Origin and History of LifeOrigin and History of Life

Where it came from and how Where it came from and how it got hereit got here

Chapter OutlineChapter Outline Primitive EarthPrimitive Earth Origin of First CellsOrigin of First Cells FossilsFossils The PrecambrianThe Precambrian The PaleozoicThe Paleozoic The MesozoicThe Mesozoic The CenozoicThe Cenozoic Continental DriftContinental Drift Mass ExtinctionsMass Extinctions

BeginningsBeginnings The Universe (maybe)The Universe (maybe)

Primitive Earth—Not paradise as we Primitive Earth—Not paradise as we know it—much different than Earth know it—much different than Earth todaytoday

Simple to complexSimple to complex Question: How could these simple Question: How could these simple

molecules be made into more molecules be made into more complex ones? complex ones?

Answer: Abundant energy sources, Answer: Abundant energy sources, lots of time. lots of time.

Origin of organic moleculesOrigin of organic molecules Alexander Oparin (1938) — a Russian Alexander Oparin (1938) — a Russian

biochemist with visionbiochemist with vision Stanley Miller (1953) – tested the Stanley Miller (1953) – tested the

hypothesishypothesis

Miller ApparatusMiller Apparatus

Other modelsOther models Carbonaceous chondritesCarbonaceous chondrites

PanspermiaPanspermia

PanspermiaPanspermia Life brought in on Life brought in on

asteroids and asteroids and cometscomets

EX. Deinococcus EX. Deinococcus radioduransradiodurans

Abiotic Chemical Abiotic Chemical EvolutionEvolution

Synthesis and accumulationSynthesis and accumulation PolymerizationPolymerization AggregationAggregation Origin of heredityOrigin of heredity

Origin of First CellsOrigin of First Cells

Keep in mind!!!Keep in mind!!! Chemical natural selectionChemical natural selection

Conditions of primitive earthConditions of primitive earth

TimescaleTimescale

Evolution of Evolution of MacromoleculesMacromolecules

RNA first hypothesisRNA first hypothesis

Protein first hypothesisProtein first hypothesis

Clay hypothesisClay hypothesis

RNA first hypothesisRNA first hypothesis RNA contains information like RNA contains information like

DNADNA RNA is catalytic-- -- RNA is catalytic-- --

ribozymes.ribozymes.

Protein First Protein First HypothesisHypothesis

Most enzymes are proteinsMost enzymes are proteins

ProteinoidsProteinoids

Proteinoid microspheresProteinoid microspheres

Faithful replication?Faithful replication?

Clay hypothesisClay hypothesis Unique chemical properties of clay.Unique chemical properties of clay.

Combines parts of the RNA first and Combines parts of the RNA first and protein first ideas.protein first ideas.

Protocell EvolvesProtocell Evolves Protocells -- precursors to the Protocells -- precursors to the

first true cells.first true cells. lipid-protein membranelipid-protein membrane

Proteinoid microspheresProteinoid microspheres CoacervatesCoacervates LiposomesLiposomes

Protocell AnatomyProtocell Anatomy

Energy ManagementEnergy ManagementWere the first protocells Were the first protocells heterotrophs or heterotrophs or autotrophs?autotrophs?

Origin of First CellsOrigin of First Cells

The Origin of Life 2The Origin of Life 2

FossilsFossils Fossils are remains and traces of Fossils are remains and traces of

past lifepast life Why are they so rare?Why are they so rare?

FossilsFossils

Dating FossilsDating Fossils

Relative DatingRelative Dating

Absolute datingAbsolute dating

CombinationCombination

StrataStrata

The Precambrian The Precambrian Age of Age of microbes microbes

570 mya - 4.6 bya570 mya - 4.6 bya The First Cells —3.5-4 billion years agoThe First Cells —3.5-4 billion years ago What were they like? What were they like?

Energy management?Energy management?

Aquatic or terrestrial?Aquatic or terrestrial?

Prokaryote or eukaryote?Prokaryote or eukaryote?

Evolution of AutotrophsEvolution of Autotrophs Life as Energy ManagementLife as Energy Management

ChemoautotrophsChemoautotrophs

PhotoautotrophsPhotoautotrophs

Atmospheric OAtmospheric O22 ~2 BYA ~2 BYA

Atmospheric OAtmospheric O22—SO WHAT?—SO WHAT?OO2 2 is very reactive—Poisonis very reactive—Poison. .

