BIOLOGY Chpt - 12 History of Life on Earth. The Theory of Spontaneous Generation Before the microscope, it was commonly thought life arose from NON- LIFE.

BIOLOGY Chpt - 12BIOLOGY Chpt - 12

History of Life on EarthHistory of Life on Earth

The Theory of The Theory of Spontaneous Generation Spontaneous Generation

Before the Before the microscope, it was microscope, it was commonly thought commonly thought life arose from life arose from NON-LIFE - NON-LIFE - ABIOGENESISABIOGENESIS

Flies came from Flies came from rotting meat!rotting meat!

Bacteria came Bacteria came from rotting broth!from rotting broth!

Francesco RediFrancesco Redi - - disproved flies came disproved flies came from rotting meat!from rotting meat!

Louis PasteurLouis Pasteur disproved bacteria disproved bacteria spontaneously arose spontaneously arose from broth!from broth!

BIOGENESISBIOGENESIS- Life - Life must arise from must arise from Life!!Life!!

HOW DID LIFE BEGIN? HOW DID LIFE BEGIN?

How did life form how How did life form how earth?earth?

2-ways to approach 2-ways to approach this…..this…..

Philosophy - SciencePhilosophy - Science

The AGE OF THE EARTH…………The AGE OF THE EARTH…………

Earth formed 4.5 billion Earth formed 4.5 billion years ago!years ago!

The Earth Began as a The Earth Began as a hot molten ball of lava..hot molten ball of lava..

3.9 billion years ago 3.9 billion years ago water vapor began to water vapor began to appearappear

3.5 billion years ago-3.5 billion years ago-life began!life began!

From Geology and Archeology

A History in the RockA History in the Rock Oldest rocks - Oldest rocks - 3.9 billion 3.9 billion

yearsyears old! old! They provide us with They provide us with

fossils, casts, imprintsfossils, casts, imprints, , and specimens in and specimens in amber amber and iceand ice

Most fossils occur in Most fossils occur in sedimentary rock!sedimentary rock!

Relative datingRelative dating - layers - layers closer to the surface are closer to the surface are younger than those found younger than those found in deeper layers!in deeper layers!

Plate Tectonics and. Continental Plate Tectonics and. Continental DriftDrift

The crust of the earth is The crust of the earth is floating on magma!floating on magma!

As the magma flows, As the magma flows, the crust is broken the crust is broken apart and squeezed apart and squeezed together!together!

These plates which These plates which holdhold the continents the continents have moved location have moved location and thus affected life and thus affected life forms!forms!

Where these plates Where these plates meet cause meet cause earthquakes, and earthquakes, and volcanic activity!volcanic activity!

From Chemistry-Radiometric From Chemistry-Radiometric Dating ...Dating ...

RadioisotopesRadioisotopes--an an unstable atom (extra unstable atom (extra neutrons)neutrons)

Radioactive DecayRadioactive Decay the breakdown into the breakdown into smaller more stable smaller more stable atoms.atoms.

Half-lifeHalf-life is the time is the time needed for 1/2 of the needed for 1/2 of the substance to change!substance to change!

TYPESTYPES Carbon 14Carbon 14 –decays to –decays to

Nitrogen.Nitrogen. half-life 5,730 years.half-life 5,730 years. PotassiumPotassium- - decays to decays to

Argon then to calcium. Argon then to calcium. half-life 1.3 -5.2 billion half-life 1.3 -5.2 billion yearsyears

Uranium 238Uranium 238 –decays to –decays to lead. Dating….half life lead. Dating….half life 704 million years704 million years

GEOLOGIC TIME SCALE GEOLOGIC TIME SCALE

The History of the Earth The History of the Earth is divided into Four Erasis divided into Four Eras PrecambrianPrecambrian-oldest -oldest

fossils of cells / fossils of cells / water invertebrateswater invertebrates

Paleozoic Paleozoic -fish and -fish and plants appearplants appear

MesozoicMesozoic- age of - age of the Reptilesthe Reptiles

CenozoicCenozoic- Mammals- Mammals

Mass Extinction…..Mass Extinction…..

5 major mass 5 major mass extinctionsextinctions

A time when A time when suddenly large suddenly large numbers of species numbers of species become extinct !become extinct !

Sudden Geological Sudden Geological changes occur..changes occur..

AsteroidsAsteroids Volcanic eruptions Volcanic eruptions

If Life comes from Life…. If Life comes from Life…. Where or How did the first life form Where or How did the first life form

arise???………...arise???………...

