2. a taxon bears only one correct name
3. no two species or genera (within one code) may have the same name
4. name must be latin or latinized
5. correct name is based upon publication priority (whoever described something first gets to give it the name, and if two species are discovered to have the same name, the first one gets to keep it, and the later one has to be changed.)
6. For plant families and animal superfamilies, the name of the family or superfamily must be based on that of a type genus.
Type genus: the first genus ever described in a given
family (plants) or superfamily (animals)
Example: old name of the Pea Family was Leguminosae.
New name: Fabaceae (because the very first genus
of leguminous plants ever described was given the name Faba
by Linnaeus.)
Another example: The old name of the Daisy Family was Compositae.
New name: Asteraceae (first genus described was Aster)
Classification is more than just naming things. Classifications have a function.
Biosystematics alone among the sciences tends to stress diversity, rather than commonality among organisms. It is a far less REDUCTIONIST field than others in the sciences.
Let's look at an example...
Another example:
They are also
ALLELOPATHIC--producing toxic compounds that are meant to deter growth of
other competing plants nearby.
(As we already know, this can be valuable to humans seeking
bioactive compounds--but don't assume that a product labeled "natural" is
safe. Those plants mean business.)
Example we'll use: Family Pongidae, the Great Apes.
To determine the symplesiomorphies that link this group together, we use an OUTGROUP, the next most recent relative of the entire assemblage above. In this case, an appropriate outgroup would be the Old World Monkeys.
The more symplesiomorphies a taxon within your study group shares with the outgroup, the more likely it is that it has a recency of common descent with that outgroup, and may be more primitive with respect to the other members of the assemblage.
Only SYNAPOMORPHIES can be used to establish recency of common descent among related organisms sharing many plesiomorphies.
SYMPLESIOMORPHIES help us establish that a study group shares characters with a hypothetical ancestor, but only the SYNAPOMORPHIES exhibited by each group tell us about how closely related they are to each other.
The more synapomorphies two groups exhibit, the more recent their common ancestor. For example, from the phylogenetic tree of the Great Apes we drew in class, you can surmise that humans and Bonobos exhibit more synapomorphies (shared, derived characters) than do humans and chimpanzees. And similarly, that Gorillas, chimps, Bonobos and humans exhibit more synapomorphies (as a group) than do Gibbons and humans.
A taxon's evolutionary history/relationships can be diagrammed with a phylogenetic tree, similar to the one you constructed in your BIOSYSTEMATICS WORKSHOP.
Form taxon: a taxon whose members are included in the group more on the basis of shared, known similarities in morphology, physiology, etc. than on known evolutionary relationships. (e.g., Kingdom Protista, Kingdom Monera, Division (Phylum) Deuteromycota)
(Be sure to review this in your Lab Manual)
However, within birds, feathers are a symplesiomorphy
which offer no further useful information in grouping birds
together into most common ancestry taxa.
Four tenets of cladism:
1. cladogenesis (speciation) is the only quantifiable feature of evolution.
2. all taxa must be monophyletic
3. all evolutionary relationships must be measured in terms of recency of common descent.
4. the rank of a taxon is automatically determined by the age of the common ancestor.
Classes, by the Cambrian and Devonian
Orders by the Carboniferous and Permian
Families by the Triassic & Early Cretaceous
Tribes by the Late Cretaceous and Oligocene
Genera by the Miocene
To the Cladist:
And now that we've covered all that, let's revisit that BIOSYSTEMATICS WORKSHOP.