EVOLUTION“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.”~Charles Darwin

EVOLUTIONChange in a species’ genetic makeup

over time

Theory (well tested explanation)

Charles Darwin

BEFORE DARWIN… Inheritance of Acquired Traits

(Jean Baptiste Lamarck)

Organisms acquired or lost traits based on use during its lifetime & passed to

offspring

BEAGLE (1831) Collected specimens & fossils

around the world

GALAPAGOS ISLANDS• Observed many organisms

• High number of endemic species (species found only there)

• 97% of island is protected

GALAPAGOS ISLAND SPECIES OF INTEREST

1859 – ORIGIN OF SPECIESBefore DNAIntroduced

Artificial selectionNatural selectionEvolution

ARTIFICIAL SELECTION Nature provides variation, humans select

variations that are useful. Examples:• Farmers breeding best livestock• Domesticated dogs

NATURAL SELECTIONThe traits that help an organism survive in a particular environment are “selected” for in

nature

STEPS IN NATURAL SELECTION1.Genetic variation

Difference in color, size, etc.Genetic mutation (after Darwin)

2.Over population3.Struggle to survive

Not enough resources4.Successful reproduction

Well adapted live and reproduce

Adaptation Video

EUROPEAN PEPPERED MOTHS• Rested on tree trunks• Moths rest with their wings folded down• Birds were predators

EUROPEAN PEPPERED MOTHS

Two color variationsDark Pale

Before 1850Pale more common

By 1860 Dark more common

WHAT HAPPENED IN THE 1850S?Trees covered in lichensPale: blendedDark: stood out

1850s – IndustrySoot covered trees

Dark: blended Pale: stood outSimulation

NATURAL SELECTION TO EVOLUTION

• Insecticides – chemicals used to rid plants of unwanted insects•Antibiotics – treat bacterial infections•Work well before = now ineffectiveWhy?Resistance

SUMMARY OF DARWIN’S THEORY

1. Organisms differ; variation is inherited2. Organisms produce more offspring

than survive3. Organisms compete for resources4. Organisms with advantages survive to

pass those advantages to their children5. Species alive today are descended with

modifications from common ancestors

TWO TYPES OF EVOLUTION1. 1. Divergent – related species become more Divergent – related species become more

dissimilardissimilar

2. Convergent – unrelated species become 2. Convergent – unrelated species become more similar in appearance as they adapt to more similar in appearance as they adapt to a similar environmenta similar environment

EVIDENCE OF EVOLUTION

Fossil RecordHomologous structures

DNAEmbryonic structures

Youngest

Oldest

FOSSIL RECORDFossils changed between different

layers of the earth

HOMOLOGOUS STRUCTURES

Structures with different mature forms that develop from the same embryonic tissue

Modified for specific function

ANALOGOUS STRUCTURES

Similar form & function, but are structurally quite different

Same habitat

DNACommon ancestors =common DNA

Greater # of DNA similarities = closely related

EMBRYONIC STRUCTURESEmbryos may look more similar to adults

All vertebrates look similar as embryos

VESTIGIAL STRUCTURESRemnants of once useful structures

Ex. – WhaleHind limb bones

Ex. – Humans• Goosebumps

SpeciationSpeciationChanges leading to formation of new Changes leading to formation of new

species.species.Populations evolve and becomePopulations evolve and becomereproductively isolatedreproductively isolated from from each other(members of two each other(members of two populations cannot interbreed)populations cannot interbreed)

Behavioral isolationBehavioral isolation

Geographic Isolation