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Dr Mika Peck and Dr Alice Eldridge introduce us to soundscape ecology and invite viewers to take part in a mini soundscape experiment being carried out on Springwatch.
In wild biomes, a dawn chorus often seems perfectly orchestrated - the calls of all organisms interlock, rather than overlap. This makes sense in evolutionary terms - if individuals of a particular species can't hear each other they can't communicate to mate. This is described as the acoustic niche hypothesis. It makes us think about our acoustic environment, or soundscape, as a resource which individuals compete for - each evolving to fit in their own acoustic niche.

Soundscape Ecology is a relatively new field of ecology, which studies the patterns, causes and consequences of sounds made by humans (anthrophony), other biological organisms (biophony) and geophysical processes (geophony). Rather than individual species' calls, the soundscape approach listens to the chorus as a whole and to all the sounds that can be heard across a particular landscape.

If we can learn to listen to this soundscape in the right way, we can use sound as a biodiversity monitoring tool. Over the last few years we have carried out acoustic surveys across different habitats in the UK and Ecuador. We couldn't possibly listen to every recording individually - this would take a lifetime. So, our research explores how well mathematical summaries of the digital audio recordings - acoustic indices - relate to the number of species present, or other ecologically relevant information.

We make thousands of short recordings, analyse the digital audio files to get numbers for each file and compare these to the number of species and abundance estimates made by ornithologists listening to the same recording. If traditional biodiversity metrics and new computer indices show the same patterns of variation then it suggests they are measuring the same thing. We are seeing strong correlations between the two - results are really promising!

This technology does not replace the expertise of ornithologists, but would allow us to rapidly survey huge areas for biodiversity that we couldn't otherwise access! This could provide a really valuable tool to assess the impacts of climate change, extractive industries, or land use changes and also to evidence the benefits of creating reserves for endangered species.

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BBC Two - Springwatch - Learning to listen to biodiversity

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Dr Mika Peck and Dr Alice Eldridge introduce us to soundscape ecology and invite viewers to take part in a mini soundscape experiment being carried out on Springwatch. In wild biomes, a dawn chorus often seems perfectly orchestrated - the calls of all organisms interlock, rather than overlap.

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An example of the biodiversity of fungi in a forest in North Saskatchewan (in this photo, there are also leaf lichens and mosses).

Biodiversity (or biological diversity) is the variety and variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa.

Since life began on Earth, six major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic aeon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion. In this period, the majority of multicellular phyla first appeared. The next 400 million years included repeated, massive biodiversity losses. Those events have been classified as mass extinction events. In the Carboniferous, rainforest collapse may have led to a great loss of plant and animal life. The Permian-Triassic extinction event, 251 million years ago, was the worst; vertebrate recovery took 30 million years.

Human activities have led to an ongoing biodiversity loss and an accompanying loss of genetic diversity. This process is often referred to as Holocene extinction, or sixth mass extinction. For example, it was estimated in 2007 that up to 30% of all species will be extinct by 2050. Destroying habitats for farming is a key reason why biodiversity is decreasing today. Climate change also plays a role. This can be seen for example in the effects of climate change on biomes. This anthropogenic extinction may have started toward the end of the Pleistocene, as some studies suggest that the megafaunal extinction event that took place around the end of the last ice age partly resulted from overhunting.

Shown in a museum, various models of species across various taxa and orders visualize the variety of life on earth.

Biologists most often define biodiversity as the "totality of genes, species and ecosystems of a region". An advantage of this definition is that it presents a unified view of the traditional types of biological variety previously identified:

Biodiversity is most commonly used to replace the more clearly-defined and long-established terms, species diversity and species richness. However, there is no concrete definition for biodiversity, as its definition continues to be defined. Other definitions include (in chronological order):

A publication by Wilcox in 1984: Biodiversity can be defined genetically as the diversity of alleles, genes and organisms. They study processes such as mutation and gene transfer that drive evolution.[14]

The 1992 United Nations Earth Summit defined biological diversity as "the variability among living organisms from all sources, including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems".[15] This definition is used in the United Nations Convention on Biological Diversity.[15]

Gaston and Spicer's definition in their book "Biodiversity: an introduction" in 2004 is "variation of life at all levels of biological organization".[16]

Discovered and predicted total number of species on land and in the oceans

According to Mora and her colleagues' estimation, there are approximately 8.7 million terrestrial species and 2.2 million oceanic species. The authors note that these estimates are strongest for eukaryotic organisms and likely represent the lower bound of prokaryote diversity. Other estimates include:

0.7-1 million marine species

1.5-3 million fungi, estimates based on data from the tropics, long-term non-tropical sites and molecular studies that have revealed cryptic speciation. Some 0.075 million species of fungi had been documented by 2001;

The number of microbial species is not reliably known, but the Global Ocean Sampling Expedition dramatically increased the estimates of genetic diversity by identifying an enormous number of new genes from near-surface plankton samples at various marine locations, initially over the 2004-2006 period. The findings may eventually cause a significant change in the way science defines species and other taxonomic categories.

Since the rate of extinction has increased, many extant species may become extinct before they are described. Not surprisingly, in the animalia the most studied groups are birds and mammals, whereas fishes and arthropods are the least studied animals groups.

The World Wildlife Fund's Living Planet Report 2022 found that wildlife populations declined by an average 69% since 1970.[32][33][34]

During the last century, decreases in biodiversity have been increasingly observed. It was estimated in 2007 that up to 30% of all species will be extinct by 2050. Of these, about one eighth of known plant species are threatened with extinction. Estimates reach as high as 140,000 species per year (based on Species-area theory). This figure indicates unsustainable ecological practices, because few species emerge each year. The rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background extinction rates. and expected to still grow in the upcoming years. As of 2012, some studies suggest that 25% of all mammal species could be extinct in 20 years.

In absolute terms, the planet has lost 58% of its biodiversity since 1970 according to a 2016 study by the World Wildlife Fund. The Living Planet Report 2014 claims that "the number of mammals, birds, reptiles, amphibians, and fish across the globe is, on average, about half the size it was 40 years ago". Of that number, 39% accounts for the terrestrial wildlife gone, 39% for the marine wildlife gone and 76% for the freshwater wildlife gone. Biodiversity took the biggest hit in Latin America, plummeting 83 percent. High-income countries showed a 10% increase in biodiversity, which was canceled out by a loss in low-income countries. This is despite the fact that high-income countries use five times the ecological resources of low-income countries, which was explained as a result of a process whereby wealthy nations are outsourcing resource depletion to poorer nations, which are suffering the greatest ecosystem losses.

A 2017 study published in found that the biomass of insect life in Germany had declined by three-quarters in the last 25 years. Dave Goulson of Sussex University stated that their study suggested that humans "appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse."

In 2020 the World Wildlife Foundation published a report saying that "biodiversity is being destroyed at a rate unprecedented in human history". The report claims that 68% of the population of the examined species were destroyed in the years 1970 - 2016.

Summary of major biodiversity-related environmental-change categories expressed as a percentage of human-driven change (in red) relative to baseline (blue)

Rates of decline in biodiversity in the current sixth mass extinction match or exceed rates of loss in the five previous mass extinction events in the fossil record. Biodiversity loss is in fact "one of the most critical manifestations of the Anthropocene" (since around the 1950s); the continued decline of biodiversity constitutes "an unprecedented threat" to the continued existence of human civilization. The reduction is caused primarily by human impacts, particularly habitat destruction.

Since the Stone Age, species loss has accelerated above the average basal rate, driven by human activity. Estimates of species losses are at a rate 100-10,000 times as fast as is typical in the fossil record.

Loss of biodiversity results in the loss of natural capital that supplies ecosystem goods and services. Species today are being wiped out at a rate 100 to 1,000 times higher than baseline, and the rate of extinctions is increasing. This process destroys the resilience and adaptability of life on Earth.

In 2006, many species were formally classified as rare or endangered or threatened; moreover, scientists have estimated that millions more species are at risk which have not been formally recognized. About 40 percent of the 40,177 species assessed using the IUCN Red List criteria are now listed as threatened with extinction-a total of 16,119. As of late 2022 9251 species were considered part of the IUCN's critically endangered.

Numerous scientists and the IPBES Global Assessment Report on Biodiversity and Ecosystem Services assert that human population growth and overconsumption are the primary factors in this decline. However, other scientists have criticized this finding and say that loss of habitat caused by "the growth of commodities for export" is the main driver.

Some studies have however pointed out that habitat destruction for the expansion of agriculture and the overexploitation of wildlife are the more significant drivers of contemporary biodiversity loss, not climate change.

Distribution of living terrestrial vertebrate species, highest concentration of diversity shown in red in equatorial regions, declining polewards (towards the blue end of the spectrum)

Biodiversity is not evenly distributed, rather it varies greatly across the globe as well as within regions and seasons. Among other factors, the diversity of all living things ( biota) depends on temperature, precipitation, altitude, soils, geography and the interactions between other species. The study of the spatial distribution of organisms, species and ecosystems, is the science of biogeography.

Diversity consistently measures higher in the tropics and in other localized regions such as the Cape Floristic Region and lower in polar regions generally. Rain forests that have had wet climates for a long time, such as Yasuní National Park in Ecuador, have particularly high biodiversity.

There is local biodiversity, which directly impacts daily life, affecting the availability of fresh water, food choices, and fuel sources for humans. Regional biodiversity includes habitats and ecosystems that synergizes and either overlaps or differs on a regional scale. National biodiversity within a country determines the ability for a country to thrive according to its habitats and ecosystems on a national scale. Also, within a country, endangered species are initially supported on a national level then internationally. Ecotourism may be utilized to support the economy and encourages tourists to continue to visit and support species and ecosystems they visit, while they enjoy the available amenities provided. International biodiversity impacts global livelihood, food systems, and health. Problematic pollution, over consumption, and climate change can devastate international biodiversity. Nature-based solutions are a critical tool for a global resolution. Many species are in danger of becoming extinct and need world leaders to be proactive with the Kunming-Montreal Global Biodiversity Framework.

