Evolution Unit Review

speciation

the origin of new species

microevolution

adaptations confined to a single gene pool

macroevolution

evolutionary change above the species level

species

a Latin word meaning "kind" or "appearance"

biological species concept

the accepted scientific definition of a species (produce viable, fertile offspring/cannot reproduce with other species)

reproductive isolation

the existence of biological factors that impede members to two species from producing viable, fertile hybrids

prezygotic barriers

impede mating between species or hinder fertilization of ova if members of different species attempt to mate

postzygotic barriers

if ovum fertilizes, prevents hybrid zygote from being viable or fertile

morphological species concept

characterizes a species by its body shape, size, and other structural features

paleontological species concept

focuses on morphologically discrete species known only from the fossil record

ecological species concept

views a species in terms of its role in a biological community

phylogenic species concept

states that a species is a set of organisms with a unique genetic history

allopatric speciation

gene flow is interupted when a population is divided into geographically isolated subpopulations; occurs after natural disaster

sympatric speciation

speciation takes place in geographically overlapping populations

polyploidy

a condition involving an extra set of chromosomes

autopolyploid

an individual with more than two chromosome sets all derived from a single species

allopolyploid

a fertile polyploid that is fertile with each other but cannot interbreed with either parental species

heterochrony

an evolutionary change in the rate or timing of developmental events

allometric growth

the proportioning that helps give a baby its specific form

paedomorphosis

condition caused by acceleration of reproductive development compared to somatic development; sexually mature stage of a species may retain body features that were juvenile structures in ancestral species

homeotic genes

determine basic features such as where a pair of wings and a pair of legs will develop on a bird

species selection

the species that endures the longest and generates the most new offspring species determine the direction of major evolutionary trends

phylogeny

the evolutionary history of a species or group of species

systematics

an analytical approach to understanding the diversity and relationships of organisms, both present day and extinct

molecular systematics

uses comparisons of DNA, RNA, and other molecules to infer evolutionary relationships between individual genes and entire genomes

fossil record

based on the sequence in which fossils have accumulated in such strata

analogy

similarity due to convergent evolution

homoplasies

analogous structures that have evolved independently

taxonomy

an order division of organisms into categories based on a set of characteristics used to assess similarities and differences

binomial

the scientific name of a species

genus

the first word of a binomial; second most specific category

specific epithet

second word of a binomial; most specific category

family

third most specific category

order

fourth most specific category

class

fifth most specific category

phylum

sixth most specific category

kingdom

seventh most specific category

domain

most general category

taxon

the general name for each category in the taxonomy

phylogenic tree

branching diagram used to depict hypotheses about evolutionary relationships

cladogram

a diagram depicting patterns of shared characteristics

clade

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

cladistics

the analysis of how species may be grouped

monophyletic grouping

a valid clade; consists of the ancestral species and all its descendants

paraphyletic grouping

consists of an ancestral species and some, but not all, of the descendants

polyphyletic grouping

consists of several species that lack a common ancestor

shared primitive character

a character that is shared beyond the the taxon we are trying to define

shared derived character

an evolutionary novelty unique to a particular clade

outgroup

a species or group of species closely related to the ingroup

ingroup

the various species we are studying

phylogram

diagram depicting relationships between species; the length of a branch reflects the number of changes that haven taken place in a particular DNA sequence in that lineage

ultrametric tree

diagram depicting the amount of chronological time that has occurred since the common ancestor lived; all of the branches are the same length

maximum parsimony

principle that states when determining which phylogenetic tree best reflects the true phylogeny, we should first investigate the simplest explanation that is consistent with the facts

maximum likelihood

the principle that states that given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events

orthologous genes

homologous genes that are passed in a straight line from one generation to the next but have ended up in different gene pools because of speciation

paralogous genes

result from gene duplication, so they are found in more than one copy in the same genome

molecular clock

a yardstick for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates

neutral theory

the theory that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian selection

horizontal gene transfer

genes are transferred from one genome to another through mechanisms such as transposable elements, and perhaps through fusions of different organisms

natural selection

the mechanism by which the many species of organisms presently inhabiting Earth are descendants of ancestral species that were different from the modern species

evolutionary adaptation

the result of natural selection; an accumulation of inherited characteristics that enhance organisms ability to survive and reproduce in specific environments

evolution

a change over time in the genetic composition of a population

fossils

remains or traces of organisms in the past

sedimentary rocks

the rocks where most fossils are found; formed from the sand and mud that settle to the bottom of seas, lakes, and marshes

paleontology

the study of fossils; largely developed by French scientist Georges Cuvier

catastrophism

the speculation that each boundary between stratum represents a catastrophe, such as a flood or drought, that destroyed many of the species living at that time

gradualism

the idea that profound change can take place through the cumulative effect of slow but continuous processes

uniformitarianism

the idea that the same geologic processes are operating today as in the past, and at the same rate; originally composed by Hutton, incorporated into more comprehensive theory by Lyell

descent with modification

the phrase Darwin used in most of book instead of evolution; he perceived a unity in life, with all organisms related through descent from an ancestor that lived in the remote past

artificial selection

the process in which humans modify other species over many generations by selecting and breeding individuals that possess desired traits

homology

similarity resulting from common ancestry

homologous structures

represent variations on a structural theme that was present in their common ancestor

vestigial organs

homologous structures of marginal, if any, importance to the organism

biogeography

the geographic distribution of species

endemic

found nowhere else in the world

population genetics

the study of how populations change genetically over time

modern synthesis

a comprehensive theory of evolution that integrated ideas from many other fields

population

a localized group of individuals that are capable of interbreeding and producing fertile offspring

gene pool

the aggregate of genes in a population at any one time

Hardy-Weinberg theorem

the theorem that states that the frequencies of alleles and genotypes in a population's gene pool remain constant from generation to generation, provided that only Mendelians segregation and recombination of alleles are at work.

Hardy-Weinberg equilibrium

describes a population in which the individuals not only donate gametes to the next generation at random, but also mate at random

mutations

changes in the nucleotide sequence of DNA

duplication

an important source of variation; occurs when an exact copy of a gene is made

genetic drift

unpredictable fluctuations from one generation to the next

bottleneck effect

caused by a sudden change in the environment, such as a fire or flood, which reduces the size of a population and therefore changes the gene pool to one that may no longer be reflective of the original gene pool

founder effect

caused by a few individuals becoming isolated from a larger population and establishing a new population whose gene pool is not reflective of the source population

gene flow

genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes

phenotypic polymorphism

a population displays this for a character if two or more distinct morphs are each represented in high enough frequencies to be readily noticeable

genetic polymorphisms

polymorphisms at the genetic level

average heterozygosity

measured as the average percent of these loci that are heterozygous

geographic variation

differences between the gene pools of separate populations or population subgroups; most species exhibit this

fitness

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

relative fitness

the contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus

directional selection

most common when a population's environment changes or when members of a population migrate to a new habitat with different environmental conditions than their former one

disruptive selection

occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotypes

stabilizing selection

acts against extreme phenotypes and favors intermediate variants

balancing selection

occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population

balanced polymorphism

the state when stable frequencies of two or more phenotypic forms in a population are maintained

heterozygote advantage

the idea that states that if individuals who are heterozygous at a particular gene locus have greater fitness than the homozygotes, natural selection will tend to maintain two or more alleles at that locus

frequency-dependent selection

the fitness of any one morph declines if it becomes too common in the population