188 relations: Acanthodii, Actinistia, Actinopterygii, Agkistrodon contortrix, Agkistrodon piscivorus, Agnatha, Amniote, Amniotic sac, Amphibian, Anamniotes, Anaspida, Anatomy, Animal, Anus, Asexual reproduction, Basal (phylogenetics), Batoidea, Bird, Black and rufous elephant shrew, Blue whale, Body plan, Brain, Brainstem, Branchial arch, Cambrian, Cambrian explosion, Carboniferous, Cenozoic, Central canal, Central nervous system, Cephalaspidomorphi, Cephalization, Cerebral hemisphere, Chondrichthyes, Chordate, Cladistics, Class (biology), Coelacanth, Conodont, Craniate, Cretaceous, Cyclostome, Devonian, Diapsid, Dinosaur, Dominance (genetics), Dorsal nerve cord, Egg cell, Epicrates maurus, Euteleostomi, ..., Evolution, Evolutionary taxonomy, External gills, Extra-pair copulation, Eye, Fertilisation, Fire salamander, Fish, FishBase, Fitness (biology), Forebrain, Frog, Galeaspida, Ganglion, Gastrointestinal tract, Genetics, Gill, Gnathostomata, Great tit, Hagfish, Haikouichthys, Hermaphrodite, Heterosis, Hindbrain, Holocene, Homologous chromosome, Hyperoartia, Inbreeding, Inbreeding avoidance, Inbreeding depression, Incest, Insect, Institute of Food and Agricultural Sciences, Invertebrate, IUCN Red List, Jaw, Jean-Baptiste Lamarck, Jurassic, Labyrinthodontia, Lamprey, Lancelet, Larva, Larynx, Latin, Lung, Lungfish, Mammal, Mangrove rivulus, Marc Kirschner, Marine vertebrate, McGraw-Hill Education, Meiosis, Mesozoic, Midbrain, Mole salamander, Monophyly, Mutation, Myllokunmingia, Natural History (Pliny), Neontology, Neural crest, New York (state), New York City, Notochord, Ocean sunfish, Onychodontida, Ordovician, Organ (anatomy), Ossicles, Osteichthyes, Osteostraci, Paedophryne amauensis, Palaeospondylus, Paleozoic, Paraphyly, Parareptilia, Peripheral nervous system, Pharynx, Philopatry, Phylogenetic tree, Phylogenetics, Phylum, Physiology, Pituriaspida, Placodermi, Polyploid, Porolepiformes, Prenatal development, Proto-Indo-European language, Pteraspidomorphi, Purple-crowned fairywren, Reptile, Reptile Database, Rhizodontida, Salamander, Saltwater crocodile, Sand lizard, Sarcopterygii, Sauropsida, Selfing, Sexual intercourse, Sexual reproduction, Shark, Sibling, Silurian, Skeletal system of the horse, Skull, Snake, Southern cassowary, Southern pied babbler, Species, Sperm, Spermatozoon, Spider, Spinal cord, Squamata, Squid, Stapes, Stem cell, Sturgeon, Subphylum, Synapsid, Synapsis, Tail, Taxon, Tetrapod, Thelodonti, Therapsid, Thyroid, Triassic, Tristichopteridae, United States Environmental Protection Agency, University of Florida, Vertebra, Vertebral column, Vertebrate, Wiley-Blackwell, Zygote. Expand index (138 more) » « Shrink index
Acanthodii or acanthodians (sometimes called spiny sharks) is a paraphyletic class of extinct teleostome fish, sharing features with both bony fish and cartilaginous fish.
Actinistia is a subclass of mostly fossil lobe-finned fishes.
Actinopterygii, or the ray-finned fishes, constitute a class or subclass of the bony fishes.
Agkistrodon contortrix is a species of venomous snake endemic to Eastern North America, a member of the subfamily Crotalinae (pit vipers).
Agkistrodon piscivorus is a venomous snake, a species of pit viper, found in the southeastern United States.
Agnatha (Greek, "no jaws") is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species.
Amniotes (from Greek ἀμνίον amnion, "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός amnos, "lamb") are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals.
The amniotic sac, commonly called the bag of waters, sometimes the membranes, is the sac in which the fetus develops in amniotes.
Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia.
The anamniotes are an informal group comprising the fishes and the amphibians, the so-called "lower vertebrates", which lay their eggs in water.
Anaspida ("without shield") is an extinct group of primitive jawless vertebrates that lived primarily during the Silurian period, and became extinct soon after the start of the Devonian.
