Vertebrate

Last updated

Vertebrate
Temporal range:
Cambrian Present, [1] 520–0  Ma [2]
Vertebrata 002.png
Example of vertebrates: a Siberian tiger (Tetrapoda), an Australian Lungfish (Osteichthyes), a Tiger shark (Chondrichthyes) and a River lamprey (Agnatha).
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Olfactores
Subphylum: Vertebrata
J-B. Lamarck, 1801 [3]
Simplified grouping (see text)
Synonyms

Ossea Batsch, 1788 [3]

Vertebrates ( /ˈvɜːrtəˌbrəts/ ) comprise all species of animals within the subphylum Vertebrata ( /-ə/ ) (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. [4] Vertebrates include such groups as the following:

Contents

Extant vertebrates range in size 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, [5] though their closest living relatives, the lampreys, do. [6] 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, [7] and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of craniata. [8]

The populations of vertebrates have dropped in the past 50 years [9] .

Etymology

The word vertebrate derives from the Latin word vertebratus (Pliny), meaning joint of the spine. [10]

Vertebrate is derived from the word vertebra , which refers to any of the bones or segments of the spinal column. [11]

Anatomy and morphology

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), [12] 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. [13]

Vertebral column

The defining characteristic of a vertebrate is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord).

However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon [14] and coelacanth. Jawed vertebrates are typified by paired appendages (fins or legs, which may be secondarily lost), but this trait is not required in order for an animal to be a vertebrate.

Fossilized skeleton of Diplodocus carnegii, showing an extreme example of the backbone that characterizes the vertebrates. Naturkundemuseum Berlin - Dinosaurierhalle.jpg
Fossilized skeleton of Diplodocus carnegii , showing an extreme example of the backbone that characterizes the vertebrates.

Gills

Gill arches bearing gills in a pike Gills (esox).jpg
Gill arches bearing gills in a pike

All basal vertebrates 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 cartilagenous or bony gill arch. [15] 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. [13]

In amphibians and some primitive bony fishes, the larvae bear external gills, branching off from the gill arches. [16] 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. [17]

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. [13]

Central nervous system

The central nervous system of vertebrates is based on a hollow nerve cord running along the length of the animal. Of particular importance and unique to vertebrates is the presence of neural crest cells. These are progenitors of stem cells, and critical to coordinating the functions of cellular components. [18] 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. [19] [20] [21]

The vertebrates are the only chordate group to exhibit cephalisation, the concentration of brain functions in the head. A slight swelling of the anterior end of the nerve cord is found in the lancelet, a chordate, though it lacks the eyes and other complex sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation. [13]

A peripheral nervous system branches out from the nerve cord to innervate the various systems. The front end of the nerve 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), further differentiated in the various vertebrate groups. [22] Two laterally placed eyes form around outgrowths from the midbrain, except in hagfish, though this may be a secondary loss. [23] [24] The forebrain is well-developed and subdivided in most tetrapods, while the midbrain dominates in many fish and some salamanders. Vesicles of the forebrain are usually paired, giving rise to hemispheres like the cerebral hemispheres in mammals. [22]

The resulting anatomy of the central nervous system, with a single hollow nerve cord topped by a series of (often paired) vesicles, is unique to vertebrates. All invertebrates with well-developed brains, such as insects, spiders and squids, have a ventral rather than dorsal system of ganglions, with a split brain stem running on each side of the mouth or gut. [13]

Evolutionary history

First vertebrates

The early vertebrate Haikouichthys Haikouichthys cropped.jpg
The early vertebrate Haikouichthys

Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw rise in organism diversity. The earliest known vertebrate is believed to be the mylinofulale . [1] Another early vertebrate is Haikouichthys ercaicunensis . 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. [25] All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed. [26] 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. [27]

From fish to amphibians

Acanthostega, a fish-like early labyrinthodont. Acanthostega BW.jpg
Acanthostega , a fish-like early labyrinthodont.

The first jawed vertebrates may have appeared in the late Ordovician and became common in the Devonian, often known as the "Age of Fishes". [28] The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. [29] 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. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional form between fishes and amphibians.

