CLASSIFICATION OF SPECIES.

Indian Spices
. Following the introduction of Botany, with a growing interest in Nature, and with wider exploration to the Americas, Asia and Africa, scientists started to get interested in the commonalities and divergencies of animals, and began to classify species. The term Specie (Latin for "Like" as in alike), was first introduced at the beginning of the 17th century.


THE IDEA OF "SPECIES"

The idea of "species" has a long and continuing history. It is one of the most important levels of classification, for several reasons:
It often corresponds to what lay people treat as the different basic kinds of organism - dogs are one species, cats another.
It is the considered the best method - to date - by which scientists typically refer to organisms.
It is the highest taxonomic level which mostly cannot be made more or less inclusionary.
After centuries of use, the concept remains central to
biology and a host of related fields, and yet also remains at times ill-defined.

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are often used, such as based on similarity of DNA. Specific traits that have changed an animal (for example skin color or size) may further subdivide species into subspecies.

This technical article in Wikipedia details and wrestles with the problems with the classifications of Species. I will try to summarize the status of classification here:


BIOLOGIST'S WORKING DEFINITION OF A SPECIE

Biodiversity in a Coral Reef
Classification is a somewhat reliable method of identifying particular species are essential for stating and testing biological theories and for measuring biodiversity. Traditionally, multiple examples of a proposed species must be studied for unifying characters before it can be regarded as a species. Precise taxonomic rankings are generally difficult to give to extinct species known only from fossils.

As you will see, assigning precise definitions of species even to current animal life is "a work in progress" but become increasingly important in two ways. 1. As we see the impact of climate change on the survivability of a species, and 2. As we discover and look for life on other planets and moons. This field is called
Astrobiology.

Biologists view species as statistical phenomena and not as categories or types. (I find it a bit demeaning to be a statistical phenomenon however, I'm used to it as I'm married and my place in hierarchy is somewhat below that of my dog).

Anyway, the notion of a statistical phenomena as defining species is counterintuitive since the classical idea of species is still widely-held. This is that a specie is seen as a class of organisms exemplified by a "
type specimen" that bears all the traits common to this species.

An Average Prokaryote Cell
Instead, a species is now defined as a separately evolving lineage that forms a single gene pool. Although properties such as genetics and morphology are used to help separate closely-related lineages, this definition has fuzzy boundaries. However, the exact definition of the term "species" is still controversial, particularly in prokaryotes (simple cell species, like certain North Korean leaders and other primitive life forms), and this is called the species problem. Biologists have proposed a range of more precise definitions, but the definition used is a pragmatic choice that depends on the particularities of the species concerned.


COMMON NAMES AND SPECIES


The commonly used names for plant and animal taxa sometimes correspond to species: for example, "lion", "walrus", and "Camphor tree" – each refers to a species. In other cases common names do not: for example, "deer" refers to a family of 34 species, including Eld's Deer, Red Deer and Elk (Wapiti). The last two species were once considered a single species, illustrating how species boundaries may change with increased scientific knowledge.

Because of the difficulties with both defining and tallying the total numbers of different species in the world, it is estimated that there are anywhere between 2 million and 100 million different species.

Each species is placed within a single
genus. This is a hypothesis that the species is more closely related to other species within its genus than to species of other genera. All species are given a binomial name consisting of the generic name and specific name (or specific epithet). For example, the Bengal Tiger is Panthera tigris tigris and the Siberian Tiger Panthera tigris altaica.


A Bengal Tiger

A BENGAL TIGER


A Siberian Tiger

A SIBERIAN TIGER


In scientific classification, a species is assigned a two-part name, treated as Latin, although roots from any language can be used as well as names of locales or individuals. The genus is listed first (with its leading letter capitalized), followed by a second term: for example, gray wolves belong to the species Canis lupus, coyotes to Canis latrans, golden jackals to Canis aureus, etc., and all of those belong to the genus Canis (which also contains many other species). The name of the species is the whole binomial, not just the second term (which may be called specific name for animals).

Carl Linnaeus (Carl von Linné)<br />Carl Linnaeus (Carl von Linné)<br />
ThIs binomial naming convention, later formalized as "The Biological Code of Nomenclature", was first used by Leonhart Fuchs and introduced as the standard by Carolus Linnaeus in his 1758 classical work Systema Naturae. At that time, the chief theory of biological origin was that species represented independent acts of creation by God and were therefore considered objectively real and immutable. Some people today still believe this. This had been the world view since Aristotle in Ancient Greece. (Aristotle was also responsible for the Earth-centric view of the universe. In fact, the more I learn of Aristotle, the less I admire him. Someone tell me I'm wrong please).

