The Evolution of LifeThe Evolution of Life

Geologic TimeGeologic Time

The Precambrian – Age of The Precambrian – Age of BacteriaBacteria

4.6 billion – 545 million years ago

The Paleozoic – Age of The Paleozoic – Age of FishesFishes 545-251 million years ago

The Mesozoic – Age of The Mesozoic – Age of DinosaursDinosaurs251-65 million years ago

The Cenozoic – Age of MammalsThe Cenozoic – Age of Mammals65 million years ago to present day

The Precambrian – Age of The Precambrian – Age of BacteriaBacteria

4.6 billion – 545 million years ago

Early Microbial EvolutionEarly Microbial Evolution

• The earliest organisms must have The earliest organisms must have been very simple resembling early been very simple resembling early prokaryotic cells.prokaryotic cells.– Lack nucleiLack nuclei– AnaerobicAnaerobic– Chemoautotrophs that obtained their Chemoautotrophs that obtained their

carbon from carbon dioxide dissolved in carbon from carbon dioxide dissolved in the oceans.the oceans.

ProkaryotesProkaryotes• ArchaebacteriaArchaebacteria - Moderen - Moderen

bacteria that live in extremely bacteria that live in extremely hostile conditions.hostile conditions.– Appear to be close to the root of Appear to be close to the root of

the tree of life.the tree of life.– Obtain their energy through Obtain their energy through

chemical reactions.chemical reactions.• MethanogensMethanogens

– AnaerobicAnaerobic

• HalophilesHalophiles– Salty conditionsSalty conditions

• ThermophilesThermophiles– Extreme heatExtreme heat

Rate of Evolution in Early Rate of Evolution in Early OrganismsOrganisms• Early organisms Early organisms

experience a higher rate experience a higher rate of evolution because…of evolution because…– Early organisms lacked Early organisms lacked

the efficient enzymes for the efficient enzymes for DNA replication.DNA replication.

– There were many errors There were many errors as DNA was copied from as DNA was copied from one generation to the one generation to the nextnext

– More errors meant more More errors meant more mutations and a higher mutations and a higher rate of evolution.rate of evolution.

What is the evidence of rapid What is the evidence of rapid early diversification of early diversification of Organisms?Organisms?

Photosynthesis begins 3.5 billion years ago

Stromatolites

The Oxygen RevolutionThe Oxygen Revolution

2.35 billion years ago

PhotosynthesisPhotosynthesis

• Most important new metabolic process Most important new metabolic process evolved graduallyevolved gradually

• Organisms that lived close to ocean surface Organisms that lived close to ocean surface probably developed means of absorbing probably developed means of absorbing sunlight (UV in particular)sunlight (UV in particular)

• Once absorbed, developed method of Once absorbed, developed method of turning it into energyturning it into energy– Modern organisms of purple sulfur bacteria and Modern organisms of purple sulfur bacteria and

green sulfur bacteria much like early green sulfur bacteria much like early photosynthetic microbes, use H2S instead of photosynthetic microbes, use H2S instead of H2O for photosynthesisH2O for photosynthesis

PhotosynthesisPhotosynthesis

• Using water for photosynthesis developed later, Using water for photosynthesis developed later, perhaps 3.5 billion years agoperhaps 3.5 billion years ago

• First appearing in cyanobacteria (blue-green algae)First appearing in cyanobacteria (blue-green algae)• By product of OBy product of O22, released into atmosphere, released into atmosphere• Changed the world!Changed the world!

Oxygen CrisesOxygen Crises• The rise of oxygen created a crisis for life.The rise of oxygen created a crisis for life.

– It attack the bonds of organic molecules.It attack the bonds of organic molecules.

– Many species went extinct.Many species went extinct.

– Species that survived had to evolve new Species that survived had to evolve new metabolic mechanisms or live in environments metabolic mechanisms or live in environments where there was no Oxygen.where there was no Oxygen.

• Oxygen could be used to generate a far superior Oxygen could be used to generate a far superior metabolic pathway that would provide much more metabolic pathway that would provide much more energy.energy.

Early EukaryotesEarly Eukaryotes

• Fossil evidence dates to 2.1 bill. Yr agoFossil evidence dates to 2.1 bill. Yr ago

• Dates to when ODates to when O22 rising in atmosphere rising in atmosphere

• DNA evidence suggests that prokaryotes DNA evidence suggests that prokaryotes and eukaryotes separated from common and eukaryotes separated from common ancestor much earlierancestor much earlier

• OO22 played a key role in eukaryote evolution played a key role in eukaryote evolution– Cells can produce energy more efficiently using Cells can produce energy more efficiently using

aerobic metabolism than anaerobic metabolismaerobic metabolism than anaerobic metabolism– Adaptations of aerobic organisms could develop Adaptations of aerobic organisms could develop

adaptations that required more energy than adaptations that required more energy than would be available for anaerobic organismswould be available for anaerobic organisms

What two adaptations lead to the rise of modern eukaryotes?

• Some cells developed specialized infoldings of their membranes that compartmentalized certain cell functions.

• Large host cells absorbed smaller prokaryotes with specialized functions. These cells developed a symbiotic relationship– Smaller cells developed into mitochondria

What evidence suggest that modern eukaryotes developed mitochondria

through edosymbiosis?

