Evolution And The Origin Of Species

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Cuvier

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• Anatomist

• Paleontologist

• Theory ofCatastrophism: Earth’s historycharacterized bycatastrophes,eliminating manyspecies (nowfossils)

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Buffon

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original creation with few species,followed by modern species conceived bynature and produced by time

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Lamarck:

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inheritance of acquiredcharacteristics. Changes in body form andfunction during an individual’s life arepassed on to its offspring. (Importance ofthe environment).

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Lamarck (19th century)

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• Environmentalpressure brings about

permanent change inan individual’s body

• The acquiredcharacteristics arepassed on to offspring

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Charles Lyell (17

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• Darwin read his bookPrinciples of Geology,which re-introducedthe Theory ofUniformitarianism ofJames Hutton.

• Presently observablegeological processeswere adequate toexplain geologicalhistory

• The Earth is very old

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What is the process that leads tomodification?

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Individuals differ in their ability to surviveand reproduce

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Steps in evolution of speciesFour Postulates of Darwin

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Postulate 1:

Individual members of a population differ

from oneanother in many respects

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Steps in evolution of species Four Postulates of Darwin

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Postulate 2: Some of the differences among members of apopulation are due to

characteristics that may be passed on tooffspring

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Steps in evolution of species Four Postulates

of Darwin

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Postulate 3: In each generation some

individuals in a populationsurvive and reproduce successfully but others do not

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Steps in evolution of species Four Postulates

of Darwin

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Postulate 4:

Natural selection: Individuals with advantageous traits survive longest and leave the most offspring

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Evidence for Evolution

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1. Fossils

2. Comparative anatomy

3. Embryological similarity

4. Biogeography

5. Modern biochemical andgenetic analysis

6. Studies on living populations

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Convergent Evolution

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Some anatomical similarities are the resultof evolutionary forces on different kinds of organisms under similar environments: Convergent evolution It can lead to structures with similarfunctions but different ancestry(analogous structures)

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Paedomorphosis

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retention ofjuvenile bodyfeatures in theadult Skull developmentof chimpanzeesand humans isalmost similar. Differences ingrowth late, onlyafter baby is born.

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Evidence from comparativemolecular biology

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1. All cells use DNA as the carrier of geneticinformation

2. All cells use RNA and approximately thesame genetic code to translate geneticinformation into proteins

3. All cells use roughly the same set of 20amino acids to build proteins

4. All cells use ATP as a cellular energycarrier

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Bear Phylogeny

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Relatedness between bears based on their DNA similarities (DNA-DNA hybridization)

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Evidence for evolution fromstudies on living populations

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1.Build-up of resistance of bacteria against antibiotics

2.Build-up of resistance of insects and otherorganisms against pesticides

3.The evolution of HIV

4.Population studies on present-day Darwin’s finches

5.Population studies on guppies

6.Stickleback populations

7.Embryology studies, evo-devo

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What is a Species?

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All individuals that potentially

caninterbreed in nature and produce fertile

offspring are considered to belong toone species

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Speciation: formation of new species

How are new species formed?

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Sexual reproduction important aspect ofa species.

For speciation to occur, a barrier forsexual reproduction must appear.

A population must break up andindividuals between the new populationsmust not be able to interbreed.

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Allopatric speciation

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Speciation in subpopulations of a species

that is split geographically.

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What does Allopatric speciation require?

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Requires two conditions:

1: Isolation of subpopulations

2. Genetic divergence of subpopulations

Then follows: No more exchange of genesbetween subpopulations, leading togenetic divergence Allo (“different”) and patria (“fatherland”)

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Geographical separation

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a natural division splits a population intwo or more groups (sub-populations)

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Examples of Geographical Separation

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Examples: Coral reefs separated by miles of oceans Mountain tops Meandering rivers separate populations Climate change leading to patches of forestsseparated by savannas Continental driftDispersal: migrationExample:Population might colonize an island

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Sympatric speciation

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Species formation within the homerange of an existing species Sym (“same), patria (“fatherland”)Examples:CichlidsMany plants

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Causes for sympatric speciation

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Chromosomal error during cell division likenondisjunction: chromosomes do not separateduring Anaphase I or II. Nondisjunction is followed by aneuploidy: cells withtoo many or not enough chromosomes Polyploidy: entire set of chromosomes does notseparate during meiosis and offspring has doublethe amount of chromosomes: 4 (or more) sets ofchromosomes 2. Ecological barriers or habitat differences:individuals live in the same area but occupy adifferent niche (have different ways of living)

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Isolating mechanisms prevent species from interbreeding

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1. Geographical or habitat isolation

