171 relations: Abdomen, Acanthocephala, Acari, Acoelomorpha, Alpheidae, Anastomosis, Animal, Annelid, Anthozoa, Aplysia, Aquatic biomonitoring, Arachnid, Arthropod, Aschelminth, Barnacle, Bee, Body plan, Brachiopod, Breathing, Brittle star, Bryozoa, Caenorhabditis elegans, Carbon dioxide, Carl Linnaeus, Cerata, Charismatic megafauna, Choanoflagellate, Chordate, Circumscription (taxonomy), Cladogram, Clam, Cnidaria, Coelenterata, Colony (biology), Columbia Encyclopedia, Convergent evolution, Copepod, Coral, Crab, Crinoid, Crustacean, Ctenophora, Diffusion, Diploblasty, Drosophila melanogaster, Earthworm, Ecdysis, Echinoderm, Egg cell, Entoprocta, ..., Eusociality, Exoskeleton, Family (biology), Fiddler crab, Fish, Flatworm, Gametogonium, Gastropoda, Gastrotrich, Gene, Genetic linkage, Genome, Geometry, Gill, Glaucus atlanticus, Gnathostomulid, Grasshopper, Head, Helix, Hemichordate, Hemolymph, Hermit crab, Hirudo medicinalis, Homology (biology), Horseshoe crab, Host (biology), Infusoria, Insect, International Union for Conservation of Nature, Intron, Invertebrate paleontology, Invertebrate zoology, IUCN Red List, Jean-Baptiste Lamarck, Jellyfish, Kingdom (biology), Kinorhyncha, Laity, Lancelet, Leech, Libbie Hyman, Limnognathia, Loricifera, Marine invertebrates, Meiosis, Metabolism, Model organism, Mollusca, Monogenea, Moulting, Multicellular organism, National Museum of Natural History (France), Nematode, Nemertea, Neontology, Neuron, New York City, Notochord, Onychophora, Order (biology), Organ (anatomy), Oxygen, Pain in invertebrates, Pangolin, Paraphyly, Passalidae, Phanerozoic, Phoronid, Phylum, Pneumostome, Polyopisthocotylea, Polyp, Priapulida, Protozoa, Radiata, Respiratory system, Rotifer, Science (journal), Sea anemone, Sea cucumber, Sea snail, Sea urchin, Sessility (motility), Sexual reproduction, Sipuncula, Slug, Snail, Spermatozoon, Spider, Spiracle, Sponge, Squid, Starfish, Starlet sea anemone, Subphylum, Symbion, Symmetry in biology, Taenidia, Tardigrade, Taxon, Taxonomic rank, Taxonomy (biology), Terrestrial animal, Thorax, Thrips, Tonian, Tortoise, Trace fossil, Tracheole, Triploblasty, Trochophore, Tunicate, Vermes, Vertebral column, Vertebrate, VHS, Water, Worm, Xenoturbella, Xiphosura, Zygote. Expand index (121 more) » « Shrink index
The abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates.
Acanthocephala (Greek ἄκανθος, akanthos, thorn + κεφαλή, kephale, head) is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host.
Acari (or Acarina) are a taxon of arachnids that contains mites and ticks.
Acoelomorpha is a subphylum of very simple and small soft-bodied animals with planula-like features which live in marine or brackish waters.
Alpheidae is a family of caridean snapping shrimp characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound.
An anastomosis (plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams.
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia.
The annelids (Annelida, from Latin anellus, "little ring"), also known as the ringed worms or segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches.
Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals, soft corals and gorgonians.
Aplysia is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are one clade of large sea slugs, marine gastropod mollusks.
Aquatic biomonitoring is the science of inferring the ecological condition of rivers, lakes, streams, and wetlands by examining the organisms that live there.
Arachnids are a class (Arachnida) of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata.
An arthropod (from Greek ἄρθρον arthron, "joint" and πούς pous, "foot") is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and paired jointed appendages.
The Aschelminthes (also known as Aeschelminthes "Nemathelminthes" "Nematodes"), closely associated with the Platyhelminthes, are an obsolete phylum of pseudocoelomate and other similar animals that are no longer considered closely related and have been promoted to phyla in their own right.
A barnacle is a type of arthropod constituting the infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters.
Bees are flying insects closely related to wasps and ants, known for their role in pollination and, in the case of the best-known bee species, the European honey bee, for producing honey and beeswax.
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.
Brachiopods, phylum Brachiopoda, are a group of lophotrochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs.
Breathing (or respiration, or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish.
Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of aquatic invertebrate animals.
Caenorhabditis elegans is a free-living (not parasitic), transparent nematode (roundworm), about 1 mm in length, that lives in temperate soil environments.
Carbon dioxide (chemical formula) is a colorless gas with a density about 60% higher than that of dry air.
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after his ennoblement as Carl von LinnéBlunt (2004), p. 171.
Ceras, plural Cerata, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine opisthobranch gastropod mollusks in the clade Aeolidida.
Charismatic megafauna are large animal species with widespread popular appeal, which are often used by environmental activists to achieve environmentalist goals.
The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals.
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.
In biological taxonomy, circumscription is the definition of a taxon, that is, a group of organisms.
A cladogram (from Greek clados "branch" and gramma "character") is a diagram used in cladistics to show relations among organisms.
Clam is a common name for several kinds of bivalve molluscs.
Cnidaria is a phylum containing over 10,000 species of animals found exclusively in aquatic (freshwater and marine) environments: they are predominantly marine species.
Coelenterata is an obsolete term encompassing the animal phyla Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies) and Ctenophora (comb jellies).
In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another.
The Columbia Encyclopedia is a one-volume encyclopedia produced by Columbia University Press and in the last edition, sold by the Gale Group.
Convergent evolution is the independent evolution of similar features in species of different lineages.
Copepods (meaning "oar-feet") are a group of small crustaceans found in the sea and nearly every freshwater habitat.
Corals are marine invertebrates in the class Anthozoa of phylum Cnidaria.
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) (translit.
Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata).
Crustaceans (Crustacea) form a large, diverse arthropod taxon which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice, and barnacles.
Ctenophora (singular ctenophore, or; from the Greek κτείς kteis 'comb' and φέρω pherō 'to carry'; commonly known as comb jellies) is a phylum of invertebrate animals that live in marine waters worldwide.
Diffusion is the net movement of molecules or atoms from a region of high concentration (or high chemical potential) to a region of low concentration (or low chemical potential) as a result of random motion of the molecules or atoms.
Diploblasty is a condition of the blastula in which there are two primary germ layers: the ectoderm and endoderm.
Drosophila melanogaster is a species of fly (the taxonomic order Diptera) in the family Drosophilidae.
An earthworm is a tube-shaped, segmented worm found in the phylum Annelida.
Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa.
Echinoderm is the common name given to any member of the phylum Echinodermata (from Ancient Greek, ἐχῖνος, echinos – "hedgehog" and δέρμα, derma – "skin") of marine animals.
The egg cell, or ovum (plural ova), is the female reproductive cell (gamete) in oogamous organisms.
Entoprocta, whose name means "anus inside", is a phylum of mostly sessile aquatic animals, ranging from long.
Eusociality (from Greek εὖ eu "good" and social), the highest level of organization of animal sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups.
An exoskeleton (from Greek έξω, éxō "outer" and σκελετός, skeletós "skeleton") is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human.
In biological classification, family (familia, plural familiae) is one of the eight major taxonomic ranks; it is classified between order and genus.
A fiddler crab, sometimes known as a calling crab, may be any of approximately 100 species of semi-terrestrial marine crabs which make up the genus Uca.
Fish are gill-bearing aquatic craniate animals that lack limbs with digits.
The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates.
Gametogonium (plural gametogonia) are stem cells for gametes located within the gonads.
The gastropods, more commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca, called Gastropoda.
The gastrotrichs (phylum Gastrotricha), commonly referred to as hairybacks, are a group of microscopic (0.06-3.0 mm), worm-like, pseudocoelomate animals, and are widely distributed and abundant in freshwater and marine environments.
In biology, a gene is a sequence of DNA or RNA that codes for a molecule that has a function.
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.
In the fields of molecular biology and genetics, a genome is the genetic material of an organism.
Geometry (from the γεωμετρία; geo- "earth", -metron "measurement") is a branch of mathematics concerned with questions of shape, size, relative position of figures, and the properties of space.
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide.
Glaucus atlanticus (common names include the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug) is a species of small, blue sea slug, a pelagic aeolid nudibranch, a shell-less gastropod mollusk in the family Glaucidae.
Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals.
Grasshoppers are insects of the suborder Caelifera within the order Orthoptera, which includes crickets and their allies in the other suborder Ensifera.
A head is the part of an organism which usually includes the eyes, ears, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste, respectively.
A helix, plural helixes or helices, is a type of smooth space curve, i.e. a curve in three-dimensional space.
Hemichordata is a phylum of marine deuterostome animals, generally considered the sister group of the echinoderms.
