Change in the properties of groups of organisms over the course of generations
Groups of organisms undergo descent with modification. may become subdivided so are derived from a common ancestral population.
before Darwin. Believed that variation is accidental imperfection. Each species has been created individually by God. (special creation)
classified plants and animals hoping to discover the pattern of the creation
same processes operated in the past as in the present, and that the observations of geology should therefore be explained by causes that we can now observe.
proposed that each species originated individually by spontaneous generation from non living matter, starting at the bottom of the chain of being. Species originated at different times so we now see a hierarchy of species because they differ in age.
Inheritance of acquired characteristics
species differ from one another b/c they have different needs. created by Lamark.
Two major thesis in Origin of Species
Descent with modification
Descent with modification
all species, living and extinct, have descended, without interruption, from one or a few original forms of life.
inheritance is based not on blending fluids but on particles that pass unaltered from generation to generation- so that variation can persist. Thought of by Mendel .
evolutionary synthesis or modern synthesis
mathematical theory of population genetics, which showed that mutation and natural selection together cause adaptive evolution: mutation is not an alternative to natural selection, but is rather its raw material
mutation, recombination, natural selection, and other processes operating within species
origin of new species and for the major, long-term features of evolution
analyses of the processes and history of change in genes.
Neutral theory of molecular evolution
most of the evolution of DNA sequences occurs by genetic drift rather than by natural selection, but it provides a foundation for detecting effects of natural selection on DNA sequences. by Kimura.
concerned with variation and evolution in multiple genes or even entire genomes.
Evolutionary Developmental Biology
understanding how the evolution of developmental processes underlies the evolution of morphological features at all levels, from cells to whole organisms.
opposes the teaching of evolution in public schools, or at least demands "equal time" for creationist beliefs.
supposition that what is natural is good. describes how the world is, not how it should be. NOT GOOD!
traits that have been shaped by natural selection
change in the properties of groups of organisms over the course of generations. the development ontogeny is not considered evolution: individual organisms do not evolve
mature coherent body of interconnected statements, based on reasoning and evidence that explain some aspect of nature-usually many aspects.
genealogical relationships among organisms. important foundation for understanding many aspects of evolutionary history such as pathways by which various characteristics have evolved.
Three empires of life
Eucarya (animals, fungi, plants, etc)
Archaea (heat releated organisms etc)
classification and naming of organisms
phylogenetic analysis and taxonomy
system of two-part names consisting of a genus and a specific epithet
groups nested within larger groups ie) genera nested within families.
levels of classification such as kingdom, phylum, class, order, family, genus, and species.
particular group of organisms assigned to a categorical rank
closely adjacent twigs represent living species derived only recently from their common ancestors, whereas twigs on different branches represent species derived from more ancient common ancestors.
characteristics of an organism may differ among organisms Phenotypic characters that have proved useful for phylogenetic analyses of various organisms have included not only external but internal morphological features but also differences in behavior, cell structure, biochemistry, and chromosome structure.
monophyletic group; clade
set of species derived from any one common ancestor.
shared derived character states
degree of relationship between species
determined by relative recency of common ancestry, not similarity
derived character states that are restricted to a single lineage. do not provide any evidence about its relationship to other lineages.
character changed only once across the whole phylogeny hence all the taxa sharing a character state inherited it without change from their common ancestor. A character may be homologous among species but a given character state may not be. May differ so greatly among taxa b/c they have evolved as its function has changed
a character state that has independently evolved two or more times, and so does not have a unique origin.
independent origin of a derived character state in two or more taxa.
constitute a return from an "advanced" or derived character state to a more "primitive" or ancestral state
taxa may be similar because they share
1) uniquely derived character states
2) ancestral character states
3) homoplasious character states, and that only the similarity due to uniquely derived character states provides evidence for the clades, the nested monophyletic groups, that make up a phylogenetic tree.
principle, dating at least from the 14th century that the simplest explanation, requiring the fewest undocumented assumptions, should be preferred over more complicated hypotheses that require more assumptions for which evidence is lacking
best estimate of true phylogeny
one that requires us to postulate the fewest evolutionary changes.
evolutionary changes tha we must suppose occurred more than once
best phlogenetic hypothesis
one that requires us to postulate the fewest homoplasious changes
monophyletic group whcih we are confident are successively more distantly related.
monophyletic set of species who relationships we wish to infer
groups derived from a common ancestor that is not shared with any other groups.
