7The Greek philosopher Aristotle (384-322 BCE) Viewed species as fixed and unchanging (Scala naturae) Fixed rungs on a ladder of complexityThe Old Testament of the BibleHolds that species were individually designed by God and therefore perfectCarolus Linnaeus ( )Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purposeWas a founder of taxonomy, classifying life’s diversity “for the greater glory of God”
8Charles Darwin (1809-1882) Born in England Attended medical school, HATED IT, and dropped out to become a priestLiked to stuff birds instead of dissect humansDidn’t like grave robbing for bodiesBoarded the H.M.S. Beagle for a 5 year UNPAID journey as a naturalist (nothing exists outside of natural laws that govern earth)
9Charles Darwin “Descent with modification” from an ancestral species November 24th 1859
10The Origin of Species Occurrence of Evolution Mechanism of Evolution Descent with Modificationall organisms related through descent from some unknownancestral populationdiverse modifications (adaptations) accumulated over timeMechanism of EvolutionNatural Selection and Adaptationnatural selection is the differential success in reproductionnatural selection occurs from the interaction between theenvironment and the inherit variability in a populationvariations in a population arise by chanceCan selection actually cause substantial change in a population?
13Darwin’s Field Research South American flora/fauna distinct from European flora/faunaS. American temperate species were more closely related to S. American tropical species than European temperate speciesS. American fossils were distinctly S. AmericanTropical Rainforest of South America
14Galapagos Islands+ most animal species on Galapagos unique to those islands, butresemble S. American continental species+ Darwin’s Finches- 13 types+ some unique to individual islands+ others found on two or more islands close togetherDarwin proposed:+ new species could arise from an ancestral population bygradually accumulating adaptations to a different environment.- Theory of natural selection as the mechanism of adaptiveevolution
15Alfred Russel Wallace (1823-1913) Presented a paper with identical ideas as Darwin on July 1, 1858 at the Linnaean Society meetingWas a botanist who came up with virtually the same concept of natural selection more or less independently through his studies on the Malay archipelago. Darwin panicked because he was not ready with his book yet!
16Where did Darwin and Wallace get the idea of evolution?
17Jean Baptiste Lamarck (1744-1829) Lamarck claimed that evolution was driven by "use vs. disuse"A used structure will become larger, stronger and more important.A disused structure will atrophy and become VESTIGIAL.Evolution occurs because organisms have an innate drive to become more complex
18Theory of “Use vs. Disuse” The long necks of giraffes were due to their stretching for food, and giraffes passed their stretched necks on to their offspring.Similarly, the big, “ripped” muscles developed by the village blacksmith with all his hammering and slinging of heavy metal objects would be expected to be passed on to his offspring.
19Theory of “Acquired Characteristics” Lamarck claimed that traits acquired during an organism's lifetime could be inherited by that organism's offspring.
20Georges Cuvier (1769-1832) Created Paleontology (The study of fossils) He noted that deeper layers of sedimentary rock had diversity of organisms far different from present day life found in more recent layersProposed the idea of extinction based on fossils
21James Hutton ( )A Scottish geologist who challenged Cuvier's view in 1795 with his idea of GRADUALISMProposed that large changes in the earth's surface could be caused by slow, constant processese.g. erosion by a river
22Charles Lyell ( )Earth processes had been going on constantly, and could explain the appearance of the earth.This theory, uniformitarianism, was a strong basis for Darwin's later theory of natural selection.
23Thomas Malthus ( )Suggested that much of humanity's suffering (disease, famine, homelessness and war) was the inevitable result of overpopulation: humans reproduced more quickly than their food supply could support them.Malthus showed that populations, if allowed to grow unchecked, increase at a geometric rate.
25Darwin made some profound observations, from which Ernst Mayr inferred some conclusions... Observation #1. All species have huge potential fertilityObservation #2. Except for seasonal fluctuations, populations tend to maintain a stable size.Observation #3. Environmental resources are limited.
26Inference #1The production of more individuals than the environment can support leads to a "struggle for existence," with only a fraction of offspring surviving in each generation.
27ObservationsObservation #4: No two individuals in a population are exactly alikeObservation #5: Much of the observed variation in a population is heritable
28Inference #2Survival in this "struggle for existence is not random, but depends, in part, on the hereditary makeup of the survivors.Those individuals who inherit characteristics that allow them to best exploit their environment are likely to leave more offspring than individuals who are less well suited to their environment.
29Inference #3Unequal reproduction between suited and unsuited organisms will eventually cause a gradual change in a population, with characteristics favorable to that particular environment accumulating over the generations.
