Exam 1: bio 191, ch19-25

evolution

Decent with modification: the process by which species accumulate differences from their ancestors as they adapt to different environments over time; also defined as a change in the genetic composition of a population from generation to generation

fossils

a preserved remnant or impression of an organism that lived in the past

adaptation

inherited characteristic of an organism that enhances its survival and reproduction in a specific environment

natural selection

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

artificial selection

process in which humans select and breed individuals that have desired traits

homology

similarity in characteristics resulting from shared ancestry

homologous structures

structures in different species that are similar because of common ancestry; these similar structures may or may not have similar functions ex. whale fins and human arms

convergent evolution

The evolution of similar features in independent evolutionary lineages

analogous

having characteristics that are similar because of convergent evolution, not homology

biogeography

study of geographic distribution of species

phylogeny

the evolutionary history of a species or group of related species

taxon

a named taxonomic unit at ent given level of classification

phylogenetic tree

a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms

branch point

The representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor. A branch point is usually shown as a dichotomy in which a branch representing the ancestral lineage splits (at the branch point) into two branches, one for each of the two descendant lineages

evolutionary lineage

the sequence of ancestral organisms leading to a particular taxon; represented by a branch in a phylogenic tree

sister taxa

groups of organisms that share an immediate common ancestor and hence are each other’s closest relatives

rooted

describing a phylogenic tree that contains a branch point representing the most recent common ancestor of all taxa in the tree

basal taxon

in a specified group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group

shared ancestral character

a character that is shared by members of a particular clade but 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. An outgroup is selected so that its members are closely related to the group of species being studied, but not as closely related as any study-group members are to each other

ingroup

A species or group of species whose evolutionary relationships are being examined in a given analysis

maximum parsimony

a principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explication that is constant with the facts

clade

a group of species that includes an ancestral species and all of its descendants

monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all of its descendants. A monophyletic taxon 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 descendants

polyphyletic

Pertaining to a group of taxa that includes distantly related organisms but does not include their most recent common ancestor

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 evolve atconstant rates

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

microevolution

evolutionary change below the species level; change in the allele frequencies in a population over generations

genetic variation

differences among individuals in the composition of their genes or other DNA sequences

phenotypic plasticity

the ability of an individual genotype that is capable of producing different phenotypes when exposed to different environmental conditions

neutral variation

genetic variation that does not provide a selective advantage or disadvantage

adaptive evolution

a process in which traits that enhance survival or reproduction tend to increase in frequency in a population over time

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 a 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 of their gametes

relative fitness

the contribution an individual makes to the gene pool of the next generation , relative to the contribution of other individuals 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 individuals with intermediate phenotypes

balancing selection

neutral selection that maintains two or more phenotypic forms in a population

heterozygote advantage

grater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool

gene pool

The aggregate of all copies of every type of allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population

population

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

Hardy-Weinberg Equilibrium

The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work, null hypothesis

allopathic speciation

the formation of new species in populations that are geographically isolated from one another

biological species concept

definition of a species as a 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

ecological species concept

definition of a species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment

hybrids

offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species

hybrid zone

A geographic region in which members of individuals from two different species meet and mate, producing at least some offspring of mixed ancestry

macroevolution

Evolutionary change above the species level. Examples of macroevolutionary change include the origin of a new group of organisms through a series of speciation events and the impact of mass extinction on the diversity of life and its subsequent recovery.

microevolution

Evolutionary change below the species level: change in the allele frequencies in a population over generations

morphological species concept

definition of a species in terms of measurable anatomical criteria

postzygotic barriers

a reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults

prezygotic barriers

a reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted

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.

reproductive isolation

the existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring

speciation

an evolutionary process in which one species splits into two or more species

adaptive radiation

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities

mass extinction

The elimination of a large number of species throughout Earth, the result of global environmental changes

Pangaea

the supercontinent that formed near the end of the Paleozoic era, when plate movements brought all the landmasses of life together

plate tectonics

the theory that the continents are part of great plates of Earth’s crust that float on hot, unyielding portion of the mantle. Movements in the mantle cause the continents to move slowly over time

radiometric dating

common techniques used to determine the age of a fossil, based on the decay of radioactive isotopes

heterochrony

evolutionary change in the timing or rate of an organism’s development

paedomorphisis

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

prokaryotes

an organism that has a prokaryotic cell: an informal term for an organism in either domain Bacteria or domain Archea

protocells

an abiotic precursor of a living cell that had a membrane-like structure that maintained an internal chemistry different form that of its surroundings

pathogens

an organism or virus that causes disease

ribozymes

an RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing

nucleoid

A non-membrane-enclosed region in a prokaryotic cell where its chromosomes is located

plasmids

A bacterial plasmid carrying genes that confer resistance to certain antibiotics.

transformation

The process by which a cell in culture acquires the ability to divide indefinitely, similar to the division of cancer cells. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer

transduction

A process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species, transduction results in horizontal gene transfer. See also signal transduction pathway

conjugation

In prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. When the two cells are members of different species, conjugation results in horizontal gene transfer

protists

An informal term applied to any eukaryote that is not a plant, animal, or fungus. Most protists are unicellular, though some are colonial or multicellular

endosymbiosis theory

The theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by host cells. The engulfed cell and its host cell then evolved into a single organism

endosymbiosis

A mutually beneficial relationship between two species in which one organism lives inside the cell or cells of another organism

secondary endosymbiosis

A process in eukaryotic evolution in which a heterotrophic eukaryotic cell engulfed a photosynthetic eukaryotic cell, which survived in a symbiotic relationship inside the heterotrophic cell