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24. Evolution eLearn.Punjab

Figure 24.1: Two hypothesies on the evolution of the eukaryotic cell. (a) Endosymbiont hypothesis, (b) Membrane invagination
hypothesis. (1) A prokaryotic cell (2) Duplicates its genetic material (genome) (3) The plasma membrane then invaginates to form
double membrane-bound organelles, and the individual genomes separate from each other (4) The nuclear genome eventually
enlarges, while the other organelle genomes lose many of their genes, resulting in a eukaryotic cell.

INHERITANCE OF ACQUIRED CHARACTERISTICS

Toward the end of the eighteenth century, several naturalists suggested that life had

evolved along with the evolution of earth. But only one of Darwin’s predecessors

developed a comprehensive model that attempted to explain how life evolves. Jean

Baptiste Lamarck (1744-1829) published his theory of evolution in 1809, the year

Darwin was bom. Lamarck was in-charge of invertebrate collection at the Natural

History Museum in Paris. He presented a mechanism to explain how specific

adaptations evolve. Lamarck argued that those parts of the body used extensively

to cope with the environment become larger and stronger, while those that are not

used deteriorate.

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