Transcript Slide 1 - Menihek Home Page

6 methods that are utilized to classify
organisms.
• Evidence from the Fossil Record
– Often Fossils can be found that illustrate a "Transition" from one
species to another. When such Transitions are made it suggests
commonalities between modern species. Archaeopteryx when it
was discovered suggested a link between birds and reptiles.
• Anatomical Evidence
– Organisms that are anatomically similar are likely to be related.
The presence of Homologous structures would suggest a reason
to group organisms together. The more similar species are to
one another the stronger the case for grouping them together.
• Embryological Similarity
– As with the Anatomical Similarities the more similar the
organisms are during the embryological stage the stronger the
case for grouping them together.
• Biochemical Similarity
– Again the more similar the Biochemical makeup of the
Species the stronger the case for grouping them
together
• DNA Evidence
– Once more a comparison of the DNA can be used to
classify organisms. The closer the DNA the closer the
relation and again the stronger the case for a similar
grouping.
Modern Developments
• The approach Linnaeus took to classifying species and
the majority of his taxonomic groupings remained the
standard in biology for at least two centuries.
• Since the 1960s, however, a trend called cladism or
cladistic taxonomy, has emerged and is expected to
usurp Linnaean classification.
• In classifying species, cladists place a priority in
achieving unity with the Darwinian principle of common
descent.
• In essence this method seeks to establish common
evolutionary patterns and group those that have a
common "ancestry" together.
• This establishment of Phylogentic Relationships can be
said to be the 6th means for classification.
Cladistics
In grouping species, cladists look for "procured similarities,"
meaning those aspects that species can be expected to
share by possessing a common ancestor. This approach
differs from that of phenetics, which does not address
ancestry and associates species based on overall
similarity.
• It also differs also from classification based on ad hoc
"key characters." Cladists avail themselves of all the
types of evidence available, including DNA sequences
and hybridization studies, biochemistry, and traditional
morphology.
• They often make use of computerized algorithms and
mathematical formulae to identify the most likely
phylogeny or "family tree" that relates the species they
are considering.
• The science of classification has grown as
knowledge and technology have grown.
One leading to the other. We now know far
more than Aristotle, Linnaeus, and other
great Biologists of the past could have
hoped to know. Projecting into the future
our descendents will view our knowledge
base as we view theirs. Good for their time
but insufficient for ours!
• As presented in the text Biologists by in large have
adopted a 6 Kingdom System of classification. The
reasons for this can be distilled into an examination of
the members of the former Kingdom Monera (under the
5 Kingdom System)
• Within that group it was realized that there are distinct
differences between those that are known as the Archae
Bacteria and the remaining members.
• For this reason the creation of a 6 Kingdom arrangement
was made.
• This takes into account the unique differences and
satisfies the deficiencies that the 5 Kingdom system
held.
Bacteria
Archaea
Bacteria
Archaea
Monera
Eukarya
Protista
Plantae
Fungi
Anamalia
Protista
Plantae
Fungi
Anamalia
Your Turn
• Read pgs. 122 - 126
• Page 127 Questions 2,3,4,5,6,7,8,9