Biomedical Engineering Reference
In-Depth Information
Chapter 3
The Tree of Life
“Individuals do not belong in the same taxon because they are similar, but they are
similar because they belong to the same taxon.”
George Gaylord Simpson (1902
1984) [13]
Bacteria (Chapters 1
14)
Eukaryota (Chapter 15)
Bikonta (2-flagellum)
Excavata (Chapters 16
18)
Archaeplastida (Chapter 24)
Chromalveolata (Chapters 19
21)
Unikonta (1-flagellum)
Amoebozoa (Chapter 22)
Opisthokonta
Choanozoa (Chapter 23)
Animalia (Chapters 25
32)
Fungi (Chapters 33
37)
Taxonomy is the science of classifying the elements of a knowledge domain,
and assigning names to the classes and the elements. In the case of terrestrial
life forms, taxonomy involves assigning a name and a class to every species
of life. Biologists estimate that there are about 50 million living or extinct
species, so the task of building a biological taxonomy is likely to continue
for as long as humans dwell on earth. Most biologists would agree to the
following:
1.
All living organisms on earth contain DNA, a highly stable nucleic acid.
DNA is transcribed into a less-stable, single-stranded molecule called
RNA, and RNA is translated into proteins. All living organisms replicate
their DNA and produce more organisms of the same genotype.
2.
All living organisms on earth can be divided into two broad classes:
the prokaryotes (organisms with a simple string of DNA and without a
membrane-delimited nucleus, or any other membrane-delimited organelles),
