Identifying, Naming & Classifying Species
➔ About 9 million species are identified however new species are discovered daily
What is a Species?
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Species: a group of organisms that can interbreed in nature and produce fertile offspring
○ Example: a frog and toad have many similar features but are considered different species
since they do not produce fertile, viable offspring together
Sometimes different species can produce offspring, but they are infertile (cannot breed) so they
are not considered a new species
○ Example: if a horse and donkey mate, they produce a mule – mules are sterile and cannot
breed with each other so they are not considered a species
■ Female horse + Male donkey = Mule
■ Male lion + Female tiger = Liger
Species Concepts
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Species are identified according to 3 different species concepts (there cannot be only 1 way to
identify a species)
1. Biological – whether 2 organisms mate under natural circumstances to produce fertile
offspring
2. Morphological – compares physical characteristics like body shape, size, structure
3. Phylogenetic – uses evolutionary history often based on DNA analysis
Naming Species
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Taxonomy: the branch of biology that identifies, names, and classifies species
Swedish botanist, Carl Linnaeus is the founder of taxonomy
He developed the system we use to name species – binomial nomenclature (categorizes the
natural world based on shared characteristics)
Binomial Nomenclature
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Each species is given a two-word Latin name – the two parts of the name are:
1. Genus name: identifies the group of closely related species to which the species belongs
(always capitalized)
2. Species name: refers to one type of organism (always lowercase)
○ Example: scientific name for humans = Homo sapiens
■ Scientific name is always italicized if typed or underlined if handwritten
Taxonomy
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Taxonomic categories are used to classify organisms
The categories or groupings are arranged in a hierarchy, from broadest to most specific
Hierarchical Classification
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Each level or category in a classification scheme is known as the rank – there are 8 ranks
The first rank, domain, is the most general – it has the most species
The species rank is specific to only one species
The 8 ranks are:
○ Domain
○ Kingdom
○ Phylum
○ Class
○ Order
○ Family
○ Genus
○ Species
■ Mnemonic: Did King Phillip Come Over From Germany Swimming?
Within each rank is a specific group called a taxon (plural form is taxa) which each organism can
be classified into
○ For example:
Rank
Taxa
Example
Domain
Bacteria, Archaea, Eukarya
Humans are in the “eukarya” taxon
Kingdom
Plants, Animals, Fungi, Protists,
Bacteria, Archaea
Humans are in the “animal” taxon
Higher ranks such as kingdom and domain are more general… there are less taxons, with more
members in each taxon
Lower ranks such as family and genus are more specific… more taxons with fewer members in
each taxon