Bats are mammals of the order Chiroptera whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, Bats do not flap their entire forelimbs, as birds do, but instead flap their spread-out digits, which are very long and covered with a thin membrane or patagium. About 70% of bat species are insectivores, most of the rest are frugivores, or fruit eaters. A few species, such as the bat, feed from animals other than insects, with the vampire bats being hematophagous. Bats are present throughout most of the world, with the exception of cold regions. They perform the vital roles of pollinating flowers and dispersing fruit seeds. Bats are economically important, as they consume insect pests, reducing the need for pesticides, the smallest bat is the Kittis hog-nosed bat, measuring 29–34 mm in length,15 cm across the wings and 2–2.6 g in mass. It is arguably the smallest extant species of mammal, with the Etruscan shrew being the other contender.
The largest species of bat are a few species of Pteropus, the Mexican free-tailed bat is the fastest flying animal in horizontal flight. An older English name for bats is flittermouse, which matches their name in other Germanic languages, middle English had bakke, most likely cognate with Old Swedish natbakka, which may have undergone a shift from -k- to -t- influenced by Latin blatta, nocturnal insect. They were formerly grouped in the superorder Archonta, along with the treeshrews, genetic studies have now placed bats in the superorder Laurasiatheria, along with carnivorans, odd-toed ungulates, even-toed ungulates, and cetaceans. A recent study by Zhang et al. places Chiroptera as a taxon to the clade Perissodactyla. The phylogenetic relationships of the different groups of bats have been the subject of much debate and this hypothesis recognized differences between microbats and megabats and acknowledged that flight has only evolved once in mammals. Most molecular biological evidence supports the view that bats form a single or monophyletic group, in the 1980s, a hypothesis based on morphological evidence was offered that stated the Megachiroptera evolved flight separately from the Microchiroptera.
The so-called flying primate hypothesis proposes that, when adaptations to flight are removed, one example is that the brains of megabats show a number of advanced characteristics that link them to primates. Although recent genetic studies support the monophyly of bats, debate continues as to the meaning of available genetic. Genetic evidence indicates that megabats originated during the early Eocene and should be placed within the four lines of microbats. Consequently, two new suborders based on molecular data have been proposed and these two new suborders are strongly supported by statistical tests
Mitochondrial DNA is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate. Mitochondrial DNA is only a portion of the DNA in a eukaryotic cell, most of the DNA can be found in the cell nucleus and, in plants and algae. In humans, the 16,569 base pairs of mitochondrial DNA encode for only 37 genes, human mitochondrial DNA was the first significant part of the human genome to be sequenced. In most species, including humans, mtDNA is inherited solely from the mother, since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It permits an examination of the relatedness of populations, and so has become important in anthropology and this theory is called the endosymbiotic theory. Each mitochondrion is estimated to contain 2–10 mtDNA copies, the reasons why mitochondria have retained some genes are debated. Recent analysis of a range of mtDNA genomes suggests that both these features may dictate mitochondrial gene retention.
In most multicellular organisms, mtDNA is inherited from the mother, mechanisms for this include simple dilution, degradation of sperm mtDNA in the male genital tract, in the fertilized egg, and, at least in a few organisms, failure of sperm mtDNA to enter the egg. Whatever the mechanism, this single parent pattern of inheritance is found in most animals, most plants. In sexual reproduction, mitochondria are inherited exclusively from the mother. Also, most mitochondria are present at the base of the sperms tail, in 1999 it was reported that paternal sperm mitochondria are marked with ubiquitin to select them for destruction inside the embryo. Some in vitro techniques, particularly injecting a sperm into an oocyte. The fact that mitochondrial DNA is maternally inherited enables researchers to trace maternal lineage far back in time. This is usually accomplished on human mitochondrial DNA by sequencing the hypervariable control regions, hVR1, for example, consists of about 440 base pairs. These 440 base pairs are compared to the regions of other individuals to determine maternal lineage.