two kinds of data yield estimates of phylogeny
DNA sequences evolve and diverge at a constant rate (NOT TRUE OF MORPHOLOGICAL FEATURES) D=2rt D is proportion of base pairs that differ between the two sequences, r is the rate of divergence per base pair per Myr, t is the time
how to estimate molecular evolution
calculate the number of differences (base pairs) that have accrued among pairs of species among pairs of species since their common ancestor by parsimoniously plotting on our estimated phylogeny where each change took place
each lineage branches into two others
what is needed to estimate the average rate of base pair substitution in any lineage
estimate of the absolute time of divergence
relative rate test
one way to determine whether sequence evolution conforms to a molecular clock. has shown that rates of sequence evolution are often quite similar among taxa that are fairly closely related, but may differ considerably among distantly related taxa.
variant DNA sequences of a gene. One haplotype gives rise to another by mutation.
gene tree/ gene genealogy
phylogeny of genes
unrooted gene tree
sequences that differ least have the closest ancestor-descendant relationship; that the most closely related haplotypes are connected to each other by the smallest possible number of mutations. ie) 7-6-5-4-1-2-3
unrooted means that we do not know what the direction of evolution was
difficulties in phylogenetic analysis
scoring characters can be hard-deciding how many independent characters there are
homoplasy is very common
process of evolution often erase the traces of prior evolutionary history
some lineages diverge so rapidly that there is little chance for the ancestors of each monophyletic group to evolve distinctive synapomorphies.
accurately estimated gene tree may imply the wrong species phylogeny
relationships among closely related species may be obscured by low level of interbreeding btwn species
evolutionary radiation/ adaptive radiation
burst of divergence of many lineges during a short period. lineages have often acquired different adaptations. lineages that are modified for different ways of life, and the evolutionary radiation. most common pattern of long-term evolution usually do not show a directional trend in any one direction.
haplotypes may become fixed, by chance, in the three species in such a way that the most closely related species do not inherit the same haplotype.
horizontal (lateral) gene transfer
incorporates just a few genes of one species into the genome of another species.
patterns of evolution
two major features of evolution
branching of a lineage into two or more descendant lines
evolutionary change of various characteristics in each of the descendants
set of all known descendants from a single common ancestor
unrelated lineages that are more closely related to species that are placed in other taxa
group that is monophyletic except that some descendants of the common ancestor have been placed in other taxa. Usually lack species that have been placed in another taxon in order to emphasize their distinctive adaptations.
greatly influenced systematics, first by proposing cladistics,
a method of discovering the real branching pattern of evolutionary history criteria for classification.
extinct group of species that has given rise to a crown group Any name for the stem group that excludes the crown group will designate a paraphyletic taxon-a unsatisfactory element in classification
later group with distinctive derived characters
criteria for hypothesizing homology of anatomical characters
correspondence of position relative to other parts of the body and correspondence of structure.
distribution on a phyogenetic tree
independent evolution of character or character state in different taxa-includes convergent evolution and evolutionary reversal .
similar features are formed by different developmental pathways
involves similar developmental modifications that evolved independently
a return from an advanced or derived character state to a more primitive or ancestral state.
complex characteristics, once lost, are unlikely to be regained--> proven wrong by evolutionary reversal
adaptations by different lineages to similar environmental conditions. A correlation between a particular homoplasious character in different groups and a feature of those organisms' environment or niche is often the best initial evidence of the feature's adaptive significance
condition in which features of one species have specifically evolved to resemble those of another species, provides especially interesting example of convergent evolution. defense against predators
retained with little or no change over long periods among the many descendants of an ancestor
one of most important principles of evolutions: a species evolves not as a whole but piecemeal: many of its features evolve quasi-independently every species is a mosaic of plesiomorphic and apomorphic characteristics. Because of mosaic evolution it is inaccurate or even wrong toconsider one living speices more "advanced" than another.
ancestral or primitive characteristics
derived or advanced characteristics
evolution proceeds by SMALL SUCCESSIVE CHANGES
evolution proceeds by small successive changes rather than by LARGE LEAPS
Von Baer's Law
features common to a more inclusive taxon often appear in ontogeny before the specific characters of lower-level taxa.
reinterpreted such patterns to mean that ontogeny recapitulates phylogeny. the development of ontogeny repeats the evolutionary history of the adult forms of its ancestors. he supposed that by studying embryology, one could read a species' phylogenetic history, and therefore infer directly phlogenetic relationships among organisms.--> known as biogenetic law.
