Theory of EvolutionTheory of Evolution

EvolutionEvolution Inherited change over time, Inherited change over time,

eventually causing creation of eventually causing creation of new species.new species.

Theories of EvolutionTheories of Evolution Lamarck’s TheoryLamarck’s Theory

1.1. Tendency Toward PerfectionTendency Toward Perfection--All organisms have innate tendency toward complexity and perfectionAll organisms have innate tendency toward complexity and perfection

-continually changing to help them live in their environment-continually changing to help them live in their environment

-Ex: over generations, bird’s urge and attempts to fly gave them big -Ex: over generations, bird’s urge and attempts to fly gave them big wingswings

2. 2. Use and DisuseUse and Disuse--Evolution occurs as structures develop with use, or disappear because Evolution occurs as structures develop with use, or disappear because

of disuseof disuse

-Ex: A giraffe’s neck-Ex: A giraffe’s neck

3. 3. Inheritance of Acquired TraitsInheritance of Acquired Traits--AcquiredAcquired characteristics are passed on to offspring characteristics are passed on to offspring

Ex: If you spent your life lifting weights and building muscle, your Ex: If you spent your life lifting weights and building muscle, your children would inherit big muscles as well. children would inherit big muscles as well.

DarwinDarwin

In 1831, Darwin set sail from England aboard the In 1831, Darwin set sail from England aboard the H.M.S. H.M.S. BeagleBeagle for a voyage around the world. for a voyage around the world.

Darwin went ashore and collected plant and Darwin went ashore and collected plant and animal specimens for his collection.animal specimens for his collection.

OBSERVATIONS:OBSERVATIONS:

--Many plants and animals were well suited to the Many plants and animals were well suited to the environments they inhabited. environments they inhabited.

-Grasslands in some regions were similar to one -Grasslands in some regions were similar to one another but were inhabited by very different another but were inhabited by very different animals.animals.

Darwin wondered…Were animals Darwin wondered…Were animals living on different islands previously living on different islands previously members of the same species?members of the same species?

Could these separate species have Could these separate species have evolved from an original South evolved from an original South American (Ecuador) ancestor American (Ecuador) ancestor species?species?

Naturally there is genetic variation Naturally there is genetic variation (Mutations!) in a population allowing some (Mutations!) in a population allowing some to survive better than others. to survive better than others.

Any characteristic that gives the organism Any characteristic that gives the organism a a REPRODUCTIVE REPRODUCTIVE advantage will become advantage will become more common in a population.more common in a population.

Over time, this process results in Over time, this process results in adaptationsadaptations that specialize the organism that specialize the organism for a particular for a particular ecological niche.ecological niche.

HeritableHeritable traits that allow traits that allow animals to better survive and animals to better survive and reproduce in their environment reproduce in their environment become more common in a become more common in a population over many population over many generations. generations.

Natural selection allows for Natural selection allows for Survival of the fittest.Survival of the fittest.

Darwin’s finchesDarwin’s finches

Types of EvolutionTypes of Evolution Convergent Evolution:Convergent Evolution:

species that are NOT closely related look species that are NOT closely related look similar because they have evolved to live in similar because they have evolved to live in the same environmentthe same environment

Ex: Shark and DolphinEx: Shark and Dolphin

Divergent EvolutionDivergent Evolution::

species that are related begin to look species that are related begin to look different because they are adapting to different because they are adapting to different environmentsdifferent environments

Ex: finches, tortoisesEx: finches, tortoises

Isabela Island Tortoise Hood (Espanola) Island

Tortoise

CoevolutionCoevolution::

two species evolve togethertwo species evolve togetherSpecies= group of organisms that have similar Species= group of organisms that have similar

characteristics and can reproduce fertile characteristics and can reproduce fertile offspringoffspring

Ex: Hummingbird and cardinal flowerEx: Hummingbird and cardinal flower

Types of Natural Types of Natural SelectionSelection

Directional SelectionDirectional Selection::

individuals in one extreme are individuals in one extreme are selected to surviveselected to survive

