This section is designed to help those unfamiliar with some of the biology and paleontology terms and explanations on this site. It is organized as a very basic overview of some of the terms and processes discussed. Some of it may seem pretty self explanatory, but I thought I'd make this section in case there were some ideas on this site that some may not understand. Key words are in red type.
What is taxonomy?
Taxonomy is a term that describes the science of classifying organisms, both living and extinct.
How does taxonomy work?
Organisms are usually named according to genetic similarity, physical similarity, and evolutionary history.
Taxonomic hierarchy
Each of the individual animals on this site have a genus and species name , such as Panthera leo, beneath their common name. These are the two lowest levels of the classification system. In it's most basic form, the system actually has seven levels. For example, the full classification of an African lion would be as follows:
| LEVEL | CLASSIFICATION |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Carnivora |
| Family | Felidae |
| Genus | Panthera |
| Species | leo |
How is a species identified?
The species level is usually the lowest level, and is most commonly defined as those organisms capable of breeding and producing viable offspring. For example: Tigers and lions are similar enough to be in the same genus. They have even been bred to produce offspring (called a 'liger' or 'tion') Although ligers and tions are usually healthy and able to function normally, they are sterile. The only way to produce one is with a lion or tiger, ligers and tions cannot have cubs. Therefore, because the offspring are sterile lions and tigers are in separate species.
Why do some animals seem to have a second species?
Some animals, like the Asiatic lion, have a name with three parts such as Panthera leo persica. The third part of this name is the subspecies name. Like I mentioned earlier, the seven level form of classification is the most basic. Some taxonomists add more levels such as subspecies, for those animals they feel are similar enough to belong to one species, but different enough to have their own category. Note: not all taxonomists agree with or even recognize these other levels of classifications, especially when dealing with fossil organisms (See Paleontology section)
Rules of Taxonomy
There are certain rules for naming of organisms . These are decided on and reviewed by the Linnean Society. This is the official society of taxonomists. Besides producing publications for and conducting research in the science of taxonomy. the society also decides which names will be recognized as the official classification of an organism. Some of the rules set for the classification of organisms are briefly summarized below:
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First and most obvious, proposed names are presented before the Linnean Society for approval before they are accepted, recognized, and widely used for scientific classification and research. |
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Names are written in a particular form. That's why the appear as they do on this site. The genus and species must be in italics when typed and underlined when written. The genus is always capitalized and the species is always in lower case , appearing like this: Panthera tigris. Genus must always be indicated in some form, the species is never written separately in publications (for example, the species name tigris is not written alone. However in this case the term tigris is seen, but only when referring to the common name for a female tiger.) |
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The law of first priority. This is a law that is more commonly exercised in paleontology than with living organisms. The law of first priority gives the right to name an organism to the first person who proposes it. This becomes complicated in paleontology when there is a dispute over how a sample should be classified, and is explained in more detail in the paleontology section. |
How are the animals on the site organized?
Unlike the living cats, the fossil cats are organized with a genus for each page. Under each genus is a list of each individual species, for example the genus Smilodon is followed by the species such as Smilodon fatalis or Smilodon populator. The genus is put before the species as is the proper way to identify an individual.
Some books only have a letter before the species, what does that mean?
If it is made clear what genus is being discussed in a publication, it can be referred to with the first letter before a species. As in the entire genus name, the letter must be capitalized. For example, once it has been identified which genus the author is referring to a publication or section discussing the Smilodon genus can refer to separate species in this form : S. fatalis or S. populator.
How do you classify an extinct animal?
Unfortunately, you can't classify a fossil as well as a living organism. You can't tell if they were able to interbreed and produce fertile offspring, and many have no genetic information, since fossil animals are actually rock. (The bones have been replaced by other minerals during the fossilization process..) Extinct animals must therefore be classified based on similar morphology, or the physical makeup of an organism.
Variation or new organism?
All organisms have some variation among their populations, different sizes, body shapes, etc. To propose a fossil is a new organism, there should be one of two factors present. One is amount found. Usually a single fossil, or specimen, is not enough to prove this was a separate species. In most cases a sample must be found. A sample is a large collection of fossils sharing similar characteristics. A sample can be evidence that a fossil specimen's appearance is not only variation.
