Classification

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					Classification
      All living things are classified and given a scientific name according to the system of Linnaeus (Carl
von Linné, 1707 - 1778). He was a Swedish botanist who introduced the idea of cataloguing and giving a
scientific name to all species. A scientific name is latinised and has two parts:
    specific name e.g. Homo
    generic name        e.g. sapiens
Such two part names are known as binomial nomenclature (introduced in 1735).

Once named, each organism is then grouped with similar organisms into the standard suprageneric
categories shown in the table below. The groups, from Kingdom down to species, become progressively
more and more closely related.
                      HUMAN                DOG             WOLF                TIGER
Kingdom               Animalia           Animalia         Animalia            Animalia
Phylum                Craniata            Craniata         Craniata           Craniata
Class                Mammalia           Mammalia          Mammalia           Mammalia
Order                 Primates          Carnivora         Carnivora          Carnivora
Family               Hominidae            Canidae          Canidae             Felidae
Genus                   Homo               Canis            Canis               Felis
Species                sapiens           familiaris         lupus               tigris

Background on Linnaeus
- Swedish born Carl von Linné, latinised his name to Carolus Linnaeus
- Described by a contempory as “The most compleat naturalist the world had ever seen”.
- Professor of Medicine and Botany Uppsala.
- Deeply patriotic and hoped classifying plants of Sweden would add to national wealth (tried to find a
   cheap Swedish alternative to China tea).
- Had rich patrons such as King and Queen of Sweden and Dutchman George Clifford the director of the
   East India Company, and was one of the first naturalists to send off naturalists on long sea voyages to
   collect specimens from abroad.
- Initially developed his classification system working with forgotten friend Peter Artedi (1705 – 1735), a
   naturalist who died aged 30. They started to develop their classification system as undergraduates at
   Uppsala, triggered by Artedi‟s efforts to classify the Umbelliferaceae (e.g. cow parsley, hemlock).
- Linnaeus classified all plants according to the number and appearance of their reproductive organs. He
   divided the flowering plants into classes based on their male parts, then orders according to their female
   parts.
- Linnaeus was a devout Christian with a gift for poetry and a somewhat „Swedish‟ view of plant life…
  “The actual petals of a flower contribute nothing to generation, serving only as the bridal bed which the
   great Creator has so gloriously prepared, adorned with such precious bed curtains, and perfumed with
   so many sweet scents in order that the bridegroom and bride may therein celebrate their nuptials with the
   greater solemnity. When the bed has thus been made ready, then is the time for the bridegroom to
   embrace his beloved wife and surrender himself to her…”
- A shocked Johann Siegesbeck from St. Petersburg wrote “Who would have thought that bluebells, lilies
   and onions could have been up to such immorality?” Linnaeus later named an unattractive weed
   Sigisbeckia.
- Species Plantarum published in 1753. Listed every plant he had ever encountered (7700 at time of
   Linnaeus‟ death). Systema Naturae published in 1758 was a comprehensive classification system for
   animals.
- Linnaeus based his system on a collaboration with Peter Artedi, who had been researching on fish
   classification. Soon afterwards Artedi sadly fell into a canal in Amsterdam and drowned, on his way
   home from a meal. Linnaeus was devastated and helped to posthumously publish Artedi‟s work The
   Natural History of Fishes in 1736. At the time Linnaeus paid tribute to the work of his friend, but over
   the years his name has been forgotten and Linnaeus stands alone as the father of classification.
- Although Artedi and Linnaeus introduced the concept of generic names, it was in fact Linnaeus‟s students
who started to use specific names, to speed up work in the field.
The Classification of Living Things
   It has rightly been said that life is hard to define, but all living things are made of cells and carry out 7
characteristic processes:
   M - movement
   R - respiration
   S - sensitivity
   G - growth
   R - reproduction
   E - excretion
   N - nutrition
You could think of „life‟ as DNA expressing itself.
There are 5 or 6 main types of life: plants
                                         animals
                                         fungi
                                         protoctista (+/- algae)
                                         bacteria and their relatives
                                         [viruses!]

