Systematics refers to the study and classification of organisms for the determination of the evolutionary relationship of organisms. Therefore, the systematics consists of both taxonomy and evolution. Systematics uses morphological, behavioral, genetics, and evolutionary relationships between organisms.
By using these characteristic features, systematics describes an organism by means of classification, name, cladistics, and phylogenetics. Cladistics refers to the classification of organisms based on the branching of different lineages from a common ancestor.
Phylogenetics refers to the study of the history of evolution and the relationship among groups of organisms. Phenetics refers to the characteristics of organisms excluding the phylogenetics. The relationships of the organisms are presented by phylogenetic trees. Both phylogenetics and phenetics are described in figure 2. Figure 2: Phylogenetics and Phonetics.
Taxonomy is one of the components of systematics. Therefore, during the description of organisms by systematics, the binomial nomenclature is also used. Furthermore, systematics identifies biological enemies of organisms that act as a biological control. It is useful for separating flowering plants into groups when using phenetic methods. However, this may not be enough to qualify flower color as a useful systematic characteristic.
It is useful in systematics only if those flowers with the same color are similar because they are descended from an ancestor with that color flower. Thus, flower color is determined by ancestry by the way, flower color is sometimes useful and sometimes not to systemetists. Cladistics is a particular systematic scheme based on an explicit theory of evolution.
In cladistics. This is the basis for the focus on ancestry as linking organisms into groups. Thus, a group grows like a tree, with the ancestral group being the trunk. As you go from the base of the tree upward, you are traveling through time towards the present. The tips of the last splits the tiniest twigs on the tree represent the most recent clades, the only clades still in existence. The tree metaphor is a very good one.
In fact, the result of a cladistic analysis is a tree-like diagram called a dendrogram the root term "dendro" comes from the Greek dendron for tree. Cladistics is a set of methods to uncover the tree, which is all in the past by definition , using characteristics measured from the organisms alive today. Since the methods are standardized, the same data will produce the same groupings. There are a lot of different methodologies, but the problem of multiple methods is not as difficult for cladists as it is for pheneticists.
This is because systematics is a natural system, so the different methods are all uncovering the same natural groups. Thus, the assumption is that they should all produce the same results if the data and methods are free of error. To construct a cladogram, one must measure characteristics that indicate common ancestry.
Whale flippers, primate hands, and frog paws all have five fingers. The development of these organs supports the hypothesis that they are similar because the ancestor of these organisms had five fingers. You may recognize this similarity-due-to-descent as homology. Lets go back to flower color. Flowers in cool tropical uplands are more often red than expected.
Is this because the plants in this habitat are all related? In this case, probably not. Lots of very different plants occur in these areas. However, cool areas like these have fewer flying insects and many pollinators are not insects but vertebrates. Reds are apparently easier for vertebrates to see so the increased incidence of red flowers is probably related to the utility of having a flower that is easily seen.
In this habitat, red flower color does not necessarily indicate common ancestry. Deciding which characteristics contain information about ancestry can be tricky. This, and the large number of calculations needed to analyze data, limited cladistic analyses for many years. However, two technological advances have turned it into a preferred means of making natural classifications.
First, computers have made it possible to do the many trillions of calculations often needed to perform an analysis. Second, DNA sequencing technology has given researchers the means to measure characteristics gene sequences that are the very stuff of common descent. The details can get a bit tricky but, in general, the assumption that two individuals have the same gene sequence because they share a common ancestor is a reasonable one. How, you might ask, does all of this affect you in this class?
In articles, book and websites devoted to plant classification, you will see that it either uses a standard taxonomic or a cladistic classification. You have to recognize which is being used and to appreciate the reasons why the two schemes are not equivalents. If you go to the USDA site to classify your plants, you will get a standard taxonomic approach, where there are species, genera, families, etc. They are not the same. The USDA site is based on a taxonomic scheme that tries to fit plants into a preset hierarchy.
Those who have constructed this hierarchy many many researchers working over many many years have tried to use characteristics that reflect common ancestry so this is an attempt at a natural system but made groups according to a pre-ordained taxonomic structure.
This approach is called evolutionary systematics a bit of a redundancy. Thus, all plants in the family Fabaceae pea family are believed to share a common ancestor, i. The "Tree of Life" site presents a strictly cladistic analysis, in which the branching pattern arises from the data, not from a preset taxonomic hierarchy.
A cladogram is not the same as the standard taxonomic hierarchy and can be very different from it. Just try it for the plants. The USDA site presents the plants like an outline, in which each lower taxonomic level is indented from the next higher level.
Select "Class" as the rank and you will get a hierarchical classification of all plants to the level of the family. I have reproduced the results below. Kingdom Plantae -- Plants. If you go the the Tree of Life web page on embryophytes, the nearest you can to the level presented in the USDA above, you get the cladogram presented below.
Notice that there are some similar names with different suffixes, like Filicopsida below and above or Lycopodiopsida above and Lycopsida below. Notice that both are classes above, but what are they below?
It turns out that there is no equivalent to class or family, or order in the Tree of Life's cladistic approach. So, even though "Filicopsida" includes the same plants in both schemes, it fits into the overall scheme very differently in each approach to taxonomy. The conclusion to draw from this is that there are different taxonomic methods to serve different purposes.
The standard hierarchy is preferred as an organizational scheme - a good filing system. Using it, one can quickly find plants with particular characteristics.
The standardization of the hierarchy Kingdom, Division, etc. However, it is not a truly systematic approach. Attempts to make it more natural fail when the actual groups can't be easily fitted into the hierarchical scheme without making loads of new levels superfamilies, subclasses, sections, groups, etc. They do the naming of taxa in a hierarchical manner: Kingdom , Phylum, Class , Order, Family, Genus, Species , and other taxonomic levels.
Maintenance of collections of specimens is one of several responsibilities that a taxonomist would perform. Hence, taxonomy provides identification keys for studying new specimens. Moreover, the distribution of a certain species is very important for the survival of other organisms; hence taxonomy is directly involved with studying that aspect as well.
One of the well-known functions that taxonomists do is the naming of organisms according to binomial nomenclature: a generic and specific name. Sometimes, they also include sub-species names for clear identification. Taxonomists describe organisms, both extant and extinct species scientifically. Since the environment changes every moment, the species should adapt accordingly, and this phenomenon is taking place rapidly among insects; taxonomical aspects are very important to be updated for such groups of organisms as the descriptions for a particular species have been changed in a minor interval.
Accordingly, the naming would also be changed with the new description forming a new taxon. In fact, taxonomy is a fascinating field in biology with the involvement of highly enthusiastic scientists who are devoted to the discipline and usually go through many hardships in the wild.
Systematics or biological systematics is the broad field of biology that studies the diversification of species. Systematics considers both extant and extinct species and also considers the evolutionary relationships of species thoroughly.
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