Ex: giraffe’s neckEx: giraffe’s neck

Neck size

# o

f G

iraff

es

in

Pop

Neck size#

of

Gir

aff

es

in

Pop

Peak shifts; average neck size increases

Stabilizing selectionStabilizing selection::

individuals with the average individuals with the average phenotype are selected to survivephenotype are selected to survive

Ex: the weight of humans at birthEx: the weight of humans at birth

Birth Weight

Perc

enta

ge

of

popula

tion

Birth Weight

Perc

enta

ge

of

popula

tion

Selection against extremes; curve in same place

Disruptive selectionDisruptive selection::

individuals of both extremes are individuals of both extremes are selected to surviveselected to survive

Ex: Birds in a population where Ex: Birds in a population where small and large seeds are small and large seeds are commoncommon

Beak size

Perc

enta

ge

of

popula

tion

Beak size

Perc

enta

ge

of

popula

tion

Selection against middle, curve peaks at the extremes

Evidence of EvolutionEvidence of Evolution

Fossils (p. 252-254)Fossils (p. 252-254)a.a. Fossilized organisms in older rocks Fossilized organisms in older rocks

are different from those found in are different from those found in newer rocks.newer rocks.

• Use them to get an approximate date Use them to get an approximate date of when the organism existed.of when the organism existed.

b.b. Can compare fossils to organisms Can compare fossils to organisms alive today.alive today.

Anatomical SimilaritiesAnatomical SimilaritiesA.A. Homologous SturcturesHomologous Sturctures: (p.256): (p.256)

Different species have the same Different species have the same structures used for different functions.structures used for different functions.

Evidence that these species evolved from Evidence that these species evolved from a common ancestor.a common ancestor.

Ex: arm bonesEx: arm bones

B.B. Vestigial StructuresVestigial Structures::

Structures or organs that we have Structures or organs that we have but no longer usebut no longer use

Evidence that species share a Evidence that species share a common ancestor who once used common ancestor who once used these structures/organsthese structures/organs

Ex: Appendix, wisdom teeth, tail boneEx: Appendix, wisdom teeth, tail bone

Embriological SimilaritiesEmbriological Similarities: (p. 257): (p. 257)

Similarities in the embryonic Similarities in the embryonic development of all vertebrates development of all vertebrates suggests that they evolved from a suggests that they evolved from a common ancestor.common ancestor.

EmbryoEmbryo An organism in the early stages of An organism in the early stages of development and growth (usually before it is development and growth (usually before it is born)born)

VertebrateVertebrate An organism with a backbone An organism with a backbone

Biochemical SimilaritiesBiochemical Similarities::

Organisms that share a common Organisms that share a common ancestor have similar DNA ancestor have similar DNA segments (amino acids and segments (amino acids and proteins)proteins)

Ex: All organisms that use oxygen Ex: All organisms that use oxygen have the enzyme cytochrome c.have the enzyme cytochrome c.

ReferencesReferences http://galapagos.editme.com/http://galapagos.editme.com/

galapagos-finches2galapagos-finches2 http://search.yahoo.com/search?http://search.yahoo.com/search?

p=giraffe+pictures&fr=FP-tab-web-p=giraffe+pictures&fr=FP-tab-web-t&toggle=1&ei=UTF-8t&toggle=1&ei=UTF-8

http://www.galapagosonline.com/http://www.galapagosonline.com/Galapagos_Natural_History/Galapagos_Natural_History/Birds_and_Animals/Animals/Birds_and_Animals/Animals/Tortoises.htmlTortoises.html

http://yahooligans.yahoo.com/content/http://yahooligans.yahoo.com/content/animals/species/2633.htmlanimals/species/2633.html

http://www.auburn.edu/~folkegw/http://www.auburn.edu/~folkegw/evsys/coevlect.htmlevsys/coevlect.html