A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
Mexico the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States. Covering 2,000,000 square kilometres, the nation is the fifth largest country in the Americas by total area and the 13th largest independent state in the world. With an estimated population of over 120 million people, the country is the eleventh most populous state and the most populous Spanish-speaking state in the world, while being the second most populous nation in Latin America after Brazil. Mexico is a federation comprising 31 states and Mexico City, a special federal entity, the capital city and its most populous city. Other metropolises in the state include Guadalajara, Puebla, Tijuana and León. Pre-Columbian Mexico dates to about 8000 BC and is identified as one of five cradles of civilization and was home to many advanced Mesoamerican civilizations such as the Olmec, Teotihuacan, Zapotec and Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its politically powerful base in Mexico-Tenochtitlan, administered as the viceroyalty of New Spain.
Three centuries the territory became a nation state following its recognition in 1821 after the Mexican War of Independence. The post-independence period was tumultuous, characterized by economic inequality and many contrasting political changes; the Mexican–American War led to a territorial cession of the extant northern territories to the United States. The Pastry War, the Franco-Mexican War, a civil war, two empires, the Porfiriato occurred in the 19th century; the Porfiriato was ended by the start of the Mexican Revolution in 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the country's current political system as a federal, democratic republic. Mexico has the 11th largest by purchasing power parity; the Mexican economy is linked to those of its 1994 North American Free Trade Agreement partners the United States. In 1994, Mexico became the first Latin American member of the Organisation for Economic Co-operation and Development, it is classified as an upper-middle income country by the World Bank and a newly industrialized country by several analysts.
The country is considered both a regional power and a middle power, is identified as an emerging global power. Due to its rich culture and history, Mexico ranks first in the Americas and seventh in the world for number of UNESCO World Heritage Sites. Mexico is an ecologically megadiverse country, ranking fourth in the world for its biodiversity. Mexico receives a huge number of tourists every year: in 2018, it was the sixth most-visited country in the world, with 39 million international arrivals. Mexico is a member of the United Nations, the World Trade Organization, the G8+5, the G20, the Uniting for Consensus group of the UN, the Pacific Alliance trade bloc. Mēxihco is the Nahuatl term for the heartland of the Aztec Empire, namely the Valley of Mexico and surrounding territories, with its people being known as the Mexica, it is believed to be a toponym for the valley which became the primary ethnonym for the Aztec Triple Alliance as a result, although it could have been the other way around.
In the colonial era, back when Mexico was called New Spain this territory became the Intendency of Mexico and after New Spain achieved independence from the Spanish Empire it came to be known as the State of Mexico with the new country being named after its capital: the City of Mexico, which itself was founded in 1524 on top of the ancient Mexica capital of Mexico-Tenochtitlan. Traditionally, the name Tenochtitlan was thought to come from Nahuatl tetl and nōchtli and is thought to mean "Among the prickly pears rocks". However, one attestation in the late 16th-century manuscript known as "the Bancroft dialogues" suggests the second vowel was short, so that the true etymology remains uncertain; the suffix -co is the Nahuatl locative, making the word a place name. Beyond that, the etymology is uncertain, it has been suggested that it is derived from Mextli or Mēxihtli, a secret name for the god of war and patron of the Mexica, Huitzilopochtli, in which case Mēxihco means "place where Huitzilopochtli lives".
Another hypothesis suggests that Mēxihco derives from a portmanteau of the Nahuatl words for "moon" and navel. This meaning might refer to Tenochtitlan's position in the middle of Lake Texcoco; the system of interconnected lakes, of which Texcoco formed the center, had the form of a rabbit, which the Mesoamericans pareidolically associated with the moon rabbit. Still another hypothesis suggests that the word is derived from Mēctli, the name of the goddess of maguey; the name of the city-state was transliterated to Spanish as México with the phonetic value of the letter x in Medieval Spanish, which represented the voiceless postalveolar fricative. This sound, as well as the voiced postalveolar fricative, represented by a j, evolved into a voiceless velar fricative during the 16th century; this led to the use of the variant Méjico in many publications in Spanish, most notably in Spain, whereas in Mexico and most other Spanish–speaking countries, México was the preferred spelling. In recent years, the Real Academia Española, which regulates the Spanish l
John Edward Gray
John Edward Gray, FRS was a British zoologist. He was the elder brother of zoologist George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray; the standard author abbreviation J. E. Gray is used to indicate this person as the author. Or zoological name. Gray was Keeper of Zoology at the British Museum in London from 1840 until Christmas 1874, before the Natural History holdings were split off to the Natural History Museum, he published several catalogues of the museum collections that included comprehensive discussions of animal groups as well as descriptions of new species. He improved the zoological collections to make them amongst the best in the world. Gray was born in Walsall, he assisted his father in writing The Natural Arrangement of British Plants. After being blackballed by the Linnean Society of London, Gray shifted his interest from botany to zoology, he began his zoological career by volunteering to collect insects for the British Museum at age 15. He joined the Zoological Department in 1824 to help John George Children catalog the reptile collection.
