San Rafael, California
San Rafael is an affluent city and the county seat of Marin County, United States. The city is located in the North Bay region of the San Francisco Bay Area; as of the 2010 census the city's population is 57,713. What is now San Rafael was once the site of several Coast Miwok villages: Awani-wi, near downtown San Rafael, near Terra Linda and Shotomko-cha, in Marinwood. Mission San Rafael Arcángel was founded in what is now downtown San Rafael as the 20th Spanish mission in the colonial Mexican province of Alta California by three priests—Father Narciso Durán from Mission San José, Father Abella from Mission San Francisco de Asís, Father Luis Gíl y Taboada from La Iglesia de Nuestra Señora Reina de los Angeles—on Dec. 14, 1817, four years before Mexico gained independence from Spain. Mission San Rafael Arcángel was located a donkey's day walk to the mission below it; the mission and the city are named after the Angel of Healing. The mission was planned as a hospital site for Central Valley American Indians who had become ill at the cold San Francisco Mission Dolores.
Father Luis Gil, who spoke several Native American languages, was put in charge of the facility. In part because of its ideal weather, San Rafael was upgraded to full mission status in 1822; the mission had 300 converts within its first year, 1,140 converts by 1828. The Mexican government took over the California missions in 1834, Mission San Rafael was abandoned in 1844 falling into ruin; the current mission was built in 1949 in the style of the original, but faces at right angles to the alignment of the original. The San Francisco and North Pacific Railroad reached San Rafael in 1879 and was linked to the national rail network in 1888; the United States Navy operated a San Pablo Bay degaussing range from San Rafael through World War II. According to the United States Census Bureau, the city has a total area of 22.4 square miles. 16.5 square miles of it is land and 6.0 square miles of it is water. South of the county is San Francisco. Notable landmarks include: Mission San Rafael Arcángel, around which the city developed the Marin County Civic Center building, designed by Frank Lloyd Wright the Rafael Film Center China Camp State Park, Kerner Studios.
Peacock Gap Golf Course, open to the public. There are several public parks in the city; the San Rafael shoreline has been filled to a considerable extent to accommodate land development, with underlying bay mud of up to 90 feet in thickness. At certain locations such as Murphys Point, the sandstone or shale rock outcrops through the mud. San Rafael has a wide diversity of natural habitats from forests at the higher elevations to marshland and estuarine settings, its marshes are home to the endangered species Salt Marsh Harvest Mouse. There are riparian areas including the San Rafael Creek and Miller Creek corridors. San Rafael has a Mediterranean climate, with mild winter lows reaching the freezing mark; the National Weather Service reports that August is the warmest month with a high of 80.1 °F or 26.7 °C and a low of 55.0 °F or 12.8 °C. December, the coldest month, has an average high of 55.1 °F or 12.8 °C and an average low of 41.0 °F or 5.0 °C. The highest temperature on record is 110 °F, recorded in June 1961.
The highest temperature in recent years, 108 °F, occurred on July 23, 2006. The record lowest temperature was 20 °F on December 22, 1990. There are an average of 17.9 afternoons annually with a high of 90 °F or 32.2 °C or more and 1.2 afternoons with a high of 100 °F or 37.8 °C or more. Freezing temperatures occur on an average of 3.6 mornings. Total annual precipitation averages 32.16 inches or 816.9 millimetres, with an average of 64.3 days with measurable rain. The rainy season is from November to early April: rain is rare outside of this period and it is normal to receive no rain in June, July and September; the wettest “rain year” was from July 1994 to June 1995 with 61.45 inches and the driest from July 1975 to June 1976 with 13.62 inches. The most rain in one month was 24.11 inches in January 1995, the heaviest 24-hour rainfall was 8.74 inches on December 11, 1995. A trace of snow was recorded on January 30, 1976; the 2010 United States Census reported that the city of San Rafael had a population of 57,713.
