Chapter 2 THE TREE OF LIFE:
CLASSIFICATION AND PHYLOGENY
We have grouped organisms for easier study by comparing similarities and differences.
SYSTEMATICS: the study of the diversity of organisms and their comparative and evolutionary
relationships. It includes comparative anatomy, comparative biochemistry, comparative
physiology, etc.
CLASSIFICATION OR TAXONOMY is the ordering of organisms into groups. It includes the
principles procedures used in classification.
PHYLOGENY: refers to the evolutionary history of a species or group of species in terms of
their derivations through evolutionary processes; which species share a common ancestor, which
species share a more distant ancestor, etc.
Systematics is the study of biological diversity and evolutionary history of organisms.
Systematics includes...
Taxonomy, the science of identifying and classifying organisms.
Phylogenetics, the study of the evolutionary history of organisms.
Nomenclature, the system used in naming organisms.
CLASSIFICATION
The present system of nomenclature was devised by Carolus Linnaeus (Carl von Linne), a
Swedish botanist who live in the 18th. Century.
Linnaeus published in 1753 a book called Species Plantarum, "the kinds of plants".
Binomial system of nomenclature: Genus + species epithet = scientific name of the plant.
Hierarchical classification: groups within groups.
A taxonomic grouping is called a taxon.
Taxonomy is hierarchical: taxa are grouped into broader taxa.
Species are grouped into genera (sing. Genus).
Genera into families; families into orders; orders into classes; classes into divisions;
divisions into kingdoms.
There are intermediate taxonomic categories, e.g. superfamily or subspecies.
Since Darwin, most systems of classification attempt to reflect phylogenetic relationships.
It is difficult to find an unbroken line of ancestors that connect the different groups in questions.
Natural processes often destroy fossil evidence.