Most often, the comparison is made to the revised Cambridge Reference Sequence, vilà et al. have published studies tracing the matrilineal descent of domestic dogs to wolves. The concept of the Mitochondrial Eve is based on the type of analysis. MtDNA is highly conserved, and its relatively slow mutation rates make it useful for studying the evolutionary relationships—phylogeny—of organisms, biologists can determine and compare mtDNA sequences among different species and use the comparisons to build an evolutionary tree for the species examined
In anatomy, the atlas is the most superior cervical vertebra of the spine. It is named for the Atlas of Greek mythology, because it supports the globe of the head, the atlas is the topmost vertebra and with the axis forms the joint connecting the skull and spine. The atlas and axis are specialized to allow a range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head, the atlanto-occipital joint allows the head to nod up and down on the vertebral column. The dens acts as a pivot that allows the atlas and attached head to rotate on the axis, the atlass chief peculiarity is that it has no body. It is ring-like and consists of an anterior and a posterior arch, the atlas and axis are important neurologically because the brain stem extends down to the axis. The diminutive size of this process prevents any interference with the movements between the atlas and the skull and this anatomical variant is known as an arcuate foramen. The lower border gives attachment to the posterior atlantoaxial ligament, which connects it with the axis, the lateral masses are the most bulky and solid parts of the atlas, in order to support the weight of the head.
Each carries two articular facets, a superior and an inferior, not infrequently they are partially subdivided by indentations which encroach upon their margins. The inferior articular facets are circular in form, flattened or slightly convex and directed downward and medially, articulating with the axis, and permitting the rotatory movements of the head. The transverse processes are large, they project laterally and downward from the lateral masses and they are long, and their anterior and posterior tubercles are fused into one mass, the foramen transversarium is directed from below and backward. The atlas is usually ossified from three centers, between the third and fourth years they unite either directly or through the medium of a separate center developed in the cartilage. At birth, the arch consists of cartilage, in this a separate center appears about the end of the first year after birth. The lines of union extend across the anterior portions of the superior articular facets, a break in the first vertebra is referred to as a Jefferson fracture.
Occipital condyle This article incorporates text in the domain from the 20th edition of Grays Anatomy Netter. Atlas of Human Anatomy, High Cervical Spine, C1–C2
The Y chromosome is one of two sex chromosomes in mammals, including humans, and many other animals. The other is the X chromosome, Y is the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers testis development, the DNA in the human Y chromosome is composed of about 59 million base pairs. The Y chromosome is passed only from father to son, with a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome. To date, over 200 Y-linked genes have been identified, all Y-linked genes are expressed and hemizygous except in the cases of aneuploidy such as XYY syndrome or XXYY syndrome. The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm Tenebrio molitor, edmund Beecher Wilson independently discovered the same mechanisms the same year.
Stevens proposed that chromosomes always existed in pairs and that the Y chromosome was the pair of the X chromosome discovered in 1890 by Hermann Henking, Stevens named the chromosome Y simply to follow on from Henkings X alphabetically. The idea that the Y chromosome was named after its similarity in appearance to the letter Y is mistaken, all chromosomes normally appear as an amorphous blob under the microscope and only take on a well-defined shape during mitosis. This shape is vaguely X-shaped for all chromosomes and it is entirely coincidental that the Y chromosome, during mitosis, has two very short branches which can look merged under the microscope and appear as the descender of a Y-shape. Most mammals have one pair of sex chromosomes in each cell. Males have one Y chromosome and one X chromosome, while females have two X chromosomes, in mammals, the Y chromosome contains a gene, SRY, which triggers embryonic development as a male. The Y chromosomes of humans and other mammals contain other genes needed for normal sperm production, for example, the platypus relies on an XY sex-determination system based on five pairs of chromosomes.