Terrestrial biodiversity is thought to be up to 25 times greater than ocean biodiversity. Forests harbour most of Earth's terrestrial biodiversity. The conservation of the world's biodiversity is thus utterly dependent on the way in which we interact with and use the world's forests. A new method used in 2011, put the total number of species on Earth at 8.7 million, of which 2.1 million were estimated to live in the ocean. However, this estimate seems to under-represent the diversity of microorganisms. Forests provide habitats for 80 percent of amphibian species, 75 percent of bird species and 68 percent of mammal species. About 60 percent of all vascular plants are found in tropical forests. Mangroves provide breeding grounds and nurseries for numerous species of fish and shellfish and help trap sediments that might otherwise adversely affect seagrass beds and coral reefs, which are habitats for many more marine species. Forests span around 4 billion acres (nearly a third of the Earth's land mass) and are home to approximately 80% of the world's biodiversity. About 1 billion hectares are covered by primary forests. Over 700 million hectares of the world's woods are officially protected.

The biodiversity of forests varies considerably according to factors such as forest type, geography, climate and soils - in addition to human use. Most forest habitats in temperate regions support relatively few animal and plant species and species that tend to have large geographical distributions, while the montane forests of Africa, South America and Southeast Asia and lowland forests of Australia, coastal Brazil, the Caribbean islands, Central America and insular Southeast Asia have many species with small geographical distributions. Areas with dense human populations and intense agricultural land use, such as Europe, parts of Bangladesh, China, India and North America, are less intact in terms of their biodiversity. Northern Africa, southern Australia, coastal Brazil, Madagascar and South Africa, are also identified as areas with striking losses in biodiversity intactness. European forests in EU and non-EU nations comprise more than 30% of Europe's land mass (around 227 million hectares), representing an almost 10% growth since 1990.

Generally, there is an increase in biodiversity from the poles to the tropics. Thus localities at lower latitudes have more species than localities at higher latitudes. This is often referred to as the latitudinal gradient in species diversity. Several ecological factors may contribute to the gradient, but the ultimate factor behind many of them is the greater mean temperature at the equator compared to that at the poles.

Even though terrestrial biodiversity declines from the equator to the poles, some studies claim that this characteristic is unverified in aquatic ecosystems, especially in marine ecosystems. The latitudinal distribution of parasites does not appear to follow this rule. Also, in terrestrial ecosystems the soil bacterial diversity has been shown to be highest in temperate climatic zones, and has been attributed to carbon inputs and habitat connectivity.

In 2016, an alternative hypothesis ("the fractal biodiversity") was proposed to explain the biodiversity latitudinal gradient. In this study, the species pool size and the fractal nature of ecosystems were combined to clarify some general patterns of this gradient. This hypothesis considers temperature, moisture, and net primary production (NPP) as the main variables of an ecosystem niche and as the axis of the ecological hypervolume. In this way, it is possible to build fractal hyper volumes, whose fractal dimension rises to three moving towards the equator.

A biodiversity hotspot is a region with a high level of endemic species that have experienced great habitat loss. The term hotspot was introduced in 1988 by Norman Myers. While hotspots are spread all over the world, the majority are forest areas and most are located in the tropics.

Brazil's Atlantic Forest is considered one such hotspot, containing roughly 20,000 plant species, 1,350 vertebrates and millions of insects, about half of which occur nowhere else. The island of Madagascar and India are also particularly notable. Colombia is characterized by high biodiversity, with the highest rate of species by area unit worldwide and it has the largest number of endemics (species that are not found naturally anywhere else) of any country. About 10% of the species of the Earth can be found in Colombia, including over 1,900 species of bird, more than in Europe and North America combined, Colombia has 10% of the world's mammals species, 14% of the amphibian species and 18% of the bird species of the world. Madagascar dry deciduous forests and lowland rainforests possess a high ratio of endemism. Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently. Indonesia's 17,000 islands cover 735,355 square miles (1,904,560 km ²) and contain 10% of the world's flowering plants, 12% of mammals and 17% of reptiles, amphibians and birds-along with nearly 240 million people. Many regions of high biodiversity and/or endemism arise from specialized habitats which require unusual adaptations, for example, alpine environments in high mountains, or Northern European peat bogs.

Accurately measuring differences in biodiversity can be difficult. Selection bias amongst researchers may contribute to biased empirical research for modern estimates of biodiversity. In 1768, Rev. Gilbert White succinctly observed of his Selborne, Hampshire "all nature is so full, that that district produces the most variety which is the most examined."

Biodiversity is the result of 3.5 billion years of evolution. The origin of life has not been established by science, however, some evidence suggests that life may already have been well-established only a few hundred million years after the formation of the Earth. Until approximately 2.5 billion years ago, all life consisted of microorganisms - archaea, bacteria, and single-celled protozoans and protists.

Apparent marine fossil diversity during the Phanerozoic[107]

Biodiversity grew fast during the Phanerozoic (the last 540 million years), especially during the so-called Cambrian explosion-a period during which nearly every phylum of multicellular organisms first appeared. However, recent studies suggest that this diversification had started earlier, at least in the Ediacaran, and that it continued in the Ordovician. Over the next 400 million years or so, invertebrate diversity showed little overall trend and vertebrate diversity shows an overall exponential trend. This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as mass extinction events. A significant loss occurred in anamniotic limbed vertebrates when rainforests collapsed in the Carboniferous, but amniotes seem to have been little affected by this event; their diversification slowed down later, around the Asselian/ Sakmarian boundary, in the early Cisuralian (Early Permian), about 293 Ma ago. The worst was the Permian-Triassic extinction event, 251 million years ago. Vertebrates took 30 million years to recover from this event.

The most recent major mass extinction event, the Cretaceous-Paleogene extinction event, occurred 65 million years ago. This period has attracted more attention than others because it resulted in the extinction of the non-avian dinosaurs, which were represented by many lineages at the end of the Maastrichtian, just before that extinction event. However, many other taxa were affected by this crisis, which affected even marine taxa, such as ammonites, which also became extinct around that time.

The biodiversity of the past is called Paleobiodiversity. The fossil record suggests that the last few million years featured the greatest biodiversity in history. However, not all scientists support this view, since there is uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of recent geologic sections. Some scientists believe that corrected for sampling artifacts, modern biodiversity may not be much different from biodiversity 300 million years ago, whereas others consider the fossil record reasonably reflective of the diversification of life. Estimates of the present global macroscopic species diversity vary from 2 million to 100 million, with a best estimate of somewhere near 9 million, the vast majority arthropods. Diversity appears to increase continually in the absence of natural selection.

The existence of a global carrying capacity, limiting the amount of life that can live at once, is debated, as is the question of whether such a limit would also cap the number of species. While records of life in the sea show a logistic pattern of growth, life on land (insects, plants and tetrapods) shows an exponential rise in diversity. As one author states, "Tetrapods have not yet invaded 64 percent of potentially habitable modes and it could be that without human influence the ecological and taxonomic diversity of tetrapods would continue to increase exponentially until most or all of the available eco-space is filled."

It also appears that the diversity continues to increase over time, especially after mass extinctions.

On the other hand, changes through the Phanerozoic correlate much better with the hyperbolic model (widely used in population biology, demography and macrosociology, as well as fossil biodiversity) than with exponential and logistic models. The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) and/or a negative feedback arising from resource limitation. Hyperbolic model implies a second-order positive feedback. Differences in the strength of the second-order feedback due to different intensities of interspecific competition might explain the faster rediversification of ammonoids in comparison to bivalves after the end-Permian extinction. The hyperbolic pattern of the world population growth arises from a second-order positive feedback between the population size and the rate of technological growth. The hyperbolic character of biodiversity growth can be similarly accounted for by a feedback between diversity and community structure complexity. The similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the interference of the hyperbolic trend with cyclical and stochastic dynamics.

Most biologists agree however that the period since human emergence is part of a new mass extinction, named the Holocene extinction event, caused primarily by the impact humans are having on the environment. It has been argued that the present rate of extinction is sufficient to eliminate most species on the planet Earth within 100 years.

New species are regularly discovered (on average between 5-10,000 new species each year, most of them insects) and many, though discovered, are not yet classified (estimates are that nearly 90% of all arthropods are not yet classified). Most of the terrestrial diversity is found in tropical forests and in general, the land has more species than the ocean; some 8.7 million species may exist on Earth, of which some 2.1 million live in the ocean.

It is estimated that 5 to 50 billion species have existed on the planet. Assuming that there may be a maximum of about 50 million species currently alive, it stands to reason that greater than 99% of the planet's species went extinct prior to the evolution of humans. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86% have not yet been described. However, a May 2016 scientific report estimates that 1 trillion species are currently on Earth, with only one-thousandth of one percent described. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 10 ³⁷ and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as four trillion tons of carbon. In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth.

The age of Earth is about 4.54 billion years. The earliest undisputed evidence of life dates at least from 3.7 billion years ago, during the Eoarchean era after a geological crust started to solidify following the earlier molten Hadean eon. There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland.. More recently, in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, "If life arose relatively quickly on Earth...then it could be common in the universe."

Summer field in Belgium (Hamois). The blue flowers are Centaurea cyanus and the red are Papaver rhoeas.

There have been many claims about biodiversity's effect on the ecosystem services, especially provisioning and regulating services. Some of those claims have been validated, some are incorrect and some lack enough evidence to draw definitive conclusions.

Ecosystem services have been grouped in three types:

1. Provisioning services which involve the production of renewable resources (e.g.: food, wood, fresh water)

2. Regulating services which are those that lessen environmental change (e.g.: climate regulation, pest/disease control)

3. Cultural services represent human value and enjoyment (e.g.: landscape aesthetics, cultural heritage, outdoor recreation and spiritual significance)

Experiments with controlled environments have shown that humans cannot easily build ecosystems to support human needs; for example insect pollination cannot be mimicked, though there have been attempts to create artificial pollinators using unmanned aerial vehicles. The economic activity of pollination alone represented between $2.1-14.6 billion in 2003. Other sources have reported somewhat conflicting results and in 1997 Robert Costanza and his colleagues reported the estimated global value of ecosystem services (not captured in traditional markets) at an average of $33 trillion annually.