2. Pre-mating isolating mechanism: Ecological Each species of fig wasps live in their own species of figs isolation

3. Temporal reproductive isolation

4. Behavioralisolation

5. Pre-matingisolatingmechanism • Mechanicalisolation:

6. Mating occurs but sperm cannotfertilize egg Among many animals that releasesperm and eggs in water Among many plants that receive pollenfrom other plants

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Post-mating or PostzygoticIsolating MechanismHybrid inviability

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Mating takes place resulting infertilized

egg Embryo does not survive:

hybridinviability Examples among frogs

Post-mating isolating mechanism hybrid

infertility in mules (or hinnies)

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Models of speciation

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Gradual model of speciation: many smallmorphological changes over long spans oftime Ex. Fossil sequences of foraminifers,ammonites, mice Punctuation model of speciation: manychanges in a short period of time,alternated with periods of little change Ex. Adaptive radiations after massextinctions

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Evolutionary

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Tree Summarizes information about the continuity and branching of relationships among species

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Extinction

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The ultimate fate of each species 99.9% of all species that ever existed arenow extinct Some causes:Habitat, environmental, changeCompetition from other speciesOverspecialization Now: habitat destruction and pollution byhumans

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New species are still discovered even relativelylarge ones such as this Golden Palace monkey

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yes

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What were the observations that Darwin had during his trip and led him to dig in to evolution?

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1. Life is very diverse

2. Fossils living in certain areas resemble living organisms from the same areas

3. Organisms have adaptations to their enviromnment.

4. some organisms like snake have non functional remanants that are functional in other organisms

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the idea of the selectivity of nature led to 4 postulates of Darwin. What are they?

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1. All offspring show variations in traits, this might affect the individual's ability to secure

resources.

2. some of the differences are due to the fact tha t some traits are passed to offspring. (All organisms have potential to produce more traits than the environment can support.

3. In each generation some individulas survive and reproduce while others dont.

4. Individuals with advantageous traits survive the longest and leave the most offspring.

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what are the evidences for evolution

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1. Fossils

2. Comparative anatomy

3. Biogeography

4. Embryological similarity

5. Modern biochemical and genetic analysis

6. Studies on living populations

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Fossils

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We now have many series of fossils. Example: The evolution of whales from land dwellers to modern marine organisms. 2. The evolution of humans, horses, amphibians and birds based on fossils.

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Comparative anatomy

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Homologous Structures: This are body

structures that are similar in anatomy but

different in function, this is due to evolving from a common ancestor.

Vestigal structures: this are structures with

no apparent function inherited from

a common ancesotr.

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Convergent Evolution

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Some anatomical similarites is due to evolutionary forces on different kinds of organisms under similar enviornment. This leads to analogous strctures.

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Analogous structres

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Are structures with similar functions but different ancestory. Example is wings of birds and insects.

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Biogeography

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distribution of organisms can be explained through geological past.

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Embryological stages

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. Early embryos of vertebrates all resemble one another. They inherited the same plan for development. Skull development in the embryos of chimpanzees and humans is almost similar. Differences develop after baby is born.

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Evidence from comparative molecular biology

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1. All cells use DNA as the carrier of genetic information

2. All cells use RNA and approximately the same genetic code to translate genetic information into proteins

3. All cells use roughly the same set of 20 amino acids to build proteins

4. All cells use ATP as a cellular energy carrier

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Molecular similarity shows evolutionary

relationships. Examples are:

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1. The DNA sequences of the genes that code for cytochrome c in a human and a mouse

2. Evolutionary relationships between vertebrates based on protein similarities: hemoglobin3. Bear Phylogeny: relatedness between bears based on their DNA similarities (DNA-DNAhybridization)

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Evidence for evolution from studies on living populations We can observe evolution at work:

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1. Build-up of resistance of bacteria against antibiotics.

2. Build-up of resistance of insects and other organsims against pesticides.

3. The evolution of HIV

4. Population studies on presnt-day Darwin's finches

5. Population studies on guppies

6. Poplutaiton studies on Anole Lizards

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What is a species?

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All indviduals that potentailly can interbreed in nature and produce fertile offspring are considered to belong to one species. (Appearance doesnt matter, for example dog breeds look different but belong to the same species.)

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Whats an important aspect of species?

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sexual reproduction.

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What has to happen for a speciation to occur?

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A barrier for sexual reproduction must appear. A population must break up and indviduals between the new populations must not be able to interbreed.

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Allopatric Speciation

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This is a speciation in sub populations of a species that is split geographically. It requires two conditions: 1. Isolation of subpopulations.