Among humans, some men have two Xs and a Y, or one X and two Ys, and some women have three Xs or a single X instead of a double X, there are other exceptions in which SRY is damaged, or copied to the X. For related phenomena, see Androgen insensitivity syndrome and Intersex, many ectothermic vertebrates have no sex chromosomes. If they have different sexes, sex is determined environmentally rather than genetically, for some of them, especially reptiles, sex depends on the incubation temperature, others are hermaphroditic. The chromosome with this became the Y chromosome, while the other member of the pair became the X chromosome. Over time, genes that were beneficial for males and harmful to females either developed on the Y chromosome or were acquired through the process of translocation, until recently, the X and Y chromosomes were thought to have diverged around 300 million years ago. The older estimate was based on reports that the platypus X chromosomes contained these sequences
Ontogeny is the developmental history of an organism within its own lifetime, as distinct from phylogeny, which refers to the evolutionary history of a species. In practice, writers on evolution often speak of species as developing traits or characteristics, while developmental processes can influence subsequent evolutionary processes, individual organisms develop, while species evolve. Ontogeny and developmental biology are closely related studies and the terms are used interchangeably. Recently, the term ontogeny has been used in biology to describe the development of various cell types within an organism. Ontogeny is a field of study in many disciplines, including developmental biology, developmental psychology, developmental cognitive neuroscience. Ontogeny is a used in anthropology as the process through which each of us embodies the history of our own making. A seminal paper named ontogeny as one of the four primary questions of biology, tinbergen emphasized that the change of behavioral machinery during development was distinct from the change in behavior during development.
Tinbergen was concerned that the elimination of factors is difficult to establish. Most organisms undergo changes in shape as they grow and mature. Even reptiles, in which the offspring are often viewed as miniature adults, comparing ourselves to others is something humans do all the time. In doing so we are acknowledging not so much our sameness to others or our difference, rather, in respect of all other humans, we find similarities in the ways we are different from one another and differences in the ways we are the same. That we are able to do this is a function of the historical process that is human ontogeny. Media related to Morphogenesis at Wikimedia Commons The dictionary definition of ontogeny at Wiktionary
Fossils are the preserved remains or traces of animals and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record. The study of fossils across geological time, how they were formed, such a preserved specimen is called a fossil if it is older than some minimum age, most often the arbitrary date of 10,000 years. The observation that fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of dating techniques in the early 20th century allowed geologists to determine the numerical or absolute age of the various strata. Like extant organisms, fossils vary in size from microscopic, even single bacterial cells one micrometer in diameter, to gigantic, such as dinosaurs, Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces.
These types of fossil are called trace fossils, as opposed to body fossils, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals, these are known as chemofossils or biosignatures. The process of fossilization varies according to type and external conditions. Permineralization is a process of fossilization that occurs when an organism is buried, the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater, occupying the empty spaces and this process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils, for permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decay process. The degree to which the remains are decayed when covered determines the details of the fossil, some fossils consist only of skeletal remains or teeth, other fossils contain traces of skin, feathers or even soft tissues.
This is a form of diagenesis, in some cases the original remains of the organism completely dissolve or are otherwise destroyed. The remaining organism-shaped hole in the rock is called an external mold, if this hole is filled with other minerals, it is a cast. An endocast or internal mold is formed when sediments or minerals fill the cavity of an organism. This is a form of cast and mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, if this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization, replacement occurs when the shell, bone or other tissue is replaced with another mineral
The red deer is one of the largest deer species. The red deer inhabits most of Europe, the Caucasus Mountains region, Asia Minor, parts of western Asia and it inhabits the Atlas Mountains region between Morocco and Tunisia in northwestern Africa, being the only species of deer to inhabit Africa. Red deer have been introduced to areas, including Australia, New Zealand, United States, Peru, Chile. In many parts of the world, the meat from red deer is used as a food source, Red deer are ruminants, characterized by a four-chambered stomach. Genetic evidence indicates the red deer as traditionally defined is a group, rather than a single species. It is probable that the ancestor of all red deer, including wapiti, originated in central Asia, although at one time red deer were rare in parts of Europe, they were never close to extinction. The red deer is the fourth-largest deer species behind moose, elk and it is a ruminant, eating its food in two stages and having an even number of toes on each hoof, like camels and cattle.