Mesozoic vertebrates

Amniotes branched from labyrinthodonts in the subsequent Carboniferous period. The Parareptilia and synapsid amniotes were common during the late Paleozoic, while diapsids became dominant during the Mesozoic. In the sea, the bony fishes became dominant. Birds, a derived form of dinosaur, evolved in the Jurassic. [30] The demise of the non-avian dinosaurs at the end of the Cretaceous allowed for the expansion of mammals, which had evolved from the therapsids, a group of synapsid amniotes, during the late Triassic Period.

After the Mesozoic

The Cenozoic world has seen 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). Fishes of myriad varieties are the main predators in most of the world's water bodies, both freshwater and marine. 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).

Classification

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. [31] Evolutionary systematics gives an overview; phylogenetic systematics gives detail. The two systems are thus complementary rather than opposed. [32]

Traditional classification

Traditional spindle diagram of the evolution of the vertebrates at class level Spindle diagram.jpg
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: [13]

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

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) [33] is given here:

†: Extinct

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. [33] For instance, descendants of the first reptiles include modern reptiles as well as 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 [ citation needed ], organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology.

Phylogenetic relationships

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 one below is based on studies compiled by Philippe Janvier and others for the Tree of Life Web Project and Delsuc et al. [34] [35] † denotes an entirely extinct clade.

Vertebrata/
Agnatha/

Hyperoartia (lampreys) Nejonoga, Iduns kokbok.jpg

Myxini

Cyclostomes

Euconodonta

Pteraspidomorphi Astraspis desiderata.png

Thelodonti Sphenonectris turnernae white background.jpg

Anaspida Pharyngolepis2.png

Galeaspida

Pituriaspida

Osteostraci

Gnathostomata

Placodermi (armoured fishes) Dunkleosteus intermedius.jpg

Acanthodii (acanthodii; paraphyletic) Acanthodes BW.jpg

Chondrichthyes (cartilaginous fishes) Carcharodon carcharias drawing.jpg

Euteleostomi

Actinopterygii (ray-finned fishes) Cyprinus carpio3.jpg

Sarcopterygii

Onychodontiformes OnychodusDB15 flipped.jpg

Actinistia (coelacanths) Coelacanth flipped.png

Porolepiformes Reconstruction of Porolepis sp flipped.jpg

Dipnoi (lungfishes) Barramunda coloured.jpg

Rhizodontimorpha Gooloogongia loomesi reconstruction.jpg

Tristichopteridae Eusthenodon DB15 flipped.jpg

Tetrapoda Deutschlands Amphibien und Reptilien (Salamandra salamdra).jpg

(lobefinned fish)
Craniata

Number of extant species

The number of described vertebrate species are split evenly 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. [36]

Vertebrate groupsImageClassEstimated number of
described species [36]
Group
totals [36]
Anamniote

lack
amniotic
membrane

so need to
reproduce
in water
Jawless Fish Eptatretus polytrema.jpg Myxini
(hagfish)
32,900
Eudontomyzon danfordi Tiszai ingola.jpg Hyperoartia
(lamprey)
Jawed Shark fish chondrichthyes.jpg cartilaginous
fish
Carassius wild golden fish 2013 G1.jpg ray-finned
fish
Coelacanth-bgiu.png lobe-finned
fish
Tetrapods Lithobates pipiens.jpg amphibians 7,30233,278
Amniote

have
amniotic
membrane

adapted to
reproducing
on land
Squirrel (PSF).png mammals 5,513
Florida Box Turtle Digon3.jpg reptiles 10,711
Secretary bird (Sagittarius serpentarius) 2.jpg birds 10,425
Total described species66,178

The IUCN estimates that 1,305,075 extant invertebrate species have been described, [36] which means that less than 5% of the described animal species in the world are vertebrates.

Vertebrate species databases

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

Reproductive systems

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.

Inbreeding

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. [37] The effects of inbreeding have been studied in many vertebrate species.

