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From the Stacks. Gulf of Guinea Expeditions. Marine Exploration. Naturalist Notebook. The best way to ensure that the organism is correctly identified is to confirm that it matches in every way with the species description.
Most keys are regional, based on the animals of the place where the key was developed. Most keys also have a section that only identifies the families in the region. This is a good place to start because families are often easier to separate and identify than individual species.
It is also important to compare the final identification to a guidebook or other source in case the key did not contain the specimen in question. The goal of biological classification is to group organisms together in terms of their relatedness to one another. There is a long-running debate within the scientific community about whether the Linnean system should be revised to better show relatedness.
There are several arguments for revision:. The phylogenetic method of classification uses shared, unique characters—heritable features that vary between individuals. In contrast, the Linnean system is focused on ranking organisms in groups. Linnean groups share similar traits, but the groups often do not reflect evolution or levels of diversity.
Phylogenetics, on the other hand, is focused on showing the evolutionary relationships between organisms. A phylogenetic tree is a branching diagram used to show the evolutionary relatedness of organisms based on similarities and differences in their characteristics Fig.
The length of the branches on a phylogenetic tree represents changes in characteristics over evolutionary time. The term synapomorphy is used to describe shared, unique characteristics. Synapomorphies are present in organisms that are related through an ancestor who genetically passed the trait on to its descendants. Organisms outside the group do not have the synapomorphy. Phylogenetic trees show groups using synapomorphies. A monophyletic group contains all of the descendants of a single common ancestor—an ancestor shared by two or more descendent lineages.
In many cases, the common ancestor is unknown. For example, all members in the primate infraorder Simiiformes shown in yellow in Fig. That means the relationship of all of the primates in this group is supported by synapomorphies. The more synapomorphies two species have in common, the more closely related they are hypothesized to be. Sometimes scientists misinterpret groups as being monophyletic when they are not.
A character that appears unique might evolve more than once in different groups, or it may be lost or reversed within a group. Homoplasies are similar characteristics, like the wings of birds and bats, that do not reflect relatedness.
Bird wings and bat wings are not related because they evolved from different genetic origins, even if both types of wings serve the function of flight. Behaviors can also be used to classify organisms, and, like other traits, can be the result of a synapomorphy or homoplasy.
For example, the night-active primates, Lorises and Tarsiers, are not grouped together in Fig. This is because their night-time behavior is not a synapomorphy a shared derived character. In order for Lorises and Tarsiers to be included in the same monophyletic group, the group would need to be expanded to include lemurs with the tarsiers, monkeys, apes, and their last common ancestor black dot.
As we learn more about genetics, and evolution, it is important to continue to explore and reassess relationships between organisms. Ideas about relationships need to be re-evaluated as discoveries are made and new information is found.
Advances in biotechnology now allow scientists to use molecular characteristics to organize organisms. Molecular phylogenies are made by examining the differences in the DNA sequence of the organisms being compared. There are many genetic similarities between organisms. For example, human and mouse genes have a similarity of about 85 percent, and human and chimpanzee genes have about 96 percent similarity.
For this reason, it is easier to study differences in genetics rather than similarities. For scientists to gain information about relationships between widely diverse species like those from different domains or kingdoms they use genes that are similar. Conserved genes are genes that have not changed much over evolutionary time. Gene conservation usually occurs in functionally important genes because these types of genes are needed to assemble proteins essential to survival.
Coding regions are segments of DNA that are translated to RNA and are important for the function of a gene or gene product. Note in Fig.
The conserved parts of the 16S rRNA gene are the places that provide information about the relationships between the organisms being compared Fig.
In this case, E. This is not unexpected since E. These non-coding regions are not considered functional parts of genes.
However, non-coding regions do play a role within the cell. These non-coding regions of DNA are known as introns. They are areas where less conservation and more genetic mutation is expected. Scientists use introns to examine how organisms have changed over time. The rate of change over time can give clues as to how long ago organisms diverged from each other in a phylogenetic sense.
This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. You might want similar subjects grouped together, and so you can find everything much faster. Same goes for biology. When there are millions of species of organisms, grouping them together can help study them a lot faster and easier. Why is classification important in biology?
Nam D. For example, if an animal is classified as a cat, immediately we already know that it has four legs, a tail, ears and whiskers, based on the way they are classified. Knowing classifications also helps to predict the characteristics that a particular animal might have, based on the observation of others within the same classification.
Still using the example of a cat - if someone has a house cat and has observed that the house cat can jump well, and they know that a tiger is also a cat, they might predict that tigers can jump well, even without knowing very much about tigers.
Additionally, classification enables scientists to explain the relationships between organisms, which is helpful in trying to reconstruct the evolutionary roots of a particular species.
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