chordates without a backbone
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The only living chordates that do not have backbones are the "protochordates", that is, the members of phyla Urochordata or Tunicata (sea squirts) and Cephalochordata (lancelets). These chordates have the primitive support structure, a dorsal notochord. \nAdult Tunicates lack notochords, except for the planktoninc and tiny Appendiculaceans.  Tunicate larvae (known as "tadpole larvae") _do_ have a notochord that supports their tails. \nThere are many genera and species of Tunicata; so if you do a Google Image search for either "Tunicata", "Urochordata" "sea squirt" or "salp" you'll get many good photographs.\nOn the other hand, the lancelets are much less diverse. Almost all are included in genus Branchiostoma, so if you look for "Branchiostoma" or "lancelet" you'll get what you're searching.
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She has demonstrated that she has no real 'backbone' with regard to intelligent social and political commentary.\n\nThe lack of a 'backbone' would, therefore, remove her from taxonomic placement within the Phylum 'Chordata' and would, logically, eliminate her from being labeled a Homo Sapien.
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Because there was no midway for hardly anything. Lizards never where halfway between lizard and bird, invertabrae never had a halfway formed spine, apes where never halfway man. Thats the only reason I can think ;)
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dolphin and pike (Osteichthyes) have bones; sea cucumber and flounder do not have true bones they are cartelagenous fish (Chondrichthyes)  the sea cucumber has no skeletal system.
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Hermatypic corals (the ones that form coral reefs) have symbiotic zooxanthellae (unicellular algae) within their tissues; the algae receive protection and housing from the polyps, and enable them to produce their calcareous exoskeleton.\nThere are sea anemones that attach to the dorsum of crabs, marine snails, etc. Thus the anemone "travels free" and the other animal is protected. \nMany species of small fishes and crustaceans shelter beneath the umbella of some jellyfish (read example at the link).
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They can't, actually, not without mixing it with another creature. Because all cells come from cells. You'd have to put the dino DNA into a modern reptile cell. And it does matter, because it is cellular machinery that brings about gene expression - and that can have a huge effect on gene expression. (epigenetic inheritance) So you would not really know what trait was dinosaur, and what was artifact from expressing the genes in a modern reptile cell. \n\nStill and all, it would be fun, I agree!
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These are the classes of Chordata : \n\nPhylum Chordata\n\n    * Subphylum Urochordata - Tunicates\n    * Subphylum Cephalochordata - Lancelets\n    * (unranked) Craniata (animals with skulls)\n          o Subphylum Vertebrata (Vertebrates - animals with backbones)\n                + Class Myxini or Hyperotreti (hagfish)\n                + Class Conodonta (Conodonts)\n                + Class Cephalaspidomorphi (Paleozoic jawless fish)\n                      # Hyperoartia (lampreys and kin)\n                + Class Pteraspidomorphi (other Paleozoic jawless fish)\n                + Infraphylum Gnathostomata (jawed vertebrates)\n                      # Class Placodermi (Paleozoic armoured forms)\n                      # Class Chondrichthyes (cartilaginous fish)\n                      # (unranked) Teleostomi (advanced fishes and their descendents)\n                            * Class Acanthodii (Paleozoic "spiny sharks")\n                            * Class Actinopterygii (ray-finned fish - Osteichthyes in part)\n                      # Class Sarcopterygii (lobe-finned fish - Osteichthyes in part))\n                            * Superclass Tetrapoda (four-legged vertebrates)\n                                  o Class Amphibia (amphibians)\n                                  o Series Amniota (amniotic egg)\n                                        + Class Synapsida (mammal-like reptiles)\n                                              # Class Mammalia (mammals)\n                                        + Class Sauropsida - (reptiles)\n                                              # Subclass Anapsida\n                                                    * Order Testudines (turtles)\n                                                    * Subclass Diapsida (most modern reptiles)\n                                                          o Superorder Lepidosauria (lizards, snakes, tuatara)\n                                                          o Division Archosauria ("ruling reptiles")\n                                                                + Order Crocodilia (crocodiles, alligators, caimans, gharials)\n                                                                + Superorder Dinosauria\n                                                                      # Class Aves (birds)
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They are arachnids, not crustaceans. Easy to find on the Indian Ocean shores. Dead animals eaters. Breath using gills, two sexed animals, egg layers, free swimmers. Outstanding feature: their blood is used as a reactive in a positive detection of human encephalitis.\n\nmore info: Barnes book of invertebrates
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It has long been held that the parathyroid glands and parathyroid hormone evolved with the emergence of the tetrapods, reflecting a need for new controls on calcium homeostasis in terrestrial, rather than aquatic, environments.\n\nNice to see you've corrected the spelling mistake in your 'nickname', after we all pointed it out, of course...there's a good girl!\n\n;)
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The tail of lizards is an important element for locomotion and balance. These animals move by mean of undulations of their entire body axis (vertebral column), and the motions of the tail counteract those of the trunk.\nIn addition, most lizards are capable of autotomy, that is, they can shed their tail at need, usually when threatened by a predator or in other highly stressful conditions, and then grow a new tail. \nThis is achieved by means of special intravertebral fracture planes, that is, each of the autotomic vertebrae has a weak transversal plane through which it can break into two pieces. In addition, the tail muscles of the autotomic region are arranged in small "brick-like" packages that can become separated without much tissue damage; the blood vessels in the area also have the ability of closing and clotting rapidly so as to avoid excess blood loss.\nUnder stressful conditions, the animal will experience reflex contraction of those specialized muscles and a fragment of the tail will become separated from the rest of the body. This fragment continues to thrash and move for some minutes after autotomy, thus attracting the would-be predator while the lizard escapes to safety.\nAfterwards, a new tail will grow (this can take several months, according to the metabolic rate and general conditions of the individual); but this new tail does not have real vertebrae, only a rod-like support tissue. It usually has a blunt tip and different color/texture from the original tail. \nThere are _no_ autotomic vertebrae inside this new stump; therefore, the next autotomy will have to occur in vertebrae that are closer to the trunk. The number of these special vertebrae is limited, so the amount of autotomies is also limited. \nAutotomy is obviously advantageous as a means of escape. However, tail loss also implies a disadvantage, basically because: 1) as other users have answered, many lizards store fat supplies in the tail (although normally the basal part of the tail is not autotomic); 2)"growing back" a new tail requires more energetic resources that might have been used for other purposes; 3)until the new tail grows, locomotion may be somewhat impaired.\nAnd I'm leaving out other (e.g. social communication) uses of the tail.\nInterestingly, the tail won't grow back if the severance does not occur at the special fracture planes.
