CH 19, 20, 21, 22, 23 Evolution

Why can't natural selection fashion perfect organisms?

1. can only act on existing variations (favors fittest phenotype which may not be ideal phenotype) 2. it's limited by historical constraints (doesn't scrape ancestral anatomy) 3. adaptations often compromises 4. chance, natural selection and environment interact (chance events affect subsequent evolutionary history of population, not all alleles in founding gene pool suited for new environment can change unpredictably)

artificial selection similar process in nature

1. members of population vary in inherited traits- individuals who inherit traits have a higher probability of surviving and reproducing 2. all species can produce more offsprings than evolution can support, offsprings fail to survive/reproduce - unequal ability of individual to survive and reproduce lead to accumulation of favorable traits in population over generations

explain the process of Natural Selection

1. progress of editing, not a creative mechanism (drug doesn't create pathogen resistant, select for resistant individual already present in population) 2. depends on time and place

artifical selection

1st mechanisms of natural selection to explain evolution, humans have modified other species over many generations by selecting and breeding individuals that possess desired traits, result in crops, livestock animals and pets with little resemblance to wild ancestors

homology

2nd evidence of evolution, related species can have characteristics that have underlying similarity - function differently, similarity resulting from shared ancestry, closely related species share similar structures

maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts, Occam, computer programs using parsimony examine large number of possible trees and identify those that require fewest evolutionary changes

Ingroup

A species or group of species whose evolutionary relationships we seek to determine/analyze We can compare ingroups with other ingroups or outgroups we can determine which characters are derived at various branches parts of vertical evolution

Macroevolution

Evolutionary change above the species level. (ex: 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)

Phylogeny

Evolutionary history of a species or group of species.

Comparing DNA molecules/alignment

After DNA sequenced (closely related sequences differ less) ex: noncoding DNA sequences in early gene in very similar species except 1st based deleted in one segment, computer programs help identify identical matching by testing possible alignments for comparable DNA with different lengths

What is used to distinguish homology and analogy?

Corroborative similarities, fossil evidence and complexity of characters being compared ( more elements similar - evolutionary common ancestor) ex: human and chimp skulls match, such complex structures same details different origins, most likely genes involved in development of sells inherited from common ancestor if two organisms share many positions of nucleotide sequence homologous

Reproductive isolation

Crucial to formation of new species, existence of bio factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offsprings

what are the three main domains?

Bacteria, Archaea, Eukarya, higher taxonomic level than kingdom level, three domains support by studies of researchers support 1st major split in life history bacteria diverge, if true euk and archaea more closely related (based on rRNA) if look at dif genes euk and bacteria more closesly related

Binomial

The two-part scientific name of a species, Linnaeus, 1st letter capitalized italicized Genus- first part of binomial, genera to which species belongs to Specific epithet- second part of binomial, unique for species within genus

stabilizing selection

acts against both extreme phenotypes and favors intermediate variants, reduces variation and maintains status quo for phenotypic characters (ex: birthweight)

If genes have existed for so long how can we explain increase in diversity?

adaptive evolution by natural selection, sorting among different in sequences of protein encoding genes, selection can improve adaptions rapidly new duplicated genes - new functions

molecular homologies

all forms of life essentially same genetic code - common ancestor, sharing of genes between different species (some homogenes new function of lost function)

molecular clock

an approach 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, assumption is that the the number of nucleotide substitutions in related gene is proportional to time elapsed since genes branched from common ancestors, understanding relationships among organism even without fossils, used to date evolutionary divergence billions years back

heterochrony

an evolutionary change in the rate or timing of developmental events, can lead to evolutionary transformations (ex: organism's shape dependent on growth rate of different body parts - changes in rate can alter) incr rate of finger bone growth -- develop wings

Autoploidy

an individual that has more than two chromosome sets that are all derived from a single species

genotype-phenotype correlation

animals can same genotype differ in phenotype due to diet

what proves patterns of evolution?

