The document discusses the origin of life, presenting various theories with a focus on the primordial soup theory, which suggests life began from organic molecules formed in the Earth's early chemical environment. It describes the emergence of the first life forms, prokaryotes, and their evolution into multicellular organisms, highlighting the role of photosynthetic organisms in altering the atmosphere. Additionally, it summarizes key experiments by scientists like Stanley Miller, Sidney Fox, and Jack Szostak that explored the conditions and processes leading to the formation of life.

1. INTRODUCTION TO
LIFE SCIENCE

2. THE ORIGIN OF LIFE
• THERE ARE MANY THEORIES ABOUT THE ORIGIN OF LIFE.
SOME BELIEVED THAT LIVING ORGANISM PUT TO EARTH
BY SOME DIVINE FORCES
• OTHER SAYS THAT LIFE DID NOT ORIGINATE FROM EARTH
BUT FROM OTHER PLANETS
• BUT AMONG SCIENTISTS ,THE MOST ACCEPTED THEORY
ISTHAT LIFE CAME INANIMATE MATTER

3. PRIMORDIAL SOUPTHEORY OR PREBIOTIC SOUP IS A HYPOTHETICAL
CONDITION OFTHE EARTH’S ATMOSPHERE BEFORETHE EMERGENCE
OF LIFE. IT IS A CHEMICAL ENVIRONMENT IN WHICH THE FIRST
BIOLOGICAL MOLECULES WERE FORMED UNDER NATURAL FORCES
PRIMORDIAL SOUP THEORY
PROPOSED BY “ ALEXANDER OPARIN AND JOHN HALDANE “
LIFE STARTED IN PRIMORDIAL SOUP OF ORGANIC MOLECULES.
SOME FORM OF ENERGY FROM LIGHTNING COMBINED
WITHTHE CHEMICALS INTHE ATMOSPHERE TO MAKE NEW
BUILDING BLOCKS OF PROTEIN KNOWN ASTHE AMINO ACIDS

4. EARLY FORM OF LIFE
• THE FIRST FORM OF LIFE IS BELIEVED TO HAVE APPEARED SOME 3.5
BILLIONYEARS AGO.THE FIRST EVIDENCE OF LIFE IS FOUND ON
MICROFOSSILS .
• MICROFOSSILS ARE FOSSILS THAT CONTAIN THE REMAINS OFTINY
PLANTS AND ANIMALS.THEY AREVERY SMALL AND CAN BE IDENTIFIED
UNDER MICROSCOPE.
• SOME OFTHE REMAINS OF ORGANISMS DO NOT HAVE A NUCLEUS SOTHEY
WERE CALLED PROKARYOTES

5. • THEY ARE KNOWNTO BE THE EARLIEST FORMS OF LIFE.
• THEY HAVE SURVIVED THE EXTREME CONDITIONS OFTHE EARLY
ENVIRONMENT.
• THEY STARTEDTO MAKETHEIR OWN FOOD BY UTILIZING THE ENERGY
FROMTHE SUN AND CARBON DIOXIDE INTHE ATMOSPHERE
• THESE ARETHE PHOTOSYNTHETIC ORGANISMS .THE PROCESS OFTHE
PHOTOSYNTHESIS PRODUCED MORE OXYGEN THAT CHANGED THE
EARTHS ATMOSPHERE
• THIS CHANGE INTHE ATMOSPHERE ALLOWED OXYGEN –BREATHING
ORGANISMSTO EXIST.

6. • CYANOBACTERIA ARETHE FIRST PHOTOSYNTHETIC ORGANISMS TO
FORM.
• THEIR MICROFOSSILS ARE AMONG THE EASIEST TO RECOGNIZE.
THEIR MORPHOLOGY REMAINED THE SAME ANDTHEY LEFT
CHEMICAL FOSSILS INTHE FORM OF BROKEN PRODUCTS FROM
PIGMENTS .

7. HOW DID MULTICELLULAR ORGANISMS EVOLVED
• Multicellular organisms are believed to have evolved from unicellular
eukaryotes. Some single eukaryotic cells, like unicellular algae , formed
multicellular aggregates through colonial aggregates, the organisms evolved
to form multicellular organisms through cell specialization.
• Protozoans, sponges , and fungi came to being
• The first fossilized animal which were discovered 580 million years ago
were soft-bodied.
• According to Charles Darwin, corganisms changed over time as a result of
adaptation to their environment in order to survived.

8. CLASSICAL EXPERIMENTS THAT LEADS
TO THE DISCOVERY OF FIRST LIFE

9. HOW DID LIFE BEGIN ON EARTH ?

10. • One of these theories is the primordial soup theory proposed
by alexander Oparin and John Haldane
• According to this Theory, life started in a primordial soup of
organic molecules . Chemicals from atmosphere and some
form of energy from lightning combined to make amino
acids which are the building blocks protein.

11. ELECTRICAL DISCHARGE EXPERIMENT
• Stanley Miller and Harold Urey verified the primordial soup theory
by simulating the formation of organic molecules on the early
Earth. They confined methane, ammonia, water, and hydrogen in a
closed system and applied continuous electrical sparks to trigger
the formation of the building blocks of life. After a day, they
observed a change of color in the solution. After a week, the
solution was tested, and they found out that several amino acids
were produced. The purpose of this experiment was not to try and
produce amino acids, rather, its purpose was to explore the
conditions of the early Earth and what the naturally occurring
results would be.

12. THERMAL SYNTHESIS
• Sidney Fox demonstrated in his experiment the origin of life using a
specific mixture of pure, dry amino acids. In his experiment, after
heating the mixture, an aqueous solution was formed and cooled into
microscopic globules called protenoid microspheres. The globules
looked like coccoid bacteria and seemed to be budding, which is a form
of reproduction in some microorganisms. He claimed that the protenoid
microspheres constituted protocells – almost true cells, and
multiplied through division like true cells. He believed that these cells
were the link between the primordial environment and the true living
cells.

13. THE PROTOCELL EXPERIMENT
• Jack Szostak contemplated on how early life forms formed in a primordial
chemical environment. He then thought that the simplest possible living cells or
protocells just required two components to be formed: a nucleic acid genome to
transmit the genetic information and a lipid sac which encapsulated the genome
and let itself grow and divide. Szostak built lipid sacs made in fatty acids and a
replicase – an RNA molecule that catalyzes its own replication, in the test tube.
He found out that lipid sacs with more RNA grew faster. He suggested that such
test tube evolution was possible. The results suggested that the early forms of life
with just a single gene, an RNA gene, could have undergone a Darwinian evolution.