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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