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Lecture 4

BIOLOGY 1M03 Lecture Notes - Lecture 4: Phylogenetic Tree, Ribosomal Rna, Design Of ExperimentsPremium


Department
Biology
Course Code
BIOLOGY 1M03
Professor
Jon Stone
Lecture
4

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BIOLOGY 1M03 - Lecture 4 - The Tree of Life (Continued)
Using Molecules to Understand the Tree of Life:
Carl Woese and colleagues studied a small subunit known as rRNA, as a means
for understanding the evolutionary relationships among organisms.
For example, SSU rRNA (small subunit rRNA) is a nucleic acid that
constitutes partially ribosomes (the protein producing organelles in cells).
They discovered that rRNA sequences should be very similar in closely
related organisms, but less similar in organisms that are less closely
related; species in the same evolutionary lineage should share particular
changes in rRNA.
It can be concluded that a phylogenetic tree is a diagram that may
be interpreted as depicting these relationships among species.
Taxa (plural for taxon, a group of any rank, such as a species,
family, or class) that may be inferred to have shared an immediate
common ancestor are closely related; other taxa are more
distantly related.
The Branches of the Tree of Life:
Carl Woese proposed a new taxonomic category called the domain to represent
the major groups.
Woese proposed three major groups of organisms: two groups are
prokaryotic (bacteria and archaea) and one is eukaryotic (eukarya).
The location of some branches on the tree is hotly debated and the shape
of the tree will continue to change as databases expand.
Doing Biology:
Biologists test ideas about the way the natural world works by testing the
predictions made by possibly multiple precisely and concisely formulated
hypotheses.
Good scientific hypotheses make testable predictions - predictions that can be
rejected (for instance, falsified) by collecting and analysing data obtained in
carefully designed experiments.
Effective experimental designs allow researchers to test effects from single, well-
defined factors on phenomena and also:
Comprise control groups
Involve constant or equivalent conditions among groups (except for the
treatments to be tested)
Include repeating the experiment
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