134-398: Ossea Batsch, 1788 Vertebrates ( / ˈ v ɜːr t ə b r ɪ t s , - ˌ b r eɪ t s / ) are animals with a backbone or spine, consisting of vertebrae and intervertebral discs . The vertebrae are irregular bones , and the intervertebral discs are of fibrocartilage . The vertebral column surrounds and protects the spinal cord . The other feature unique to vertebrates is
268-956: A fundamental frequency ranging from 8 to 25 Hz; their vocalizations may vary by region, season, behavior, and time of day. Orcas are their only natural predators. The blue whale was abundant in nearly all the Earth's oceans until the end of the 19th century. It was hunted almost to the point of extinction by whalers until the International Whaling Commission banned all blue whale hunting in 1966. The International Union for Conservation of Nature has listed blue whales as Endangered as of 2018. It continues to face numerous man-made threats such as ship strikes , pollution , ocean noise , and climate change . Scientists found evidence of this through morphological or epidemiological analysis. These analyses are accompanied by chemical profiles that use fecal and tissue which continue to prove
402-399: A gastrula with a digestive chamber and two separate germ layers , an external ectoderm and an internal endoderm . In most cases, a third germ layer, the mesoderm , also develops between them. These germ layers then differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction generally leads to inbreeding depression within
536-506: A 21 m (70 ft) pregnant female whale caught off Iceland in 1986 found that it had a blue whale mother and a fin whale father, while its fetus was sired by a blue whale. In 2024, a genome analysis of North Atlantic blue whales found evidence that approximately 3.5% of the blue whales' genome was derived from hybridization with fin whales. Gene flow was found to be unidirectional from fin whales to blue whales. Comparison with Antarctic blue whales showed that this hybridization began after
670-500: A 9-second-long, 27 Hz tone, and then a 1-second downsweep to 19 Hz, followed by a downsweep further to 18 Hz. Other vocalizations include 1–4 second long, frequency-modulated calls with a frequency of 80 and 38 Hz. There is evidence that some blue whale songs have temporally declined in tonal frequency. The vocalization of blue whales in the Eastern North Pacific decreased in tonal frequency by 31% from
804-569: A blue whale comes from Robert Sibbald 's Phalainologia Nova , after Sibbald found a stranded whale in the estuary of the Firth of Forth , Scotland, in 1692. The name "blue whale" was derived from the Norwegian blåhval , coined by Svend Foyn shortly after he had perfected the harpoon gun. The Norwegian scientist G. O. Sars adopted it as the common name in 1874. Blue whales were referred to as "Sibbald's rorqual", after Robert Sibbald, who first described
938-462: A calf thought to be nursing was filmed in New Zealand in 2016. Calves may be weaned when they reach 6–8 months old at a length of 16 meters (53 ft). They gain roughly 37,500 pounds (17,000 kg) during the weaning period. Interbirth periods last two to three years; they average 2.6 years in pygmy blue whales. Blue whales produce some of the loudest and lowest frequency vocalizations in
1072-417: A central nervous system arising from a single nerve cord dorsal to the gut tube , headed by a series of (typically paired) brain vesicles, is unique to vertebrates. This is in stark contrast to invertebrates with well-developed central nervous systems such as arthropods and cephalopods , which have an often ladder-like ventral nerve cord made of paired segmental ganglia on the opposite ( ventral ) side of
1206-547: A clade Xenambulacraria for the Xenacoelamorpha + Ambulacraria; this is either within Deuterostomia, as sister to Chordata, or the Deuterostomia are recovered as paraphyletic, and Xenambulacraria is sister to the proposed clade Centroneuralia , consisting of Chordata + Protostomia. Eumetazoa , a clade which contains Ctenophora and ParaHoxozoa , has been proposed as a sister group to Porifera . A competing hypothesis
1340-598: A group of orcas harassing a blue whale in Monterey Bay . The blue whale defended itself by slapping its tail. A similar incident was recorded by a drone in Monterey Bay in May 2017. The first direct observations of orca predation occurred off the south coast of Western Australia, two in 2019 and one more in 2021. The first victim was estimated to be 18–22 meters (59–72 ft). In Antarctic waters, blue whales accumulate diatoms of
1474-521: A hollow neural tube ) 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 dorsal nerve cord during development, initiate the formation of neuronal ganglia and various special sense organs. The peripheral nervous system forms when neural crest cells branch out laterally from
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#17328484951781608-486: A part of oil and gas exploration. Blue whales in the Southern California Bight decreased calling in the presence of mid-frequency active (MFA) sonar . Exposure to simulated MFA sonar was found to interrupt blue whale deep-dive feeding but no changes in behavior were observed in individuals feeding at shallower depths. The responses also depended on the animal's behavioral state, its (horizontal) distance from
1742-1105: A population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding . Some animals are capable of asexual reproduction , which often results in a genetic clone of the parent. This may take place through fragmentation ; budding , such as in Hydra and other cnidarians ; or parthenogenesis , where fertile eggs are produced without mating , such as in aphids . Animals are categorised into ecological groups depending on their trophic levels and how they consume organic material . Such groupings include carnivores (further divided into subcategories such as piscivores , insectivores , ovivores , etc.), herbivores (subcategorized into folivores , graminivores , frugivores , granivores , nectarivores , algivores , etc.), omnivores , fungivores , scavengers / detritivores , and parasites . Interactions between animals of each biome form complex food webs within that ecosystem . In carnivorous or omnivorous species, predation
1876-685: A problem in Sri Lankan waters, where their habitat intersects with one of the world's most active shipping routes. Here, strikes caused the deaths of eleven blue whales in 2010 and 2012, and at least two in 2014. Ship-strike mortality claimed the lives of two blue whales off southern Chile in the 2010s. Possible measures for reducing future ship strikes include better predictive models of whale distribution, changes in shipping lanes, vessel speed reductions, and seasonal and dynamic management of shipping lanes. Few cases of blue whale entanglement in commercial fishing gear have been documented. The first report in