In some of his early articles, Gray adopted William Sharp Macleay's quinarian system for classifications of molluscs, echinoderms and mammals. In 1840 he took over Children's position as Keeper of Zoology, which he held for 35 years, publishing well over 1,000 papers, he named many cetacean species, genera and families. During this period he collaborated with Benjamin Waterhouse Hawkins, the noted natural history artist, in producing Gleanings from the Menagerie at Knowsley; the menagerie at Knowsley Hall, near Liverpool, founded by Edward Smith-Stanley, 13th Earl of Derby, at the Stanley ancestral seat, was one of the largest private menageries in Victorian England. Gray married Maria Emma Smith in 1826, she helped him with his scientific work with her drawings. In 1833, Gray was a founder of. Gray was a friend of the coleopterist Hamlet Clark, in 1856-57 they voyaged on Gray's yacht Miranda to Spain and Brazil. Gray was an accomplished watercolourist, his landscape paintings illustrate Clark's account of their journeys.
Gray was interested in postage stamps. On 1 May 1840, the day the Penny Black first went on sale, he purchased several with the intent to save them. During his fifty years employed at the British Museum Gray wrote nearly 500 papers, including many descriptions of species new to science; these had been presented to the Museum by collectors from around the world, included all branches of zoology, although Gray left the descriptions of new birds to his younger brother and colleague George. Gray was active in malacology, the study of molluscs. John Edward Gray was buried at Lewisham. Gray was one of the most prolific taxonomists in the history of zoology, he described more than 300 species and subspecies of reptiles, only surpassed by his successors at the British Museum, George A. Boulenger and Albert Günther and American zoologist Edward D. Cope. Gray described and named numerous marine snails including: The genus Lithopoma Gray, 1850 The genus Euthria Gray, 1850Genera named in his honour include: The snake genus Grayia Günther, 1858Species and subspecies named in his honour include: Ardeola grayii – Indian pond heron Mesoplodon grayi von Haast, 1876 – Gray's beaked whale Crocidura grayi Dobson, 1890 – Luzon shrew Ablepharus grayanus Delma grayii A. Smith, 1849 Microlophus grayii Naultinus grayii Bell, 1843 Salvelinus grayi Günther, 1862 Tropidophorus grayi Günther, 1861 Trachemys venusta grayi 1821: "A natural arrangement of Mollusca, according to their internal structure."
London Medical Repository 15: 229–239. 1821: "On the natural arrangement of Vertebrose Animals." London Medical Repository 15: 296–310. 1824: "A revision of the family Equidae." Zool. J. Lond. 1: 241-248 pl. 9. 1824: "On the natural arrangement of the pulmonobranchous Mollusca." Annals of Philosophy, 8: 107–109. 1824: "On the arrangement of the Papilionidae." Annals of Philosophy 8: 119-120. 1825: "A list and description of some species of shells not taken notice of by Lamarck." Annals of Philosophy 9: 407-415. 1825: "A synopsis of the genera of reptiles and Amphibia, with a description of some new species." Annals of Philosophy 10: 193-217. 1825: "An outline of an attempt at the disposition of the Mammalia into tribes and families with a list of the genera appertaining to each tribe." Annals of Philosophy 10: 337-344. 1825: "An attempt to divide the Echinida, or sea eggs, into natural families." Annals of Philosophy 10: 423-431. 1826: "Vertebrata. Mammalia.". P. 412-415 in King, P. P. Narrative of a Survey of the Intertropical and Western Coasts of Australia.
