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JJA Obico, Instructor, Department of Biology

Natural TheologyPhilosophy dedicated to discovering the Creator’s plan by studying nature

Classify species in order to reveal y pthe steps of life that God had created

Carolus Linnaeus - sought to discover order in the diversity of life- founder of Taxonomy

Jean Baptiste LamarckIn-charge of invertebrate collection at the Natural History Museum in Paris

Compared current species toCompared current species to fossil forms

Use and DisuseInheritance of Acquired Characteristics

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Biological EvolutionDescent with modificationCharles Darwin and Alfred Wallace

Descent- Transfer of genetic material to offspring overtimea. Clonal reproduction (asexual)b. Sexual reproduction

Biological Evolution

Modification- Change in genetic material- Mutation; genetic

recombinationrecombination

What evolves?

Population- A group of individuals of the same species

usually geographically delimited and typically have a significant amount of gene exchangeexchange

Species- Consists of group generally intergrading,

interbreeding populations that are reproductively isolated from other groups

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Mechanisms of Evolution

Genetic DriftMutationGene flowN d tiNon random matingNatural Selection

Population Genetics (PopGen)

Study of behavior of genes in the populationGenetics + EvolutionMendel (1866); Darwin and WallaceMendel (1866); Darwin and Wallace (1858)

Population 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 a. T inc; t dec?b. T dec; t inc?c. Freq does not change

Hardy-Weinberg Equilibrium

Frequency of alleles will remain the same under the following conditions:

1. Size of population is large2 No mutations2. No mutations3. No migrations4. Mating is random5. Natural selection does not take place

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Genetic Drift

- Change of frequency of alleles over time due to chance

a. Bottleneck effect- occurs when a catastrophic event pdrastically and nonselectively reduces size of population

b. Founder effect- small no. of individuals colonize a new area

Mutations

Alter the nucleotide sequence of genesMay give an selective advantage in a particular environment

eg Tolerance to a toxic metaleg. Tolerance to a toxic metal

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Gene Flow

Movement of alleles form one population to anotherPollen, seeds, fruitsRunners or horizontal stemsRunners or horizontal stems

Mating is random

Individuals mate without regard to genotypeNonrandom matingSelf fertilization- Self fertilization

- Assortative mating- outcome of pollinator preferenceeg. Hawkmoths prefer to feed on flowers with long corolla tube

Natural selection

Thomas Malthus- Population of organisms tend to

increase geometricallyGeometric progression:- Geometric progression: 2,4,8,16,32,64…

- Resources are limited

Individual variation within species

Mutation Crossing overRecombinationTTransposons- DNA sequences - have the ability to move from place to place in chromosomes

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Natural selection

Individuals that are best adapted to their environment have the greatest chance of surviving and successfully reproducingp g

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Certain traits that are common among individuals- provide superior adaptation in environmentenvironmentLess common traits- do not confer selective advantage

Tropical Forests

Lack of windLow light intensity

Pl tPlants- Undivided leaves, large, with acumen

Competition for resources is NOT necessary for natural selection to occurNatural selection may occur if certain individuals produce more offspring thanindividuals produce more offspring than others

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Modes of natural selectionStabilizing selection- eliminates extreme phenotypes

Directional selection- shifts the average or typical in one direction by favoring one of the extreme phenotypesy g p yp- leads to ANAGENESIS or phyletic evolution

Diversifying selection- splits a population into 2 parts favoring both extremes of phenotypic range- leads to CLADOGENESIS or branching evolution

Artificial selection

Selectively breeding plants or animals to favor the production of offspring with desirable traits

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Evolution can occur rapidly

Punctuated equilibriumEldredge and Gould, 1972punctuated with short periods of rapid changechangeFew year or thousand of yearseg. -Colonization of mine tailings by plants

Co-evolution

a change in the genetic composition of one species in response to a genetic change in anotherPlants and insects

Speciation

Formation of new species from preexisting speciesUltimate result of evolution

Biological Species ConceptBiological Species Concept- A population whose members have the

potential to interbreed with one another in nature to produce viable, fertile offspring but who cannot produce viable, fertile offspring with members of other species

- Reproductively isolated from other populations

Reproductive isolation

Prezygotic- Sperm does not fertilize egg from other

populationNo zygote is formed- No zygote is formed

Postzygotic- Zygote or embryo does not survive or

adult is infertile

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PrezygoticTemporal isolation

SeasonalDiurnal

Ecological – eg. Acerblack maple (Acer nigrum)- dry, high Cablack maple (Acer nigrum) dry, high Casugar maple (A. saccharum)- acidic

Self fertilizationFloral

Behavioral- restriction to one pollinatorStructural – white and red petaled flower

Pollen-pistil incompatibility

Post 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

Hybrid breakdown- problems in later generation of hybrids

Modes of speciation

Allopatric speciationGeographical barrier that physically isolates populations hinders gene flow

Sympatric speciationSympatric speciationIntrinsic factors alter gene flow

Allopatric speciation

geographical barriers: mountain range, oceans, lakes, creeping glaciers

Adaptive radiationWhen a species move into previously- When a species move into previously unoccupied environment (island or occupied environment with many opportunities to succeed)

- Scalesia spp. in Galapagos Islands

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Sympatric Speciation

Occurs within the range of parent populationsPolyploidy- more than 2 complete sets of pchromosomes; common in plants- oats, cotton, potatoes, tobacco, wheat

a. Autopolyploid- from single speciesb. Allopolyploid- 2 different species

- more vigorous than parents