In several species of fish, inbreeding was found to decrease reproductive success. [38] [39] [40]

Inbreeding was observed to increase juvenile mortality in 11 small animal species. [41]

A common breeding practice for pet dogs is mating between close relatives (e.g. between half- and full siblings). [42] This practice generally has a negative effect on measures of reproductive success, including decreased litter size and puppy survival. [43] [44] [45]

Incestuous matings in birds result in severe fitness costs due to inbreeding depression (e.g. reduction in hatchability of eggs and reduced progeny survival). [46] [47] [48]

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. [49] 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. [49]

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. [50] 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. [50]

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. [51] 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. [51] This preference may enhance the fitness of progeny by reducing inbreeding depression.

Outcrossing

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 [52] (see heterosis). Vertebrates have evolved numerous diverse mechanisms for avoiding close inbreeding and promoting outcrossing [53] (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. [54]

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. [48]

Southern pied babblers (Turdoides bicolor) appear to avoid inbreeding in two ways: through dispersal and by avoiding familiar group members as mates. [55] Although both males and females 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. [56] Female offspring rarely stay at home, dispersing over distances that allow them to breed independently or to join unrelated groups.

Parthenogenesis

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. [57] [58] The WW females are likely produced by terminal automixis.

Mole salamanders are an ancient (2.4–3.8 million year-old) unisexual vertebrate lineage. [59] 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. [60] 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.

Self-fertilization

The mangrove killifish (Kryptolebias marmoratus) produces both eggs and sperm by meiosis and routinely reproduces by self-fertilisation. This capacity has apparently persisted for at least several hundred thousand years. [61] 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. [62] 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. [63] [64] 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. [63]

The Living Planet Index, following 16,704 populations of 4,005 species of vertebrates, shows a decline of 60% between 1970 and 2014. [65] Since 1970, freshwater species declined 83%, and tropical populations in South and Central America declined 89%. [66] The authors note that, "An average trend in population change is not an average of total numbers of animals lost." [66] According to WWF, this could lead to a sixth major extinction event. [67] The five main causes of biodiversity loss are land-use change, overexploitation of natural resources, climate change, pollution and invasive species. [68]

See also

Related Research Articles

Chordate Phylum of animals having a dorsal nerve cord

A chordate is an animal of the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, and a post-anal tail: these four anatomical features define this phylum. Chordates are also bilaterally symmetric, and have a coelom, metameric segmentation, and circulatory system.

Osteichthyes Diverse group of fish with skeletons of bone rather than cartilage

Osteichthyes, popularly referred to as the bony fish, is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue, as opposed to cartilage. The vast majority of fish are members of Osteichthyes, which is an extremely diverse and abundant group consisting of 45 orders, and over 435 families and 28,000 species. It is the largest class of vertebrates in existence today. The group Osteichthyes is divided into the ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii). The oldest known fossils of bony fish are about 420 million years old, which are also transitional fossils, showing a tooth pattern that is in between the tooth rows of sharks and bony fishes.

Tetrapod Superclass of the first four-limbed vertebrates and their descendants

Tetrapods are four-limbed animals constituting the superclass Tetrapoda. It includes extant and extinct amphibians, reptiles, and mammals. Tetrapods evolved from a group of animals known as the Tetrapodomorpha which, in turn, evolved from ancient sarcopterygians around 390 million years ago in the middle Devonian period; their forms were transitional between lobe-finned fishes and the four-limbed tetrapods. The first tetrapods appeared by the late Devonian, 367.5 million years ago; the specific aquatic ancestors of the tetrapods, and the process by which they colonized Earth's land after emerging from water remains unclear. The change from a body plan for breathing and navigating in water to a body plan enabling the animal to move on land is one of the most profound evolutionary changes known. The first tetrapods were primarily aquatic. Modern amphibians, which evolved from earlier groups, are generally semiaquatic; the first stage of their lives is as fish-like tadpoles, and later stages are partly terrestrial and partly aquatic. However, most tetrapod species today are amniotes, most of those are terrestrial tetrapods whose branch evolved from earlier tetrapods about 340 million years ago. The key innovation in amniotes over amphibians is laying of eggs on land or having further evolved to retain the fertilized egg(s) within the mother.

Agnatha Superclass of fishes

Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct species. The group is sister to all vertebrates with jaws, known as gnathostomes.

