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15.3: Characteristics of Chordates - Biology


Learning Objectives

  • Describe the distinguishing characteristics of chordates

Vertebrates are members of the kingdom Animalia and the phylum Chordata (Figure 1). Recall that animals that possess bilateral symmetry can be divided into two groups—protostomes and deuterostomes—based on their patterns of embryonic development. The deuterostomes, whose name translates as “second mouth,” consist of two phyla: Chordata and Echinodermata. Echinoderms are invertebrate marine animals that have pentaradial symmetry and a spiny body covering, a group that includes sea stars, sea urchins, and sea cucumbers. The most conspicuous and familiar members of Chordata are vertebrates, but this phylum also includes two groups of invertebrate chordates.

Characteristics of Chordata

Animals in the phylum Chordata share four key features that appear at some stage during their development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail (Figure 2). In some groups, some of these are present only during embryonic development.

The chordates are named for the notochord, which is a flexible, rod-shaped structure that is found in the embryonic stage of all chordates and in the adult stage of some chordate species. It is located between the digestive tube and the nerve cord, and provides skeletal support through the length of the body. In some chordates, the notochord acts as the primary axial support of the body throughout the animal’s lifetime. In vertebrates, the notochord is present during embryonic development, at which time it induces the development of the neural tube and serves as a support for the developing embryonic body. The notochord, however, is not found in the postnatal stage of vertebrates; at this point, it has been replaced by the vertebral column (that is, the spine).

The dorsal hollow nerve cord derives from ectoderm that rolls into a hollow tube during development. In chordates, it is located dorsal to the notochord. In contrast, other animal phyla are characterized by solid nerve cords that are located either ventrally or laterally. The nerve cord found in most chordate embryos develops into the brain and spinal cord, which compose the central nervous system.

Pharyngeal slits are openings in the pharynx (the region just posterior to the mouth) that extend to the outside environment. In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth. In vertebrate fishes, the pharyngeal slits are modified into gill supports, and in jawed fishes, into jaw supports. In tetrapods, the slits are modified into components of the ear and tonsils. Tetrapod literally means “four-footed,” which refers to the phylogenetic history of various groups that evolved accordingly, even though some now possess fewer than two pairs of walking appendages. Tetrapods include amphibians, reptiles, birds, and mammals.

The post-anal tail is a posterior elongation of the body, extending beyond the anus. The tail contains skeletal elements and muscles, which provide a source of locomotion in aquatic species, such as fishes. In some terrestrial vertebrates, the tail also helps with balance, courting, and signaling when danger is near. In humans, the post-anal tail is vestigial, that is, reduced in size and nonfunctional.

Practice Question

Which of the following statements about common features of chordates is true?

  1. The dorsal hollow nerve cord is part of the chordate central nervous system.
  2. In vertebrate fishes, the pharyngeal slits become the gills.
  3. Humans are not chordates because humans do not have a tail.
  4. Vertebrates do not have a notochord at any point in their development; instead, they have a vertebral column.

[reveal-answer q=”97577″]Show Answer[/reveal-answer]
[hidden-answer a=”97577″]Statement a is true.[/hidden-answer]

Watch this video discussing the evolution of chordates and five characteristics that they share.

A link to an interactive elements can be found at the bottom of this page.


15.3: Characteristics of Chordates - Biology

Vertebrates are members of the kingdom Animalia and the phylum Chordata (Figure 1). The vertebrates exhibit two major innovations in their evolution from the invertebrate chordates. These innovations may be associated with the whole genome duplications that resulted in a quadruplication of the basic chordate genome, including the Hox gene loci that regulate the placement of structures along the three axes of the body. One of the first major steps was the emergence of the quadrupeds in the form of the amphibians. A second step was the evolution of the amniotic egg, which, similar to the evolution of pollen and seeds in plants, freed terrestrial animals from their dependence on water for fertilization and embryonic development. Within the amniotes, modifications of keratinous epidermal structures have given rise to scales, claws, hair, and feathers. The scales of reptiles sealed their skins against water loss, while hair and feathers provided insulation to support the evolution of endothermy, as well as served other functions such as camouflage and mate attraction in the vertebrate lineages that led to birds and mammals.

Figure 1. All chordates are deuterostomes possessing a notochord.


Visual Connection Questions

Figure 15.3 Which of the following statements is false?

  1. Eumetazoa have specialized tissues and Parazoa do not.
  2. Both acoelomates and pseudocoelomates have a body cavity.
  3. Chordates are more closely related to echinoderms than to rotifers according to the figure.
  4. Some animals have radial symmetry, and some animals have bilateral symmetry.

Figure 15.24 Which of the following statements about the anatomy of a mollusk is false?

  1. Mollusks have a radula for scraping food.
  2. Mollusks have ventral nerve cords.
  3. The tissue beneath the shell is called the mantle.
  4. The mantle cavity contains hemolymph.

