evolution, natural selection, and speciation

“Evolve” Means to Change Over Time

The belief that life on Earth has changed over time is quite old

To be considered science, this belief requires a great deal of evidence

The Development of Evolutionary TheoryThe Development of Evolutionary Theory Naturalists have always wondered at the Naturalists have always wondered at the

diversity of living things………diversity of living things………Great varieties in shape, size, and ecological roleEstimated 3 million to 20 million different living speciesMuch of the natural world’s biodiversity has vanished through extinction99% of all species that ever lived are now extinctPermian-Triassic Mass ExtinctionWhat Killed the Dinosaurs?

Development of Evolutionary TheoryDevelopment of Evolutionary Theory

What could cause such great diversity, What could cause such great diversity, and why have so many species died and why have so many species died out?out?

Charles Darwin offered an explanation based Charles Darwin offered an explanation based on careful observationson careful observations

Who was Charles Darwin?Who was Charles Darwin?

Development of Evolutionary TheoryDevelopment of Evolutionary TheoryDarwin Concluded:

Physical traits and behaviors enable organisms to survive and reproduce (called Fitness )Fitness results from adaptationsDarwin reasoned that adaptations result from natural selection and result in evolution

Evolution is the process by which living Evolution is the process by which living things change and diversify over timethings change and diversify over time

Development of Evolutionary TheoryThese ideas were widely challenged until a tremendous amount of evidence was gathered to support evolution!

Now…The Theory of Evolution is the Cornerstone of BiologyExplore the Evolution Revolution

The Origin of LifeGeologyThe Fossil RecordComparative EmbryologyComparative BiochemistryComparative AnatomyIsn’t Evolution Just a Theory?

Scientists from many disciplines including biology, chemistry, physics, geology, and paleontology have contributed to the case for evolution!

The Origin of LifeOrigin of the UniverseBig Bang (animation)Early EarthEvolution Starts Up: Chemical EvolutionHeterotroph Hypothesis: Molecules of life arose from inorganic building blocks

The Miller-Urey ExperimentStudied Molecules Present at Time of Early Earth

Methane, Ammonia, Carbon Dioxide, Water VaporMixed Molecules in Reaction ChamberSparked with Electricity to Simulate LightningExposed Mixture to UV Radiation to Simulate Cosmic RaysProduced Basic Amino Acids and Organic Molecules

Miller-Urey Apparatus

Biological Evolution

RNA as a information molecule and catalystEndosymbiotic Theory

Mitochondria and chloroplasts were originally free living prokaryotic cellsBoth have own DNA and ribosomesJoined together to cooperate

GeologyThe Study of the Earth and RocksEarly Ideas About Earth:

People believed Earth was only a few thousand years oldPeople believed that rocks and geological features were shaped by catastrophic events and rarely changed

GeologyIn the 18th and 19th Century Scientists Studied Geology in Great Detail

Over millions of years 1 original continent Pangea drifted apart to make our modern continentsContinental drift is gradual “gradualism”

GeologyHutton and Lyell: Earth is Changed by Weather and Natural Processes like Volcanoes and ErosionTakes a Very Long Time!

GeologyThese ideas refute the idea that the Earth is only a few thousand years old

Backed up by radiometric dating The Earth is approximately 4.6 Billion Years Old

4,600,000,000 years is a long time!

The Fossil RecordFossils are the preserved remains of ancient organisms

Provide information about past organismsShows that many diverse organisms lived at different times in Earth’s History                                    

The Fossil RecordTaphonomy: The Formation of Fossils

Fossils form in sedimentary rockDead organisms covered by sand and siltSediments are passed into bone by pressure from above (fossils form in sedimentary rock)Video

Determining the Age of FossilsRelative Dating: Technique used by scientists to determine the age of fossils relative to fossils in other layers of rock

Different layers represent different geologic periods Older fossils found in lower layers, newer fossils found in upper layersCannot determine the actual age of the fossil!

Determining the Age of FossilsRadioactive Dating: Process by which traces of radioactive elements are analyzed to calculate the actual age of a fossilMany radioactive elements can be used as geologic clocks. Each radioactive element decays at its own nearly constant rate. Once this rate is known, geologists can estimate the length of time over which decay has been occurring by measuring the amount of radioactive parent element and the amount of stable daughter elements Video

Radiometric DatingRadioactive Parent

Stable Daughter

Half life

Potassium 40 Argon 40 1.25 billion

yrs

Rubidium 87Strontium

8748.8 billion

yrs

Thorium 232 Lead 20814 billion

years

Uranium 235 Lead 207704 million

years

Uranium 238 Lead 2064.47 billion

years

Carbon 14 Nitrogen 14 5730 years

The Geologic Time ScaleBased on fossil and geologic evidenceA record of the Earth’s pastDivided into Era, Period, and EpochShows that life on Earth followed geologic change on Earth

Deep Time ActivityInteractive Time Scale

Comparative EmbryologyEmbryos are organisms at early stages of development

Comparative EmbryologyAll vertebrate embryos, including humans, share features

Eye spot • (Evolution of the Human Eye)

Gill pouchesNotochord

Shows similar genetic ancestryVideo

Comparative BiochemistryAll life is based on organic chemistry

Carbon based compounds

All life uses same molecule as blueprint DNA

Similar chemical processesBacteria, algae, and plants all do photosynthesis

Similar organisms have similar genetic codeHumans and chimpanzees share nearly identical genes (98.4% identical gene sequences) Video

Anatomy and Comparative AnatomyVestigial Organs

Organs inherited but not used by modern organismsPresent but greatly reduced in modern organismsHip bone in pythonAppendix in humanTail bone (cocyx) in human