2010-587: A protein related to ubiquitin carboxyl-terminal hydrolase are exclusively shared by all vertebrates and reliably distinguish them from all other animals. A specific relationship between vertebrates and tunicates is strongly supported by two CSIs found in the proteins Rrp44 (associated with the exosome complex ) and serine palmitoyltransferase . These are exclusively shared by species from these two subphyla, but not cephalochordates . This indicates hat vertebrates are more closely related to tunicates than cephalochordates. The "Notochordata hypothesis" suggested that
2144-403: A reproductive function. D calls may have multiple functions. They are produced by both sexes during social interactions while feeding. and by males when competing for mates. Blue whale calls recorded off Sri Lanka have a three-unit phrase. The first unit is a 19.8 to 43.5 Hz pulsive call, and is normally 17.9 ± 5.2 seconds long. The second unit is a 55.9 to 72.4 Hz FM upsweep that
2278-399: A separate population, and implies that they do not fall under the same subspecies as the pygmy blue whale ( B. m. brevicauda ). The blue whale is a slender-bodied cetacean with a broad U-shaped head; thin, elongated flippers ; a small 33 centimeters (13 in) sickle-shaped dorsal fin located close to the tail, and a large tail stock at the root of the wide and thin flukes . The upper jaw
2412-551: A single lunge. It is estimated that an average-sized blue whale must consume 1,120 ± 359 kilograms (2,469 ± 791 lb) of krill a day. In the southern ocean, blue whales feed on Antarctic krill ( Euphausia superba ). In the South Australia, pygmy blue whales ( B. m. brevicauda ) feeds on Nyctiphanes australis . In California, they feed mostly on Thysanoessa spinifera , but also less commonly on North pacific krill ( Euphausia pacifica ). Research of
2546-476: A single opening, which serves as both mouth and anus. Animals in both phyla have distinct tissues, but these are not organised into discrete organs . They are diploblastic , having only two main germ layers, ectoderm and endoderm. Blue whale The blue whale ( Balaenoptera musculus ) is a marine mammal and a baleen whale . Reaching a maximum confirmed length of 29.9 m (98 ft) and weighing up to 199 t (196 long tons; 219 short tons), it
2680-734: A worldwide distribution, but are mostly absent from the Arctic Ocean and the Mediterranean , Okhotsk , and Bering Sea . Blue whales off the Chilean coast might be a separate subspecies based on their geographic separation, genetics, and unique song types. Chilean blue whales might overlap in the Eastern Tropical Pacific with Antarctica blue whales and Eastern North Pacific blue whales. Chilean blue whales are genetically differentiated from Antarctica blue whales such that interbreeding
2814-468: Is 13.8 ± 1.1 seconds long. The final unit is 28.5 ± 1.6 seconds long with a tone of 108 to 104.7 Hz. A blue whale call recorded off Madagascar, a two-unit phrase, consists of 5–7 pulses with a center frequency of 35.1 ± 0.7 Hz lasting 4.4 ± 0.5 seconds proceeding a 35 ± 0 Hz tone that is 10.9 ± 1.1 seconds long. In the Southern Ocean, blue whales produce 18-second vocals which start with
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#17328484951782948-900: Is 22.0 meters (72.1 ft) for Eastern North Pacific blue whales, 24 meters (79 ft) for central and western North Pacific blue whales, 21–24 meters (68–78 ft) for North Atlantic blue whales, 25.4–26.3 meters (83.4–86.3 ft) for Antarctic blue whales, 23.5 meters (77.1 ft) for Chilean blue whales, and 21.3 meters (69.9 ft) for pygmy blue whales. In the Northern Hemisphere, males weigh an average 100 metric tons (220,000 lb) and females 112 metric tons (247,000 lb). Eastern North Pacific blue whale males average 88.5 tonnes (195,000 lb) and females 100 tonnes (220,000 lb). Antarctic males average 112 tonnes (247,000 lb) and females 130 tonnes (290,000 lb). Pygmy blue whale males average 83.5 tonnes (184,000 lb) to 99 tonnes (218,000 lb). The weight of
3082-464: Is a consumer–resource interaction where the predator feeds on another organism, its prey , who often evolves anti-predator adaptations to avoid being fed upon. Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various antagonistic/ competitive coevolutions . Almost all multicellular predators are animals. Some consumers use multiple methods; for example, in parasitoid wasps ,
3216-433: Is a stage in embryonic development that is unique to animals, allowing cells to be differentiated into specialised tissues and organs. All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins . During development, the animal extracellular matrix forms a relatively flexible framework upon which cells can move about and be reorganised, making
3350-458: Is disputed, as they might be water-escape or other structures. Animals are monophyletic , meaning they are derived from a common ancestor. Animals are the sister group to the choanoflagellates , with which they form the Choanozoa . The dates on the phylogenetic tree indicate approximately how many millions of years ago ( mya ) the lineages split. Ros-Rocher and colleagues (2021) trace
3484-634: Is estimated to be 5,000–15,000 mature individuals and 10,000–25,000 total as of 2018. By comparison, there were at least 140,000 mature whales in 1926. There are an estimated total of 1,000–3,000 whales in the North Atlantic, 3,000–5,000 in the North Pacific, and 5,000–8,000 in the Antarctic. There are possibly 1,000–3,000 whales in the eastern South Pacific while the pygmy blue whale may number 2,000–5,000 individuals. Blue whales have been protected in areas of
3618-410: Is evidence of alternative strategies, such as year-round residency, and partial (where only some individuals migrate) or age/sex-based migration. Some whales have been recorded feeding in breeding grounds. The traveling speed for blue whales ranges 5–30 kilometers per hour (3.1–18.6 mph). Their massive size limits their ability to breach . The greatest dive depth reported from tagged blue whales
3752-439: 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 :
3886-450: Is known as zoology , and the study of animal behaviour is known as ethology . The animal kingdom is divided into five infrakingdoms / superphyla , namely Porifera , Ctenophora , Placozoa , Cnidaria and Bilateria . Most living animal species belong to the infrakingdom Bilateria, a highly proliferative clade whose members have a bilaterally symmetric body plan , and the vast majority of bilaterians belong to two large superphyla :
4020-457: Is lined with 70–395 black baleen plates. The throat region has 60–88 grooves which allows the skin to expand during feeding. It has two blowholes that can squirt 9.1–12.2 meters (30–40 ft) up in the air. The skin has a mottled grayish-blue coloration, appearing blue underwater. The mottling patterns near the dorsal fin vary between individuals. The underbelly has lighter pigmentation and can appear yellowish due to diatoms in
4154-430: Is not enough information on current abundance trends (e.g., pygmy blue whales), others are critically endangered (e.g., Antarctic blue whales). Blue whales were initially difficult to hunt because of their size and speed. This began to change in the mid-19th century with the development of harpoons that can be shot as projectiles. Blue whale whaling peaked between 1930 and 1931 with 30,000 animals taken. Harvesting of