Provisioning services

With regards to provisioning services, greater species diversity has the following benefits:

Greater species diversity of plants increases fodder yield (synthesis of 271 experimental studies).

Regulating services

With regards to regulating services, greater species diversity has the following benefits:

Greater species diversity

of plants increases soil nutrient remineralization (synthesis of 103 experimental studies), increases soil organic matter (synthesis of 85 experimental studies) and decreases disease prevalence on plants (synthesis of 107 experimental studies)[151]

of natural pest enemies decreases herbivorous pest populations (data from two separate reviews; synthesis of 266 experimental and observational studies;[152] Synthesis of 18 observational studies.[153][154] Although another review of 38 experimental studies found mixed support for this claim, suggesting that in cases where mutual intraguild predation occurs, a single predatory species is often more effective[155]

Agriculture production, pictured is a tractor and a chaser bin

Agricultural diversity can be divided into two categories: intraspecific diversity, which includes the genetic variation within a single species, like the potato (Solanum tuberosum) that is composed of many different forms and types (e.g. in the U.S. they might compare russet potatoes with new potatoes or purple potatoes, all different, but all part of the same species, S. tuberosum). The other category of agricultural diversity is called interspecific diversity and refers to the number and types of different species.

Agricultural diversity can also be divided by whether it is 'planned' diversity or 'associated' diversity. This is a functional classification that we impose and not an intrinsic feature of life or diversity. Planned diversity includes the crops which a farmer has encouraged, planted or raised (e.g. crops, covers, symbionts, and livestock, among others), which can be contrasted with the associated diversity that arrives among the crops, uninvited (e.g. herbivores, weed species and pathogens, among others).

Associated biodiversity can be damaging or beneficial. The beneficial associated biodiversity include for instance wild pollinators such as wild bees and syrphid flies that pollinate crops and natural enemies and antagonists to pests and pathogens. Beneficial associated biodiversity occurs abundantly in crop fields and provide multiple ecosystem services such as pest control, nutrient cycling and pollination that support crop production.

The diverse forest canopy on Barro Colorado Island, Panama, yielded this display of different fruit

Biodiversity's relevance to human health is becoming an international political issue, as scientific evidence builds on the global health implications of biodiversity loss. This issue is closely linked with the issue of climate change, as many of the anticipated health risks of climate change are associated with changes in biodiversity (e.g. changes in populations and distribution of disease vectors, scarcity of fresh water, impacts on agricultural biodiversity and food resources etc.). This is because the species most likely to disappear are those that buffer against infectious disease transmission, while surviving species tend to be the ones that increase disease transmission, such as that of West Nile Virus, Lyme disease and Hantavirus, according to a study done co-authored by Felicia Keesing, an ecologist at Bard College and Drew Harvell, associate director for Environment of the Atkinson Center for a Sustainable Future (ACSF) at Cornell University.

Biodiversity provides critical support for drug discovery and the availability of medicinal resources. A significant proportion of drugs are derived, directly or indirectly, from biological sources: at least 50% of the pharmaceutical compounds on the US market are derived from plants, animals and microorganisms, while about 80% of the world population depends on medicines from nature (used in either modern or traditional medical practice) for primary healthcare. Only a tiny fraction of wild species has been investigated for medical potential.

Marine ecosystems are particularly important, although inappropriate bioprospecting can increase biodiversity loss, as well as violating the laws of the communities and states from which the resources are taken.

Many industrial materials derive directly from biological sources. These include building materials, fibers, dyes, rubber, and oil. Biodiversity is also important to the security of resources such as water, timber, paper, fiber, and food. As a result, biodiversity loss is a significant risk factor in business development and a threat to long-term economic sustainability.

Eagle Creek, Oregon hiking

Philosophically it could be argued that biodiversity has intrinsic aesthetic and spiritual value to mankind in and of itself. This idea can be used as a counterweight to the notion that tropical forests and other ecological realms are only worthy of conservation because of the services they provide.

Biodiversity also affords many non-material benefits including spiritual and aesthetic values, knowledge systems and education.

Less than 1% of all species that have been described have been studied beyond noting their existence. The vast majority of Earth's species are microbial. Contemporary biodiversity physics is "firmly fixated on the visible [macroscopic] world". For example, microbial life is metabolically and environmentally more diverse than multicellular life (see e.g., extremophile). "On the tree of life, based on analyses of small-subunit ribosomal RNA, visible life consists of barely noticeable twigs. The inverse relationship of size and population recurs higher on the evolutionary ladder-to a first approximation, all multicellular species on Earth are insects". Insect extinction rates are high-supporting the Holocene extinction hypothesis.

Biodiversity changes (other than losses)

Biodiversity naturally varies due to seasonal shifts. Spring's arrival enhances biodiversity as numerous species breed and feed, while winter's onset temporarily reduces it as some insects perish and migrating animals leave. Additionally, the seasonal fluctuation in plant and invertebrate populations influences biodiversity.

Male Lophura nycthemera (silver pheasant), a native of East Asia that has been introduced into parts of Europe for ornamental reasons

Barriers such as large rivers, seas, oceans, mountains and deserts encourage diversity by enabling independent evolution on either side of the barrier, via the process of allopatric speciation. The term invasive species is applied to species that breach the natural barriers that would normally keep them constrained. Without barriers, such species occupy new territory, often supplanting native species by occupying their niches, or by using resources that would normally sustain native species.

Species are increasingly being moved by humans (on purpose and accidentally). Some studies say that diverse ecosystems are more resilient and resist invasive plants and animals. Many studies cite effects of invasive species on natives, but not extinctions.

Invasive species seem to increase local ( alpha diversity) diversity, which decreases turnover of diversity (i beta diversity). Overall gamma diversity may be lowered because species are going extinct because of other causes, but even some of the most insidious invaders (e.g.: Dutch elm disease, emerald ash borer, chestnut blight in North America) have not caused their host species to become extinct. Extirpation, population decline and homogenization of regional biodiversity are much more common. Human activities have frequently been the cause of invasive species circumventing their barriers, by introducing them for food and other purposes. Human activities therefore allow species to migrate to new areas (and thus become invasive) occurred on time scales much shorter than historically have been required for a species to extend its range.

At present, several countries have already imported so many exotic species, particularly agricultural and ornamental plants, that their indigenous fauna/flora may be outnumbered. For example, the introduction of kudzu from Southeast Asia to Canada and the United States has threatened biodiversity in certain areas. Another example are pines, which have invaded forests, shrublands and grasslands in the southern hemisphere.

The Yecoro wheat (right) cultivar is sensitive to salinity, plants resulting from a hybrid cross with cultivar W4910 (left) show greater tolerance to high salinity

Endemic species can be threatened with extinction through the process of genetic pollution, i.e. uncontrolled hybridization, introgression and genetic swamping. Genetic pollution leads to homogenization or replacement of local genomes as a result of either a numerical and/or fitness advantage of an introduced species.

Hybridization and introgression are side-effects of introduction and invasion. These phenomena can be especially detrimental to rare species that come into contact with more abundant ones. The abundant species can interbreed with the rare species, swamping its gene pool. This problem is not always apparent from morphological (outward appearance) observations alone. Some degree of gene flow is normal adaptation and not all gene and genotype constellations can be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.

A schematic image illustrating the relationship between biodiversity, ecosystem services, human well-being and poverty.[202] The illustration shows where conservation action, strategies, and plans can influence the drivers of the current biodiversity crisis at local, regional, to global scales.

Conservation biology matured in the mid-20th century as ecologists, naturalists and other scientists began to research and address issues pertaining to global biodiversity declines.

The conservation ethic advocates management of natural resources for the purpose of sustaining biodiversity in species, ecosystems, the evolutionary process and human culture and society.

Conservation biology is reforming around strategic plans to protect biodiversity. Preserving global biodiversity is a priority in strategic conservation plans that are designed to engage public policy and concerns affecting local, regional and global scales of communities, ecosystems and cultures. Action plans identify ways of sustaining human well-being, employing natural capital, market capital and ecosystem services.

In the EU Directive 1999/22/EC zoos are described as having a role in the preservation of the biodiversity of wildlife animals by conducting research or participation in breeding programs.

Removal of exotic species will allow the species that they have negatively impacted to recover their ecological niches. Exotic species that have become pests can be identified taxonomically (e.g., with Digital Automated Identification SYstem (DAISY), using the barcode of life). Removal is practical only given large groups of individuals due to the economic cost.

As sustainable populations of the remaining native species in an area become assured, "missing" species that are candidates for reintroduction can be identified using databases such as the Encyclopedia of Life and the Global Biodiversity Information Facility.

Mother and child at an orangutan rehab facility in Malaysia

Protected areas, including forest reserves and biosphere reserves, serve many functions including for affording protection to wild animals and their habitat. Protected areas have been set up all over the world with the specific aim of protecting and conserving plants and animals. Some scientists have called on the global community to designate as protected areas of 30 percent of the planet by 2030, and 50 percent by 2050, in order to mitigate biodiversity loss from anthropogenic causes. The target of protecting 30% of the area of the planet by the year 2030 ( 30 by 30) was adopted by almost 200 countries in the 2022 United Nations Biodiversity Conference. At the moment of adoption (December 2022) 17% of land territory and 10% of ocean territory were protected. In a study published 4 September 2020 in Science Advances researchers mapped out regions that can help meet critical conservation and climate goals.

Protected areas safeguard nature and cultural resources and contribute to livelihoods, particularly at local level. There are over 238 563 designated protected areas worldwide, equivalent to 14.9 percent of the earth's land surface, varying in their extension, level of protection, and type of management (IUCN, 2018).

