Heterotrophic Bacteri4

Heterotrophic Bacteri4 - prokaryote (or perhaps early...

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Heterotrophic Bacteria Members of this large and diverse group must derive their energy from another organism by feeding. Two main types: saprophytic and symbiotic . Saprophytes feed on dead or decaying material and are important nutrient recyclers. Symbiotic bacteria live within a host multicellular organism and contribute to the health of the host. Examples include cows and other grazing animals: the bacteria convert cellulose from plant leaves and stems eaten by the animal into glucose for digestion by the animal. Normally cellulose is nondigestible. Possible symbiosis of bacteria within early eukaryotic cells was a major step in the evolution of eukaryotic cells. In 1980, Lynn Margulis proposed the theory of endosymbiosis , diagrammed in Figure 15, to explain the origin of mitochondria and chloroplasts from permanent resident prokaryotes. According to this idea, a larger
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Unformatted text preview: prokaryote (or perhaps early eukaryote) engulfed or surrounded a smaller prokaryote some 1.5 billion to 700 million years ago. Instead of digesting the smaller organisms the large one and the smaller one entered into a type of symbiosis known as mutualism , where both organisms benefit and neither is harmed. The larger organism gained excess ATP provided by the "protomitochondrion" and excess sugar provided by the "protochloroplast", while providing a stable environment and the raw materials the endosymbionts required. This is so strong that now eukaryotic cells cannot survive without mitochondria (likewise photosynthetic eukaryotes cannot survive without chloroplasts), and the endosymbionts cannot survive outside their hosts. Nearly all eukaryotes have mitochondria....
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