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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. [1]

254 relations: Acanthocephala, Acoela, Acoelomorpha, Aeolosomatidae, Aerobic organism, American robin, Ammonia, Angling, Animal locomotion, Annelid, Anti-inflammatory, Anticoagulant, Anus, Aquaculture, Arthropod, Asexual reproduction, Axon, Bacteria, Badger, Basal (phylogenetics), Bilateria, Biomineralising polychaete, Biomineralization, Blood plasma, Blood vessel, Bloodletting, Brachiopod, Brain, Branchiobdellida, Bristle, British Columbia, Bryozoa, Budding, Burgess Shale, Burgessochaeta, Burrow, Calcium, Cambrian, Canadia (annelid), Canalipalpata, Capillary, Carbon dioxide, Carboniferous, Cell (biology), Central nervous system, Chaeta, Chaetopterus, Charles Darwin, Chemoreceptor, Chitin, ..., Chloragogen cell, Chlorocruorin, Chordate, Cilium, Circulatory system, Cirrus (biology), CITES, Class (biology), Cleavage (embryo), Clitellata, Clitellum, Cloudinidae, Cnidaria, Coelom, Collagen, Compound eye, Connective tissue, Convergent evolution, Coral reef, Cretaceous, Crinoid, Cuticle, Decomposition, Dermis, Deuterostome, Dickinsonia, Dicyemida, Dodecaceria, Earthworm, Ecdysozoa, Echinoderm, Echiura, Ecosystem, Ediacaran, Ediacaran biota, Egg cell, Epidermis, Errantia, Eunicidae, Excretion, External fertilization, Family (biology), Fat, Feces, Filter feeder, Fishing bait, Flagellate, Flatworm, Flowering plant, Follicle (anatomy), Food chain, Fossil, Ganglion, Gastrointestinal tract, Gastrotrich, Genus, Geometer moth, Giant Gippsland earthworm, Gill, Gland, Glycera (annelid), Glycogen, Gonad, Haplodrili, Hemoglobin, Hermaphrodite, Hirudo medicinalis, Hydrogen sulfide, Hydrothermal vent, Inorganic compound, International Union for Conservation of Nature, Intertidal zone, Invertebrate, Jean-Baptiste Lamarck, Jellyfish, Jurassic, Kootenayscolex, Larva, Latin, Leech, Liver, Lophophore, Lophotrochozoa, Machaeridian, Mesentery (zoology), Mesothelium, Metamorphosis, Metastasis, Methane, Microsurgery, Microvillus, Mineral, Mite, Mitochondrion, Molecular phylogenetics, Mollusca, Morphogenesis, Moulting, Mucous membrane, Mucus, Muscle, Myoscolex, Myxobolus cerebralis, Myxosporea, Myzostomida, Nematode, Nemertea, Nemertodermatida, Neontology, Neoplasm, Nephridium, Nereididae, Nervous system, Neuron, Nitrogen, Nuchal organ, Oligochaeta, Onychophora, Ordovician, Organ (anatomy), Organic matter, Ovary, Oxygen, Pack saddle, Palola viridis, Palpata, Paraphyly, Parapodium, Parasitism, Penis, Periproct, Peristalsis, Peristomium, Petroleum seep, Pharynx, Phoronid, Phyllodocidae, Phylum, Plankton, Plant litter, Platyzoa, Polychaete, Priapulida, Proboscis, Prostomium, Protein, Protostome, Pupa, Pygidium, Respiration (physiology), Respiratory pigment, Rotifer, Saliva, Samoa, Scolecida, Sea anemone, Secretion, Sediment, Segmentation (biology), Septum, Sessility (motility), Seta, Sex, Sexual intercourse, Sexual reproduction, Shrew, Siboglinidae, Simon Conway Morris, Simple eye in invertebrates, Sipuncula, Sirius Passet, Small shelly fauna, Soft-bodied organism, Soil, Soil fertility, Species, Sperm, Spermatheca, Statocyst, Stork, Symbiosis, Symmetry in biology, Tardigrade, Taxon, Taxonomy (biology), Teloblast, Tertiary, The Economist, The Formation of Vegetable Mould through the Action of Worms, Trace fossil, Traction (engineering), Tree of life (biology), Trematoda, Triassic, Triploblasty, Trochophore, Undulatory locomotion, Urea, Urine, Vein, Vertebrate, Wiwaxia, Yolk, Zinc. Expand index (204 more) »


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.