Another way may be with the use of math. Normal ranges of variation are plotted on a graph against the new specimen. If there is sufficient difference, then the specimen may be a new organism. For example, if a specimen has a feature that is highly unlike the existing samples may be too different to be in the normal range of variation.
Problems in classification.
Not every paleontologist agrees on how a fossil should be classified. There are two basic views that most paleontologists follow. Some try to classify organisms into as little categories as possible. These tend to look for similarities between new samples and existing samples. They only recognize a new classification if there is enough evidence to convince them it exists. Other paleontologists classify each new specimen into a new category until it is proven to be similar enough to an existing one.
How does this affect the name of an organism?
When a paleontologists feels there is enough information to prove a fossil sample is a new species, the name is proposed before the Linnean society. This is where the law of first priority is important. The first proposed name is always used, so if it found later that a certain fossil belongs in a different classification, the newest name is disregarded. An example of this comes from anthropology: A genus and species were recognized as Australopithecus boisei. Later, a specimen was found and given the genus Zinjanthropus. When it was found that this specimen belonged in the Australopithecus genus, the new name was discarded. Because scientists have different criteria for classification, some may refuse to recognize a certain genus or species. Their classification is sometimes accepted by others if they have a convincing argument for why they chose a certain classification. Because it is not always certain in the absence of any information on genetics or reproductive behavior, the classifications sometimes change frequently and are not always considered by some.
How do scientist know how an animal lived?
No one can be sure, as a living environment can't be seen. As with all aspects of paleontology, most reconstructions are guesswork based on fossils. Many science need to work together to properly reconstruct an ancient landscape.
Geologists are pivotal in any paleontological study. Geologists can determine a great deal about environments based on rock formations. Among the factors geologists can determine are: erosion patterns can give clues such as bodies of water present, natural disasters such as earthquakes and volcanoes, and most importantly which species co-existed based on the strata (level of rock) they are found in. Strata can also give a rough idea of the age of a fossil.
Paleobotonists (scientists who study ancient plants) can determine which plant life was present based on not only fossils of plant parts but pollen fossils as well. Pollen is often a great indicator of plant life as it is indestructible. (The only downfall to using pollen is that pollinating plants were not present for all of Earth's history.) One the types of plants are known, it can be determined if an area was grassland, desert, forest, etc.
Zoologists can make parallels of ancient environments based on living environments. These are not exact parallels as the living and extinct animals probably had different behavior patterns unique to their species. But they do provide a general basis to modify to fit the fossil evidence. Modern species can also provide a general basis for behavior, but again the example usually needs to be modified.
How do paleontologists decide what colors an animal might have been?
Coloring is the most difficult to determine. Although it many times is based on environment, this is sometimes not the case. For example, certain living species are colored to attract mates or to determine which possible mat is of their own group. ( A species of primates called guenons have distinct facial colorings for each subspecies or 'breed'.) Coloring is usually given a best guess, as it is difficult to say who is right.
Definition
Evolution is the gradual changing of organisms over time. Despite old depictions of evolution as a 'ladder' leading to a species standing at the pinnacle, evolution is not a 'driving force', and there is no eventually 'goal' in the changes that occur in organisms.
How does evolution operate?
The key to evolution is in reproduction and variation. Organisms with designs that are helpful, or well adapted to their current living conditions, will be able to reproduce and pass these traits on to the next generation. What causes apparent changes is genetic variation. For each trait, there will be a difference among individuals. As the environment or other living conditions change, these degrees of variation become more or less advantageous. Those with the more advantageous traits will survive to produce more offspring, with a new set of variations. Over several generations, the changes become significant enough to be classified as a distinct species.
Extinction does not mean an organism was 'stupid', or 'inferior', it merely means a species was not able to adapt to changes quick enough. This can be due to a sudden change in environment, the introduction of a species which competes with native fauna, or a slow reproductive rate preventing new generation from reaching maturity in large enough numbers to survive change.
Convergent evolution is the development of similar traits independently in different species. An example of this is dolphins and sharks. Both have streamlined bodies very similar in shape, but are not related. The design developed in both species as one which was advantageous for movement and catching prey in a marine environment, and not because they share a common ancestor.