Anatomy (Greek anatomē, “dissection”) is the branch of biology concerned with the study of the structure of organisms and their parts.
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia.
The anus (from Latin anus meaning "ring", "circle") is an opening at the opposite end of an animal's digestive tract from the mouth.
Asexual reproduction is a type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only; it does not involve the fusion of gametes, and almost never changes the number of chromosomes.
In phylogenetics, basal is the direction of the base (or root) of a rooted phylogenetic tree or cladogram.
Batoidea is a superorder of cartilaginous fish commonly known as rays.
Birds, also known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
The black and rufous elephant shrew, (Rhynchocyon petersi) the black and rufous sengi, or the Zanj elephant shrew is one of the 17 species of elephant shrew found only in Africa.
The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whale parvorder, Mysticeti.
A body plan, Bauplan (German plural Baupläne), or ground plan is a set of morphological features common to many members of a phylum of animals.
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.
The brainstem (or brain stem) is the posterior part of the brain, adjoining and structurally continuous with the spinal cord.
Branchial arches, or gill arches, are a series of bony "loops" present in fish, which support the gills.
The Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon.
The Cambrian explosion or Cambrian radiation was an event approximately in the Cambrian period when most major animal phyla appeared in the fossil record.
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period million years ago (Mya), to the beginning of the Permian Period, Mya.
The Cenozoic Era meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and, extending from 66 million years ago to the present day.
The central canal, also known as ependymal canal, is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord.
The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord.
Cephalaspidomorphs are a group of jawless fishes named for Cephalaspis of the osteostracans.
Cephalization is an evolutionary trend in which, over many generations, the mouth, sense organs, and nerve ganglia become concentrated at the front end of an animal, producing a head region.
The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure.
Chondrichthyes (from Greek χονδρ- chondr- 'cartilage', ἰχθύς ichthys 'fish') is a class that contains the cartilaginous fishes: they are jawed vertebrates with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone.
A chordate is an animal belonging to the phylum Chordata; chordates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail, for at least some period of their life cycle.
Christmas is an annual festival commemorating the birth of Jesus Christ,Martindale, Cyril Charles.
The Christmas season, also called the festive season, or the holiday season (mainly in the U.S. and Canada; often simply called the holidays),, is an annually recurring period recognized in many Western and Western-influenced countries that is generally considered to run from late November to early January.
Christmas Eve is the evening or entire day before Christmas Day, the festival commemorating the birth of Jesus.
Christmas traditions vary from country to country.
Cladistics (from Greek κλάδος, cládos, i.e., "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on the most recent common ancestor.
In biological classification, class (classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank.
The coelacanths constitute a now rare order of fish that includes two extant species in the genus Latimeria: the West Indian Ocean coelacanth (Latimeria chalumnae) primarily found near the Comoro Islands off the east coast of Africa and the Indonesian coelacanth (Latimeria menadoensis).
Conodonts (Greek kōnos, "cone", + odont, "tooth") are extinct agnathan chordates resembling eels, classified in the class Conodonta.
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage.
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (mya) to the beginning of the Paleogene Period mya.
Cyclostome is a biological term (from the Greek for "round mouth") used in a few different senses.
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya.
Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period.
Dinosaurs are a diverse group of reptiles of the clade Dinosauria.
Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus.
The dorsal nerve cord is a unique feature to chordates, and it is mainly found in the Vertebrata chordate subphylum.
The egg cell, or ovum (plural ova), is the female reproductive cell (gamete) in oogamous organisms.
Epicrates maurus is a species of non-venomous constrictor, in the family Boinae, found in Amazon region of South America.
Euteleostomi is a successful clade that includes more than 90% of the living species of vertebrates.
Evolution is change in the heritable characteristics of biological populations over successive generations.
Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship (shared descent), progenitor-descendant relationship (serial descent), and degree of evolutionary change.
External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes.
Extra-pair copulation (EPC) is a promiscuous mating behaviour in monogamous species.
Eyes are organs of the visual system.
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, conception, fecundation, syngamy and impregnation, is the fusion of gametes to initiate the development of a new individual organism.
The fire salamander (Salamandra salamandra) is possibly the best-known salamander species in Europe.
Fish are gill-bearing aquatic craniate animals that lack limbs with digits.
FishBase is a global species database of fish species (specifically finfish).
Fitness (often denoted w or ω in population genetics models) is the quantitative representation of natural and sexual selection within evolutionary biology.
In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral-most (forward-most) portion of the brain.
