Living things are placed into certain kingdoms based on how they obtain their food, the types of cells that make up their body, and the number of cells they contain. Phylum is the next level following kingdom in the classification of living things. It is an attempt to find physical similarities among organisms within a kingdom.
These physical similarities suggest that there is a common ancestry among those organisms in a particular phylum. Classes are way to further divide organisms of a phylum. Organisms of a class have even more in common than those in an entire phylum. Order Organisms in each class are further broken down into orders. A taxonomy key is used to determine to which order an organism belongs. A taxonomy key is a checklist of characteristics that determines how organisms are grouped together. Families Orders are divided into families.
Organisms within a family have more in common than with organisms in any classification level above it. Because they share so much in common, organisms of a family are said to be related to each other. Within each of those sections, there will be more divisions like fiction, non-fiction. Within those sections there will be even more divisions such as mystery, science fiction, and romance novels in the fiction section. Finally you will get down to a single book.
Biological classification works the same way. So the hunt for a useful and unambiguous classification system continued. Prerequisites Any classification system requires four things: Data or evidence For every object or organism to be classified, a lot of information is needed. This data is usually provided by systematics ; an examination of organisms from many points of view.
Such data can include input from almost all fields of science, including molecular biology, field studies, collections, morphological analysis, genetics, behavioral studies, chemistry, and anatomy.
A systematic study, at its best, generates a very large amount of data about organisms which can then be used to determine the range of similarities and differences between them. The appropriate groups Taxonomy is a theoretical branch of biology in which taxonomists try to devise appropriate groups into which they can unambiguously place all living things.
Moving down through each level of classification, the number of species in the group decreases Table 1. Two species within the same genus likely share a recent common ancestor in their evolutionary history. These two species would be more closely related to each other than two species classified into different families.
The levels of classification might also provide information on the evolutionary history of a species or other taxonomic group. Such is the case with the coelocanths Latimera spp. West Indian ocean coelacanth Latimeria chalumnae ; Fig.
They are also the only living members of their family Latimeriidae and of their order Coelacanthiformes. All other species belonging to these levels of classification are now extinct. Coelacanths are also some of the very few surviving fish species within the class Sarcopterygii, a group known as the lobe-finned fishes.
All four-limbed vertebrate animals—amphibians, reptiles, birds, and mammals—also belong to class Sarcopterygii. The coelacanths, and the six species of lung fish, are more closely related to each other and to the four-limed vertebrates than to other fishes.
For this reason, the coelacanth offers a rare glimpse into the evolutionary history of vertebrate animals and their limb-development. Classification systems are used in many ways. Compare the classifications shown in Fig. Most people know something about water vehicles, so it is not necessary to say that a speedboat has a motor.
In the same way, there is general knowledge that a tuna is classified as a fish. So, a tuna can be described without needing to say that it is a fish because. Thus, if we make the statement that a skipjack tuna is caught while fishing in a speedboat, many details can be left out of the description because there is general, underlying knowledge of the classification of boats and tuna.
This use of italics is part of the rules that the scientific community has developed for the naming of organisms. There are three main codes that govern the naming of organisms. Scientific names are useful outside of science. Common names vary from place to place, and the scientific nomenclature system helps eliminate confusion.
This example also brings up another problem with common names. Notice that one of the common names for this fish uses the word dolphin, which is also the common name of a marine mammal. Scientific names are also valuable in navigating the classification system. The classification system provides great deal of information about the characteristics of organisms.
Using scientific names can therefore act as a shorthand method for describing a plant or animal. For example, following a whale stranding along the Maui coastline, an observer might record this information:. This is all information needed to identify the organism and avoid mixing it up with other similar organisms. Of course, when reporting the mammal stranding to her supervisor, the observer will report stranding of a Megaptera novaeangliae , which is the species name that describes the humpback whale.
The scientific name Megaptera novaeangliae encompasses all of the described features. Most binomial names are Latin terms. However, some binomial names are Greek, and some are derived from the names of their discoverers or other scientists. When Carl Linneaus developed his classification system, almost all educated people were trained in Latin and Greek. No matter what country they came from, people could communicate with one another using these languages.
Because Latin and Greek were the common languages of scientists, Latin and Greek were used to develop a universal classification system.
Even today, the English language has many words that were originally Latin or Greek in origin. Latin and Greek terminology is also useful because it tends to be very descriptive of the species in question Table 1.
For example, consider the great white shark. However, the great white shark is universally known by its scientific name of Carcharodon carcarias around the world.
The root word — odon sounds like the familiar type of dentist—the orth odon tist. In fact, odon is a root word that means tooth. Carcharo - means jagged. When put together, the word Carcharodon means jagged-toothed shark. The person who named this shark incorporated this observational fact within the name. Create names for 15 species of sharks and compare them with the actual scientific and common names.
Although more than two million different species have been identified by scientists, millions more are likely still undiscovered. A dichotomous key is a tool used by scientists to help them identify organisms that are already classified and described. The key presents a series of choices that leads the user to the identification of the organism. The series of choices is similar to a series of contrasting hypotheses that are tested by examining the organism to disprove one hypothesis and support the other.
A detailed description exists for every organism with a scientific name. The final step in any identification should be to compare the specimen to a species description. It is important to make this comparison because it is possible to misinterpret the information presented, and it is also possible that the specimen was not in the key or that the specimen is even a new, undescribed species. If the diagnosis does not contradict what is known about the specimen, the identification is supported.
For example, if the specimen was caught in water one meter deep, but the diagnosis says that the organism only lives at depths of meters or more, there may be an error in the identification.
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