The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, the longest period of the Phanerozoic Eon; the Cretaceous Period is abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas; these oceans and seas were populated with now-extinct marine reptiles and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared; the Cretaceous ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.
The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk, found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta; the Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use; as with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is defined, being placed at an iridium-rich layer found worldwide, believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico.
This layer has been dated at 66.043 Ma. A 140 Ma age for the Jurassic-Cretaceous boundary instead of the accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. From youngest to oldest, the subdivisions of the Cretaceous period are: Late Cretaceous Maastrichtian – Campanian – Santonian – Coniacian – Turonian – Cenomanian – Early Cretaceous Albian – Aptian – Barremian – Hauterivian – Valanginian – Berriasian – The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms; the Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type, formed under warm, shallow marine circumstances.
Due to the high sea level, there was extensive space for such sedimentation. Because of the young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide. Chalk is a rock type characteristic for the Cretaceous, it consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast; the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not consolidated and the Chalk Group still consists of loose sediments in many places; the group has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is a marine system consisting of competent limestone beds or incompetent marls.
Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean. Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval; these shales are an important source rock for oil and gas, for example in the subsurface of the North Sea. During th
Phthiracaridae is a family of oribatid mites in the order Oribatida. There are at least 710 described species in Phthiracaridae. Atropacarus Ewing, 1917 Hoplophorella Berlese, 1923 Hoplophthiracarus Jacot, 1933 Notophthiracarus Ramsay, 1966 Phthiracarus Perty, 1841 Rhacaplacarus Niedbala, 1986 Steganacarus Ewing, 1917
The Acari are a taxon of arachnids that contains mites and ticks. The diversity of the Acari is extraordinary and their fossil history goes back to at least the early Devonian period. Acarologists have proposed a complex set of taxonomic ranks to classify mites. In most modern treatments, the Acari are considered a subclass of the Arachnida and are composed of two or three superorders or orders: Acariformes and Opilioacariformes; the monophyly of the Acari is open to debate, the relationships of the acarines to other arachnids is not at all clear. In older treatments, the subgroups of the Acarina were placed at order rank, but as their own subdivisions have become better understood, treating them at the superorder rank is more usual. Most acarines are minute to small. Over 50,000 species have been described and an estimated million or more species may exist; the study of mites and ticks is called acarology, the leading scientific journals for acarology include Acarologia and Applied Acarology and the International Journal of Acarology.
Mites are arachnids, as such, evolved from a segmented body with the segments organised into two tagmata: a prosoma and an opisthosoma. However, only the faintest traces of primary segmentation remain in mites; this anterior body region is called the capitulum or gnathosoma, according to some works, is found in the Ricinulei. The remainder of the body is unique to mites. Most adult mites have four pairs of legs, like other arachnids. For example, gall mites like Phyllocoptes variabilis have a worm-like body with only two pairs of legs. Larval and prelarval stages have a maximum of three pairs of legs. Members of the Nematalycidae within the Endeostigmata, which live between sand grains, have worm-like and elongated bodies with reduced legs; the mouth parts of mites may be adapted for biting, sawing, or sucking. They breathe through tracheae, stigmata and the skin itself. Species hunting for other mites have acute senses, but many mites are eyeless; the central eyes of arachnids are always missing.
Thus, any eye number from none to five may occur. Acarine ontogeny consists of an egg, a prelarval stage, a larval stage, a series of nymphal stages. Any or all of these stages except the adult may be suppressed or occur only within the body of a previous stage. Larvae have a maximum of three pairs of legs. A maximum of three nymphal stages are present and they are referred to in sequence as the protonymph and tritonymph; the females of some Tarsonemidae bear sexually mature young. If any nymphal stages are absent authors may disagree on which stages are present. Only the Oribatida pass through all developmental stages. Acarines are diverse, they live in every habitat, include aquatic and terrestrial species. They detritus. Many are parasitic, they affect both vertebrates and invertebrates. Most parasitic forms are external parasites, while the free-living forms are predatory and may be used to control undesirable arthropods. Others are detritivores that help to break down forest litter and dead organic matter, such as skin cells.
Others still may damage crops. The feather mites, are found on all species of birds, except for penguins, are specialized for life on their hosts, they may feed on uropygial oil, skin flakes, fungus and feathers, depending on the taxon to which they belong. Their lifestyles are affected by the microclimate. However, no evidence shows microclimate affecting mite diversity. Damage to crops is the most costly economic effect of mites by the spider mites and their relatives, earth mites, thread-footed mites and the gall and rust mites; the honey bee parasite Varroa destructor has caused or contributed to large-scale die-offs of commercial pollinating populations. Some parasitic forms affect humans and other mammals, causing damage by their feeding, can be vectors of diseases, such as scrub typhus, Lyme disease, Q fever, Colorado tick fever, tick-borne relapsing fever, babesiosis and tick-borne meningoencephalitis. A well-known effect of mites on humans is their role as allergens and the stimulation of asthma in people affected by respiratory disease.