artificial selection, direct observations, homology, fossil records, biogeography

artifical selection vs natural selection

artificial- dramatic changes in a short period of time natural- should be capable of substantial modifications of species over many generations

describe three domains

bacteria domain- most currently known prokaryotes domain archaea- diverse group of prokaryotes eukarya- all organisms with true nuclei, single and mutlicellular organisms (plants, animals, fungi)

The Origin of Species

book published by Charles Darwin convinced scientists of evolution, Wallace developed hypothesis of natural selection identical to Darwin's theory before he published

What do new alleles arise from?

by mutation (change in nucleotide sequence) in multicellular organisms only mutations in cell lines that produce gametes can be passed to offspring (majority of mutations in animal not passed), more diff cell lines can produce gametes in cells and fungi

analogous

not homologous, features share similar function but not common ancestry, homolog features share same ancestor, but not necessarily similar function

how is genetic variation measured at the molecular level?

nucleotide variability - little of variation results in phenotypic variation because many occur with introns (noncoding) and exons (coding) most variants in exons don't cause change in amino acid sequence of protein encoded by gene, (though single variable site is enough to cause genetic variation at level of gene - 2 dif forms of enzyme produced)

directional selection

occurs when natural selection favors individuals exhibiting one extreme of a phenotypic range, thereby shifting the population's frequency curve for phenotypic character in one direction common when populations environment changes or population migrates to new environment

When does genetic variation occur?

occurs when there is a wide range of phenotypes in a population, when there is mutations genes duplicated or other processes produce new alleles and new genes (faster in organisms with shorter generations), can also be caused by sexual reproduction

Hybrids

offspring that result from an interspecific mating, barriers can block gene flow between species and limit formation of hybrids (usually a combo of hybrids)

what does macroevolution tell us about evolution?

origin of new species affected by small scale factors (natural selection in populations) and large scale factors (continental drift)

how can problems with molecular clocks be avoided?

calibrate molecular clocks with data on rates at which genes evolved in different taxa or by using many genes not just 1 or 2 (many gene fluctuations to natural selection over time may average out)

sexual selection (sympatric selection)

can also cause sympatric selection (many species more than double in number of fresh water fish species known in Europe, groups of original fish adapted to different food sources genetic divergence - speciation) females select male mates based on appearance can also be a factor, correlates to breeding can act as reproductive barrier keep gene pool of two species separate

changes in gene regulation

can be limited to one cell type fewer harmful side effects, can only affect one body part(spine)

how does a mutation have to be to have an impact on phenotype?

change as little as point mutations can have a significant impact on phenotype (ex; sickle cell) organisms reflect many generations of past selection hence phenotypes well suited for their environment, most mutations to phenotypes are harmful, usually removed by natural selection, some can hide heterozygotes

outgroup

closely related species or group of species from a lineage that is known to have diverged before the lineage that includes the ingroup Good outgroup based on morphology, paleontology, embryo develops, gene express

gene pool

consists of all copies of every type of allele at every locus in all members of the population, way to characterize a population's genetic makeup

paraphyletic group

consists of an ancestral species and some, but not all, of its descendants, most recent ancestor apart of group

what is an organism's fitness measure by?

contribution to gene pool

Important information on phylogenetic trees

1. Show patterns of descent not phenotypic similarities 2. Branching in a tree doesn't necessarily indicate actual absolute ages of species- not always a relation between branch length and time, look at patterns in terms of descent 3. Don't assume a taxon on polygenetic evolution from next to it (wolf didn't evolve from coyote share the same extinct ancestor, both descendants extant)

phylogenetic species concept

defines a species as the smallest group of individuals that share a common ancestor, forming one branch in tree of life

ecological species concept

defines a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment (ex: two species of oak trees might differ in size and ability to tolerate dry conditions but occasionally interbreeding, dif species connected by gene flow) asexual/sexual reprod

sexual dimorphism

differences between the secondary sex characteristics of males and females of the same species, often a result of sexual selection, characteristics include differences in size, color, behavior, ornamentation ex: peacocks

what are the three ways in which natural selection can occur?