30SO WHAT IS THIS THEORY OF NATURAL SELECTION? It can be broken down into four basic tenets, or ideas
31Theory of Natural Selection 1. Organisms are capable of producing huge numbers of offspring.2. Those offspring are variable in appearance and function, and some of those variations are heritable.
32Theory of Natural Selection 3. Environmental resources are limited, and those varied offspring must compete for their share.4. Survival and reproduction of the varied offspring is not random. Those individuals whose inherited characteristics make them better able to compete for resources will live longer and leave more offspring than those not as able to compete for those limited resources.
33Natural selection is differential success in reproduction That results from the interaction between individuals that vary in heritable traits and their environment
34Natural Selection Definition isdifferential success in reproductionSelection can only edit existing variations
35EvolutionTheory - an accepted hypothesis that has been tested over and over again without yet being disprovedDefinition - Evolution is the change in the overall genetic makeup of a population over timeThree Basic Components a. Individuals cannot evolve. Populations evolve. b. Natural selection is the mechanism of evolution. c. Evolution occurs by chance (NOT GOAL ORIENTED).
36EvolutionPopulations are a group of interbreeding individuals belonging to the same species and sharing a common geographic areaNatural selection favors individuals, so multiple generations must be examined
37What is speciation and who studies it? Speciation is the creation of a new speciesScientists who study the processes and mechanisms that lead to such speciation events are called EVOLUTIONARY BIOLOGISTS.
38Speciesspecies as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but are unable to produce viable fertile offspring with members of other populations
39the origin of new taxonomic groups (new species, etc.) + Anagenesis Macroevolutionthe origin of new taxonomicgroups (new species, etc.)+ Anagenesis- phyletic evolution- transformation of onespecies to another+ Cladogenesis- branching evolution- new species arise from a population that buds from a parent species+ increases biodiversity(b) Cladogenesis(a) Anagenesis
40Speciation can occur in two ways Allopatric speciationSympatric speciationAllopatric speciation. A population forms a newspecies while geographically isolated from its parent population.Sympatric speciation. A small population becomes a new species without geographic separation.
41Allopatric Speciation A population becomes physically separated from the rest of the species by a geographical barrier that prevents interbreeding. Because gene flow is disrupted by this physical barrier, new species will form.
44Sympatric SpeciationTwo populations are geographically close to each other, but they are reproductively isolated from each other by different habitats, mating seasons, etc.PolyploidyIs the presence of extra sets of chromosomes in cells due to accidents during cell divisionHas caused the evolution of some plant species
45An autopolyploidIs an individual that has more than two chromosome sets, all derived from a single species2n = 64n = 122n4nFailure of cell division in a cell of a growing diploid plant after chromosome duplication gives rise to a tetraploid branch or other tissue.Gametes produced by flowers on this branch will be diploid.Offspring with tetraploid karyotypes may be viable and fertile—a new biological species.
46An allopolyploidIs a species with multiple sets of chromosomes derived from different speciesMeiotic error;chromosomenumber notreduced from2n to nUnreduced gametewith 4 chromosomesHybrid with7 chromosomeswith 7 chromosomesViable fertile hybrid(allopolyploid)Normal gameten = 3Species A2n = 4Species B2n = 62n = 10
48Reproductive Barriers A reproductive barrier is any factor that prevents two species from producing fertile hybrids, thus contributing to reproductive isolation.Habitat IsolationTemporal IsolationBehavioral IsolationMechanical IsolationGametic Isolation
49Reproductive Barriers Prezygotic barriersImpede mating between species or hinder the fertilization of ova if members of different species attempt to matePostzygotic barriersOften prevent the hybrid zygote from developing into a viable, fertile adult
51Individuals of different species Prezygotic and postzygotic barriersPrezygotic barriers impede mating or hinder fertilization if mating does occurIndividuals of different speciesMating attemptHabitat isolationTemporal isolationBehavioral isolationMechanical isolationHABITAT ISOLATIONTEMPORAL ISOLATIONBEHAVIORAL ISOLATIONMECHANICAL ISOLATION(b)(a)(c)(d)(e)(f)(g)
54Adaptive RadiationAdaptive Radiation - Evolutionary process in which the original species gives rise to many new species, each of which is adapted to a new habitat and a new way of life. E.g. Darwin's Finches
58Evidence for Evolution HOMOLOGY is a characteristic shared by two species (or other taxa) that is similar because of common ancestry.Artificial Selection Farmers had been conducting this controlled breeding of livestock and crops for years in order to obtain the most milk from cows or the best cobs from corn plants.
