EvolutionEvolution part Ipart I

““The process of The process of change change

over time”over time”

Charles DarwinCharles Darwin Darwin is considered as the Darwin is considered as the

“father” of evolution“father” of evolution Losing his passion to become Losing his passion to become

a doctor in med school he a doctor in med school he took to the sea to become a took to the sea to become a “naturalist” in 1831“naturalist” in 1831– The name of the ship he spent The name of the ship he spent

5 years on was the 5 years on was the BeagleBeagle Darwin returned to England Darwin returned to England

in 1836 with pages of notes in 1836 with pages of notes from what he saw as well as from what he saw as well as many specimens from his many specimens from his journeyjourney

Charles DarwinCharles Darwin Darwin spent 36 days on Darwin spent 36 days on

the Galapagos Islands the Galapagos Islands – These islands are located These islands are located

West of the Northern part West of the Northern part of South America off the of South America off the coast of Ecuadorcoast of Ecuador

The Galapagos islands The Galapagos islands were an undisturbed were an undisturbed island chain void of island chain void of humans for thousands humans for thousands of yearsof years

What Darwin found What Darwin found astonished him!astonished him!

Charles DarwinCharles Darwin Because of Because of geographic geographic

isolationisolation, the inhabitants , the inhabitants of the Galapagos evolved of the Galapagos evolved without predatorswithout predators– This allowed humans to get This allowed humans to get

as close as they wanted to as close as they wanted to research the animalsresearch the animals

Many species were the Many species were the same species he found on same species he found on other continents but, they other continents but, they had key differences!had key differences!– For example, a species of For example, a species of

cacti normally only 5 feet cacti normally only 5 feet tall grew to heights of 20 tall grew to heights of 20 feet!feet!

And lizards swam and ate algae from the rocks

Charles DarwinCharles Darwin

One of the observations One of the observations that spawned Darwin’s that spawned Darwin’s curiosity was the amazing curiosity was the amazing similarities between similarities between animals of different animals of different species!species!

Darwin also noticed that Darwin also noticed that plants and animals had plants and animals had unique characteristics unique characteristics within the same species within the same species as well!as well!

Important Important VocabularyVocabulary Natural variationNatural variation – is defined as – is defined as

differences among individuals differences among individuals of the same speciesof the same species– Interspecific variationInterspecific variation – is variation – is variation

among individuals of the same among individuals of the same speciesspecies

– Intraspecific variationIntraspecific variation – – variation variation among individuals of different among individuals of different speciesspecies

Artificial selectionArtificial selection – artificial – artificial selection is similar to selection is similar to selective selective breedingbreeding (being “chosen”) (being “chosen”)– An example would be the selection An example would be the selection

for a mate that birds go throughfor a mate that birds go through

Important Important VocabularyVocabulary AdaptationAdaptation – any inherited – any inherited

characteristic that increases characteristic that increases and organism’s chance of and organism’s chance of survival survival – Adaptations can be a Adaptations can be a physical physical

characteristiccharacteristic or a more complex or a more complex behaviorbehavior This lizard is known as the Thorny This lizard is known as the Thorny

Devil and it lives in the harsh outback Devil and it lives in the harsh outback of Australia where there is very little of Australia where there is very little waterwater

To get water, it’s body has special To get water, it’s body has special channelschannels that lead water to the that lead water to the corners of its mouth and all it has to corners of its mouth and all it has to do is gulp to draw the moisture from do is gulp to draw the moisture from the air that has condensed on its body the air that has condensed on its body (via capillary action)(via capillary action)

Important Important VocabularyVocabulary Natural selectionNatural selection – aka. – aka. Survival Survival

of the fittestof the fittest is defined as is defined as nature nature “selecting” individuals with “selecting” individuals with characteristics making them characteristics making them well suited to their environmentwell suited to their environment– Over time, natural selection results Over time, natural selection results

in changes in the inherited in changes in the inherited characteristics of a population. characteristics of a population. These changes increase a species’ These changes increase a species’ fitness in its environment.fitness in its environment.

– http://www.greenexpander.com/2007/12/10/amazing-octopus-camouflage/http://www.greenexpander.com/2007/12/10/amazing-octopus-camouflage/

Genes and VariationGenes and Variation A group of interbreeding individuals A group of interbreeding individuals

is known as a is known as a populationpopulation The The genomegenome of an individualof an individual

organismorganism is all of the genes that is all of the genes that organism possesses worldwideorganism possesses worldwide

The The gene poolgene pool is ALL of the genes in is ALL of the genes in a population including all of the a population including all of the ‘possible’ alleles‘possible’ alleles– For example: in Basenji puppies they For example: in Basenji puppies they

can have 1 of 4 coat colorscan have 1 of 4 coat colors

The The relative frequencyrelative frequency is how often is how often that gene occurs in the gene poolthat gene occurs in the gene pool

Genes and VariationGenes and Variation Natural Selection Natural Selection and trait distributionand trait distribution

– Directional selectionDirectional selection is when individuals is when individuals in a population have a higher fitness over in a population have a higher fitness over those in the middle range or lower range those in the middle range or lower range seesee figure 16-6 pg. 398figure 16-6 pg. 398 This causes a “shift” in the fitness towards This causes a “shift” in the fitness towards

one particular one particular phenotypephenotype As an example: Suppose that there were As an example: Suppose that there were

many different height giraffes in a region of many different height giraffes in a region of Africa that underwent sever climatic changeAfrica that underwent sever climatic change

The food availability is now 8’ higher than The food availability is now 8’ higher than before and only a limited number of giraffe before and only a limited number of giraffe can actually reach the resourcecan actually reach the resource

This would be This would be directional selectiondirectional selection

Natural Selection in Natural Selection in PopulationsPopulations

In any population of In any population of organisms there is organisms there is variationvariation within the within the speciesspecies– There are organisms There are organisms

that fit into a “bell that fit into a “bell curve” whereby the curve” whereby the largest percent of the largest percent of the population is in the population is in the center with slightly center with slightly different variations different variations on either sideon either side

These are two bell curves shown above. The mean is

the average and the majority of the population

phenotype. The curve represents the entire variation within the

population

Directional SelectionDirectional Selection Directional Directional

selectionselection – is the effect of a is the effect of a

shift in a shift in a population’s population’s phenotype in phenotype in response to response to natural natural selectionselection towards a towards a more favored more favored phenotype from the phenotype from the variation within the variation within the original populationoriginal population

Disruptive SelectionDisruptive Selection Disruptive selectionDisruptive selection

– Occurs when both Occurs when both extremeextreme phenotypes phenotypes are are favored favored by by natural selection natural selection while the while the mean mean populationpopulation is is selected against by selected against by something in naturesomething in nature

Stabilizing SelectionStabilizing Selection Stabilizing selectionStabilizing selection

– Occurs when the Occurs when the mean mean phenotypephenotype is highly is highly favored in the favored in the environment and environment and becomes even more becomes even more dominant in the dominant in the populationpopulation

– This can lead to a lower This can lead to a lower diversitydiversity which makes which makes species susceptible to species susceptible to disease or other limiting disease or other limiting factorsfactors