Misplaced Pages

#562437

63-661: GRIN has extended its role to manage information on the germplasm reposits of insect ( invertebrate ), microbial , and animal species (see sub-projects ). The site is a resource for identifying taxonomic information (scientific names) as well as common names on more than 500,000 accessions (distinct varieties , cultivars etc.) of plants covering 10,000 species; both economically important ones and wild species. It profiles plants that are invasive or noxious weeds, threatened or endangered, giving out data on worldwide distribution of its habitat; as well as passport information. GRIN also incorporates an Economic Plants Database. The network

126-446: A t e s {\displaystyle n.states} , c i occupies a range from 1 to ( n . s t a t e s − 1 ) / ( n . t a x a − ⌈ n . t a x a / n . s t a t e s ⌉ ) {\displaystyle (n.states-1)/(n.taxa-\lceil n.taxa/n.states\rceil )} . The retention index (RI)

189-445: A metric to measure how consistent a candidate cladogram is with the data. Most cladogram algorithms use the mathematical techniques of optimization and minimization. In general, cladogram generation algorithms must be implemented as computer programs, although some algorithms can be performed manually when the data sets are modest (for example, just a few species and a couple of characteristics). Some algorithms are useful only when

252-540: A character in a phylogenetic analysis as they do not contribute anything to our understanding of relationships. However, homoplasy is often not evident from inspection of the character itself (as in DNA sequence, for example), and is then detected by its incongruence (unparsimonious distribution) on a most-parsimonious cladogram. Note that characters that are homoplastic may still contain phylogenetic signal . A well-known example of homoplasy due to convergent evolution would be

315-412: A cladogram can be roughly categorized as either morphological (synapsid skull, warm blooded, notochord , unicellular, etc.) or molecular (DNA, RNA, or other genetic information). Prior to the advent of DNA sequencing, cladistic analysis primarily used morphological data. Behavioral data (for animals) may also be used. As DNA sequencing has become cheaper and easier, molecular systematics has become

378-422: A dataset, the degree to which each character carries phylogenetic information, and the fashion in which additive characters are coded, rendering it unfit for purpose. c i occupies a range from 1 to 1/[ n.taxa /2] in binary characters with an even state distribution; its minimum value is larger when states are not evenly spread. In general, for a binary or non-binary character with n . s t

441-432: A group of organisms with a last common ancestor . There are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor (not an actual entity) which can be inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about

504-457: A larger clade. The incongruence length difference test (ILD) is a measurement of how the combination of different datasets (e.g. morphological and molecular, plastid and nuclear genes) contributes to a longer tree. It is measured by first calculating the total tree length of each partition and summing them. Then replicates are made by making randomly assembled partitions consisting of the original partitions. The lengths are summed. A p value of 0.01

567-452: A more and more popular way to infer phylogenetic hypotheses. Using a parsimony criterion is only one of several methods to infer a phylogeny from molecular data. Approaches such as maximum likelihood , which incorporate explicit models of sequence evolution, are non-Hennigian ways to evaluate sequence data. Another powerful method of reconstructing phylogenies is the use of genomic retrotransposon markers , which are thought to be less prone to

630-528: A small proportion of the Metazoa that to speak of the kingdom Animalia in terms of "Vertebrata" and "Invertebrata" has limited practicality. In the more formal taxonomy of Animalia other attributes that logically should precede the presence or absence of the vertebral column in constructing a cladogram , for example, the presence of a notochord . That would at least circumscribe the Chordata. However, even

693-494: A source of information for forensic investigators. Two of the most commonly studied model organisms nowadays are invertebrates: the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans . They have long been the most intensively studied model organisms , and were among the first life-forms to be genetically sequenced. This was facilitated by the severely reduced state of their genomes , but many genes , introns , and linkages have been lost. Analysis of

SECTION 10

#1732775697563

756-431: A wide range of invertebrate species, including annelids, molluscs, nematodes and arthropods. One type of invertebrate respiratory system is the open respiratory system composed of spiracles , tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues. The distribution of spiracles can vary greatly among the many orders of insects, but in general each segment of

819-410: Is a character state that is shared by two or more taxa due to some cause other than common ancestry. The two main types of homoplasy are convergence (evolution of the "same" character in at least two distinct lineages) and reversion (the return to an ancestral character state). Characters that are obviously homoplastic, such as white fur in different lineages of Arctic mammals, should not be included as

882-402: Is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be consistent with the same cladogram. A cladogram uses lines that branch off in different directions ending at a clade ,

945-552: Is also included within invertebrates: the Arthropoda, including insects, spiders , crabs , and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. In addition, they possess a hardened exoskeleton that is periodically shed during growth. Two smaller phyla, the Onychophora and Tardigrada , are close relatives of the arthropods and share some traits with them, excluding