Figure 15.33 Which of the following statements about common features of chordates is true?

  1. The dorsal hollow nerve cord is part of the chordate central nervous system.
  2. In vertebrate fishes, the pharyngeal slits become the gills.
  3. Humans are not chordates because humans do not have a tail.
  4. Vertebrates do not have a notochord at any point in their development instead, they have a vertebral column.

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    The Second Law of Thermodynamics

    A living cell’s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers that we have discussed, along with all energy transfers and transformations in the universe, is completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, scientists define heat energy as energy that transfers from one system to another that is not doing work. For example, when an airplane flies through the air, it loses some of its energy as heat energy due to friction with the surrounding air. This friction actually heats the air by temporarily increasing air molecule speed. Likewise, some energy is lost as heat energy during cellular metabolic reactions. This is good for warm-blooded creatures like us, because heat energy helps to maintain our body temperature. Strictly speaking, no energy transfer is completely efficient, because some energy is lost in an unusable form.

    An important concept in physical systems is that of order and disorder (or randomness). The more energy that a system loses to its surroundings, the less ordered and more random the system. Scientists refer to the measure of randomness or disorder within a system as entropy . High entropy means high disorder and low energy ((Figure)). To better understand entropy, think of a student’s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be put into the system, in the form of the student doing work and putting everything away, in order to bring the room back to a state of cleanliness and order. This state is one of low entropy. Similarly, a car or house must be constantly maintained with work in order to keep it in an ordered state. Left alone, a house’s or car’s entropy gradually increases through rust and degradation. Molecules and chemical reactions have varying amounts of entropy as well. For example, as chemical reactions reach a state of equilibrium, entropy increases, and as molecules at a high concentration in one place diffuse and spread out, entropy also increases.


    The Invertebrates

    Objectives for the chapter and helpful videos/songs/charts are listed below. This is not an all inclusive list of the content, but it is an excellent place to start or review! The videos are used as a study tool and may cover more or less than what we will cover in class. I will not test you on anything we did not cover in class, unless stated otherwise.

    Introduction to the Animal Kingdom

    Characteristics of the Kingdom Animalia 15.1 (Pg. 341-342)

    1. Demonstrate an understanding of the nine major characteristics of kingdom Animalia by giving examples of each

    Basic Anatomy of Animals 15.2 (Pg. 342-344)

    1. Distinguish between the three types of symmetry seen in animals
    2. Apply relative terms to familiar examples of animal symmetry and anatomy
    3. Recognize the relative abundance of species among the major phyla and classes of animals

    Poriferans and Cnidarians

    Phylum Porifera: The Sponges 15.3 (Pg.345-347)

    1. Trace the path of water and food through a typical sponge
    2. Describe how a sponge’s body is supported
    3. Contrast asexual and sexual reproduction in sponges

    Phylum Cnidaria 15.4 (Pg. 347-351)

    1. Describe the two different cnidaria body forms
    2. Summarize how the cnidocytes function in capturing prey
    3. Compare reproduction in the hydra and Aurelia

    The Worms

    Phylum Platyhelminthes: The Flatworms 15.5 (Pg. 351-357)


    Contents

    Felis rufa was the scientific name proposed by Johann Christian Daniel von Schreber in 1777. [2] In the 19th and 20th centuries, the following zoological specimens were described: [3]

    • Lynx floridanus proposed by Constantine Samuel Rafinesque in 1817 was a greyish lynx with yellowish brown spots from Florida. [4]
    • Lynx fasciatus also proposed by Rafinesque in 1817 was a reddish brown lynx with a thick fur from the northwest coast. [4]
    • Lynx baileyi proposed by Clinton Hart Merriam in 1890 was a female lynx that was shot in the San Francisco Mountains. [5]
    • Lynx texensis proposed by Joel Asaph Allen in 1895 to replace the earlier name Lynx rufus var. maculatus. [6]
    • Lynx gigas proposed by Outram Bangs in 1897 was a skin of an adult male lynx shot near Bear River, Nova Scotia. [7]
    • Lynx rufus eremicus and Lynx rufus californicus proposed by Edgar Alexander Mearns in 1898 were skins and skulls of two adult lynxes killed in San Diego County, California. [8]
    • Lynx rufus peninsularis proposed by Oldfield Thomas in 1898 was a skull and a pale rufous skin of a male lynx from Baja California Peninsula. [9]
    • Lynx fasciatus pallescens proposed by Merriam in 1899, was a skin of a gray lynx that was killed near Trout Lake, Washington. [10]
    • Lynx ruffus escuinapae proposed by Allen in 1903 was a skull and a pale rufous skin of an adult female from Escuinapa Municipality in Mexico. [11]
    • Lynx rufus superiorensis by Randolph Lee Peterson and Stuart C. Downing in 1952 was a skeleton and skin of a male lynx killed near Port Arthur, Ontario. [12]
    • Lynx rufus oaxacensis proposed by George Goodwin in 1963 was based on three skulls and six skins of lynxes killed in the Mexican Tehuantepec District. [13]