directional, disruptive and stabilizing selection

morphological species concept

distinguishes a species by body shape and other structural features, applied to asexual/sexually reproducing, used without info on extent of gene, relies on subjective criteria

what do punctuated and gradual models tell us about how long it takes a new species to form?

even though species may have originated more slowly than its fossils suggest, punctuated pattern indicate speciation occurs more rapidly

example of ongoing natural selection in humans

evolution of drug resistant pathogens (disease causing viruses) can proliferate quickly in bacteria and viruses, bacterium: Staphylococcus aureus- usually no probability but genetic variant strains of methicillin resistant SA pathogens incr in virulent form of MRSA and clones, USA300, penicillin resistant, enzyme pencillase to destroy develop new antibiotics- develop resistance methicillin works in deactivating ezy in bacteria to synthesize cell walls, survive treatments reproduce at incr rates - multidrug resistant strains

Micro evolution

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

departure from conditions

evolutionary change common in natural population, can be HW equilibrium for specific genes

phylogenetic tree

evolutionary history of a group of organisms represented in a branching diagram, how taxonomists classified organisms within other groups, does not classify evolutionary relationships in system (over time key evolutionary features shared by close relatives can be lost which can lead to mistakes in species within not closely related species)

genetic drift

evolutionary mechanism, 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 chance events associated with survival and reproduction can result in loss of an alleles and affect what is passed to next generation two circumstances where genetic drift has big impact on population: founder and bottle neck effect

gene flow

evolutionary mechanism, The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes, tends to reduce genetic difference between populations, can cause two populations to combine into one with one common gene pool, affect how well populations adapt to local environment, can transfer alleles that improve of ability of population to adapt to local conditions, important agent of evolutionary change in humans

natural selection regarding genetic variation

evolutionary mechanism, individuals in a population exhibit variations in their heritable traits and those with traits are better suited to their environment tend to produce more offsprings than those with traits not as well suited, results in alleles being passed to next generation in proportions that differ from those in present generation typically through mutations

Reinforcement

hybrids often less fit than members of parent species natural selection should strengthen pre zygotic barriers to reproduction, reducing formation of unfit hybrids,

Paedomorphosis

if the development of reproductive organs accelerates compared to that of other organs, the sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species (ex: salamander sexually mature retaining gills/larval features)

punctuated equilibra

in 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, gradual model- change over longer periods of time punctuated model- new species change most as they branch from parents, diverge from one another slowly

molecular homoplasies

in organisms that do not appear to be closely related, the bases that their otherwise very different sequences happen to share may simply be coincidental matches (sequences that resemble each other at many points along length - homologous)

polyphyletic group

includes distantly related species but does not include their most recent common ancestor

natural selection

increases the frequency of adaptations favorable to environment, change in evolutions result in adaptation to new conditions, can give rise to new species, occurs between individuals and evolution individuals don't evolve - population evolves over time, can amplify or diminish only heritable traits differ among individuals in population, even if traits is heritable natural selection can't occur if all population genetically identical for trait

heterozygote advantage

individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes (NS maintain two or more alleles at locus) defined in terms of genotype (ex: phenotype of heterozygous is intermediate of phenotype of homozygous, heterozygote advantage form of stabilizing selection) ex: sickle cell disease (heterozygote protect against malaria)

What causes allele frequencies over hybrid zone?

infer obstacles in gene flow, geographical barriers can reduce flow, but not in toad example: toads incr embryo mortality hybrids poor survival/reproduction produce few viable offsprings

Adaptation

inherited characteristic that increases an organism's chance of survival and reproduction in specific environments (link between adaptation and origin of new species)

applications of Handy Weinberg Equilibrium

initial test of whether evolution occurring at particular locus is in a population (no difference no evolution) medical application: estimate percentage of population carrying alleles for inherited disease

how does sexual selection operate?

