ProjectProjectProjectORIGIN OF LIFE ORIGIN OF LIFE

ON EARTHON EARTH

ASSIGNMENT CHEMICAL AND ORGANIC EVOLUTION OF EARTH

Group Leader: Fatima Tuzahra Assistant: Faryal Zahra Abeera Ishaq Tayyaba Khalil

WHAT IS SCIENCE?• Universe seems to

operate under some principles .In order to understand these principles some experiments are done and observations are made on the basis of which logical conclusions are drawn.Such studies are called science.

Biology Biology is the scientific study of living things.The word bios means life and logos means thought discourse or reasoning.

Origin of Life (According To Halden And Oparin)

Light elements present at the surface

of earth in vapours and responsible for

origin of life Origin of life and solar

system came into being together Heavy elements are

present in the centre of earth

Conditions of New Existing Earth

• Earth had high temperature and radiation and had frequent and abundant electric discharges.

• Simple inorganic molecules slowly and gradually combined to produce complex organic molecules from which the simplest form of life came into existence.

Primitive Earth’s Atmosphere Atmosphere had

carbon dioxide,ammonia and water vapours.

Mixture of these gases leads to organic compounds under ultraviolet radiations in the absence of oxygen.

Origin Of First Life Organic compounds

accumulated together in seas.

The accumulated sugars and amino acids give rise to polymers.

Polymers combined and give rise to microscopic organisms.

Oxygen was still absent.

Verification of Oparin and Halden Hypothesis(by other scientists)

In 1953,Stanley Miller and Harold Uray made a first successful attempt in U.S.A.

Primitive Earth conditions were simulated in laboratory.

In the result of which Ammonia,fatty acids and urea are formed.

Life of Primitive Organisms Fossils indicates that

earliest life lived about 3.8 billion years ago.

It is speculted that earliest life started about 4 billion ago.

Bacteria(the earliest organism) are primary hetrotrophs and are anaerobes.

Primitive Autotrophs Lack of pre-existed food

led to the evolution of Autotrophs.

They succeeded in establishing themselves and reproduced in that environment.

Early Autrotrophs used hydrogen sulphide instead of water.

When hydrogen sulphide depleted they started using water.

Difference Between Primitive and Present Photosynthetic Process

CO2+12H2S light C6H12O6+12S+6H2O

6CO2+12H2O light C6H12O6+6O2+6H2O

Evolutionary Change Due To Autotrophs Photosynthesis led to the

accumalation of oxygen. Ozone formation and

accumaltion started with the increase in oxygen.

Ozone Layer penetrate the ultra violet radiations to earth surface.

Aerobes(prokaryotic and unicellular)were produced.

Necessity of Photosynthetic organisms.

Evolution of Eukaryotes and existing multi-cellular organisms from prokaryotes

REFERENCES Encarta

Encyclopedia www.google.com www.nationalgeogr

aphic.com www.edu.com Biology 9 (Punjab

Text Book Board) www.hotmail.com www.wikipedia.co

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