    The validity of these subspecies was challenged in 1981 because of the minor differences between specimens from the various geographic regions in North America. [14]

    Since the revision of cat taxonomy in 2017, only two subspecies are recognised as valid taxa: [15]

    • L. r. rufus – east of the Great Plains
    • L. r. fasciatus – west of the Great Plains

    Phylogeny Edit

    The genus Lynx shares a clade with the genera Puma, Prionailurus and Felis dated to 7.15 million years ago Lynx diverged approximately 3.24 million years ago . [16]

    The bobcat is thought to have evolved from the Eurasian lynx (L. lynx), which crossed into North America by way of the Bering Land Bridge during the Pleistocene, with progenitors arriving as early as 2.6 million years ago. [17] It first appeared during the Irvingtonian stage around 1.8 million years ago . The first bobcat wave moved into the southern portion of North America, which was soon cut off from the north by glaciers the population evolved into the modern bobcat around 20,000 years ago. A second population arrived from Asia and settled in the north, developing into the modern Canada lynx (L. canadensis). [18] Hybridization between the bobcat and the Canada lynx may sometimes occur. [19] The populations east and west of the Great Plains were probably separated during Pleistocene interglacial periods due to the aridification of the region. [20]

    The bobcat resembles other species of the midsize genus Lynx, but is on average the smallest of the four. Its coat is variable, though generally tan to grayish-brown, with black streaks on the body and dark bars on the forelegs and tail. Its spotted patterning acts as camouflage. The ears are black-tipped and pointed, with short, black tufts. Generally, an off-white color is seen on the lips, chin, and underparts. Bobcats in the desert regions of the southwest have the lightest-colored coats, while those in the northern, forested regions are darkest. Kittens are born well-furred and already have their spots. [21] A few melanistic bobcats have been sighted and captured in Florida, USA and New Brunswick, Canada. [22] They appear black, but may still exhibit a spot pattern. [23]

    The face appears wide due to ruffs of extended hair beneath the ears. Bobcat eyes are yellow with round, black pupils. The nose of the bobcat is pinkish-red, and it has a base color of gray or yellowish- or brownish-red on its face, sides, and back. [24] The pupils are round, black circles and will widen during nocturnal activity to maximize light reception. [25] The cat has sharp hearing and vision, and a good sense of smell. It is an excellent climber, and swims when it needs to, but normally avoids water. [26]

    The adult bobcat is 47.5 to 125 cm (18.7 to 49.2 in) long from the head to the base of its distinctive stubby tail, averaging 82.7 cm (32.6 in) the tail is 9 to 20 cm (3.5 to 7.9 in) long. [24] Its "bobbed" appearance gives the species its name. [27] [28] [29] [30] An adult stands about 30 to 60 cm (12 to 24 in) at the shoulders. [21]

    Adult males can range in weight from 6.4 to 18.3 kg (14 to 40 lb), with an average of 9.6 kg (21 lb) females at 4 to 15.3 kg (8.8 to 33.7 lb), with an average of 6.8 kg (15 lb). [31] The largest bobcat accurately measured on record weighed 22.2 kg (49 lb), although unverified reports have them reaching 27 kg (60 lb). [32] Furthermore, a June 20, 2012 report of a New Hampshire roadkill specimen listed the animal's weight at 27 kg (60 lb). [33] The largest-bodied bobcats were recorded in eastern Canada and northern New England, and the smallest in the southern Appalachian Mountains. [34] Skeletal muscles make up 56% of the bobcat's body weight. [35] At birth, it weighs 0.6 to 0.75 lb (0.27 to 0.34 kg) and is about 25 cm (10 in) in length. At the age of one year, it weighs about 4.5 kg (10 lb). [26]

    Consistent with Bergmann's rule, the bobcat is larger in its northern range and in open habitats. [36] A morphological size comparison study in the eastern United States found a divergence in the location of the largest male and female specimens, suggesting differing selection constraints for the sexes. [37]

    Tracks Edit

    Bobcat tracks show four toes without claw marks, due to their retractile claws. The tracks range in size from 1 to 3 in (25 to 76 mm) the average is about 1.8 in (46 mm). [38] When walking or trotting, the tracks are spaced roughly 8 to 18 in (20 to 46 cm) apart. The bobcat can make great strides when running, often from 4 to 8 ft (1.2 to 2.4 m). [39]

