Why is it important to classify the millions of species on earth? People are always looking for more meaningful ways to organize the knowledge they have about the world around them.
One of the ways that we attempt to achieve this goal is by categorizing things into various groups according to the ways in which they are similar to and distinct from one another. Consider some of the items that are categorised in and around your house or school, as well as the ways that are utilized to categorize inanimate objects.
The organization of living things into categories is the subject of taxonomy, which is one of the subfields in biology. Taxonomy is the formal categorization of organisms into groups based upon those supposed links.
It is the study of the connections that exist between living things as well as the formalization of that classification. The similarities and differences between organisms are used as the basis for classifying them.
Consider your own direct lineage of ancestors and grandparents. People who are connected to you by birth are considered to be your biological relatives. Examples of biological relatives are your parents, siblings, sisters, cousins, aunts, uncles, and grandparents. When we say that two different creatures are related, we indicate that they descended from the same ancestor.
The more recent the common ancestor, the greater the genetic similarity between the creatures. Due to the fact that you and your closest relatives are descended from the same parent, your brothers and sisters will be your closest living relatives. Your grandparents are the common ancestor that you share with your cousins, which means that the distance between you and them is not as close. Your grandparents are the parents of your parents.
Taxonomy considers not only the genetic but also the functional similarities between people in its classifications. People are mammals, but they are more closely related to primates, like apes, than they are to other mammals, like dogs.
Dogs and other mammals are not primates. When contrasted with the face and paws of a dog, the hands and facial characteristics of humans and apes are functionally comparable to those of dogs. This piece of evidence lends credence to the hypothesis that canines and humans have a more distant common ancestor than apes do.
Even while scientists have catalogued approximately 2 million different species on Earth, it is believed that this figure represents just a tiny fraction of the total number of species that are now active on the planet. There is a vast fossil record of plants and animals that existed in the past and that may be distant cousins of extant species. These fossils have been preserved via the process of fossilization.
Amazingly complicated and complex are the links that exist between all of these many species that are still alive and others that have died out on our planet. The many species that continue to exist on Earth and those that have since died out are of particular interest to the scientific community, which seeks to categorize both groups.
In addition to this, they have an interest in researching the evolutionary processes that are responsible for the formation and maintenance of new species. Because different species might share appearances that are strikingly similar to one another, it is essential for scientists to define clear criteria that can be used to differentiate one species from another.
Carl Linnaeus, sometimes known as Carl von Linné, was a Swedish scientist who developed a universal method for categorizing and naming plants and animals in the year 1753. His name was Carl Linnaeus. This Linnean approach is still widely used by scientists today to identify living things. It is a structured hierarchy that functions like a tree with levels inside levels (Fig. 1.9). The domain, which is represented by the biggest box, is the level of categorization that contains all of the other levels.
There are three categories that include every living creature that exists on our planet. Bacteria, Archaea, and Eukarya are the three domains that exist. Both bacteria and archaea are examples of single-celled microorganisms that lack nuclei and hence do not have DNA inside their cells.
The majority of archaea are adapted to survive in harsh settings. Archaea and Bacteria were originally considered to be members of the same kingdom, which was referred to as Monera; however, researchers eventually realized that the Bacteria and Archaea were separate from one another. Archaea are more closely related to eukaryotic cells than they are to bacterial cells.
The progression of life on Earth over the course of the last four billion years has led to the emergence of an extremely diverse array of species. Over the course of more than two thousand years, people have been attempting to categorize the vast variety of living things.
Taxonomy is the name given to the scientific study of the classification of creatures. Understanding both the current variety of life on Earth and its evolutionary history in the past requires classification as an essential step along the way.
The Linnaean categorization system is the progenitor of all contemporary methods of taxonomy and classification. In the 1700s, Swedish botanist Carolus Linnaeus was the one who came up with the concept.
He made an effort to categorize all of the living creatures that were known during his day. He classified creatures according to their evident similarities in terms of their physical characteristics, such as the number of legs or the form of the leaves.
Linnaeus is often regarded as the “father of taxonomy” because to the significant contributions he made to the field. Watching the film that can be found at this link will provide you with further information on Linnaeus and the classification scheme that he developed.
The Linnaean system of categorization is comprised of a hierarchical arrangement of categories, which are referred to as taxa (singular, taxon). The taxonomic scale extends from the kingdom down to the species (see Figure below).
The kingdom is the most extensive and all-encompassing organization in this category. It is made up of different species that are only comparable in a few fundamental ways to one another. The kingdoms of plants and animals are two such examples. The species is the most specific and limited collection of living things. It is made up of organisms that are sufficiently related to one another in order for them to jointly generate viable offspring. A genus is a collection of closely related species that are grouped together.
Linnaeus’s system for identifying species is often cited as the single most important contribution he made to the field of science. By using this system, which is known as binomial nomenclature, each species is given a distinct, two-word Latin name consisting of the name of the genus and the name of the species. Homo sapiens, which is the Latin term for humans and consists of two words, is one example. The exact translation of the word is “wise human.” This makes a joke about how large our brains are.
