Historical Development of the Concept of Life Lesson Outline

Earth's Age and Formation

• Earth's age is approximately 4.5 billion years
• The early Earth was violent, disorderly, and chaotic due to "Accretional Energy"
• Life did not emerge immediately after Earth's formation, taking hundreds of millions of years to appear

Fossil Discoveries

• Microfossils (4.28 billion years old) were discovered in hydrothermal vent precipitates
• Undisputed evidence of life dates back to at least 3.5 billion years ago

Early Life Forms

• Prokaryotes (cells without a nucleus, such as bacteria and archaea) were among the first life forms
• The early atmosphere was rich in nitrogen, carbon dioxide, and deficient in oxygen (anoxic environment)
• Anaerobic organisms were capable of surviving without oxygen

Photosynthesis and Oxygen

• Cyanobacteria (blue-green algae) conducted photosynthesis using sunlight, oxygen, and carbon dioxide
• This process introduced oxygen into the atmosphere, transforming it

Unicellular and Multicellular Organisms

• Unicellular organisms eventually evolved into multicellular organisms
• Evolution plays a crucial role in the development of life

Theories on the Origin of Life

• Creation Theory: the concept of divine creation, where all life forms are created by a supreme being
• Abiogenesis Theory (Spontaneous Generation): the idea that life can appear from non-living material
• Biogenesis Theory: life originated from pre-existing life
• Fossils provide strong evidence that many life forms existed on Earth in the past 3.5 billion years

Key Scientists

• Alexander Ivanovich Oparin (1920): proposed theories about the origin of life in his book "The Origin of Life"
• John Scott Haldane (1920s): conducted self-experiments, leading to significant discoveries in physiology