Lesson 2: Classification Flashcards
Systematics
Branch of Biology
that deals with
classifying living
things both current
and prehistoric.
Three Branches
of Systematics
Taxonomy:
Branch describing and naming new
taxonomic groups (species)
Classification
Branch organizing information about
organisms by arranging them into a
hierarchical system
Phylogenetics
Branch determining the evolutionary history and relationships among the various forms of life through time
History of
Classification
Aristotle (384 – 322 BCE)
Created the first widely used
system of classification by dividing
organisms into plants and animals.
Carolus Linnaeus (1707 – 1778)
Developed the hierarchical
categorization system.
Grouped organisms based on
resemblance to other life forms
Developed binomial nomenclature
Binomial
Nomenclature 1
Naming system developed by Swedish botanist
Carolus Linnaeus
Each organism has a two part name
First the genus then the species
Ex. Acer rubrum (red maple tree)
Acer is the genus name
rubrum is the species name
Notice: genus name is capitalized, species
is not.
Binomial
Nomenclature 2
1850 – 1900’s
Improvements in light
microscopy led to the discovery
of a large number of organisms
Ernst Haeckel proposed the
Kingdom Protista in 1866. This
includes all single celled
organisms.
In the early 1900’s the invention
of the electron microscope and
advancements in biochemistry
lead to the discovery of
Eukaryotic and Prokaryotic cells.
Binomial
Nomenclature 3
Robert Whitaker (1959)
Proposed 5 kingdom system (Plants,
Animals, Fungi, Bacteria and Protists)
Carl Woese (1970’s)
Analyzed base sequences of RNA in
bacteria and protists and suggested
that bacteria should be separated into
two groups, Eubacteria and
Archaebacteria.
Led to a 6 kingdom system in which
Kingdom Bacteria (Monera) was
separated into the Eubacteria and
Archaebacteria kingdoms.
1990 Woese proposed a Three
Domain scheme of classification.
Types of Classification
Historically, there have been two main classification schemes.
These are similar in that they use the characteristics of organisms to
classify, however, they differ in how those characteristics are
established.
Artificial Classification – characteristics used for classification are chosen
arbitrarily, then organisms are grouped accordingly.
Natural Classification – organisms are grouped first according to similarities,
then shared characteristics are identified.
Advantages and Disadvantages
While artificial classification is easy to develop and can remain unchanged, it does not show evolutionary relationships.
Artificial Classification is rarely used today.
In natural classification all members of a group would share a common ancestor but this type of classification is highly changeable as new information is discovered.
Taxonomists will reclassify groups of species when new evidence arises that suggests a different relationship to the existing scheme.
This is the basis of the modern system of classification.
Phylogenetic Classification
This system of classification is based in genetics.
Organisms with more similar DNA or amino acid sequences are
expected to be more closely related.
This is the current method of classification of organisms today
Current Taxonomic
Model
The classification system
used today to organize
life on earth
Species
A species is a population which
can interbreed with each other
(share a gene pool) to produce
fertile offspring.
This makes them a distinct
biological unit.
Genus
A genus is a group of closely related
species.
All the species in a genus share
common characteristics.
Family
A family is a larger classification than
genus and groups similar genera
(plural for genus) together.
Order
The next largest classification
(taxon) groups similar families
together.
Class
Orders are grouped into
classes, again based on
common characteristics.