1. Plants
- plants are multicellular eukaryotes with cell walls containing cellulose
- nutrition is autotrophic (photosynthesis)
- they have chloroplasts, which contain the photosynthetic pigments: chlorophyll a, chlorophyll b,
    xanthophyll and carotene
- there is a life cycle consisting of two alternating generations: a diploid sporophyte which produces
    spores, and a haploid gametophyte which produces gametes.
The Kingdom Plantae consists of 3 major groups:
    (i) Bryophytes             - liverworts (Hepaticae)
                               - mosses (Musci)
    (ii) Pteridophytes         - club mosses (Lycopodophyta) e.g. Selaginella
                               - horsetails (Sphenophyta) e.g. Equisetum
                               - cycads (Cycadopsida)
                               - ginkgos (Ginkgopsida)
                               - ferns (Filicinophyta)
    (iii) Spermatophytes       - conifers or gymnosperms (Coniferophyta)
                               - flowering plants (Angiospermophyta)         - monocots e.g. grass
                                                                             - dicots e.g. geranium

2. Animals
- animals are multicellular eukaryotes without cell walls
- they are heterotrophic (and holozoic i.e. ingestive)
- they contain nervous and muscle tissue

3. Fungi
- fungi are single celled or multicellular eukaryotes with cell walls made of chitin
- they lack chlorophyll (so can‟t photosynthesise), i.e. they are heterotrophic (and absorptive)
- nutrition is usually saprophytic (or „saprotrophic‟), although some species may also be mutualistic
    („symbiotic‟) or parasitic:
    Saprophytes rot things by externally digesting them, then absorbing the products e.g. the bread mould
    Rhizopus.
    Mutualism (symbiosis) means that two species live together for their mutual benefit e.g. lichens and
    mycorrhiza. Lichens are an association between a fungus (usually an ascomycete) and a green alga or
    cyanophyte (or sometimes both). The fungus gains food from the alga, and the alga gains a protected
    habitat. Examples are Verrucaria maura or tar lichen and Usnea florida or old man‟s beard.
   Mycorrhiza are an association between fungal hyphae of an underground mycelium and plant roots.
   This allows the fungus to take 15% to 20% of the plants carbohydrates, and the plant to take excess
   minerals (containing N and P) from the hyphae. About 90% of plant species form mycorrhizae, and
   some plants also gain protection against pathogenic fungi etc.
   In parasitic nutrition the fungus takes food directly from another organism and causes it harm e.g.
   Phytophthera infestans (potato blight fungus).

4. Protoctista
   Single celled eukaryotes and the algaemake up the Kingdom Protoctista. Eukaryote cells contain about
   1,000 times more DNA than bacterial cells, and have a true nucleus and membrane bound organelles
   such as mitochondria and Golgi bodies. Most Protoctista are still single celled, but some colonial and
   multicelled types have also evolved e.g. algae such as seaweeds. The Protoctista are an extremely
   diverse group, with some species being essentially plant-like, some more animal-like and some e.g.
   Euglena exhibiting characteristics of both. Over 60,000 species have been described, and some
   biologists who study them say there are over 40 different Protoctistan phyla. The Protoctista are the
   ancestors of the major multicellular groups of organisms: Fungi, Plants and Animals.

                  Amoeba




5. Monera
The earliest organisms were single-celled prokaryotes (Kingdom Monera), i.e. bacteria. This is an
  extremely diverse group of organisms which is still flourishing today. Bacteria are the smallest, most
  numerous and most widespread group of organisms on Earth, and for 2,000 million years they were the
  only organisms on Earth. Bacterial cells have no nucleus and no membrane-bound organelles, and most
  have a cell wall made of peptidoglycan (a mixture of sugar chains and polypeptides). Most bacteria are
  not disease-causing, and indeed without them acting as decomposers and nitrogen fixers plants and
  animals could not exist.

				
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posted:9/22/2011
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