How many genus are there in the world

To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. There are 8. The latest biodiversity estimate, based on a new method of prediction, dramatically narrows the range of 'best guesses', which was previously between 3 million and million.

Camilo Mora, a marine ecologist at the University of Hawaii at Manoa, and his colleagues at Dalhousie University in Halifax, Canada, have identified a consistent scaling pattern among the different levels of the taxonomic classification system order, genus, species and so on that allows the total number of species to be predicted.

The research is published in PLoS Biology 1 today. Mora argues that knowing how many species there are on Earth is one of the most important questions in science. He also highlights the practical significance: "Without this knowledge, we cannot even begin to answer questions such as how much diversity we can lose while still maintaining the ecosystem services that humanity depends upon.

But the unstinting efforts of field taxonomists are not going to provide the number any time soon. In the more than years since Swedish biologist Carl Linnaeus began the science of taxonomy, 1. At this pace, May estimates that it will take another years to complete the job of recording all species.

Instead, scientists have tried to predict the total number of species from the number already known. Some of the estimates amount to little more than educated guesses. Other approaches use assumptions that he describes as "unreliable and easy to break". Mora's method is based on an analysis of the taxonomic classification for all 1.

Linnaeus's system forms a pyramid-like hierarchy — the lower the category, the more entities it contains. There are more species than genera, more genera than families, more families than orders and so on, right up to the top level, domain. Mora and his colleagues show that a consistent numerical trend 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, from the numbers in higher levels that are much more comprehensively described.

However, the method does not work for prokaryotes bacteria and archaea because the higher taxonomic levels are not well catalogued as is the case for eukaryotes. A conservative 'lower bound' estimate of about 10, prokaryotes is included in Mora's total but, in reality, they are likely to number in the millions.

Derek P. Alastair G. Georgina M. Mace, Academic Editor. Author information Article notes Copyright and License information Disclaimer. Received Nov 12; Accepted Jul Copyright Mora et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. This article has been cited by other articles in PMC.

Figure S2: Sensitivity analysis due to changes in higher taxonomy. Figure S3: Assessing the effects of data incompleteness. Figure S4: Comparison of the fits of the hyperexponential, exponential, and power functions to the relationship between the number of higher taxa and their numerical rank. Abstract The diversity of life is one of the most striking aspects of our planet; hence knowing how many species inhabit Earth is among the most fundamental questions in science.

Author Summary Knowing the number of species on Earth is one of the most basic yet elusive questions in science. Open in a separate window. Figure 1. Predicting the global number of species in Animalia from their higher taxonomy. Figure 2. Validating the higher taxon approach. Table 1 Available methods for estimating the global number of species and their limitations.

Case Study Limitations Macroecological patterns Body size frequency distributions. By extrapolation from the frequency of large to small species, May [7] estimated 10 to 50 million species of animals. May [7] suggested that there was no reason to expect a simple scaling law from large to small species. Further studies confirmed different modes of evolution among small species [4] and inconsistent body size frequency distributions among taxa [4].

Latitudinal gradients in species. By extrapolation from the better sampled temperate regions to the tropics, Raven [10] estimated 3 to 5 million species of large organisms.

May [2] questioned the assumption that temperate regions were better sampled than tropical ones; the approach also assumed consistent diversity gradients across taxa which is not factual [4]. Species-area relationships. Diversity ratios Ratios between taxa. Ratio-like approaches have been heavily critiqued because, given known patterns of species turnover, locally estimated ratios between taxa may or may not be consistent at the global scale [3] , [12] and because at least one group of organisms should be well known at the global scale, which may not always be true [15].

Host-specificity and spatial ratios. Known to unknown ratios. Taxonomic patterns Time-species accumulation curves. This approach is not widely applicable because it requires species accumulation curves to approach asymptotic levels, which is only true for a small number of well-described taxa [22] — [23].

Authors-species accumulation curves. This is a very recent method and the effect of a number of assumptions remains to be evaluated.

One is the extent to which the description of new species is shifting from using taxonomic expertise alone to relying on molecular methods particularly among small organisms [26] and the other that not all authors listed on a manuscript are taxonomic experts, particularly in recent times when the number of coauthors per taxa described is increasing [21] , [38] , which could be due to more collaborative research [38] and the acknowledgment of technicians, field assistants, specimen collectors, and so on as coauthors Philippe Bouchet, personal communication.

Analysis of expert estimations. Robustness in the estimations is assumed from the consistency of responses among different experts. Estimates can vary widely, even those of a single expert [5] , [6]. Table 2 Currently catalogued and predicted total number of species on Earth and in the ocean.

Predictions for prokaryotes represent a lower bound because they do not consider undescribed higher taxa. For protozoa, the ocean database was substantially more complete than the database for the entire Earth so we only used the former to estimate the total number of species in this taxon. All predictions were rounded to three significant digits. Assessment of Possible Limitations We recognize a number of factors that can influence the interpretation and robustness of the estimates derived from the method described here.