J.B. HaldaneJ.B. Haldane – and- – and- Alexander OparinAlexander Oparin - -

hypothesized life hypothesized life began in the oceans began in the oceans from complex organic from complex organic molecules!molecules!

Harold Urey- and Harold Urey- and Stanley Miller -Stanley Miller - 1953 1953 set up a test to see if set up a test to see if the hypothesis had the hypothesis had merit!merit!

The Primordial Soup !The Primordial Soup !

Stanley Miller’s experiment with the help Stanley Miller’s experiment with the help of Harold Urey of Harold Urey produced amino acids, produced amino acids, sugars, and other organic compounds!sugars, and other organic compounds!

Similar processes have Similar processes have produced ATP- produced ATP- energy carrier, and nucleic acids- the energy carrier, and nucleic acids- the building blocks for DNA!building blocks for DNA!

BUT- If there was NO OZONE layer this BUT- If there was NO OZONE layer this process could not have happened!process could not have happened!

The Bubble Model…The Bubble Model… Louis Lerman – molecules Louis Lerman – molecules

for life formed within for life formed within bubbles on the surface of bubbles on the surface of the oceanthe ocean..

gases trapped in ocean gases trapped in ocean vents formed bubblesvents formed bubbles

methane and ammonia methane and ammonia made amino acids made amino acids released into atmospherereleased into atmosphere

UV rays forced further UV rays forced further molecular changemolecular change

these fell back into the these fell back into the ocean and repeated the ocean and repeated the cycle.cycle.

Proto cells…Proto cells…

LIPIDS LIPIDS – (fats) form bubbles in water.– (fats) form bubbles in water. COACERVATESCOACERVATES- amino acids and sugars - amino acids and sugars

form bubbles with cell membrane like form bubbles with cell membrane like structure.structure.

MICROSPHERESMICROSPHERES – amino acid chains form – amino acid chains form bubblesbubbles

Scientists Cech and Altman showed that Scientists Cech and Altman showed that RNA can reproduce itself and can modify RNA can reproduce itself and can modify its structure over time.its structure over time.

What are these precursors of What are these precursors of the first cells??the first cells??

Scientists disagree about the details Scientists disagree about the details of the process that led to the origin of the process that led to the origin of life. of life.

Most scientists accept that under Most scientists accept that under certain conditions.certain conditions.

The basic molecules of life could The basic molecules of life could have formed spontaneously through have formed spontaneously through simple chemistry.simple chemistry.

Simple to Complex Simple to Complex Molecules?Molecules?

There is a huge difference between There is a huge difference between simple and large complex molecules simple and large complex molecules found in living things.found in living things.

How did amino acids link to form How did amino acids link to form proteins? How do nucleotides come proteins? How do nucleotides come together to form long strains of DNA that together to form long strains of DNA that store the instructions for making store the instructions for making proteins??proteins??

In the lab, Scientists cannot make In the lab, Scientists cannot make proteins nor DNA form spontaneously in proteins nor DNA form spontaneously in water.water.

But get this……But get this……

Scientists have made short chains of RNA, Scientists have made short chains of RNA, the nucleic acid that helps carry out DNA’s the nucleic acid that helps carry out DNA’s instructions.instructions.

These RNA molecules have been able to These RNA molecules have been able to form by themselves in water!form by themselves in water!

Turns out that RNA molecules can act as Turns out that RNA molecules can act as enzymes to form DNA.enzymes to form DNA.

Therefore, RNA was the first information Therefore, RNA was the first information storing molecule and it catalyzed the storing molecule and it catalyzed the assembly of the first proteins. This molecule assembly of the first proteins. This molecule changed from generation to generation.changed from generation to generation.

LipidsLipids

Lipids tend to gather together in Lipids tend to gather together in water. (Fats are not water soluble water. (Fats are not water soluble and are hydrophobic.)and are hydrophobic.)

When some lipids are combined with When some lipids are combined with other molecules, they form tiny other molecules, they form tiny droplets with a surface that looks like droplets with a surface that looks like a cell membrane.a cell membrane.

MicrospheresMicrospheres

Another lab experiment shows that in Another lab experiment shows that in water, short chains of amino acids water, short chains of amino acids can gather into tiny droplets called can gather into tiny droplets called MICROSPHERES.MICROSPHERES.

