Evidence of EvolutionEvidence of EvolutionPart IIPart II

The study of living organisms The study of living organisms reveals secrets of ancestryreveals secrets of ancestry

Theory of EvolutionTheory of Evolution

All life on Earth descended from a common All life on Earth descended from a common ancestorancestor

Life originated as a simple form, and Life originated as a simple form, and became more diverse and complex over became more diverse and complex over timetime

Evidence in OrganismsEvidence in Organisms

““Evolution proceeds by modifications of Evolution proceeds by modifications of organisms which already exist”organisms which already exist”

Evidence in OrganismsEvidence in Organisms

I.I. Homologous StructuresHomologous Structures* Definition* Definition

* Examples * Examples (Can you give detailed descriptions of (Can you give detailed descriptions of homologous bones?)homologous bones?)

I. Homologous StructuresI. Homologous Structures

Homologous StructuresHomologous Structures

Evidence in OrganismsEvidence in Organisms

II.II. Similarities in Embryonic Similarities in Embryonic DevelopmentDevelopment

• All animals:All animals: cleavage, morula, blastula, cleavage, morula, blastula, layering after blastula (gastrula) layering after blastula (gastrula)

• All Vertebrates:All Vertebrates: What did you observe?What did you observe?

Similarities in Embryonic Similarities in Embryonic DevelopmentDevelopment

The limbs of all tetrapods develop from limbThe limbs of all tetrapods develop from limbbuds in similar ways (see below).buds in similar ways (see below).

Similarities in Embryonic Similarities in Embryonic DevelopmentDevelopment

How evidence of Evolution?How evidence of Evolution?

Evidence in OrganismsEvidence in Organisms

III. Vestigial StructuresIII. Vestigial Structures• definition:definition:

• Examples:Examples:• Eyes on blind cavefishEyes on blind cavefish• Human coccyx (tailbone)Human coccyx (tailbone)• Femurs on pythons, whalesFemurs on pythons, whales• Wings on a Kiwi birdWings on a Kiwi bird

• How evidence of evolution?How evidence of evolution?

Evidence in OrganismsEvidence in Organisms What evidence suggests that life forms What evidence suggests that life forms

today share a common ancestor?today share a common ancestor? Animal life:Animal life:

– Bone homologyBone homology– Embryological comparisonsEmbryological comparisons

All life:All life:– Biochemical evidenceBiochemical evidence

DNA/ProteinsDNA/Proteins Energy reactionsEnergy reactions

QuestionQuestion

Why do scientists believe that all life on Why do scientists believe that all life on Earth descended from a SINGLE common Earth descended from a SINGLE common ancestor?ancestor?

Why don’t we think that several “trees of life” Why don’t we think that several “trees of life” exist? (One for vertebrates, one for exist? (One for vertebrates, one for invertebrates, one for plants, one for fungi, invertebrates, one for plants, one for fungi, etc?)etc?)

ANSWERANSWER

DD–NN

AA

II. Evidence in OrganismsII. Evidence in Organisms

Evidence that Life forms change over timeEvidence that Life forms change over time Vestigial StructuresVestigial Structures

– DefinitionDefinition– ExamplesExamples

Artificial SelectionArtificial Selection Peppered MothPeppered Moth