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The Acoela or acoels are a class of small and simple invertebrates in the phylum Xenacoelomorpha which resemble flatworms.

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Acoelomorpha is a subphylum of very simple and small soft-bodied animals with planula-like features which live in marine or brackish waters.

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The Aeolosomatidae is a family of very small, acquatic annelid worms, the affinities of which are uncertain.

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Aerobic organism

An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.

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American robin

The American robin (Turdus migratorius) is a migratory songbird of the true thrush genus and Turdidae, the wider thrush family.

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Ammonia is a compound of nitrogen and hydrogen with the formula NH3.

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Angling is a method of fishing by means of an "angle" (fish hook).

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Animal locomotion

Animal locomotion, in ethology, is any of a variety of movements or methods that animals use to move from one place to another.

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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.

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Anti-inflammatory, or antiinflammatory, refers to the property of a substance or treatment that reduces inflammation or swelling.

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Anticoagulants, commonly referred to as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time.

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The anus (from Latin anus meaning "ring", "circle") is an opening at the opposite end of an animal's digestive tract from the mouth.

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Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the farming of fish, crustaceans, molluscs, aquatic plants, algae, and other organisms.

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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.

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Asexual reproduction

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.

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An axon (from Greek ἄξων áxōn, axis) or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses known as action potentials, away from the nerve cell body.

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Bacteria (common noun bacteria, singular bacterium) is a type of biological cell.

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Badgers are short-legged omnivores in the family Mustelidae, which also includes the otters, polecats, weasels, and wolverines.

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Basal (phylogenetics)

In phylogenetics, basal is the direction of the base (or root) of a rooted phylogenetic tree or cladogram.

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The Bilateria or bilaterians, or triploblasts, are animals with bilateral symmetry, i.e., they have a head (anterior) and a tail (posterior) as well as a back (dorsal) and a belly (ventral); therefore they also have a left side and a right side.

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Biomineralising polychaete

Biomineralising polychaetes are polychaetes that biomineralize.

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Biomineralization is the process by which living organisms produce minerals, often to harden or stiffen existing tissues.

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Blood plasma

Blood plasma is a yellowish coloured liquid component of blood that normally holds the blood cells in whole blood in suspension; this makes plasma the extracellular matrix of blood cells.

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Blood vessel

The blood vessels are the part of the circulatory system, and microcirculation, that transports blood throughout the human body.

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Bloodletting (or blood-letting) is the withdrawal of blood from a patient to prevent or cure illness and disease.

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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.

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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.

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Branchiobdellida are an order of leech-like clitellates that are mostly exoparasites of crayfish.

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A bristle is a stiff hair or feather (natural or artificial), either on an animal, such as a pig, or on a tool such as a brush or broom.

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British Columbia

British Columbia (BC; Colombie-Britannique) is the westernmost province of Canada, located between the Pacific Ocean and the Rocky Mountains.

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Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of aquatic invertebrate animals.

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Budding is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site.

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Burgess Shale

The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada.

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Burgessochaeta is an extinct genus of polychaete annelids from the Middle Cambrian.

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A burrow is a hole or tunnel excavated into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion.

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Calcium is a chemical element with symbol Ca and atomic number 20.

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The Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon.

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Canadia (annelid)

Canadia (meaning of Canada or after Canada) is a genus of extinct annelid worm present in Burgess Shale type Konservat-Lagerstätte.

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Canalipalpata, also known as bristle-footed annelids or fan-head worms, is an infraclass of polychaete worms, with 31 families in it including the Sabellida (tubeworms, fanworms, and feather duster worms) and the Alvinellidae, a family of deep-sea worms associated with hydrothermal vents.

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A capillary is a small blood vessel from 5 to 10 micrometres (µm) in diameter, and having a wall one endothelial cell thick.

