Biology, Answering the Big Questions of Life/Taxonomy

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Classification of living things[edit]

In order to get a handle on the diversity of all living things, we give organisms names. Names like cat, squirrel, tree, mushroom and jellyfish.

These names used in everyday speech to describe an organism are called COMMON NAMES .

We also group different kinds of living organisms into groups:

  • Domains
  • Kingdoms
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
    • subspecies

When we refer to individual organisms, we use only the last two terms GENUS and SPECIES

This way of referring to organisms using two names is called BINOMIAL NOMENCLATURE and it was proposed by the Swedish Biologist Carolus Linnaeus in the mid 1700s

In Science, we prefer to use SCIENTIFIC NAMES (those using binomial nomenclature) to COMMON NAMES because common names change from place to place, but Scientific names are the same all over the world.

SCIENTIFIC NAMES are written in Latin Since Latin is no longer spoken as a living language, it does not change.

For example you and I call ourselves HUMANS

Human is the common name for the organisms that we are. Our scientific name is HOMO SAPIENS

Our entire classification is

  • Domain EUKARYA
  • Kingdom ANIMALIA
  • Superphylum DEUTEROSTOMIA
  • Phylum CORDATA
  • subphylum VERTEBRATA
  • Class MAMMALIA
  • subclass PLACENTALIA
  • Order PRIMATES
  • suborder HAPLORRHINI (dry nosed or simple nosed as opposed to wet/curved nose)
  • Family HOMINIDAE
  • subfamily HOMININAE
  • Genus HOMO
  • Species SAPIENS
  • Subspecies SAPIENS
  • Classification changes as new discoveries are made , just as theories change.


When Linnaeus wrote down the first widely accepted system, there were two kingdoms Animalia and plantae

Due to advances in genomics, we have been able to compare the genetic sequences of organisms and have come up with new classifications largely due to the work of Carl Woese whose RNA comparison studies suggested that a new group ARCHAEA be separated from both Eukaryotes and prokaryotes.

The current preferred system is the 6 kingdom system.


ARCHAEA Single celled, non nucleated organisms with radically different genetic sequences. Most are extremophiles that grow in harsh places. An example are Halophites. Single celled organisms that grow in salty areas like the great salt lake where salt content is 15 - 20%.

BACTERIA Single celled, non nucleated organisms. They are common all throughout the Earth. An example is Escherichia coli an intestinal bacteria.

PROTISTA Single celled organisms that may be found in organized groups. These organism have a nucleus and internal organelles. An example of a protist is an Amoeba.

FUNGI Single or multicellular organism that eat by secreting digestive chemicals and absorbing nutrients. An example of a Fungus is a shitake mushroom.

PLANTAE Multicellular organisms that use light to create energy and sugar by a process called photosynthesis. An example of a plant is a dandilion.

ANIMALIA Multicelluar organisms that eat food internally. An example of an animal is a grasshopper.