Vertebrate - Misplaced Pages Continue
4288-808: Is often used to refer only to nonhuman animals. The term metazoa is derived from Ancient Greek μετα ( meta ) 'after' (in biology, the prefix meta- stands for 'later') and ζῷᾰ ( zōia ) 'animals', plural of ζῷον zōion 'animal'. Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and multicellular . Unlike plants and algae , which produce their own nutrients , animals are heterotrophic , feeding on organic material and digesting it internally. With very few exceptions, animals respire aerobically . All animals are motile (able to spontaneously move their bodies) during at least part of their life cycle , but some animals, such as sponges , corals , mussels , and barnacles , later become sessile . The blastula
4422-422: Is only produced by sponges and pelagophyte algae. Its likely origin is from sponges based on molecular clock estimates for the origin of 24-ipc production in both groups. Analyses of pelagophyte algae consistently recover a Phanerozoic origin, while analyses of sponges recover a Neoproterozoic origin, consistent with the appearance of 24-ipc in the fossil record. The first body fossils of animals appear in
4556-525: Is supported by a cartilaginous or bony gill arch , which develop embryonically from pharyngeal arches . Bony fish have three pairs of gill arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven pairs. The ancestral vertebrates likely had more arches than seven, as some of their chordate relatives have more than 50 pairs of gill opens, although most, if not all, of these openings are actually involved in filter feeding rather than respiration . In jawed vertebrates ,
4690-537: Is the Benthozoa clade, which would consist of Porifera and ParaHoxozoa as a sister group of Ctenophora . Several animal phyla lack bilateral symmetry. These are the Porifera (sea sponges), Placozoa , Cnidaria (which includes jellyfish , sea anemones , and corals), and Ctenophora (comb jellies). Sponges are physically very distinct from other animals, and were long thought to have diverged first, representing
4824-486: Is the largest animal known ever to have existed . The blue whale's long and slender body can be of various shades of greyish-blue on its upper surface and somewhat lighter underneath. Four subspecies are recognized: B. m. musculus in the North Atlantic and North Pacific, B. m. intermedia in the Southern Ocean, B. m. brevicauda (the pygmy blue whale ) in the Indian Ocean and South Pacific Ocean, and B. m. indica in
4958-408: Is thus an indicator of age. The oldest blue whale found was determined, using this method, to be 110 years old. The maximum age of a pygmy blue whale determined this way is 73 years. In addition, female blue whales develop scars or corpora albicantia on their ovaries every time they ovulate. In a female pygmy blue whale, one corpus albicans is formed on average every 2.6 years. The blue whale
5092-457: Is unlikely. However, the genetic distinction is less between them and the Eastern North Pacific blue whale, hence there might be gene flow between the South and North hemispheres. A 2019 study by Luis Pastene, Jorge Acevedo and Trevor Branch provided new morphometric data from a survey of 60 Chilean blue whales, hoping to address the debate about the possible distinction of this population from others in
5226-402: Is usually solitary, but can be found in pairs. When productivity is high enough, blue whales can be seen in gatherings of more than 50 individuals. Populations may go on long migrations , traveling to their summer feeding grounds towards the poles and then heading to their winter breeding grounds in more equatorial waters. The animals appear to use memory to locate the best feeding areas. There
5360-605: The Cambrian explosion , which began around 539 million years ago (Mya), and most classes during the Ordovician radiation 485.4 Mya. 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived about 650 Mya during the Cryogenian period. Historically, Aristotle divided animals into those with blood and those without . Carl Linnaeus created
5494-613: The Cephalochordata is the sister taxon to Craniata (Vertebrata). This group, called the Notochordata, was placed as sister group to the Tunicata (Urochordata). Studies since 2006 analyzing large sequencing datasets however strongly support Olfactores (tunicates + vertebrates) as a clade, and hence the placement of Cephalochordata as sister-group to Olfactores (known as the " Olfactores hypothesis "). The following cladogram summarizes
Vertebrate - Misplaced Pages Continue
5628-542: 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
5762-614: The Ediacaran , represented by forms such as Charnia and Spriggina . It had long been doubted whether these fossils truly represented animals, but the discovery of the animal lipid cholesterol in fossils of Dickinsonia establishes their nature. Animals are thought to have originated under low-oxygen conditions, suggesting that they were capable of living entirely by anaerobic respiration , but as they became specialized for aerobic metabolism they became fully dependent on oxygen in their environments. Many animal phyla first appear in
5896-702: The Endangered Species Act . Blue whales are formally classified as endangered under both the U.S. Endangered Species Act and the IUCN Red List . They are also listed on Appendix I under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on the Conservation of Migratory Species of Wild Animals . Although, for some populations, there
6030-472: The Izu–Ogasawara Trench at a depth of 8,336 metres (27,349 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
6164-620: The Jurassic . 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 the Tibetan stone loach ( Triplophysa stolickai ) in western Tibetan hot springs near Longmu Lake at an elevation of 5,200 metres (17,100 feet) to an unknown species of snailfish (genus Pseudoliparis ) in
6298-464: The Last Glacial Maximum . Their more recent divergence has resulted in the subspecies having a relatively low genetic diversity, and New Zealand blue whales have an even lower genetic diversity. Whole genome sequencing suggests that blue whales are most closely related to sei whales with gray whales as a sister group . This study also found significant gene flow between minke whales and
6432-561: 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 ): While this traditional classification is orderly, most of the groups are paraphyletic , i.e. do not contain all descendants of
6566-495: The Southern Ocean , baleen whales appear to feed on Antarctic krill of different sizes, which may lessen competition between them. Blue whale feeding habits may differ due to situational disturbances, like environmental shifts or human interference. This can cause a change in diet due to stress response. Due to these changing situations, there was a study preformed on Blue whales measuring Cortisol levels and comparing them with