    Like all cats, the bobcat 'directly registers', meaning its hind prints usually fall exactly on top of its fore prints. Bobcat tracks can be generally distinguished from feral or house cat tracks by their larger size: about 2 in 2 (13 cm 2 ) versus 1.5 in 2 (9.7 cm 2 ). [40]

    The bobcat is an adaptable species. It prefers woodlands—deciduous, coniferous, or mixed—but does not depend exclusively on the deep forest. It ranges from the humid swamps of Florida to desert lands of Texas or rugged mountain areas. It makes its home near agricultural areas, if rocky ledges, swamps, or forested tracts are present its spotted coat serves as camouflage. [41] The population of the bobcat depends primarily on the population of its prey other principal factors in the selection of habitat type include protection from severe weather, availability of resting and den sites, dense cover for hunting and escape, and freedom from disturbance. [42]

    The bobcat's range does not seem to be limited by human populations, but by availability of suitable habitat only large, intensively cultivated tracts are unsuitable for the species. [36] The animal may appear in back yards in "urban edge" environments, where human development intersects with natural habitats. [43] If chased by a dog, it usually climbs up a tree. [41]

    The historical range of the bobcat was from southern Canada, throughout the United States, and as far south as the Mexican state of Oaxaca, and it still persists across much of this area. In the 20th century, it was thought to have lost territory in the US Midwest and parts of the Northeast, including southern Minnesota, eastern South Dakota, and much of Missouri, mostly due to habitat changes from modern agricultural practices. [25] [36] [41] While thought to no longer exist in western New York and Pennsylvania, multiple confirmed sightings of bobcats (including dead specimens) have been recently reported in New York's Southern Tier and in central New York, and a bobcat was captured in 2018 on a tourist boat in Downtown Pittsburgh, Pennsylvania. [44] [45] In addition, bobcat sightings have been confirmed in northern Indiana, and one was killed near Albion, Michigan, in 2008. [46] In early March 2010, a bobcat was sighted (and later captured by animal control authorities) in a parking garage in downtown Houston. [47] By 2010, bobcats appear to have recolonized many states, occurring in every state in the continuous 48 except Delaware. [1]

    The bobcat population in Canada is limited due to both snow depth and the presence of the Canadian lynx. The bobcat does not tolerate deep snow, and waits out heavy storms in sheltered areas [48] it lacks the large, padded feet of the Canadian lynx and cannot support its weight on snow as efficiently. The bobcat is not entirely at a disadvantage where its range meets that of the larger felid: displacement of the Canadian lynx by the aggressive bobcat has been observed where they interact in Nova Scotia, while the clearing of coniferous forests for agriculture has led to a northward retreat of the Canadian lynx's range to the advantage of the bobcat. [36] In northern and central Mexico, the cat is found in dry scrubland and forests of pine and oak its range ends at the tropical southern portion of the country. [36]

    The bobcat is crepuscular, and is active mostly during twilight. It keeps on the move from three hours before sunset until about midnight, and then again from before dawn until three hours after sunrise. Each night, it moves from 2 to 7 mi (3.2 to 11.3 km) along its habitual route. [26] This behavior may vary seasonally, as bobcats become more diurnal during fall and winter in response to the activity of their prey, which are more active during the day in colder weather. [25]

    Social structure and home range Edit

    Bobcat activities are confined to well-defined territories, which vary in size depending on the sex and the distribution of prey. The home range is marked with feces, urine scent, and by clawing prominent trees in the area. [49] In its territory, the bobcat has numerous places of shelter, usually a main den, and several auxiliary shelters on the outer extent of its range, such as hollow logs, brush piles, thickets, or under rock ledges. Its den smells strongly of the bobcat. [41] The sizes of bobcats' home ranges vary significantly and ranges from 0.23 to 126 sq mi (0.60 to 326.34 km 2 ). [36] One study in Kansas found resident males to have ranges of roughly 8 sq mi (21 km 2 ), and females less than half that area. Transient bobcats were found to have home ranges of 22 sq mi (57 km 2 ) and less well-defined home ranges. Kittens had the smallest range at about 3 sq mi (7.8 km 2 ). [50] Dispersal from the natal range is most pronounced with males. [51]

    Reports on seasonal variation in range size have been equivocal. One study found a large variation in male range sizes, from 16 sq mi (41 km 2 ) in summer up to 40 sq mi (100 km 2 ) in winter. [41] Another found that female bobcats, especially those which were reproductively active, expanded their home range in winter, but that males merely shifted their range without expanding it, which was consistent with numerous earlier studies. [52] Other research in various American states has shown little or no seasonal variation. [50] [53] [54]

    Like most felines, the bobcat is largely solitary, but ranges often overlap. Unusual for cats, males are more tolerant of overlap, while females rarely wander into others' ranges. [52] Given their smaller range sizes, two or more females may reside within a male's home range. When multiple territories overlap, a dominance hierarchy is often established, resulting in the exclusion of some transients from favored areas. [41]