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod body remaining in direct contact with the animal's tissues.
Hermit crabs are decapod crustaceans of the superfamily Paguroidea.
Hirudo medicinalis, the European medicinal leech, is one of several species of leeches used as "medicinal leeches".
In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa.
Horseshoe crabs are marine and brackish water arthropods of the family Limulidae, suborder Xiphosurida, and order Xiphosura.
In biology and medicine, a host is an organism that harbours a parasitic, a mutualistic, or a commensalist guest (symbiont), the guest typically being provided with nourishment and shelter.
Infusoria is a collective term for minute aquatic creatures such as ciliates, euglenoids, protozoa, unicellular algae and small invertebrates that exist in freshwater ponds.
Insects or Insecta (from Latin insectum) are hexapod invertebrates and the largest group within the arthropod phylum.
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natural resources.
An intron is any nucleotide sequence within a gene that is removed by RNA splicing during maturation of the final RNA product.
Invertebrate paleontology (also spelled Invertebrate palaeontology) is sometimes described as Invertebrate paleozoology or Invertebrate paleobiology.
Invertebrate zoology is the subsystem of zoology that consists of the study of invertebrates, animals without a backbone (a structure which is found only in fish, amphibians, reptiles, birds and mammals.) Invertebrates are a vast and very diverse group of animals that includes sponges, echinoderms, tunicates, numerous different phyla of worms, molluscs, arthropods and many additional phyla.
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.
Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck, was a French naturalist.
Jellyfish or sea jelly is the informal common name given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria.
In biology, kingdom (Latin: regnum, plural regna) is the second highest taxonomic rank, just below domain.
Kinorhyncha (I move, ῥύγχος "snout") is a phylum of small (1 mm or less) marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos.
A layperson (also layman or laywoman) is a person who is not qualified in a given profession and/or does not have specific knowledge of a certain subject.
The lancelets — also known as amphioxi (singular, amphioxus) consist of about 32 species of fish-like marine chordates in the order Amphioxiformes.
Leeches are segmented parasitic or predatory worm-like animals that belong to the phylum Annelida and comprise the subclass Hirudinea.
Libbie Henrietta Hyman (December 6, 1888 – August 3, 1969), was a U.S. zoologist.
Limnognathia maerski is a microscopic platyzoan animal, discovered living in homothermic springs on Disko Island, Greenland in 1994, that has variously been assigned as a class or subphylum in the phylum Gnathifera or as a phylum in a Gnathifera superphylum, named Micrognathozoa.
Loricifera (from Latin, lorica, corselet (armour) + ferre, to bear) is a phylum of very small to microscopic marine cycloneuralian sediment-dwelling animals with 37 described species, in nine genera.
Marine invertebrates are the invertebrates that live in marine habitats.
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.
Metabolism (from μεταβολή metabolē, "change") is the set of life-sustaining chemical transformations within the cells of organisms.
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms.
Mollusca is a large phylum of invertebrate animals whose members are known as molluscs or mollusksThe formerly dominant spelling mollusk is still used in the U.S. — see the reasons given in Gary Rosenberg's.
Monogeneans are a group of ectoparasites commonly found on the skin, gills, or fins of fish.
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle.
Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.
The French National Museum of Natural History, known in French as the (abbreviation MNHN), is the national natural history museum of France and a grand établissement of higher education part of Sorbonne Universities.
The nematodes or roundworms constitute the phylum Nematoda (also called Nemathelminthes).
Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms".
Neontology is a part of biology that, in contrast to paleontology, deals with living (or, more generally, recent) organisms.
A neuron, also known as a neurone (British spelling) and nerve cell, is an electrically excitable cell that receives, processes, and transmits information through electrical and chemical signals.
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.
Onychophora (from Ancient Greek, onyches, "claws"; and pherein, "to carry"), commonly known as velvet worms (due to their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, Peripatus), is a phylum of elongate, soft-bodied, many-legged panarthropods.
In biological classification, the order (ordo) is.
Organs are collections of tissues with similar functions.
Oxygen is a chemical element with symbol O and atomic number 8.
Pain in invertebrates is a contentious issue.
Pangolins or scaly anteaters are mammals of the order Pholidota (from the Greek word φολῐ́ς, "horny scale").
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.
Passalidae is a family of beetles known variously as "bessbugs", "bess beetles", "betsy beetles" or "horned passalus beetles".
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed.
Phoronids (scientific name Phoronida, sometimes called horseshoe worms) are a small phylum of marine animals that filter-feed with a lophophore (a "crown" of tentacles), and build upright tubes of chitin to support and protect their soft bodies.
