The processesprocesses that have transformed life on earth from it’s earliest formsearliest forms to the vast diversitydiversity that characterizes it today.

A changechange in the genes!!!!!!!!genes!!!!!!!!

Jean Baptiste LamarckJean Baptiste Lamarck (early 1800’s) proposed:

““The inheritance of acquired The inheritance of acquired characteristics”characteristics”

He proposed that by using or not using its body parts, an individual tends to developdevelop certain characteristicscharacteristics, which it passespasses on to its offspringoffspring.

Example:Example:A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

Influenced by Charles LyellInfluenced by Charles Lyell who published “Principles of “Principles of Geology”.Geology”.

This publication led DarwinDarwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.

Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831-1836) to survey the south seas (mainly (mainly South America and the Galapagos South America and the Galapagos Islands)Islands) to collect plants and animals.

On the Galapagos Islands, Galapagos Islands, Darwin observed species that lived no where else in the world.

These observations led Darwin to write a book.

Wrote in 1859Wrote in 1859: “On the Origin of “On the Origin of Species by Means of Natural Selection”Species by Means of Natural Selection”

Two main points:Two main points:

1.1. Species were not created in their Species were not created in their present form, but evolved from present form, but evolved from ancestral species.ancestral species.

2.2. Proposed a mechanism for Proposed a mechanism for evolution:evolution: NATURAL SELECTIONNATURAL SELECTION

IndividualsIndividuals with favorablefavorable traitstraits are more likely to leave more offspring better suited for their environmentenvironment.

Example:Example:English peppered moth (English peppered moth (Biston betularia))

- light and dark phases- light and dark phases

The selective breedingselective breeding of domesticated plants and animals by man.

Question:Question:What’s the ancestor of the domesticated dog?

Answer:Answer: WOLFWOLF

1.1. Biogeography: Biogeography:

Geographical distribution of Geographical distribution of species.species.

2. Fossil Record:2. Fossil Record:

Fossils and the order in which Fossils and the order in which they appear in layers of they appear in layers of sedimentary rock sedimentary rock (strongest (strongest evidence).evidence).

Fossilized Trilobite

Fossils:•Formed when animal remains are trapped in sedimentary layers.

•Organic material replaced by minerals over millions of years.•Result is a "mineral cast" of the dead organism.•Where a fossil is located in the sedimentary strata can indicate it's age.

•Successive changes in fossil forms of an organism can help in developing a fossil record of an organism's evolution.•Some rare fossils can show "soft tissues" which give invaluable information on an organism's physiology

•Example: paleontologists recently discovered a dinosaur with a fossilized heart. This indicates that this species was most likely warm blooded. Fossilized Dinosaur Heart

3. Taxonomy:3. Taxonomy:

Classification of life forms.Classification of life forms.

4. Homologous structures:4. Homologous structures:Structures that are similar Structures that are similar

because of because of common ancestry common ancestry (comparative anatomy)(comparative anatomy)

Refers to the fact that organisms' structures are formed from similar anatomy.

Example the wing of a bird, arm of a man, wing of a bat, and flipper of a whale, all appear to be formed from a common set of bones.

Implies that these organisms evolved from some common ancestor.

5. Comparative embryology:5. Comparative embryology:

Study of structures that appear Study of structures that appear during during embryonic development.embryonic development.

6. Molecular biology:6. Molecular biology:

DNA and proteins (amino acids)DNA and proteins (amino acids)

In early embryological development, it appears that embryos "play out" their evolutionary history.

Known as Ontonogy recapitulating Phylogeny.

Implies that genetically, we have not "forgotten" our evolutionary history, only built upon it.

7. Vestigial Structures7. Vestigial Structures

Remnants of Remnants of

structures used in structures used in

the past.the past.

The sciencescience of genetic genetic changechange in population.

A localized group of individualsindividuals belonging to the same speciessame species.

A group of populationspopulations whose individualsindividuals have the potential to interbreedinterbreed and produce viableviable offspring.

The total collection of genescollection of genes in a population at any one time.

The origin of taxonomic groups higher than the species higher than the species levellevel.

Includes the origin of the universe.