This figure does not, include portions of the Santa Venetia and Lucas Valley-Marinwood CDPs, nor various other unincorporated areas, all of which have San Rafael postal addresses. The following statistics refer to the incorporated limits of San Rafael only; the population density was 2,573.9 people per square mile. The racial makeup of San Rafael was 40,734 White, 1,154 African American, 709 Native American, 3,513 Asian, 126 Pacific Islander, 8,513 from other races, 2,964 from two or more races. Hispanic or Latino of any race were 17,302 persons; the Census reported that 55,594 people lived in households, 1,314 lived in non-institutionalized group quarters, 805 were institutionalized. There were 22,764 households, out of which 6,358 had children under the age of 18 living in them, 9,845 were opposite-sex married couples living together, 2,004 had a female householder with no husband present, 1,133 had a male householder with no wife present. There were 1,450 unmarried opp
A wetland is a distinct ecosystem, inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, support of plants and animals. Wetlands are considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for assessing these functions, wetland ecological health, general wetland condition have been developed in many regions and have contributed to wetland conservation by raising public awareness of the functions and the ecosystem services some wetlands provide.
Wetlands occur on every continent. The main wetland types are swamp, marsh and fen. Many peatlands are wetlands; the water in wetlands is either brackish, or saltwater. Wetlands can be non-tidal; the largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, the Sundarbans in the Ganges-Brahmaputra delta. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff, they may play a role in water-sensitive urban design. A patch of land that develops pools of water after a rain storm would not be considered a "wetland" though the land is wet. Wetlands have unique characteristics: they are distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants.
A more concise definition is a community composed of hydric soil and hydrophytes. Wetlands have been described as ecotones, providing a transition between dry land and water bodies. Mitsch and Gosselink write that wetlands exist "...at the interface between terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet dependent on both."In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. A wetland is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota rooted plants, to adapt to flooding." There are four main kinds of wetlands – marsh, swamp and fen. Some experts recognize wet meadows and aquatic ecosystems as additional wetland types; the largest wetlands in the world include the swamp forests of the Amazon and the peatlands of Siberia. Under the Ramsar international wetland conservation treaty, wetlands are defined as follows: Article 1.1: "...wetlands are areas of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water, static or flowing, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."
Article 2.1: " may incorporate riparian and coastal zones adjacent to the wetlands, islands or bodies of marine water deeper than six metres at low tide lying within the wetlands." Although the general definition given above applies around the world, each county and region tends to have its own definition for legal purposes. In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands include swamps, marshes and similar areas"; this definition has been used in the enforcement of the Clean Water Act. Some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal government's. In the United States Code, the term wetland is defined "as land that has a predominance of hydric soils, is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation adapted for life in saturated soil conditions and under normal circumstances supports a prevalence of such vegetation."
Related to this legal definitions, the term "normal circumstances" are conditions expected to occur during the wet portion of the growing season under normal climatic conditions, in the absence of significant disturbance. It is not uncommon for a wetland to be dry for long portions of the growing season. Wetlands can be dry during the dry season and abnormally dry periods during the wet season, but under normal environmental conditions the soils in a wetland will be saturated to the surface or inundated such that the soils become anaerobic, those conditions will persist through the wet portion of the growing season; the most important factor producing wetlands is flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation
Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavior of animals in response to the environment where the animal lives. Behavioral ecologists use economic models to understand foraging, thus foraging theory is discussed in terms of optimizing a payoff from a foraging decision. The payoff for many of these models is the amount of energy an animal receives per unit time, more the highest ratio of energetic gain to cost while foraging. Foraging theory predicts that the decisions that maximize energy per unit time and thus deliver the highest payoff will be selected for and persist. Key words used to describe foraging behavior include resources, the elements necessary for survival and reproduction which have a limited supply, any organism that consumes others, prey, an organism, eaten in part or whole by another.