6700-865: 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 . Hyperoartia ( lampreys ) [REDACTED] Myxini ( hagfish ) [REDACTED] † Euconodonta [REDACTED] † Myllokunmingiida [REDACTED] † Pteraspidomorphi [REDACTED] † Thelodonti [REDACTED] † Anaspida [REDACTED] † Galeaspida [REDACTED] † Pituriaspida [REDACTED] † Osteostraci [REDACTED] † Antiarchi [REDACTED] † Petalichthyida [REDACTED] † Arthrodira [REDACTED] † Ptyctodontida [REDACTED] † Entelognathus [REDACTED] Animal Animals are multicellular , eukaryotic organisms in
6834-482: The Wnt and TGF-beta signalling pathways which may have enabled animals to become multicellular by providing a pattern for the body's system of axes (in three dimensions), and another 7 are for transcription factors including homeodomain proteins involved in the control of development . Giribet and Edgecombe (2020) provide what they consider to be a consensus internal phylogeny of the animals, embodying uncertainty about
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#17328484951786968-893: The biological kingdom Animalia ( / ˌ æ n ɪ ˈ m eɪ l i ə / ). With few exceptions, animals consume organic material , breathe oxygen , have myocytes and are able to move , can reproduce sexually , and grow from a hollow sphere of cells, the blastula , during embryonic development . Animals form a clade , meaning that they arose from a single common ancestor . Over 1.5 million living animal species have been described , of which around 1.05 million are insects , over 85,000 are molluscs , and around 65,000 are vertebrates . It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complex ecologies and interactions with each other and their environments, forming intricate food webs . The scientific study of animals
7102-665: The evolutionary relationships between taxa . Humans make use of many other animal species for food (including meat , eggs , and dairy products ), for materials (such as leather , fur , and wool ), as pets and as working animals for transportation , and services . Dogs , the first domesticated animal, have been used in hunting , in security and in warfare , as have horses , pigeons and birds of prey ; while other terrestrial and aquatic animals are hunted for sports, trophies or profits. Non-human animals are also an important cultural element of human evolution , having appeared in cave arts and totems since
7236-468: The fossil record during the Cambrian explosion , starting about 539 million years ago, in beds such as the Burgess shale . Extant phyla in these rocks include molluscs , brachiopods , onychophorans , tardigrades , arthropods , echinoderms and hemichordates , along with numerous now-extinct forms such as the predatory Anomalocaris . The apparent suddenness of the event may however be an artifact of
7370-562: 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. Conventional classification has extant vertebrates grouped into seven classes based on traditional interpretations of gross anatomical and physiological traits. The commonly held classification lists three classes of fish and four of tetrapods . In addition to these, there are two classes of extinct armoured fishes,
7504-403: The larvae of lampreys , has evolved into the thyroid in most vertebrates. Vertebrates vary in body length ranging from the frog species Brachycephalus pulex , a Brazilian flea toad, with a minimum adult snout–vent length of 6.45 millimetres (0.254 in) to the blue whale , at up to 33 m (108 ft). With only one exception, the defining characteristics of a vertebrate are
7638-497: The lobe-finned fish Tiktaalik started to move on to land in the late Devonian , about 375 million years ago. Animals occupy virtually all of earth's habitats and microhabitats, with faunas adapted to salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of other organisms. Animals are however not particularly heat tolerant ; very few of them can survive at constant temperatures above 50 °C (122 °F) or in
7772-460: The lobe-finned fish , which gave rise to the tetrapods , the animals with four limbs. Vertebrates make up less than five percent of all described animal species ; the rest are all invertebrates , that lack a backbone. The word 'vertebrate' derives from the Latin vertebratus ("jointed"), from vertebra meaning "joint", in turn from Latin vertere to turn. All vertebrates are built along
7906-407: 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 which may have secondarily lost the structures. The forebrain is more well-developed in most tetrapods and subdivided into
8040-495: The protostomes , which includes organisms such as arthropods , molluscs , flatworms , annelids and nematodes ; and the deuterostomes , which include echinoderms , hemichordates and chordates , the latter of which contains the vertebrates . The much smaller basal phylum Xenacoelomorpha have an uncertain position within Bilateria. Animals first appear in the fossil record in the late Cryogenian period and diversified in
8174-431: The telencephalon and diencephalon , while the midbrain dominates in fish and some salamanders . In vertebrates with paired appendages, especially tetrapods, a pair of secondary enlargements of the hindbrain become the cerebella , which modulate complex motor coordinations . The brain vesicles are usually bilaterally symmetrical , giving rise to the paired cerebral hemispheres in mammals . The resultant anatomy of
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#17328484951788308-399: The vertebral column , and the skull . The embryonic notochord is replaced by a segmented series of irregular bones known as vertebrae . The vertebrae are separated by intervertebral discs of fibrocartilage , which are remnants of the notochord. Hagfish are the only extant vertebrate whose notochord persists and is not integrated or replaced by the vertebral column. In the sturgeon
8442-480: The 1970s. Ship strikes are a significant mortality factor for blue whales, especially off the U.S. West Coast . A total of 17 blue whales were killed or suspected to have been killed by ships between 1998 and 2019 off the U.S. West Coast. Five deaths in 2007 off California were considered an unusual mortality event, as defined under the Marine Mammal Protection Act . Lethal ship strikes are also
8576-647: The Cambrian explosion, possibly as early as 1 billion years ago. Early fossils that might represent animals appear for example in the 665-million-year-old rocks of the Trezona Formation of South Australia . These fossils are interpreted as most probably being early sponges . Trace fossils such as tracks and burrows found in the Tonian period (from 1 gya) may indicate the presence of triploblastic worm-like animals, roughly as large (about 5 mm wide) and complex as earthworms. However, similar tracks are produced by
8710-712: The Cnidaria) never grow larger than 20 μm , and one of the smallest species ( Myxobolus shekel ) is no more than 8.5 μm when fully grown. The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of
8844-493: The Eastern North Pacific population shows that when diving to feed on krill, the whales reach an average depth of 201 meters, with dives lasting 9.8 minutes on average. While most blue whales feed almost exclusively on krill, the Northern Indian Ocean subspecies ( B. m. indica ) instead feeds predominantly on sergestid shrimp. To do so, they dive deeper and for longer periods of time than blue whales in other regions of