Amniote Clade of tetrapods including reptiles, birds and mammals

Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals. Amniotes lay their eggs on land or retain the fertilized egg within the mother, and are distinguished from the anamniotes, which typically lay their eggs in water. Older sources, particularly prior to the 20th century, may refer to amniotes as "higher vertebrates" and anamniotes as "lower vertebrates", based on the discredited idea of the evolutionary great chain of being.

Fish anatomy study of the form or morphology of fishes

Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.

Craniate clade of chordates

A craniate is a member of the Craniata, a proposed clade of chordate animals with a skull of hard bone or cartilage. Living representatives are the Myxini (hagfishes), Hyperoartia, and the much more numerous Gnathostomata. Formerly distinct from vertebrates by excluding hagfish, molecular and anatomical research in the 21st century has led to the reinclusion of hagfish, making living craniates synonymous with living vertebrates.

Egg organic vessel in which an embryo first begins to develop

The egg is the organic vessel containing the zygote in which an embryo develops until it can survive on its own, at which point the animal hatches. An egg results from fertilization of an egg cell. Most arthropods, vertebrates, and mollusks lay eggs, although some, such as scorpions, do not.

Internal fertilization Union of an egg and sperm to form a zygote within the female body

Internal fertilization is the union of an egg cell with a sperm during sexual reproduction inside the female body. For this to happen there needs to be a method for the male to introduce the sperm into the female's reproductive tract. In mammals, reptiles, some birds, some fish and certain other groups of animals, this is done by copulation, the penis or other intromittent organ being introduced into the vagina or cloaca. In most birds, the cloacal kiss is used, the two animals pressing their cloacas together while transferring sperm. Salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm, from the male to the female. Following fertilization, the embryos are laid as eggs in oviparous organisms, or in viviparous organisms, continue to develop inside the reproductive tract of the mother to be born later as live young.

Fish reproduction The reproductive physiology of fishes

Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The genital papilla is a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish often can be determined by the shape of its papilla.

Fish Vertebrate animal that lives in water and usually has gills

Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups.

Marine vertebrate Fish, seabirds, marine reptiles, and marine mammals

Marine vertebrates are vertebrates that live in marine environments. These are the marine fish and the marine tetrapods. Vertebrates are a subphylum of chordates that have a vertebral column (backbone). The vertebral column provides the central support structure for an internal skeleton. The internal skeleton gives shape, support, and protection to the body and can provide a means of anchoring fins or limbs to the body. The vertebral column also serves to house and protect the spinal cord that lies within the column.

Branchial arch

Branchial arches, or gill arches, are a series of bony "loops" present in fish, which support the gills. As gills are the primitive condition of vertebrates, all vertebrate embryos develop pharyngeal arches, though the eventual fate of these arches varies between taxa. In jawed fish, the first arch develops into the jaws, the second into the hyomandibular complex, with the posterior arches supporting gills. In amphibians and reptiles, many elements are lost including the gill arches, resulting in only the oral jaws and a hyoid apparatus remaining. In mammals and birds, the hyoid is still more simplified.

Deuterostome Superphylum of bilateral animals

Deuterostomes constitute a superphylum of animals. It is a sister clade of Protostomia, with which it forms the Nephrozoa clade.

The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.

Female sperm storage The retention of sperm by a female following mating.

Female sperm storage is a biological process and often a type of sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, or egg, is fertilized. The site of storage is variable among different animal taxa and ranges from structures that appear to function solely for sperm retention, such as insect spermatheca and bird sperm storage tubules, to more general regions of the reproductive tract enriched with receptors to which sperm associate before fertilization, such as the caudal portion of the cow oviduct containing sperm-associating annexins. Female sperm storage is an integral stage in the reproductive process for many animals with internal fertilization. It has several documented biological functions including:

Fish fin Bony skin-covered spines or rays protruding from the body of a fish

Fins are usually the most distinctive anatomical features of a fish. They are composed of bony spines or rays protruding from the body with skin covering them and joining them together, either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as seen in sharks. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles. Their principal function is to help the fish swim.

Evolution of fish The origin and diversification of fish through geologic time

The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.

Fish gill

Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide.