1008-500: Is easily seen in snails and sea snails , which have helical shells. Slugs appear externally symmetrical, but their pneumostome (breathing hole) is located on the right side. Other gastropods develop external asymmetry, such as Glaucus atlanticus that develops asymmetrical cerata as they mature. The origin of gastropod asymmetry is a subject of scientific debate. Other examples of asymmetry are found in fiddler crabs and hermit crabs . They often have one claw much larger than

1071-592: Is maintained by GRIN's Database Management Unit (GRIN/DBMU). GRIN is under the oversight of National Germplasm Resources Laboratory (NGRL) in Beltsville, Maryland , which in 1990 replaced its forerunner, the Germplasm Services Laboratory (GSL), that had formerly run GRIN. Since November, 2015 GRIN has been running on GRIN-Global software produced by a collaborative project between the USDA and

1134-474: Is not always precise among non-biologists since it does not accurately describe a taxon in the same way that Arthropoda , Vertebrata or Manidae do. Each of these terms describes a valid taxon, phylum , subphylum or family . "Invertebrata" is a term of convenience, not a taxon; it has very little circumscriptional significance except within the Chordata . The Vertebrata as a subphylum comprises such

1197-411: Is obtained for 100 replicates if 99 replicates have longer combined tree lengths. Some measures attempt to measure the amount of homoplasy in a dataset with reference to a tree, though it is not necessarily clear precisely what property these measures aim to quantify The consistency index (CI) measures the consistency of a tree to a set of data – a measure of the minimum amount of homoplasy implied by

1260-636: Is particularly salient in eusocial species but applies to other invertebrates as well. Insects recognize information transmitted by other insects. The term invertebrates covers several phyla. One of these are the sponges ( Porifera ). They were long thought to have diverged from other animals early. They lack the complex organization found in most other phyla. Their cells are differentiated, but in most cases not organized into distinct tissues. Sponges typically feed by drawing in water through pores. Some speculate that sponges are not so primitive, but may instead be secondarily simplified. The Ctenophora and

1323-526: Is usually done by comparison to the character states of one or more outgroups . States shared between the outgroup and some members of the in-group are symplesiomorphies; states that are present only in a subset of the in-group are synapomorphies. Note that character states unique to a single terminal (autapomorphies) do not provide evidence of grouping. The choice of an outgroup is a crucial step in cladistic analysis because different outgroups can produce trees with profoundly different topologies. A homoplasy

SECTION 20

#1732775697563

1386-737: The Acanthocephala , or spiny-headed worms, the Gnathostomulida , Micrognathozoa , and the Cycliophora . Also included are two of the most successful animal phyla, the Mollusca and Annelida. The former, which is the second-largest animal phylum by number of described species, includes animals such as snails , clams , and squids , and the latter comprises the segmented worms, such as earthworms and leeches . These two groups have long been considered close relatives because of

1449-737: The Cnidaria , which includes sea anemones , corals , and jellyfish , are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus. Both have distinct tissues, but they are not organized into organs . There are only two main germ layers, the ectoderm and endoderm , with only scattered cells between them. As such, they are sometimes called diploblastic . The Echinodermata are radially symmetric and exclusively marine, including starfish (Asteroidea), sea urchins , (Echinoidea), brittle stars (Ophiuroidea), sea cucumbers (Holothuroidea) and feather stars (Crinoidea). The largest animal phylum

1512-734: The Global Crop Diversity Trust . A stated mission of GRIN is to support the following projects: Invertebrate Invertebrates is an umbrella term describing animals that neither develop nor retain a vertebral column (commonly known as a spine or backbone ), which evolved from the notochord . It is a paraphyletic grouping including all animals excluding the chordate subphylum Vertebrata , i.e. vertebrates . Well-known phyla of invertebrates include arthropods , mollusks , annelids , echinoderms , flatworms , cnidarians , and sponges . The majority of animal species are invertebrates; one estimate puts

1575-536: The Nemertea , or ribbon worms, and the Sipuncula . Another phylum is Platyhelminthes , the flatworms. These were originally considered primitive, but it now appears they developed from more complex ancestors. Flatworms are acoelomates , lacking a body cavity, as are their closest relatives, the microscopic Gastrotricha . The Rotifera , or rotifers, are common in aqueous environments. Invertebrates also include

1638-595: The Phanerozoic . Fossils of invertebrates are commonly used in stratigraphy. Carl Linnaeus divided these animals into only two groups, the Insecta and the now-obsolete Vermes ( worms ). Jean-Baptiste Lamarck , who was appointed to the position of "Curator of Insecta and Vermes" at the Muséum National d'Histoire Naturelle in 1793, both coined the term "invertebrate" to describe such animals and divided