Species definitions An important caveat to the interpretation of our results concerns the definition of species. Changes in higher taxonomy Increases or decreases in the number of higher taxa will affect the raw data used in our method and thus its estimates of the total number of species. Figure 3. Assessment of factors affecting the higher taxon approach.

Changes in taxonomic effort Taxonomic effort can be a strong determinant of species discovery rates [21]. Completeness of taxonomic inventories To account for yet-to-be-discovered higher taxa, our approach fitted asymptotic regression models to the temporal accumulation curve of higher taxa. Subjectivity in the Linnaean system of classification Different ideas about the correct classification of species into a taxonomic hierarchy may distort the shape of the relationships we describe here.

Discussion Knowing the total number of species has been a question of great interest motivated in part by our collective curiosity about the diversity of life on Earth and in part by the need to provide a reference point for current and future losses of biodiversity.

Materials and Methods Databases Calculations of the number of species on Earth were based on the classification of currently valid species from the Catalogue of Life www.

Statistical Analysis To account for higher taxa yet to be discovered, we used the following approach. Survey of Taxonomists We contacted 4, taxonomy experts with electronic mail addresses as listed in the World Taxonomist Database www.

DOC Click here for additional data file. Figure S2 Sensitivity analysis due to changes in higher taxonomy. Figure S3 Assessing the effects of data incompleteness. Figure S4 Comparison of the fits of the hyperexponential, exponential, and power functions to the relationship between the number of higher taxa and their numerical rank. Footnotes The authors have declared that no competing interests exist. References 1. May R. Tropical arthropod species, more or less?

How many species inhabit the earth? Sci Amer. Storks N. How many species are there? Biodiv Conserv. Gaston K, Blackburn T. Blackwell Science Ltd; Pattern and process in macroecology. Erwin T. Conserv Biol. Bouchet P. Duarte C. M, editor. The magnitude of marine biodiversity. The exploration of marine biodiversity: scientific and technological challenges. How many species are there on earth? Thomas C. Fewer species. Tropical forests: their richness in Coleoptera and other arthropod species.

Coleopterists Bull. Raven P. Disappearing species: a global tragedy. Bottoms up for the oceans. Lambshead P. D, Boucher G. Marine nematode deep-sea biodiversity-hyperdiverse or hype? J Biogeogr. Grassle J. F, Maciolek N. Deep-sea species richness: regional and local diversity estimates from quantitative bottom samples. Am Nat. Briggs J. C, Snelgrove P. Marine species diversity. Gaston K. The magnitude of global insect species richness. Poore C. B, Wilson G.

Marine species richness. In this genus example, several species are included. However, only one species remain extant, i. Below is the genus list of human species genus Homo. These species possess a highly developed brain and advanced skills, particularly in abstract reasoning, problem-solving, self-awareness, and articulate communication.

They walk on two legs, with erect carriage. They have relatively smaller teeth than other primates. These features set them apart from other genera, such as Australopithecus.

The genus Australopithecus also belongs to the tribe Hominini. They were more morphologically similar to the chimpanzees and bonobos than to humans since their body is fully covered with hair. Astralopithecus , though, play a part in human evolution. The genus Homo is presumed to originate from one of the species of this genus million years ago. Members of this genus were already extinct. They diverged from the chimpanzees. They have a grasping hallux or big toe that enabled them to move from one tree to another with relative ease.

This genus as the earliest human ancestor is a matter of debate though since they likely behave more like a chimpanzee than humans. Sahelanthropus is a genus comprised of extinct species from Miocene epoch, particularly during the time close to that when chimpanzees and humans diverged.

Seed plants are vascular plants. They differ from the other vascular plants in producing seeds that germinate into a new plant. Two major plant divisions are covered: the angiosperms and the gymnosperms. Read More. The hominid family diversified from the apes around 6 to 8 million years ago. Since then, the evolutionary path has proved to be nothing short of phenomenal. This tutorial elucidates the emergence of the hominid family from where the human ancestral line came from Find out more about New Zealand's unique biodiversity by exploring a range of different ecosystems and the key role of some endemic species in these ecosystems Meet some of New Zealand's unique fauna, including endemic insects, frogs, reptiles, birds, and mammals, and investigate why many have such distinctive features.

You'll also find out about why there are so few native mammals and the impact of introduced pests on the unique natural ecosystems The evolution of the species of the genus "Homo" led to the emergence of modern humans.

Find out more about human evolution in this tutorial that elaborates on the different Homo species in the early geologic time.

Subspecies comparison of the Genus: Corucia. Malaria : Plasmodium togetherness a strategy for breeding success. What is a species? Definition of species, different approaches. Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum.

Genus — definition. Table of Contents. Genus is a taxonomic rank among the eight major taxonomic ranks in a biological classification. It is below the family and above the species. A genus may be comprised of one or more species. A family, in turn, consists of a genus or several genera. Seed Plants Seed plants are vascular plants. The Hominids The hominid family diversified from the apes around 6 to 8 million years ago.

The Homo Species The evolution of the species of the genus "Homo" led to the emergence of modern humans. Related Articles