intra sexual selection, mate choice- selection within the same sex, individuals of 1 sex compete directly for mates (typically the males) females typically particular in choosing mate based on showiness and behavior

how prevalent are mutations?

low in plants/animals and even lower in prokaryotes (more generations per unit of time) mutations and viruses generate genetic variation ex: HIV (gen time of 2 days, RNA genome higher mutation rate, some mutant forms HIV resistant to particular drugs-- cocktail of drugs good treatment)

heterozygote protection

maintains a huge pool of alleles that might not be favored under present conditions, but that could be beneficial if the environment changes

stability

many hybrid zones are stable in sense that hybrids continue to be produced, sometimes occurs because hybrids survive or reproduce better than members of parent species, stable hybrid zones also where hybrids are selected against unexpected result possibly due to narrow hybrid zone

homeotic genes

master regulatory genes that determine how basic features will develop, one homeotic genes is Hox genes -positional information on animal embryo

why don't molecular clocks run as smoothly as possible?

molecular clocks don't run as smoothly as expected if underlying mutations selectively neutral irregularities (result of natural selection) in certain DNA changes are favored over other directions of natural selection may change over long periods time and average out some genes experiencing selection markers of elapsed time

did species on different sides of isthmus originate by allopatric speciation?

morphological and genetic data of shrimp into 15 pairs of sister species pairs whose members are each other's close relative (each sister species live on Atlantic/Pacific side) suggest that two species arose as consequence of geographic isolation

what is the role of natural selection in adaptive evolution?

natural selection increases the frequency of alleles that enhance survival and reproduction (ex: jaw of snakes allow to eat prey of larger size) individuals with favorable traits increase species, suit environment, adaptive evolution dynamic and continuous cause environment is always changing natural selection only evolutionary mechanism that consistently leads to adaptive evolution (not genetic drift or gene flow)

changes in gene sequence

new genes from gene duplication facilitate origin of novel morphological forms, through experiment proved change in nucleotide sequence - major evolutionary change, affects function

strata

new layers of sediment cover older ones and compress them into superimposed layers of rock strata, fossils in particular stratum glimpse of organisms population on Earth at that time

species can arise rapidly once divergence begins, what is time between speciation events?

time elapse before population of newly formed species start to diverge and time it takes for speciation to be complete avg in millions of years, organisms don't have speciation clock cause them to produce new species at regular intervals, speciation begins only after gene flow is interrupted by changing environment

Beagle Voyage

took sail on HMS Beagle with scientist FitzRoy observed animals and plants in South America, Earth age must be older than accepted thousand years, went to Galapagos islands where unique organisms never seen before, strayed from South American mainland and diversified new species

homologous structures

underlying skeletons of arms, forelegs, flippers, wings of different mammals, represent variations on a structural theme present in common ancestor

what do modifications by natural selection explain?

unity of life, diversity of life, ways organisms are suited for environment unity of life: organisms share many characteristics, descent from one organism diversity of life: different environments, modifications to adapt ways organisms are suited for their environments

variation during gene duplication: how does it occur?

variation often occurs during duplication due to errors in meiosis, unequal crossing over, slippage during DNA rep, activities of transposable elements, duplications of larger chromosomes (harmful) gene duplications that don't have severe effects can persist over generations allowing mutations and eventually expand genomes

phylogenetic bracketing

we can predict (by parsimony) that features shared by two groups of closely related organisms are present in their common ancestor and all of its descendants unless independent data indicate otherwise Treat polygenic tree as a hypothesis about how organisms in tree relate to each other Bracketing used to make novel predictions about dinosaurs(connect Dino, birds, crocs) use of fossils of Dino embryo to connect birds an Dino's eventually crocs

what causes allopolyploid?