8978-588: The Northern Indian Ocean. There is a population in the waters off Chile that may constitute a fifth subspecies. In general, blue whale populations migrate between their summer feeding areas near the poles and their winter breeding grounds near the tropics. There is also evidence of year-round residencies, and partial or age/sex-based migration. Blue whales are filter feeders ; their diet consists almost exclusively of krill . They are generally solitary or gather in small groups, and have no well-defined social structure other than mother–calf bonds. Blue whales vocalize, with
9112-641: The Southern Hemisphere since 1939. In 1955, they were given complete protection in the North Atlantic under the International Convention for the Regulation of Whaling ; this protection was extended to the Antarctic in 1965 and the North Pacific in 1966. The protected status of North Atlantic blue whales was not recognized by Iceland until 1960. In the United States, the species is protected under
9246-429: The U.S. occurred off California in 2015, reportedly some type of deep-water trap/pot fishery. Three more entanglement cases were reported in 2016. In Sri Lanka, a blue whale was documented with a net wrapped through its mouth, along the sides of its body, and wound around its tail. Increasing man-made underwater noise impacts blue whales. They may be exposed to noise from commercial shipping and seismic surveys as
9380-891: The age of sexual maturity. Little is known about mating behavior, or breeding and birthing areas. Blue whales appear to be polygynous , with males competing for females. A male blue whale typically trails a female and will fight off potential rivals. The species mates from fall to winter. Pregnant females eat roughly four percent of their body weight daily, amounting to 60% of their overall body weight throughout summer foraging periods. Gestation may last 10–12 months with calves being 6–7 meters (20–23 ft) long and weighing 2–3 metric tons (2.0–3.0 long tons; 2.2–3.3 short tons) at birth. Estimates suggest that because calves require 2–4 kilograms (4.4–8.8 lb) milk per kg of mass gain, blue whales likely produce 220 kilograms (490 lb) of milk per day (ranging from 110 to 320 kilograms (240 to 710 lb) of milk per day). The first video of
9514-418: The ancestors of the blue and sei whale. Blue whales also displayed high genetic diversity. Blue whales are known to interbreed with fin whales . The earliest description of a possible hybrid between a blue whale and a fin whale was a 20 m (66 ft) anomalous female whale with the features of both the blue and the fin whales taken in the North Pacific. A whale captured off northwestern Spain in 1984,
9648-576: The animal kingdom, and their inner ears appear well adapted for detecting low-frequency sounds. The fundamental frequency for blue whale vocalizations ranges from 8 to 25 Hz. Blue whale songs vary between populations. Vocalizations produced by the Eastern North Pacific population have been well studied. This population produces pulsed calls ("A") and tonal calls ("B"), upswept tones that precede type B calls ("C") and separate downswept tones ("D"). A and B calls are often produced in repeated co-occurring sequences and sung only by males, suggesting
9782-460: The axial endoskeleton, enclosed by neural arches , with a fore-end enlargement within a skeletonized braincase . This provides an alternative name for vertebrates, the craniates . All vertebrate embryos develop transient pharyngeal arches ; in fish, these develop into the branchial arches that support the gills . An organ in the pharynx , the endostyle , which assists in filter feeding in adult cephalochordates and urochordates , and in
9916-531: The basic chordate body plan of five shared characteristics . These are a rigid axial skeleton that includes a vertebral column developed around an elastic or flexible notochord , and a skull. The notochord stretches out for almost the whole length of the body of a chordate , it lies dorsal to the gastrointestinal tract and provides flexible support to the body. The notochord remains in the jawless fish and cephalochordates (non-vertebrate chordates). In vertebrates it becomes replaced either wholly or in part by
10050-435: The blubber to feed on. Intestinal parasites include the trematode genera Ogmogaster and Lecithodesmus ; the tapeworm genera Priapocephalus , Phyllobotrium , Tetrabothrius , Diphyllobotrium , and Diplogonoporus ; and the thorny-headed worm genus Bolbosoma . In the North Atlantic, blue whales also contain the protozoans Entamoeba , Giardia and Balantidium . The global blue whale population
10184-450: The blue whale in size, with Perucetus also being heavier than the blue whale with a mean weight of 180 t (180 long tons; 200 short tons). These estimates are based on fragmentary remains, and the proposed size for the latter has been disputed in 2024. Other studies estimate that on land, large sauropods like Bruhathkayosaurus (mean weight: 110–170 tons) and Maraapunisaurus (mean weight: 80–120 tons) would have easily rivalled
10318-431: The blue whale, with the former even exceeding the blue whale based on its most liberal estimations (240 tons), although these estimates are based on even more fragmentary specimens that had disintegrated by the time those estimates were made. The International Whaling Commission (IWC) whaling database reports 88 individuals longer than 30 meters (98 ft), including one of 33 meters (108 ft), but problems with how
10452-425: The brain (which itself is a fused cluster of segmental ganglia from the rostral metameres ). Molecular markers known as conserved signature indels (CSIs) in protein sequences have been identified and provide distinguishing criteria for the vertebrate subphylum. Specifically, 5 CSIs in the following proteins: protein synthesis elongation factor-2 , eukaryotic translation initiation factor 3 , adenosine kinase and
10586-408: 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
10720-456: The dark sea floor consume organic matter produced through chemosynthesis (via oxidizing inorganic compounds such as hydrogen sulfide ) by archaea and bacteria . Animals evolved in the sea. Lineages of arthropods colonised land around the same time as land plants , probably between 510 and 471 million years ago during the Late Cambrian or Early Ordovician . Vertebrates such as
10854-551: The demise of virtually all jawless fishes save for lampreys and hagfishes, 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 led a lineage of sarcopterygii to leave water, eventually establishing themselves as terrestrial tetrapods in
10988-408: The developmental phases, the fetus is located where the embryonic and fetal phases converge. This fetus is the youngest gestational age of the specimen recorded. Blue whales live around 80–90 years or more. Scientists look at a blue whale's earwax or ear plug to estimate its age. Each year, a light and dark layer of wax is laid corresponding with fasting during migration and feeding time. Each set