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Carbon dioxide

Carbon dioxide (chemical formula) is a colorless gas with a density about 60% higher than that of dry air.

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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.

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Cell (biology)

The cell (from Latin cella, meaning "small room") is the basic structural, functional, and biological unit of all known living organisms.

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Central nervous system

The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord.

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A chaeta or cheta (see spelling differences) is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm, although the term is also frequently used to describe similar structures in other invertebrates.

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Chaetopterus or the parchment worm or parchment tube worm is a genus of marine polychaete worm that lives in a tube it constructs in sediments or attaches to a rocky or coral reef substrate.

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Charles Darwin

Charles Robert Darwin, (12 February 1809 – 19 April 1882) was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution.

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A chemoreceptor, also known as chemosensor, is a specialized sensory receptor cell which transduces (responds to) a chemical substance (endogenous or induced) and generates a biological signal.

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Chitin (C8H13O5N)n, a long-chain polymer of ''N''-acetylglucosamine, is a derivative of glucose.

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Chloragogen cell

Chloragogen cells, also called as y cells, are cells in annelids that function similarly to the liver in vertebrates.

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Chlorocruorin is an oxygen-binding hemeprotein present in the blood plasma of many annelids, particularly certain marine polychaetes.

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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.

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A cilium (the plural is cilia) is an organelle found in eukaryotic cells.

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Circulatory system

The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.

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Cirrus (biology)

In biology, a cirrus, plural cirri,, (from the Latin cirrus meaning a curl-like tuft or fringe) is a long, thin structure in an animal similar to a tentacle but generally lacking the tentacle's strength, flexibility, thickness, and sensitivity.

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CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals.

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Class (biology)

In biological classification, class (classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank.

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Cleavage (embryo)

In embryology, cleavage is the division of cells in the early embryo.

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The Clitellata are a class of annelid worms, characterized by having a clitellum - the 'collar' that forms a reproductive cocoon during part of their life cycles.

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The clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches, that secretes a viscid sac in which the eggs are deposited.

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The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud. Cloudinids comprise two genera: Cloudina itself is mineralized, whereas Conotubus is at best weakly mineralized, whilst sharing the same "funnel-in-funnel" construction. Cloudinids had a wide geographic range, reflected in the present distribution of localities in which their fossils are found, and are an abundant component of some deposits. They never appear in the same layers as soft-bodied Ediacaran biota, but the fact that some sequences contain cloudinids and Ediacaran biota in alternating layers suggests that these groups had different environmental preferences. It has been suggested that cloudinids lived embedded in microbial mats, growing new cones to avoid being buried by silt. However no specimens have been found embedded in mats, and their mode of life is still an unresolved question. The classification of the cloudinids has proved difficult: they were initially regarded as polychaete worms, and then as coral-like cnidarians on the basis of what look like buds on some specimens. Current scientific opinion is divided between classifying them as polychaetes and regarding it as unsafe to classify them as members of any broader grouping. Cloudinids are important in the history of animal evolution for two reasons. They are among the earliest and most abundant of the small shelly fossils with mineralized skeletons, and therefore feature in the debate about why such skeletons first appeared in the Late Ediacaran. The most widely supported answer is that their shells are a defense against predators, as some Cloudina specimens from China bear the marks of multiple attacks, which suggests they survived at least a few of them. The holes made by predators are approximately proportional to the size of the Cloudina specimens, and Sinotubulites fossils, which are often found in the same beds, have so far shown no such holes. These two points suggest that predators attacked in a selective manner, and the evolutionary arms race which this indicates is commonly cited as a cause of the Cambrian explosion of animal diversity and complexity.

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Cnidaria is a phylum containing over 10,000 species of animals found exclusively in aquatic (freshwater and marine) environments: they are predominantly marine species.

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The coelom is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs.

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Collagen is the main structural protein in the extracellular space in the various connective tissues in animal bodies.

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Compound eye

A compound eye is a visual organ found in arthropods such as insects and crustaceans.

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Connective tissue

Connective tissue (CT) is one of the four basic types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue.