acquisition of distinct identities by such units. important basis for mosaic evolution
structures that are arrayed along the body axis (vertebrae)
structures that are not arrayed along the body axis
an evolutionary change in the timing or rate of developmental events. global heterochronic changes are illustrated by cases in which the time of development of most somatic features is altered relative to the time of maturation of the gonads
those other than the gonads and related reproductive structures.
such evolution of a more juvenilized morphology of the reproductive adult. Can be caused by reducing neoteny or by progenesis
growth rate of somatic characters
cessation of growth at an earlier age
evolution of delayed maturity may result in reproduction at a larger size, associated with the extended development of "hyper-adult" features . q
Allometric growth, Allometry
differential rate of growth of different parts or dimensions of an organism during its ontogeny. Changes in rates of allometric growth of individual characters appear to have played an extremely important role in evolution.
y=bx^a y and x are two measurements such as the height and width of a tooth or the size of the head and the body. a describes their relative growth rates. if a=1-> isometic if a >1 positive allometry a<1 negative
two structures or dimensions increase at the same rate and shape does not change
evolutionary change in the position within an organism at which a phenotypic character is expressed.
repeated changes of a character in the same direction, either within a single lineage or, often, in many lineages independently.
measure in picograms of DNA varies ore than tenfold among species of salamanders and about twofold even between species in the same genus.
mutiational even by which a new gene arises as a copy of a preexisting gene so that a single gene locus in a n ancestor is represented by two loci in the descendant.
the genes that diverged from a common ancestral gene by phylogenetic splitting at the organismal level
genes that originated from a common ancestral gene duplication
entire nuclear genome is duplicated occurs commonly in plants and occasionally in animals.
plays a major role in the embryonic development of animals, is represented by one set of genes in non vertebrate chordates, four sets in most vertebrates, and seven sets in teleost fishes.
two themes the fossil record provides evidence for
phenotypic transformations in particular lineages
changes in biological diversity over time
new crust formed at mid-oceanic ridges. only this rock can be dated radiometrically,
formed by the deposition and solidification of sediments, which are usually formed either by the breakdown of older rocks or by precipitation of minerals from water must be dated by bracketing it between younger and older igneous formations.
under high temperature and pressure, both igneous and sedimentary rocks are altered and form metamorphic rocks.
theoretical mechanism for continental drift. The lithosphere, the solid layer of the earth bearing both the continents and the crust below the oceans, consists of 8 major and a number of minor plates that move over the denser, more plastic asthenosphere.
measures thedecay of certain radioactive elements in minerals that form in igneous rock.
layers of sediment deposited at different times. often contain distinctive fossils of species that persisted for a short time and are thus the signatures of the age in which they lived Different strata have different characteristics
marked by the first appeareance of diverse animals divided into three eras, each of which is divided into periods
change in a characteristic within a single, unbranching lineage characters tend to change gradually
multple lineages often evolve through grades
abrupt appearance of clsely related species, not to higher taxa. refer to both a pattern of change in the fossil reccord and a hypothesis about evolutionary processes
traditional notion of slow incremental change
detailed fossil record of abundant shell-bearing protists called foraminiferans
A unit of geologic time that is a division of a period. A notable event that marks the beginning of such a perio
he longest division of geologic time, made up of one or more periods.
An interval regarded as a distinct evolutionary or developmental phas
The theory that speciation occurs in spurts of major genetic alterations that punctuate long periods of little change.
long period in which species exhibit little or not detectable phenotypic change, interrupted by traditional notion of slow, incremental phenotypic change. ie) changes in the molar teeth of a lineage of grass-feeding voles.
long period in which species exhibit little or not detectable phenotypic change, interrupted by rapid shits from one such "equilibrium" state to another; that is "punctuated" by rapid change.
Eldredge and Gould hypothesis
characters evolve primarily in concert with true speciation-that is the branching of an ancestral species into two species. Founder-effect speciation or peripatric speciation.
fossil record shows that characters may evolve between long0stable states in populations that do not undergo speciation. This pattern--> punctuated gradualism is illustrated by the detailed fossil record of abundant shell-bearing protists called foraminiferans.
measure of the amount of variation within a population.
most difficult problem in accounting for the origin of life
in known living systems, only nucleic acids replicate, but their replication requires the action of proteins that are encoded by the nucleic acids.
simple organic molecules
building blocks of complex organic molecules, have been found in space and cane be produced by abiotic chemical reactions.
polymerization may have been facilitated by..
absorption to clay particles or by concentration caused by evaporation.
what else could occur after replication originated
prebiotic evolution by natural selection
about the first genes
need not have had any particular base pair sequence. thus there is no force to the argument, that the assembly of a particular nucleic acid sequence is extremely improbable.