11122-407: 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 enlarged clusters in the head , which give rise to a brain . A slight swelling of the anterior end of the nerve cord
11256-450: The earliest times, and are frequently featured in mythology , religion , arts , literature , heraldry , politics , and sports . The word animal comes from the Latin noun animal of the same meaning, which is itself derived from Latin animalis 'having breath or soul'. The biological definition includes all members of the kingdom Animalia. In colloquial usage, the term animal
11390-411: The early 1960s to the early 21st century. The frequency of pygmy blue whales in the Antarctic has decreased by a few tenths of a hertz every year starting in 2002. It is possible that as blue whale populations recover from whaling, there is increasing sexual selection pressure (i.e., a lower frequency indicates a larger body size). The only known natural predator to blue whales is the orca , although
11524-401: The endoskeleton is of cartilage and the vertebral column consists of mostly vertebrae of cartilage, without vertebral centrums , supported by the retained notochord. Most vertebrates are aquatic and carry out gas exchange via gills . The gills are carried right behind the head, bordering the posterior margins of a series of crescentic openings from the pharynx to the outside. Each gill
11658-574: The family Balaenopteridae . A 2018 analysis estimates that the Balaenopteridae family diverged from other families in between 10.48 and 4.98 million years ago during the late Miocene . The earliest discovered anatomically modern blue whale is a partial skull fossil from southern Italy identified as B. cf. musculus , dating to the Early Pleistocene , roughly 1.5–1.25 million years ago. The Australian pygmy blue whale diverged during
11792-481: The first gill arch pair evolved into the jointed jaws and form an additional oral cavity ahead of the pharynx . Research also suggests that the sixth branchial arch contributed to the formation of the vertebrate shoulder, which separated the head as a distinct part of the body. In amphibians and some primitive bony fishes, the larvae bear external gills , branching off from the gill arches. These are reduced in adulthood, their respiratory function taken over by
11926-565: The first hierarchical biological classification for animals in 1758 with his Systema Naturae , which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous with Animalia) and the Protozoa , single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics , which are effective at demonstrating
12060-448: The formation of complex structures possible. This may be calcified, forming structures such as shells , bones , and spicules . In contrast, the cells of other multicellular organisms (primarily algae, plants, and fungi ) are held in place by cell walls, and so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions , gap junctions , and desmosomes . With few exceptions—in particular,
12194-520: The fossil record, rather than showing that all these animals appeared simultaneously. That view is supported by the discovery of Auroralumina attenboroughii , the earliest known Ediacaran crown-group cnidarian (557–562 mya, some 20 million years before the Cambrian explosion) from Charnwood Forest , England. It is thought to be one of the earliest predators , catching small prey with its nematocysts as modern cnidarians do. Some palaeontologists have suggested that animals appeared much earlier than
12328-721: The giant single-celled protist Gromia sphaerica , so the Tonian trace fossils may not indicate early animal evolution. Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals. Objects such as sediment-filled tubes that resemble trace fossils of the burrows of wormlike animals have been found in 1.2 gya rocks in North America, in 1.5 gya rocks in Australia and North America, and in 1.7 gya rocks in Australia. Their interpretation as having an animal origin
12462-420: 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 embryonic dorsal nerve cord (which then flattens into a neural plate before folding and fusing over into
12596-399: 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 . The higher functions of the vertebrate CNS are highly centralized towards the brain (particularly the forebrain), while the invertebrate CNS is significantly more decentralized with the segmental ganglia having substantial neural autonomy independent of
12730-415: The harvest of a female blue whale, Messrs. Irvin and Johnson collected a fetus that is now 70% preserved and used for educational purposes. The fetus was collected in 1922, so some shrinkage may have occurred, making visualization of some features fairly difficult. However, due to this collection researchers now know that the external anatomy of a Blue whale fetus is approximately 133 mm. Along with during
12864-507: The heart of a stranded North Atlantic blue whale was 180 kg (400 lb), the largest known in any animal. The record-holder blue whale was recorded at 173 tonnes (190 short tons ), with estimates of up to 199 tonnes (220 short tons ). In 2024, Motani and Pyenson calculated the body mass of blue whales at different lengths, compiling records of their sizes from previous academic literatures and using regression analyses and volumetric analyses. A 25 metres (82 ft) long individual
12998-461: The impact of man-made threats. However, researchers will be able to know more when lifetime chemical profiles are accessible. The genus name, Balaenoptera , means winged whale, while the species name, musculus , could mean "muscle" or a diminutive form of "mouse", possibly a pun by Carl Linnaeus when he named the species in Systema Naturae . One of the first published descriptions of
13132-472: The injured whale escaped after five hours. Four more blue whales were documented as being chased by a group of orcas between 1982 and 2003. The first documented predation event by orcas occurred in September 2003, when a group of orcas in the Eastern Tropical Pacific was encountered feeding on a recently killed blue whale calf. In March 2014, a commercial whale watch boat operator recorded an incident involving
13266-442: The internal gills proper in fishes and by cutaneous respiration in most amphibians. While some amphibians such as axolotl retain the external gills into adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods , who evolved lungs (which are homologous to swim bladders ) to breathe air. While the more specialized terrestrial vertebrates lack gills,
13400-441: The larvae feed on the hosts' living tissues, killing them in the process, but the adults primarily consume nectar from flowers. Other animals may have very specific feeding behaviours , such as hawksbill sea turtles which mainly eat sponges . Most animals rely on biomass and bioenergy produced by plants and phytoplanktons (collectively called producers ) through photosynthesis . Herbivores, as primary consumers , eat