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (Ancient Greek ἀν-, without + οὐρά, tail).
Galeaspida (from Latin, "Helmet shields") is an extinct taxon of jawless marine and freshwater fish.
A ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system and sensory system.
The gastrointestinal tract (digestive tract, digestional tract, GI tract, GIT, gut, or alimentary canal) is an organ system within humans and other animals which takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces.
Genetics is the study of genes, genetic variation, and heredity in living organisms.
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide.
Gnathostomata are the jawed vertebrates.
The great tit (Parus major) is a passerine bird in the tit family Paridae.
Hagfish, the class '''Myxini''' (also known as Hyperotreti), are eel-shaped, slime-producing marine fish (occasionally called slime eels).
Haikouichthys is an extinct genus of craniate (animals with notochords and distinct heads) believed to have lived 525 million years ago, during the Cambrian explosion of multicellular life.
In biology, a hermaphrodite is an organism that has complete or partial reproductive organs and produces gametes normally associated with both male and female sexes.
Heterosis, hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring.
The hindbrain or rhombencephalon is a developmental categorization of portions of the central nervous system in vertebrates.
The Holocene is the current geological epoch.
A couple of homologous chromosomes, or homologs, are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during meiosis.
Hyperoartia or Petromyzontida is a disputed group of vertebrates that includes the modern lampreys and their fossil relatives.
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically.
Inbreeding avoidance, or the inbreeding avoidance hypothesis, is a concept in evolutionary biology that refers to the prevention of the deleterious effects of inbreeding.
Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals.
Incest is sexual activity between family members or close relatives.
Insects or Insecta (from Latin insectum) are hexapod invertebrates and the largest group within the arthropod phylum.
The Institute of Food and Agricultural Sciences (IFAS) is an agriculture, life science, pathogen, and invasive species research facility in Florida affiliated with University of Florida.
Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord.
The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List), founded in 1964, has evolved to become the world's most comprehensive inventory of the global conservation status of biological species.
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food.
Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck, was a French naturalist.
The Jurassic (from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya.
Labyrinthodontia (Greek, "maze-toothed") is an extinct amphibian subclass, which constituted some of the dominant animals of late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago).
Lampreys (sometimes also called, inaccurately, lamprey eels) are an ancient lineage of jawless fish of the order Petromyzontiformes, placed in the superclass Cyclostomata.
The lancelets — also known as amphioxi (singular, amphioxus) consist of about 32 species of fish-like marine chordates in the order Amphioxiformes.
A larva (plural: larvae) is a distinct juvenile form many animals undergo before metamorphosis into adults.
The larynx, commonly called the voice box, is an organ in the top of the neck of tetrapods involved in breathing, producing sound, and protecting the trachea against food aspiration.
Latin (Latin: lingua latīna) is a classical language belonging to the Italic branch of the Indo-European languages.
The lungs are the primary organs of the respiratory system in humans and many other animals including a few fish and some snails.
Lungfish are freshwater rhipidistian fish belonging to the subclass Dipnoi.
Mammals are the vertebrates within the class Mammalia (from Latin mamma "breast"), a clade of endothermic amniotes distinguished from reptiles (including birds) by the possession of a neocortex (a region of the brain), hair, three middle ear bones, and mammary glands.
The mangrove killifish or mangrove rivulus, Kryptolebias marmoratus (syn. Rivulus marmoratus), is a species of fish in the Aplocheilidae family.
Marc W. Kirschner (born February 28, 1945) is an American cell biologist and biochemist and the founding chair of the Department of Systems Biology at Harvard Medical School. His research involves problems in cell and developmental biology, such as the dynamics and function of the cytoskeleton, the regulation of the cell cycle, and the process of signaling in embryos, as well as the evolution of the vertebrate body plan, and applying mathematical approaches to biology.
Marine vertebrates are vertebrates which live in a marine environment.
McGraw-Hill Education (MHE) is a learning science company and one of the "big three" educational publishers that provides customized educational content, software, and services for pre-K through postgraduate education.
Meiosis (from Greek μείωσις, meiosis, which means lessening) is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them.
The Mesozoic Era is an interval of geological time from about.
The midbrain or mesencephalon (from Greek mesos 'middle', and enkephalos 'brain') is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.
The mole salamanders (genus Ambystoma) are a group of advanced salamanders endemic to North America, the only genus in the family Ambystomatidae.
In cladistics, a monophyletic group, or clade, is a group of organisms that consists of all the descendants of a common ancestor.
In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.
