Editing Anatomy (section)

== Invertebrate anatomy ==
[[File:Chirocephalus diaphanus male head.png|thumb|Head of a male ''[[Daphnia]]'', a [[planktonic]] crustacean]]
[[Invertebrate]]s constitute a vast array of living organisms ranging from the simplest unicellular [[eukaryote]]s such as ''[[Paramecium]]'' to such complex multicellular animals as the [[octopus]], [[lobster]] and [[dragonfly]]. They constitute about 95% of the animal species. By definition, none of these creatures has a backbone. The cells of single-cell [[protozoa]]ns have the same basic structure as those of multicellular animals but some parts are specialized into the equivalent of tissues and organs. Locomotion is often provided by [[cilia]] or [[flagella]] or may proceed via the advance of [[pseudopodia]], food may be gathered by [[phagocytosis]], energy needs may be supplied by [[photosynthesis]] and the cell may be supported by an [[endoskeleton]] or an [[exoskeleton]]. Some protozoans can form multicellular colonies.<ref>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=23–24 }}</ref>

[[Metazoa]]ns are a multicellular organism, with different groups of cells serving different functions. The most basic types of metazoan tissues are epithelium and connective tissue, both of which are present in nearly all invertebrates. The outer surface of the epidermis is normally formed of epithelial cells and secretes an [[extracellular matrix]] which provides support to the organism. An endoskeleton derived from the [[mesoderm]] is present in [[echinoderm]]s, [[sponge]]s and some [[cephalopod]]s. [[Exoskeleton]]s are derived from the epidermis and is composed of [[chitin]] in [[arthropod]]s (insects, spiders, ticks, shrimps, crabs, lobsters). [[Calcium carbonate]] constitutes the shells of [[molluscs]], [[brachiopod]]s and some tube-building [[polychaete worms]] and [[silica]] forms the exoskeleton of the microscopic [[diatom]]s and [[radiolaria]].<ref>{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/198292/exoskeleton |title=Exoskeleton |encyclopedia=Encyclopædia Britannica |access-date=2 July 2013 |archive-date=3 May 2015 |archive-url=https://web.archive.org/web/20150503190050/https://www.britannica.com/EBchecked/topic/198292/exoskeleton |url-status=live }}</ref> Other invertebrates may have no rigid structures but the epidermis may secrete a variety of surface coatings such as the [[pinacoderm]] of sponges, the gelatinous cuticle of cnidarians ([[polyp (zoology)|polyp]]s, [[sea anemone]]s, [[jellyfish]]) and the [[collagen]]ous cuticle of [[annelid]]s. The outer epithelial layer may include cells of several types including sensory cells, gland cells and stinging cells. There may also be protrusions such as [[microvilli]], cilia, bristles, [[Spine (zoology)|spines]] and [[tubercle]]s.<ref>{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/289723/integument |title=Integument |author=Ebling, F. J. G. |encyclopedia=Encyclopædia Britannica |access-date=2 July 2013 |archive-date=30 April 2015 |archive-url=https://web.archive.org/web/20150430013330/https://www.britannica.com/EBchecked/topic/289723/integument |url-status=live }}</ref>

[[Marcello Malpighi]], the father of microscopical anatomy, discovered that plants had tubules similar to those he saw in insects like the silk worm. He observed that when a ring-like portion of bark was removed on a trunk a swelling occurred in the tissues above the ring, and he unmistakably interpreted this as growth stimulated by food coming down from the leaves, and being captured above the ring.<ref name="ArberAgnes">{{cite journal|author=Arber, Agnes|title= Nehemiah Grew (1641–1712) and Marcello Malpighi (1628–1694): an essay in comparison|journal= Isis |volume =34|issue=1| pages =7–16|jstor=225992|doi=10.1086/347742|year= 1942|s2cid= 143008947}}</ref>

=== Arthropod anatomy ===
{{main|Arthropod|Insect morphology|Spider anatomy}}
[[Arthropod]]s comprise the largest phylum of [[invertebrate]]s in the animal kingdom with over a million known species.<ref>Britannica Concise Encyclopaedia 2007</ref>

[[Insect]]s possess [[segmentation (biology)|segmented]] bodies supported by a hard-jointed outer covering, the [[exoskeleton]], made mostly of [[chitin]]. The segments of the body are organized into three distinct parts, a head, a [[Thorax (insect anatomy)|thorax]] and an [[abdomen]].<ref>{{cite web|title=O. Orkin Insect zoo |url=https://insectzoo.msstate.edu/Students/basic.structure.html |year=1997 |publisher=Mississippi State University |access-date=23 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20090602045832/https://www.insectzoo.msstate.edu/Students/basic.structure.html |archive-date=2 June 2009 }}</ref> The head typically bears a pair of sensory [[Antenna (biology)|antennae]], a pair of [[compound eye]]s, one to three simple eyes ([[ocelli]]) and three sets of modified appendages that form the [[insect mouthparts|mouthparts]]. The thorax has three pairs of segmented [[arthropod leg|legs]], one pair each for the three segments that compose the thorax and one or two pairs of [[insect wing|wings]]. The abdomen is composed of eleven segments, some of which may be fused and houses the [[digestion|digestive]], [[Respiration (physiology)|respiratory]], [[excretory]] and reproductive systems.<ref name="Gullan and Cranston">{{cite book |last1=Gullan |first1=P.J. |last2=Cranston |first2=P. S. |title=The Insects: An Outline of Entomology |publisher=Blackwell Publishing |location=Oxford |year=2005 |edition=3 |pages=[https://archive.org/details/isbn_9781405111133/page/22 22–48] |isbn=978-1-4051-1113-3 |url-access=registration |url=https://archive.org/details/isbn_9781405111133/page/22 }}</ref> There is considerable variation between species and many adaptations to the body parts, especially wings, legs, antennae and mouthparts.<ref>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=218–225 }}</ref>

[[Spider]]s a class of [[arachnid]]s have four pairs of legs; a body of two segments—a [[cephalothorax]] and an [[abdomen]]. Spiders have no wings and no antennae. They have mouthparts called [[chelicerae]] which are often connected to venom glands as most spiders are venomous. They have a second pair of appendages called [[pedipalp]]s attached to the cephalothorax. These have similar segmentation to the legs and function as taste and smell organs. At the end of each male pedipalp is a spoon-shaped cymbium that acts to support the [[palpal bulb|copulatory organ]].