13534-666: The levels of stressed individuals, it gave a closer look to the reasoning behind their diet and behavioral changes. Blue whales generally reach sexual maturity at 8–10 years. In the Northern Hemisphere, the length at which they reach maturity is 21–23 meters (69–75 ft) for females and 20–21 meters (66–69 ft) for males. In the Southern Hemisphere, the length of maturity is 23–24 meters (75–79 ft) and 22 meters (72 ft) for females and males respectively. Male pygmy blue whales average 18.7 meters (61.4 ft) at sexual maturity. Female pygmy blue whales are 21.0–21.7 meters (68.9–71.2 ft) in length and roughly 10 years old at
13668-459: 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 phylogenetics , the relationships between animals are illustrated as a hierarchy known as a phylogenetic tree . The cladogram below is based on studies compiled by Philippe Janvier and others for
13802-520: The measurements were taken suggest that any longer than 30.5 meters (100 ft) are suspect. The Discovery Committee reported lengths up to 31 meters (102 ft). The longest scientifically measured individual blue whale was 30 meters (98 ft) from rostrum tip to tail notch. Female blue whales are larger than males. Hydrodynamic models suggest a blue whale could not exceed 33 metres (108 ft) because of metabolic and energy constraints. The average length of sexually mature female blue whales
13936-748: The most extreme cold deserts of continental Antarctica . The blue whale ( Balaenoptera musculus ) is the largest animal that has ever lived, weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long. The largest extant terrestrial animal is the African bush elephant ( Loxodonta africana ), weighing up to 12.25 tonnes and measuring up to 10.67 metres (35.0 ft) long. The largest terrestrial animals that ever lived were titanosaur sauropod dinosaurs such as Argentinosaurus , which may have weighed as much as 73 tonnes, and Supersaurus which may have reached 39 meters. Several animals are microscopic; some Myxozoa ( obligate parasites within
14070-620: The oldest animal phylum and forming a sister clade to all other animals. Despite their morphological dissimilarity with all other animals, genetic evidence suggests sponges may be more closely related to other animals than the comb jellies are. Sponges lack the complex organization found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues, unlike all other animals. They typically feed by drawing in water through pores, filtering out small particles of food. The comb jellies and Cnidaria are radially symmetric and have digestive chambers with
14204-525: The origins of animals to unicellular ancestors, providing the external phylogeny shown in the cladogram. Uncertainty of relationships is indicated with dashed lines. Holomycota (inc. fungi) [REDACTED] Ichthyosporea [REDACTED] Pluriformea [REDACTED] Filasterea [REDACTED] [REDACTED] [REDACTED] The most basal animals, the Porifera , Ctenophora , Cnidaria , and Placozoa , have body plans that lack bilateral symmetry . Their relationships are still disputed;
14338-519: The plant material directly to digest and absorb the nutrients, while carnivores and other animals on higher trophic levels indirectly acquire the nutrients by eating the herbivores or other animals that have eaten the herbivores. Animals oxidize carbohydrates , lipids , proteins and other biomolecules, which allows the animal to grow and to sustain basal metabolism and fuel other biological processes such as locomotion . Some benthic animals living close to hydrothermal vents and cold seeps on
14472-420: The presence of a cranium , or skull. The vertebrates make up the subphylum Vertebrata with some 65,000 species in the phylum Chordata . The vertebrates include mammals , birds , amphibians , and various classes of reptiles and fish . Classes of fish include the jawless Agnatha , and the jawed Gnathostomata . The jawed fish include both the cartilaginous fish and the bony fish . Bony fish include
14606-702: The rate of fatal attacks by orcas is unknown. Photograph-identification studies of blue whales have estimated that a high proportion of the individuals in the Gulf of California have rake-like scars, indicative of encounters with orcas. Off southeastern Australia , 3.7% of blue whales photographed had rake marks and 42.1% of photographed pygmy blue whales off Western Australia had rake marks. Documented predation by orcas has been rare. A blue whale mother and calf were first observed being chased at high speeds by orcas off southeastern Australia. The first documented attack occurred in 1977 off southwestern Baja California, Mexico , but
14740-539: The relationships between the Olfactores (vertebrates and tunicates) and the Cephalochordata. Amphioxiformes (lancelets) [REDACTED] Tunicata /Urochordata ( sea squirts , salps , larvaceans ) [REDACTED] Vertebrata [REDACTED] Vertebrates originated during the Cambrian explosion , which saw a rise in organism diversity. The earliest known vertebrates belongs to
14874-511: The results are pending independent testing and verification of the samples. Because the International Whaling Commission classified blue whales as a "Protection Stock", trading their meat is illegal, and the kill is an infraction that must be reported. Blue-fin hybrids have been detected from genetic analysis of whale meat samples taken from Japanese markets. Blue-fin whale hybrids are capable of being fertile. Molecular tests on
15008-639: The seabed. 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. 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
15142-554: The separation of the northern and southern populations. Despite their smaller size, fin whales have similar cruising and sprinting speeds to blue whales, which would allow fin males to complete courtship chases with blue females. There is a reference to a humpback–blue whale hybrid in the South Pacific , attributed to marine biologist Michael Poole. At least four subspecies of blue whale are recognized, some of which are divided into population stocks or "management units". They have
15276-731: The sister group to all other animals could be the Porifera or the Ctenophora, both of which lack hox genes , which are important for body plan development . Hox genes are found in the Placozoa, Cnidaria, and Bilateria. 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived 650 million years ago in the Precambrian . 25 of these are novel core gene groups, found only in animals; of those, 8 are for essential components of
15410-407: The smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova . These fuse to form zygotes , which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form
15544-504: The sound source and the availability of prey. The potential impacts of pollutants on blue whales is unknown. However, because blue whales feed low on the food chain , there is a lesser chance for bioaccumulation of organic chemical contaminants. Analysis of the earwax of a male blue whale killed by a collision with a ship off the coast of California showed contaminants like pesticides, flame retardants, and mercury. Reconstructed persistent organic pollutant (POP) profiles suggested that
