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Chordata
And see textA chordate is an animal belonging to the phylum Chordata; chordates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail, for at least some period of their life cycle. Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates with metameric segmentation and a circulatory system. In the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development. Taxonomically, the phylum includes the following subphyla: the Vertebrata, which includes fish, amphibians, reptiles, birds, and mammals; the Tunicata, which includes salps and sea squirts; and the Cephalochordata, which include the lancelets. There are also additional extinct taxa such as the Vetulicolia
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Cordate
The following is a defined list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular or irregular, may be smooth or bearing hair, bristles or spines. For more terms describing other aspects of leaves besides their overall morphology see the leaf article.Chart illustrating leaf morphology termsContents1 Leaf
Leaf
structure 2 Leaf
Leaf
and leaflet shapes 3 Edge 4 Leaf
Leaf
folding 5 Latin descriptions 6 See also 7 References 8 Bibliography 9 External links Leaf
Leaf
structure[edit]A ternate compound leaf with a petiole but no rachis (or rachillae)Leaves of most plants include a flat structure called the blade or lamina, but not all leaves are flat, some are cylindrical
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Paleogene
The Paleogene (/ˈpæliədʒiːn, ˈpeɪliə-/; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous
Cretaceous
Period 66 million years ago (Mya) to the beginning of the Neogene
Neogene
Period 23.03 Mya
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Circulatory System
The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis. The circulatory system includes the lymphatic system, which circulates lymph.[1] The passage of lymph for example takes much longer than that of blood.[2] Blood
Blood
is a fluid consisting of plasma, red blood cells, white blood cells, and platelets that is circulated by the heart through the vertebrate vascular system, carrying oxygen and nutrients to and waste materials away from all body tissues
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Bilateral Symmetry
Symmetry
Symmetry
in biology is the balanced distribution of duplicate body parts or shapes within the body of an organism. In nature and biology, symmetry is always approximate. For example, plant leaves – while considered symmetrical – rarely match up exactly when folded in half. Symmetry
Symmetry
creates a class of patterns in nature, where the near-repetition of the pattern element is by reflection or rotation. The body plans of most multicellular organisms exhibit some form of symmetry, whether radial, bilateral, or spherical
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Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds. While tails are primarily a feature of vertebrates, some invertebrates including scorpions and springtails, as well as snails and slugs, have tail-like appendages that are sometimes referred to as tails. Tailed objects are sometimes referred to as "caudate" and the part of the body associated with or proximal to the tail are given the adjective "caudal".Contents1 Function 2 Human tails 3 Gallery 4 See also 5 References 6 External linksFunction[edit] Vulpes lagopus
Vulpes lagopus
(Arctic fox) sleeping with its tail wrapped as a blanket. Animal
Animal
tails are used in a variety of ways
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Endostyle
The endostyle is an organ which assists lower-chordates (urochordates and cephalochordates, as well as the larvae of lampreys) in filter-feeding. This pharyngeal organ secretes mucus which utilizes cilia to coat itself.[1] The mucus produced by the endostyle adheres to food particles that are in the water and this mixture is then passed through the pharynx of the organism and into the esophagus through the sweeping movement of the cilia.[1] The endostyle in larval lampreys (ammocoetes) metamorphoses into the thyroid gland in adults, and is regarded as being homologous to the thyroid gland in vertebrates due to its iodine-concentrating activity.[2] Since the endostyle is found in the three branches of chordates, it is presumed to have arisen in the common ancestor of these taxa, along with a shift to internal feeding for extracting suspended food from the water.[3] References[edit]^ a b L., Jordan, E. (1967). Chordate
Chordate
Zoology. Delhi: S. Chanda & Co
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Pharyngeal Slit
Pharyngeal slits are filter-feeding organs found in Invertebrate chordates (lancelets and tunicates) and hemichordates living in aquatic environments. Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth. With this position, they allow for the movement of water in the mouth and out the pharyngeal slits. It's postulated that this is how pharyngeal slits first assisted in filter-feeding, and later with the addition of gills along their walls, aided in respiration of aquatic chordates.[1] These repeated segments are controlled by similar developmental mechanisms. Some hemichordate species can have as many as 200 gill slits.[2] Pharyngeal slits resembling gill slits are transiently present during the embryonic stages of tetrapod development
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Dorsal Nerve Cord
The dorsal nerve cord is a unique feature to chordates, and it is mainly found in the Vertebrata
