Honors Bio - Chapters 13 - 15 MEGA

adaptation

An inherited character that enhances an organism's ability to survive and reproduce in a particular environment.

artificial selection

The selective breeding of domesticated plants and animals to promote the occurrence of desirable traits.

balancing selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population.

bottleneck effect

Genetic drift resulting from a drastic reduction in population size. Typically, the surviving population is no longer genetically representative of the original population.

directional selection

Natural selection in which individuals at one end of the phenotypic range survive and reproduce more successfully than do other individuals.

disruptive selection

Natural selection in which individuals on both extremes of a phenotypic range are favored over intermediate phenotypes.

evolution

Descent with modification; the idea that living species are descendants of ancestral species that were different from present-day ones; also, the genetic changes in a population from generation to generation.

evolutionary tree

A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms.

fossil

A preserved remnant or impression of an organism.

fossil record

The chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool is not reflective of that of the original population.

gene flow

The transfer of alleles from one population to another as a result of the movement of individuals or their gametes.

gene pool

All copies of every type of allele at every locus in all members of the population.

genetic drift

A change in the gene pool of a population due to chance. Effects are most pronounced in small populations.

Hardy-Weinberg equilibrium

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

heterozygote advantage

Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in gene pools.

homologous structures

Structures in different species that are similar because of common ancestry.

homology

Similarity in characters resulting from a shared ancestry.

microevolution

A change in a population's gene pool over generations.

molecular biology

The study of biological structures, functions, and heredity at the molecular level.

mutation

A change in the genetic information of a cell; the ultimate source of genetic diversity. A mutation also can occur in the DNA or RNA of a virus.

natural selection

A process in which individuals with certain inherited traits are more likely to survive and reproduce than are individuals that do not have those traits.

paleontologist

A scientist who studies fossils.

population

A group of individuals belonging to one species and living in the same geographic area.

relative fitness

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.

sexual dimorphism

Marked differences between the secondary sex characteristics of males and females.

sexual selection

A form of natural selection in which individuals with certain inherited traits are more likely than other individuals to obtain mates.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

stratum (plural, strata)

Rock layer formed when a new layer of sediment covers an older one and compresses it.

theory

A widely accepted explanatory idea that is broader in scope than a hypothesis, generates new hypotheses, and is supported by a large body of evidence.

vestigial structure

A feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors.

adaptive radiation

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

allopatric 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

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.

hybrid

Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species; an offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes.

hybrid zone

A geographic region in which members of different species meet and mate, producing at least some hybrid offspring.

morphological species concept

A definition of species in terms of measurable anatomical criteria.

phylogenetic species concept

A definition of species as the smallest group of individuals that shares a common ancestor, forming one branch on the tree of life.

polyploid

An organism that has more than two complete sets of chromosomes as a result of an accident of cell division.

postzygotic barriers

A reproductive barrier that prevents hybrid zygotes produce by two different species from developing into viable, fertile adults. Includes reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

prezygotic barriers

A reproductive barrier that impedes mating between species or hinders fertilization if mating between two species is attempted. Includes temporal, habitat, behavioral, mechanical, and gametic isolation.

punctuated equilibria

In the fossil record, long periods in which a species undergoes little or no morphological change (equilibria), interrupted (punctuated) 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

The evolution of a new species.

species

A group of populations whose members have the potential to interbreed and produce viable, fertile offspring.

sympatric speciation

The formation of new species in populations that live in the same geographic area.

analogy

The similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.

Archaea

One of two prokaryotic domains of life, the other being Bacteria.

Bacteria

One of two prokaryotic domains of life, the other being Archaea.

binomial

The two-part format for naming a species, consisting of a genus and specific epithet; for example, Homo sapiens.

biogeography

The study of the past and present distribution of organisms.

clade

A group of species that includes an ancestral species and all its descendants.

cladistics

An approach to systematics in which common descent is the primary criterion used to classify organisms by placing them into groups called clades.

class

In Linnaean classification, the taxonomic category above order.

convergent evolution

The evolution of similar features in different evolutionary lineages, which can result from living in very similar environments.

domain

A taxonomic category above the kingdom level. The three ____ of life are Archaea, Bacteria, and Eukarya.

Eukarya

Domain of life that includes all eukaryotic organisms.

evo-devo

Evolutionary developmental biology; the field of biology that combines evolutionary biology with developmental biology.

family

In Linnaean classification, the taxonomic category above genus.

genus

In classification, the taxonomic category above species; the first part of a species' binomial; for example, Homo.

geologic record

A time scale established by geologists that divides Earth's history into four eons—Hadean, Archaean, Proterozoic, and Phanerozoic—and further subdivides it into eras, periods, and epochs.

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.

ingroup

In a cladistic study of evolutionary relationships, the group of taxa whose evolutionary relationships are being determined. See also outgroup.

kingdom

In classification, the broad taxonomic category above phylum.

macroevolution

Evolutionary change above the species level, encompassing the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery.

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 at constant rates.

molecular systematics

A scientific discipline that uses nucleic acids or other molecules in different species to infer evolutionary relationships.

monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all its descendants, equivalent to a clade.

order

In Linnaean classification, the taxonomic category above family.

outgroup

In a cladistic study, a taxon or group of taxa known to have diverged before the lineage that contains the group of species being studied. See also ingroup.

paedomorphosis

The retention in an adult of juvenile features of its evolutionary ancestors.

Pangaea

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

parsimony

In scientific studies, the search for the least complex explanation for an observed phenomenon.

phylogenetic tree

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

phylogeny

The evolutionary history of a species or group of related species.

phylum (plural, phyla)

In Linnaean classification, the taxonomic category above class.

plate tectonics

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

radiometric dating

A method for determining the absolute ages of fossils and rocks, based on the half-life of radioactive isotopes.

ribozyme

An RNA molecule that functions as an enzyme.

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.

stromatolite

Layered rock that results from the activities of prokaryotes that bind thin films of sediment together.

systematics

A scientific discipline focused on classifying organisms and determining their evolutionary relationships.

taxon

A named taxonomic unit at any given level of classification.

taxonomy

The scientific discipline concerned with naming and classifying the diverse forms of life.

three-domain system

A system of taxonomic classification based on three basic groups: Bacteria, Archaea, and Eukarya.

phenotype

The expressed traits of an organism.

genotype

The genetic makeup of an organism.

reduced hybrid fertility

a lower potential to survive for organisms whose parents have incompatible genetics, mostly because these parents mated despite being different species

reduced hybrid viability

Offspring that have a lower rate of survival than the parent species. This reduces the likelihood of the hybrid offspring surviving to sexual maturity.

gamete isolation

A type of prezygotic barrier where the gametes (egg and sperm) come into contact, but no fertilization takes place.

mechanical isolation

Includes any physical barrier that prevents mating. Organisms may attempt to mate, but due to physical differences in the genitalia, mating does not occur. Is the result of the evolution of genitalia in specific species that prevents them from mating with others. 

behavioral isolation

Occurs when mismatches in mating traits (signals and/or preferences) prevent mating between two species/populations.

temporal isolation

A type of reproductive isolation mechanism among sexual organisms in which the differences in the timing of critical reproductive events prevent members of closely related species, which could otherwise breed with one another, from mating and producing hybrid offspring.

habitat isolation

a form of reproductive isolation in which reproduction between two populations (generally two species that are capable of interbreeding) is restricted because each population occupies a different habitat.

hybrid breakdown

A type of reproductive failure that appears after the F2 generation of crosses between different species or subspecies. It is caused by incompatibility between interacting genes.