Behavioral ecologists first tackled this topic in the 1970s. Their goal was to quantify and formalize a set of models to test their null hypothesis that animals forage randomly. Important contributions to foraging theory have been made by: Eric Charnov, who developed the marginal value theorem to predict the behavior of foragers using patches. Learning is defined as an adaptive change or modification of a behavior based on a previous experience. Since an animal's environment is changing, the ability to adjust foraging behavior is essential for maximization of fitness. Studies in social insects have shown that there is a significant correlation between learning and foraging performance. In nonhuman primates, young individuals learn foraging behavior from their peers and elders by watching other group members forage and by copying their behavior. Observing and learning from other members of the group ensure that the younger members of the group learn what is safe to eat and become proficient foragers.
One measure of learning is'foraging innovation'—an animal consuming new food, or using a new foraging technique in response to their dynamic living environment. Foraging innovation is considered learning because it involves behavioral plasticity on the animal's part; the animal recognizes the need to come up with a new foraging strategy and introduce something it has never used before to maximize his or her fitness. Forebrain size has been associated with learning behavior. Animals with larger brain sizes are expected to learn better. A higher ability to innovate has been linked to larger forebrain sizes in North American and British Isle birds according to Lefebvre et al.. In this study, bird orders that contained individuals with larger forebrain sizes displayed a higher amount of foraging innovation. Examples of innovations recorded in birds include following tractors and eating frogs or other insects killed by it and using swaying trees to catch their prey. Another measure of learning is spatio-temporal learning, which refers to an individual's ability to associate the time of an event with the place of that event.
This type of learning has been documented in the foraging behaviors of individuals of the stingless bee species Trigona fulviventris. Studies showed that T. fulviventris individuals learned the locations and times of feeding events, arrived to those locations up to thirty minutes before the feeding event in anticipation of the food reward. Foraging behavior can be influenced by genetics; the genes associated with foraging behavior have been studied in honeybees with reference to the following. Honey bee foraging activity occurs both inside and outside the hive for either nectar. Similar behavior is seen in many social wasps, such as the species Apoica flavissima. Studies using quantitative trait loci mapping have associated the following loci with the matched functions; the presence of predators while a animal is foraging affects its behaviour. In general, foragers balance the risk of predation with their needs, thus deviating from the foraging behaviour that would be expected in the absence of predators.
An example of this balanced risk can be observed in the foraging behavior of A. longimana. Parasitism can affect the way in which animals forage. Parasitism can affect foraging at several levels. Animals might avoid food items that increase their risk of being parasitized, as when the prey items are intermediate hosts of parasites. Animals might avoid areas that would expose them to a high risk of parasitism. Animals might self-medicate, either prophylactically or therapeutically. Foraging can be categorized into two main types; the first is solitary foraging. The second is group foraging. Group foraging includes when animals can be seen foraging together when it is beneficial for them to do so and when it is detrimental for them to do so. Solitary foraging the v
A clutch of eggs is the group of eggs produced by birds, amphibians, or reptiles at a single time those laid in a nest. In birds, destruction of a clutch by predators results in double-clutching; the technique is used to double the production of a species' eggs, in the California condor case to increase population size. The act of putting one's hand in a nest to remove eggs is known as "dipping the clutch". Clutch size differs between species, sometimes within the same genus, it may differ within the same species due to many factors including habitat, nutrition, predation pressures, time of year. Clutch size variation can reflect variation in optimal reproduction effort. In birds, clutch size can vary within a species due to various features, while some species are determinant layers, laying a species-specific number of eggs. Long-lived species tend to have smaller clutch sizes than short-lived species; the evolution of optimal clutch size is driven by other factors, such as parent–offspring conflict.