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Convergent evolution

Convergent evolution is the independent evolution of similar features in species of different lineages.

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Coral reef

Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals.

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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.

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Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata).

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A cuticle, or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection.

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Decomposition is the process by which organic substances are broken down into simpler organic matter.

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The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain.

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Deuterostomes (taxonomic term: Deuterostomia; meaning "second mouth" in Greek) are any members of a superphylum of animals.

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Dickinsonia is a genus of iconic fossils of the Ediacaran biota.

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Dicyemida, also known as Rhombozoa, is a phylum of tiny parasites that live in the renal appendages of cephalopods.

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Dodecaceria is a genus of marine polychaete worms in the family Cirratulidae.

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An earthworm is a tube-shaped, segmented worm found in the phylum Annelida.

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Ecdysozoa is a group of protostome animals, including Arthropoda (insects, chelicerata, crustaceans, and myriapods), Nematoda, and several smaller phyla.

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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.

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The Echiura, or spoon worms, are a small group of marine animals.

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An ecosystem is a community made up of living organisms and nonliving components such as air, water, and mineral soil.

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The Ediacaran Period, spans 94 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 541 Mya.

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Ediacaran biota

The Ediacaran (formerly Vendian) biota consisted of enigmatic tubular and frond-shaped, mostly sessile organisms that lived during the Ediacaran Period (ca. 635–542 Mya).

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Egg cell

The egg cell, or ovum (plural ova), is the female reproductive cell (gamete) in oogamous organisms.

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The epidermis is the outer layer of the three layers that make up the skin, the inner layers being the dermis and hypodermis.

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Errantia, occasionally Aciculata, is a subclass of polychaete worms.

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Eunicidae is a family of polychaetes.

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Excretion is the process by which metabolic waste is eliminated from an organism.

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External fertilization

External fertilization is a male organism’s sperm fertilizing a female organism’s egg outside of the female’s body.

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Family (biology)

In biological classification, family (familia, plural familiae) is one of the eight major taxonomic ranks; it is classified between order and genus.

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Fat is one of the three main macronutrients, along with carbohydrate and protein.

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Feces (or faeces) are the solid or semisolid remains of the food that could not be digested in the small intestine.

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Filter feeder

Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure.

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Fishing bait

Fishing bait is any substance used to attract and catch fish, e.g. on the end of a fishing hook, or inside a fish trap.

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A flagellate is a cell or organism with one or more whip-like appendages called flagella.

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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.

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Flowering plant

The flowering plants, also known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 416 families, approximately 13,164 known genera and c. 295,383 known species.

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Follicle (anatomy)

A follicle is a small spherical or vase-like group of cells enclosing a cavity in which some other structure grows or other material is contained.

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Food chain

A food chain is a linear network of links in a food web starting from producer organisms (such as grass or trees which use radiation from the Sun to make their food) and ending at apex predator species (like grizzly bears or killer whales), detritivores (like earthworms or woodlice), or decomposer species (such as fungi or bacteria).

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A fossil (from Classical Latin fossilis; literally, "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age.

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A ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system and sensory system.

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Gastrointestinal tract

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.

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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.

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A genus (genera) is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology.

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Geometer moth

The geometer moths are moths belonging to the family Geometridae of the insect order Lepidoptera, the moths and butterflies.

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Giant Gippsland earthworm

The giant Gippsland earthworm, Megascolides australis, is one of Australia's 1,000 native earthworm species.

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A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide.

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A gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).

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Glycera (annelid)

The genus Glycera is a group of polychaetes (bristle worms) commonly known as bloodworms.

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Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in humans, animals, fungi, and bacteria.

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A gonad or sex gland or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism.

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Haplodrili, or Archiannelida, is an order of primitive polychaete worms.

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Hemoglobin (American) or haemoglobin (British); abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates (with the exception of the fish family Channichthyidae) as well as the tissues of some invertebrates.

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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.

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Hirudo medicinalis

Hirudo medicinalis, the European medicinal leech, is one of several species of leeches used as "medicinal leeches".

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Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula H2S.

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Hydrothermal vent

A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues.

