Evidence of Evolutionary Change

Comparing Fossils

• Evidence for Evolution

• Shows that Living Systems change

• Change is STILL happening

Galapagos Archipelago

• Isolated Island used for scientific study

• Biologists observed 2 species of birds:– Medium Ground Finch– Cactus Finch

Galapagos Islands

Bird Experiment

• 12 year period

• Took measurements of:– Size of bodies– Thickness of beaks

• 2 severe dry spells – caused many bird fatalities

Galapagos Island

Bird Experiment Results

• Avg. characteristics of the surviving populations changed

– Larger sized birds

– Thicker beaks

Galapagos Island

Bird Experiment Analysis

1.Biological change– Influenced by natural circumstances– Passed on from generation to generation

2.Species change gradually

3.Small changes add up to significant differences

Comparative Anatomy

• Branch of biology that concentrates on the similarities and differences in anatomical features of different species

Comparative Anatomy

• Look for structural similarities/differences

• Similar characteristics may suggest evolutionary relatedness

• Book pg 107 **Good Graphic**

Homologous Structure

• Characteristic that is similar among different organisms because they evolved from a common ancestor

• Ex. Forearm Structure– Consistent similarities– Develop same way in young– Different functions

Vestigial Structure

• Structures that are functional in some species, but seemingly useless in others

• “Vestige”—a remnant of

• Ex. Tails– Most mammals have tails– Humans/Apes

• Tail represented by last 3-5 bones of the backbone• Tail-moving muscles also present

Genetic Information

• DNA– Deoxyribonucleic Acid– Genetic “Blueprint”

• Allows Scientists to determine how closely related 2 organisms are

Genetic Information

Animal % of DNA that is the Same as Human DNA

Monkey

(old world primate)

93%

Gibbon (lesser ape)

95%

Chimpanzee (great ape)

98+%

Genetic Information

• Scientists can also show which organisms ARE NOT closely related

– Bacterium• interpreted as an entirely different organism

Charles Darwin

• HMS Beagle

• 5 year journey

• Mission: chart sections of theS. American Coast

Darwin

• Deserted mission and spent time collecting specimen and recording observations

• Questioned the geographical distribution of the organisms that he observed

Darwin

• Organisms similar to those in Europe, but very distinct

• Organisms in mild S. America climates more similar to organisms in tropical S. America than to organisms in mild European climates

• Organisms perfect for their environment

Darwin

• Returned to England and spent 20 years analyzing data

• On the Origin of the Species (1859)– Word “evolution” not used– “descent with modification”

• Evolution by Natural Selection

Darwin

• Only published b/c realized that other scientists were thinking the same– Alfred Russel Wallace

• Integrity