Linnaeus's first attempt to define animal species was 11 pages long. His 13th (and final) edition was 3000 pages. This work of Fuchs and then Linnaeus has formed the basis for modern biology. Linnaeus is to Biology as Einstein is to Physics. Linne as he came to be known was world famous in his day and beyond.

The Swiss philosopher Jean-Jacques Rousseau sent him the message: "Tell him I know no greater man on earth." The German writer Johann Wolfgang von Goethe wrote: "With the exception of Shakespeare and Spinoza, I know no one among the no longer living who has influenced me more strongly." Swedish author August Strindberg wrote: "Linnaeus was in reality a poet who happened to become a naturalist".

Catherine II of Russia sent him seeds from her country. He also corresponded with Giovanni Antonio Scopoli, "The Linnaeus of the Austrian Empire", who was a doctor and a botanist in Idrija, Duchy of Carniola (nowadays Slovenia). Scopoli communicated all of his research, findings, and descriptions (for example, olm and dormouse, two little animals which were not known to Linnaeus) to him for several years, but because of the great distance they were never able to meet. Linnaeus named for him the solanaceous genus Scopolia from which scopolamine is derived.

A lot of the details of Linnaeus's work has been revised over time, but he is credited with the development of the "system" by which we can begin to define and categorize species.


DEFINITIONS OF SPECIES

The question of how best to define "species" is one that has occupied biologists for centuries up to today, and the debate itself has become known as "The species problem". The modern theory of evolution depends on a fundamental redefinition of "species". This problem became the original focus of the work of Charles Darwin before he started to focus on the Origin of Species . Prior to Darwin, naturalists viewed species as ideal or general types, which could be exemplified by an ideal specimen bearing all the traits general to the species. Any difference in a specie was regarded as an aberration. This unfortunate definition has led to catastrophes such as Eugenics and even Genocide.

Traditionally, researchers relied on observations of anatomical differences, and on observations of whether different populations were able to interbreed successfully, to distinguish species; both anatomy and breeding behavior are still important to assigning species status. As a result of the revolutionary (and still ongoing) advance in microbiological research techniques, including DNA analysis, a great deal of additional knowledge about the differences and similarities between species has become available in the last few decades. Many populations which were formerly regarded as separate species are now considered to be a single taxon, and many formerly grouped populations have been split. Any taxonomic level (species, genus, family, etc.) can be synonymized or split, and at higher taxonomic levels, these revisions have been still more profound.

Given the complexity of life, some have argued that such an objective definition is in all likelihood impossible, and biologists should settle for the most practical definition. The naming of a particular species today is regarded as a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be confirmed or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as the same species. When two named species are discovered to be of the same species, the older species name is usually retained, and the newer species name dropped, a process called synonymization, or colloquially, as lumping. Dividing a taxon into multiple, often new, taxons is called splitting. Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognizing differences or commonalities between organisms (see lumpers and splitters).

From a taxonomical point of view, groups within a species can be defined as being of a taxon hierarchically lower than a species. In zoology only the subspecies is used, while in botany the variety, subvariety, and form are used as well. In conservation biology, the concept of evolutionary significant units (ESU) is used, which may be define either species or smaller distinct population segments.

But 150 years ago, (before DNA was even dreamed about), Darwin's theories shifted attention from uniformity to variation and from the general to the particular -- or individual.

A
Once our attention is redirected to the individual, we need another way of making generalizations. We are no longer interested in the conformity of an individual to an ideal type; we are now interested in the relation of an individual to the other individuals with which it interacts. To generalize about groups of interacting individuals, we need to drop the language of types and essences, which is prescriptive (for example, telling us what finches should be), and adopt the language of statistics and probability, which is predictive (telling us what the average finch, under specified conditions, is likely to do). Relations will be more important than categories; functions, which are variable, will be more important than purposes; transitions will be more important than boundaries; sequences will be more important than hierarchies.

This shift resulted in a new approach to "species";

Darwin concluded that species are what they appear to be: ideas, which are provisionally useful for naming groups of interacting individuals. "I look at the term species", he wrote, "as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other ... It does not essentially differ from the word variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for convenience sake."