In biology, a phylum (plural: phyla) is a level of classification or taxonomic rank below Kingdom and above Class.
The pneumostome (or breathing pore) is a feature (the respiratory opening) of the external body anatomy of an air-breathing land slug or land snail.
Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea.
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa.
Priapulida (priapulid worms, from Gr. πριάπος, priāpos 'Priapus' + Lat. -ul-, diminutive), sometimes referred to as penis worms, is a phylum of unsegmented marine worms.
Protozoa (also protozoan, plural protozoans) is an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris.
Radiata or Radiates is a historical taxonomic rank that was used to classify animals with radially symmetric body plans, and is no longer accepted.
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants.
The rotifers (Rotifera, commonly called wheel animals) make up a phylum of microscopic and near-microscopic pseudocoelomate animals.
Science, also widely referred to as Science Magazine, is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals.
Sea anemones are a group of marine, predatory animals of the order Actiniaria.
Sea cucumbers are echinoderms from the class Holothuroidea.
Sea snail is a common name for snails that normally live in saltwater, in other words marine gastropods.
Sea urchins or urchins are typically spiny, globular animals, echinoderms in the class Echinoidea.
In biology, sessility (in the sense of positional movement or motility) refers to organisms that do not possess a means of self-locomotion and are normally immobile.
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.
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a group containing 144–320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms.
Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc.
Snail is a common name loosely applied to shelled gastropods.
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.
Spiracles are openings on the surface of some animals, which usually lead to respiratory systems.
Sponges, the members of the phylum Porifera (meaning "pore bearer"), are a basal Metazoa clade as sister of the Diploblasts.
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.
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea.
The starlet sea anemone (Nematostella vectensis) is a species of small sea anemone in the family Edwardsiidae native to the east coast of the United States, with introduced populations along the coast of southeast England and the west coast of the United States.
In zoological nomenclature, a subphylum is a taxonomic rank below the rank of phylum.
Symbion is the name of a genus of aquatic animals, less than 0.5 mm wide, found living attached to the bodies of cold-water lobsters.
Symmetry in biology is the balanced distribution of duplicate body parts or shapes within the body of an organism.
Taenidia (singular: taenidium) are circumferential thickenings of the cuticle inside a trachea or tracheole in an insect's respiratory system.
Tardigrades (also known colloquially as water bears, or moss piglets) are water-dwelling, eight-legged, segmented micro-animals.
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.
In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in a taxonomic hierarchy.
Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.
Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, spiders), as compared with aquatic animals, which live predominantly or entirely in the water (e.g., fish, lobsters, octopuses), or amphibians, which rely on a combination of aquatic and terrestrial habitats (e.g., frogs, or newts).
The thorax or chest (from the Greek θώραξ thorax "breastplate, cuirass, corslet" via thorax) is a part of the anatomy of humans and various other animals located between the neck and the abdomen.
Thrips (order Thysanoptera) are minute (most are 1 mm long or less), slender insects with fringed wings and unique asymmetrical mouthparts.
The Tonian (from Greek τόνος (tónos), meaning "stretch") is the first geologic period of the Neoproterozoic Era.
Tortoises are a family, Testudinidae. Testudinidae is a Family under the order Testudines and suborder Cryptodira.
A trace fossil, also ichnofossil (ιχνος ikhnos "trace, track"), is a geological record of biological activity.
Tracheole (trā'kē-ōl') is a fine respiratory tube of the trachea of an insect or a spider, part of the respiratory system.
Triploblasty is a condition of the blastula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm.
A trochophore (also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia.
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata, which is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords.
Vermes ("worms") is an obsolete taxon used by Carl Linnaeus and Jean-Baptiste Lamarck for non-arthropod invertebrate animals.
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).
The Video Home System (VHS) is a standard for consumer-level analog video recording on tape cassettes.
Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms.
Worms are many different distantly related animals that typically have a long cylindrical tube-like body and no limbs.
Xenoturbella is a genus of very simple bilaterians up to a few centimeters long.
Xiphosurans, sometimes called horseshoe crabs, are arthropods related to arachnids that first appeared in the Hirnantian (Late Ordovician) until today.
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.
Acraniata, Evertebrata, Invertabrate, Invertebrata, Invertebrate fauna, Invertebrate faunas, Invertebrate hormones, Invertebrates, Macroinvertebrate, Macroinvertebrates, Microinvertebrate, Non-vertebrate, Non-vertibrate.