Taxonomy & Classification Lecture - Grouping and Naming Organisms
A. Taxonomy as defined by Webster’s dictionary is:
a. the process or system of describing the way in which different living
things are related by putting them in groups
b. the study of the general principles of scientific classification
c. orderly classification of plants and animals according to their
presumed natural relationships
B. Taxonomy is used to help scientists to universally name and classify
organisms.
a. Why do we need to classify things?
i. We classify organisms so that we can understand how they
relate to one another. We organize them into groups that have
biological significance.
b. Why is Taxonomy so important?
i. So that everyone uses the same name and same naming
system for all organisms worldwide
C. Early naming efforts were very confusing and the names were extremely
long and detailed.
a. Early naming systems have been traced back
as far as 1500 B.C.E. from the early Egyptians
b. Early nomenclature (500 C.E. to 1700 C.E.)
example: “Oak with deeply divided leaves
that have no hairs on their undersides and no
teeth around their edges”
D. The Linnaeus system is the system that we use
today.
a. Created by Carolus Linnaeus in 1735
b. Linnaeus’s system is a binomial
nomenclature which is a two-word naming system
c. A taxon is a group or level of organization within a taxonomic
category
d. The Linnaeus system uses seven taxonomic categories:
i. Kingdom, phylum, class, order, family, Genus & species
E.
F.
G.
H.
ii. The scientific name is Genus species
Although we use the Linnaeus taxonomic
system, we have eight taxonomic categories,
and those categories could also have subcategories.
a. Domain, kingdom, phylum, class, order,
family, Genus, and species
i. example: Canis lupis
b. Sub-categories include sub-class and suborder
Traditional Classification
a. Problems
i. Based on body structure and physical similarities.
ii. Living things that are not related can share similar body
structures due to convergent evolution and related organisms
may have totally different body
structures.
1. Convergent evolution is the
appearance of apparently
similar structures in
organisms of different lines
of descent.
Evolutionary Classification
a. Scientists now group organisms into categories that represent lines
of evolutionary descent, not just physical similarities.
b. Cladistics is now the preferred analysis method which uses derived
characteristics to connect lineages. This method is used to construct
a cladogram
Role of DNA & RNA
a. With the advancement in DNA and RNA we have been able to follow
the genes of animals back through time.
b. A molecular clock allows us to use DNA to estimate the amount of
time that two organisms have been evolving independently, or how
long ago the two organisms separated on the evolutionary tree.
c. DNA advancement has also allowed us to ancestral relationships that
we didn’t know existed:
i. Example: yeast and humans both have a gene that codes for
myosin, which shows us that at one point we had a common
ancestor with yeast.