Myllokunmingia is a genus of basal chordate from the Lower Cambrian Maotianshan shales of China, thought to be a vertebrate, although this is not conclusively proven.
The Natural History (Naturalis Historia) is a book about the whole of the natural world in Latin by Pliny the Elder, a Roman author and naval commander who died in 79 AD.
Neontology is a part of biology that, in contrast to paleontology, deals with living (or, more generally, recent) organisms.
Neural crest cells are a temporary group of cells unique to chordates of the group Cristozoa that arise from the embryonic ectoderm cell layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia.
New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one.
New Year's Day, also called simply New Year's or New Year, is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
In the Gregorian calendar, New Year's Eve (also known as Old Year's Day or Saint Sylvester's Day in many countries), the last day of the year, is on 31 December which is the seventh day of Christmastide.
New York is a state in the northeastern United States.
The City of New York, often called New York City (NYC) or simply New York, is the most populous city in the United States.
In anatomy, the notochord is a flexible rod made out of a material similar to cartilage.
The ocean sunfish or common mola (Mola mola) is the heaviest known bony fish in the world.
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era.
Organs are collections of tissues with similar functions.
The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body.
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 class Osteostraci ("Bony Shields") is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian.
The Paedophryne amauensis is a species of frogs from Papua New Guinea.
Palaeospondylus gunni ("Gunn's Ancient Vertebrae") is a mysterious, fish-like fossil vertebrate.
The Paleozoic (or Palaeozoic) Era (from the Greek palaios (παλαιός), "old" and zoe (ζωή), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon.
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—monophyletic subgroups.
Parareptilia ("at the side of reptiles") is a subclass or clade of reptiles which is variously defined as an extinct group of primitive anapsids, or a more cladistically correct alternative to Anapsida.
The peripheral nervous system (PNS) is one of the two components of the nervous system, the other part is the central nervous system (CNS).
The pharynx (plural: pharynges) is the part of the throat that is behind the mouth and nasal cavity and above the esophagus and the larynx, or the tubes going down to the stomach and the lungs.
Philopatry is the tendency of an organism to stay in or habitually return to a particular area.
A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the evolutionary relationships among various biological species or other entities—their phylogeny—based upon similarities and differences in their physical or genetic characteristics.
In biology, phylogenetics (Greek: φυλή, φῦλον – phylé, phylon.
In biology, a phylum (plural: phyla) is a level of classification or taxonomic rank below Kingdom and above Class.
Physiology is the scientific study of normal mechanisms, and their interactions, which work within a living system.
The Pituriaspida ("Pituri Shield") are a small group of extinct armored jawless fishes with tremendous nose-like rostrums, which lived in the marine, deltaic environments of Middle Devonian Australia (about 390 Ma).
Placodermi (from the Greek πλάξ.
Polyploid cells and organisms are those containing more than two paired (homologous) sets of chromosomes.
Porolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period (about 416 to 359 million years ago).
Prenatal development is the process in which an embryo and later fetus develops during gestation.
Proto-Indo-European (PIE) is the linguistic reconstruction of the hypothetical common ancestor of the Indo-European languages, the most widely spoken language family in the world.
Pteraspidomorphi is an extinct class of early jawless fish.
The purple-crowned fairywren (Malurus coronatus) is a species of bird in the Australasian wren family, Maluridae.
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives.
The Reptile Database is a scientific database that collects taxonomic information on all living reptile species (i.e. no fossil species such as dinosaurs).
Rhizodonts (order Rhizodontida) are an extinct group of predatory tetrapodomorph fishes known from many areas of the world from the Givetian through to the Pennsylvanian - the earliest known species is about 377 million years ago (Mya), the latest around 310 Mya.
Salamanders are a group of amphibians typically characterized by a lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults.
The saltwater crocodile (Crocodylus porosus), also known as the estuarine crocodile, Indo-Pacific crocodile, marine crocodile, sea crocodile or informally as saltie, is the largest of all living reptiles, as well as the largest riparian predator in the world.
The sand lizard (Lacerta agilis) is a lacertid lizard distributed across most of Europe and eastwards to Mongolia.
The Sarcopterygii or lobe-finned fish (from Greek σαρξ sarx, flesh, and πτερυξ pteryx, fin) – sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek κροσσός krossos, fringe) – constitute a clade (traditionally a class or subclass) of the bony fish, though a strict cladistic view includes the terrestrial vertebrates.
Sauropsida ("lizard faces") is a group of amniotes that includes all existing birds and other reptiles as well as their fossil ancestors and other extinct relatives.