The benefits of protected areas extend beyond their immediate environment and time. In addition to conserving nature, protected areas are crucial for securing the long-term delivery of ecosystem services. They provide numerous benefits including the conservation of genetic resources for food and agriculture, the provision of medicine and health benefits, the provision of water, recreation and tourism, and for acting as a buffer against disaster. Increasingly, there is acknowledgement of the wider socioeconomic values of these natural ecosystems and of the ecosystem services they can provide.

A national park is a large natural or near natural area set aside to protect large-scale ecological processes, which also provide a foundation for environmentally and culturally compatible, spiritual, scientific, educational, recreational and visitor opportunities. These areas are selected by governments or private organizations to protect natural biodiversity along with its underlying ecological structure and supporting environmental processes, and to promote education and recreation. The International Union for Conservation of Nature (IUCN), and its World Commission on Protected Areas (WCPA), has defined "National Park" as its Category II type of protected areas. Wildlife sanctuaries aim only at the conservation of species

Percentage of forest in legally protected areas (as of 2020).[78]

There is an estimated 726 million ha of forest in protected areas worldwide. Of the six major world regions, South America has the highest share of forests in protected areas, 31 percent. The forests play a vital role in harboring more than 45,000 floral and 81,000 faunal species of which 5150 floral and 1837 faunal species are endemic. In addition, there are 60,065 different tree species in the world. Plant and animal species confined to a specific geographical area are called endemic species.

In forest reserves, rights to activities like hunting and grazing are sometimes given to communities living on the fringes of the forest, who sustain their livelihood partially or wholly from forest resources or products.

Approximately 50 million hectares (or 24%) of European forest land is protected for biodiversity and landscape protection. Forests allocated for soil, water, and other ecosystem services encompass around 72 million hectares (32% of European forest area).

In 2019, a summary for policymakers of the largest, most comprehensive study to date of biodiversity and ecosystem services, the Global Assessment Report on Biodiversity and Ecosystem Services, was published by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). It stated that "the state of nature has deteriorated at an unprecedented and accelerating rate". To fix the problem, humanity will need a transformative change, including sustainable agriculture, reductions in consumption and waste, fishing quotas and collaborative water management.

The concept of nature-positive is playing a role in mainstreaming the goals of the Global Biodiversity Framework (GBF) for biodiversity. The aim of mainstreaming is to embed biodiversity considerations into public and private practice to conserve and sustainably use biodiversity on global and local levels. The concept of nature-positive refers to the societal goal to halt and reverse biodiversity loss, measured from a baseline of 2020 levels, and to achieve full so-called "nature recovery" by 2050.

Citizen science, also known as public participation in scientific research, has been widely used in environmental sciences and is particularly popular in a biodiversity-related context. It has been used to enable scientists to involve the general public in biodiversity research, thereby enabling the scientists to collect data that they would otherwise not have been able to obtain.

Volunteer observers have made significant contributions to on-the-ground knowledge about biodiversity, and recent improvements in technology have helped increase the flow and quality of occurrences from citizen sources. A 2016 study published in Biological Conservation registers the massive contributions that citizen scientists already make to data mediated by the Global Biodiversity Information Facility (GBIF). Despite some limitations of the dataset-level analysis, it is clear that nearly half of all occurrence records shared through the GBIF network come from datasets with significant volunteer contributions. Recording and sharing observations are enabled by several global-scale platforms, including iNaturalist and eBird.

A great deal of work is occurring to preserve the natural characteristics of Hopetoun Falls, Australia while continuing to allow visitor access.

Global agreements such as the Convention on Biological Diversity, give "sovereign national rights over biological resources" (not property). The agreements commit countries to "conserve biodiversity", "develop resources for sustainability" and "share the benefits" resulting from their use. Biodiverse countries that allow bioprospecting or collection of natural products, expect a share of the benefits rather than allowing the individual or institution that discovers/exploits the resource to capture them privately. Bioprospecting can become a type of biopiracy when such principles are not respected.

Sovereignty principles can rely upon what is better known as Access and Benefit Sharing Agreements (ABAs). The Convention on Biodiversity implies informed consent between the source country and the collector, to establish which resource will be used and for what and to settle on a fair agreement on benefit sharing.

On the 19 of December 2022, during the 2022 United Nations Biodiversity Conference every country on earth, with the exception of the United States and the Holy See, signed onto the agreement which includes protecting 30% of land and oceans by 2030 ( 30 by 30) and 22 other targets intended to reduce biodiversity loss. The agreement includes also recovering 30% of earth degraded ecosystems and increasing funding for biodiversity issues.

European Union

In May 2020, the European Union published its Biodiversity Strategy for 2030. The biodiversity strategy is an essential part of the climate change mitigation strategy of the European Union. From the 25% of the European budget that will go to fight climate change, large part will go to restore biodiversity and nature based solutions.

The EU Biodiversity Strategy for 2030 include the next targets:

Protect 30% of the sea territory and 30% of the land territory especially Old-growth forests.

Plant 3 billion trees by 2030.

Restore at least 25,000 kilometers of rivers, so they will become free flowing.

Reduce the use of Pesticides by 50% by 2030.

Increase Organic farming. In linked EU program From Farm to Fork it is said, that the target is making 25% of EU agriculture organic, by 2030.

Increase biodiversity in agriculture.

Give €20 billion per year to the issue and make it part of the business practice.

Approximately half of the global GDP depend on nature. In Europe many parts of the economy that generate trillions of euros per year depend on nature. The benefits of Natura 2000 alone in Europe are €200 - €300 billion per year.

Biodiversity is taken into account in some political and judicial decisions:

The relationship between law and ecosystems is very ancient and has consequences for biodiversity. It is related to private and public property rights. It can define protection for threatened ecosystems, but also some rights and duties (for example, fishing and hunting rights).[citation needed ]

Law regarding species is more recent. It defines species that must be protected because they may be threatened by extinction. The U.S. Endangered Species Act is an example of an attempt to address the "law and species" issue.

Laws regarding gene pools are only about a century old. Domestication and plant breeding methods are not new, but advances in genetic engineering have led to tighter laws covering distribution of genetically modified organisms, gene patents and process patents. Governments struggle to decide whether to focus on for example, genes, genomes, or organisms and species.[citation needed ]

Uniform approval for use of biodiversity as a legal standard has not been achieved, however. Bosselman argues that biodiversity should not be used as a legal standard, claiming that the remaining areas of scientific uncertainty cause unacceptable administrative waste and increase litigation without promoting preservation goals.

India passed the Biological Diversity Act in 2002 for the conservation of biological diversity in India. The Act also provides mechanisms for equitable sharing of benefits from the use of traditional biological resources and knowledge.

1916 - The term biological diversity was used first by J. Arthur Harris in "The Variable Desert", Scientific American: "The bare statement that the region contains a flora rich in genera and species and of diverse geographic origin or affinity is entirely inadequate as a description of its real biological diversity."

1974 - The term natural diversity was introduced by John Terborgh.

1980 - Thomas Lovejoy introduced the term biological diversity to the scientific community in a book. It rapidly became commonly used.

1985 - According to Edward O. Wilson, the contracted form biodiversity was coined by W. G. Rosen: "The National Forum on BioDiversity ... was conceived by Walter G.Rosen ... Dr. Rosen represented the NRC/NAS throughout the planning stages of the project. Furthermore, he introduced the term biodiversity".

1988 - The term biodiversity first appeared in publication.

1988 to Present - The United Nations Environment Programme (UNEP) Ad Hoc Working Group of Experts on Biological Diversity in began working in November 1988, leading to the publication of the draft Convention on Biological Diversity in May 1992. Since this time, there have been 15 Conferences of the Parties (COPs) to discuss potential global political responses to biodiversity loss. Most recently COP 15 in Montreal, Canada in 2022.

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Biodiversity (or biological diversity) is the variety and variability of life on Earth. It can be measured on various levels. There is for example genetic variability , species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth.

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Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord. This includes all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods ( insects, arachnids, crustaceans, and myriapods), mollusks ( chitons, snails, bivalves, squids, and octopuses), annelid ( earthworms and leeches), and cnidarians ( hydras, jellyfishes, sea anemones, and corals).

The majority of animal species are invertebrates; one estimate puts the figure at 97%. Many invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata. Invertebrates vary widely in size, from 50 μm (0.002 in) rotifers to the 9-10 m (30-33 ft) colossal squid.

Some so-called invertebrates, such as the Tunicata and Cephalochordata, are more closely related to vertebrates than to other invertebrates. This makes the invertebrates paraphyletic, so the term has little meaning in taxonomy.

The word "invertebrate" comes from the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. The jointed aspect of vertebra is derived from the concept of turning, expressed in the root verto or vorto, to turn. The prefix in- means "not" or "without".

Taxonomic significance

The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the same way that Arthropoda, Vertebrata or Manidae do. Each of these terms describes a valid taxon, phylum, subphylum or family. "Invertebrata" is a term of convenience, not a taxon; it has very little circumscriptional significance except within the Chordata. The Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of "Vertebrata" and "Invertebrata" has limited practicality. In the more formal taxonomy of Animalia other attributes that logically should precede the presence or absence of the vertebral column in constructing a cladogram, for example, the presence of a notochord. That would at least circumscribe the Chordata. However, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan.

Despite this, the concept of invertebrates as a taxon of animals has persisted for over a century among the laity, and within the zoological community and in its literature it remains in use as a term of convenience for animals that are not members of the Vertebrata. The following text reflects earlier scientific understanding of the term and of those animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone, either internal or external. They include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms. Others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca and Arthropoda. Arthropoda include insects, crustaceans and arachnids.

Number of extant species

By far the largest number of described invertebrate species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species

The IUCN estimates that 66,178 extant vertebrate species have been described, which means that over 95% of the described animal species in the world are invertebrates.

Characteristics

The trait that is common to all invertebrates is the absence of a vertebral column (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically homologous trait, any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unites tortoises, snails and sponges. Being animals, invertebrates are heterotrophs, and require sustenance in the form of the consumption of other organisms. With a few exceptions, such as the Porifera, invertebrates generally have bodies composed of differentiated tissues. There is also typically a digestive chamber with one or two openings to the exterior.