59Evidence for Evolution Paleontology - Study of Fossils a. Fossil - preserved evidence of past life b. Radioactive Dating - method by which fossil age can be determined by the amount of organic matter remaining in the specimen. This is possible because some substances break down at a known rate (half-life).
61Types of homologymorphological homology – species placed in the same taxonomic category show anatomical similarities.ontogenetic homology - species placed in the same taxonomic category show developmental (embryological) similarities.molecular homology - species placed in the same taxonomic category show similarities in DNA and RNA.
62MORPHOLOGICAL HOMOLOGY Structures derived from a common ancestral structure are called:HOMOLOGOUS STRUCTURES
65Ontogenetic HomologyThe human embryo has gills, a post-anal tail, webbing between the toes & fingers, & spends its entire time floating and developing in amniotic fluid has similar salt concentration as ocean water
75Types of EvolutionDivergent Evolution - Method of evolution accounting for the presence of homologous structures. Multiple species of organisms descended from the same common ancestor at some point in the past.Convergent Evolution - Method of evolution accounting for the presence of analogous structures. Organisms of different species often live in similar environments, thus explaining the presence of features with similar functions.
77An ongoing processEvolution can be considered a process of "remodeling" a population over the course of many generations, with the driving force being the natural selection factors that favor one form over another in specific environments.
78Vestigial StructuresHave marginal, if any use to the organisms in which they occur.EXAMPLES:femurs in pythonid snakes and pelvis in cetaceans (whales)appendix in humanscoccyx in great apes
82Rate of EvolutionGradual evolution occurs where the increment of change is small compared to that of time.Punctuated evolution occurs where the increment of change is very large compared to that of time in discrete intervals, while most of the time there is virtually no change at all.
96Causes of EvolutionMutations - random changes in genetic material at the level of the DNA nucleotides or entire chromosomesNatural Selection - most important cause of evolution; measured in terms of an organism's fitness, which is its ability to produce surviving offspringModes of Selectiona. Stabilizing Selection - average phenotypes have a selective advantage over the extreme phenotypesb. Directional Selection - phenotype at one extreme has a selective advantage over those at the other extremec. Disruptive Selection - both extreme phenotypes are favored over the intermediate phenotypes
97Modes of Selection Original population Frequency of individuals In this case, darker mice are favoredbecause they live among darkrocks and a darker fur color concealsThem from predators.These mice have colonized apatchy habitat made up of lightand dark rocks, with the resultthat mice of an intermediatecolor are at a disadvantage.If the environment consists ofrocks of an intermediate color,both light and dark mice willbe selected against.Phenotypes (fur color)Original populationOriginalpopulationEvolvedFrequency of individuals
99Causes of Evolution3. Mating Preferences - Organisms usually do not choose their mates at random, thus the selection process can cause evolution4. Gene Flow - Transfer of genes between different populations of organisms. This situation leads to increased similarity between the two populations (Tends to reduce differences between populations over time)5. Genetic Drift (Founder Effect & Bottleneck) - Situation that results in changes to a population's gene pool caused by random events, not natural selection. This situation can have drastic effects on small populations of individuals. Common on islands.
106Understanding the bottleneck effect Can increase understanding of how human activity affects other speciesBottlenecking a population of organisms tends to reduce genetic variation, as in these northern elephant seals in California that were once hunted nearly to extinction.