Performed between the years 1818 and 1822. With an Appendix, containing various subjects relating to hydrography and natural history. London: J. Murray Vol. 2. 1827: "Synopsis of the species of the class Mammalia." P. 1-391 in Baron Cuvier The Animal Kingdom Arranged in Conformity with its Organization, by the Baron Cuvier, with additional descriptions by Edward Griffith and others.. London: George B. Whittaker Vol. 5. 1828: "Spicilegia Zoologica, or original figures and short systematic descriptions of new and unfigured animals." Pt 1. London: Treuttel, Würtz & Co. 1829: "An attempt to improve the natural arrangement of the genera of bat, from actual examination. Phil. Mag
The saguaro is an arborescent cactus species in the monotypic genus Carnegiea, which can grow to be over 40 feet tall. It is native to the Sonoran Desert in Arizona, the Mexican State of Sonora, the Whipple Mountains and Imperial County areas of California; the saguaro blossom is the state wildflower of Arizona. Its scientific name is given in honor of Andrew Carnegie. In 1994, Saguaro National Park, near Tucson, was designated to help protect this species and its habitat; the image of the saguaro is indelibly linked with that of the American Southwest in western films. The common name saguaro came into the English language through the Spanish language, originating in the Mayo language. Saguaros have a long lifespan exceeding 150 years, they may grow their first side arm any time from 75 -- 100 years of age. A saguaro without arms is called a spear. Arms are developed to increase the plant's reproductive capacity, as more apices lead to more flowers and fruit. A saguaro is able to absorb and store considerable amounts of rainwater, visibly expanding in the process, while using the stored water as needed.
This characteristic enables the saguaro to survive during periods of drought. The saguaro is a columnar cactus that grow notable branches referred to as arms; as many as 25 arms may grow on one plant. They are slow growing but live to 150 or 200 years old, they are the largest cactus in the United States. Their roots are shallow yet wide, growing only to 6 inches deep, but extend as wide as the plant is tall; the growth rate of saguaros is dependent on precipitation. Saguaros grow from seed, never from cuttings, grow to be over 40 feet in height; the largest known living saguaro is the Champion Saguaro growing in Maricopa County, measuring 45.3 feet high with a girth of 10 feet. The tallest saguaro measured was an armless specimen found near Cave Creek, Arizona, it was 78 feet in height. When rain is plentiful and the saguaro is hydrated it can weigh between 3,200–4,800 pounds; the spines on a saguaro can grow up to 1 millimetre per day. When held up to the light or bisected, alternating light and dark bands transverse to the long axis of spines can be seen.
These transverse bands have been correlated to daily growth. In columnar cacti, spines always grow in areoles which originate at the apex of the plant. A spine stops growing in its first season. Areoles are moved to the side and the apex continues to grow upwards. Thus, older spines are towards the base of a columnar cactus and newer spines are near the apex. Studies are underway to examine the relationship of carbon and oxygen isotope ratios in the tissues of spines of an individual to its climate and photosynthetic history; the white, waxy flowers appear in April through June, opening well after sunset and closing in mid-afternoon. They continue to produce nectar after sunrise. Flowers are self-incompatible. Large quantities of pollen are required for complete pollination; this pollen is produced by the numerous stamens, which in one notable case totaled 3,482 in a single flower. A well-pollinated fruit contains several thousand tiny seeds. Saguaros have a redundant pollination system, i.e. full fruit set is possible if only a fraction of the pollinating species are present.
Main pollinators are honey bees and white-winged doves. In most years, diurnal visitors honey bees, are the main contributors for fruit. Other diurnal pollinators are birds such as Costa's hummingbird, the black-chinned hummingbird, the broad-billed hummingbird, the hooded oriole, Scott's oriole, the Gila woodpecker, the gilded flicker, the verdin, the house finch; the primary nocturnal pollinator is the lesser long-nosed bat. A number of floral characteristics are geared toward bat pollination: nocturnal opening of the flowers, nocturnal maturation of pollen rich nectar, position high above ground, durable blooms that can withstand a bat's weight, fragrance emitted at night. Further, the amino acids in the pollen appear to help sustain lactation in bats; the ruby red fruits are 2.4 to 3.5 inches long and ripen in June, each containing around 2,000 seeds, plus sweet, fleshy connective tissue. The fruits are prized by local people; the fruits are out of reach and are harvested using a pole 7 to 16 feet long, to the end of, attached a smaller pole, crosswise.
