English Origin Of Life In Universe

ORIGIN OF LIFE

The facts……. hidden somewhere The story….….. unrevealed

The truth….. not known exactly The path…. untraced

An attempt to explore the way!!! An effort to blend biology, chemistry,

and physics in the search to identify and understand the origin of life in the

universe

It’s a “Journey Back In Time”…By Kalpana Stuti, Ritu, Gauri

Miranda House

ORIGIN OF LIFE

BIG BANG

Cosmic dust and gases+ H2O

Oceans

Haldane soup

Reducing atmosphere(gases like CH4,NH3,N2,CO2,H2O responsible for abiotic synthesis of organic compounds)

OPARIN-HALDANE THEORY Haldane Soup

Simple Molecules

Complex Molecules (building blocks)

Aggregates (coacervates and microspheres)

Protocells( proprimitive stage before formation of true cell

Proto cells + nucleic acid = self replicating system

“CELL”

Microsphere

ENERGY YIELDING SYSTEM

• “Cell” Energy Yielding System

• Chlorophyll development Photosynthesis

O2 evolved

Ozone Formation (shielding effect)

• Atmosphere changed to oxidizing from reducing.

• Evolution of photosynthesis which is followed by respiration.

CELL

Replication Metabolism Homeostasis

Anaerobes Aerobes

Chemotrophs Heterotrophs

Chemoheterotrophs Chemoautotrophs

Prokaryotic Cells Eukaryotic cellEndosymbiotic Theory

How Eukaryotic Cell Changed to Multicellular Organism….

EVIDENCES???

• Geological Evidence

• Precambrian Fossil Evidence

• Laboratory Evidence

GEOLOGICAL EVIDENCE• Sedimentary rock in past 500 million years are

silicate sands clay, quartz type indicating oxidizing conditions.

• Ancient Precambrian sediments containing sands with reduced iron minerals found in Canada, Brazil, South Africa.

• Banded iron ore deposits with mixed oxidation states in Quinland, Russia, India and Australia

PRECAMBRIAN FOSSIL EVIDENCE

• Elso Barghoorn et al studied polished thin sections of silica rich cherts from Gunflint region of Northern Minnesota and Southern Canada with optical and electron microscope.

• Living organisms algae, fungi, microbes associated with banded iron ore cherts indicates that they were probably laid down under reducing atmospheric conditions.

LABORATORY EVIDENCE MILLER & UREY EXPERIMENT

•

•A mixture of H4,NH3, H2, and water was put into a flask and energized by an electrical discharge apparatus to represent ultraviolet radiation .

•The products were allowed to condense and collect in a lower flask.

•. After a week, Miller and Urey found a dark brown scum had collected in the lower flask and was found to contain several types of amino acids together with sugars, tars, and various other unidentified organic chemicals.

How could polymer form in dilute aqueous solution when polymerization is a dehydration process?

• Sidney Fox experiment – Fox found that dry amino acids heated to 160-210OC, forms polymers of molecular weight 300,000 provided mixture contains Aspartic Acid and Glutamic Acid. Thermal protenoids so formed, if washed with water, form microspheres of fairly uniform diameter of 20, 000Ao

• Cinder Cone Hypothesis - Protenoid material first polymerized on hot dry volcanic Cinder Cones and then it was leached into oceans by rains to form microspheres.

These became early segregated chemical systems and eventually led to protocells.

COACERVATES• They tend to concentrate

some molecules in their interior and this in an ability that most primitive protocells would have acquired. Behavior of Coacervate shows how earlier protocells would have achieved internal compositions that were different from their surroundings and could have developed certain amount of chemical evidences.

Coacervate droplets formed by interaction between gelatin and gum arabic. A. I. Oparin

Amylase

Sunlight

Ascorbic Acid + Dye

Chloroplast e- + Dye

Reduced Dye (colour change)

AmylaseStarch Maltose

PANSPERMIA THEORY

Organic compounds arrived from outer space

It states that hydrocarbons and other organic molecules (molecules that organisms contain or that might lead to the genesis of life) have been found in meteorites –

It means that at least prebiotic chemistry that leads to the primordial soup might be going on there.

Evidences in support of this theory

• In 1969, a meteorite landed in Australia that was 12% water and contained traces of 92 amino acids.

Inference- It points to not only the presence of organic compounds in outer space, but also the capacity of such compounds to reach earth.

• Fred Hoyle and Chandra Wickramasinghe have argued persistently since the 1970s that complex organic substances, and perhaps even primitive organisms, might have evolved on the surface of comic dust grains in space and then been transported to the Earth's surface by comets and meteorites.

Where did life begin???• There is an ongoing debate regarding the most probable site of

life's origins.

• The prevailing paradigm - life began near the ocean's surface, bathed in sunlight.

• Current Research - life arose near deep hydrothermal vents which is still under investigation.

"Scientists have long suspected that life on Earth originated in the ocean and strong evidence now suggests that the earliest life on our planet occurred in the depths of the ocean in the absence of heat and light."

-- Pulse of the Planet, American Museum of Natural History

Miller and Urey found

Photograph from National Geographic magazine

Deep-sea Vents

• Their discovery in late 1970’s stretched our concept of the origin of life on earth.

• Can life exist and that too thousands of meters beneath the surface of sea in absence of sunlight?

• It raised the possibility that earlier vents supplied the energy and chemical precursors for origin of protobionts.

