Taxonomy and Classification

Aristotle was the first to classify animal and plants into groups
1. Further classified animals based on their means of transportation (air, land, or water)
John Ray (1627–1705) - English naturalist
1. Published important works on plants, animals, and natural theology
2. Classified plants according to similarities and differences that emerged from observation – monocots and dicots.
Carolus Linnaeus (1707–1778) - Swedish Botanist
1. Grouped species according to shared physical characteristics (what you can see).
2. Method revised to improve consistency with the Darwinian principle of common descent.
3. Systema Naturae, ran through twelve editions during his lifetime (1st ed. 1735).
4. Nature was divided into three kingdoms: mineral (Mineralia), vegetable (Vegetabilia) and animal (Animalia).
5. Linnaeus used five ranks: class, order, genus, species, and variety.
6. Method still used to formulate the scientific name of every species.
7. Previously - long multi-worded names which gave a description of the species - were not fixed.
8. Philosophia Botanica (1751) Introduced new descriptive terms and defined their meaning with precision.
9. Late 1740s began to use a parallel system of naming species.
10. Nomen triviale (trivial name) was placed on the margin of the page next to the many-worded "scientific" name.
11. Had to be short, unique within a given genus, and that they should not be changed.
Kingdoms
1. Five-kingdom system - proposed in 1969, still used in many works, or forms the basis for newer multi-kingdom systems.
2. 1980s - emphasis on phylogeny and redefining the kingdoms to be monophyletic groups (groups made up of relatively closely related organisms).
3. The kingdom-level classification widely used for grouping organisms, although not perfect
4. Some problems – linking phylogeny of eukaryotic and kingdoms
5. Animalia Multicellular Obtain energy from ingesting food (Heterotrophic) Movement
  1. Plantae Multicellular Autotrophic – obtain energy through photsynthesis
    1. Fungi Multicellular Collect energy from organic matter Bodies consist of branching multinucleate filaments
      1. Protista Unicellular Live in water or in permanent moist habitats eg. algae Cells are larger and more complex than most bacteria Some obtain energy via photosynthesis ‘Algae’ Others acquire energy by ingesting food ‘Protozoa’
        Monera Unicellular Bacteria and Blue-green algae Prokaryotic cells
Linnaean Classification
1. Linnaean classification groups living organisms into a hierarchy, including the following basic ranks:
  1. Kingdom Phylum (plural - phyla) Class Order Family Genus Species
  2. May be over 40 various other ranks used for different species.
    1. For example, subphylum, superorder, subfamily, subtribe, or subspecies to handle complex groups such as insects. (Sub - below, super - above).
2. Genus and Species names make up the scientific name of a species. No species is ever listed without its genus. E.g. Homo sapiens – Man.
3. Mandatory suffixes for some of the ranks, for example: Superfamily – oidea Family – idae Subfamily – inae Tribe – ini
4. Binomial nomenclature - combination of a genus name and a single specific epithet (e.g. sapiens) to uniquely identify each species of organism.
5. Every species is given a unique and fixed name (compared with common names that may not be unique or consistent globally).
6. The names of the genera and species are always shown in italics or underlined if hand written. The genus begins with a capital letter, and the species without.
7. Example – Siberian Tiger Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora – Animals capable of consuming flesh. Family: Felidae – Carnivores with short skulls and well developed (normally retractible) claws. Genus: Panthera – Large cats with a specialised larynx with elastic ligaments, unlike other cats they can roar and purr. Species: tigris altaica– Striped coat in adults.
Phylogenetics
1. Treats a species as a group of lineage-connected individuals over time. A means of classifying groups of organisms according to degree of evolutionary relatedness.
2. Picture is of a cladogram a form of classification
3. Monophyly- all have common ancestor no matter where they branched off. Paraphyly- evolving at the same time, parallel evolution Polyphyly- link together, but not evolving at the same time, similar connection between groups Only mammals and birds are endothermic that is why they are linked Mammals and birds are convergent
4. Birds and reptiles - believed to be descended from a single common ancestor, so this taxonomic grouping is called monophyletic.
  1. "Modern reptile" is a grouping that shares a common ancestor, but as birds are excluded it is paraphyletic.
  2. A grouping such as ‘endothermic animals’ would include only mammals and birds – this is polyphyletic because the members of this grouping do not share the most recent common ancestor.
Cladistics
1. Derived from the ancient Greek ‘klados’ meaning "branch.“
2. German entomologist Will Hennig, who referred to it as phylogenetic systematics.
3. Organisms that share common ancestors (and therefore have similar features) are grouped into taxonomic groups called clades.
4. Clades can be represented in terms of a cladogram - branching diagram that depicts species divergence from common ancestors. They show the distribution and origins of hypothesized shared characteristics.
5. Cladistics is based on three principles: Groups of organisms are descended from a common ancestor. At each node (divergence of a population), there are two branching lines of descendants. Evolution results in modifications of characteristics over time.

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