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EXAM 5 - EXAM 5 Two basic approaches to science Discovery...

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EXAM 5 Two basic approaches to science Discovery science – mostly foucuses on describing nature Hypothesis-based science- mostly focuses on explaining nature o Discovery science Careful observation of nature Data may be qualitative or quantitative May focus on current phenomena(recording animal behavior) or may focus on historical events ( sequence of fossils occurring in rock strata) o Hypothesis An hypothesis (a tentative explanation) is tested- often, though not always, by performing experiments Data may be qualitative or quantitative Results either support(but never prove) or refute the hypothesis Also requires careful observation o Both approaches are science and can contribute in important ways to our understanding of the natural world o Neither can be used to test or understand any claims about putative supernatural phenomena or interventions Prokarotic and Eukaryotic cells Both types of cells undergo cell division We’re going to focus on cell division in eukaryotic cells In eukaryotic cells, cell division involves both division of the nucleus and division of the nucleus and division of cytoplasm Cells Cells are surrounded by a membrane called plasma membrane Some cells also have a cell wall- distinct from, and made of different materials than, the plasma membrane The nucleus is surrounded by two membranes (an envelope) and contains chromosomes with most of the DNA in the cell Two types of nuclear division (karyokinesis) o Mitosis o Meiosis Cell division also includes cytokinesis-division of the cytoplasm o Mitosis is the process that is required for multi and single celled things to make copies of eachother Chromosomes Consist of DNA and proteins Different species can have different numbers of chromosomes-humans have 46 Male ants of the species myrmecia pilosula have 1 The fern ophioglossum reticulatum has 1260 Genetic information is contained in the sequence of the DNA Each chromosome has one long DNA molecule with thousands of genes Chromosome shape and structure vary during the cell cycle
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Highly extended during interphase (chromatin) highly condensed during karyokinesis (chromosomes) Depending on the stage of the cell cycle, a chromosome can consist of one chromatid or two chromatidds Process of mitosis in an animal cell Fig 12.6 Mio Meiosis
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