Exploring the deep ocean floor

View of the first high-temperature vent

(380°C) ever seen by scientists during a dive

of the deep-sea submersible Alvin in

1979. Such geothermal vents

are called smokers. This photograph shows a black smoker, but

smokers can also be white, grey, or clear depending on the material being ejected. Photograph by Dudley Foster from RISE

expedition

Vent Community

A vent community in its prime: Pale pink eelpout fish and white brachyuran crabs swim and scuttle among blood-red tube worms

large and small. Scientists are still trying to figure out how the offspring of such organisms disperse over long stretches of

inhospitable seafloor to colonize widely separated vent systems.

Giant Clams

The size of deep-sea giant clams is evident from the hands of a scientist holding them.

(Photograph by William R. Normark, USGS.)

Giant Tube Worms: RIFTIA

• On the bottom of the ocean around deep-sea hydrothermal vents, there is a profusion of life that thrives on the hydrogen sulfide (H2S) gas

released from the vents.and live inside hard, shell-like protective tubes that attach to the rocks.

Giant tubeworms that live around hydrothermal vents on the sea floor. These creatures are about the size of your hand in shallower waters, but in the ocean's deep

they have been found as big as eight feet long!

How they live….• These creatures lack mouths, anuses, intestines and stomachs,

and scientists were at a loss to explain how these were getting nutrients to survive and grow.

• Their insides are lined with bacteria that oxidize the H2S, turning it into usable nutrients for the worms.

• The bacteria, in turn, benefit from the relationship because the worms deliver blood containing hemoglobin which helps the bacteria to break down the sulfides.

• They live in a symbiotic relationship with a bacteria that may hold clues as to how life on earth began billions of years ago.

BIOCHEMISTRY AT THE VENTS

• H2S Oxidation by bacteria

Energy released helps in fixing CO2 into small organic molecules

So this cycle ... is the same metabolic pathway that is utilized by plants in photosynthesis ... takes inorganic carbon dioxide and fixes it into organic compounds that are then food. But, the difference here, the critical difference, is that rather than using sunlight, these animals and bacteria are completely independent of sunlight. They utilize chemical energy to power that reaction.

So, ever imagined a life out of toxic Hydrogen Sulphide?!

Released from vents

Chemical of Life - Ammonia, Produced at Vents

• Hydrothermal vents were the most likely site for NH3 production where inorganic sulphides acted as catalyst.

N2 +NO2 +N03

Presumed to be present in ancient sea

NH3

FeS, 500oC

89% yield, 15 min

FeO

46% yield 15 min

Powdered Basalt.

20% yield

Stable upto 800oC

RESULTS

• Since NH3 cannot survive at temperature above 800oC indicates that nitrogen would have been present only as N2 during early phase of earth’s development.

• Life can exist on thermal and chemical energy as opposed to just sunlight as had been thought in the past. And so what was realized is that photosynthesis was not the only way to support life.

THE BIG BANGFirst proposed by George Lemaître in 1927

Salient Features•Our Universe began as an infinitesimally small, infinitely hot, infinitely dense singularity.

•Then it inflated (big bang), expanded and cooled to the size and temperature of our present Universe.

Timeline of the Big Bang

What happened after the Big Bang?

Time sinceBig Bang

T (K)

< 10-43s Quantum era

~ 10-35s - 10-33s Inflationary epoch

~ 10-6s 1013K Quark --> Hadron transition

Time sinceBig Bang

T (K)

0.01s 1011K · The Universe expands rapidly, scale is doubled every 0.02s.

· it cools, T ~ 1/R.

15s 3 x 109K · Temperature is below threshold for creation of electron/positron pairs.

· e+/ e- annihilate

· The Universe is "reheated" about 35% by annihilation.

3 min 109K Era of Nuclear Reactions

· Nuclei begin to hold together

Time sinceBig Bang

T (K)

3 &1/2 min 108K End of Nuclear Reactions neutrons have been "used-up" forming 4HeUniverse is now 90% H nuclei( p+) & 10% He nuclei

106yr 4000K

Era of Recombinationnuclei & electrons "recombine to form atoms

109yr Era of Galaxy Formation

Evidences for the Big Bang •Galaxies are moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929 •The abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins•Cosmic Background Radiation predicted by Cosmologist George Gamov in 1948 and discovered by Arno Penzias & Robert Wilson of Bell Labs in 1965.

  THE COMPETITORS …

FOR THE THEORY ON ORIGIN OF THE UNIVERSE

• The Bubble Universe / Andre Linde's Self Creating Universe

• The Inflationary Theory (1981, Alan Guth )

• The Protouniverse (white hole theory)

• The Steady State Theory (late 1940’s )

• The Oscillating Universe Theory (1960’s -70’s )

References

• The Cosmos by Carl Sagan• Text Book of Biology by Campbell• The Scientific American• http://scienceweek.com• www.nationalgeographic.com• Humphris, Susan E. and Tom McCollom. “The Cauldron

Beneath the Seafloor,” Oceanus, Vol. 41, No. 2, 1998, 18.• Sawyer, Kathy. “Signs of Earliest Life in Ocean Depths—

Scalding Habitat May Have Supported Microbes, Fossils Indicate,” Washington Post, June 8, 2000.

Nobody understands the origin of life. If they say they do, they are probably trying to

fool you.

— Ken Nealson, 2002

THANK YOU