Vertebrata
chordate subphylum. The dorsal nerve cord is only one embryonic feature unique to all chordates, among the other four chordate features-- a notochord, a post-anal tail, an endostyle, and pharyngeal slits. The dorsal hollow nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. This is important, as it distinguishes chordates from other animal phyla, such as Annelids
Annelids
and Arthropods, which have solid, ventral tubes. The process by which this is performed is called invagination. The cells essentially convolute into the body cavity, arranging themselves on the dorsal plane above the notochord, as mentioned above. The evolutionary explanation to this adaptation from a solid cord to hollow tube is unknown
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Notochord
In anatomy, the notochord is a flexible rod made out of a material similar to cartilage. If a species has a notochord at any stage during its life cycle, it is, by definition, a chordate. The notochord lies along the anteroposterior ("head to tail") axis, is usually closer to the dorsal than the ventral surface of the animal, and is composed of cells derived from the mesoderm. The notochord has been observed to have many functions including developmental functions. The most commonly cited functions are as a site of muscle attachment, vertebral precursor, and as a midline tissue that provides signals to the surrounding tissue during development.[1] Notochords are thought to be advantageous (both in an evolutionary and developmental context) because they provide(d) rigid structure for muscle attachment, but were still flexible
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Terreneuvian
Coordinates: 47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310Delegates from the Ichnia 2012 conference inspect the Global Boundary Stratotype Section and Point (GSSP) for the Ediacaran-Cambrian boundary at Fortune Head
Fortune Head
Ecological Reserve, Newfoundland, Canada. The boundary is defined on the appearance of the complex, vertical trace fossil Treptichnus (formerly Phycodes) pedum.The Terreneuvian
Terreneuvian
is the lowermost and oldest series of the Cambrian geological system.[1] Its base is defined by the first appearance datum of the trace fossil Treptichnus pedum
Treptichnus pedum
around 541 million years ago
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Taxonomy (biology)
Taxonomy (from Ancient Greek τάξις (taxis), meaning 'arrangement', and -νομία (-nomia), meaning 'method') is the science of defining and naming groups of biological organisms on the basis of shared characteristics. Organisms are grouped together into taxa (singular: taxon) and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a super-group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum (division is sometimes used in botany in place of phylum), class, order, family, genus and species
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Spinal Cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system (CNS). In humans, the spinal cord begins at the occipital bone where it passes through the foramen magnum, and meets and enters the spinal canal at the beginning of the cervical vertebrae. The spinal cord extends down to between the first and second lumbar vertebrae where it ends. The enclosing bony vertebral column protects the relatively shorter spinal cord. It is around 45 cm (18 in) in men and around 43 cm (17 in) long in women
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Neogene
The Neogene
Neogene
( /ˈniːəˌdʒiːn/)[6][7] (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago (Mya) to the beginning of the present Quaternary
Quaternary
Period 2.58 Mya. The Neogene
Neogene
is sub-divided into two epochs, the earlier Miocene
Miocene
and the later Pliocene. Some geologists assert that the Neogene
Neogene
cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into roughly modern forms, while other groups of life remained relatively unchanged. Early hominids, the ancestors of humans, appeared in Africa near the end of the period
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Ernst Haeckel
Ernst Heinrich Philipp August Haeckel (German: [ˈhɛkəl]; 16 February 1834 – 9 August 1919[1]) was a German biologist, naturalist, philosopher, physician, professor, marine biologist, and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including anthropogeny, ecology, phylum, phylogeny, stem cell, and Protista. Haeckel promoted and popularised Charles Darwin's work in Germany and developed the influential but no longer widely held recapitulation theory ("ontogeny recapitulates phylogeny") claiming that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development, or phylogeny. The published artwork of Haeckel includes over 100 detailed, multi-colour illustrations of animals and sea creatures (see: Kunstformen der Natur, "Art Forms of Nature")
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Cretaceous
The Cretaceous
Cretaceous
( /krɪˈteɪʃəs/, kri-TAY-shəs) is a geologic period and system that spans 79 million years from the end of the Jurassic
Jurassic
Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic
Mesozoic
Era. The Cretaceous
Cretaceous
Period is usually abbreviated K, for its German translation Kreide (chalk). The Cretaceous
Cretaceous
was a period with a relatively 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, ammonites and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared
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