    In line with widely differing estimates of home range size, population density figures diverge from one to 38 bobcats per 10 sq mi (26 km 2 ) in one survey. [36] The average is estimated at one bobcat per 5 sq mi (13 km 2 ). [41] A link has been observed between population density and sex ratio. An unhunted population in California had a sex ratio of 2.1 males per female. When the density decreased, the sex ratio skewed to 0.86 males per female. Another study observed a similar ratio, and suggested the males may be better able to cope with the increased competition, and this helped limit reproduction until various factors lowered the density. [55]

    Hunting and diet Edit

    The bobcat is able to survive for long periods without food, but eats heavily when prey is abundant. During lean periods, it often preys on larger animals, which it can kill and return to feed on later. The bobcat hunts by stalking its prey and then ambushing with a short chase or pounce. Its preference is for mammals weighing about 1.5 to 12.5 lb (0.7 to 6 kg). Its main prey varies by region: in the eastern United States, it is the eastern cottontail and New England cottontail, and in the north, it is the snowshoe hare. When these prey species exist together, as in New England, they are the primary food sources of the bobcat. In the far south, the rabbits and hares are sometimes replaced by cotton rats as the primary food source. Birds up to the size of an adult trumpeter swan are also taken in ambushes while nesting, along with their fledglings and eggs. [56] The bobcat is an opportunistic predator that, unlike the more specialized Canada lynx, readily varies its prey selection. [36] Diet diversification positively correlates to a decline in numbers of the bobcat's principal prey the abundance of its main prey species is the main determinant of overall diet. [57]

    The bobcat hunts animals of different sizes, and adjusts its hunting techniques accordingly. With small animals, such as rodents (including squirrels, moles, muskrats, mice), birds, fish including small sharks, [58] and insects, it hunts in areas known to be abundant in prey, and will lie, crouch, or stand, and wait for victims to wander close. It then pounces, grabbing its prey with its sharp, retractable claws. For slightly larger animals, such as geese, ducks, rabbits, and hares, it stalks from cover and waits until prey comes within 20 to 35 ft (6.1 to 10.7 m) before rushing in to attack. Less commonly, it feeds on larger animals, such as young ungulates, and other carnivores, such as fishers (primarily female), foxes, minks, martens, skunks, raccoons, small dogs, and domesticated cats. [41] [59] [60] [61] [62] Bobcats are also occasional hunters of livestock and poultry. While larger species, such as cattle, and horses, are not known to be attacked, bobcats do present a threat to smaller ruminants, such as pigs, sheep and goats. According to the National Agricultural Statistics Service, bobcats killed 11,100 sheep in 2004, comprising 4.9% of all sheep predator deaths. [63] However, some amount of bobcat predation may be misidentified, as bobcats have been known to scavenge on the remains of livestock kills by other animals. [64]

    It has been known to kill deer or pronghorn, and sometimes to hunt elk in western North America, especially in winter when smaller prey is scarce, or when deer populations become more abundant. One study in the Everglades showed a large majority of kills (33 of 39) were fawns, According to the Yellowstone showed a large number of kills (15 of 20) were includes elk calves, but prey up to eight times the bobcat's weight could be successfully taken. [65] It stalks the deer, often when the deer is lying down, then rushes in and grabs it by the neck before biting the throat, base of the skull, or chest. On the rare occasions a bobcat kills a deer, it eats its fill and then buries the carcass under snow or leaves, often returning to it several times to feed. [41]

    The bobcat prey base overlaps with that of other midsized predators of a similar ecological niche. Research in Maine has shown little evidence of competitive relationships between the bobcat and coyote or red fox separation distances and territory overlap appeared random among simultaneously monitored animals. [66] However, other studies have found bobcat populations may decrease in areas with high coyote populations, with the more social inclination of the canid giving them a possible competitive advantage. [67] With the Canada lynx, however, the interspecific relationship affects distribution patterns competitive exclusion by the bobcat is likely to have prevented any further southward expansion of the range of its felid relative. [17]

    Reproduction and life cycle Edit

    The average lifespan of the bobcat is seven years but rarely exceeds 10 years. The oldest wild bobcat on record was 16 years old, and the oldest captive bobcat lived to be 32. [55]

    Bobcats generally begin breeding by their second summer, though females may start as early as their first year. Sperm production begins each year by September or October, and the male is fertile into the summer. A dominant male travels with a female and mates with her several times, generally from winter until early spring this varies by location, but most mating takes place during February and March. The pair may undertake a number of different behaviors, including bumping, chasing, and ambushing. Other males may be in attendance, but remain uninvolved. Once the male recognizes the female is receptive, he grasps her in the typical felid neck grip and mates with her. The female may later go on to mate with other males, [41] and males generally mate with several females. [68] During courtship, the bobcat's vocalizations include screaming and hissing. [69] Research in Texas revealed that establishing a home range is necessary for breeding studied animals without a home range had no identified offspring. [51] The female has an estrous cycle of 44 days, with the estrus lasting five to ten days. Bobcats remain reproductively active throughout their lives. [25] [68]