Selfing or self-fertilization is the union of male and female gametes and/or nuclei from same haploid, diploid, or polyploid organism.
Sexual intercourse (or coitus or copulation) is principally the insertion and thrusting of the penis, usually when erect, into the vagina for sexual pleasure, reproduction, or both.
Sexual reproduction is a form of reproduction where two morphologically distinct types of specialized reproductive cells called gametes fuse together, involving a female's large ovum (or egg) and a male's smaller sperm.
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head.
A sibling is one of two or more individuals having one or both parents in common.
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (Mya), to the beginning of the Devonian Period, Mya.
The skeletal system of the horse has three major functions in the body.
The skull is a bony structure that forms the head in vertebrates.
Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes.
The southern cassowary (Casuarius casuarius) also known as double-wattled cassowary, Australian cassowary or two-wattled cassowary, is a large flightless black bird.
The southern pied babbler (Turdoides bicolor) is a species of bird in the Leiothrichidae family, found in dry savannah of Botswana, Namibia, South Africa, and Zimbabwe.
In biology, a species is the basic unit of classification and a taxonomic rank, as well as a unit of biodiversity, but it has proven difficult to find a satisfactory definition.
Sperm is the male reproductive cell and is derived from the Greek word (σπέρμα) sperma (meaning "seed").
A spermatozoon (pronounced, alternate spelling spermatozoön; plural spermatozoa; from σπέρμα "seed" and ζῷον "living being") is a motile sperm cell, or moving form of the haploid cell that is the male gamete.
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom.
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column.
Squamata is the largest order of reptiles, comprising lizards, snakes and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles.
Squid are cephalopods of the two orders Myopsida and Oegopsida, which were formerly regarded as two suborders of the order Teuthida, however recent research shows Teuthida to be paraphyletic.
The stapes or stirrup is a bone in the middle ear of humans and other mammals which is involved in the conduction of sound vibrations to the inner ear.
Stem cells are biological cells that can differentiate into other types of cells and can divide to produce more of the same type of stem cells.
Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae.
In zoological nomenclature, a subphylum is a taxonomic rank below the rank of phylum.
Synapsids (Greek, 'fused arch'), synonymous with theropsids (Greek, 'beast-face'), are a group of animals that includes mammals and every animal more closely related to mammals than to other living amniotes.
Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis.
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso.
In biology, a taxon (plural taxa; back-formation from taxonomy) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit.
The superclass Tetrapoda (from Greek: τετρα- "four" and πούς "foot") contains the four-limbed vertebrates known as tetrapods; it includes living and extinct amphibians, reptiles (including dinosaurs, and its subgroup birds) and mammals (including primates, and all hominid subgroups including humans), as well as earlier extinct groups.
Thelodonti (from Greek: "feeble teeth")Maisey, John G., Craig Chesek, and David Miller.
Therapsida is a group of synapsids that includes mammals and their ancestors.
The thyroid gland, or simply the thyroid, is an endocrine gland in the neck, consisting of two lobes connected by an isthmus.
The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period Mya.
Tristichopterids (Tristichopteridae) were a diverse and successful group of tetrapodomorph fishes living throughout the Middle and Late Devonian.
The Environmental Protection Agency is an independent agency of the United States federal government for environmental protection.
The University of Florida (commonly referred to as Florida or UF) is an American public land-grant, sea-grant, and space-grant research university on a campus in Gainesville, Florida.
In the vertebrate spinal column, each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, the proportions of which vary according to the segment of the backbone and the species of vertebrate.
The vertebral column, also known as the backbone or spine, is part of the axial skeleton.
Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones).
Wiley-Blackwell is the international scientific, technical, medical, and scholarly publishing business of John Wiley & Sons.
A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke") is a eukaryotic cell formed by a fertilization event between two gametes.
2018 has been designated as the third International Year of the Reef by the International Coral Reef Initiative.
2019 (MMXIX) will be a common year starting on Tuesday of the Gregorian calendar, the 2019th year of the Common Era (CE) and Anno Domini (AD) designations, the 19th year of the 3rd millennium, the 19th year of the 21st century, and the 10th and last year of the 2010s decade.
Animals with backbone, Evolution of vertebrates, Reproductive systems of vertebrates, Subphylum vertebrata, Subphylum vertebrate, Vertabrate, Vertebrata, Vertebrate animals, Vertebrate biology, Vertebrate evolution, Vertebrate viruses, Vertebrates, Vertibrate.