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TRANSCRIPT
TaxonomyBio 11
Objectives
Explain how organisms are classified
Identify where different organisms should fall on the classification system
Classification
Why Classify?
To study the great diversity of organisms
biologists must give each one a name and
attempt to organize them into groups that
have meaning.
In the discipline known as Taxonomy, scientists
classify organisms and assign each a universally
accepted name.
Assigning Scientific Names
In the 18th century, scientists realized referring to
organisms by common names was confusing
Some organisms are known by many different names
depending on the language or even region
Ex. Cougar, puma, mountain lion, panther
Different organisms sometimes share a common name
Ex. In UK Buzzard = Hawk, in US Buzzard = Vulture.
Early Naming Efforts
First attempts described physical
characteristics in great detail.
Why was this a problem?
“Oak with deeply divided leaves that
have no hairs on their undersides and
no teeth around their edges”
Different scientists describe different
characteristics.
Binomial Nomenclature
In the 18th century, an botanist named
Carolus Linnaeus developed a two-word
naming system rooted in Latin.
Written in italics, fist words
CAPITALIZED, second word
lowercase.
First word = genus
Second word =species
For example: Humans belong to the
genus Homo and are of the species
sapien, the only surviving species in the
genus.
Linnaeus’s System of Classification
A hierarchical system including 7 levels. From
smallest to largest they are:
Species, genus, family, order, class, phylum, and
kingdom
Modern Evolutionary Classification
Interestingly, organisms choose their own species by who they mate with but
all other taxonomic groups were “invented” based on biological
characteristics.
Linnaeus’s system had limitations
For example: If you lived in the 18th century where would you put a dolphin?
What Characteristics are most important?
Crabs, barnacles, and limpets… let’s take a look
Evolutionary Classification
Instead of classification by physical attributes, organisms are grouped by their
evolutionary history.
Kingdoms and Domains
The scientific view was simpler in Linnaeus’s time.
Two Kingdoms: Animalia and Plantae
Then microorganisms were discovered and recognized as being significantly
different Protista.
Later, mushrooms, yeasts and molds were placed in their own kingdom Fungi.
Even later, scientists realized bacteria lacked certain cellular organelles that
other forms of life had and were given their own kingdom Monera.
This produced 5 Kingdoms: Monera, Protista, Fungi, Plantae, and Anamalia.
6 Kingdoms
In recent years, as technology and evidence increased, scientists realized that
Monera had two distinct groups that were as different as plants and animals
so it broke into two new kingdoms: Eubacteria and Archaebacteria.
This created 6 Kingdoms total.
The 3 Domain System
The most recent evolutionary trees were formed using a molecular
clock model that groups organisms according to how long they have
been evolving independently
3 Domains above Kingdom
Bacteria, Archaea, Eukarya
Domain Bacteria
Unicellular
Prokaryotic
Have thick and rigid cell walls that surround cell membrane
Contains a substance called peptidoglycan
Some need oxygen, some are killed by it.
Corresponds to kingdom Eubacteria
Domain Archaea
Also unicellular and prokaryotic
Cell walls lack peptidoglycan and contain unusual lipids not found in other
organisms
Found in extreme environments that lack oxygen
Corresponds with kingdom Archaebacteria
Domain Eukarya
Consists of all organisms that have a nucleus.
Broken into 4 Kingdoms
Protista
Fungi
Plantae
Anamalia
Dichotomous Keys
Dichotomous Keys are tools used for classification.
A series of paired statements that describe physical
characteristics.
Let’s try one!