1701-666: The Protozoa , Porifera , Coelenterata , Platyhelminthes , Nematoda , Annelida , Echinodermata , Mollusca and Arthropoda . Arthropoda include insects , crustaceans and arachnids . By far the largest number of described invertebrate species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species , 2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, which means that over 95% of

1764-457: The Tonian . Trace fossils such as tracks and burrows found in the late Neoproterozoic Era indicate the presence of triploblastic worms, roughly as large (about 5 mm wide) and complex as earthworms . Around 453 MYA, animals began diversifying, and many of the important groups of invertebrates diverged from one another. Fossils of invertebrates are found in various types of sediment from

1827-545: The gill chamber of their fish hosts ). Neurons differ in invertebrates from mammalian cells. Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal leech , Hirudo medicinalis . Learning and memory using nociceptors in the sea hare, Aplysia has been described. Mollusk neurons are able to detect increasing pressures and tissue trauma. Neurons have been identified in

1890-449: The starlet sea anemone genome has emphasised the importance of sponges, placozoans, and choanoflagellates , also being sequenced, in explaining the arrival of 1,500 ancestral genes unique to animals. Invertebrates are also used by scientists in the field of aquatic biomonitoring to evaluate the effects of water pollution and climate change . Cladogram A cladogram (from Greek clados "branch" and gramma "character")

1953-718: The 1968 edition of Invertebrate Zoology , it is noted that "division of the Animal Kingdom into vertebrates and invertebrates is artificial and reflects human bias in favor of man's own relatives." The book also points out that the group lumps a vast number of species together, so that no one characteristic describes all invertebrates. In addition, some species included are only remotely related to one another, with some more related to vertebrates than other invertebrates (see Paraphyly ). For many centuries, invertebrates were neglected by biologists, in favor of big vertebrates and "useful" or charismatic species . Invertebrate biology

Germplasm Resources Information Network - Misplaced Pages Continue

2016-538: The air sacs in their abdomen, are able to control the flow of air through their body. In some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a gill , or function essentially as normal, via a plastron . Despite being internal, the tracheae of arthropods are shed during moulting ( ecdysis ). Only vertebrate animals have ears, though many invertebrates detect sound using other kinds of sense organs. In insects, tympanal organs are used to hear distant sounds. They are located either on

2079-460: The body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular exoskeleton that branch ( anastomose ) throughout the body with diameters from only a few micrometres up to 0.8 mm. The smallest tubes, tracheoles, penetrate cells and serve as sites of diffusion for water , oxygen , and carbon dioxide . Gas may be conducted through

2142-941: The call of her host, a male cricket. Depending on where the song of the cricket is coming from, the fly's hearing organs will reverberate at slightly different frequencies. This difference may be as little as 50 billionths of a second, but it is enough to allow the fly to home in directly on a singing male cricket and parasitise it. Like vertebrates, most invertebrates reproduce at least partly through sexual reproduction . They produce specialized reproductive cells that undergo meiosis to produce smaller, motile spermatozoa or larger, non-motile ova . These fuse to form zygotes , which develop into new individuals. Others are capable of asexual reproduction, or sometimes, both methods of reproduction. Extensive research with model invertebrate species such as Drosophila melanogaster and Caenorhabditis elegans has contributed much to our understanding of meiosis and reproduction. However, beyond

2205-431: The character, "presence of wings". Although the wings of birds, bats , and insects serve the same function, each evolved independently, as can be seen by their anatomy . If a bird, bat, and a winged insect were scored for the character, "presence of wings", a homoplasy would be introduced into the dataset, and this could potentially confound the analysis, possibly resulting in a false hypothesis of relationships. Of course,

2268-434: The characteristic data are molecular (DNA, RNA); other algorithms are useful only when the characteristic data are morphological. Other algorithms can be used when the characteristic data includes both molecular and morphological data. Algorithms for cladograms or other types of phylogenetic trees include least squares , neighbor-joining , parsimony , maximum likelihood , and Bayesian inference . Biologists sometimes use

2331-826: The common presence of trochophore larvae, but the annelids were considered closer to the arthropods because they are both segmented. Now, this is generally considered convergent evolution , owing to many morphological and genetic differences between the two phyla. Among lesser phyla of invertebrates are the Hemichordata , or acorn worms, and the Chaetognatha, or arrow worms. Other phyla include Acoelomorpha , Brachiopoda , Bryozoa , Entoprocta , Phoronida , and Xenoturbellida . Invertebrates can be classified into several main categories, some of which are taxonomically obsolescent or debatable, but still used as terms of convenience. Each however appears in its own article at