•Mitochondria contain their own DNA.– A single circular chromosome– DNA is structured like prokaryote DNA

•Mitochondria divide independently of the cell

The Ediacaran Fauna (575 The Ediacaran Fauna (575 mya)mya)

Precambrian ContinentsPrecambrian Continents

Precambrian continents were smaller, thinner, and moved more rapidly

The PaleozoicThe Paleozoic

The Paleozoic – Age of The Paleozoic – Age of FishesFishes 545-251 million years ago

The Cambrian Explosion (525 The Cambrian Explosion (525 mya)mya)

The Cambrian ExplosionThe Cambrian Explosion

• Animal branch of the tree of lifeAnimal branch of the tree of life

• Different classifications based on Different classifications based on body planbody plan

• All known body plans made All known body plans made appearance in fossil record in a time appearance in fossil record in a time span of 40 million yearsspan of 40 million years– <1% of Earth’s age<1% of Earth’s age– Animal diversity began 545 mill. Yr agoAnimal diversity began 545 mill. Yr ago

Why did the diversification of Why did the diversification of animals occur so suddenly?animals occur so suddenly?

• Oxygen levels reached a high Oxygen levels reached a high enough level for the survival of larger enough level for the survival of larger and more energy intensive life forms.and more energy intensive life forms.

• The evolution of genetic complexityThe evolution of genetic complexity

• A milder climate away from a snow A milder climate away from a snow ball earthball earth

• Efficient preditorsEfficient preditors

Why haven’t we seen other Why haven’t we seen other explosions of diversification explosions of diversification like the Cambian?like the Cambian?

• Once predators were efficient and Once predators were efficient and widespread, it was more difficult for widespread, it was more difficult for entirely new body forms to find an entirely new body forms to find an available environment.available environment.

The Cambrian WorldThe Cambrian World

Middle Paleozoic SeasMiddle Paleozoic Seas

DunkleosteusDunkleosteus – Late – Late DevonianDevonian

Colonization of LandColonization of Land

• Life flourished where liquid water existLife flourished where liquid water exist

• Life on land was more complicatedLife on land was more complicated– Had to develop means of collecting solar Had to develop means of collecting solar

energy above ground and nutrients belowenergy above ground and nutrients below– Protection from U.V. lightProtection from U.V. light

• Life in shallow ponds or edges of lakesLife in shallow ponds or edges of lakes– Water evaporatesWater evaporates– Natural selection favored that which could Natural selection favored that which could

withstand periods of droughtwithstand periods of drought

Colonization of LandColonization of Land• DNA evidence suggests that plants evolved from an DNA evidence suggests that plants evolved from an

algae.algae.– algae developed thick cell walls to help them survive dry algae developed thick cell walls to help them survive dry

periods.periods.

• It took only 75 mill. Yrs for animals to follow plants out It took only 75 mill. Yrs for animals to follow plants out of water of water

First Land Plants and First Land Plants and InsectsInsectsAppear in the Late Silurian, diversify in the Devonian

First trees and forestsFirst trees and forests

Archaeopteris

Late Devonian

Animals move ashoreAnimals move ashoreEusthenopteron and Ichthyostega

The Formation of PangaeaThe Formation of Pangaea

Geologic TimeGeologic Time

The Mesozoic – Age of The Mesozoic – Age of DinosaursDinosaurs251-65 million years ago

Origination of MammalsOrigination of Mammals

Origination of BirdsOrigination of Birds

Archaeopteryx (Jurassic)

White White Cliffs of Cliffs of Dover: Dover:

CretaceouCretaceous Chalks Chalk

ArchelonArchelon

Cretaceous marine turtle, ~ 15’

First Flowers, Bees, and First Flowers, Bees, and GrassGrass

145 million years ago in the Cretaceous period

The End-Mesozoic The End-Mesozoic ExtinctionExtinction

Did an impact kill the Did an impact kill the dinosaurs?dinosaurs?• Iridium layer at the K-T boundaryIridium layer at the K-T boundary

• High abundance of rare metals at the High abundance of rare metals at the K-T boundaryK-T boundary– Osmium, gold and platinumOsmium, gold and platinum

• Spherical Rocks called droplets found Spherical Rocks called droplets found in the K-T boundary.in the K-T boundary.

• Soot found in the boundary.Soot found in the boundary.

Geologic TimeGeologic Time

The Cenozoic – Age of MammalsThe Cenozoic – Age of Mammals65 million years ago to present day

Radiation of mammals and Radiation of mammals and large, predatory birdslarge, predatory birds

The Paleogene of North The Paleogene of North AmericaAmerica

PeraceratheriumPeraceratheriumLargest known land mammal – 18’ at the shoulder

Mass ExtinctionsMass Extinctions

Mass ExtinctionsMass Extinctions

• Possible CausesPossible Causes– ImpactsImpacts

• Impact sites found for K-T boundaryImpact sites found for K-T boundary

•Suspected for Permian extinction 245 mill yr Suspected for Permian extinction 245 mill yr agoago

– Active volcanismActive volcanism•Climate changeClimate change

– External influence for copying errorsExternal influence for copying errors• Increase in solar particles or radiation hitting Increase in solar particles or radiation hitting

surfacesurface

•Local supernovaLocal supernova

ExtinctionsExtinctionsDemise of Species