CoacervatesCoacervates

Another tiny droplet is made out of Another tiny droplet is made out of molecules of different kinds., molecules of different kinds., including linked amino acids and including linked amino acids and sugars.sugars.

What does all this mean?What does all this mean?

Scientists think that formation of Scientists think that formation of microspheres might have been the first microspheres might have been the first step of creating a cell. One theory says step of creating a cell. One theory says that microspheres fomed, lasted a while, that microspheres fomed, lasted a while, and then dispersed.and then dispersed.

Over millions of years, some microspheres Over millions of years, some microspheres were able to “survive” because they were able to “survive” because they blended with other molecules and energy. blended with other molecules and energy. Not living cells though because lacked Not living cells though because lacked heredity!heredity!

Origin of heredityOrigin of heredity

Even though scientists disagree Even though scientists disagree about the details of the origin of about the details of the origin of heredity, many agree that double heredity, many agree that double stranded DNA evolved after RNA and stranded DNA evolved after RNA and that early RNA catalyzed the that early RNA catalyzed the production of the first proteins.production of the first proteins.

So we So we stillstill don’t know how life don’t know how life started naturally and spontaneously.started naturally and spontaneously.

The Evolution of PROKARYOTESThe Evolution of PROKARYOTES The oldest known The oldest known

fossils are the fossils are the PROKARYOTES.PROKARYOTES.

CYANOBACTERIA- CYANOBACTERIA- blue green algae blue green algae produced the produced the OXYGEN in air !!OXYGEN in air !!

Ancient prokaryotes Ancient prokaryotes are called are called ARCHAEBACTRIA.ARCHAEBACTRIA.

The first EUKARYOTE CELLSThe first EUKARYOTE CELLS1.5 Billion years ago…1.5 Billion years ago…

first fossils of Eukaryotes!first fossils of Eukaryotes!

Eukaryotes have organelles Eukaryotes have organelles within..(Nucleus and otherswithin..(Nucleus and others))

Archaebacteria-Archaebacteria-

Cyanobacteria-Cyanobacteria- developed developed into into Chloroplasts and Chloroplasts and MitochondriaMitochondria

Endosymbiosis Endosymbiosis occurred..occurred..

forming first Eukaryote cellforming first Eukaryote cell

The ENDOSYMBIOTANT The ENDOSYMBIOTANT HYPOTHESISHYPOTHESIS

Lynn Marguli –Lynn Marguli – Proposed Proposed prokaryote cells prokaryote cells engulfed smaller engulfed smaller cells and formed cells and formed a symbiotic a symbiotic relationship – of relationship – of mutualism…..mutualism…..

where both benefit!where both benefit!

Evidence-Evidence-Mitochondria –Mitochondria –same size same size

as bacteriaas bacteria

Chloroplasts and Chloroplasts and Mitochondria have Mitochondria have membranes like membranes like bacteriabacteria

Both have Both have there own there own DNADNA

BothBoth –have ribosomes –have ribosomes like bacterialike bacteria

Both-Both- Reproduce like Reproduce like bacteriabacteria

MulticellularityMulticellularity

Unicellular Unicellular organisms unite organisms unite to formto form

multi-cellular multi-cellular

organismsorganisms

Specialization –Specialization – cells become cells become specialized for a specialized for a particular functionparticular function

Protists – Primative unicellularand multicellular organisms

OZONE LAYEROZONE LAYERAs ozone formed , it allowed As ozone formed , it allowed

life to move onto the life to move onto the land….land….

First FungiFirst Fungi as it can absorb as it can absorb mineralsminerals

Plants need the minerals to Plants need the minerals to carry on photosynthesis…carry on photosynthesis…they came next..they came next..

MYCORRHIZAE-MYCORRHIZAE- fungi and fungi and plants in a symbiotic plants in a symbiotic relationship of Mutualism!relationship of Mutualism!

Invertebrates--Invertebrates--arrivearrive Arthropods followed plantsArthropods followed plants

insects – spiders- centipedes-etcinsects – spiders- centipedes-etc

Vertebrates…Vertebrates…

....fish were evolving as the fish were evolving as the arthropods developed on land..arthropods developed on land..

. Amphibians evolved from fish. Amphibians evolved from fish

.Reptiles developed the egg.Reptiles developed the egg

.Birds developed from reptiles.Birds developed from reptiles

.Reptiles gave rise to the .Reptiles gave rise to the mammalsmammals