3. The Evolution of Cells

3.0 Introduction

Primitive autonomous organisms, the bacteria, are essentially composed of a tough membrane that separates the inner environment from the exterior. Hooked onto this membrane is a dense string of circular double-stranded nucleic acid of the DNA type. The remainder of … Continue reading

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3.1 The Prokaryotes

3.1.1 The bacteria 3.1.1.1 The common ancestor Debate on the origin of life centers on the question as to whether the cradle of life is hot or cold. With no fossils to rely on, indirect clues are evaluated. The hotter … Continue reading

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3.2 The Eukaryotes

3.2.1 The origin of the eukaryotes The way eukaryotes could emerge and evolve from a more primitive organism is one of the great questions debated, and a number of explanations have been put forward. In 1977, Woese and Fox presented … Continue reading

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3.3 Sexual Reproduction

The number of nucleic acid bases actively engaged in protein synthesis is about 106 in bacteria. The probability or error in replication of these bases is about 10-6. An exchange of genetic material seems to be the only way in … Continue reading

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3.4 The Appearance of the Metazoa

It is highly unlikely that large amounts of free oxygen in the atmosphere of the earth could have been produced before the advent of oxygen-producing blue-green algae. The only significant abiotic source of atmospheric oxygen is provided by the decomposition … Continue reading

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3.5 Evolution is not Chance but Necessity

On celestial bodies endowed with water as the principal solvent, one would expect the evolution of Life to have proceeded – under appropriate conditions – in a way similar to that on earth. The origin of life and the evolution … Continue reading

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