2394-561: The conclusion that in vertebrates are a group that deviates from the normal, vertebrates. This has been said to be because researchers in the past, such as Lamarck, viewed vertebrates as a "standard": in Lamarck's theory of evolution, he believed that characteristics acquired through the evolutionary process involved not only survival, but also progression toward a "higher form", to which humans and vertebrates were closer than invertebrates were. Although goal-directed evolution has been abandoned,

2457-691: The dataset). The rescaled consistency index (RC) is obtained by multiplying the CI by the RI; in effect this stretches the range of the CI such that its minimum theoretically attainable value is rescaled to 0, with its maximum remaining at 1. The homoplasy index (HI) is simply 1 − CI. This measures the amount of homoplasy observed on a tree relative to the maximum amount of homoplasy that could theoretically be present – 1 − (observed homoplasy excess) / (maximum homoplasy excess). A value of 1 indicates no homoplasy; 0 represents as much homoplasy as there would be in

2520-566: The described animal species in the world are invertebrates. The trait that is common to all invertebrates is the absence of a vertebral column (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically homologous trait, any more than the common trait of having wings functionally unites insects, bats, and birds, or than not having wings unites tortoises , snails and sponges . Being animals, invertebrates are heterotrophs, and require sustenance in

2583-466: The distinction of invertebrates and vertebrates persists to this day, even though the grouping has been noted to be "hardly natural or even very sharp." Another reason cited for this continued distinction is that Lamarck created a precedent through his classifications which is now difficult to escape from. It is also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates. In any event, in

Germplasm Resources Information Network - Misplaced Pages Continue

2646-457: The few model systems, the modes of reproduction found in invertebrates show incredible diversity. In one extreme example, it is estimated that 10% of orbatid mite species have persisted without sexual reproduction and have reproduced asexually for more than 400 million years. Social behavior is widespread in invertebrates, including cockroaches, termites, aphids, thrips , ants, bees, Passalidae , Acari , spiders, and more. Social interaction

2709-534: The figure at 97%. Many invertebrate taxa have a greater number and diversity of species than the entire subphylum of Vertebrata. Invertebrates vary widely in size, from 10  μm (0.0004 in) myxozoans to the 9–10 m (30–33 ft) colossal squid . Some so-called invertebrates, such as the Tunicata and Cephalochordata , are actually sister chordate subphyla to Vertebrata, being more closely related to vertebrates than to other invertebrates. This makes

2772-470: The following links. The earliest animal fossils appear to be those of invertebrates. 665-million-year-old fossils in the Trezona Formation at Trezona Bore, West Central Flinders, South Australia have been interpreted as being early sponges. Some paleontologists suggest that animals appeared much earlier, possibly as early as 1 billion years ago though they probably became multicellular in

2835-555: The form of the consumption of other organisms. With a few exceptions, such as the Porifera , invertebrates generally have bodies composed of differentiated tissues. There is also typically a digestive chamber with one or two openings to the exterior. The body plans of most multicellular organisms exhibit some form of symmetry , whether radial, bilateral, or spherical. A minority, however, exhibit no symmetry. One example of asymmetric invertebrates includes all gastropod species. This

2898-495: The hardened exoskeleton. The Nematoda , or roundworms, are perhaps the second largest animal phylum, and are also invertebrates. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the Kinorhyncha , Priapulida , and Loricifera . These groups have a reduced coelom, called a pseudocoelom. Other invertebrates include

2961-474: The head or elsewhere, depending on the insect family . The tympanal organs of some insects are extremely sensitive, offering acute hearing beyond that of most other animals. The female cricket fly Ormia ochracea has tympanal organs on each side of her abdomen. They are connected by a thin bridge of exoskeleton and they function like a tiny pair of eardrums, but, because they are linked, they provide acute directional information. The fly uses her "ears" to detect

3024-529: The notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan . Despite this, the concept of invertebrates as a taxon of animals has persisted for over a century among the laity , and within the zoological community and in its literature it remains in use as a term of convenience for animals that are not members of the Vertebrata. The following text reflects earlier scientific understanding of

3087-705: The only reason a homoplasy is recognizable in the first place is because there are other characters that imply a pattern of relationships that reveal its homoplastic distribution. A cladogram is the diagrammatic result of an analysis, which groups taxa on the basis of synapomorphies alone. There are many other phylogenetic algorithms that treat data somewhat differently, and result in phylogenetic trees that look like cladograms but are not cladograms. For example, phenetic algorithms, such as UPGMA and Neighbor-Joining, group by overall similarity, and treat both synapomorphies and symplesiomorphies as evidence of grouping, The resulting diagrams are phenograms, not cladograms, Similarly,

