Protists reference great

Protists reference great - Protists Eukaryotic Cells...

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Protists Eukaryotic Cells Eukaryote cells have membranous organelles , including a nucleus . The first eukaryotic cells are thought to have been protists. They gave rise to fungi, plants, and animals. The diagram below shows evolutionary relationships among the 4 kingdoms. The oldest fossils of eukaryotic cells are 1.5 billion years old although the earliest eukaryotic cells may have arisen 2.1 billion years ago. The oldest fossils of prokaryotes are 3.6 billion years old. Evolution of Aerobic Prokaryotes Earth’s early atmosphere did not contain oxygen. The earliest organisms were anaerobic .
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Photosynthesis produced oxygen. 6CO 2 + 6 H 2 O + Energy C 6 H 12 O 6 + 6O 2 Aerobic organisms evolved because oxygen enables organisms to obtain much more energy from their food then they could without oxygen. Endosymbiotic Theory The endosymbiotic theory states that some eukaryotic organelles evolved from prokaryotes. For example, the mitochondrion, chloroplast, and other plastids originated as prokaryotic cells that came to reside within a host cell. They enabled the host cell to use sunlight as an energy source (the chloroplast) and use aerobic cellular respiration (the mitochondrion). In return, the host cell provided the necessary nutrients, a stable chemical environment, and protection. Evolutionary change eventually resulted in this relationship being obligate. Below: Heterotrophic prokaryotes that engulfed (or became infected by) photosynthetic prokaryotes were able to benefit by using the sugars produced using solar energy. The prokaryotes benefited by receiving necessary nutrients from their host cell. The chloroplast and other plastids evolved from this photosynthetic endosymbiont. The origin of the double membrane surrounding plastids can be seen in the diagram above. The outer membrane originated as part of the plasma membrane of the heterotrophic cell when the photosynthetic cell was engulfed. The inner membrane originated as the plasma membrane of the photosynthetic cell. Below: Mitochondria are eukaryotic organelles that function in aerobic cellular respiration . They may have arisen by anaerobic prokaryotes engulfing aerobic prokaryotes. The anaerobic cell benefited by the extra energy available from aerobic respiration. The engulfed cell benefited by nutrients provided by its host. Evidence linking organelles to prokaryotes
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Examples of this type of symbiotic relationship can be found today. For example, some sponges harbor photosynthetic algae within their tissues. Sponges that are infected with algae have the ability to photosynthesize. The organelles (chloroplasts and mitochondria) resemble bacteria in size and structure. These organelles each contain a small amount of DNA ( prokaryote ) but lack a nuclear membrane . Each has the capability of self-replication. They reproduce by
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Protists reference great - Protists Eukaryotic Cells...

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