which clade is most primitive
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- Lampreys and hagfishes are the only jawless vertebrates to survive today. They both have a round mouth and for this reason are often referred to as cyclostomes. They are the most primitive of the vertebrates. By primitive, a biologist means that they are the least changed from the first vertebrates.1  They have no paired pectoral (shoulder) or pelvic (hip) fins. 2  Their notochord persists for life, never being completely replaced by a backbone even in the lampreys.3  They have no scales.y primitive, a biologist means that they are the least changed from the first vertebrates. 1  They have no paired pectoral (shoulder) or pelvic (hip) fins. 2  Their notochord persists for life, never being completely replaced by a backbone even in the lampreys. 3  They have no scales.
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- C. Pharyngeal pouches. D. Endostyle-elongated groove in the pharynx floor of protochordates that may develop as the thyroid gland in chordates. These four characteristics may be found in some of the ancestors of chordates and are commonly placed in an informal grouping called Protochordates.These serve as living representations of the missing fossils in vertebrate evolution.n contrast to protochordates (hemichordates, urochordates, and cephalochordates), vertebrates are actively-feeding, predatory organisms that move by lateral undulation of an elongate body. Hemichordates and most urochordates are also filter-feeders, moving water through their gill slits, but are sessile as adults.
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Dinosaursâ Living Descendants The fossils finally have confirmed, to all but a few skeptics, that birds descended from dinosaurs and are the living representatives of a dinosaur lineage called the Maniraptorans. Most dinosaurs were not part of the lineage that gave rise to birds; they occupied other branches of the dinosaur family tree. Sinosauropteryx, in fact, was what paleontologists call a non-avian dinosaur, even though it had feathers.
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- Gnathostomes-vertebrates with jaws derived from the mandibular arch, which may have (in primitive vertebrates) supported gills. Includes Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia. Amniotes-vertebrates that possess an amnion. Includes Reptilia, Aves, Mammalia. Tracing vertebrate evolution through the fossil record. Keep in mind that the evolutionary relationships among the different taxa that we are discussing have been determined from the fossil record. Vertebrates, among all species of animals in the world, have the best fossil record.
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Examples of Invertebrate Chordates In this way, invertebrate chordates are considered some of the most basal, or primitive, chordates. While there is a fossil record for these ancient relatives of ours, there are, amazingly, also examples of invertebrate chordates still alive today.
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Looking for the most âprimitiveâ organism (s) on Earth today: the state of the art The search for the most primitive organisms still living today is a highly risky and uncertain task, In this paper, I have tried to convince the reader that even the wellestablished procaryotic dogma is not supported by real data.oese first suggested that the universal ancestor was a truly primitive organism, a progenote (Woese, 1981), i.e. an entity representing an evolutionary stage in between the very first living cells and modern procaryotes, fulfilling the dream of evolutionists. However, it turns out that molecular 172 Fig.
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Amphibian All modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura (the frogs and toads), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians).
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Archaeopteryx Archaeopteryx Conclusion. While it may be fair to conclude that Archaeopteryx was of intermediate structure (in the sense that it was a bird which shared a handful of features in common with reptiles), it cannot be regarded as transitional in terms of phylogeny.ecause it had fully developed feathers, including primaries and secondaries which were arranged on its wings in the same way as modern birds, Archaeopteryx is recognized and classified as a bird. Its skeleton, however, possessed a number of reptilian features.
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Clade Cladogram (family tree) of a large biological group, showing the last common ancestor of the composite tree, which is the vertical line 'trunk' at the bottom. A clade located within a clade is said to be nested within that clade. 2  In the diagram, the hominoid clade, the apes and humans, is nested within the primate clade. 3  Two clades are sisters if they have an immediate common ancestor. 4  In the diagram, lemurs and lorises are sister clades.
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- Introduction to Primitive Invertebrates. Today well examine several phyla that represent alternate pathways in early animal evolution. The sponges, in the Phylum Porifera, are so strange that they are placed in the Subkingdom Parazoa, which literally means “animals set aside”.All other animals belong to the Subkingdom Eumetazoa (“true” animals).oday well examine several phyla that represent alternate pathways in early animal evolution. The sponges, in the Phylum Porifera, are so strange that they are placed in the Subkingdom Parazoa, which literally means “animals set aside”. All other animals belong to the Subkingdom Eumetazoa (“true” animals).
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Clade A clade is by definition monophyletic, meaning it contains one ancestor (which can be an organism, a population, or a species) and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. A clade located within a clade is said to be nested within that clade. 2  In the diagram, the hominoid clade, the apes and humans, is nested within the primate clade. 3  Two clades are sisters if they have an immediate common ancestor.
