The Origin of Life and Evolutionary Theory Explained

The Origin of Life: Two Key Processes

1. Chemical Evolution

This process created the molecules that make up living things (biomolecules) and subsequently formed structures called protocells.

• Biomolecule Formation: Simple organic molecules originated from meteorites.
• Complexification: More complex biomolecules were created from simple molecules in the primordial soup (the first biomolecules on the planet).
• Protocell Formation: Protocells were formed when biomolecules became organized into hollow, spherical membranes containing proteins and nucleic acids.

2. Biological Evolution

This process led protocells to become different types of cells, resulting in all the organisms that have ever inhabited the Earth.

• Primitive Cells: Similar to prokaryotic cells, these formed when some protocells managed to exchange matter and energy, regulate themselves, and reproduce.
• Cell Diversification: Different types of prokaryotic cells were created from primitive cells (heterotrophic, photosynthetic, and mobile cells).
• Eukaryotic Cells: The first eukaryotic cells appeared as a result of endosymbiosis.

Theories on the Origin of Biodiversity

Fixism and Catastrophism

Fixism suggests species remain as they were created, though some have gone extinct. Cuvier later proposed the theory of catastrophism to explain species disappearance.

Evolutionary Theories

Naturalists proposed actualism and evolutionism:

• Actualism: The same events that occurred in the past are occurring now; changes take place slowly, constantly, and gradually.
• Evolutionism: Lamarck observed fossils and realized that some species could descend from others.

Lamarck's Theory

1. Spontaneous Generation: Simplest life forms become more complex.
2. Internal Impulse: Organisms develop according to their needs.
3. Inheritance: These changes are passed to descendants, creating new species.

Darwin's Theory

Darwin and Wallace supported the same theory, but Darwin provided the most comprehensive evidence. His hypothesis includes:

• The world is not static.
• The process of change is gradual and continuous.
• Similar organisms are related.
• Evolutionary change is the result of natural selection.

Neo-Darwinism (Synthetic Theory)

A revised version of natural selection, enriched by contributions from genetics, paleontology, and taxonomy.