what two different species interbreed and form hybrid offspring, which are sterile because two sets of chromosomes from one species can't pair during meiosis with other species, infertile hybrid can propagate asexually, in subsequent generations various mechanisms can change sterile hybrid to fertile polyploid -allopolyploid

founder effect

when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differ from source population (ex: members of population blown by storm to island) accounts for relatively high frequency of certain inherited disorders among isolated human population

habitat differentiation

when a subpopulation exploits a habitat or resource not used by the parent population, mechanism for sympatric speciation

bottleneck effect

when a sudden change in the environment may drastically reduce the size of a population, the survivors may have passed through a restrictive "bottleneck", by chance certain alleles may be overproduced by survivors other alleles underrepresented or absent

disruptive selection

when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes (intermediates size beak inefficient compared to two extremes)

convergent evolution

why distantly related organisms can relate to each other, independent evolutions of similar features in different lineages (ex: Australian mauriospal sugar glider vs similar to flying squirrel eutherians of North America different ancestors similar evolutionary adaptation)

do females select mate based on traits indicative of good genes?

yes, "good genes" alleles indicative of robust immune system

monophyletic group (clade)

Clade contains common ancestors and all descendants, a taxon is a clad if it monophyletic

What holds the gene pool of a species together, causing its members to resemble each other more than they resemble other species?

Gene flow: the transfer of alleles between populations. Members of a species often resemble each other because their populations are connected by gene flow.

postzygotic barriers

"After the zygote" many contribute to reproductive isolation after hybrid zygote is formed (ex: developmental errors may reduce hybrid embryo survival or hybrids infertile) viability (survival) fertility (sterile) breakdown (1st gen ok 2nd gen sterile) in hybrids

prezygotic barriers

"before the zygote" block fertilization from occurring, act in three ways: impeding members of different species from attempting to mate, preventing an attempted mating from being completed successfully, or hindering fertilization if mating is completed successfully habitat isolation temporal isolation (day and night) behavioral isolation mechanical isolation (parts don't fit)

evolution

"descent with modification" a change in the genetic composition of a population from generation to generation Darwin: Earth's many species are descendants of ancestral species different from present species

Practical applications of Phylogenetic trees

- determine a specie's closest living relative, can be used as reservoirs of beneficial alleles transferred -infer species identities by analyzing relatedness of DNA sequence of different organisms - infer phylogeny - gather info on morphology, genes, biochemistry of relevant organisms, focus features of common ancestry

scientists before Darwin

-Aristotle- viewed species as fixed (unchanging) recognized affinities of different organisms, scala naturale life forms arranged on a ladder -Linnaeus- developed binomial "two part" format of naming species (homo sapiens) develop classification system -Hulton- proposed Earth's geographical features explained by gradual mechanisms valleys formed by rivers wearing through rocks -Lyell- geographical process operating today as in the past and at the same rate

what can evolutionary change result from?

-alteration in genes that control body organization -changes in gene sequences -changes in gene regulation

two different ways to view evolution

-pattern of evolutionary revealed by data from many scientific disciplines, facts and observations of natural world -process evolutionary mechanisms that produce observed patterns of change

Conditions for Hardy-Weinberg Equilibrium

1. No mutations (alleles or genes) 2. Random mating (no inbreeding, near neighbor) 3. No natural selection (changes allele frequencies) 4. Extremely large population size (small more likely for allele frequency fluctuations) 5. No gene flow (moving alleles in or out of population)

Alloploidy

A fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes, fertile when mating with each other but can't interbreed with either parent species represent new bio species

population

A group of individuals that belong to the same species and live in the same area and interbreed, producing fertile offspring, different population of a specie can be geographically isolated, not isolated pops breed with each other more closely related

basal taxon

A lineage that diverges from all other lineages in a group very early in the history

Cladistics

An approach to systematics, common ancestry is the criterium used to classify

shared derived character

An evolutionary novelty that is unique to a particular clade. (Mammal and hair) Character is relative to matter and part of branch being studied

homoplacies

Analogous structures that arose independently

Tree diagrams represent time and genetic change

Branch lengths proportional to evolutionary change or time (Ex: branch lengths can represent genetic change, longer more change) Even though branches of phlyotree have different lengths among organisms today all different. In some branches can indicate time, use fossil data to place branch points with geological tie, you can combine time and change tree types

How can we calculate the clock of gene with reliable average rate of evolution?