15678-526: The southern hemisphere. Data from this study, based on whales collected in the 1965/1966 whaling season, shows that both the maximum and mean body length of Chilean blue whales lies between these values in pygmy and Antarctic blue whales. Data also indicates a potential difference in snout-eye measurements between the three, and a significant difference in fluke-anus length between the Chilean population and pygmy blue whales. This further confirms Chilean blue whales as
15812-498: The species Cocconeis ceticola and the genera Navicola , which are normally removed when the whales enter warmer waters. Other external parasites include barnacles such as Coronula diadema , Coronula reginae , and Cryptolepas rhachianecti , which latch on their skin deep enough to leave behind a pit if removed. Whale lice species make their home in cracks of the skin and are relatively harmless. The copepod species Pennella balaenopterae digs in and attaches itself to
15946-523: The species was particularly high in the Antarctic, with 350,000–360,000 whales taken in the first half of the 20th century. In addition, 11,000 North Atlantic whales (mostly around Iceland) and 9,500 North Pacific whales were killed during the same period. The International Whaling Commission banned all hunting of blue whales in 1966 and gave them worldwide protection. However, the Soviet Union continued to illegally hunt blue whales and other species up until
16080-517: The species. Whalers sometimes referred to them as "sulphur bottom" whales, as the bellies of some individuals are tinged with yellow. This tinge is due to a coating of huge numbers of diatoms . ( Herman Melville briefly refers to "sulphur bottom" whales in his novel Moby-Dick . ) Minke whale B. musculus ( blue whale ) B. borealis ( sei whale ) Eschrichtius robustus ( gray whale ) B. physalus ( fin whale ) Megaptera novaeangliae ( humpback whale ) Blue whales are rorquals in
16214-474: The sponges and placozoans —animal bodies are differentiated into tissues . These include muscles , which enable locomotion, and nerve tissues , which transmit signals and coordinate the body. Typically, there is also an internal digestive chamber with either one opening (in Ctenophora, Cnidaria, and flatworms) or two openings (in most bilaterians). Nearly all animals make use of some form of sexual reproduction. They produce haploid gametes by meiosis ;
16348-411: The structure at the base of the tree (dashed lines). Porifera [REDACTED] Ctenophora [REDACTED] Placozoa [REDACTED] Cnidaria [REDACTED] Xenacoelomorpha [REDACTED] Ambulacraria [REDACTED] Chordata [REDACTED] Ecdysozoa [REDACTED] Spiralia [REDACTED] An alternative phylogeny, from Kapli and colleagues (2021), proposes
16482-511: The subsequent Ediacaran period in what is known as the Avalon explosion . Earlier evidence of animals is still controversial; the sponge -like organism Otavia has been dated back to the Tonian period at the start of the Neoproterozoic , but its identity as an animal is heavily contested. Nearly all modern animal phyla became clearly established in the fossil record as marine species during
16616-632: 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
16750-551: The thickest patches. This provides them enough energy for everyday activities while storing additional energy necessary for migration and reproduction. Due to their size, Blue whales have larger energetic demands than most animals resulting in their need for this specific feeding habit. Blue whales have to engulf densities greater than 100 krill/m to maintain the cost of lunge feeding. They can consume 34,776–1,912,680 kilojoules (8,312–457,141 kcal) from one mouthful of krill, which can provide up to 240 times more energy than used in
16884-467: The total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011. 3,000–6,500 4,000–25,000 Evidence of animals is found as long ago as the Cryogenian period. 24-Isopropylcholestane (24-ipc) has been found in rocks from roughly 650 million years ago; it
17018-401: 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,
17152-410: The vertebral column. The vertebral column typically continues beyond the rear orifice ( anus , or cloaca ) to form an elongated tail . Some vertebrates evolved to become tailless with only a vestigial coccyx . A dorsal nerve cord , which folds and fuses into a hollow neural tube during embryonic development and eventually gives rise to the brain and spinal cord , runs more dorsally to
17286-399: The water out through their baleen plates with pressure from the throat pouch and tongue, and swallow the remaining krill. Blue whales have been recorded making 180° rolls during lunge-feeding, possibly allowing them to search the prey field and find the densest patches. While pursuing krill patches, blue whales maximize their calorie intake by increasing the number of lunges while selecting
17420-414: The water, which historically earned them the nickname "sulphur bottom". The male blue whale has the largest penis in the animal kingdom, at around 3 m (9.8 ft) long and 12 in (30 cm) wide. The blue whale is the largest animal known ever to have existed. Some studies have estimated that certain shastasaurid ichthyosaurs and the ancient whale Perucetus could have rivalled
17554-411: The world, with dives of 10.7 minutes on average, and a hypothesized dive depth of about 300 meters. Fecal analysis also found the presence of fish, krill, amphipods , cephalopods , and scyphozoan jellyfish in their diet. Blue whales appear to avoid directly competing with other baleen whales. Different whale species select different feeding spaces and times as well as different prey species. In
17688-689: Was 315 meters (1,033 ft). Their theoretical aerobic dive limit was estimated at 31.2 minutes, however, the longest dive measured was 15.2 minutes. The deepest confirmed dive from a pygmy blue whale was 506 meters (1,660 ft). A blue whale's heart rate can drop to 2 beats per minute (bpm) at deep depths, but upon surfacing, can rise to 37 bpm, which is close to its peak heart rate. The blue whale's diet consists almost exclusively of krill . Blue whales capture krill through lunge feeding; they swim towards them at high speeds as they open their mouths up to 80°. They may engulf 220 metric tons (220 long tons; 240 short tons) of water at one time. They squeeze
17822-403: Was estimated to weigh approximately 101–119 tonnes (111–131 short tons), while a 30 metres (98 ft) long individual was estimated to weigh approximately 184–205 tonnes (203–226 short tons). Considering that the largest blue whale was indeed 33 metres (108 ft) long, they estimated that a blue whale of such length would have weighed approximately 252–273 tonnes (278–301 short tons). During
17956-657: Was found to have been the product of a blue whale mother and a fin whale father. Two live blue-fin whale hybrids have since been documented in the Gulf of St. Lawrence (Canada), and in the Azores (Portugal). DNA tests done in Iceland on a blue whale killed in July 2018 by the Icelandic whaling company Hvalur hf, found that the whale was the offspring of a male fin whale and female blue whale; however,
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