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Published on : Jul 30, 2023 | Views : 2004 | Downloads : 1

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Slide 1-

Diversity of Life Major groupings How many organisms on earth Viruses
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Diversity of Life - Kingdoms Aristotle to Linneus 1860 – Animalia, Plantae Chlorophyll vs none = method of getting energy
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1850 Haeckel – add Protista (one celled) (1632-1723) the first person to study protozoa and bacteria Antonie van Leeuwenhoek Discovered Volvox in 1700 Separate them as both plants and animals and some in between (Euglena – a motile one celled organism with chlorophyll
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1937 Charlton – procaryotes,(bacteria) eucaryotes(true cells, with nucleus) Eucaryotes include animals, plants and protista (or proctista) Bacteria – ‘nothing’ inside Amoeba; nuclei, organelles, etc. Procaryote Eucaryote
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1959 – Whittaker – Fungi are fifth kingdom No chlorophyll, not motile, multicellular, eucaryotic
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1990 – Woese, splits procaryota into true bacteria = eubacteria, and archaebacteria (6th kingdom) also new category = Domains, archaea,bacteria and eukarya. Separation based on biochemistry, not appearance.
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Viruses: not classified – are they fragments of higher organisms, or remnants of very early life?? More later. What belongs in the kingdom plantae? Original:If it is photysynthetic it is a plant. Today; But if it is a procaryote, and green, it is not a plant (photsynthetic bacteria) If it is one celled eucaryote (euglena), it is not a plant. If it has no embryo, it is not a plant (so all marine and fresh water algae are no longer plants.) Why = cladistics in part. Attempt to find a common ancestor and recognition that photosynthesis is very old and may have arisen more than once.
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Euglena – a protist ‘seaweed’ – protist Photosynthetic bacteria = eu or archebacteria Note: multicellular algae are now protists !!!
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How many species are there on earth? Described species: 1.6 million. Most species are arthropods. About 1 million are insects. How many species are undescribed ?.
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How do we estimate the number of undescribed species? http://news.nationalgeographic.com/news/2002/06/0625_020624_0624TVprimate.html Two previously unknown monkey species, discovered in the Amazon in 2002 Discovery rate for birds, mammals; 1-3 per year – big, lots of researchers. Discovery rate for insects: higher and fewer researchers.
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Is the world full? Are all niches utilized?? Oceans land invasion Air invasion Fossil record: Poorer farther back you go – Major fluctuations
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Most unidentified species are small insects.
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Another strategy: species accumulation curves
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How many species are undescribed? The great killing experiment
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Find an tropical forest area about to be logged gas a tree and catch all the bugs sort the beetles to species do this for several tree species identify beetles unique to each tree. You know ½ of all animals are insects, ¼ of all insects are beetles you know how many different trees in the tropics Tree species x unique beetles x ½ x ¼ x 1.5 million (number of described species) = 10 to 20 million species undescribed
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This is the basis for the statement that 100s of species go extinct every day; they are tropical insects and it is due to tropical deforestation.
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A whole world underground that is mostly unexplored...
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Viruses
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Tiny (23 billion needed to become visible) Many shapes Consist of an outer capsule (protein) and an inner dna or rna molecule. Obligate parasites = use a host cell’s machinery to make copies of selves.
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Adenovirus (pink eye) Flu virus hiv virus Hanta virus Influenza virus Papilloma virus (warts)
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A submicroscopic infectious agent that is unable to grow or reproduce outside a host cell. It is non-cellular but consisting of a core of DNA or RNA surrounded by a protein coat.
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Viruses: extremely small, varied in shape.
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Origins Virus are extremely varied, some with as few as 4 genes, some with as many as 200. Believed to have several origins, not a single one. Thought to be ‘fragments’ from living cells and go back to first bacteria.
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Extreme abundance of viruses. One teaspoon of ocean water contains 10 to 100 million virus particles, ten times the number of bacteria.
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The ancient Virus World and evolution of cells Eugene V Koonin1 , Tatiana G Senkevich2 and Valerian V Dolja3 1 National Center for Biotechnology Information, National Library of Medicine, USA 2 Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20894, USA 3 Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331, USA What are viruses? “old view” = obligate parasites on cells, therefore, must have come into existence after cellular life. They are ‘deccomposition fragments’ of living cells. New view = see evolution of viruses or viruses and evolution
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The extraordinary diversity of viruses Viruses are ubiquitous companions of cellular life forms: it appears that every cellular organism studied has its own viruses or, at least, virus-like selfish genetic elements. Recent environmental studies have shown that viruses, primarily, bacteriophages, are "most abundant biological entities on the planet", with the total number of virus particles exceeding the number of cells by at least an order of magnitude. Viruses actively move between biomes and are thought to be major agents of evolution by virtue of their capacity to operate as vehicles of horizontal gene transfer (HGT).
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“Each teaspoon of weawater contains 10 – 100 million viruses (also 1-1-million bacteria. Effect on marine ecosystems? Marine bacterioplankton = total weight of all other ocean organisms and do most of the oceans photosynthesis 20% a day destroyed by viral infection – carbon not eaten but released.
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We outline a scenario of the origin of the main classes of viruses in conjunction with a specific model of precellular evolution under which the primordial gene pool dwelled in a network of inorganic compartments. Somewhat paradoxically, under this scenario, we surmise that selfish genetic elements ancestral to viruses evolved prior to typical cells, to become intracellular parasites once bacteria and archaea arrived at the scene. Selection against excessively aggressive parasites that would kill off the host ensembles of genetic elements would lead to early evolution of temperate virus-like agents and primitive defense mechanisms, possibly, based on the RNA interference principle. The emergence of the eukaryotic cell is construed as the second melting pot of virus evolution from which the major groups of eukaryotic viruses originated as a result of extensive recombination of genes from various bacteriophages, archaeal viruses, plasmids, and the evolving eukaryotic genomes. Again, this vision is predicated on a specific model of the emergence of eukaryotic cell under which archaeo-bacterial symbiosis was the starting point of eukaryogenesis, a scenario that appears to be best compatible with the data.
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Evolution of the virus world: origin of the main lineages from the primordial gene pool. Characteristic images of RNA and protein structures are shown for each postulated stage of evolution, and characteristic virion images are shown for the emerging classes of viruses. Thin arrows show the postulated movement of genetic pools between inorganic compartments. Block arrows show the origin of different classes of viruses at different stages of pre-cellular evolution. Koonin et al. Biology Direct 2006 1:29 doi:10.1186/1745-6150-1-29