Classifying Organisms and Domains of Life (B2)

Study Notes

Ecologists use a consistent method of classification to refer to various species and their relatives.
Taxonomy is the practice of classifying living things.
All living organisms can be classified according to three domains of life: Archaea, Bacteria, and Eukarya.

Archaea are prokaryotic, single-celled organisms that live in extreme environments, like hot springs and salt lakes. They can be autotrophs or heterotrophs.
Bacteria are prokaryotic, single-celled organisms that live in less extreme environments. They can be autotrophs or heterotrophs.
Eukarya are eukaryotic, meaning they have a nucleus. They can be single-celled or multicellular. They live in less extreme environments and can be autotrophs or heterotrophs.

Living things are classified into eight levels, from general to specific: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
This system (excluding Domain), was developed by Carolus Linnaeus.

Most organisms are classified according to binomial nomenclature, which combines their genus and species.
Scientific names are italicized, and use Latin and Greek words.

Binomial nomenclature indicates similarities in anatomy, embryology, and evolutionary ancestry.
It suggests different species are genetically related, for example: North American black bear (Ursus americanus), Grizzly bear (Ursus horribilus), Alaskan brown bear (Ursus arctos), and Polar bear (Ursus maritimus).

Modern technology allows scientists to sequence DNA, which can verify or change an organism's classification.
For instance, skunks were recently reclassified into their own family, separate from weasels.

Dichotomous keys use pairs of descriptions to simplify the identification of organisms.
They are often used to identify species within the same family, which can look very similar.