Evolution of tetrapods The evolution of four legged vertebrates and their derivatives

The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. Tetrapods are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals. While most species today are terrestrial, little evidence supports the idea that any of the earliest tetrapods could move about on land, as their limbs could not have held their midsections off the ground and the known trackways do not indicate they dragged their bellies around. Presumably, the tracks were made by animals walking along the bottoms of shallow bodies of water. The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear, and are areas of active research and debate among palaeontologists at present.

References

  1. 1 2 Shu; et al. (4 November 1999). "Lower Cambrian vertebrates from south China". Nature. 402 (6757): 42–46. Bibcode:1999Natur.402...42S. doi:10.1038/46965.
  2. Peterson, Kevin J.; Cotton, James A.; Gehling, James G.; Pisani, Davide (27 April 2008). "The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1496): 1435–1443. doi:10.1098/rstb.2007.2233. PMC   2614224 . PMID   18192191.
  3. 1 2 Nielsen, C. (July 2012). "The authorship of higher chordate taxa". Zoologica Scripta. 41 (4): 435–436. doi:10.1111/j.1463-6409.2012.00536.x.
  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...2E.373O. doi:10.1038/ncomms1355. ISSN   2041-1723. PMC   3157150 . PMID   21712821.
  6. Kuraku; et al. (December 1999). "Monophyly of Lampreys and Hagfishes Supported by Nuclear DNA–Coded Genes". Journal of Molecular Evolution. 49 (6): 729–35. Bibcode:1999JMolE..49..729K. doi:10.1007/PL00006595. PMID   10594174.
  7. Stock, D.; Whitt, G.S. (7 August 1992). "Evidence from 18S ribosomal RNA sequences that lampreys and hagfish form a natural group". Science. 257 (5071): 787–9. Bibcode:1992Sci...257..787S. doi:10.1126/science.1496398. PMID   1496398.
  8. Nicholls, H. (10 September 2009). "Mouth to Mouth". Nature. 461 (7261): 164–166. doi: 10.1038/461164a . PMID   19741680.
  9. Marshall, Michael. "Animal Populations Have Fallen 60 Percent And That's Bad Even If They Don't Go Extinct". Forbes. Retrieved 21 May 2020.
  10. "vertebrate". Online Etymology Dictionary. Dictionary.com.
  11. "vertebra". Online Etymology Dictionary. Dictionary.com.
  12. Waggoner, Ben. "Vertebrates: More on Morphology". UCMP. Retrieved 13 July 2011.
  13. 1 2 3 4 5 6 Romer, A.S. (1949): The Vertebrate Body. W.B. Saunders, Philadelphia. (2nd ed. 1955; 3rd ed. 1962; 4th ed. 1970)
  14. 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.
  15. Scott, T. (1996). Concise encyclopedia biology . Walter de Gruyter. p.  542. ISBN   978-3-11-010661-9.
  16. Szarski, Henryk (1957). "The Origin of the Larva and Metamorphosis in Amphibia". The American Naturalist. 91 (860): 283–301. doi:10.1086/281990. JSTOR   2458911.
  17. Clack, J. A. (2002): Gaining ground: the origin and evolution of tetrapods. Indiana University Press, Bloomington, Indiana. 369 pp
  18. Teng, L.; Labosky, P. A. (2006). "Neural crest stem cells" In: Jean-Pierre Saint-Jeannet, Neural Crest Induction and Differentiation, pp. 206-212, Springer Science & Business Media. ISBN   9780387469546.
  19. Gans, C.; Northcutt, R. G. (1983). "Neural crest and the origin of vertebrates: a new head". Science. 220 (4594): 268–273. Bibcode:1983Sci...220..268G. doi:10.1126/science.220.4594.268. PMID   17732898.
  20. Bronner, M. E.; LeDouarin, N. M. (1 June 2012). "Evolution and development of the neural crest: An overview". Developmental Biology. 366 (1): 2–9. doi:10.1016/j.ydbio.2011.12.042. PMC   3351559 . PMID   22230617.