Practically, biologists define species as populations of organisms that have a high level of genetic similarity. This may reflect an adaptation to the same niche, and the transfer of genetic material from one individual to others, through a variety of possible means. The exact level of similarity used in such a definition is arbitrary, but this is the most common definition used for organisms that reproduce asexually (asexual reproduction), such as some plants and microorganisms.

This lack of any clear species concept in microbiology has led to some authors arguing that the term "species" is not useful when studying bacterial evolution. Instead they see genes as moving freely between even distantly-related bacteria, with the entire bacterial domain being a single gene pool.

Nevertheless, a kind of rule of thumb has been established, saying that species of Bacteria or Archaea with close enough genetic characteristics to each other need to be checked by
DNA-DNA Hybridization if they belong to the same species or not. This concept has been updated recently, saying that the border of 97% was too low and can be raised to 98.7%.

In the study of sexually reproducing organisms, where genetic material is shared through the process of reproduction, the ability of two organisms to interbreed and produce fertile offspring is generally accepted as a simple indicator that the organisms share enough genes to be considered members of the same species. Thus a "species" is a group of interbreeding organisms.

This definition can be extended to say that a species is a group of organisms that could potentially interbreed - fish could still be classed as the same species even if they live in different lakes, as long as they could still interbreed were they ever to come into contact with each other. On the other hand, there are many examples of series of three or more distinct populations, where individuals of the population in the middle can interbreed with the populations to either side, but individuals of the populations on either side cannot interbreed. Thus, one could argue that these populations constitute a single species, or two distinct species. This is not a paradox; it is evidence that species are defined by gene frequencies, and thus have fuzzy boundaries.

Currently, we tend to classify species into different ranges. Instead of specific fixed taxonomies, biologists have proposed a range of definitions. Which definition a biologists uses is a pragmatic choice, depending on the particularities of that biologist's research.

In practice, these definitions often coincide, and the differences between them are more a matter of emphasis than of outright contradiction. Nevertheless, no species concept yet proposed is entirely objective, or can be applied in all cases without resorting to judgment.



A Skink - I'd never heard of it either For most vertebrates, classification is made using either the biological species concept (BSC) or, to a lesser extent (or for different purposes) the phylogenetic species concept (PSC). Many BSC subspecies are considered species under the PSC; the difference between the BSC and the PSC can be summed up insofar as that the BSC defines a species as a consequence of manifest evolutionary history, while the PSC defines a species as a consequence of manifest evolutionary potential. Thus, a PSC species is "made" as soon as an evolutionary lineage has started to separate, while a BSC species starts to exist only when the lineage separation is complete. Accordingly, there can be considerable conflict between alternative classifications based upon the PSC versus BSC, as they differ completely in their treatment of taxa that would be considered subspecies under the latter model (e.g., the numerous subspecies of honey bees).

From a taxonomical point of view, groups within a species can be defined as being of a taxon hierarchically lower than a species. In zoology only the subspecies is used, while in botany the variety, subvariety, and form are used as well. In conservation biology, the concept of evolutionary significant units (ESU) is used, which may be define either species or smaller distinct population segments.


So, how many species do we know about (today):

This list shows the numbers of species that are defined at the beginning of the 21st century:

Insects make up the vast majority of animal species.
Bearing in mind the problems with categorising species, the following numbers are only a soft guide. They break down as follows:
Total number of species (estimated):
7 - 100 millions, including:
5-10 million
bacteria,
74,000-120,000
fungi,

297,326 plants, including:
15,000
mosses,
20,000 Ferns and horsetails,
980 gymnosperms,
258,650
angiosperms,
199,350
dicotyledons,
59,300
monocotyledons,
9,671
Red and green algae,

28,849 fungi & other non-animals, including:
10,000
lichens,
16,000
mushrooms,
2,849
brown algae,

1,250,000 animals, including:

1,203,375 invertebrates:
950,000
insects,
81,000
mollusks,
40,000
crustaceans,
2,175
corals,
130,200 others;

59,811 vertebrates:
29,300
fish,
6,199
amphibians,
8,240
reptiles,
9,956
birds,
5,416
mammals.


So, in summary, we have learned that Classification of Species is essential for us to learn about life itself, and give us a benchmark for the future. We have also learned just how difficult it is to classify millions of species, and how this is really a work in progress.

Now, the big question. How did this happen. What is the Origin of the Species?