Cells had to deal with thisCells had to deal with thisAerobicAerobicAnaerobicAnaerobicFacultative anaerobesFacultative anaerobes

Changes in atmosphere– OChanges in atmosphere– O22 and ozone. So? and ozone. So?Consequences for energy acquisitionConsequences for energy acquisition

Circle of LifeCircle of Life

Carbon compounds, O2

CO2, H2O

Respiration

Photosynthesis

Energy

Energy

Eukaryotes evolveEukaryotes evolve More complexMore complex

Origin? Endosymbiont hypothesisOrigin? Endosymbiont hypothesis

ribosomes

cell wallplasma membrane

food granule

prokaryoticflagellum

cytoplasm

nucleoid (DNA)

flagellum

cytoplasmrough endoplasmicreticulum

ribosome

microtubules

lysosome

mitochondrion

Golgi complex

plasmamembrane

intermediatefilaments

vesicle

smooth endoplasmicreticulum

free ribosome vesicle

nuclear porechromatin (DNA)

nucleolusnuclear envelope

nucleus

1. Anaerobic, predatoryprokaryotic cell engulfsan aerobic bacterium.

2. Descendants of engulfedbacterium evolve intomitochondria.

3. Mitochondria-containingcell engulfs a photosyntheticbacterium.

4. Descendants of photosyntheticbacterium evolve into chloroplasts.

aerobicbacterium

Multicellularity EvolvesMulticellularity EvolvesExamples?Examples?Volvox—Simple, Volvox—Simple, multicellularmulticellular

Advantages?Advantages?

Summary of PrecambrianSummary of Precambrian Earth formsEarth forms Prokaryotes evolvedProkaryotes evolved PhotosynthesisPhotosynthesis EukaryotesEukaryotes MulticellularityMulticellularity Sexual reproductionSexual reproduction

PaleozoicPaleozoic

Paleozoic 2Paleozoic 2 Mass extinction---Disappearance Mass extinction---Disappearance

of a large number of species of a large number of species within a relatively small time within a relatively small time interval.interval.

opportunities for speciationopportunities for speciation

PALEOZOIC- MAJOR EVENTSPALEOZOIC- MAJOR EVENTS What were the major events of What were the major events of

the Paleozoic?the Paleozoic?1.1. three mass extinctionsthree mass extinctions2.2. Invertebrates dominated – Invertebrates dominated –

exoskeletonexoskeleton3.3. Primitive plants invaded landPrimitive plants invaded land

PALEOZOIC- MAJOR EVENTSPALEOZOIC- MAJOR EVENTS

1.1. Vertebrates appeared (jawless Vertebrates appeared (jawless fishes) -- internal skeletonfishes) -- internal skeleton

2.2. Insects and amphibians invaded Insects and amphibians invaded the land -- -- evolution of flight, the land -- -- evolution of flight, evolution of lungs, evolution of evolution of lungs, evolution of stronger limbs, strengthened stronger limbs, strengthened internal skeletoninternal skeleton

PALEOZOIC- MAJOR EVENTSPALEOZOIC- MAJOR EVENTS1.1. Reptiles appearReptiles appear

a)a) Shelled eggShelled eggb)b) Scaly skinScaly skinc)c) Reptiles diversify amphibians Reptiles diversify amphibians

declined declined 2.2. Coal forming forestsCoal forming forests3.3. Conifers appearConifers appear

Invasion of LandInvasion of Land PlantsPlants InvertebratesInvertebrates VertebratesVertebrates

MesozoicMesozoic

MESOZOIC- MAJOR EVENTSMESOZOIC- MAJOR EVENTS The age of reptilesThe age of reptiles Angiosperms evolve-insects Angiosperms evolve-insects

diversifydiversify Mammals and birdsMammals and birds Evolution of endothermyEvolution of endothermy

QUESTIONSQUESTIONS From what to did dinosaurs evolve?From what to did dinosaurs evolve? From what to do to mammals From what to do to mammals

evolve?evolve? From what did birds evolve?From what did birds evolve? What caused the mass extinction of What caused the mass extinction of

dinosaurs?dinosaurs? Were the dinosaurs endothermic?Were the dinosaurs endothermic?