By graphing number of genetic differences against dates of evolutionary branch points known from fossil record, gene change inferred from date of events from fossil record Typically have fairly smooth average rate of change some deviations from average rate same gene develops at different in different organisms When comparing genes that are clocklike rate of clock may vary greatly gene to gene

what is the connection between natural selection and the capacity to "over reproduce?"

Darwin saw an important connection between natural selection and the capacity to "over reproduce" after reading Malthus: humans suffering result in population potential to reproduce faster than resources, all species have power to over reproduce

natural selection

Darwin's explanation of centered adaptation, process in which individuals have certain inherited traits to survive and reproduce at higher rates than other individuals because of their traits

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. strengths: can be used to evaluate reproductive isolation fossils cannot, doesn't apply to a sexually reproducing species

genetic variation

Differences among individuals in the composition of their genes or other DNA segments, reflected by phenotypic variations, two types of phenotypic differences: heritable phenotypic differences "either or" (purple or white flowers) determined by a single locus, some phenotypic differences vary in gradation

Clads

Groups biologists attempt to place species in, using cladistics each clad includes an ancestral species and all of its descendants, clads positioned within larger clad

sister taxa (sister group)

Groups of organisms that share an immediate ancestor, close relatives

Systematics

How biologists reconstruct and interpret phylogenies, by classifying organisms and determine their evolutionary relationships

Species definition according BSC

In a group of population whose members have potential to interbreed in nature and produce viable, fertile offspring but don't produce viable, fertile offspring with members of other groups, members of biospecies are united by reproduce compatible at least potential (all humans in same species)

Microevolution vs. Macroevolution

Micro: changes over time in allele frequency in a population Macro: broad pattern of evolution above species level (ex: change of new groups of species like plant through speciation events)

Pangea

Pangea- Earth's landmass into a single large continent broke up due to continental drift

Speciation

Process by one species splits into two or more species, produces lots of diversity through new species and can explain unity of life or shared characteristics

morphological homologies

Represent features shared by common ancestry, ex: similar in number and arrangement of forelimbs of mammals, organisms with similar morphologies/DNA likely to be closely related, some morphological divergence greater genes smaller and vice versa

sexual reproduction and genetic variation

Reshuffling of different combinations of alleles from parents; produces genetic variability, shuffles alleles through crossing over, independent assortment of chromosomes, fertilization homolog chrom of each parent trade alleles during crossing over, randomly distributed into gametes and then because of so many possible mating combos fertilization brings gametes together likely to have dif genetic backgrounds

convergent evolution

Similar environment pressure and natural selection produce similar adaptation in organisms of two different lineages

Analogy

Similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait, analogous characteristics evolved independently in two lineages that adapted to similar lives

Taxon

Taxon unit at any level of hierarchy, classifying species, structuring view on the world, characters helpful to classify

Difference between homologous and analogy example

Very important in reconstructing phylogenies Underlying skeleton birds/bats - homologous Wings are not homologous- analogous

polytomy

a branch point from which more than two descendant groups emerge, evolutionary relationships among taxa not yet clear

Rooted

a branch point within the tree represents the most recent common ancestor of all taxa in the tree

shared ancestral character

a character that originated in an ancestor of the taxon (ex: vertebrates and backbones) unique to particular clade

how many genes influence the formation of new species?

a few or many genes can influence evolution of reproductive isolation and the emergence of new species

horizontal gene transfer

a process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable elements and plasmids, viral infection, and perhaps fusions of organisms of three domains - dif results phyl trees based on assumption genes are passed gen to gen vertically which supports gene transfer role inconsistent results many hypothesis early history should be an entagled web

sexual selection

a process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates

hybrid zone

a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry, some zones form narrow bands (two close relatives) can compare frequency of specific allele with distance from hybrid zone center typically located wherever habitats of interbreeding species meet, when two species lack complementary barriers don't reproduce isolated- new species, 3 outcomes: reinforce barriers, fusion of species, stability