    The female raises the young alone. One to six, but usually two to four, kittens are born in April or May, after roughly 60 to 70 days of gestation. Sometimes, a second litter is born as late as September. The female generally gives birth in an enclosed space, usually a small cave or hollow log. The young open their eyes by the ninth or tenth day. They start exploring their surroundings at four weeks and are weaned at about two months. Within three to five months, they begin to travel with their mother. [69] They hunt by themselves by fall of their first year, and usually disperse shortly thereafter. [41] In Michigan, however, they have been observed staying with their mother as late as the next spring. [68]

    Predators Edit

    The adult bobcat has relatively few predators. However rarely, it may be killed in interspecific conflict by several larger predators or fall prey to them. Cougars and gray wolves can kill adult bobcats, a behavior repeatedly observed in Yellowstone National Park. [70] [71] Coyotes have killed adult bobcats and kittens. [72] [73] [74] At least one confirmed observation of a bobcat and an American black bear (Ursus americanus) fighting over a carcass is confirmed. [75] Like other Lynx species, bobcats probably avoid encounters with bears, in part because they are likely to lose kills to them or may rarely be attacked by them. [76] [77] Bobcat remains have occasionally been found in the resting sites of male fishers. [78] American alligators (Alligator mississippensis) have been filmed opportunistically preying on adult bobcats in the southeast United States. [79] [80]

    Kittens may be taken by several predators, including great horned owls, eagles, foxes, and bears, and other adult male bobcats. [81] When prey populations are not abundant, fewer kittens are likely to reach adulthood. Golden eagles (Aquila chrysaetos) have been reportedly observed preying on bobcats. [82]

    Diseases, accidents, hunters, automobiles, and starvation are the other leading causes of death. Juveniles show high mortality shortly after leaving their mothers, while still perfecting their hunting techniques. One study of 15 bobcats showed yearly survival rates for both sexes averaged 0.62, in line with other research suggesting rates of 0.56 to 0.67. [83] Cannibalism has been reported kittens may be taken when prey levels are low, but this is very rare and does not much influence the population. [55]

    The bobcat may have external parasites, mostly ticks and fleas, and often carries the parasites of its prey, especially those of rabbits and squirrels. Internal parasites (endoparasites) are especially common in bobcats. [84] One study found an average infection rate of 52% from Toxoplasma gondii, but with great regional variation. [85] One mite in particular, Lynxacarus morlani, has to date been found only on the bobcat. Parasites' and diseases' role in the mortality of the bobcat is still unclear, but they may account for greater mortality than starvation, accidents, and predation. [55]

    It is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), [86] which means it is not considered threatened with extinction, but hunting and trading must be closely monitored. The animal is regulated in all three of its range countries, and is found in a number of protected areas of the United States, its principal territory. [36] Estimates from the US Fish and Wildlife Service placed bobcat numbers between 700,000 and 1,500,000 in the US in 1988, with increased range and population density suggesting even greater numbers in subsequent years for these reasons, the U.S. has petitioned CITES to remove the cat from Appendix II. [42] Populations in Canada and Mexico remain stable and healthy. It is listed as least concern on the IUCN Red List, noting it is relatively widespread and abundant, but information from southern Mexico is poor. [1]

    The species is considered endangered in Ohio, Indiana, and New Jersey. It was removed from the threatened list of Illinois in 1999 and of Iowa in 2003. In Pennsylvania, limited hunting and trapping are once again allowed, after having been banned from 1970 to 1999. The bobcat also suffered population decline in New Jersey at the turn of the 19th century, mainly because of commercial and agricultural developments causing habitat fragmentation by 1972, the bobcat was given full legal protection, and was listed as endangered in the state in 1991. [25] L. r. escuinipae, the subspecies found in Mexico, was for a time considered endangered by the US Fish and Wildlife Service, but was delisted in 2005. [87] Between 2003 and 2011, a reduction in bobcat sightings in the Everglades by 87.5% has been attributed to predation by the invasive Burmese python. [88]

    The bobcat has long been valued both for fur and sport it has been hunted and trapped by humans, but has maintained a high population, even in the southern United States, where it is extensively hunted. In the 1970s and 1980s, an unprecedented rise in price for bobcat fur caused further interest in hunting, but by the early 1990s, prices had dropped significantly. [89] Regulated hunting still continues, with half of mortality of some populations being attributed to this cause. As a result, the rate of bobcat deaths is skewed in winter, when hunting season is generally open. [55]