Morphology and symmetry

The body plans of most multicellular organisms exhibit some form of symmetry, whether radial, bilateral, or spherical. A minority, however, exhibit no symmetry. One example of asymmetric invertebrates includes all gastropod species. This is easily seen in snails and sea snails, which have helical shells. Slugs appear externally symmetrical, but their pneumostome (breathing hole) is located on the right side. Other gastropods develop external asymmetry, such as Glaucus atlanticus that develops asymmetrical cerata as they mature. The origin of gastropod asymmetry is a subject of scientific debate.

Other examples of asymmetry are found in fiddler crabs and hermit crabs. They often have one claw much larger than the other. If a male fiddler loses its large claw, it will grow another on the opposite side after moulting. Sessile animals such as sponges are asymmetrical alongside coral colonies (with the exception of the individual polyps that exhibit radial symmetry); alpheidae claws that lack pincers; and some copepods, polyopisthocotyleans, and monogeneans which parasitize by attachment or residency within the gill chamber of their fish hosts).

Nervous system

Neurons differ in invertebrates from mammalian cells. Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal leech, Hirudo medicinalis.

Learning and memory using nociceptors in the sea hare, has been described. Mollusk neurons are able to detect increasing pressures and tissue trauma.

Neurons have been identified in a wide range of invertebrate species, including annelids, molluscs, nematodes and arthropods.

Respiratory system

One type of invertebrate respiratory system is the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues. The distribution of spiracles can vary greatly among the many orders of insects, but in general each segment of the body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular exoskeleton that branch ( anastomose) throughout the body with diameters from only a few micrometres up to 0.8 mm. The smallest tubes, tracheoles, penetrate cells and serve as sites of diffusion for water, oxygen, and carbon dioxide. Gas may be conducted through the respiratory system by means of active ventilation or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their haemolymph.

A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices. In the head, thorax, or abdomen, tracheae may also be connected to air sacs. Many insects, such as grasshoppers and bees, which actively pump the air sacs in their abdomen, are able to control the flow of air through their body. In some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a gill, or function essentially as normal, via a plastron. Note that despite being internal, the tracheae of arthropods are shed during moulting ( ecdysis).

Reproduction

Like vertebrates, most invertebrates reproduce at least partly through sexual reproduction. They produce specialized reproductive cells that undergo meiosis to produce smaller, motile spermatozoa or larger, non-motile ova. These fuse to form zygotes, which develop into new individuals. Others are capable of asexual reproduction, or sometimes, both methods of reproduction.

Social interaction

Social behavior is widespread in invertebrates, including cockroaches, termites, aphids, thrips, ants, bees, Passalidae, Acari, spiders, and more. Social interaction is particularly salient in eusocial species but applies to other invertebrates as well.

The term invertebrates covers several phyla. One of these are the sponges ( Porifera). They were long thought to have diverged from other animals early. They lack the complex organization found in most other phyla. Their cells are differentiated, but in most cases not organized into distinct tissues. Sponges typically feed by drawing in water through pores. Some speculate that sponges are not so primitive, but may instead be secondarily simplified. The Ctenophora and the Cnidaria, which includes sea anemones, corals, and jellyfish, are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus. Both have distinct tissues, but they are not organized into organs. There are only two main germ layers, the ectoderm and endoderm, with only scattered cells between them. As such, they are sometimes called diploblastic.

The Echinodermata are radially symmetric and exclusively marine, including starfish (Asteroidea), sea urchins, (Echinoidea), brittle stars (Ophiuroidea), sea cucumbers (Holothuroidea) and feather stars (Crinoidea).

The largest animal phylum is also included within invertebrates: the Arthropoda, including insects, spiders, crabs, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. In addition, they possess a hardened exoskeleton that is periodically shed during growth. Two smaller phyla, the Onychophora and Tardigrada, are close relatives of the arthropods and share these traits. The Nematoda or roundworms, are perhaps the second largest animal phylum, and are also invertebrates. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the Kinorhyncha, Priapulida, and Loricifera. These groups have a reduced coelom, called a pseudocoelom. Other invertebrates include the Nemertea or ribbon worms, and the Sipuncula.

Another phylum is Platyhelminthes, the flatworms. These were originally considered primitive, but it now appears they developed from more complex ancestors. Flatworms are acoelomates, lacking a body cavity, as are their closest relatives, the microscopic Gastrotricha. The Rotifera or rotifers, are common in aqueous environments. Invertebrates also include the Acanthocephala or spiny-headed worms, the Gnathostomulida, Micrognathozoa, and the Cycliophora.

Also included are two of the most successful animal phyla, the Mollusca and Annelida. The former, which is the second-largest animal phylum by number of described species, includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such as earthworms and leeches. These two groups have long been considered close relatives because of the common presence of trochophore larvae, but the annelids were considered closer to the arthropods because they are both segmented. Now, this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla.

Among lesser phyla of invertebrates are the Hemichordata, or acorn worms, and the Chaetognatha, or arrow worms. Other phyla include Acoelomorpha, Brachiopoda, Bryozoa, Entoprocta, Phoronida, and Xenoturbellida.

Classification of invertebrates

Invertebrates can be classified into several main categories, some of which are taxonomically obsolescent or debatable, but still used as terms of convenience. Each however appears in its own article at the following links.

The earliest animal fossils appear to be those of invertebrates. 665-million-year-old fossils in the Trezona Formation at Trezona Bore, West Central Flinders, South Australia have been interpreted as being early sponges. Some paleontologists suggest that animals appeared much earlier, possibly as early as 1 billion years ago though they probably became multicellular in the Tonian. Trace fossils such as tracks and burrows found in the late Neoproterozoic era indicate the presence of triploblastic worms, roughly as large (about 5 mm wide) and complex as earthworms.

Around 453 MYA, animals began diversifying, and many of the important groups of invertebrates diverged from one another. Fossils of invertebrates are found in various types of sediment from the Phanerozoic. Fossils of invertebrates are commonly used in stratigraphy.

Classification

Carl Linnaeus divided these animals into only two groups, the Insecta and the now-obsolete Vermes ( worms). Jean-Baptiste Lamarck, who was appointed to the position of "Curator of Insecta and Vermes" at the Muséum National d'Histoire Naturelle in 1793, both coined the term "invertebrate" to describe such animals and divided the original two groups into ten, by splitting Arachnida and Crustacea from the Linnean Insecta, and Mollusca, Annelida, Cirripedia, Radiata, Coelenterata and Infusoria from the Linnean Vermes. They are now classified into over 30 phyla, from simple organisms such as sea sponges and flatworms to complex animals such as arthropods and molluscs.

Significance of the group

Invertebrates are animals without a vertebral column. This has led to the conclusion that invertebrates are a group that deviates from the normal, vertebrates. This has been said to be because researchers in the past, such as Lamarck, viewed vertebrates as a "standard": in Lamarck's theory of evolution, he believed that characteristics acquired through the evolutionary process involved not only survival, but also progression toward a "higher form", to which humans and vertebrates were closer than invertebrates were. Although goal-directed evolution has been abandoned, the distinction of invertebrates and vertebrates persists to this day, even though the grouping has been noted to be "hardly natural or even very sharp." Another reason cited for this continued distinction is that Lamarck created a precedent through his classifications which is now difficult to escape from. It is also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates. In any event, in the 1968 edition of Invertebrate Zoology, it is noted that "division of the Animal Kingdom into vertebrates and invertebrates is artificial and reflects human bias in favor of man's own relatives." The book also points out that the group lumps a vast number of species together, so that no one characteristic describes all invertebrates. In addition, some species included are only remotely related to one another, with some more related to vertebrates than other invertebrates (see Paraphyly).

In research

For many centuries, invertebrates were neglected by biologists, in favor of big vertebrates and "useful" or charismatic species. Invertebrate biology was not a major field of study until the work of Linnaeus and Lamarck in the 18th century. During the 20th century, invertebrate zoology became one of the major fields of natural sciences, with prominent discoveries in the fields of medicine, genetics, palaeontology, and ecology. The study of invertebrates has also benefited law enforcement, as arthropods, and especially insects, were discovered to be a source of information for forensic investigators.

Two of the most commonly studied model organisms nowadays are invertebrates: the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans. They have long been the most intensively studied model organisms, and were among the first life-forms to be genetically sequenced. This was facilitated by the severely reduced state of their genomes, but many genes, introns, and linkages have been lost. Analysis of the starlet sea anemone genome has emphasised the importance of sponges, placozoans, and choanoflagellates, also being sequenced, in explaining the arrival of 1500 ancestral genes unique to animals. Invertebrates are also used by scientists in the field of aquatic biomonitoring to evaluate the effects of water pollution and climate change.

References

Further reading

Hyman, L. H. 1940. The Invertebrates (6 volumes) New York : McGraw-Hill. A classic work.

Anderson, D. T. (Ed.). (2001). Invertebrate zoology (2nd ed.). Oxford: Oxford University Press.

Brusca, R. C., & Brusca, G. J. (2003). Invertebrates (2nd ed.). Sunderland, Mass. : Sinauer Associates.

Miller, S.A., & Harley, J.P. (1996). Zoology (4th ed.). Boston: WCB/McGraw-Hill.

Pechenik, Jan A. (2005). Biology of the invertebrates. Boston: McGraw-Hill, Higher Education. pp. 590 pp. ISBN 978-0-07-234899-6.

Ruppert, E. E., Fox, R. S., & Barnes, R. D. (2004). Invertebrate zoology: a functional evolutionary approach. Belmont, CA: Thomas-Brooks/Cole.

Adiyodi, K.G. & Adyiodi, R.G. (Eds) 1983- . Reproductive Biology of Invertebrates. Wiley, New York. (Many volumes.)

Giese, A.G. & Pearse, J.S. (Eds) 1974- . Reproduction of Marine Invertebrates. Academic Press, New York. (Many volumes.)