The use of predatory mites in pest control and herbivorous
An earthworm is a tube-shaped, segmented worm found in the phylum Annelida. They have a world-wide distribution and are found living in soil, feeding on live and dead organic matter. An earthworm's digestive system runs through the length of its body, it conducts respiration through its skin. It has a double transport system composed of coelomic fluid that moves within the fluid-filled coelom and a simple, closed blood circulatory system, it has a peripheral nervous system. The central nervous system consists of two ganglia above the mouth, one on either side, connected to a nerve cord running back along its length to motor neurons and sensory cells in each segment. Large numbers of chemoreceptors are concentrated near its mouth. Circumferential and longitudinal muscles on the periphery of each segment enable the worm to move. Similar sets of muscles line the gut, their actions move the digesting food toward the worm's anus. Earthworms are hermaphrodites: each individual carries both male and female sex organs.
As invertebrates, they lack either an internal skeleton or exoskeleton, but maintain their structure with fluid-filled coelom chambers that function as a hydrostatic skeleton. "Earthworm" is the common name for the largest members of Oligochaeta. In classical systems, they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, though the internal male segments are anterior to the female. Theoretical cladistic studies have placed them, instead, in the suborder Lumbricina of the order Haplotaxida, but this may again soon change. Folk names for the earthworm include "dew-worm", "rainworm", "night crawler", "angleworm". Larger terrestrial earthworms are called megadriles, as opposed to the microdriles in the semiaquatic families Tubificidae and Enchytraeidae, among others; the megadriles are characterized by having a distinct clitellum and a vascular system with true capillaries. Depending on the species, an adult earthworm can be from 10 mm long and 1 mm wide to 3 m long and over 25 mm wide, but the typical Lumbricus terrestris grows to about 360 mm long.
The longest worm on confirmed records is Amynthas mekongianus that extends up to 3 m in the mud along the banks of the 4,350 km Mekong River in Southeast Asia. From front to back, the basic shape of the earthworm is a cylindrical tube, divided into a series of segments that compartmentalize the body. Furrows are externally visible on the body demarking the segments. Except for the mouth and anal segments, each segment carries bristle-like hairs called lateral setae used to anchor parts of the body during movement. Special ventral setae are used to anchor mating earthworms by their penetration into the bodies of their mates. Within a species, the number of segments found is consistent across specimens, individuals are born with the number of segments they will have throughout their lives; the first body segment features both the earthworm's mouth and, overhanging the mouth, a fleshy lobe called the prostomium, which seals the entrance when the worm is at rest, but is used to feel and chemically sense the worm's surroundings.
Some species of earthworm can use the prehensile prostomium to grab and drag items such as grasses and leaves into their burrow. An adult earthworm develops a belt-like glandular swelling, called the clitellum, which covers several segments toward the front part of the animal; this produces egg capsules. The posterior is most cylindrical like the rest of the body, but depending on the species, may be quadrangular, trapezoidal, or flattened; the last segment is called the periproct. The exterior of an individual segment is a thin cuticle over skin pigmented red to brown, which has specialized cells that secrete mucus over the cuticle to keep the body moist and ease movement through soil. Under the skin is a layer of nerve tissue, two layers of muscles—a thin outer layer of circular muscle, a much thicker inner layer of longitudinal muscle. Interior to the muscle layer is a fluid-filled chamber called a coelom that by its pressurization provides structure to the worm's boneless body; the segments are separated from each other by septa which are perforated transverse walls, allowing the coelomic fluid to pass between segments.
A pair of structures called. This tubule leads to the main body fluid filtering organ, the nephridium or metanephridium, which removes metabolic waste from the coelomic fluid and expels it through pores called nephridiopores on the worm's sides. At the center of a worm is the digestive tract, which runs straight through from mouth to anus without coiling, is flanked above and below by blood vessels and the ventral nerve cord, is surrounded in each segment by a pair of pallial blood vessels that connect the dorsal to th
Carrion is the decaying flesh of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, eagles, Virginia opossum, Tasmanian devils and Komodo dragons. Many invertebrates, such as the carrion and burying beetles, as well as maggots of calliphorid flies and flesh-flies eat carrion, playing an important role in recycling nitrogen and carbon in animal remains. Carrion begins to decay at the moment of the animal's death, it will attract insects and breed bacteria. Not long after the animal has died, its body will begin to exude a foul odor caused by the presence of bacteria and the emission of cadaverine and putrescine; some plants and fungi attract insects that aid in reproduction. Plants that exhibit this behavior are known as carrion flowers. Stinkhorn mushrooms are examples of fungi with this characteristic. Sometimes carrion is used to describe an infected carcass, diseased and should not be touched.