European red deer have a long tail compared to their Asian. The deer of Central and Western Europe vary greatly in size, large red deer stags, like the Caspian red deer or those of the Carpathian Mountains, may rival the wapiti in size. Female red deer are smaller than their male counterparts. The male red deer is typically 175 to 250 cm long and weighs 160 to 240 kg, the tail adds another 12 to 19 cm and shoulder height is about 95 to 130 cm. In Scotland, stags average 201 cm in length and 122 cm high at the shoulder. Size varies in different subspecies with the largest, the huge but small-antlered deer of the Carpathian Mountains, weighing up to 500 kg. At the other end of the scale, the Corsican red deer weighs about 80 to 100 kg, European red deer tend to be reddish-brown in their summer coats. The males of many subspecies grow a short neck mane during the autumn, the male deer of the British Isles and Norway tend to have the thickest and most noticeable manes. Male Caspian red deer and Spanish red deer do not carry neck manes, male deer of all subspecies, tend to have stronger and thicker neck muscles than female deer, which may give them an appearance of having neck manes.
Red deer hinds do not have neck manes, the European red deer is adapted to a woodland environment. Only the stags have antlers, which growing in the spring and are shed each year
Where the connecting medium is hyaline cartilage, a cartilaginous joint is termed a synchondrosis. An example of a joint is the first sternocostal joint. In this example, the rib articulates with the manubrium via the costal cartilage, this is a temporary form of joint called epiphyseal growth plate, where the cartilage is converted into bone before adult life. Types of joints This article incorporates text in the domain from the 20th edition of Grays Anatomy
Forkhead box protein P2 is a protein that, in humans, is encoded by the FOXP2 gene, known as CAGH44, SPCH1 or TNRC10, and is required for proper development of speech and language. Initially identified as the factor of speech disorder in KE family, its gene is the first gene discovered associated with speech. The gene is located on chromosome 7, and is expressed in fetal and adult brain, lung, FOXP2 orthologs have been identified in other mammals for which complete genome data are available. The FOXP2 protein contains a forkhead-box DNA-binding domain, making it a member of the FOX group of transcription factors, in addition to this characteristic forkhead-box domain, the protein contains a polyglutamine tract, a zinc finger and a leucine zipper. The gene is active in females than in males, to which could be attributed better language learning in females. In humans, mutations of FOXP2 cause a severe speech and language disorder, outside the brain FOXP2 has been implicated in development of other tissues such as the lung and gut. FOXP2 is popularly dubbed the gene, but this is only partly correct since there are other genes involved in language development.
It directly regulates a number of genes, including CNTNAP2, CTBP1. Two amino acid substitutions distinguish the human FOXP2 protein from that found in chimpanzees, evidence from genetically manipulated mice and human neuronal cell models suggests that these changes affect the neural functions of FOXP2. Their case was studied at the Institute of Child Health of University London College and she hypothesized that the basis was not of learning or cognitive disability, but due to genetic factors affecting mainly grammatical ability. In 1995, the University of Oxford and the Institute of Child Health researchers found that the disorder was purely genetic. This is one of the few examples of Mendelian inheritance for a disorder affecting speech and language skills. In 1998, Oxford University geneticists Simon Fisher, Anthony Monaco, Cecilia S. L. Lai, the chromosomal region contained 70 genes. The locus was given the official name SPCH1 by the Human Genome Nomenclature committee and sequencing of the chromosomal region was performed with the aid of bacterial artificial chromosome clones.
Around this time, the researchers identified an individual who was unrelated to the KE family, in this case the child, known as CS, carried a chromosomal rearrangement in which part of chromosome 7 had become exchanged with part of chromosome 5. The site of breakage of chromosome 7 was located within the SPCH1 region, in 2001, the team identified in CS that the mutation is in the middle of a protein-coding gene. Using a combination of bioinformatics and RNA analyses, they discovered that the codes for a novel protein belonging to the forkhead-box group of transcription factors. As such, it was assigned with the name of FOXP2