A biologist thinks they have discovered a new species.
How can they be sure? There are three different species
concepts used to classify organisms in taxonomy.
1. Biological species concept – organisms can
successfully breed and produce fertile offspring. This
widely used concept only works for living, sexually
reproducing organisms.
2. Morphological species concept – comparing the
measurements and physical descriptions. Often used for
plants or asexually reproducing organisms.
3. Phylogenetic species concept – looks for evolutionary
relationships between organisms. Usually based on
DNA studies or fossil evidence.
Dichotomous means to divide in two. Scientists use a
dichotomous key and ask yes/no questions to classify a
newly discovered organism compared to existing organisms.
The questions biologists ask
in a dichotomous key are
based on known species
characteristics of organisms.
The choice of one alternative
yes or no answer determines
the next step in the
dichotomous key. For
example:
1. Does it have feathers? No
2. Does it have legs? Yes
Then it must be a lizard.
A dichotomous key can
be shown as a branching
tree diagram with
characteristics on each
branch. The questions
start with
1. Is it multicellular?
2. Does it have tissues?
3. Radial symmetry?
4. Bilateral symmetry?
These characteristics
classify animals.
Your newly discovered organism now needs a name.
Carolus Linnaeus developed the binomial naming system
so every species has a unique two part scientific name. The
rules are:
1. The scientific name consists of the genus and species.
2. Both words are italicized or underlined.
3. Genus is always capitalized.
4. species is always lower-case.
5. Both name are in Latin.
6. The species name must be unique in the same Genus.
For example, Ursus arctos or Homo sapiens
What is the honey bees’ scientific name? Apis mellifera
And the Large Milkweed bug?
Oncopeltus fasciatus
Common names of an
organism are different in
every language. Durian’s
scientific name is
Durio zibethinus
Look at p 395 in your text. Imagine how hard it must be for
someone learning English to understand the meaning of “fish” in
all those common names.