Endothermy vs EctothermyEndothermy vs EctothermyEndothermyEndothermy

Warm –bloodedWarm –bloodedRequires a high use Requires a high use

of energyof energyHigh metabolic rateHigh metabolic rateDisadvantages?Disadvantages?

EctothermyEctothermy

Cold bloodedCold bloodedLess energy necessaryLess energy necessaryRegulation?Regulation?

behavioralbehavioralstructuralstructural

inertial ectothermyinertial ectothermy

Cretaceous Mass Cretaceous Mass ExtinctionExtinction

Bolide theory -- -- the most Bolide theory -- -- the most widely accepted theory of widely accepted theory of the Cretaceous Mass the Cretaceous Mass extinction.extinction.

Bolide -- -- and exploding Bolide -- -- and exploding asteroid.asteroid.

CenozoicCenozoic

CENOZOIC- MAJOR EVENTSCENOZOIC- MAJOR EVENTS Three mass extinctionsThree mass extinctions Decline of reptilesDecline of reptiles Diversification ofDiversification of

AngiospermsAngiosperms InsectsInsects BirdsBirds MammalsMammals

Factors That Influence Factors That Influence EvolutionEvolution

Continental DriftContinental Drift Positions of continents and oceans Positions of continents and oceans

are not fixed.are not fixed.

How does this explain the presence How does this explain the presence of marsupials and monotremes in of marsupials and monotremes in Australia?Australia?

Continental DriftContinental Drift

Continental DriftContinental Drift Plate TectonicsPlate Tectonics

Movements of Earth’s crust which is Movements of Earth’s crust which is fragmented into slablike plates that float fragmented into slablike plates that float on a lower hot mantle layer.on a lower hot mantle layer.

Plate TectonicsPlate Tectonics

Mass extinctionsMass extinctionsA A mass extinctionmass extinction occurs when a large occurs when a large fraction of all living species becomes fraction of all living species becomes rapidly extinct.rapidly extinct.The fossil record shows that at least five The fossil record shows that at least five major mass extinctions have occurred in major mass extinctions have occurred in the past 500 million years.the past 500 million years.Impacts of asteroids on Earth are Impacts of asteroids on Earth are suspected as a primary cause of mass suspected as a primary cause of mass extinction.extinction.

Mass ExtinctionsMass Extinctions Mass extinctions have occurred Mass extinctions have occurred

throughout history. At the ends of:throughout history. At the ends of: OrdovicianOrdovician

Continental DriftContinental Drift DevonianDevonian

Bolide EventBolide EventLoss of 70% of marine Loss of 70% of marine invertebratesinvertebrates

Mass ExtinctionsMass Extinctions PermianPermian

Excess carbon dioxide.Excess carbon dioxide.Loss of 90% of ocean species.Loss of 90% of ocean species.

TriassicTriassicMeteorite CollisionMeteorite Collision

Cretaceous—probably a bolide.Cretaceous—probably a bolide.

Permian Mass ExtinctionPermian Mass ExtinctionAt the end of the Permian period (about At the end of the Permian period (about

245 mya), destroyed 90-95% of marine 245 mya), destroyed 90-95% of marine and 70% of land species.and 70% of land species.

Possibilities?Possibilities? The glaciation of GondwanalandThe glaciation of Gondwanaland the increased fluctuation of global the increased fluctuation of global

temperatures temperatures volcanic eruptions occurring in volcanic eruptions occurring in

SiberiaSiberia

Mass ExtinctionsMass ExtinctionsIntrinsic gradualismIntrinsic gradualismExtinction caused Extinction caused

primarily by primarily by climate change or climate change or other gradual other gradual processes.processes.

EX. Global warmingEX. Global warming

Extrinsic Extrinsic catastrophismcatastrophism

Extinction caused by Extinction caused by a catastrophea catastrophe

Ex. Asteroid collision Ex. Asteroid collision with Earthwith Earth

ReviewReview Primitive EarthPrimitive Earth Origin of First CellsOrigin of First Cells FossilsFossils The PrecambrianThe Precambrian The PaleozoicThe Paleozoic The MesozoicThe Mesozoic The CenozoicThe Cenozoic Continental DriftContinental Drift Mass ExtinctionsMass Extinctions