Anatomy: Homologous StructuresSimilar parts of different organisms, often quite dissimilar in purpose, that developed from the same ancestral body parts (Video)Divergent evolution

Anatomy: Analogous StructuresSimilar in purpose, but not inherited from a recent common ancestorEnvironment selected for trait

Wings of birds and insects

Convergent evolution

Summary

There is overwhelming evidence to support the Theory of EvolutionEvidence comes from disciplines as varied as biology, geology, chemistry, physics, astronomy, and paleontologyEvolution has produced the great beauty and diversity of life on Earth over the last 4 billion years

Natural Selection and Speciation

Charles Darwin

Studied Medicine and TheologyExcelled in Geology and BiologyIn 1831 Darwin joined the H.M.S. Beagle on a trip around the world to make mapsHe was the ship’s naturalistDarwin’s Diary

The Voyage of the Beagle: Ports of Call

Noted that populations of organisms were slightly Noted that populations of organisms were slightly different from place to placedifferent from place to place

Each group was modified to their specific Each group was modified to their specific environmentenvironment

The Galapagos ArchipelagoThe Galapagos Archipelago

Land Iguana

Marine Iguana

The Origin of Species Interactive Exploration

Evolution Through Natural SelectionThere is variation in populations caused by There is variation in populations caused by genetics (Praying Mantis Camouflage)genetics (Praying Mantis Camouflage)Many more offspring are produced than can Many more offspring are produced than can survive. Many die through predation or starvationsurvive. Many die through predation or starvationSome variations are favorable and help organisms Some variations are favorable and help organisms compete to survive and reproducecompete to survive and reproduceOver time, the organisms with favorable variations Over time, the organisms with favorable variations become plentiful. The ones without favorable become plentiful. The ones without favorable variations become rare or extinctvariations become rare or extinctReluctantly published On the Origin of Species On the Origin of Species in in 18591859Video

Speciation

Natural Selection modifies populations. Some evolutionary changes are so great that some organisms can no longer interbreed with the original populationA new species resultsSpecies

An interbreeding population of organisms that can produce healthy, fertile offspring

Reproductive Barriers and SpeciationPrezygotic: gametes never meet and fuse

Geographic isolation (allopatric speciation)Ecological isolationBehavioral isolation (lacewing songs)Mechanical isolationSeasonal isolation

Postzygotic: genetic differences manifestHybrid inviabilityHybrid sterility (tigons and ligers)

Patterns in EvolutionAdaptive Radiation

Development of numerous new species from a common ancestor in diverse environmentsDarwin’s Finches (Origin of Species Activity)

GradualismPunctuated Equilibrium

Evolution Produces Diversity

All living things are classified by characteristics into 5 kingdoms of life

Monera: bacteria, unicellular prokaryotesProtista: single celled eukaryotesFungi: multicellular, eukaryotic, nonmotile, heterotrophs Plantae: multicellular, eukaryotic, autotrophs

Animalia: multicellular, eukaryotic, motile, heterotropohs

Linnean TaxonomyExample: human classification

Kingdom animaliaPhylum chordataClass mammaliaOrder primateFamily hominidGenus homoSpecies sapiens

Binomial nomenclature uses genus and species to make the scientific nameHomo sapiensClassification activity

Human Evolution

Explore Human EvolutionView the Becoming Human broadband documentary

As you view each segment, visit the related exhibits to further explore this topic

Go to the Learning Center and select the “Calculating Cousins” activityGo to the Learning Center and select the “Chromosome Connection” activityGo to the Learning Center and select the “Building Bodies” activity

The Order Primate

Characteristics of PrimatesStrong hands and opposable thumbsFree-moving shoulder jointForward facing eyes and stereoscopic visionIntelligence/larger brainSocial complexity

What Characteristics do Humans Have?All of those of primates, plus

Upright posture and bipedalUse of tools and technologyAdvanced intelligenceComplex communication and speech

The Steps to Human Evolution

TerrestrializationBipedal (Walking on all two’s)Increased Brain SizeCivilizationTake a look at the Human family tree

The Hominid Family

Each year new fossils are found to add to the Hominid family treeMost fossils of early humans are found in Africa and lower AsiaMost well understood members include genus Australopithecus (extinct) and genus HomoSolve the Riddle of the Bones

Genus AustralopithecusFirst human ancestor to live on the ground and walk on two legs

As evidenced by the Laetoli footprints

Ape-like jawSmall brainShort statureFound only in South and East Africa

The AustralopithecinesA. anamesis 4 MYAA. afarensis 3.2 MYA (Finding “Lucy”)A. africanus 2.5 MYAA. robustus 2 MYA A. boisei 2 MYA

Genus HomoMore modern hominids that exhibited major evolutionary steps

Increased brain sizeUse of toolsUse of fireUse of shelterReligionLanguage and civilization

Homo habilis “The Tool Man”Approx. 2.5 MYABrain ½ size of modern humanFirst to make and use stone tools and weapons

Homo erectus “The Upright Man”

Direct ancestor of modern humansWidespread in Africa and Asia by 1 MYAEvidence of use of shelter and fire

Homo sapiens “The Wise Man”Most likely evolved from H. erectus as early as 400,000 years agoGreatly increased brain sizeConsisted of 2 groups

NeanderthalCro-Magnon/modern H. sapiens

NeanderthalsFound in Neander Valley in GermanyFossils found throughout Europe, Middle East, and Asia from 150,000-30,000 years agoLarge bodies and brainsEvidenced painting, religion, complex social structure“Cave man”

Cro Magnons and Fully Modern HumansFirst early modern H. sapiens appear about 130,000 years agoThinner bones, smaller jaws, higher skull with little or no brow ridge, and larger brainsCave art shows complex religion and cultureLived alongside Neanderthal for several thousand years, but eventually out-competed them