3150-429: The order of evolution of various features, adaptation, and other evolutionary narratives about ancestors. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational phylogenetics are now very commonly used in the generation of cladograms, either on their own or in combination with morphology. The characteristics used to create

3213-563: The original two groups into ten, by splitting Arachnida and Crustacea from the Linnean Insecta, and Mollusca, Annelida, Cirripedia , Radiata , Coelenterata and Infusoria from the Linnean Vermes. They are now classified into over 30 phyla , from simple organisms such as sea sponges and flatworms to complex animals such as arthropods and molluscs. Invertebrates are animals without a vertebral column. This has led to

SECTION 50

#1732775697563

3276-422: The other. If a male fiddler loses its large claw, it will grow another on the opposite side after moulting . Sessile animals such as sponges are asymmetrical alongside coral colonies (with the exception of the individual polyps that exhibit radial symmetry); Alpheidae claws that lack pincers; and some copepods , polyopisthocotyleans , and monogeneans which parasitize by attachment or residency within

3339-499: The problem of reversion that plagues sequence data. They are also generally assumed to have a low incidence of homoplasies because it was once thought that their integration into the genome was entirely random; this seems at least sometimes not to be the case, however. Researchers must decide which character states are "ancestral" ( plesiomorphies ) and which are derived ( synapomorphies ), because only synapomorphic character states provide evidence of grouping. This determination

3402-436: The program settles on a local minimum rather than the desired global minimum. To help solve this problem, many cladogram algorithms use a simulated annealing approach to increase the likelihood that the selected cladogram is the optimal one. The basal position is the direction of the base (or root) of a rooted phylogenetic tree or cladogram. A basal clade is the earliest clade (of a given taxonomic rank[a]) to branch within

3465-441: The respiratory system by means of active ventilation or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their haemolymph . A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices . In the head , thorax , or abdomen , tracheae may also be connected to air sacs. Many insects, such as grasshoppers and bees , which actively pump

3528-405: The results of model-based methods (Maximum Likelihood or Bayesian approaches) that take into account both branching order and "branch length," count both synapomorphies and autapomorphies as evidence for or against grouping, The diagrams resulting from those sorts of analysis are not cladograms, either. There are several algorithms available to identify the "best" cladogram. Most algorithms use

3591-460: The term parsimony for a specific kind of cladogram generation algorithm and sometimes as an umbrella term for all phylogenetic algorithms. Algorithms that perform optimization tasks (such as building cladograms) can be sensitive to the order in which the input data (the list of species and their characteristics) is presented. Inputting the data in various orders can cause the same algorithm to produce different "best" cladograms. In these situations,

3654-511: The term "invertebrates" rather polyphyletic , so the term has little meaning in taxonomy . The word "invertebrate" comes from the Latin word vertebra , which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. The jointed aspect of vertebra is derived from the concept of turning, expressed in the root verto or vorto , to turn. The prefix in- means "not" or "without". The term invertebrates

3717-411: The term and of those animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone, either internal or external. They include hugely varied body plans . Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms. Others have hard exoskeletons , outer shells like those of insects and crustaceans . The most familiar invertebrates include

3780-406: The tree. It is calculated by counting the minimum number of changes in a dataset and dividing it by the actual number of changes needed for the cladogram. A consistency index can also be calculated for an individual character i , denoted c i . Besides reflecting the amount of homoplasy, the metric also reflects the number of taxa in the dataset, (to a lesser extent) the number of characters in

3843-423: The user should input the data in various orders and compare the results. Using different algorithms on a single data set can sometimes yield different "best" cladograms, because each algorithm may have a unique definition of what is "best". Because of the astronomical number of possible cladograms, algorithms cannot guarantee that the solution is the overall best solution. A nonoptimal cladogram will be selected if

SECTION 60

#1732775697563

3906-410: Was not a major field of study until the work of Linnaeus and Lamarck in the 18th century. During the 20th century, invertebrate zoology became one of the major fields of natural sciences, with prominent discoveries in the fields of medicine, genetics, palaeontology, and ecology. The study of invertebrates has also benefited law enforcement, as arthropods, and especially insects, were discovered to be

3969-399: Was proposed as an improvement of the CI "for certain applications" This metric also purports to measure of the amount of homoplasy, but also measures how well synapomorphies explain the tree. It is calculated taking the (maximum number of changes on a tree minus the number of changes on the tree), and dividing by the (maximum number of changes on the tree minus the minimum number of changes in

#562437