Advances in Invertebrate Reproduction. Elsevier Science, Amsterdam. (Five volumes.)

External links

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Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord. This includes all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods ( insects, arachnids, crustaceans, and myriapods), mollusks ( chitons, snails, bivalves, squids, and octopuses), annelid ( earthworms and leeches), and cnidarians ( hydras, jellyfishes, sea anemones, and corals).

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Vertebrates () are deuterostomal animals with bony or cartilaginous axial endoskeleton - known as the vertebral column, spine or backbone - around and along the spinal cord, including all fish, amphibians, reptiles, birds and mammals. The vertebrates consist of all the taxa within the subphylum Vertebrata () ( chordates with backbones) and represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following:

Extant vertebrates range in length from the frog species Paedophryne amauensis, at as little as 7.7 mm (0.30 in), to the blue whale, at up to 33 m (108 ft). Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns.

The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, the lampreys, do. Hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as " Craniata" when discussing morphology. Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of craniata.

The word vertebrate derives from the Latin word vertebratus ( Pliny), meaning joint of the spine. A similarly derived word is , which refers to any of the irregular bones or segments of the spinal column.

All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal (vertebral column and/or notochord), with a hollow tube of nervous tissue (the spinal cord) above it and the gastrointestinal tract below.

In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body. The remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut.

Fossilized skeleton (cast) of Diplodocus carnegii, showing an extreme example of the backbone that characterizes the vertebrates.

With only one exception, the defining characteristic of a vertebrate is the vertebral column, in which the embryonic notochord found in all chordates is replaced by a segmented series of mineralized elements called vertebrae separated by fibrocartilaginous intervertebral discs, which are derived embryonically and evolutionarily from the notochord. Hagfish are the only extant vertebrate whose notochord is not integrated into the vertebral column.

A few vertebrates have secondarily lost this feature and retain the notochord into adulthood, such as the sturgeon and coelacanth. Jawed vertebrates are typified by paired appendages ( fins or limbs, which may be secondarily lost), but this trait is not required to qualify an animal as a vertebrate.

Gill arches bearing gills in a pike

All basal vertebrates are aquatic and breathe with gills. The gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilaginous or bony gill arch. The bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their chordate relatives have more than 50 pairs of gills. In jawed vertebrates, the first gill arch pair evolved into the jointed jaws and form an additional oral cavity ahead of the pharynx.

In amphibians and some primitive bony fishes, the larvae bear external gills, branching off from the gill arches. These are reduced in adulthood, their function taken over by the gills proper in fishes and by lungs in most amphibians. Some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods.

While the more derived vertebrates lack gills, the gill arches form during fetal development, and form the basis of essential structures such as jaws, the thyroid gland, the larynx, the columella (corresponding to the stapes in mammals) and, in mammals, the malleus and incus.

The central nervous system of vertebrates is based on the hollow dorsal nerve cord running along the dorsal aspect of the notochord. Of particular importance and unique to vertebrates is the presence of neural crest cells, which are progenitor cells critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the nerve cord during development, and initiate the formation of neural ganglia and structures such as the jaws and skull. The peripheral nervous system forms when neural crest cells branch out laterally from the dorsal nerve cord and migrate together with the mesodermal somites to innervate the various different structures that develop in the body.

The vertebrates are the only chordate group with neural cephalization, and their neural functions are centralized towards a series of vesicular enlargements in the head, which give rise to a brain. A slight swelling of the anterior end of the nerve cord is found in invertebrate chordates such as lancelets (a sister subphylum known as the cephalochordates), though it lacks eyes and other complex special sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalization.

The rostral end of the neural tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles: the prosencephalon ( forebrain), mesencephalon ( midbrain) and rhombencephalon ( hindbrain), which are further differentiated in the various vertebrate groups. Two laterally placed retinas and optical nerves form around outgrowths from the midbrain, except in hagfish, though this may be a secondary loss. The forebrain is more well-developed in most tetrapods and subdivided into the telencephalon and diencephalon, while the midbrain dominates in many fish and some salamanders. Vesicles of the brain are usually bilaterally symmetrical, giving rise to the paired cerebral hemispheres in mammals.

The resulting anatomy of the central nervous system with a single hollow nerve cord dorsal to the gut tube, headed by a series of (often paired) vesicles, is unique to vertebrates. Other invertebrates with well-developed central nervous systems such as arthropods and cephalopods, have a ventral nerve cord made of segmental ganglia on the opposite side of the gut tube, with a split brain stem circumventing the foregut around each side to form a brain on the dorsal side of the mouth.

In addition to the morphological characteristics used to define vertebrates (i.e. the presence of a notochord, the development of a vertebral column from the notochord, a dorsal nerve cord, pharyngeal gills, a post-anal tail, etc.), molecular markers known as conserved signature indels (CSIs) in protein sequences have been identified and provide distinguishing criteria for the subphylum Vertebrata. Specifically, 5 CSIs in the following proteins: protein synthesis elongation factor-2 (EF-2), eukaryotic translation initiation factor 3 (eIF3), adenosine kinase (AdK) and a protein related to ubiquitin carboxyl-terminal hydrolase are exclusively shared by all vertebrates and reliably distinguish them from all other metazoan. The CSIs in these protein sequences are predicted to have important functionality in vertebrates.

A specific relationship between Vertebrates and Tunicates is also strongly supported by two CSIs found in the proteins Rrp44 (associated with exosome complex) and serine palmitoyltransferase, that are exclusively shared by species from these two subphyla but not Cephalochordates, indicating Vertebrates are more closely related to Tunicates than Cephalochordates.

Originally, the "Notochordata hypothesis" suggested that the Cephalochordata is the sister taxon to Craniata (Vertebrata). This group, called the Notochordata, was placed as sister group to the Tunicata (Urochordata). Although this was once the leading hypothesis, studies since 2006 analyzing large sequencing datasets strongly support Olfactores (tunicates + vertebrates) as a monophyletic clade, and the placement of Cephalochordata as sister-group to Olfactores (known as the " Olfactores hypothesis"). As chordates, they all share the presence of a notochord, at least during a stage of their life cycle.

The following cladogram summarizes the systematic relationships between the Olfactores (vertebrates and tunicates) and the Cephalochordata.

The early vertebrate Haikouichthys

Vertebrates originated during the Cambrian explosion, which saw a rise in organism diversity. The earliest known vertebrates belongs to the Chengjiang biota and lived about 518 million years ago. These include Haikouichthys, Myllokunmingia, Zhongjianichthys, and probably Haikouella. Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed.[page needed ] A vertebrate group of uncertain phylogeny, small eel-like conodonts, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.

Acanthostega, a fish-like early labyrinthodont.

The first jawed vertebrates may have appeared in the late Ordovician (~445 mya) and became common in the Devonian period, often known as the "Age of Fishes". The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. The Devonian also saw the demise of virtually all jawless fishes save for lampreys and hagfish, as well as the Placodermi, a group of armoured fish that dominated the entirety of that period since the late Silurian as well as the eurypterids, dominant animals of the preceding Silurian, and the anomalocarids. By the middle of the Devonian, several droughts, anoxic events and oceanic competition lead a lineage of sarcopterygii to leave water, eventually establishing themselves as terrestrial tetrapods in the succeeding Carboniferous.

Amniotes branched from amphibious tetrapods early in the Carboniferous period. The synapsid amniotes were dominant during the late Paleozoic, the Permian, while diapsid amniotes became dominant during the Mesozoic. In the sea, the teleosts and sharks became dominant. Mesothermic synapsids called cynodonts gave rise to endothermic mammals and diapsids called dinosaurs eventually gave rise to endothermic birds, both in the Jurassic. After all dinosaurs except birds went extinct by the end of the Cretaceous, birds and mammals diversified and filled their niches.

The Cenozoic world saw great diversification of bony fishes, amphibians, reptiles, birds and mammals.

Over half of all living vertebrate species (about 32,000 species) are fish (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over 4,600 metres (15,100 feet) to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about 11,000 metres (36,000 feet). Many fish varieties are the main predators in most of the world's freshwater and marine water bodies . The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between the two classes). Tetrapods comprise the dominant megafauna of most terrestrial environments and also include many partially or fully aquatic groups (e.g., sea snakes, penguins, cetaceans).

There are several ways of classifying animals. Evolutionary systematics relies on anatomy, physiology and evolutionary history, which is determined through similarities in anatomy and, if possible, the genetics of organisms. Phylogenetic classification is based solely on phylogeny. Evolutionary systematics gives an overview; phylogenetic systematics gives detail. The two systems are thus complementary rather than opposed.

Traditional spindle diagram of the evolution of the vertebrates at class level

Conventional classification has living vertebrates grouped into seven classes based on traditional interpretations of gross anatomical and physiological traits. This classification is the one most commonly encountered in school textbooks, overviews, non-specialist, and popular works. The extant vertebrates are:

In addition to these, there are two classes of extinct armoured fishes, the Placodermi and the Acanthodii, both considered paraphyletic.

Other ways of classifying the vertebrates have been devised, particularly with emphasis on the phylogeny of early amphibians and reptiles. An example based on Janvier (1981, 1997), Shu et al. (2003), and Benton (2004) is given here († = extinct):

Diversity of various groups of vertebrates through the geologic ages. The width of the bubbles signifies the diversity (number of families).

While this traditional classification is orderly, most of the groups are paraphyletic, i.e. do not contain all descendants of the class's common ancestor. For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; the traditional " amphibians" have given rise to the reptiles (traditionally including the synapsids or mammal-like "reptiles"), which in turn have given rise to the mammals and birds. Most scientists working with vertebrates use a classification based purely on phylogeny, organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology.

In phylogenetic taxonomy, the relationships between animals are not typically divided into ranks but illustrated as a nested "family tree" known as a phylogenetic tree. The cladogram below is based on studies compiled by Philippe Janvier and others for the Tree of Life Web Project and Delsuc et al., and complemented (based on, and ). A dagger (†) denotes an extinct clade, whereas all other clades have living descendants.

