evolution with phylogeny
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JJA Obico, Instructor, Department of Biology
Natural TheologyNatural TheologyPhilosophy dedicated to p ydiscovering the Creator’s plan by studying nature
Classify species in order to reveal the steps of life that God had createdcreated
Carolus Linnaeus - sought to discover order in the diversity of life- founder of Taxonomy- founder of Taxonomy
Jean Baptiste LamarckJean Baptiste LamarckIn-charge of invertebrate collection at the Natural History Museum in Paris
Compared current species to fossil formsfossil forms
Use and DisuseUse and DisuseInheritance of Acquired Characteristics
Biological EvolutionBiological EvolutionDescent with modificationCharles Darwin and Alfred WallaceCharles Darwin and Alfred Wallace
Descent- Transfer of genetic material to offspring overtimeg p ga. Clonal reproduction (asexual)b. Sexual reproduction
Biological EvolutionBiological Evolution
ModificationModification- Change in genetic material
Mutation; genetic- Mutation; genetic recombination
What evolves?What evolves?
Populationp- A group of individuals of the same species
usually geographically delimited and i ll h i ifi ftypically have a significant amount of gene
exchange
Species- Consists of group generally intergrading- Consists of group generally intergrading,
interbreeding populations that are reproductively isolated from other groups
Mechanisms of EvolutionMechanisms of Evolution
Genetic DriftGenetic DriftMutationGene flowGene flowNon random matingNatural Selection
Population Genetics (PopGen)Population Genetics (PopGen)
Study of behavior of genes in theStudy of behavior of genes in the populationGenetics + EvolutionGenetics + EvolutionMendel (1866); Darwin and Wallace (1858)(1858)
Population GeneticsPopulation Genetics
Evolution - A change in the frequency of alleles in a
population over time
1000 garden peas; 2000 alleles (TT, Tt or tt)T= 1000; t= 1000 freq of each allele= 0.5What happens when
T i d ?a. T inc; t dec?b. T dec; t inc?
F d t hc. Freq does not change
Hardy-Weinberg EquilibriumHardy Weinberg Equilibrium
Frequency of alleles will remain the sameFrequency of alleles will remain the same under the following conditions:
1 Size of population is large1. Size of population is large2. No mutations3 N i ti3. No migrations4. Mating is random5. Natural selection does not take place
Genetic DriftGenetic Drift
- Change of frequency of alleles over timeChange of frequency of alleles over time due to chance
a. Bottleneck effect- occurs when a catastrophic event drastically and nonselectively reduces size of population
b. Founder effect- small no. of individuals colonize a new area
MutationsMutations
Alter the nucleotide sequence of genesAlter the nucleotide sequence of genesMay give an selective advantage in a particular environmentparticular environment
eg. Tolerance to a toxic metal
Gene FlowGene Flow
Movement of alleles form one populationMovement of alleles form one population to anotherPollen seeds fruitsPollen, seeds, fruitsRunners or horizontal stems
Mating is randomMating is random
Individuals mate without regard toIndividuals mate without regard to genotypeNonrandom matingNonrandom mating
- Self fertilizationA t ti ti t f- Assortative mating- outcome of pollinator preference
H k th f t f d fleg. Hawkmoths prefer to feed on flowers with long corolla tube
Natural selectionNatural selection
Thomas MalthusThomas Malthus- Population of organisms tend to
increase geometricallyincrease geometrically- Geometric progression:
2 4 8 16 32 642,4,8,16,32,64…- Resources are limited
Individual variation within species
MutationMutation Crossing overRecombinationRecombinationTransposons- DNA sequences - have the ability to move from place to place in chromosomes
Natural selectionNatural selection
Individuals that are best adapted to theirIndividuals that are best adapted to their environment have the greatest chance of surviving and successfully g yreproducing
Certain traits that are common amongCertain traits that are common among individuals- provide superior adaptation in- provide superior adaptation in environmentLess common traits- do not conferLess common traits- do not confer selective advantage
Tropical ForestsTropical Forests
Lack of windLack of windLow light intensity
Plants- Undivided leaves, large, with acumen
Competition for resources is NOTCompetition for resources is NOT necessary for natural selection to occurNatural selection may occur if certainNatural selection may occur if certain individuals produce more offspring than othersothers
Modes of natural selectionModes of natural selectionStabilizing selection- eliminates extreme phenotypesp yp
Directional selectionshifts the average or typical in one direction- shifts the average or typical in one direction
by favoring one of the extreme phenotypes- leads to ANAGENESIS or phyletic evolution
Diversifying selection- splits a population into 2 parts favoring both- splits a population into 2 parts favoring both extremes of phenotypic range- leads to CLADOGENESIS or branching evolutionevolution
Artificial selectionArtificial selection
Selectively breeding plants or animals toSelectively breeding plants or animals to favor the production of offspring with desirable traits
Evolution can occur rapidlyEvolution can occur rapidly
Punctuated equilibriumPunctuated equilibriumEldredge and Gould, 1972punctuated with short periods of rapidpunctuated with short periods of rapid changeF th d fFew year or thousand of yearseg. -Colonization of mine tailings by plants
Co-evolutionCo evolution
a change in the genetica change in the genetic composition of one species in response to a genetic change p g gin anotherPlants and insectsPlants and insects
SpeciationSpeciation
Formation of new species from preexisting p p gspeciesUltimate result of evolution
Biological Species ConceptA population whose members have the- A population whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring but