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Inorganic compound

An inorganic compound is typically a chemical compound that lacks C-H bonds, that is, a compound that is not an organic compound, but the distinction is not defined or even of particular interest.

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International Union for Conservation of Nature

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.

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Intertidal zone

The intertidal zone, also known as the foreshore and seashore and sometimes referred to as the littoral zone, is the area that is above water at low tide and under water at high tide (in other words, the area between tide marks).

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Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord.

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Jean-Baptiste Lamarck

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck, was a French naturalist.

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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.

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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.

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Kootenayscolex, the bristle-headed worm, is a 500 million year old fossil species of proto-annelid resembling a bristle worm, found in British Columbia in 2012.

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A larva (plural: larvae) is a distinct juvenile form many animals undergo before metamorphosis into adults.

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Latin (Latin: lingua latīna) is a classical language belonging to the Italic branch of the Indo-European languages.

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Leeches are segmented parasitic or predatory worm-like animals that belong to the phylum Annelida and comprise the subclass Hirudinea.

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The liver, an organ only found in vertebrates, detoxifies various metabolites, synthesizes proteins, and produces biochemicals necessary for digestion.

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The lophophore is a characteristic feeding organ possessed by four major groups of animals: the Brachiopoda, Bryozoa, Hyolitha, and Phoronida, which collectively constitute the protostome group Lophophorata.

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Lophotrochozoa ("crest/wheel animals") is a clade of protostome animals within the Spiralia.

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Machaeridia is an extinct group of armoured, segmented annelid worms, known from the Early Ordovician (Late Tremadoc) to Carboniferous.

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Mesentery (zoology)

A mesentery is a membrane inside the body cavity of an animal.

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The mesothelium is a membrane composed of simple squamous epithelium that forms the lining of several body cavities: the pleura (thoracic cavity), peritoneum (abdominal cavity including the mesentery), mediastinum and pericardium (heart sac).

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Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.

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Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; it is typically spoken of as such spread by a cancerous tumor.

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Methane is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen).

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Microsurgery is a general term for surgery requiring an operating microscope.

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Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.

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A mineral is a naturally occurring chemical compound, usually of crystalline form and not produced by life processes.

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Mites are small arthropods belonging to the class Arachnida and the subclass Acari (also known as Acarina).

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The mitochondrion (plural mitochondria) is a double-membrane-bound organelle found in most eukaryotic organisms.

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Molecular phylogenetics

Molecular phylogenetics is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominately in DNA sequences, to gain information on an organism's evolutionary relationships.

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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.

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Morphogenesis (from the Greek morphê shape and genesis creation, literally, "beginning of the shape") is the biological process that causes an organism to develop its shape.

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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.

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Mucous membrane

A mucous membrane or mucosa is a membrane that lines various cavities in the body and covers the surface of internal organs.

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Mucus is a slippery aqueous secretion produced by, and covering, mucous membranes.

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Muscle is a soft tissue found in most animals.

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Myoscolex is an early animal species known from the Cambrian Emu Bay Shale in South Australia.

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Myxobolus cerebralis

Myxobolus cerebralis is a myxosporean parasite of salmonids (salmon, trout, and their allies) that causes whirling disease in farmed salmon and trout and also in wild fish populations.

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Myxosporea is a subclass of microscopic parasites, belonging to the Myxozoa clade within Cnidaria.

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The Myzostomida are an order of small marine polychaete worms, which are parasitic on crinoids.

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The nematodes or roundworms constitute the phylum Nematoda (also called Nemathelminthes).

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Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms".

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Nemertodermatida is a class of Acoela, comprising about ten species of millimetre-sized 'tubellariform', mostly interstitial worms.

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Neontology is a part of biology that, in contrast to paleontology, deals with living (or, more generally, recent) organisms.

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Neoplasia is a type of abnormal and excessive growth of tissue.

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The nephridium (plural nephridia) is an invertebrate organ which occurs in pairs and performs a function similar to the vertebrate kidney.

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Nereididae (formerly spelled Nereidae) are a family of polychaete worms.

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Nervous system

The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body.

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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.