108Note the Difference Macroevolution -Evolutionary change above the species level e.g. the appearance of feathers on dinosaursMacroevolutionary changeIs the cumulative change during thousands of small speciation episodesMicroevolutionIs change in the genetic makeup of a population from generation to generation
109Population geneticsIs the study of how populations change genetically over timePopulation geneticistsMeasure the number of polymorphisms in a population by determining the amount of heterozygosity at the gene level and the molecular levelAverage heterozygosityMeasures the average percent of loci that are heterozygous in a population
110Three major factors alter allele frequencies and bring about most evolutionary change Natural selectionGenetic driftGene flow
112Figure 23.4 Generation 1 CRCR CWCW genotype Plants mate 2 All CRCW (all pink flowers)50% CRgametes50% CWCome together at random23425% CRCR50% CRCW25% CWCWAlleles segregate, and subsequentgenerations also have three typesof flowers in the same proportions
113Hardy-Weinberg Theorem genetic structure of a non-evolvingpopulation remains constant+ sexual recombination cannot alterthe relative frequencies of alleles- Hardy-Weinberg equilibriumHardy-Weinberg equationp pq + q2 = 1p2: frequency of AA genotype2pq: frequency of Aa genotypeq2: frequency of aa genotype- p: frequency of A allele- q: frequency of a allele
114Hardy-WeinbergHW law states --> original of a genotypes alleles remains CONSTANTHW Equilibrium... is defined algebraicallyany gene with 2 allelic forms A and alet frequency of one allele (A) = p & frequency of other allele (a) = qthen by definition, p + q = 1HW equation (p + q)2 = p pq q2 = 1AA Aa aa
117mechanisms that help to preserve genetic variation in a population DiploidyMaintains genetic variation in the form of hidden recessive allelesHeterozygote AdvantageIndividuals who are heterozygous at a particular locus have greater fitness than homozygotesNatural selectionWill tend to maintain two or more alleles at that locus
118Heterozygote Advantage Plasmodium falciparumAA = No sickle (Dead from malaria)Aa = sickle traitaa = sickle disease (Dead)
119Sexual reproduction Produces fewer reproductive offspring than asexual reproduction, a so-called reproductive handicapAsexual reproductionFemaleSexual reproductionMaleGeneration 1Generation 2Generation 3Generation 4
120If sexual reproduction is a handicap, why has it persisted? It produces genetic variation that may aid in disease resistance
122PhylogenyThe evolutionary history of a species or group of related species depicted as a branching treeEach branch represents a new species which inherits many (primitive) traits from the ancestor but also has a new (derived) trait which appear for the 1st time
123Systematics Morphological, biochemical, and molecular An analytical approach to understanding thediversity and relationships of organisms, bothpresent-day and extinctMorphological, biochemical, and molecularcomparisons are used to infer evolutionaryrelationships
125The fossil record Fossils reveal Is based on the sequence in which fossils have accumulated in such strataFossils revealAncestral characteristics that may have been lost over time
126Diversity of Life Learned Through the Fossil Record Mass Extinctionsextinction is inevitablein a changing world+ extinctions open upnew adaptive zones- new livingconditions,resources, andopportunities
127Dating Fossils Relative Dating tells the order in which groups of species were present in a sequence of strata (before/after, early/late)+ index fossils- fossils that permit the relative dating of rocks within a narrow time spanAbsolute Datingdating that provides the age of fossils in years+ radiometric dating- use of radioactive isotopes to date specimens (Carbon-14)
128Dinosaur bones being excavated from sandstone Tusks of a 23,000-year-old mammoth, frozen whole in Siberian iceBoy standing in a 150-million-year-old dinosaur track in ColoradoCasts of ammonites, about 375 million years oldInsects preserved whole in amberPetrified tree in Arizona, about 190 million years oldLeaf fossil, about 40 million years old
129In addition to fossil organisms Phylogenetic history can be inferred from certain morphological and molecular similarities among living organismsIn general, organisms that share very similar morphologies or similar DNA sequencesAre likely to be more closely related than organisms with vastly different structures or sequences
130Systematists use computer programs and mathematical tools C C A T C A G A G T C CC C A T C A G A G T C CC C A T C A G A G T C CG T ADeletionInsertionC C A T C A A G T C CC C A T G T A C A G A G T C CC C A T C A A G T C CC C A T G T A C A G A G T C C1 Ancestral homologous DNA segments are identical as species 1 and species 2 begin to diverge from their common ancestor.2 Deletion and insertion mutations shift what had been matching sequences in the two species.3 Homologous regions (yellow) do not all align because of these mutations.4 Homologous regions realign after a computer program adds gaps in sequence 1.12Systematists use computer programs and mathematical toolsWhen analyzing comparable DNA segments from different organisms
131Sorting Homology from Analogy A potential misconception in constructing a phylogenyIs similarity due to convergent evolution, called analogy, rather than shared ancestryConvergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionaryAnalogous structures or molecular sequences that evolved independentlyAre also called homoplasies
132Binomial nomenclature Phylogenetic systematics connect classification with evolutionary historyTaxonomyIs the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differencesBinomial nomenclatureIs the two-part format of the scientific name of an organismWas developed by Carolus Linnaeus
133Classification based on physical and structural similarities Carolus Linnaeus ( )Created binomial nomenclature (2 word naming system)1st word = Genus (genera if plural) = a group of similar species2nd word = specific epithet = SpeciesScientific name = Genus + specific epithet e.g. Homo sapiens
134Writing Species Names Rules for writing species names Latin is the language of scientific names (Latin is no longer spoken, so it does not change)Italicize in print and underline when hand written1st letter of the genus is CAPITALIZED & 1st letter of specific epithet is lowercase
135Writing Species NamesCanis latrans = CoyoteCanis lupus = Grey wolf
141Six Kingdoms Protista · Eukoryotic Eubacteria · Autotrophs and heterotrophs· Lacks organs systems· Lives in moist environments· Unicellular or multicellularFungi· Eukaryotic· Heterotrophs· Absorbs nutrients from organic material in its environmentEubacteria· Prokaryotic· True bacteria· RNA is simple· Have true cell walls· UnicellularArchaebacteria· RNA more complex
145Each branch point Represents the divergence of two species Leopard DomesticcatCommon ancestor
146“Deeper” branch points Represent progressively greater amounts of divergenceLeopardDomesticcatCommon ancestorWolf
147Cladistics Vocabulary Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristicsA cladogramIs a depiction of patterns of shared characteristics among taxaA clade within a cladogramIs defined as a group of species that includes an ancestral species and all its descendantsCladisticsIs the study of resemblances among clades
148Cladistics Vocabulary Character -- Heritable trait possessed by an organismNodes --The points of branching within a cladogram.
