Origin of Life on Earth

Origin of Life on Earth

• Life is defined as the existence of a living thing, especially a human being, characterized by growth through metabolism, reproduction, and adapting to surroundings through internal changes.
• Scientists have dedicated themselves to understanding the first appearance of life on Earth.
• The Primordial Soup Theory proposes that life arose from organic molecules in a soup-like mixture.

Primordial Soup Theory

• Alexander Oparin, a Russian Biochemist, theorized about the origin of life and wrote the book "The Origin of Life."
• John Haldane, a Scottish Physiologist, also contributed to the understanding of gas nature and the human body.
• This theory suggests that energy from lightning combined with atmospheric chemicals created amino acids, the building blocks of proteins, in a primordial soup.

Electrical Discharge Experiment

• Stanley Miller and Harold Urey conducted experiments to test the primordial soup theory.
• They simulated early Earth conditions (methane, ammonia, water, hydrogen) by creating closed systems and applying electrical sparks.
• Their findings showed the formation of amino acids from the simulated environment.

Thermal Synthesis

• Sidney Fox's experiments demonstrated the origin of life by using a specific mixture of pure, dry amino acids.
• Upon heating the mixture, an aqueous solution formed and cooled into microscopic globules called proteinoid microspheres.
• These globules exhibited characteristics like budding, comparable to the reproduction of coccid bacteria, and were seen as the origin of protocells.

Protocell Experiment

• Jack Szostak's experiments involved a nucleic acid genome and a lipid sac.

Differences between DNA and RNA

• DNA is a double-stranded molecule with a long chain of nucleotides.
• RNA is a single-stranded molecule with a shorter chain of nucleotides.

Early Forms of Life

• About 3.5 billion years ago, the first form of life likely emerged.
• Microfossils, fossils of tiny plants and animals, serve as crucial evidence of early life.

Microfossils

• Microfossils are fossils that retain remains of tiny plants and animals.
• Some early organisms lacked a nucleus and were called prokaryotes.

Photosynthetic Organisms

• Photosynthetic organisms, like cyanobacteria, increased the oxygen present in Earth's early atmosphere.

Cyanobacteria

• Cyanobacteria are the first known photosynthetic organisms.
• Their microfossils are easily identifiable, and they left chemical fossils from broken pigments.
• The earliest microfossils were found in rocks approximately 1.5 billion years old.
• The presence of these microfossils signals the beginning of eukaryotic organisms on Earth.