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An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. The first contact that an organism has with a particular antigen will result in the production of effector T and B cells which are activated cells that defend against the pathogen.
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Many scientists favor the RNA world hypothesis, in which RNA, not DNA, was the first genetic molecule of life on Earth. Other ideas include the pre-RNA world hypothesis and the metabolism-first hypothesis. Organic compounds could have been delivered to early Earth by meteorites and other celestial objects
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For unicellular organisms, cell division is important for the reproduction of the population, Unicellular organism mainly use cell division, also called binary fission, for pollution growth. This is because unicellular organisms are only composed of one cell.
Multicellular organisms use cell division for growth and reproduction. Cell division causes increase in the number of cells composing the organism hence its growth in size. Cell division is also used to create gametes that are used in reproduction by fertilization.
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Even in fully developed organisms, cell division is important in tissue repair. In tissue homeostasis, there is a balanced rate of cell division and cell death . An example in muscles. Due to the stress experienced by muscle cells, they usually have a lower life span and therefore the damaged cells are often replaced with new ones by cell division. This prevents tissue wastage.
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Growth factors signal the growth of a cell. They usually bind receptors on the cell surface and indicate how the cell should grow and divide base don environmental stimuli. An example is during regular exercises. Growth factors indicate that the muscle cells should divide regularly and grow bigger to accommodate the higher stress in the muscles from the workout. This is how your muscles grow bigger and stronger with more exercise.
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Differentiation of cells occurs through the silencing of some gene allowing the cell to produce particular proteins (and other biomolecules) that align with its functions in the body. This especially critical in multicellular organisms. An example is that while al the cells in your body have the same DNA, some cells differentiate into liver cells while others into lungs, stomach, heart, and etcetera.
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<span><span>C. descending order by weight. </span>The standard rule in food labeling guide is to list ingredients </span>in order of weight. The first ingredient being the one that weighs the most, and the last ingredient that weighs the least. Water should also be included in the list of ingredients unless it's less than 5 percent of the product.