  21. 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
  22. 1 2 Hildebrand, M.; Gonslow, G. (2001): Analysis of Vertebrate Structure. 5th edition. John Wiley & Sons, Inc. New York
  23. "Keeping an eye on evolution". PhysOrg.com. 3 December 2007. Retrieved 4 December 2007.
  24. "Hyperotreti". tolweb.org.
  25. Waggoner, B. "Vertebrates: Fossil Record". UCMP. Archived from the original on 29 June 2011. Retrieved 15 July 2011.
  26. Tim Haines, T.; Chambers, P. (2005). The Complete Guide to Prehistoric Life . Firefly Books.
  27. Donoghue, P. C. J.; Forey, P. L.; Aldridge, R. J. (May 2000). "Conodont affinity and chordate phylogeny". Biological Reviews. 75 (2): 191–251. doi:10.1111/j.1469-185X.1999.tb00045.x. PMID   10881388.
  28. Encyclopædia Britannica: a new survey of universal knowledge, Volume 17. Encyclopædia Britannica. 1954. p. 107.
  29. Berg, L.R.; Solomon, E.P.; Martin, D.W. (2004). Biology. Cengage Learning. p. 599. ISBN   978-0-534-49276-2.
  30. Cloudsley-Thompson, J. L. (2005). Ecology and behaviour of Mesozoic reptiles . 9783540224211: Springer. p.  6.CS1 maint: location (link)
  31. 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.
  32. 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
  33. 1 2 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. Retrieved 16 March 2006.
  34. 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/
  35. Delsuc F, Philippe H, Tsagkogeorga G, Simion P, Tilak MK, Turon X, López-Legentil S, Piette J, Lemaire P, Douzery EJ (April 2018). "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.
  36. 1 2 3 4 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).
  37. Charlesworth, D.; Willis, J.H. (November 2009). "The genetics of inbreeding depression". Nat. Rev. Genet. 10 (11): 783–796. doi:10.1038/nrg2664. PMID   19834483.
  38. Gallardo, J.A.; Neira, R. (July 2005). "Environmental dependence of inbreeding depression in cultured Coho salmon (Oncorhynchus kisutch): aggressiveness, dominance and intraspecific competition". Heredity (Edinb). 95 (6): 449–56. doi: 10.1038/sj.hdy.6800741 . PMID   16189545.
  39. Ala-Honkola, O.; Uddström, A.; Pauli, B.D.; Lindström, K. (2009). "Strong inbreeding depression in male mating behaviour in a poeciliid fish". J. Evol. Biol. 22 (7): 1396–1406. doi:10.1111/j.1420-9101.2009.01765.x. PMID   19486236.
  40. Bickley, L.K.; Brown, A.R.; Hosken, D.J.; Hamilton, P.B.; Le Page, G.; Paull, G.C.; Owen, S.F.; Tyler, C.R. (February 2013). "Interactive effects of inbreeding and endocrine disruption on reproduction in a model laboratory fish". Evol Appl. 6 (2): 279–289. doi:10.1111/j.1752-4571.2012.00288.x. PMC   3689353 . PMID   23798977.
  41. Ralls, K.; Ballou, J. (1982). "Effect of inbreeding on juvenile mortality in some small mammal species". Lab Anim. 16 (2): 159–66. doi: 10.1258/002367782781110151 . PMID   7043080.
  42. Leroy, G. (August 2011). "Genetic diversity, inbreeding and breeding practices in dogs: results from pedigree analyses". Vet. J. 189 (2): 177–182. doi:10.1016/j.tvjl.2011.06.016. PMID   21737321.
  43. 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.
  44. 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.
  45. 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.
  46. Keller, L.F.; Grant, P.R.; Grant, B.R.; Petren, K. (2002). "Environmental conditions affect the magnitude of inbreeding depression in survival of Darwin's finches". Evolution. 56 (6): 1229–39. doi:10.1111/j.0014-3820.2002.tb01434.x. PMID   12144022.
