The History of LifeThe History of Life14.2 The origin of Life14.2 The origin of Life

The Origin of Life: Early IdeasThe Origin of Life: Early Ideas

People saw maggots People saw maggots appear on rotting meatappear on rotting meat

People saw mice appear People saw mice appear in food storagein food storage

Thought that living Thought that living things sprouted from the things sprouted from the non-livingnon-living

The Origin of Life: Early IdeasThe Origin of Life: Early Ideas Spontaneous generationSpontaneous generation is the is the

idea that non-living material can idea that non-living material can produce lifeproduce life

The Origin of Life: Early IdeasThe Origin of Life: Early Ideas In In 1668 Francesco Redi showed that 1668 Francesco Redi showed that

living things did not come from non-living things did not come from non-livingliving

The Origin of Life: Early IdeasThe Origin of Life: Early Ideas People still believed that life must People still believed that life must

arise from somewherearise from somewhere– Maybe from some vital force in the airMaybe from some vital force in the air

The Origin of Life: Early IdeasThe Origin of Life: Early Ideas In In mid-1800s Louis Pasteur showed mid-1800s Louis Pasteur showed

that living things that living things would would not arise not arise from airfrom air

The Origin of LifeThe Origin of Life Biogenesis – Biogenesis – the idea that living the idea that living

things come only from other living things come only from other living thingsthings

Biogenesis became cornerstone of Biogenesis became cornerstone of biologybiology

But how did the first life on Earth But how did the first life on Earth begin?begin?

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas For life on Earth to beginFor life on Earth to begin

– Molecules that contain carbon formMolecules that contain carbon formOrganic moleculesOrganic molecules

– Then Then are organized into complex are organized into complex moleculesmoleculesProteins, carbohydrates, nucleic acidsProteins, carbohydrates, nucleic acids

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas 1930s Russian 1930s Russian

Alexander Oparin Alexander Oparin saidsaid– Heat from lightning on Heat from lightning on

the oceans triggered the oceans triggered formation of organic formation of organic moleculesmolecules

1953 Americans 1953 Americans Miller and UreyMiller and Urey

– Simulated the conditions Simulated the conditions of early Earthof early Earth

– Supported Oparin’s Supported Oparin’s hypothesishypothesis

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas 1950s experiments showed that 1950s experiments showed that

organic molecules in heated water organic molecules in heated water form complex molecules like form complex molecules like proteins, ATPproteins, ATP

American Sydney Fox showed that American Sydney Fox showed that amino acid chains can amino acid chains can form protocellsform protocells

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas Protocells are large structures with a Protocells are large structures with a

membrane that carry out life membrane that carry out life activities like growth and divisionactivities like growth and division

Protocells evolved to prokaryotesProtocells evolved to prokaryotes

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas The first prokaryotes The first prokaryotes were were

– AnaerobicAnaerobic – without oxygen – without oxygen– HeterotrophsHeterotrophs – don’t make own food – don’t make own food

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas Next: ArchaebacteriaNext: Archaebacteria

– Prokaryotes that live in harsh environsProkaryotes that live in harsh environs– AutotrophsAutotrophs – make own food – make own food– ChemosynthesisChemosynthesis – get energy from – get energy from

inorganic compounds in the environmentinorganic compounds in the environment

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas Then: Prokaryotes that get food from Then: Prokaryotes that get food from

photosynthesisphotosynthesis Start to make oxygenStart to make oxygen

The Origin of Life: Modern ideasThe Origin of Life: Modern ideas Eukaryotes evolve when prokaryotes Eukaryotes evolve when prokaryotes

team upteam up– Proposed by American Lynn Margulis 1960Proposed by American Lynn Margulis 1960