Number 4 please ndoplasnic reticulum f. cilia and flagella g. vacuole h. ribosom
ID: 202911 • Letter: N
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Number 4 please ndoplasnic reticulum f. cilia and flagella g. vacuole h. ribosome i. lysosome Cells lining the respiratory passages White blood cells that engulf and destroy invading bacteria Leaf cells of cacti 4, One organism found in a termite's gut is Mixotricha paradoxa. This strange creature looks like a single-celled swimming ciliate under low magnification. However, the electron microscope reveals that it con- tains spherical bacteria rather than mitochondria and has on its sur- face, rather than ciliía, hundreds of thousands of spirilla and bacilla bacteria. You are the scientist who first observed this organism. How would you describe this organism-single-celled? aggregate? colony? multicellular? Review definitions of these terms in the introduction to Exercise 3.5. Can the structure of this organism give you any insight into the evolution of eukaryotic cells? (Hint: See the discussion of the endosymbiosis hypothesis in your text.) 5. Pleodorina is an aquatic green algae that is common in ponds, lakes, roadside ditches (Figure 3.13). This organism is made up of 32 to 128 cells that are embedded in a gel-like matrix. In mature colonies two types of cells can be distinguished, small somatic cells and larger reproductive cells that divide to form new colonies. Somatic cells carry on photosyn- thesis, but may become reproductive if isolated from the colony Review the criteria used to determine multicellularity, and decide if Pleodorina should be classified as multicellular or colonialExplanation / Answer
4. Mixotricha paradoxa is a single celled eukaryotic motile protozoan that lacks mitochondria (they have only one cell). The spherical bacteria (spirilla) present inside its body serves the function of mitochondria. On its surface of this protist, three other symbionts live, which include Paramecium bursaria, Paulinella chromatophora. Paramecium burasaria forms a symbiotic relationship with green algae Zoochlorella that lives in the cytoplasm of the cell. Paulinella chromatophora has an endosymbiont cyanobacteria in it. Hence, there are five genomes in this protist.
Mixotricha paradoxa has an bacteria that lives in it. Hence, it is an example of endosymbiotic theory for origin of mitochondria. According to endosymbiosis theory, an anaerobic prokaryote that was unable to utilize oxygen lost its cell wall. The elastic membrane beneath the cell wall enfolded and led to formation of the nucleus and the internal organelles of the cell. The primitive eukaryotic cell could engulf an aerobic proteobacteria (a prokaryote) via its cell membrane. The primitive eukaryote did not degrade the aerobic proteobacteria. There was a mutually beneficial relationship initiated wherein the eukaryote provided protection and nutrition to the proteobacteria while the proteobacteria provided energy via respiration. Over time, most of the genes were transferred to the nucleus and the endosymbiont could not live outside the host. It became dependent on the host cell for organic and inorganic nutrient. The respiratory apparatus became evolved, gained a double membrane and became a mitochondrion. The host cell now evolved to form respiring eukaryotic aerobe. However, in case of Mixotricha paradoxa, the spirilla bacteria retained its genome and remained as a bacterium within the eukaryote. The protist existed initially as an anaerobic prokaryote. Its cell membrane enfolded and it formed organelles and nucleus. The spirilla bacteria are aerobic and can undergo cellular respiration. The protist engulfed the spirilla bacteria for a mutually symbiotic association via its cell membrane. The protist provided protection and nutrition to the spirochete while the bacteria provided energy via respiration. Over time, the bacteria lost its ability to live outside the protist.
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