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What do the following What do the following images have in common?images have in common?
And how do they support And how do they support Darwin’s Theory of Evolution?Darwin’s Theory of Evolution?
They all have five limbsThey all have five limbs
Or, more correctly, the bones Or, more correctly, the bones for 5 limbsfor 5 limbs
Scientists look for related Scientists look for related features in unrelated (or features in unrelated (or
any) organismsany) organisms
Scientists look for related Scientists look for related features in unrelated (or features in unrelated (or
any) organismsany) organisms
In order to deduce In order to deduce common ancestorscommon ancestors
Is the common feature Is the common feature from a common ancestorfrom a common ancestor
Or due toOr due to Natural Natural SelectionSelection
Common features from a Common features from a common ancestorcommon ancestor
Are called Are called homologoushomologous featuresfeatures
Common features due to Common features due to Natural selectionNatural selection
Are called Are called analogous analogous featuresfeatures
How do we tell which How do we tell which features are which???features are which???
We We cannot !cannot !
So scientists try to choose So scientists try to choose features that do not confer features that do not confer an evolutionary advantagean evolutionary advantage
So scientists try to choose So scientists try to choose features that do not confer features that do not confer an evolutionary advantagean evolutionary advantage
Colour or camouflage Colour or camouflage would be a would be a badbad
exampleexample
So scientists try to choose So scientists try to choose features that do not confer features that do not confer an evolutionary advantagean evolutionary advantage
Bone structure is a Bone structure is a betterbetter example example
The following are all The following are all thought to have evolved thought to have evolved from a common ancestorfrom a common ancestor
The following are all The following are all thought to have evolved thought to have evolved from a common ancestorfrom a common ancestor
As they all have exactly As they all have exactly the same bone the same bone
structures and number structures and number of each boneof each bone
Even though the sizes of Even though the sizes of the bones have changedthe bones have changed
This is thought to have This is thought to have been due to been due to Natural Natural
selectionselection
Some scientists still argue Some scientists still argue over the value of this workover the value of this work
As we cannot prove the As we cannot prove the differences are due to a differences are due to a
common ancestorcommon ancestor
As we cannot prove the As we cannot prove the differences are due to a differences are due to a
common ancestorcommon ancestor
And are not just due to And are not just due to Natural selectionNatural selection
Comparative anatomy is Comparative anatomy is simply another jigsaw piece simply another jigsaw piece
in the puzzlein the puzzle
Comparative anatomy is Comparative anatomy is simply another jigsaw piece simply another jigsaw piece
in the puzzlein the puzzle
That isThat is
EvolutionEvolution
Scientists also noticed that Scientists also noticed that embryosembryos all share a all share a common pattern of common pattern of
developmentdevelopment
The similarities of The similarities of embryo’sembryo’sat different stages of at different stages of
development is also used to development is also used to deduce evolutionary deduce evolutionary
patternspatterns
The more The more recentlyrecently scientists think they scientists think they
were relatedwere related
The longer theThe longer theembryosembryos
stay similarstay similar
This image suggests fish This image suggests fish and salamanders are and salamanders are related to each otherrelated to each other
And pig, cow, rabbit and And pig, cow, rabbit and human are closely relatedhuman are closely related
These evolutionary These evolutionary relationshipsrelationshipsShould be more Should be more
correctly stated ascorrectly stated as““More”More”
closely relatedclosely related
And they support other And they support other pieces of evidence we have pieces of evidence we have
collectedcollected
And they support other And they support other pieces of evidence we have pieces of evidence we have
collectedcollected
On the sequence of On the sequence of evolution on our planetevolution on our planet
Bibliography (5 Feb 2007)Bibliography (5 Feb 2007)
Most images from images from Most images from images from www.schoolhousevideo.orgwww.schoolhousevideo.org
Hoof image from Hoof image from http://www.horsemanpro.com/images3/Hoof%20Parallels/club2.jpghttp://www.horsemanpro.com/images3/Hoof%20Parallels/club2.jpg
Hand from Hand from http://www.simreal.com/twiki2/bin/view.pl/Simreal/handofsomeonehttp://www.simreal.com/twiki2/bin/view.pl/Simreal/handofsomeone