An example of carrion being used to describe dead and rotting bodies in literature may be found in William Shakespeare's play Julius Caesar: Another example can be found in Daniel Defoe's Robinson Crusoe when the title character kills an unknown bird for food but finds "its flesh was carrion, fit for nothing". The thirty-count laws of Ulla include the prohibition of humans consuming carrion; this count is in addition to the standard seven law count and has been published from the Judeo-Arabic writing of Shmuel ben Hophni Gaon after having been lost for centuries
The Jurassic period was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era known as the Age of Reptiles; the start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, the Tithonian event at the end; the Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations; the Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, Gondwana to the south; this created more coastlines and shifted the continental climate from dry to humid, many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life; the oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, he named it "Jura-Kalkstein" in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", borrowed into Latin as a place name, evolved into Juria and Jura. The Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations known as Lias and Malm in Europe; the separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are: During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Jurassic North Atlantic Ocean was narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared; as in the Triassic, there was no land over either pole, no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation; the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus common, along with calcitic ooids, calcitic cements, invertebrate faunas with dominantly calcitic skeletons; the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, South America, Japan and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well studied in Africa. Late Jurassic strata are poorly represented apart from the spectacular Tendaguru fauna in Tanzania; the Late Jurassic life of Tendaguru is similar to that found in western North America's Morrison Formation. During the Jurassic period, the primary vertebrates living in the sea were marine reptiles; the latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in rivers. In the invertebrate world, several new groups appeared, including rudists (a reef-formi
Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parents". Reproduction is a fundamental feature of all known life. There are two forms of reproduction: sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms; the cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically identical copy of itself; the evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes. Sexual reproduction requires the sexual interaction of two specialized organisms, called gametes, which contain half the number of chromosomes of normal cells and are created by meiosis, with a male fertilizing a female of the same species to create a fertilized zygote; this produces offspring organisms whose genetic characteristics are derived from those of the two parental organisms.
Asexual reproduction is a process by which organisms create genetically similar or identical copies of themselves without the contribution of genetic material from another organism. Bacteria divide asexually via binary fission; these organisms do not possess different sexes, they are capable of "splitting" themselves into two or more copies of themselves. Most plants have the ability to reproduce asexually and the ant species Mycocepurus smithii is thought to reproduce by asexual means; some species that are capable of reproducing asexually, like hydra and jellyfish, may reproduce sexually. For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can reproduce sexually. Bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include parthenogenesis and spore formation that involves only mitosis. Parthenogenesis is the development of embryo or seed without fertilization by a male. Parthenogenesis occurs in some species, including lower plants and vertebrates.
It is sometimes used to describe reproduction modes in hermaphroditic species which can self-fertilize. Sexual reproduction is a biological process that creates a new organism by combining the genetic material of two organisms in a process that starts with meiosis, a specialized type of cell division; each of two parent organisms contributes half of the offspring's genetic makeup by creating haploid gametes. Most organisms form two different types of gametes. In these anisogamous species, the two sexes are referred to as female. In isogamous species, the gametes are similar or identical in form, but may have separable properties and may be given other different names. For example, in the green alga, Chlamydomonas reinhardtii, there are so-called "plus" and "minus" gametes. A few types of organisms, such as many fungi and the ciliate Paramecium aurelia, have more than two "sexes", called syngens. Most animals and plants reproduce sexually. Sexually reproducing organisms have different sets of genes for every trait.
Offspring inherit one allele for each trait from each parent. Thus, offspring have a combination of the parents' genes, it is believed that "the masking of deleterious alleles favors the evolution of a dominant diploid phase in organisms that alternate between haploid and diploid phases" where recombination occurs freely. Bryophytes reproduce sexually, but the larger and commonly-seen organisms are haploid and produce gametes; the gametes fuse to form a zygote which develops into a sporangium, which in turn produces haploid spores. The diploid stage is small and short-lived compared to the haploid stage, i.e. haploid dominance. The advantage of diploidy, only exists in the diploid life generation. Bryophytes retain sexual reproduction despite the fact that the haploid stage does not benefit from heterosis; this may be an indication that the sexual reproduction has advantages other than heterosis, such as genetic recombination between members of the species, allowing the expression of a wider range of traits and thus making the population more able to survive environmental variation.
Allogamy is the fertilization of the combination of gametes from two parents the ovum from one individual with the spermatozoa of another. Self-fertilization known as autogamy, occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual, e.g. many vascular plants, some foraminiferans, some ciliates. The term "autogamy" is sometimes substituted for autogamous pollination and describes self-pollination within the same flower, distinguished from geitonogamous pollination, transfer of pollen to a different flower on the same flowering plant, or within a single monoecious Gymnosperm plant. Mitosis and meiosis are types of cell division. Mitosis occurs in somatic cells. Mitosis The resultant number of cells in mitosis is t