Polyploidy

a species may originate from an accident during cell division that results in extra sets of chromosomes, poly speciation sometimes in animals, two forms observed in plants

Biogeography

fourth type of evidence for evolution, scientific study of geographic distributions of a species, geo distribution influenced by many factors ex: predict where fossils of animal are based on geographical and anatomical evidence

HW equilibrium example

frequency of alleles: p- frequency of Cr allele - .8, 80% q- frequency of Cw allele- .2, 20% gametes produced: each egg: Cr 80%, Cw 20% each sperm: Cr 80%, Cw 20% frequencies of genotypes: homozygous Cr: pxp, .8x.8= .64, 64% homozygous Cw: qxq, .2x.2=.4, 4% heterozygous: egg Cr sperm Cw: pxq, .8x.2= .16x2=.32, 32%

adaptative radiation

fuels increase in diversity of life, periods of evolution change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in communities, occurred after all 5 of the mass extinction

allopartic speciation

gene flow is interrupted when a population is divided into geographically isolated sub populations (lake divides) can occur without geographic remodeling (individuals colonize remote area) ex: Darwin's finches on the Galapagos Islands, which may have speciated allopatrically because of volcanic eruptions that divided populations

How much do genes and other DNA sequences vary from one individual to another?

gene variation at whole gene level (gene variability) quantified as the average percent of loci that are heterozygous

how do genes and molecular clocks relate?

genes most likely effected by natural selection at fossil based estimates used carefully molecular clocks can help understanding of evolution relation (ex: date origin of HIV in humans)

what is the effect of ongoing genetic drift?

have substantial effects on gene population until pop is large enough, if it recovers from bottleneck will have lower genetic variation for a time, humans can creates bottle necks in other species (prairie chickens)

Molecular comparisons

help biologists sort out the evolutionary connections among species, reveal that many base substitutions and differences have accumulated in comparable genes of Australian and American mole, difference indicate diverged early not closely related

Process of Allopatric Speciation

how formidable a geographic barrier is to promote allopatric speciation depends on ability of organisms to move about when geographic isolation has occurred, separated gene pools may diverge, different mutations NS and genetic drift may alter allele frequency in different ways speciation can occur in allopatric pop or in nature

what is phenotypic variation a result of?

phenotypic variation is not the result of genetic differences among individuals, it is the product of inherited genotype and environment influences (ex: bodybuilders don't pass down muscles to offsprings) only genetically determined part of phenotypic variation can evolutionary consequences

neutral variation

point mutations in noncoding regions conferring no selective advantage or disadvantage, due to redundancy of genetic code in gene that encodes for protein point mutation no effect on protein function if amino acid comp not changed and if it is no effect on protein shape/function

balancing selection

preserve variation at some loci, maintaining to or more phenotypic forms in a population (includes heterozygous advantage and frequency dependent selection)

adaptative evolution

process in which traits that enhance survival or reproduction tend to increase in frequency in a population over time, Natural selection increases the frequency of alleles that provide reproductive advantage and lead to adaptative evolution

Lamarack's hypothesis

proposed mechanism for how life changes hypothesis not accurate - use and disuse, parts of body used extensively become larger and stronger, not used deteriorate inheritance of acquired characteristics - organisms can pass modification to offsprings (giraffe neck)

fossils

remains/traces of organisms from the past, Darwin used fossils to study sedimentary rocks formed from sand, mud settled at bottom of sea, lakes, swamps

vestigal structures

remnants of features that served a function in the organism's ancestors (ex: snake vestige of pelvis and leg bones of ancestors)

fusion

reproduction barriers may be weaker when two species meet in hybrid zone usually gene flow further weakens barriers, gene pools of two species become increasingly similar , speciation process reverses , causes two hybridizing species to fuse into one, loss of one species

what can be discovered by comparing early stages of development in different animals?