Note that, as shown in the cladogram above, the †" Ostracodermi" (armoured jawless fishes) and †" Placodermi" (armoured jawed fishes) are shown to be paraphylectic groups, separated from Gnathostomes and Eugnathostomes respectively.

Also note that Teleostei ( Neopterygii) and Tetrapoda ( amphibians, mammals, reptiles, birds) each make up about 50% of today's vertebrate diversity, while all other groups are either extinct or rare. The next cladogram shows the extant clades of tetrapods (the four-limbed vertebrates), and a selection of extinct (†) groups:

Note that reptile-like amphibians, mammal-like reptiles, and non-avian dinosaurs are all paraphyletic.

The placement of hagfish on the vertebrate tree of life has been controversial. Their lack of proper vertebrae (among with other characteristics found in lampreys and jawed vertebrates) led phylogenetic analyses based on morphology to place them outside Vertebrata. Molecular data, however, indicates they are vertebrates closely related to lampreys. A study by Miyashita et al. (2019), 'reconciliated' the two types of analysis as it supports the Cyclostomata hypothesis using only morphological data.

The number of described vertebrate species are split between tetrapods and fish. The following table lists the number of described extant species for each vertebrate class as estimated in the IUCN Red List of Threatened Species, 2014.3.

The IUCN estimates that 1,305,075 extant invertebrate species have been described, which means that less than 5% of the described animal species in the world are vertebrates.

The following databases maintain (more or less) up-to-date lists of vertebrate species:

Nearly all vertebrates undergo sexual reproduction. They produce haploid gametes by meiosis. The smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse by the process of fertilisation to form diploid zygotes, which develop into new individuals.

During sexual reproduction, mating with a close relative ( inbreeding) often leads to inbreeding depression. Inbreeding depression is considered to be largely due to expression of deleterious recessive mutations. The effects of inbreeding have been studied in many vertebrate species.

In several species of fish, inbreeding was found to decrease reproductive success.

Inbreeding was observed to increase juvenile mortality in 11 small animal species.

A common breeding practice for pet dogs is mating between close relatives (e.g. between half- and full siblings). This practice generally has a negative effect on measures of reproductive success, including decreased litter size and puppy survival.

Incestuous matings in birds result in severe fitness costs due to inbreeding depression (e.g. reduction in hatchability of eggs and reduced progeny survival).

Inbreeding avoidance

As a result of the negative fitness consequences of inbreeding, vertebrate species have evolved mechanisms to avoid inbreeding.

Numerous inbreeding avoidance mechanisms operating prior to mating have been described. Toads and many other amphibians display breeding site fidelity. Individuals that return to natal ponds to breed will likely encounter siblings as potential mates. Although incest is possible, Bufo americanus siblings rarely mate. These toads likely recognize and actively avoid close kin as mates. Advertisement vocalizations by males appear to serve as cues by which females recognize their kin.

Inbreeding avoidance mechanisms can also operate subsequent to copulation. In guppies, a post-copulatory mechanism of inbreeding avoidance occurs based on competition between sperm of rival males for achieving fertilization. In competitions between sperm from an unrelated male and from a full sibling male, a significant bias in paternity towards the unrelated male was observed.

When female sand lizards mate with two or more males, sperm competition within the female's reproductive tract may occur. Active selection of sperm by females appears to occur in a manner that enhances female fitness. On the basis of this selective process, the sperm of males that are more distantly related to the female are preferentially used for fertilization, rather than the sperm of close relatives. This preference may enhance the fitness of progeny by reducing inbreeding depression.

Mating with unrelated or distantly related members of the same species is generally thought to provide the advantage of masking deleterious recessive mutations in progeny (see heterosis). Vertebrates have evolved numerous diverse mechanisms for avoiding close inbreeding and promoting outcrossing (see inbreeding avoidance).

Outcrossing as a way of avoiding inbreeding depression has been especially well studied in birds. For instance, inbreeding depression occurs in the great tit ( Parus major) when the offspring are produced as a result of a mating between close relatives. In natural populations of the great tit, inbreeding is avoided by dispersal of individuals from their birthplace, which reduces the chance of mating with a close relative.

Purple-crowned fairywren females paired with related males may undertake extra-pair matings that can reduce the negative effects of inbreeding, despite ecological and demographic constraints.

Southern pied babblers ( Turdoides bicolor) appear to avoid inbreeding in two ways: through dispersal and by avoiding familiar group members as mates. Although both genders disperse locally, they move outside the range where genetically related individuals are likely to be encountered. Within their group, individuals only acquire breeding positions when the opposite-sex breeder is unrelated.

Cooperative breeding in birds typically occurs when offspring, usually males, delay dispersal from their natal group in order to remain with the family to help rear younger kin. Female offspring rarely stay at home, dispersing over distances that allow them to breed independently or to join unrelated groups.

Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilization.

Reproduction in squamate reptiles is ordinarily sexual, with males having a ZZ pair of sex determining chromosomes, and females a ZW pair. However, various species, including the Colombian Rainbow boa ( Epicrates maurus), Agkistrodon contortrix (copperhead snake) and Agkistrodon piscivorus (cotton mouth snake) can also reproduce by facultative parthenogenesis-that is, they are capable of switching from a sexual mode of reproduction to an asexual mode-resulting in production of WW female progeny. The WW females are likely produced by terminal automixis.

Mole salamanders are an ancient (2.4-3.8 million year-old) unisexual vertebrate lineage. In the polyploid unisexual mole salamander females, a premeiotic endomitotic event doubles the number of chromosomes. As a result, the mature eggs produced subsequent to the two meiotic divisions have the same ploidy as the somatic cells of the female salamander. Synapsis and recombination during meiotic prophase I in these unisexual females is thought to ordinarily occur between identical sister chromosomes and occasionally between homologous chromosomes. Thus little, if any, genetic variation is produced. Recombination between homeologous chromosomes occurs only rarely, if at all. Since production of genetic variation is weak, at best, it is unlikely to provide a benefit sufficient to account for the long-term maintenance of meiosis in these organisms.

Two killifish species, the mangrove killifish ( Kryptolebias marmoratus) and Kryptolebias hermaphroditus, are the only known vertebrates to self-fertilize. They produce eggs and sperm by meiosis and routinely reproduce by self-fertilisation. This capacity has apparently persisted for at least several hundred thousand years. Each individual hermaphrodite normally fertilizes itself through uniting inside the fish's body of an egg and a sperm that it has produced by an internal organ. In nature, this mode of reproduction can yield highly homozygous lines composed of individuals so genetically uniform as to be, in effect, identical to one another. Although inbreeding, especially in the extreme form of self-fertilization, is ordinarily regarded as detrimental because it leads to expression of deleterious recessive alleles, self-fertilization does provide the benefit of fertilization assurance ( reproductive assurance) at each generation.

The Living Planet Index, following 16,704 populations of 4,005 species of vertebrates, shows a decline of 60% between 1970 and 2014. Since 1970, freshwater species declined 83%, and tropical populations in South and Central America declined 89%. The authors note that, "An average trend in population change is not an average of total numbers of animals lost." According to WWF, this could lead to a sixth major extinction event. The five main causes of biodiversity loss are land-use change, overexploitation of natural resources, climate change, pollution and invasive species.

1. Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659-666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168. Archived (PDF) from the original on 9 October 2022.

2. ^ "vertebrate". Dictionary.com Unabridged (Online). n.d.

3. ^ "Vertebrata". Dictionary.com Unabridged (Online). n.d.

4. ^ "Table 1a: Number of species evaluated in relation to the overall number of described species, and numbers of threatened species by major groups of organisms". IUCN Red List. 18 July 2019.

5. ^ Ota, Kinya G.; Fujimoto, Satoko; Oisi, Yasuhiro; Kuratani, Shigeru (25 January 2017). "Identification of vertebra-like elements and their possible differentiation from sclerotomes in the hagfish". Nature Communications. 2: 373. Bibcode:2011NatCo...2..373O. doi:10.1038/ncomms1355. ISSN 2041-1723. PMC 3157150. PMID 21712821.

6. ^ "vertebrate". Online Etymology Dictionary. Dictionary.com.

7. ^ "vertebra". Online Etymology Dictionary. Dictionary.com.

8. ^ Waggoner, Ben. "Vertebrates: More on Morphology". UCMP.

9. ^ Romer, A.S. (1949): The Vertebrate Body. W.B. Saunders, Philadelphia. (2nd ed. 1955; 3rd ed. 1962; 4th ed. 1970)

10. ^ Liem, K. F.; Walker, W. F. (2001). Functional anatomy of the vertebrates: an evolutionary perspective. Harcourt College Publishers. p. 277. ISBN 978-0-03-022369-3.

11. ^ Scott, T. (1996). Concise encyclopedia biology. Walter de Gruyter. p. 542. ISBN 978-3-11-010661-9.

12. Clack, J. A. (2002): Gaining ground: the origin and evolution of tetrapods. ^ Indiana University Press, Bloomington, Indiana. 369 pp

13. ^ Teng, Lu; Labosky, Patricia A. (2006). "Neural Crest Stem Cells". Neural Crest Induction and Differentiation. Advances in Experimental Medicine and Biology. Vol. 589. pp. 206-212. doi:10.1007/978-0-387-46954-6_13. ISBN 978-0-387-35136-0. ISSN 0065-2598. PMID 17076284.

14. Dupin, E.; Creuzet, S.; Le Douarin, N.M. (2007) "The Contribution of the Neural Crest to the Vertebrate Body". In: Jean-Pierre Saint-Jeannet, ^ Neural Crest Induction and Differentiation, pp. 96-119, Springer Science & Business Media. ISBN 9780387469546. doi:10.1007/978-0-387-46954-6_6. Full text

15. Hildebrand, M.; Gonslow, G. (2001): Analysis of Vertebrate Structure. 5th edition. John Wiley & Sons, Inc. New York

16. ^ "Keeping an eye on evolution". PhysOrg.com. 3 December 2007.

