Download Taxonomy is a branch of biology that names and groups organisms

Taxonomy is a branch of biology that names and groups organisms according to their
characteristics and evolutionary history.
Aristotle (384-322 B.C.) was the first to classify living organisms. This greek philospher
grouped animals into two categories. The particular organism was classified as either
plant or animal origin.
As time progressed, modern science and rapid research identified many new organisms.
Aristotle’s classification was not sufficient.
The Swedish naturalist Carolus Linnaeus (1707-1778) realized that such a system was not
conducive for modern biology. Linnaeus realized that common names caused a problem
as they varied from region to region. For example a jelly fish is not a fish, or a sea horse
is not a horse. Linnaeus developed a classification system of organizing organisms into
hierarchal categories. He did this be using the physical appearances of organisms to
group them.
Viruses are not in ANY of these kingdoms, scientists do not classify them as 'alive'
Linnaeus made two main contributions to taxonomy. He was instrumental in developing
hierarchal categories and binomial nomenclature.
Hierarchal classification includes seven different levels of organization. Kingdom,
Phyla, Classes, Orders, Families, Genera, and Species are included in the seven. A
mnemonic device used to remember this could be
Kings Play Calgary On Friday Gretzky Scores.
Kingdom
Phylum
Class
Order
Family
Genus
Species
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo
Sapiens
Humans
Animalia
Chordata
Mammalia
Carnivora
Felidae
Felis
Domesticus
House cat
We identify organisms by using their Genus name and their species name. These names
are either going to be in Greek or Latin. For example, humans would be known as Homo
Sapiens. This two-name system is known as binomial nomenclature. This system allows
scientists to have universal communication among different speaking countries.
For many years, most biologists favored a Five-Kingdom system consisting of Kingdoms
Monera, Protista, Fungi, Plantae, and Animalia. They were placed into categories by
their type of cell (prokaryotic or eukaryotic), level of organization (unicellular or
multicellular), and how they acquire their nutrition.
It is suggested that protests evolved from the Monerans who are the simplest organism.
Fungus, Plants and Animals evolved from the Protists in three separate evolutionary
lines. The five kingdom system of classification is based on structural differences and
also on modes of nutrition among the eukaryotes.
A New Proposal: The Three Domains of Life
In the 1970’s scientists began to find evidence for a previously unknown group of
prokaryotic organisms. These organisms lived in extreme environments such as the Dead
Sea, acid lakes, and salt evaporation ponds. These are environments that scientists never
suspected of maintaining any life.
Because they appeared prokaryotic, they were considered bacteria and named
"archaebacteria" ('ancient' bacteria). However, became obvious from biochemical
characteristics and DNA sequence analysis that there were numerous differences
between these archaebacteria and other bacteria. Before long, it was realized that these
archaebacteria were more closely related to the eukaryotes than to bacteria. Today, these
bacteria have been renamed Archaea.
From this work scientistspropesed that there should be a new caterogy of classification of
life - the Domain, a classification category above Kingdom.
The traditional 5 Kingdom system says nothing about how organisms within Kingdoms
or between kingdoms may be related to each other via evolutionary relationships among
the kingdoms.
A New Proposal is the Three Domains of Life. The three domains are Bacteria, Archaea,
and Eukarya. The three-domain system of classification is based on biochemical
differences that show they are three vastly different groups of organisms. See table 27.3
on page 561 titled Classification Criteria for the Three Domains.
How was the 'Three Domain' Classification of Life Determined?
Scientists used the nucleotide sequence of Ribosomal rRNA (the small subunit) and other
RNA and protein sequences as an “Evolutionary Chronometer” – an evolutionary time
clock.
What makes rRNA (or another sequence) a good ‘chronometer’?
1. It is universally distributed across group chosen – all organisms have
rRNA
2. It is functionaly similar between organisms – rRNAs all participate in
protein synthesis
3. Its sequence changes slowly - good for looking across long periods of
time
4. The rRNA sequences can be aligned, or matched up, between 2
organisms
1. What are the names of the 3 Domains? Who is Carl Woese and what was his role
developing the concept of 3 Domains?
2. What is rRNA and why was did scientists choose it as an Evolutionary Chronometer?
3. Bacteria: What is the significance of the Proteobacteria and the Cyanobacteria in the
development of eukaryotic organelles?
4. Archaea: Distinguish between the three groups. Why are thay called 'extremeophiles'?
5. Eukarya: Be able to list the 4 Kingdom within Eukarya and give 1 representative
organisms for each. (You do not need to know dates, numbers of species, or other facts
provided in the quotes).
Horse
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Species: Equus caballus
Amoeba proteus