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Nitrogen is a chemical element with symbol N and atomic number 7.

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Nuchal organ

The nuchal organ is a ciliated pit or groove present at the posterior end of the prostomium of annelid worms, some cephalopods, and other invertebrates.

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Oligochaeta is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms.

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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.

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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era.

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Organ (anatomy)

Organs are collections of tissues with similar functions.

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Organic matter

Organic matter, organic material, or natural organic matter (NOM) refers to the large pool of carbon-based compounds found within natural and engineered, terrestrial and aquatic environments.

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The ovary is an organ found in the female reproductive system that produces an ovum.

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Oxygen is a chemical element with symbol O and atomic number 8.

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Pack saddle

A pack saddle is any device designed to be secured on the back of a horse, mule, or other working animal so it can carry heavy loads such as luggage, firewood, small cannons or other weapons too heavy to be carried by humans.

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Palola viridis

Palola viridis, commonly known as the palolo worm or Samoan palolo worm, is a Polychaeta species from the waters of the Pacific islands around Samoa and the Maluku Islands.

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Palpata is a subclass of polychaete worm.

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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.

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The term parapodium (Gr. para, beyond or beside + podia, feet) refers to two different organs.

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In evolutionary biology, parasitism is a relationship between species, where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life.

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A penis (plural penises or penes) is the primary sexual organ that male animals use to inseminate sexually receptive mates (usually females and hermaphrodites) during copulation.

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The periproct is the final body segment in annelid worms.

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Peristalsis is a radially symmetrical contraction and relaxation of muscles that propagates in a wave down a tube, in an anterograde direction.

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The peristomium is the first true body segment in an annelid worm's body in the anterior end.

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Petroleum seep

A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow.

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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.

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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.

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Phyllodocidae is a family of polychaete worms.

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In biology, a phylum (plural: phyla) is a level of classification or taxonomic rank below Kingdom and above Class.

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Plankton (singular plankter) are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current.

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Plant litter

Litterfall, plant litter, leaf litter, tree litter, soil litter, or duff, is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground.

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The paraphyletic "Platyzoa" are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998.

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The Polychaeta, also known as the bristle worms or polychaetes, are a paraphyletic class of annelid worms, generally marine.

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Priapulida (priapulid worms, from Gr. πριάπος, priāpos 'Priapus' + Lat. -ul-, diminutive), sometimes referred to as penis worms, is a phylum of unsegmented marine worms.

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A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate.

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The prostomium (sometimes also called the acron) is the first body segment in an annelid worm's body in the anterior end.

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Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.

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Protostomia (from Greek πρωτο- proto- "first" and στόμα stoma "mouth") is a clade of animals.

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A pupa (pūpa, "doll"; plural: pūpae) is the life stage of some insects undergoing transformation between immature and mature stages.

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The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites.

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Respiration (physiology)

In physiology, respiration is defined as the movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction.

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Respiratory pigment

A respiratory pigment is a molecule, such as hemoglobin in humans and other vertebrates, that increases the oxygen-carrying capacity of the blood.

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The rotifers (Rotifera, commonly called wheel animals) make up a phylum of microscopic and near-microscopic pseudocoelomate animals.

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Saliva is a watery substance formed in the mouths of animals, secreted by the salivary glands.

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Samoa, officially the Independent State of Samoa (Malo Saʻoloto Tutoʻatasi o Sāmoa; Sāmoa) and, until 4 July 1997, known as Western Samoa, is a unitary parliamentary democracy with eleven administrative divisions.

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Scolecida is an infraclass of polychaete worms.

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Sea anemone

Sea anemones are a group of marine, predatory animals of the order Actiniaria.

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Secretion is the movement of material from one point to another, e.g. secreted chemical substance from a cell or gland.

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Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice, and/or by the force of gravity acting on the particles.

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Segmentation (biology)

Segmentation in biology is the division of some animal and plant body plans into a series of repetitive segments.

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In biology, a septum (Latin for something that encloses; plural septa) is a wall, dividing a cavity or structure into smaller ones.

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Sessility (motility)

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.

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In biology, setae (singular seta; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms.