Archean, prior to 2.5 billion years ago, and the Proterozoic, from 2.5 billion to 542 Mya
three empires or domains
Eucarya (all eukaryote organisms) and two groups of prokaryotes the Archaea and Bacteria. For 2 billion years the two prokaryotic empires were the only life on Earth.
eukaryotes distiguished by
cytoskeleton, a nucleus with multiple chromosomes and a miotic spindle, and a cell membrane rather than a rigid cell wall. Most eukaryotes undergo meiosis the basis oh highly organized recombination and sexual reproduction.
evolution of multicellularity
evolved because of the advantage of "division of labor" between different cell types with different functions. The oldest fossils of multicellular animals are about 575 Myr old.
Began with the Cambrian period then almost all the modern phyla and classes of skeletonized marine animals, as well as many extinct groups, appeared in the fossil recored. this diversification is generally called the cambrian explosion.
different body plans known in animals apparently evolved during the Cambrian-perhaps the time of the most dramatic adaptive radiation in the history of life.
between Ordovician to Devonian. (488-354 Mya)
Carboniferous-Permian (359-251 Mya)
Divided into the Triassic (251-200 Mya) Jurassic (200-145) and Cretaceous (145-65.5 Mya) age of reptiles.
sing world continent
southern continent during Mesozoic life
nothern continent during Mesozoic life
mass extinction periods
end-Permian mass extinction: the most massive extinction even in the history of the Earth so far.
end of Triassic
end of the Cretaceious-best known mass extinction (K/t extinction)
floweering plants first appeared in the early creaceous period.
one of the most diverse groups of amniotes. One majorlineage is the lepidosuromorphs, includes the lizards antoher is the archosauromorph, which dinosaurs evolved from
give rise to the terapsids sometimes called mammal-like reptiles, which flourished until the middle Jurassic
six epochs--> Paleocene through Pleistocene. At beginning of Cenozoic Gondwana broke up into the separate island continents of South America, Africa, India, and Antarctica plus Australia. Sometimes called the age of mammals
the geographic distribution of almost everry species is limited to some extent, and many higher taxa are likewise restricted to a particular geographic region.
Palearctic (temperate and tropical Eurasia and northern Africa) Nearctice (North America) and Neotropical (sound and central America) and Ethiopian (sub-Saharan Africa) and Oriental (India and Southeast Asia) and Australian (Australia, New Guinea, New Zealand, and nearby islands)
separates islands, that despite their close proximity and similar climate, differ greatly in their fauna. Assigned to two different bio geographic realms: the Oriental and the Australian.
Inhabited by many higher taxa that are much more diverse in that realm than elsewhere, or are even restricted to that realm
taxa whose distributions have gaps. typically have different representatives in each area they occupy.
movement of individuals. two kinds: Range expansion (moveent across expanses of more or less continuous favorable habitat) jump dispersal (movement across a barrier)
separation of population of a widespread species by barriers arising from changes in geology, climate, or habitat. The separated populations diverge and they often become different subspecies, species, or higher taxa.
foundation of most modern studies of historical biogeography. Use a Parsimony approach to reconstruct the geographic distributions of ancestors from data on the distributions of living taxa.
Ronquist's method most fully accounts for the importance of dispersal and is therefore most biologically realistic. assumes that vicariance is the "null hypothesis"
Certain taxa that originated elsewhere.
taxa that evolved within the region.
description and analysis of the processes that govern the geographic distribution of lineages of genes, especially within species and among closely related species. Relies strongly on phylogenetic analysis of variant genes within species on inferring gene genalogies.
archaic sapiens populations in Africa and eurasia all evolved into modern sapiens, with gene flow spreading modern traits among the various populations.
after archaic sapiens spread from Africa to Asia and Europe, modern sapiens evolved from archaic sapiens in Africa, spread throughout the world in a second expansion and replaced the populations of archaic sapiens without interbreeding with them to any substantial extent.
fundamental ecological niche
a population as the set of all those environmental conditions in which a species can maintain a stable population size.
realized ecological niche`
even within the potential niche space the range of environmental conditions that a species actually occupies (realized e.n.O may be further restricted if the species is excluded by competitors or predators
phylogenetic nice conservatism
has been described with respect to both abiotic and biotic factors. Related species often have similar ecological requirements, presumably derived from their common ancestor.