17. ^ "Hyperotreti". tolweb.org.

18. ^ Gupta, Radhey S. (January 2016). "Molecular signatures that are distinctive characteristics of the vertebrates and chordates and supporting a grouping of vertebrates with the tunicates". Molecular Phylogenetics and Evolution. 94 (Pt A): 383-391. doi:10.1016/j.ympev.2015.09.019. ISSN 1055-7903. PMID 26419477.

19. ^ Stach, Thomas (2008). "Chordate phylogeny and evolution: a not so simple three‐taxon problem". Journal of Zoology. 276 (2): 117-141. doi:10.1111/j.1469-7998.2008.00497.x.

20. ^ Delsuc, F (2006). "Tunicates and not cephalochordates are the closest living relatives of vertebrates" (PDF). Nature. 439 (7079): 965-968. Bibcode:2006Natur.439..965D. doi:10.1038/nature04336. PMID 16495997. S2CID 4382758. Archived (PDF) from the original on 9 October 2022.

21. ^ Shu, D. (2003). "A paleontological perspective of vertebrate origin". Chinese Science Bulletin. 48 (8): 725-735. doi:10.1360/03wd0026.

22. ^ Waggoner, B. "Vertebrates: Fossil Record". UCMP. Archived from the original on 29 June 2011.

23. ^ Tim Haines, T.; Chambers, P. (2005). The Complete Guide to Prehistoric Life. Firefly Books.

24. ^ Encyclopædia Britannica: a new survey of universal knowledge, Volume 17. Encyclopædia Britannica. 1954. p. 107.

25. ^ Berg, L. R.; Solomon, E. P.; Martin, D. W. (2004). Biology. Cengage Learning. p. 599. ISBN 978-0-534-49276-2.

26. ^ Cloudsley-Thompson, J. L. (2005). Ecology and behaviour of Mesozoic reptiles. Springer. p. 6. ISBN 9783540224211.

27. ^ Pires, Mathias; Mankin, Brian; Silvestro, Daniele; Quental, Tiago (26 September 2018). "Diversification dynamics of mammalian clades during the K-Pg mass extinction". Biology Letters. 14 (9) - via Proceedings of the Royal Society.

28. ^ Lowery, Christopher; Fraass, Andrew (8 April 2019). "Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction". Nature Ecology & Evolution. 3: 900-904 - via Nature.

29. ^ Andersen, N. M.; Weir, T. A. (2004). Australian water bugs: their biology and identification (Hemiptera-Heteroptera, Gerromorpha & Nepomorpha). Apollo Books. p. 38. ISBN 978-87-88757-78-1.

30. Hildebran, M.; Gonslow, G. (2001): Analysis of Vertebrate Structure. 5th edition. ^ John Wiley & Sons, Inc. New York, page 33: Comment: The problem of naming sister groups

31. Benton, M.J. (1 November 2004). Vertebrate Palaeontology (Third ed.). Blackwell Publishing. pp. 33, 455 pp. ISBN 978-0632056378. Archived from the original on 19 October 2008.

32. ^ Irie, Naoki (26 December 2018). "The phylum Vertebrata: a case for zoological recognition". Zoological Letters. 4 Article Number 32: 32. doi:10.1186/s40851-018-0114-y. PMC 6307173. PMID 30607258.

33. Janvier, P. 1997. Vertebrata. Animals with backbones. Version 1 January 1997 (under construction). ^ http://tolweb.org/Vertebrata/14829/1997.01.01 in The Tree of Life Web Project, http://tolweb.org/

34. ^ Delsuc, F.; Philippe, H.; Tsagkogeorga, G.; Simion, P. (April 2018). Tilak, M. K.; Turon, X.; López-Legentil, S.; Piette, J.; Lemaire, P.; Douzery, E. J. "A phylogenomic framework and timescale for comparative studies of tunicates". BMC Biology. 16 (1): 39. doi:10.1186/s12915-018-0499-2. PMC 5899321. PMID 29653534.

35. ^ Zhu, Min; Yu, Xiaobo; Ahlberg, Per Erik; Choo, Brian; Lu, Jing; Qiao, Tuo; Qu, Qingming; Zhao, Wenjin; Jia, Liantao; Blom, Henning; Zhu, You'an (25 September 2013). "A Silurian placoderm with osteichthyan-like marginal jaw bones". Nature. 502 (7470): 188-193. Bibcode:2013Natur.502..188Z. doi:10.1038/nature12617. ISSN 0028-0836. PMID 24067611. S2CID 4462506.

36. ^ Giles, Sam; Friedman, Matt; Brazeau, Martin D. (12 January 2015). "Osteichthyan-like cranial conditions in an Early Devonian stem gnathostome". Nature. 520 (7545): 82-85. Bibcode:2015Natur.520...82G. doi:10.1038/nature14065. ISSN 1476-4687. PMC 5536226. PMID 25581798.

37. ^ Benton, Michael J. (2009). Vertebrate Palaeontology (3rd ed.). John Wiley & Sons. p. 44. ISBN 978-1-4051-4449-0.

38. ^ The World Conservation Union. 2014. IUCN Red List of Threatened Species, 2014.3. Summary Statistics for Globally Threatened Species. Table 1: Numbers of threatened species by major groups of organisms (1996-2014).

39. ^ Nelson, Joseph, S. (2016). Fishes of the World. John Wiley & Sons, Inc. ISBN 978-1-118-34233-6.

40. ^ van der Beek, S.; Nielen, A.L.; Schukken, Y.H.; Brascamp, E.W. (1999). "Evaluation of genetic, common-litter, and within-litter effects on preweaning mortality in a birth cohort of puppies". Am. J. Vet. Res. 60 (9): 1106-10. PMID 10490080.

41. ^ Gresky, C.; Hamann, H.; Distl, O. (2005). "[Influence of inbreeding on litter size and the proportion of stillborn puppies in dachshunds]". Berl. Munch. Tierarztl. Wochenschr. (in German). 118 (3-4): 134-9. PMID 15803761.

42. ^ Leroy, G.; Phocas, F.; Hedan, B.; Verrier, E.; Rognon, X. (2015). "Inbreeding impact on litter size and survival in selected canine breeds" (PDF). Vet. J. 203 (1): 74-8. doi:10.1016/j.tvjl.2014.11.008. PMID 25475165. S2CID 27631883. Archived (PDF) from the original on 9 October 2022.

43. Kingma, S. A.; Hall, M. L.; Peters, A. (2013). "Breeding synchronization facilitates extrapair mating for inbreeding avoidance". Behavioral Ecology. 24 (6): 1390-1397. doi:10.1093/beheco/art078.

44. Waldman, B.; Rice, J.E.; Honeycutt, R.L. (1992). "Kin recognition and incest avoidance in toads". Am. Zool. 32: 18-30. doi:10.1093/icb/32.1.18.

45. Fitzpatrick, J. L.; Evans, J. P. (2014). "Postcopulatory inbreeding avoidance in guppies" (PDF). J. Evol. Biol. 27 (12): 2585-94. doi:10.1111/jeb.12545. PMID 25387854. S2CID 934203. Archived (PDF) from the original on 9 October 2022.

46. ^ Kanamori, Akira; Sugita, Yosuke; Yuasa, Yasufumi; Suzuki, Takamasa; Kawamura, Kouichi; Uno, Yoshinobu; Kamimura, Katsuyasu; Matsuda, Yoichi; Wilson, Catherine A; Amores, Angel; Postlethwait, John H (1 April 2016). "A Genetic Map for the Only Self-Fertilizing Vertebrate". G3: Genes, Genomes, Genetics. 6 (4): 1095-1106. doi:10.1534/g3.115.022699. ISSN 2160-1836. PMC 4825644. PMID 26865699.

47. ^ Tatarenkov, A.; Lima, S. M.; Taylor, D. S.; Avise, J. C. (25 August 2009). "Long-term retention of self-fertilization in a fish clade". Proc. Natl. Acad. Sci. U.S.A. 106 (34): 14456-9. Bibcode:2009PNAS..10614456T. doi:10.1073/pnas.0907852106. PMC 2732792. PMID 19706532.

48. ^ Sakakura, Yoshitaka; Soyano, Kiyoshi; Noakes, David L. G.; Hagiwara, Atsushi (2006). "Gonadal morphology in the self-fertilizing mangrove killifish, Kryptolebias marmoratus". Ichthyological Research. 53 (4): 427-430. doi:10.1007/s10228-006-0362-2. hdl:10069/35713. S2CID 9474211.

49. Avise, J. C.; Tatarenkov, A. (13 November 2012). "Allard's argument versus Baker's contention for the adaptive significance of selfing in a hermaphroditic fish". Proc. Natl. Acad. Sci. U.S.A. 109 (46): 18862-7. Bibcode:2012PNAS..10918862A. doi:10.1073/pnas.1217202109. PMC 3503157. PMID 23112206.

50. ^ "Living Planet Report 2018 | WWF". wwf.panda.org.

51. Grooten, M.; Almond, R. E. A. (2018). Living Planet Report - 2018: Aiming Higher (PDF). WWF--World Wide Fund for Nature. ISBN 978-2-940529-90-2. Archived (PDF) from the original on 9 October 2022.

52. ^ "WWF Finds Human Activity Is Decimating Wildlife Populations". Time.

53. ^ Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, IPBES (25 November 2019). "Summary for policymakers of the global assessment report on biodiversity and ecosystem services". doi:10.5281/zenodo.3553579. ;

# data[].attributes.attachment_link.description
Vertebrates () are deuterostomal animals with bony or cartilaginous axial endoskeleton - known as the vertebral column, spine or backbone - around and along the spinal cord, including all fish, amphibians, reptiles, birds and mammals.

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One animal mentioned is not a vertebrate

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One animal mentioned is not a vertebrate

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Two Large Groups (Invertebrates and Vertebrates)

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Two Large Groups (Invertebrates and Vertebrates)