h t d i bl f til ff iwho cannot produce viable, fertile offspring with members of other species
- Reproductively isolated from other populationsReproductively isolated from other populations
Reproductive isolationReproductive isolation
PrezygoticPrezygotic- Sperm does not fertilize egg from other
populationpopulation- No zygote is formed
Postzygotic- Zygote or embryo does not survive or
adult is infertile
PrezygoticPrezygoticTemporal isolationp
SeasonalDiurnal
Ecological eg AcerEcological – eg. Acerblack maple (Acer nigrum)- dry, high Casugar maple (A. saccharum)- acidic
Self fertilizationFloral
Behavioral restriction to one pollinatorBehavioral- restriction to one pollinatorStructural – white and red petaled flower
Pollen-pistil incompatibilityp p y
Post zygoticPost zygotic
Inviable seedHybrid inviability- not reach reproductive maturityHybrid floral isolation – no pollinatorsHybrid sterility
Chromosomes do not pair during meiosisBrocolli (Brassica oleracea) x radish (Raphanussativus) Raphanobrassica) p
Hybrid breakdown- problems in later generation of hybrids
Modes of speciationModes of speciation
Allopatric speciationAllopatric speciationGeographical barrier that physically isolates populations hinders gene flowp p g
Sympatric speciationIntrinsic factors alter gene flowIntrinsic factors alter gene flow
Allopatric speciationAllopatric speciation
geographical barriers: mountain rangegeographical barriers: mountain range, oceans, lakes, creeping glaciers
Adaptive radiationAdaptive radiation- When a species move into previously
unoccupied environment (island orunoccupied environment (island or occupied environment with many opportunities to succeed)opportunities to succeed)
- Scalesia spp. in Galapagos Islands
Sympatric SpeciationSympatric Speciation
Occurs within the range of parentOccurs within the range of parent populationsPolyploidyyp y- more than 2 complete sets of chromosomes; common in plants- oats, cotton, potatoes, tobacco, wheat
a. Autopolyploid- from single speciesb. Allopolyploid- 2 different species
- more vigorous than parentsg p
What is phylogeny?Evolutionary history or pattern of descent
What is phylogenetic systematics (cladistics)?(cladistics)?
Branch of systematics concerned with inferring phylogenyphylogeny
Lines on cladogram? Lineage = sequence of ancestral-descendentLineage sequence of ancestral descendent
populations through time; represent descent
Split, from one lineage into two?
Divergence, which may lead to speciation
Pre-existing feature? gPrimitive / Ancestral / Plesiomorphic
New feature?New feature? Advanced / Derived / Apomorphic
PheneticPhenetic- classification based on overall similaritiessimilarities- common to everyone
Phylogeneticclassification based on evolutionary - classification based on evolutionary
history or pattern of descent
Can be arbitrary Can be arbitrary, e.g., classify these:
Represented in the form of a cladogram/ Represented in the form of a cladogram/ phylogenetic treeCladogramCladogram• Lines- lineage or clades; denote descent• Branching- divergence from a common ancestorBranching divergence from a common ancestor
Evolution recognized as a change from pre-existing character state(ancestral) to pre existing character state(ancestral) to a new (derived) character state
All of life is interconnected by All of life is interconnected by
TAXA descentdescent
A B C D E F
TIME
lineage or clade
TIME
Cladogram or Phylogenetic TreeCladogram or Phylogenetic Tree
A B C D E F TAXA
TIME
speciation
Cladogram or Phylogenetic Tree
CladisticsCladisticsMethodology of inferring the pattern of evolutionary history of a group of evolutionary history of a group of organisms using apomorphic characters
Ancestral characterPleisiomorphy- Pleisiomorphy
Derived character- Apomorphy- Apomorphy
Apomorphies the result of evolutionApomorphies - the result of evolution.
Taxa sharing apomorphies underwent Taxa sharing apomorphies underwent same evolutionary history,should be grouped togethershould be grouped together.
A B C D E F
TAXA
Apomorphiesf B&C
Apomorphyfor taxon D
for taxa B&C
TIME
Apomorphyfor taxa B-F
Cladogram or Phylogenetic Tree
Common ancestry
TAXA
A B C D E F
TIME
common ancestor (of taxon D, E, & F)
Cl d Ph l ti T
common ancestor (of taxon A & taxa B-F)
Cladogram or Phylogenetic Tree
Similarity due to common ancestry- similar DNA sequences
Intraindividual homology?gy
Similarity by common ancestry of features within an individual e g carpels and leavesan individual, e.g., carpels and leaves(common ancestry by genes)
Similarity not by common ancestry.
Types?
Convergence independent evolution of a Convergence - independent evolution of a similar feature in 2 or more lineages.
Reversal - loss of a derived feature with re-establishment of ancestral featureestablishment of ancestral feature.
Convergence - Stem succulence and “spines” in Cactaceae and Euphorbia sppCactaceae and Euphorbia spp.
Reversal - Loss of perianth in Lemna, Wolffia.
Recognized group in phylogeneticRecognized group in phylogeneticsystematicsConsisting of a common ancestor plus all Consisting of a common ancestor plus all of its descendantsSequential listing of monophyletic groupSequential listing of monophyletic group- serve as a phylogenetic classification schemescheme
A B C D E F TAXA
monophyletic group
TIME
t
common ancestor (of taxon A & taxa B-F)
common ancestor (of taxon D, E, & F)
Cladogram or Phylogenetic Tree
Consisting of a common ancestor but not Consisting of a common ancestor but not all descendants of that common ancestor
Two or more separate groups each with a separate common ancestor
A B C D E F TAXA
TIME
common ancestor (of taxon A & taxa B-F)
common ancestor (of taxon D, E, & F)
Cladogram or Phylogenetic Tree
A B C D E FTAXA
A B C D E F
TIME
common ancestor ( f t A & t B F)
common ancestor (of taxon D, E, & F)
Cladogram or Phylogenetic Tree
(of taxon A & taxa B-F)
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