  47. Hemmings, N.L.; Slate, J.; Birkhead, T.R. (2012). "Inbreeding causes early death in a passerine bird". Nat Commun. 3: 863. Bibcode:2012NatCo...3..863H. doi: 10.1038/ncomms1870 . PMID   22643890.
  48. 1 2 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 .
  49. 1 2 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 .
  50. 1 2 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.
  51. 1 2 Olsson, M.; Shine, R.; Madsen, T.; Gullberg, A. Tegelström H (1997). "Sperm choice by females". Trends Ecol. Evol. 12 (11): 445–6. doi:10.1016/s0169-5347(97)85751-5. PMID   21238151.
  52. Bernstein, H.; Byerly, H.C.; Hopf, F.A.; Michod, R.E. (1985). "Genetic damage, mutation, and the evolution of sex". Science. 229 (4719): 1277–81. Bibcode:1985Sci...229.1277B. doi:10.1126/science.3898363. PMID   3898363.
  53. Pusey, A.; Wolf, M. (1996). "Inbreeding avoidance in animals". Trends Ecol. Evol. 11 (5): 201–6. doi:10.1016/0169-5347(96)10028-8. PMID   21237809.
  54. Szulkin, M.; Sheldon, B.C. (2008). "Dispersal as a means of inbreeding avoidance in a wild bird population". Proc. Biol. Sci. 275 (1635): 703–11. doi:10.1098/rspb.2007.0989. PMC   2596843 . PMID   18211876.
  55. Nelson-Flower, M.J.; Hockey, P.A.; O'Ryan, C.; Ridley, A.R. (2012). "Inbreeding avoidance mechanisms: dispersal dynamics in cooperatively breeding southern pied babblers". J Anim Ecol. 81 (4): 876–83. doi:10.1111/j.1365-2656.2012.01983.x. PMID   22471769.
  56. Riehl, C.; Stern, C.A. (2015). "How cooperatively breeding birds identify relatives and avoid incest: New insights into dispersal and kin recognition". BioEssays. 37 (12): 1303–8. doi:10.1002/bies.201500120. PMID   26577076.
  57. Booth, W.; Smith, C.F.; Eskridge, P.H.; Hoss, S.K.; Mendelson, J.R.; Schuett, G.W. (2012). "Facultative parthenogenesis discovered in wild vertebrates". Biol. Lett. 8 (6): 983–5. doi:10.1098/rsbl.2012.0666. PMC   3497136 . PMID   22977071.
  58. Booth, W.; Million, L.; Reynolds, R.G.; Burghardt, G.M.; Vargo, E.L.; Schal, C.; Tzika, A.C.; Schuett, G.W. (2011). "Consecutive virgin births in the new world boid snake, the Colombian rainbow Boa, Epicrates maurus". J. Hered. 102 (6): 759–63. doi: 10.1093/jhered/esr080 . PMID   21868391.
  59. Bogart, J.P.; Bi, K.; Fu, J.; Noble, D.W.; Niedzwiecki, J. (February 2007). "Unisexual salamanders (genus Ambystoma) present a new reproductive mode for eukaryotes". Genome. 50 (2): 119–36. doi:10.1139/g06-152. PMID   17546077.
  60. Bi, K; Bogart, J.P. (April 2010). "Probing the meiotic mechanism of intergenomic exchanges by genomic in situ hybridization on lampbrush chromosomes of unisexual Ambystoma (Amphibia: Caudata)". Chromosome Res. 18 (3): 371–82. doi:10.1007/s10577-010-9121-3. PMID   20358399.
  61. 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.
  62. 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 .
  63. 1 2 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.
  64. Earley, R.L.; Hanninen, A.F.; Fuller, A.; Garcia, M.J.; Lee, E.A. (2012). "Phenotypic plasticity and integration in the mangrove rivulus (Kryptolebias marmoratus): a prospectus". Integr. Comp. Biol. 52 (6): 814–27. doi:10.1093/icb/ics118. PMC   3501102 . PMID   22990587.
  65. "Living Planet Report 2018 | WWF". wwf.panda.org. Retrieved 21 May 2020.
  66. 1 2 Living Planet Report - 2018: Aiming Higher (PDF). 2018. ISBN   978-2-940529-90-2.
  67. "WWF Finds Human Activity Is Decimating Wildlife Populations". Time. Retrieved 21 May 2020.
  68. 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.Cite journal requires |journal= (help)

Bibliography