reveals additional anatomical homologies not visible in adult organisms (ex: all vertebrate embryos have throat arches which develop into different structures with different functions gills, ears, throat)

Summarize genetic drift

significant in small populations can cause allele frequency to change at random can lead to loss of genetic variation within pop can cause harmful alleles to be fixed

What causes differences in speed at which clocklike genes evolve?

some mutations are selectively neutral (beneficial or detrimental) many are harmful an removed, but if most of the rest are neutral and have little or no effect on survival/reproduction , then the rate of evolution of neutral mutations should be regular like a clock, differences in clock rate for different genes are function how important a gene is, if sequence of amino acids that a gene specifics is essential to survival, most mutational changes harmful a few neutral, result: genes change slowly if sequence of amino acids is less critical fewer of new mutations will be harmful and more neutral, change more quickly

sympatric speciation

speciation occurs in populations that live in the same geographic area ex: occurred in apple maggot flies (Rhagoletis pomonella), a parasitic insect that laid its eggs in the fruit of wild hawthorns (Crataegus) until one subset of the population began to lay its eggs in the fruit of domesticated apple trees (Malus domestica) that grew in the same area. That small group of apple maggot flies selected a different host species from the rest of its kind, and its offspring became accustomed to domesticated apples and later laid their own eggs in them, thereby cementing the shift in host

endemic species

species that are confined to a specific geographic area, evolution can explain biographical data (islands colonized by species from nearest main land, colonists give rise to new endemic species)

Paleontology

study of fossils, developed by Cuvier, old stratum more dissimilar fossils to current life form, even discovered extinct species

what happens when herbivores switch to new food source?

study on soapberry bugs use beaks to feed, beaks length change in order to adapt to food eaten - natural selection can cause rapid evolution in a wild population

how can reproductive barriers form between sympatric populations while their members remain in contact with each other>

such contact resulting in gene flow make sympatric speciation less common than allopatric speciation sympatric speciation can occur if gene flow is reduced by factors as polyploidy, habitat differentiation and sexual selection

Importance of allopatric speciation

suggested by fact that regions are isolated or highly subdivided by barriers typically have more species than do otherwise similar regions that lack features reproductive isolation between two species generally increase geo distance, geographic isolation interbreeding between members of allopatric populations

Linnaean System

taxonomic system, places genera into same families, families—> order —> classes —-> phyla —> kingdoms—> domains (Ex: species: "Panthera pardus" genus: "panthera" family: felidae order: carinvora class: mammalia phylum: chordata kingdom: animal domain: eukarya

relative fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals, although we often refer to relative fitness of a genotype entity is subjected to by natural selection is the whole organism not underlying genotype, selection acts directly on phenotype, indirectly on genotype

frequency-dependent selection

the fitness of a phenotype depends on how common it is in the population, selection favors whichever phenotype is less common - oscillates over and balancing selection due to frequency dependent selection, each frequency 50%

branch points

the representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor, divergence of two evolutionary lineages from common ancestors

Taxonomy

the scientific discipline concerned with classifying and naming organisms

Handy-Weinberg equilibrium

the state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided only Medelian segregation and recombinant alleles are at work we can view reproduction as random selecting alleles from a bin (gene pool) and combining assuming mating is random p- frequency of one allele q- frequency of another allele homozygous - pxp, qxq heterozygous- 2pq

what effects do organism's traits have on performance and coping with evolution?

they advance the increase in the number of offsprings that survive and reproduce, traits favored increase in the next generation

fossil records

third type of evidence for evolution, documents patterns of evolution, past organisms and differences with the present, evolutionary changes occurred in various groups of organism (fossils show stickleback fish reduce pelvis size natural selection) and info on origins of new organism (cretan closely related to even toed ungulates)