    Urbanization can result in the fragmentation of contiguous natural landscapes into patchy habitat within an urban area. Animals that live in these fragmented areas often have reduced movement between the habitat patches, which can lead to reduced gene flow and pathogen transmission between patches. Animals such as the bobcat are particularly sensitive to fragmentation because of their large home ranges. [90] A study in coastal Southern California has shown bobcat populations are affected by urbanization, creation of roads, and other developments. The populations may not be declining as much as predicted, but instead the connectivity of different populations is affected. This leads to a decrease in natural genetic diversity among bobcat populations. [91] For bobcats, preserving open space in sufficient quantities and quality is necessary for population viability. Educating local residents about the animals is critical, as well, for conservation in urban areas. [92]

    In bobcats using urban habitats in California, the use of rodenticides has been linked to both secondary poisoning by consuming poisoned rats and mice, and to increased rates of severe mite infestation (known as notoedric mange), as an animal with a poison-weakened immune system is less capable of fighting off mange. Liver autopsies in California bobcats that have succumbed to notoedric mange have revealed chronic rodenticide exposure. [93] [94] Alternative rodent control measures such as vegetation control and use of traps have been suggested to alleviate this issue. [95]

    Stories featuring the bobcat, in many variations, are found in some Indigenous cultures of North America, with parallels in South America. A story from the Nez Perce, for instance, depicts the bobcat and coyote as opposed, antithetical beings. [96] However, another version depicts them with equality and identicality.

    In a Shawnee tale, the bobcat is outwitted by a rabbit, which gives rise to its spots. After trapping the rabbit in a tree, the bobcat is persuaded to build a fire, only to have the embers scattered on its fur, leaving it singed with dark brown spots. [97] The Mohave believed dreaming habitually of beings or objects would afford them their characteristics as supernatural powers. Dreaming of two deities, cougar and lynx, they thought, would grant them the superior hunting skills of other Tribes. [98] European-descended inhabitants of the Americas also admired the cat, both for its ferocity and its grace, and in the United States, it "rests prominently in the anthology of . national folklore." [99]

    Grave artifacts from dirt domes excavated in the 1980s along the Illinois River revealed a complete skeleton of a young bobcat along with a collar made of bone pendants and shell beads that had been buried by the Hopewell culture. The type and place of burial indicate a tamed and cherished pet or possible spiritual significance. The Hopewell normally buried their dogs, so the bones were initially identified as remains of a puppy, but dogs were usually buried close to the village and not in the mounds themselves. This is the only wild cat decorated burial on the archaeological record. [100] [101]


    Big Data Analytics in Medicine and Healthcare

    This paper surveys big data with highlighting the big data analytics in medicine and healthcare. Big data characteristics: value, volume, velocity, variety, veracity and variability are described. Big data analytics in medicine and healthcare covers integration and analysis of large amount of complex heterogeneous data such as various - omics data (genomics, epigenomics, transcriptomics, proteomics, metabolomics, interactomics, pharmacogenomics, diseasomics), biomedical data and electronic health records data. We underline the challenging issues about big data privacy and security. Regarding big data characteristics, some directions of using suitable and promising open-source distributed data processing software platform are given.

    Keywords: Big Data Analytics Data Mining Health Informatics Healthcare Information Systems.

    Conflict of interest statement

    Authors state no conflict of interest. All authors have read the journal’s Publication ethics and publication malpractice statement available at the journal’s website and hereby confirm that they comply with all its parts applicable to the present scientific work.


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    Background

    There are over 4,100 species of plant parasitic nematodes [1] which collectively are an important threat to global food security. Damage caused to crops worldwide by plant parasitic nematodes has been estimated at $80 billion per year [2]. The largest economic losses to agriculture are imposed by root-knot nematodes and cyst nematodes that both belong to the order Tylenchida. The most widespread and damaging species of root-knot nematodes have a wide host range and are prevalent in Mediterranean, subtropical and tropical regions while cyst nematode species have more restricted host ranges and the most damaging species are found predominantly in more temperate agricultural regions. Both root-knot and cyst nematodes are obligate, sedentary endoparasites that have unique, biotrophic interactions with their host plants. A central feature of the parasitism is the establishment and maintenance of a permanent feeding site that sustains the nematode throughout its growth in the plant [3]. However, biotrophic parasitism of plants by root-knot nematodes and cyst nematodes has evolved independently [4] and this is reflected in the different feeding structures of these nematodes.

