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)