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Persuade a creationist that the endosymbiont theory is correct.

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Introduction

Persuade a creationist that the endosymbiont theory is correct. all life forms on Earth are made of cells. Eukaryotic cells have a cell nucleus separated from the rest of the cell contents (the cytoplasm) by a nuclear membrane. The nucleus contains DNA on chromosomes, whilst within the cytoplasm are distinct membrane-bounded organelles, which perform specific tasks. The more ancient prokaryotic cells on the other hand, (bacteria and Cyano-bacteria) carry their genetic material in simple strands of DNA that is not separated from the cytoplasm by a nuclear membrane. They reproduce asexually. Eukaryotic cells reproduce sexually, mixing genes between individuals and passing genetic variations to their offspring. Sexual reproduction allows more genetic combinations, so only not can eukaryotic cells be larger and more complex than prokaryotic cells, but also their ability for sexual reproduction made it more plausible for multi-cellular plants and animals to evolve. Eukaryotic cells are therefore the key to the evolution of the diversity of plant and animal life on our planet. The new techniques of functional genomics, now enabling the sequencing of the entire genomes of organisms. The new science, often automated, provides scientists with vast quantities of data. ...read more.

Middle

This idea was based on observations of cell structure, the biochemistry taking in the organelles and the fact that mitochondria and chloroplasts had unique genes that did not appear in the cell nucleus. It was an interesting theory that took over seven decades to become respectable. In the 1960's, the biologist Lynn Margulis put forward what was to become known as the Endosymbiont Hypothesis. In 1970 her book "Origin if Eukaryotic Cells" was published, followed by "Symbiosis in Cell Evolution" in 1981. Although now accepted as mainstream, the idea was treated with scepticism and even ridicule for several years, according to Professor John Allen: - "To a student in the 1960's and 1970's it was still a hypothesis. It was still a bit wacky, still on the fringe. People might want to talk about it over coffee, but you wouldn't set examination questions on it, because it wasn't real! It's mainstream stuff now. These things were once free-living bacteria. It's quite inconceivable that it could be otherwise. And it raises questions: what sort of bacteria and what evolutionary forces were at work? And why did they lose so many genes? ...read more.

Conclusion

During the history of plant cells, complex rearrangements of the genes responsible for photosynthetic machinery have taken place. These have included the loss and gain as well as the transfer of genetic material between the original endosymbionts Co-evolution took place of genes in the organelles and in the nucleus. As a result, genes and intracellular signalling are very specific, tailored to each individual partnership. Consequently, organelle changes between even closely related species can result in disturbance of the intra cellular genetic balance because of incompatibility. Throughout the evolution of plastids, genes were transferred to the nucleus of the host cell with major consequences for the regulation of gene expression. Although the genes themselves have been lost to the nucleus, the plastid retains a role in the manufacturing of proteins necessary for photosynthesis, the plastids and the nucleus is involved in regulating the expression a set of nuclear genes that encode proteins required for photosynthesis and related processes. Two and a half billion years of co-existence and co-evolution are summed up by a theory known as endosymbiosis. It explains the origin of organelles seen inside eukaryotic cells, notably mitochondria and chloroplasts. In a nutshell, the endosymbiotic theory is that mitochondria evolved from bacteria living within their host cell. Chloroplasts evolved from endosymbiotic cyanobacteria; that is from prokaryotic organisms able to synthesise organic constituents from inorganic sources. ...read more.

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