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Description
Flashcards by Taylor Caufield, updated more than 1 year ago
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Created by Taylor Caufield
almost 9 years ago
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| Question | Answer |
| 1.5.U1 Cells can only be formed by division of pre existing cells. | Cells are highly complex structures and a way to produce cells from simpler subunits has not been found. All known examples of growth are a result of cells division. Louis Pasteur designed an experiment that proved this. |
| 1.5.U2 The first cells must have arisen from non-living material. | It is argued that the first cell either derived from a single ancestor cell that was created through spontaneous generation, or the first cell was transported here from elsewhere in the universe. |
| Spontaneous Generation | The formation of life from non-living material. |
| 1.5.U3 The origin of eukaryotic cells can be explained by the endosymbiotic theory. | Mitochondria were once free living prokaryotic organisms that began to develop aerobic cell respiration. Larger prokaryotes that anaerobically respire took them in by endocytosis. Instead of killing the smaller prokaryotes, they allowed them to live in the cytoplasm. As long as the smaller prokaryotes grew and divided as fast as the larger ones, they could exist forever inside the larger cells. |
| 1.5.A1 Evidence from Pasteur's experiments that spontaneous generation of cells and organisms does not now occur on earth | Two experiments were set up. Pasteur added nutrient broth to flasks and bent the necks of the flasks into "S" shapes. Each flask was then heated to boil the broth in order to kill all existing microbes. After the broths have been sterilized, Pasteur opened up on of the flasks to expose it and left the other closed off. The broth in flask one that was opened turned cloudy and the broth in the flask that was closed stayed the same. This indicates that growth only happened in the exposed flask, which proves that spontaneous generation cannot occur. |
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