This pole is used to knock the fruits free. The O'odham tribes have a long history of saguaro fruit use; the Tohono O’odham tribes celebrate the beginning of their summer growing season with a ceremony using a fermented drink made from the bright red fruit, to summon rains vital for their crops. The saguaro genome is around 1 billion base pairs long. Sequencing has revealed that the genome of the saguaro's chloroplast is the smallest known among non-parasitic flowering plants. Saguaros are endemic to the Sonoran Desert and are found only in western Sonora in Mexico and in southern Arizona in the US – although plants are found in southeastern California. Elevation is a limiting factor to its environment, as the Saguaro is sensitive to extended frost or cold temperatures. No wild saguaros are found anywhere in New Mexico, Colorado, Utah, or Nevada, nor in the high deserts of northern Arizona. Native birds such as Gila woodpeckers
Larrea tridentata is known as creosote bush and greasewood as a plant, as chaparral as a medicinal herb, as gobernadora in Mexico, Spanish for "governess", due to its ability to secure more water by inhibiting the growth of nearby plants. In Sonora, it is more called hediondilla, it is a flowering plant in the family Zygophyllaceae. The specific name tridentata refers to its three-toothed leaves. Larrea tridentata is a prominent species in the Mojave and Chihuahuan Deserts of western North America, its range includes those and other regions in portions of southeastern California, southern Nevada, southwestern Utah, New Mexico, Texas in the United States, Chihuahua, Coahuila, Nuevo Leon, Zacatecas and San Luis Potosì in Mexico; the species grows as far east as Zapata County, along the Rio Grande southeast of Laredo near the 99th meridian west. Larrea tridentata is an evergreen shrub growing to 1 to 3 m tall 4 m; the stems of the plant bear resinous, dark green leaves with two opposite lanceolate leaflets joined at the base, with a deciduous awn between them, each leaflet 7 to 18 mm long and 4 to 8.5 mm broad.
The flowers are up to 25 mm with five yellow petals. Galls may form by the activity of the creosote gall midge; the whole plant exhibits a characteristic odor of creosote. In the regions where it grows, its smell is associated with the "smell of rain"; as the creosote bush grows older, its oldest branches die and its crown splits into separate crowns. This happens when the plant is 30 to 90 years old; the old crown dies and the new one becomes a clonal colony from the previous plant, composed of many separate stem crowns all from the same seed. The "King Clone" creosote ring is one of the oldest living organisms on Earth, it has been alive an estimated 11,700 years, in the central Mojave Desert near present-day Lucerne Valley, California. This single clonal colony plant of L. tridentata reaches up to 67 ft in diameter, with an average diameter of 45 ft. King Clone was identified and its age estimated by Frank Vasek, a professor at the University of California, Riverside. Measurements of the plant, as well as radiocarbon dating of wood fragments, were used to determine the plant's mean annual growth rate outward from the center of the ring.
By measuring the diameter of the ring, its total age could be estimated. It is within the Creosote Rings Preserve of the Lucerne Johnson Valley. Creosote bush is most common on the well-drained soils of alluvial flats. In parts of its range, it may cover large areas in pure stands, though it occurs in association with Ambrosia dumosa. Chemicals found in creosote bush roots have been shown to inhibit the growth of burro bush roots, but as of 2013, much of their relationship remains unexplained. Creosote bush stands tend to display an evenly spaced distribution of plants, it was assumed that the plant produced a water-soluble inhibitor that prevented the growth of other bushes near mature, healthy bushes. Now, however, it has been shown that the root systems of mature creosote plants are so efficient at absorbing water that fallen seeds nearby cannot accumulate enough water to germinate creating dead zones around every plant. Owing to the harshness of the germination environment above mature root systems, young creosote bushes are much more susceptible to drought stress than established plants.
Germination is quite active during wet periods, but most of the young plants die quickly unless water conditions are optimal. Ground heat compounds the young plants' susceptibility to water stress, ground temperatures can reach upwards of 70 °C. To become established, the young plant must experience three to five years of abnormally cool and moist weather during and after germination. From this, it can be inferred. Mature plants, can tolerate extreme drought stress. In terms of negative water potential, creosote bushes can operate at -50 bars of water potential and have been found living down to -120 bars, although the practical average floor is around -70 bars, where the plant's need for cellular respiration exceeds the level that the water-requiring process of photosynthesis can provide. Cell division can occur during these times of water stress, new cells quickly absorb water after rainfall; this rapid uptake causes branches to grow several centimeters at the end of a wet season. Water loss is reduced by the resinous waxy coating of the leaves, by their small size, which prevents them from heating above air temperature.
Plants drop some leaves heading into summer. Accumulation of fallen leaves, as well as other detritus caught from the passing wind, creates an ecological community specific to the creosote bush canopy, including beetles, pocket mice, kangaroo rats. Native Americans in the Southwest held beliefs that it treated many maladies, including sexually transmitted diseases, chicken pox and snakebite; the Coahuilla Indians used the plant for tuberculosis. The Pima drank a decoction of the leaves as an emetic, applied the boiled leaves as poultices to wounds or sores. Papago Indians prepared it medicinally for stiff limbs, snake bites, menstrual cramps; the shrub is still used as an herbal medicine in Mexico. Larrea tridentata is referred t