Post under development.
Post under development.
Have you seen a flower like this red sub-tropical one? Do you know what it is? How could you find out?
Maybe you have a friend or relative that can tell you what it is. Maybe you can look in a field guide. Maybe you can use a taxonomic key. Maybe you can use genetic testing or biotechnology.
Scientists today use biotechnological methods to show
"pictures of relationships" among organisms. This way of studying organisms genetically and grouping them is a field called
cladistics. That may be a new word for many people, because the word itself is relatively new. So using a dictionary to find the meaning can help improve our understanding. It is important to teach students that they do not have to know all the words. Do you know all words? Do doctors and professors?
No one actually knows all words, so, it is important students recognize that and that they realize it is good to learn words that are new to them by using processes like context clues (In this case, we can guess from the context that, "cladistics," has something to do with relationships of organisms) or by looking up words in dictionaries and encyclopedias (and that there are specialized dictionaries and encyclopedias for different fields). It is
Joan Beinetti's quote that I like to emphasize to students so they can feel good about themselves, even though they do not know all the words, "No one knows all the words." (Personal communication, 1989).
Being comfortable not knowing is very important to good science. It allows scientists to enjoy finding new information out through experimentation. It is also important to read about what other scientists have done and learn about new words through their work and through tools like dictionaries, whether on-line, electronic, or book formats. So, what is, "cladistics?" Let's have a look.
In Wikipedia (where many students start to look, we find "
Cladistics (Ancient Greek: κλάδος, klados, "branch") is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants (and nothing else). ... In the terms of biological systematics, a clade is a single "branch" on the "tree of life", a monophyletic group," (Source: http://en.wikipedia.org/wiki/Cladistics, Accessed March 31, 2011). Did that help? It may have helped some but not others. There are more words that may be unfamiliar. There is no need to be nervous, however.
Let's read more. I found the following historical point interesting because the words the originator chose appear to me much easier to understand (and usually we use the originators words), "Cladistics
originated in the work of the German entomologist Willi Hennig, who referred to it as
'phylogenetic systematics' (also the name of his 1966 book); the
use of the terms "cladistics" and "clade" was popularized by other researchers. The technique and sometimes the name have been successfully applied in other disciplines: for example, to determine the relationships between the surviving manuscripts of the
Canterbury Tales [3, as cited in Wikipedia]," (Source: http://en.wikipedia.org/wiki/Cladistics, Accessed March 31, 2011). Let's get back to the flower and other methods for identifying it.
We've been discussing cladistics, now, we'll look at more traditional Linnaean nomenclature. Wait, look at those two words:
Do you see what I see? I emphasized parts of each word in red. When learning new vocabulary, it is helpful to look at word parts. Earlier we looked at the Greek background of the word, "cladistics." Remember?
κλάδος, klados, "branch." Hmmm! Students can think about the word parts as they learn new words. (
Scientific literacy involves learning new vocabulary and the related techniques.)
"Most taxonomists have used the traditional approaches of
Linnaean taxonomy and later
Evolutionary taxonomy to organize life forms. These approaches use several fixed levels of a hierarchy, such as
kingdom,
phylum,
class,
order, and
family. Phylogenetic nomenclature does not feature those terms, because the evolutionary tree is so deep and so complex that it is inadvisable to set a fixed number of levels," (Source: http://en.wikipedia.org/wiki/Cladistics; Accessed March 31,2011).
Linnaeus was famous for, among other things, binomial nomenclature... a two-name naming system. You know it...genus and specific epithet...genus and species names. These days, people recognize them with organisms familiar to most:
- Escherichia coli or E. coli
- Lactobacillus rhamnosis
- Clostridium difficile
These names are in Latin and follow the grammatical rule for words in foreign languages, that is they are underlined or italicized. There are two words to each name: The genus and the species names.
Taxonomic keys can be used to identify organisms to genus and species based on visible characteristics or other features of the organisms.
The technical literature discusses the difference between cladistics and Linneaen taxonomy. Here are a few examples. (Literacy notes: Remember that some students in any class will have lower, or higher reading levels than others. Some students like a challenge. College students should be capable of reading the journal articles, but, depending on the quality of the library education at their high schools, they may not yet have been exposed to journal articles. Thus, especially in undergraduate classes, it is a good idea to bridge the students up to "college level reading" of the refereed journal articles.)
- [PDF] Cladistic analysis or cladistic classification [PDF] from cornell.edu E Mayr - Z. zool. Syst. Evol.-forsch, 1974 - courses.cit.cornell.edu... In contrast to the flood of defenses of cladistics published in recent years (by Bigelow, Brundin ...proposes “that the phylogenetic system should be expressed by revision of the traditionalLinnaean system rather than by proposal of a separate classification.”
" Post;
Under development
(c)2011 J.S. Shipman
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