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Biology 110 - Basic Concepts and Biodiversity

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Prokaryotes I - Cellular and Genetic Organization

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In the last few decades, several taxonomic schemes have been used to describe life; you were introduced to this concept in Tutorial Two. One of the simplest divides life into prokaryotes and eukaryotes; that is, those organisms without nuclei went into one group and those with nuclei went into another, respectively. Another commonly used scheme divides life into five kingdoms: Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia. You may see one of these schemes in an older textbook or website. Keep in mind that classification schemes strive to show the evolutionary relationships between groups, and in recent years it has become apparent that the evolutionary relationships of prokaryotes are quite complex. One prokaryotic group, the Archaea, have some features that are more eukaryotic than prokaryotic. Although the Archaea lack a nucleus, their genetic organization is more like that of a eukaryote.

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Prokaryotes do not alternate between the haploid and diploid states, so meiosis and fertilization are not components of their life cycles. Rather, binary fission is the main method of reproduction in prokaryotes. This form of asexual reproduction means that the genetic variation created by meiosis and random fertilization (you will learn more about this in Tutorial #11) does not occur in prokaryotes. Nonetheless, genetic variation does occur in prokaryotes, and mutations are one source of variation in the population. Genetic variation within a population can be beneficial because it provides the raw materials for a population to adapt to a changing environment. Greater diversity in the gene pool increases the likelihood that at least some of the organisms in a population will have the right genetic combination to survive if environmental conditions change.

Three mechanisms by which prokaryotes transfer genes between individuals (transformation, conjugation, and transduction) will be discussed next.

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Questions?  Send your instructor a message through ANGELCanvas?

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