A change in a population’s population’s gene poolgene pool over a secession of generations.

Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.

1. Genetic drift:1. Genetic drift:

Change in the gene pool Change in the gene pool of a of a small population due small population due to chance.to chance.

Two examples:Two examples:

a. Bottleneck effecta. Bottleneck effect

b. Founder effectb. Founder effect

2. Gene Flow:2. Gene Flow:

TThe gain or loss of allelesgain or loss of alleles from a population by the movementmovement of individuals or gametes.

Immigration or emigrationImmigration or emigration.

3. Mutation:3. Mutation:

Change in an organism’s DNA Change in an organism’s DNA that creates a new allele.that creates a new allele.

4. Non-random mating:4. Non-random mating:

The selection of mates other The selection of mates other thanthan by chance.by chance.

5. Natural selection:5. Natural selection:

Differential reproduction.Differential reproduction.

Natural selectionNatural selection has three three modesmodes of action:1.1. Stabilizing selectionStabilizing selection

2.2. Directional selectionDirectional selection

3.3. Diversifying selectionDiversifying selection

Number ofIndividuals

Size of individualsSmall Large

ActsActs upon extremesextremes and favorsfavors the intermediateintermediate.

Number ofIndividuals

Size of individualsSmall Large

FavorsFavors variants of one one extremeextreme.

Number ofIndividuals

Size of individualsSmall Large

FavorsFavors variants of opposite opposite extremesextremes. AKA Disruptive Selection

Number ofIndividuals

Size of individualsSmall Large

The evolutionevolution of new species.

Any mechanismmechanism that impedesimpedes two species from producing fertile and/or viable hybrid fertile and/or viable hybrid offspringoffspring.

Two barriers:Two barriers:

1.1. Pre-zygotic barriersPre-zygotic barriers

2.2. Post-zygotic barriersPost-zygotic barriers

a. Temporal isolation:a. Temporal isolation:Breeding occurs at different times for different species.

b. Habitat isolation:b. Habitat isolation:Species breed in different habitats.

c. Behavioral isolation:c. Behavioral isolation:Little or no sexual attraction between species.

d. Mechanical isolation:d. Mechanical isolation:Structural differences prevent

gamete exchange.

e. Gametic isolation:e. Gametic isolation:Gametes die before uniting with gametes of other species, or

gametes fail to unite.

a. Hybrid inviability:a. Hybrid inviability:Hybrid zygotes fail to develop or fail

to reach sexual maturity.

b. Hybrid sterility:b. Hybrid sterility:Hybrid fails to produce functional

gametes.

c. Hybrid breakdown:c. Hybrid breakdown:Offspring of hybrids are weak or

infertile.

Emergence of numerous Emergence of numerous speciesspecies from a common common ancestorancestor introduced to new and diverse environments.

Aka – Divergent evolution

Example:Example:

Darwin’s FinchesDarwin’s Finches

SpeciesSpecies from different evolutionary branchesevolutionary branches may come to resemble one another if they live in very similar environments.very similar environments.

Example:Example:1.1. Ostrich (Africa) and Emu (Australia).Ostrich (Africa) and Emu (Australia).2.2. Sidewinder (Mojave Desert) andSidewinder (Mojave Desert) and

Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)

By contrasting North By contrasting North American placental mammals American placental mammals with Australian marsupials. with Australian marsupials. One can see how One can see how convergence and divergence convergence and divergence works together. works together. •In each case an ancestor In each case an ancestor mammal evolved into several mammal evolved into several ecological niches.ecological niches.•Since each niche required a Since each niche required a specific phenotype, what specific phenotype, what results are 2 groups of results are 2 groups of mammals which have NEVER mammals which have NEVER made contact, evolving into made contact, evolving into similar shapes.similar shapes.

Evolutionary changeEvolutionary change, in which one species act as a selective selective forceforce on a secondsecond species, inducing adaptations that in turn act as selective force on the firstfirst species.

Example:Example:1.1. Acacia ants and acacia treesAcacia ants and acacia trees2.2. Humming birds and plants with Humming birds and plants with flowers flowers with long tubeswith long tubes