Definitions [5]
Definition: Biogenesis
Biogenesis is the idea that life arises only from pre-existing life.
Definition: Abiogenesis
Abiogenesis is the concept that living organisms can arise naturally from non-living substances.
Definition: Autogenesis
Autogenesis is another term for spontaneous generation, meaning self-origin of life from non-living matter.
Definition: Natural Selection
The process where organisms with favorable variations survive and reproduce more successfully than others is called natural selection.
Definition: Survival of the Fittest
The concept where only well-adapted individuals survive in the struggle for existence is called survival of the fittest.
Key Points
Key Points: Origin of Life on Earth
- The origin of life is a unique event; Earth formed about 4.5 billion years ago, and life appeared about 4 billion years ago.
- Special Creation Theory: all organisms were created by a supernatural power; religion-based, no scientific proof.
- Cosmozoic Theory (Panspermia): life came from other planets as spores; not accepted, as it doesn't explain life's origin elsewhere.
- Spontaneous Generation (Abiogenesis): life arose from non-living matter; later disproved.
- Biogenesis: life arises only from pre-existing life; explains continuity but not the first origin.
- Redi (1668): maggots appeared only in the uncovered meat jar, showing they came from fly eggs.
- Spallanzani (1767): sealed boiled broth showed no growth, proving microbes come from air.
- Pasteur (1861): swan-neck flask trapped airborne microbes, conclusively disproving spontaneous generation.
