Classification and Taxonomy

• Taxonomy is a branch of biology concerned with the classification of living and extinct organisms.
• Taxonomy is the science of naming organisms and placing them into categories based on evolutionary relationships.
• The classification of an oak tree includes the kingdom Plantae, phylum Angiospermophyta, class Dicotyledonae, order Fagales, family Fagacae, genus Quercus, and species alba.
• Classification is the organisation of living entities into groups according to their characteristics.
• Classifying living organisms helps to know and understand more about them.
• We use a hierarchical system of classification.
• Aristotle classified 500 organisms into 11 categories.
• Carl von Linne (Carolus Linnaeus) proposed a modern classification system and grouped all organisms into 2 kingdoms -Plants (Plantae) and animals (Animalia).
• Carl von Linne introduced the scientific name composed of genus and species – Binomial Nomenclature.
• Ernst Haeckel proposed a third kingdom -The Protista in 1866.
• Charles Darwin proposed the concept of common ancestry.
• The Three Domain System is in use today and there is a debate amongst biologists about the number of kingdoms (and about taxonomy).
• Carl Woese studied the biochemistry of prokaryotic organisms in the late 1970s and focused on nucleotide sequences of the RNA found in the organism’s ribosomes.
• The Three Domain System includes the kingdoms Monera, The Archaea, and The Eukarya.
• A simple tree of all life is represented by a nested hierarchy where each level includes all other levels below it.
• The organisms included in any category of the taxonomic hierarchy form a Taxon (Taxa = plural).
• A few unicellular forms include yeasts, which range from small microscopic yeasts to large mushrooms and toadstools.
• Yeast cell walls are composed of chitin, a polysaccharide.
• Yeast nutrition is heterotrophic and they are decomposers.
• Most yeasts are saprophytes, but some are parasites.
• Kingdom Fungi is divided into moulds and yeasts.
• Moulds are decomposers and most are saprophytes.
• Edible mushrooms, fly agaric toadstool, and penicillium are examples of mushrooms.
• Animals range from simple sponges to worms to insects to man.
• Plants range from simple mosses to ferns to flowering plants to trees.
• Plants and animals are different in terms of nutrition, cell wall, movement, and species classification.
• The species and genus of an organism provide their specific and generic names.
• A species is the basic unit of classification, the lowest rank in Linnaean hierarchy, and a group of recognisably similar individuals clearly distinct from other groups.
• The binomial system of naming organisms involves every organism having two Latin names: the generic name (Genus) comes first and begins with a capital letter, and the specific name (species) comes last and begins with a lower class letter.
• Humans would be either Homo sapiens or Homo sapiens.
• Domestic dogs display considerable variation in appearance.
• In man, four races are recognised: australoid, mongoloid, caucasoid, negroid.
• The classification of a cat includes Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Carnivora, Family: Felidae, Genus: Felis, and Species: catus.
• Prokaryotes are microscopic simple cells and are Earth's first organisms.
• Most prokaryotes are unicellular, although some species form colonies.
• Prokaryotes are found in all environments, from the depths of the oceans to the highest mountains.
• Prokaryotes have a variety of shapes, including spheres (cocci), rods (bacilli), and spirals.
• Bacteria are rod-shaped bacilli.
• Spherical cocci are a type of bacteria.
• Spiral-shaped spirillia are a type of bacteria.