In birds, ornithologist David Lack carried out much research into regulation of clutch size. In species with altricial young, he proposed that optimal clutch size was determined by the number of young a parent could feed until fledgling. In precocial birds, Lack determined that clutch size was determined by the nutrients available to egg-laying females. An experimental study in Black Brent Geese, which lay more than 5 eggs, found that the probability of an egg leading to a fledged gosling declined from 0.81 for two-egg clutches to 0.50 for seven-egg clutches, whilst the nesting period increased with the increasing number of eggs laid. This suggests. Oology Viviparity
A snail is, in loose terms, a shelled gastropod. The name is most applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is used for most of the members of the molluscan class Gastropoda that have a coiled shell, large enough for the animal to retract into; when the word "snail" is used in this most general sense, it includes not just land snails but numerous species of sea snails and freshwater snails. Gastropods that lack a shell, or have only an internal shell, are called slugs, land snails that have only a small shell are called semi-slugs. Snails have considerable human relevance, including as food items, as pests, as vectors of disease, their shells are used as decorative objects and are incorporated into jewelry; the snail has had some cultural significance, has been used as a metaphor. Snails that respire using a lung belong to the group Pulmonata; as traditionally defined, the Pulmonata were found to be polyphyletic in a molecular study per Jörger et al. dating from 2010.
But snails with gills form a polyphyletic group. Both snails that have lungs and snails that have gills have diversified so over geological time that a few species with gills can be found on land and numerous species with lungs can be found in freshwater. A few marine species have lungs. Snails can be found in a wide range of environments, including ditches and the abyssal depths of the sea. Although land snails may be more familiar to laymen, marine snails constitute the majority of snail species, have much greater diversity and a greater biomass. Numerous kinds of snail can be found in fresh water. Most snails have thousands of microscopic tooth-like structures located on a banded ribbon-like tongue called a radula; the radula works like a file. Many snails are herbivorous, eating plants or rasping algae from surfaces with their radulae, though a few land species and many marine species are omnivores or predatory carnivores. Snails cannot absorb colored pigments when eating paper or cardboard so their feces are colored.
Several species of the genus Achatina and related genera are known as giant African land snails. The largest living species of sea snail is Syrinx aruanus; the snail Lymnaea makes decisions by using only two types of neuron: one deciding whether the snail is hungry, the other deciding whether there is food in the vicinity. The largest known land gastropod is the African giant snail Achatina achatina, the largest recorded specimen of which measured 39.3 centimetres from snout to tail when extended, with a shell length of 27.3 cm in December 1978. It weighed 900 g. Named Gee Geronimo, this snail was owned by Christopher Hudson of Hove, East Sussex, UK, was collected in Sierra Leone in June 1976. Gastropods that lack a conspicuous shell are called slugs rather than snails; some species of slug have a red shell, some have only an internal vestige that serves as a calcium repository, others have no shell at all. Other than that there is little morphological difference between slugs and snails. There are however important differences in habitats and behavior.
A shell-less animal is much more maneuverable and compressible, so quite large land slugs can take advantage of habitats or retreats with little space, retreats that would be inaccessible to a similar-sized snail. Slugs squeeze themselves into confined spaces such as under loose bark on trees or under stone slabs, logs or wooden boards lying on the ground. In such retreats they are in less danger from either predators or desiccation, those are suitable places for laying their eggs. Slugs as a group are far from monophyletic; the reduction or loss of the shell has evolved many times independently within several different lineages of gastropods. The various taxa of land and sea gastropods with slug morphology occur within numerous higher taxonomic groups of shelled species. Land snails are known as an agricultural and garden pest but some species are an edible delicacy and household pets. There are a variety of snail-control measures that gardeners and farmers use in an attempt to reduce damage to valuable plants.
Traditional pesticides are still used, as are many less toxic control options such as concentrated garlic or wormwood solutions. Copper metal is a snail repellent, thus a copper band around the trunk of a tree will prevent snails from climbing up and reaching the foliage and fruit. Placing crushed egg shells on the soil around garden plants can deter snails from coming to the plants; the decollate snail will capture and eat garden snails, because of this it has sometimes been introduced as a biological pest control agent. However, this is not without problems, as the decollate snail is just as to attack and devour other gastropods that may represent a valuable part of the native fauna of the region. In French cuisine, edible snails are served for instance in Escargot à la Bourguignonne; the practice of rearing snails for food is known as heliciculture. For purposes of cultivation, the snails are kept in a
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
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