NOTES 30 – Evidence of NOTES 30 – Evidence of EvolutionEvolution

How is the theory of evolution How is the theory of evolution supported?supported?

1.1. Evidence that shows species have Evidence that shows species have changed over timechanged over time

Proves that species have not always existed Proves that species have not always existed in their current formsin their current forms

2.2. Evidence that shows different species Evidence that shows different species come from common ancestors come from common ancestors

Proves that one species can split into two Proves that one species can split into two different species over timedifferent species over time

The theory of evolution is supported by two types of evidence:

FossilsFossils

DimetrodonDimetrodon

What types of evidence show that What types of evidence show that species have changed over time?species have changed over time?

FossilsFossils – fossils are the remains of ancient – fossils are the remains of ancient organisms (bones, etc.)organisms (bones, etc.)

Fossils have been found that are not like Fossils have been found that are not like any species alive todayany species alive today

Fossils have been found that are similar Fossils have been found that are similar to species alive todayto species alive today

Fossils show that other kinds of life have Fossils show that other kinds of life have existed and that species have changed existed and that species have changed over timeover time

Fossils & Ancient Fossils & Ancient Life Life 1.1. Water carries small Water carries small

rock particles to rock particles to lakes and seaslakes and seas

2.2. Dead organisms are Dead organisms are buried by layers of buried by layers of sediment which sediment which eventually forms eventually forms new layers of rocknew layers of rock

3.3. The preserved The preserved remains may later remains may later be discovered and be discovered and studiedstudied

Fossils & Ancient LifeFossils & Ancient Life From fossils, scientists can infer what From fossils, scientists can infer what

past life forms were like: their past life forms were like: their structure, what they ate, what ate structure, what they ate, what ate them, & the environment where they them, & the environment where they livedlived

They group similar organisms They group similar organisms together & arrange them in the order together & arrange them in the order that they lived, from oldest to most that they lived, from oldest to most recentrecent

Together, all this information about Together, all this information about past life is called the fossil recordpast life is called the fossil record

http://www.fossilmuseum.net/FossilGahttp://www.fossilmuseum.net/FossilGalleries.htmlleries.htm

Fossils & Ancient LifeFossils & Ancient Life Relative datingRelative dating - determining the age of a - determining the age of a

fossil by comparing its placement with fossil by comparing its placement with that of fossils in other layersthat of fossils in other layers

Horse Fossil RecordHorse Fossil Record

Horse Fossil RecordHorse Fossil Record

Fossils & Ancient LifeFossils & Ancient Life The fossil record shows The fossil record shows

that more than 99% of that more than 99% of all species that have all species that have ever lived on Earth ever lived on Earth have become extincthave become extinct

The dodo has been The dodo has been extinct since the mid-extinct since the mid-to-late 17th century. It to-late 17th century. It is commonly used as is commonly used as the archetype of an the archetype of an extinct species because extinct species because its extinction occurred its extinction occurred during recorded human during recorded human history, and was history, and was directly attributable to directly attributable to human activity. human activity.

What types of evidence show that What types of evidence show that species have changed over time?species have changed over time? Vestigial OrgansVestigial Organs – body parts found in – body parts found in

species that have little or no usespecies that have little or no use These organs are parts that had uses in the These organs are parts that had uses in the

ancestors of the species but as new species ancestors of the species but as new species evolved they were no longer necessary for evolved they were no longer necessary for survivalsurvival

EX. the human appendix is a small tube on EX. the human appendix is a small tube on the end of the large intestine that has no the end of the large intestine that has no modern function but was necessary to modern function but was necessary to digest rough plant matter which was a large digest rough plant matter which was a large part of the diet of our non-human ancestorspart of the diet of our non-human ancestors

Vestigial organs show that species have Vestigial organs show that species have changed over timechanged over time

Vestigial Vestigial OrgansOrgans

Some snakes and whales show the remains of pelvis and leg bones from walking ancestors

Non-functioning eyes on blind cave fish

Human tail bone

Why would whales have pelvis and leg Why would whales have pelvis and leg bones if they were always sea bones if they were always sea creatures?creatures?

Homologous StructuresHomologous Structures

What types of evidence show that What types of evidence show that species come from common ancestors?species come from common ancestors? Homologous StructuresHomologous Structures – body parts in – body parts in

different species that are built in a similar way different species that are built in a similar way even though they may have different functionseven though they may have different functions

EX. the bones in the arm of a human EX. the bones in the arm of a human are similar to the bones in the front leg are similar to the bones in the front leg of a cat and in the front fin of a whaleof a cat and in the front fin of a whale

Homologous structures are similar Homologous structures are similar because the two species shared a because the two species shared a common ancestor with a similar body common ancestor with a similar body part that evolved as the species part that evolved as the species changed over timechanged over time

Homologous structures Forelimbs of human,

cats, whales, & bats share same skeletal structures

similar structure similar

embryological development

different functions evidence of common

ancestor (branched off from common 4-limbed ancestor)

Homologous StructuresHomologous Structures

Comparative Comparative AnatomyAnatomy

Looking at structures Looking at structures in different organisms in different organisms in order to determine in order to determine relationships between relationships between them, how they are them, how they are alike, and how they alike, and how they are differentare different

Comparative Comparative AnatomyAnatomy

Looking at structures Looking at structures in different organisms in different organisms in order to determine in order to determine relationships between relationships between them, how they are them, how they are alike, and how they alike, and how they are differentare different

EmbryologyEmbryology

What types of evidence show that What types of evidence show that species come from common ancestors?species come from common ancestors? EmbryologyEmbryology – the study of animal embryos (the – the study of animal embryos (the

early stages of development before birth)early stages of development before birth)

Different species go through similar Different species go through similar stages in early developmentstages in early development

Closely related species have very Closely related species have very similar embryos (EX. human and pig)similar embryos (EX. human and pig)

If species are not closely related, the If species are not closely related, the embryos begin to look different earlier embryos begin to look different earlier (EX. human and fish)(EX. human and fish)

Comparing EmbryosComparing Embryos

What types of evidence show that What types of evidence show that species come from common ancestors?species come from common ancestors? Molecular BiologyMolecular Biology – studying the – studying the

molecules that make up living thingsmolecules that make up living things Closely related organisms have common DNAClosely related organisms have common DNA

All living things have DNA which is built of All living things have DNA which is built of the same ingredientsthe same ingredients

All living things have some DNA in All living things have some DNA in commoncommon

The closely related 2 different species are, The closely related 2 different species are, the more DNA they have in common (EX. the more DNA they have in common (EX. humans and chimps share about 99% of humans and chimps share about 99% of their DNA)their DNA)

Closely related organisms have common Closely related organisms have common proteinsproteins

What does all the evidence What does all the evidence mean?mean? Species alive today are NOT the same Species alive today are NOT the same

species that have always been on the Earthspecies that have always been on the Earth Species have changed over timeSpecies have changed over time Many species that have existed in the past Many species that have existed in the past

are now extinctare now extinct It appears that different species share It appears that different species share

common ancestorscommon ancestors and that all life can be and that all life can be traced back to the appearance of the first traced back to the appearance of the first living things – this explains why different living things – this explains why different species alive today share so many species alive today share so many characteristics (cells, DNA, etc.)characteristics (cells, DNA, etc.)

Evolution explains both Evolution explains both the the unityunity and and diversitydiversity of lifeof life