    The most economically important cyst nematode species are within the Heterodera and Globodera genera. Cyst nematodes cause significant damage to a range of crops worldwide, particularly potato, soybean, wheat and rice. Potato cyst nematode (PCN) is the collective term for the two species G. pallida and G. rostochiensis that are restricted to infecting a few species of Solanaceous plants. PCN is a major pest of the potato crop in cool-temperate areas of the world. Yield losses of potato in excess of 50% due to PCN are reported in the literature (for example, [5]). Although PCN is indigenous to South America, it was introduced into Europe in the 19th century with potato material used for resistance breeding against late blight [6] and is now widely distributed in Europe [7]. From here, PCN has spread to all major potato growing areas of the world including Ukraine and, more recently, Idaho in the USA [8, 9]. Integrated pest management of G. pallida is based on partially resistant cultivars, crop rotation and nematicides. Resistance against the pathotypes of G. rostochiensis predominant in Europe is provided by the H1 gene, which is now available in many potato cultivars, for example, ‘Maris Piper’. However, the lack of a comparable single, dominant natural resistance gene for G. pallida has resulted in an emphasis on multi-trait quantitative resistance that is difficult to breed and is more readily overcome by virulent pathotypes. Repeated use of cultivars resistant to G. rostochiensis has selected for G. pallida in mixed populations [10]. The slow decline rate of the dormant soil population of G. pallida makes crop rotation an extremely inefficient management practice [11, 12]. Nematicides are thus currently essential to control G. pallida and allow favoured, susceptible potato cultivars to be grown at an economically viable cropping frequency. Recent legislation, however, has withdrawn or severely limited their use [13]. Consequently there is an urgent need to develop novel approaches for control of this and other cyst nematodes. Research in this direction will be significantly enhanced by a greater understanding of the molecular basis of the parasitic interaction and the key nematode genes required for this.

    Cyst nematodes hatch as second stage juveniles (J2) from eggs contained within cysts in the soil. This process is usually initiated in response to chemicals released from roots of a potential host plant. Upon locating host roots they use their stylet to disrupt the plant tissue and migrate intracellularly through cortical cells towards the vascular cylinder where an initial feeding cell is selected. The nematode secretes proteins from pharyngeal gland cells through the bore of the stylet into the initial feeding cell thus inducing the formation of a syncytial feeding site. Localised cell wall dissolution and protoplast fusion cause the syncytium to progressively enlarge until it eventually incorporates up to 200 neighbouring cells [14]. The syncytium develops wall ingrowths to facilitate water and nutrient uptake from the xylem and acts as a strong nutrient sink, with phloem solutes transported at first apoplasmically and later via plasmodesmata. The syncytium is continually stimulated by stylet secretions and provides the growing cyst nematode with all the nutrients required for development into an adult male or an egg-laying female, a process that takes 3 to 6 weeks. Sex is determined by the size of the syncytium that is induced and whether it gains access to vascular tissues in order to supply plentiful nutrients (reviewed by [15]). The cuticle of the mature female, harbouring eggs containing quiescent J2s within her body, is tanned by a polyphenol oxidase to form the tough cyst that protects the eggs. The cyst becomes detached from the root following death of the plant and the eggs within can remain viable for many years.

    Nematodes have been a focus of genomic projects since the 1990s when the free-living bacteriovore Caenorhabditis elegans became the first multicellular organism to have a completely sequenced genome [16]. This provided a valuable platform for genomics research in other nematode species, but it was a further decade before the first genome sequence became available for a parasitic nematode, the human filarial parasite Brugia malayi[17]. Genome sequences have subsequently been reported for a range of other nematode species [18–20], but only three plant parasitic nematodes: two root-knot nematode species [21] (Meloidogyne incognita[22] and M. hapla[23]) and most recently the pine wood nematode Bursaphelenchus xylophilus, a migratory endoparasite [24]. The draft genome sequence of G. pallida reported here is, to our knowledge, the first cyst nematode genome to be described and will serve as a valuable comparator for understanding the evolution of plant parasitism in nematodes. We describe the genome in detail, examining the gene content of G. pallida in the context of other published plant parasitic nematode genomes. Significantly, we use RNA-seq to examine changes in gene expression throughout the lifecycle of G. pallida, which provides important insights into the genes involved particularly in root invasion and establishment of the feeding site.


    Assortative mating

    Our editors will review what you’ve submitted and determine whether to revise the article.

    Assortative mating, in human genetics, a form of nonrandom mating in which pair bonds are established on the basis of phenotype (observable characteristics). For example, a person may choose a mate according to religious, cultural, or ethnic preferences, professional interests, or physical traits.

    Positive assortative mating, or homogamy, exists when people choose to mate with persons similar to themselves (e.g., when a tall person mates with a tall person) this type of selection is very common. Negative assortative mating is the opposite case, when people avoid mating with persons similar to themselves.

    Assortative mating also occurs in nonhuman animal populations. Indeed, phenotypic similarity is thought to underlie mate selection in a variety of species.

    This article was most recently revised and updated by Kara Rogers, Senior Editor.


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