consequences of niche conservatism
contributes to our understanding of the geographic distributions of many clades
underlies the observation that many species shifted their geographic ranges during the Pleistocene, rather than adapting in situ to changes in climate
biological diversity can be studied from the complementary perspectives of ecology and evolutionary history.
pull of the Recent
because the more recently a taxon arose, the ore likely it is to still be extant, diversity will seem to increase as we approach the present BIAS!!! can be reduced by counting only fossil occurrences of each taxon and not listing it for time intervals between its last fossil occurrence and the Recent.
taxons that are recorded from only a single geological stage, even though it lived longer than that. these make up a higher proportion of taxa as the completeness of sampling decreases and therefore bias the sample. they can create a spurious correlation between rates of origination and extinction because they appear to originate and become extinct in the same time interval
distinction is often made between episodes during which exceptionally high numbers of taxa become extinct
period of so-called normal numbers of taxa become extinct
characteristics to determine extinction rates of families
degree of ecological specialization
Red queen hypothesis
each species has to run (evolve) as fast as possible just to stay in the same place (survive) because its competitors, predators and parasites also continue to evolve.
ΔN/Δt=SN-EN or ΔN/Δt=RN R=(S-E) and is the per capita rate of increase.
number of taxa (or of a population of organisms)
dN/dt=rN and Nt=N0ert
competition for food or space, cause the per capita birth rate to decline, and/or the death rate to increase, with population density, so that population growth slows down and the population density may reach a stable equilibrium.
might reduce origination rates or increase extinction rates as the number of species increases.
density-dependant population growth is shown by this. growth in number of species may be expressd as
ΔN/Δt=r0N(K-N/K) R is the per capita rate of increase when the number of species is very low.
changes that have altered conditions for organisms
changes have occured in the physical environment, including changes in climate and in the configuration of land and sea
taxa that became dominant after mass extinctions were different from thosethat prevailed before and would be expectd to attain a different equilibrium level of diversity because of new patters of competition and other interactions.
taxa have evolved to use new resources and habitats, changing the overall number of species that the planet's resources can support
later group may have caused the extinction of the earlier group by competition
extinction of the incumbent taxon may then have vacated ecological "niche space" permitting the second taxon to radiate. been more common than competitive displacement.
an adaptation that enables an organism to occupy a substantially new ecological niche, often by using a novel resource or habitat. adaptation has enabled the diversification.
roughly equivalent to a set of adaptive zones.
Replicated sister-group comparison
if the convergently evolved character is consistently associated with high diversity we would have support for the hypothesis that it has caused a higher rate of diversification
degree to which the world's biota is partitioned among geographic regions. a faunal or floral province is a region containing high numbers of distinctive localized taxa
single long tightly coiled DNA molecule different portions of which constitute different genes, together with histone proteins
a sequence of DNA that is transcribed into RNA together with untranscribed regions that play roles in regulating its transcription.
chromosome site occupied by a particular gene but it is often used to refer to the gene itself.
one strand of a protein-encoding gene is transcribed into RNA
enhancers and repressors
untranscribed sequences. tro which regulatory proteins prudued by other genes bind.
coding regions of a transcribed sequence of a gene
noncoding regions seperates most genes.
the mature mRNA corresponds to a variable number of the exons, can result in several proteins being encoded by a single gene.
triplet of bases, the third position in a codon is the most degenerate, the second position is least degenerate- a substitution of one base for another in the second position usually results in an amino acid substitution in a protein.
repetitive elements that include repeated sequences of a few base pairs each.
repeated sequences offten occur as tandem repeats
the production of copies that become inserted into new positions in the genome
DNA sequences that are capable of transposition
groups of genes that are similar in sequence and often have related functions. examples of repeated sequences that have diversifiedover time.
sequences that resemble the functional genes but that differ at several base pair sites and are not transcribed because they have internal stop codons
those that originated by reverse transcription from an mRNA message into a DNA sequence that lacked introns and later underwent silencing and further base pair changes.
a particular DNA sequence that differs by one or more mutations from homologous sequence
detectable mutations that geneticists use to recognize specific regions of chromosomes or genes.
base pair substitutions
simplest mutation are alteratins of a s single base pair
mutations that maps to a single gene locus. this term is often restricted to single base pair substitutions.
substitution of a purine for a purine (A<--> T) and same with pyrimadine
are substiutions of purines for pyrimidines or vice verca
many mutatins in coding regions that have no effect on the functional properties of the polypeptide or protein and thus no effect on thephenotype or they may have substantial consequences.