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EXTINCTION OF THE DINOSAURS Primate-like Mammals. The first primate-like mammals, or proto-primates , evolved in the early Paleocene Epoch (65.5-55.8 million years ago) at the beginning of the Cenozoic Era. They were roughly similar to squirrels and tree shrews in size and appearance.
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- ... genome sequence of Trichoplax, one of nature's most primitive multicellular organisms, providing a new insight into the evolution ... with genes, introns and spacer sequences like the most primitive organisms. However, size is not all that matters.DNA ..... that they have discovered AEG within cyanobacteria, which are believed to be some of the most primitive organisms on Earth. AEG is a small molecule that when linked into chains forms a hypothetical backbone for peptide ...
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- Origins of the Chordates For Questions 1–8, write True if the statement is true. If the statement is false, change the underlined word to make the statement true. 1. Embryological evidence suggests that the most ancient chordates were related to the ancestors of echinoderms. 2. Pikaia was an early vertebrate fossil.
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What is a Clade? A clade is termed “monophyletic”, meaning it contains one ancestor which can be an organism, population or species and all its descendents. The term clade refers to the grouping of the ancestor and its living and/or deceased descendants together.n terms of biological systematic, a clade is a single “branch” on the “tree of life”. Charles Darwin, a English Naturalist, believed that the ascent of all species through time was expressible as a metaphor he termed the Tree of Life.
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Cladistics At the same time, cladistics rapidly became the dominant set of methods of phylogenetics in evolutionary biology, because computers made it possible to process large quantities of data about organisms and their characteristics.
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Brain Parts and Function Having evolved hundreds of millions of years ago, the Hindbrain or the Reptillian Brain is the oldest part of the human brain. As you might guess from it's name, it's a piece of brain anatomy that we share with reptiles and is the most primitive.Likewise it's in charge of our primal instincts and most basic functions.aving evolved hundreds of millions of years ago, the Hindbrain or the Reptillian Brain is the oldest part of the human brain. As you might guess from it's name, it's a piece of brain anatomy that we share with reptiles and is the most primitive.
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The molecular phylogeny of oysters based on a satellite DNA related to transposons The sequences of O. edulis, C. virginica and C. gasar are grouped in a sub-clade which constitute a clade with the sequences of C. ariakensis and subfamily 1 from C. angulata and C. gigas.
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Divergent and Convergent Pathways Cladistics: a phylogenetic system of classification used to infer and construct cladograms based on shared derived traits or synapomorphies. Synapomorphies: shared traits that evolved only by members of the group and that have been inherited from a single common ancestor in which the features first evolved. EX. Most vertebrates have paired appendages: fish have fins, while amphibians reptiles, birds and mammals are tetrapods.
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Major Phyla Of Animals Advocates of the panspermia hypothesis believe that tardigrades had an extraterrestrial origin, although DNA sequencing data indicate that the phylum Tardigrada (tardigrades) is a sister clade with the phylum Arthropoda (arthropods), and both phyla (Tardigrada + Arthropoda) form a sister clade with the phylum Onychophora (velvet worms).
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Looking for the most âprimitiveâ organism (s) on Earth today: the state of the art They comprise methane-producing anaerobic species (methano- P. Forterre : The most primitive organisms on Earth 169 yens), bacteria living in very high salt environments (halobacteria) and a huge number of diverse thermophilic species, aerobic and/or anaerobic, acidophilic or neutrophilic (sulfothermophiles).
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Whale The whales are part of the largely terrestrial mammalian clade Laurasiatheria. Whales do not form a clade or order; the infraorder Cetacea includes dolphins and porpoises, which are not considered whales.
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EXTINCTION OF THE DINOSAURS Primate-like Mammals. The first primate-like mammals, or proto-primates, evolved in the early Paleocene Epoch (65.5-55.8 million years ago) at the beginning of the Cenozoic Era. They were roughly similar to squirrels and tree shrews in size and appearance.
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Primate Based on fossil evidence, the earliest known true primates, represented by the genus Teilhardina, date to 55.8 mya. An early close primate relative known from abundant remains is the Late Paleocene Plesiadapis, c. 55–58 million years old.
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- The most ancient part of our brains -- the brain stem and hindbrain-- are still shared with reptiles and thus, we call this primeval foundation of our central nervous system the reptilian brain.
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Kingdom Monera Monera are considered as the most primitive group of organisms. They include various types of bacteria and blue-green algae. Monerans are most abundant of all organisms, due to their versa ti lity of their habitat. It is estimated that a single drop of water contai ns 50 billion bacteria. They are primitive organisms. 2  All organisms of the kingdom are prokaryotes. 3  They are present in both living and non-living environment. 4  They can survive in harsh and extreme climatic conditions like in hot springs, acidic soils etc.