149CladesCan be nested within larger clades, but not all groupings or organisms qualify as cladesMONOPHYLETIC (Only VALID clade)taxon includes all descendent species along with their immediatecommon ancestorPOLYPHYLETIC(b) taxon includes species derived from two different immediateancestorsPARAPHYLETIC(c) taxon includes species A without incorporating all other descendants
150Evolutionary Classification Phylogeny - evolutionary history of a group of organismsCladistics – The study of evolutionary relationships between groups to construct their family tree based on charactersDerived characters – Characteristics which appear in recent parts of a lineage but NOT in its older members (Evolutionary innovation)
151Most recent common ancestor – The ancestral organism from whicha group of descendants arose.
154Cladistics Vocabulary A shared primitive characterIs a homologous structure that predates the branching of a particular clade from other members of that cladeIs shared beyond the taxon we are trying to defineA shared derived characterIs an evolutionary novelty unique to a particular clade
155Systematists use a method called outgroup comparison To differentiate between shared derived and shared primitive characteristicsOutgroup comparisonIs based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor
156Cladistics Vocabulary Ingroup -- In a cladistic analysis, the set of taxa which are hypothesized to be more closely related to each other than any are to the outgroup.
159SystematistsCan never be sure of finding the single best tree in a large data setNarrow the possibilities by applying the principles of maximum parsimony and maximum likelihoodThe most parsimonious tree is the one thatrequires the fewest evolutionary events tohave occurred in the form of shared derivedcharacters
160Applying parsimony to a problem in molecular systematics HumanMushroomTulip40%30%(a) Percentage differences between sequences
161Sometimes there is compelling evidence The principle of maximum likelihoodStates that, given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary eventsLizardFour-chambered heartBirdMammal(a) Mammal-bird clade(b) Lizard-bird cladeSometimes there is compelling evidenceThat the best hypothesis is not the most parsimonious
162Gene duplicationIs one of the most important types of mutation in evolution because it increases the number of genes in the genome, providing further opportunities for evolutionary changesHomeotic or Hox genes, when duplicated can lead to new appendage arrangement (Vertebrate Evolution from Invertebrates)
163The tree of lifeIs divided into three great clades called domains: Bacteria, Archaea, and EukaryaThe early history of these domains is not yet clearArchaeaBacteriaEukarya
164The evolution of vertebrates from invertebrate animals Was associated with alterations in Hox genesThe vertebrate Hox complex contains duplicates of many of the same genes as the single invertebrate cluster, in virtually the same linear order on chromosomes, and they direct the sequential development of the same body regions. Thus, scientists infer that the four clusters of the vertebrate Hox complex are homologous to the single cluster in invertebrates.5First HoxduplicationSecond HoxVertebrates(with jaws)with four Hox clustersHypothetical earlyvertebrates(jawless)with two HoxclustersHypotheticalvertebrateancestor(invertebrate)with a singleHox clusterMost invertebrates have one cluster of homeotic genes (the Hox complex), shown here as colored bands on a chromosome. Hox genes direct development of major body parts.1A mutation (duplication) of the single Hox complex occurred about 520 million years ago and may have provided genetic material associated with the origin of the first vertebrates.2In an early vertebrate, the duplicate set of genes took on entirely new roles, such as directing the development of a backbone.3A second duplication of the Hox complex, yielding the four clusters found in most present-day vertebrates, occurred later, about 425 million years ago. This duplication, probably the result of a polyploidy event, allowed the development of even greater structural complexity, such as jaws and limbs.4