2. Genetic divergence of subpopulations.

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Allopatric

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Allo means different Patric means fatherland. Therefore different fatherland. that is speciation in sub populations of a species that is split geographically. It requires 1. Isolation of sub populations. 2. Genetic divergergence of sub poplutations.

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Vicariance

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is a natural division that splits a population in two or more groups (sub-populations).

Coral reefs separated by miles of oceansMountain topsMeandering rivers separate populationsClimate change leading to patches of forests separated by savannasContinental drift

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Dispersal

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inhabit geographically separate locations with different climates andecosystems.

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Allopatric Speciation and Adaptive Radiation

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From one original species, multiple others evolved, each with its own distinctive characteristics. Examples are the honeycreeper birds on Hawaii and the 30 species of silversword plants on Hawaiian Islands. All descended from one ancestral population (from California). The Darwin finches on the Galapagos also are an example of allopatric speciation and adaptive radiation.

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Sympatric speciation

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Species formation within the home range of an existing species. Sym means “same” and patriameans “fatherland”

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Causes for sympatric speciation

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1. hromosomal error during cell division like nondisjunction: Aneuploidy: cells with too many or not enough cromosomes.

Polyploidy: entire set of chromosomes doesnt separate during meiosis 1.

2. Ecological barriers or habitat differences: individuals live in the same area but occupy adifferent niche (have different ways of living).

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Aneuploidy

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gametes have too many or too few chromosomes . (2n+1) Trisomy and Monomsomy (2n-1)

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Polyploidy

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the result of non disjunction. Autopolyploidy results when meiosis occurs with out chromosome separation. gametes are diploid. (Plant self fertilizes and the offspring has four sets of chromosmes)

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Alloploidy

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two different species mate to produce viable offspring.

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Sympatric isolation through different niches

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Individuals of one species might begin to use another food source. They diverge geneticallyfrom the original one, which may lead to reproductive isolation: a new species. Differentecological requirements lead to different species.

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Reproductive Isolation

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Isolating mechanisms prevent species from interbreeding. There are many ways through whichreproductive isolation happens.

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Pre-mating isolating mechanisms

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1.geographical or habitat isolation.

2. Ecological isolation

3. temporal reproductive isolation

4.behavorial isolation

5.mechanical incompatibility. (mismatch between body parts).

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Ecological isolation.

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Species of fig wasps live in their own species of figs

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Temporal reproductive isolation

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Related frog species can exhibit temporal reproductive isolation. One reproduces earlyin the year, the other later in the year. Another example are the Bishop and Montereypine that do not interbreed as they release pollen at different times of the year.

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Behavioral isolation

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Display of correct behavior is needed for mating to take place.

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Mechanical incompatibility

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incompatibilities or mismatch between body parts The shape of the male reproductive organ varies among male damselfly species, and is only compatible with the female of that species. Reproductive organ incompatibility keeps the species reproductively isolated. Some flowers have evolved to attract certain pollinators.

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Post-mating Isolating Mechanism

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1. Gametic incompatibility

2. Hybrid inviability

3. Hybrid infertility

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Gametic incompatibility

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Mating occurs but sperm cannot fertilize eggAmong many animals that release sperm and eggs in waterAmong many plants that receive pollen from other plants

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Hybrid inviability

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Mating takes place resulting in fertilized eggEmbryo does not survive: hybrid inviability

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Hybrid Infertility

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Liger is a cross between male lion and female tiger. It cannot reproduce, therefore tigerand lion are separate species. More examples of sterile hybrids are the mule, zorse andzedonk

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Evolutionary tree of life

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Speciation leads to forking branches in the evolutionary tree of life

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Gradual model of speciation:

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many small morphological changes over long spans of time. Examples are fossil sequences of foraminifers, ammonites and mice.

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What are the models of speciation

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1. Gradual model of speciation

2. Punctuation model of speciation

3. Evolutionary Tree

4.Extinction

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Gradual model of speciation.

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many small morphological changes over long spans of time. Examples are fossil sequences of foraminifers, ammonites and mice.

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Punctuation model of Speciation .

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many changes in a short period of time, alternated withperiods of little change. Examples are adaptive radiations after mass extinctions. Earth historyshows that both rates of speciation happen. It depends on the rate of environmental change.

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Evolutionary Tree

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Summarizes information about the continuity and branching of relationships among species

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Extinction

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is the ultimate fate of each species and 99.9% of all species that ever existed arenow extinct.

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What are the causes of Extinciton

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Habitat, environmental, changeCompetition from other speciesOverspecializationNow: habitat destruction and pollution by humans New species are still discovered even relatively large ones such as the Golden Palace monkey