, which relative fitness is assigned to be 1.0

Reproductive output: the average product of gamete abundance representing the reproductive effort of an individual

Fixation: the tendency of one genotype to become favored completely overtime

Genetic bottleneck: the phenomenon in which a population lineage shrinks to a small size for a period, causing that population to lose genetic variation

Genetic load: the frequency of deleterious alleles that have accumulated in a population

Polymorphism: random change in allele frequencies in a population over time

Mutation-selection balance: the frequency of genetic disorders is based on a balance between the rate of mutation and the strength of negative selection

Overdominant selection: selection in which heterozygote genotypes have the highest fitness

Trans-specific polymorphisms: a set of alleles that are shared between closely related species; they arose before speciation and were maintained as polymorphisms

Underdominant selection: selection in which heterozygote genotypes have the lowest fitness

Continuous trait: a trait that is characterized by values on a continuous scale, rather than being controlled by a single locus

Disruptive selection: selection that favors trait values at both extremes of the trait value distribution

Heritability: the fraction of the variation in a population that can be explained by genetics

Parent-offspring regression: the regression (heritability) calculated when parent and offspring values are plotted on a graph.

Response to selection (r) : the amount the mean trait value in a population changes after one generation

Stabilizing selection: selection that disfavors extreme trait values and favors trait values towards the center of the trait distribution

Standard deviation: square root of the variance

Strength of selection (s): response to selection assuming all variation is genetic

Variance: a measure of the spread of the distribution values in a population (technically, the sum of squared deviations from the mean value)

Altruism: actions that result in the organism exhibiting the behavior lowering its own fitness while increasing the fitness of other organisms within its population

Exaggerated secondary sexual characteristics: dramatic traits in an organism that lower the organism’s viability but evolve because they are favored by sexual selection

Female choice: females influence sexual selection by choosing which male they want to mate with

Group selection: favors traits that improve the survival of multi-individual groups, even if they do not favor each individual in the group

Male-male competition: the competition between males to attract females to mate with

Monogamy: one female and one male mate

Polygamy: when one male can mate with many females

Runaway sexual selection: the phenomenon in which secondary sexual characteristics become exaggerated due to feedback between male traits and female preferences ( or more rarely, female traits and male preferences)

Variance of reproductive output: the variance of reproductive output. Lol

Allopatric speciation: speciation driven by geographic isolation

Assortative mating: individual organisms tend to mate with other organisms with trait values like theirs

Biological species concept: the view that species are defined by the ability of their members to reproduce with one another and to be unable to reproduce with the members of other species

Clinical variation: gradual changes in traits as a function of geographic isolation

Discrete variation: genetic variation among geographically separated populations, where each population contains genetically smaller individuals

Disruptive selection: selection that favors the extreme phenotypes

Reproductive isolation:

Phylogenetic sp. Concept: the view that species are clades, like other in the taxonomic hierarchy, that biologists have chosen to assign to the species rank for practical reasons

Speciation: the splitting of an ancestral species into descendant species

Stabilizing selection: selection that favors the middle of the group

Sympatric speciation: speciation without geographic separation, driven by assortative mating within a population

Anoxygenic photosynthesis: the reduction of carbon dioxide to organic molecules using light energy win which something other than water is the electron donor and oxygen gas is not released

Archaea: microorganisms that are similar to bacteria in size and simplicity of structure but radically different in molecular organization. They are now believed to constitute an ancient intermediate group between the bacteria and eukaryotes.

Bacteria: a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some that can cause disease.

Cyanobacteria: a clade of bacteria characterized by its ability to perform oxygenic photosynthesis

Last universal common ancestor: the most recent common ancestor of all known life

Oxygenic photosynthesis: the reduction of carbon dioxide to organic molecules using light energy in which water is the electron donor and oxygen gas is released

Prokaryotic cells: a category of cells characterized by an outer membrane containing no internal membrane structures

Asgard archaea: asgard or Asgardarchaeota is a proposed superphylum consisting of a group of archaea that contain eukaryotic signature proteins. It appears that the eukaryotes, the domain that contains the animals, plants, and fungi, emerged within the Asgard, in a branch containing the Heimdallarchaeota

Autogenous hypothesis: the theory that mitochondria and nucleus both evolved within the same eukaryotic lineage

Endomembrane system: a group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins.

Endoplasmic reticulum: holds the ribosomes, acts as a membrane, transports stuff

Endosymbiotic hypothesis: the theory that mitochondria are derived from endosymbiotic bacteria taken up by the host cell whose genome is found in the eukaryotic nucleus

Inside-out model: a theory for development of eukaryotic internal compartments that suggests that the outer plasma membrane of a prokaryotic ancestor was pushed outward and ultimately fused to create the cytoplasm and plasma membrane of eukaryotes

Mitochondria: powerhouse of the cell

Organelle: membrane-bound compartment of a eukaryotic cell

Outside-in model: a theory for development of eukaryotes that starts with the production of vesicles within the cytoplasm by internalization

Plastid: chloroplast, where photosynthesis is conducted

Arboreal: tree-dwelling

Anthropoid: a higher primate, especially an ape

Dichromatic vision: partial color blindness in which the eye contains only two times of cone photopigment instead of the typical three

Diurnal: the characteristics of being active during the day

Frugivory: an animal that feeds on fruit

Hominid: a primate of a family that includes humans and their fossil ancestors and also (in recent systems) at least some of the great apes

Hominin: a primate of a taxonomic tribe which comprises those species regarded as human, directly ancestral to humans, or very closely related to humans

Trichromatic vision: color vision consisting of three cones, full human range of colors