BSC 314 Lecture Notes - Lecture 39: Linnaean Taxonomy, Eukaryote, Archaea
27 Jun 2018
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Plants Among the Diversity of Organisms
Classification schemes are in a state of flux because of the availability of large volumes
of data generated by molecular sequencing of DNA and RNA. As might be expected,
disagreements among biologists are common. For example, not all biologists believe
widely different appearing and behaving organisms should be grouped together just ‐
because they have similar DNA base pair sequences. But, the cladists do (and are
willing to debate the doubters).
Major groups and current ways of grouping of organisms
In the middle of the eighteenth century, Linnaeus' ideas transformed biological
classification. In the latter half of the nineteenth century, Darwin revolutionized biology
with an irrefutable theory of evolution. At the end of the twentieth century, molecular
sequencing is changing the phylogeny of the entire tree of life. Appropriately enough, a
major adjustment has already been made at the roots of the tree: There appear to
be three main lines of development from the primitive milieu. The hodge podge of ‐
prokaryotes (unicellular, non nucleated organisms) clearly belong to two separate ‐
groups: the Bacteria and the Archaea (Archaebacteria). The nucleated organisms
(eukaryotes)— plants, animals, and so forth— fit in a separate lineage,
the Eukarya (Figure . The Linnaean hierarchy is modified and a new name added for
these three “super kingdoms,” the Domain.
Controversial as this change has been, shifts among groupings of the Eukarya are even more
controversial, not because the data are suspect, but because biologists differ on how best to organize the
new information with the old. Organisms in the five-kingdom approach of the recent past are now
distributed among four kingdoms of the Domain Eukarya and the two domains of prokaryotes, Domain
Bacteria and Domain Archaea.
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Document Summary
Classification schemes are in a state of flux because of the availability of large volumes of data generated by molecular sequencing of dna and rna. As might be expected, disagreements among biologists are common. For example, not all biologists believe widely different appearing and behaving organisms should be grouped together just because they have similar dna base pair sequences. But, the cladists do (and are willing to debate the doubters). Major groups and current ways of grouping of organisms. In the middle of the eighteenth century, linnaeus" ideas transformed biological classification. In the latter half of the nineteenth century, darwin revolutionized biology with an irrefutable theory of evolution. At the end of the twentieth century, molecular sequencing is changing the phylogeny of the entire tree of life. Appropriately enough, a major adjustment has already been made at the roots of the tree: there appear to be three main lines of development from the primitive milieu.