happen because of insertions or deletions usually nonfunctional though exceptions to this generalization are known.
result in amino acid substituions they may have little or no effect on the functional properties of the polypeptide or protein and thus no effect on the phenotype or they may have substantial consequences.
process that alters the number of short repeats in microsatelites.
when homologous DNA sequence differ at two or more base pairs intragenic recombination between them can generate new DNA sequences just as crossng over between genes generrates new gene combinations.
unequal crossing over
can occur between two homologous sequences or chromosomes that are not perfectly aligned. it then results in Tandem duplications on one recombination product and a deletion on the other.
carry a gene for the enzyme reverse transcriptase first transcribe into RNA which then is reverse-transcribed into a DNA copy that is inserted into the genomeins
encode only enzymes that cause transpostion
encode other functional genes as well as enzymes that cause transposition
cDNA copies of RNA resemble the exoons of an ancestral gene located elsewhere in the genome but they lack controlregions and introns.
normal genes. benefical mutations.
refers to the repeated origin of a particular mutation and the rate at whcich a particular mutation occurs is typically measure in terms of recurrent mutation: the number of independent origins per gene copy per generation or per unit time
mutation of a mutant allele back to the allele from which it arose. usually occur at a much lower rate than forward mutations presumably because many more substitutions can impair gene function than forward mutations.
most phenotypic characters are this. it is based on several or many different genetic loci.
increase variation in a population caused bu new mutations in each generations.
describes the effect of an allele on a phenotypic character when it is paired with another allele in the heterozygous condition
mutation that affect more than one character
description of its complement of chromosomes: their number, size, shape, and internal arrangement. It is important to bear in mind that the loss of a whole chromosome, or a mjor part of a chromosome usually reduces the viabilty of a gamete or an organism becaue of the loss of genes.
unbalanced chromosome complement a gamete or organism often inviable or fails to develop properly
arisen polyploids have arisen by the union of unreduced gametes of the same species these organisms
organimsm which have arisen by hybridization between closely related species.
by breakage and reunion two nonhomologous chromosomes may exchange segments resulting in this
two nonhomologous acrocentric chromosomes undergo reciprocal translocation newer the ecentromeres so that they are joined into a metacentric chromosome
phenotypic differences that are not based on DNA sequence differences are transmitted among generations of dividing cells in multicellular organisms and also, sometimes, from parents to offspring
members of the population do not mate at random-the genotype frequencies may depart from the ratios
migration 0r gene flow
mating among individuals from different populations
presence in a population of two or more variant rarer allels has a frequency greater than .01.
locus or character that is not polymorphic.
discrete genetic polymophisms in phenotypic traits such as pin or thrum flowers, are much less common than slight differences among individuals such as variation in the number of bristles on the abdomen in weigh or nose shape among humans
due to variation at several or many loci each of which contributes to the variation in phenotype.
used to detect genetic variation in a character.
provided many insights into the mechanisms of evolution
distinct forms or populations have overlapping geographic distributions such that they occupy the same area and can frequently encounter each other
populations with adjacent but nonoverlapping geographic ranges that come into contact
populations with separated distriubtions su
a region in which genetically distinct parapatric forms interbreed.
body size in the hit-tailed deer increases with increasing latitude over much of North America apattern that is so common in mammals and birds
a gradual change in a character or in allele ffrequencies over geographic distance
phenotypes that are associated with a particular habitat often in a patchy mosaic pattern
measures how likely it is that gene copies taken from two populations will be diffeerent alleles, given data on allele frequencies.
single nucleotide polymorphisms
single-site nucleotide variations at more than 3 million sites in the genome.
random fluctuations in allele frequencies can esult in the replacement of old alleles by new ones
small independent populations
ensemble of such populations may be termed
may increase by chance in some demes from one generation to the next it may decrease in other demes. allele frequencies may vary among the demes.
effective population size
number of individuals in an ideal population in which the rate of genetic drift would be the same as it is in the actual population
new population rapidly grows to a large size, allele frequencies will probably not be greatly altered from those in the source population .
restrictions in size through which populations may pass
occurs when a new population is established by a small number of colonists, or founders-sometimes as few asa single mating pair.
neutral theory of molecular evolution
although a small minority of mutaion in DNA or protein sequences are advantageous and are fixed by natural selection, and although many mutations are disadvantageous and are fixed by natural selection, the great majority of those mutations that are fixed are effectively neutral with respect to fitness and are fixed by genetic drift.
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