Why is it so vital to have two different names? It is comparable to the fact that individuals have both a first and a last name. It’s possible that you know more than one person whose first name is Michael, but by the time you add their last name, it should be clear who you’re referring to. In a similar manner, a species may be identified in a way that is completely unique by having two names.
Linnaeus is credited with being the first person to publish a categorization system. Since then, an abundance of previously unknown species have been found. It has also become possible to understand the biochemistry of a great many creatures. After some time, researchers came to the conclusion that Linnaeus’s method of categorization required certain adjustments.
The introduction of a new taxon that was given the name “domain” was one of the most significant modifications that the Linnaean system underwent. The term “domain” refers to a taxon that is broader and more encompassing in scope than “kingdom.” Bacteria, Archaea, and Eukaryota are the three basic categories of life that may be found on Earth, according to the majority of scientists (see Figure below).
Archaea and bacteria are both collections of single-celled, prokaryotic organisms. The kingdom Eukaryota is comprised of all eukaryotic organisms, ranging from single-celled protists to multicellular humans. The kingdoms of Animalia (animals), Plantae (plants), Fungi (fungi), and Protista (protists) are all included in this realm.
The ribosomal RNA nucleotide sequences of several living creatures were compared to one another in order to construct this phylogenetic tree. Bacteria, Archaea, and Eukarya are the three categories that make up the tree’s division of all species into their respective domains. The Eukarya domain is home to eukaryotic organisms including humans and other animals. Based on the information presented here, the species that belong to the domain Eukarya seem to have had a more recent common ancestor with Archaea than they did with Bacteria.
On our planet, there are about 8.7 million different eukaryotic species, with a margin of error of 1.3 million. The most recent estimate of the biodiversity is based on a new way of prediction, and as a result, the range of ‘best estimates’ has been drastically narrowed. Previously, this range was between 3 million and 100 million. This indicates that an astounding 91 percent of marine species and 86 percent of terrestrial species have not yet been identified.
Camilo Mora, a marine ecologist at the University of Hawaii at Manoa, and his colleagues at Dalhousie University in Halifax, Canada, have discovered a consistent scaling pattern among the different levels of the taxonomic classification system (order, genus, species, and so on). This pattern enables the total number of species to be predicted. Mora is a member of the Society for Marine Biology. Today, the study was posted online in the journal PLoS Biology1.
Mora believes that one of the most significant problems in all of science is to determine the total number of species that inhabit the earth. He states that the discovery of this number fulfills a fundamental desire in scientific research.
A biologist named Bob May from the University of Oxford in the United Kingdom, who authored a commentary on the work2, is of the same opinion. According to him, it is of the utmost importance to have an accurate count of the number of flora and fauna that inhabit the earth. In addition, he emphasizes the importance of the topic from a practical standpoint, saying, “Without this understanding, we cannot even begin to address concerns such as how much variety we may lose while still preserving the ecosystem services that civilization relies upon.”
However, despite the tireless efforts of field taxonomists, we will not have the number any time in the near future. During the more than 250 years that have passed since the Swedish scientist Carl Linnaeus established the study of taxonomy, a total of 1.2 million species have been recognized and categorized. This represents less than 15 percent of Mora’s new total. May predicts that in order to finish the mission of documenting all species, it will take another 480 years at the current rate of progress.
Instead, scientists have attempted to estimate the total number of species based on the number of species that are already known. Some of the projections are not much more than educated guesses, while others are rather accurate. Mora claims that these forecasts cannot be relied upon since even the opinions of experts are subject to change. Other methods include assumptions that he deems “unreliable and simple to breach,” thus he recommends avoiding such.
The methodology developed by Mora is predicated on an examination of the taxonomic categorization of each of the 1.2 million species that are now known to science. Linnaeus’ system is structured in the shape of a pyramid, with the lower the category being, the greater the number of creatures it comprises. There are more species than genera, more genera than families, more families than orders, etc., all the way up to the highest level, which is called a domain.
Mora and his colleagues demonstrate that there is a constant numerical trend that links the numbers in each category, and that this can be used to predict how many entities there should be in poorly catalogued levels, such as species, based on the numbers in higher levels that are much more comprehensively described. Mora and his colleagues also demonstrate that this can be used to predict how many entities there should be in levels that are more comprehensively described.
However, the strategy is not applicable to prokaryotes, which include bacteria and archaea, given that the higher taxonomic levels of prokaryotic organisms are not as well cataloged as eukaryotic organisms are. Mora’s figure takes into account a more cautious estimate known as the “lower limit” of around 10,000 prokaryotes; nonetheless, it is very probable that the actual number of prokaryotes is in the millions.
According to him, the fact that we are able to verify the methodology is what makes it stand out from other methods. “We were able to prove that we could correctly anticipate the number of species by evaluating the predictions against well-catalogued groupings such as mammals, birds, reptiles, and amphibians,”
The data also shows that certain bands are substantially more well-known than others in the industry. For instance, only around 12 percent of the expected land mammal species and 7 percent of the anticipated land fungal species have been recorded up to this point, although about 72 percent of the predicted 298,000 plant species on land have already been described.
May is overcome with awe. “This way of thinking appeals to me. Not only is it creative and original, but the resultant figure is within the range of what I would estimate to be the most likely outcomes myself!”