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Organisms of many species are specialized into male and female varieties, each known as a sex. Sexual reproduction involves the combining and mixing of genetic traits: specialized cells known as gametes combine to form offspring that inherit traits from each parent.

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Sexual intercourse

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.

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Sexual reproduction

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.

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A shrew (family Soricidae) is a small mole-like mammal classified in the order Eulipotyphla.

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Siboglinidae, also known as the beard worms, is a family of polychaete annelid worms whose members made up the former phyla Pogonophora (the giant tube worms) and Vestimentifera.

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Simon Conway Morris

Simon Conway Morris (born 1951) is an English palaeontologist, evolutionary biologist, and astrobiologist known for his study of the fossils of the Burgess Shale and the Cambrian explosion.

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Simple eye in invertebrates

A simple eye (sometimes called a pigment pit) refers to a type of eye form or optical arrangement that contains a single lens.

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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.

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Sirius Passet

Sirius Passet is a Cambrian Lagerstätte in Greenland.

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Small shelly fauna

The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian Period.

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Soft-bodied organism

Soft-bodied organisms are animals that lack skeletons, a group roughly corresponding to the group Vermes as proposed by Carl von Linné.

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Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life.

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Soil fertility

Soil fertility refers to the ability of a soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality.

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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.

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Sperm is the male reproductive cell and is derived from the Greek word (σπέρμα) sperma (meaning "seed").

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The spermatheca (pronounced plural: spermathecae), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. bees, some molluscs, oligochaeta worms and certain other invertebrates and vertebrates.

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The statocyst is a balance sensory receptor present in some aquatic invertebrates, including molluscs, bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans.

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Storks are large, long-legged, long-necked wading birds with long, stout bills.

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Symbiosis (from Greek συμβίωσις "living together", from σύν "together" and βίωσις "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic.

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Symmetry in biology

Symmetry in biology is the balanced distribution of duplicate body parts or shapes within the body of an organism.

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Tardigrades (also known colloquially as water bears, or moss piglets) are water-dwelling, eight-legged, segmented micro-animals.

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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.

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Taxonomy (biology)

Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.

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A teloblast is a large cell in the embryos of clitellate annelids which asymmetrically divide to form many smaller cells known as blast cells.

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Tertiary is the former term for the geologic period from 65 million to 2.58 million years ago, a timespan that occurs between the superseded Secondary period and the Quaternary.

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The Economist

The Economist is an English-language weekly magazine-format newspaper owned by the Economist Group and edited at offices in London.

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The Formation of Vegetable Mould through the Action of Worms

The Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits (sometimes shortened to Worms) is an 1881 book by Charles Darwin on earthworms.

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Trace fossil

A trace fossil, also ichnofossil (ιχνος ikhnos "trace, track"), is a geological record of biological activity.

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Traction (engineering)

Traction, or tractive force, is the force used to generate motion between a body and a tangential surface, through the use of dry friction, though the use of shear force of the surface is also commonly used.

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Tree of life (biology)

The tree of life or universal tree of life is a metaphor, model and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct, as described in a famous passage in Charles Darwin's On the Origin of Species (1859).

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Trematoda is a class within the phylum Platyhelminthes.

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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.

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Triploblasty is a condition of the blastula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm.

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A trochophore (also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia.

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Undulatory locomotion

Undulatory locomotion is the type of motion characterized by wave-like movement patterns that act to propel an animal forward.

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Urea, also known as carbamide, is an organic compound with chemical formula CO(NH2)2.

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Urine is a liquid by-product of metabolism in humans and in many animals.

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Veins are blood vessels that carry blood toward the heart.

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Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones).

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Wiwaxia is a genus of soft-bodied animals that were covered in carbonaceous scales and spines.

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Among animals which produce one, the yolk (also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo.

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Zinc is a chemical element with symbol Zn and atomic number 30.

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Annelid worm, Annelid worms, Annelida, Annelida Phylum, Annelids, Chaetopoda, Phylum Annelida, Phylum annelida, Ringed worm, Segmented worm.


[1] https://en.wikipedia.org/wiki/Annelid

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