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courtesy of Encarta Encyclopedia Online!\nThe phylum of Cnidarians, or Coelenterates, is a phylum within Kingdom Animalia and consists of hydras, jellyfish, sea anemones, and corals. This phylum consists of over 9000 species. All cnidarians are radially symmetrical, meaning that they have a central axis and are symmetrical all around it. Their level of complexity is right above that of sponges, among the Metazoa, or many cells animals. In all cnidarians, the mouth leads directly into the gastrovascular cavity, a digestive cavity. This cavity is filled with fluid, which services internal cells, provides body support, and helps maintain structure. There is no anus, and so excess food and waste products must exit through the mouth. As a result, the digestive system of cnidarians is considered incomplete. Another characteristic of cnidarians is that they all have two layers of living tissue. The first layer of living tissue is known as the dermis, and the second layer is know as the gastordermis. The dermis is the outer layer, and the gastordermis is the inner layer which forms the body cavity. A gelatinous layer called mesoglea separates these two layers. Also, in all cnidarians, nearly all functions are performed by individual tissues, not organs, despite the fact that a very small number of them do contain organs. Another characteristic of cnidarians is that they all have two layers of living tissue. The first layer of living tissue is known as the dermis, and the second layer is know as the gastordermis. The dermis is the outer layer, and the gastordermis is the inner layer which forms the body cavity. A gelatinous layer called mesoglea separates these two layers. Also, in all cnidarians, nearly all functions are performed by individual tissues, not organs, despite the fact that a very small number of them do contain organs.\n\nPhylum Cnidaria includes the following classes:\n\n-Class Schphozoa (The jellyfish, or jellies)\n-Class Hydrozoa (Diverse polyps, including hydras)\n-Class Cubozoa (A minor tropical class with cuboidal swimming cups)\n-Class Anthozoa (Sea anemones, corals)
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A cell undergoing mitosis without cytokinesis would result in a mass of cytoplasm with many nuclei. For an example take a look at a slime mold like physarum polycephalum: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endoreplication.html
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Wood-boring bivalves of the family Teredinidae (commonly called shipworms) are known to harbor dense populations of gram-negative bacteria within specialized cells (bacteriocytes) in their gills. These symbionts are thought to provide enzymes, e.g., cellulase and dinitrogenase, which assist the host in utilizing wood as a primary food source. A cellulolytic, dinitrogen-fixing bacterium, Teredinibacter turnerae, has been isolated from the gill tissues of numerous teredinid bivalves and has been proposed to constitute the sole or predominant symbiont of this bivalve family. Here we demonstrate that one teredinid species, Lyrodus pedicellatus, contains at least four distinct bacterial 16S rRNA types within its gill bacteriocytes, one of which is identical to that of T. turnerae. Phylogenetic analyses indicate that the three newly detected ribotypes are derived from gamma proteobacteria that are related to but distinct (>6.5% sequence divergence) from T. turnerae. In situ hybridizations with 16S rRNA-directed probes demonstrated that the pattern of occurrence of symbiont ribotypes within bacteriocytes was predictable and specific, with some bacteriocytes containing two symbiont ribotypes. However, only two of the six possible pairwise combinations of the four ribotypes were observed to cooccur within the same host cells. The results presented here are consistent with the existence of a complex multiple symbiosis in this shipworm species.
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A. plant cells do not have centrioles.
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Actually, it makes perfect sense in relation to evolution.  In fact, the existence of homologous structures (things that are similar in many different species) are a major piece of evidence that supports the theory of evolution.\n\nThe thing is, the various species didn't evolve independently from primative cells.  We have common ancestors.  Our common ancestors have those features you talked about.  Our hands have approximately the same bone structure as a bat's wing because our most recent common ancestor had that bone structure in their forelimb, and there was no reason for it to change.\n\nAll land animals breath air and require water because the biochemical pathways that appeared in very early cells and have been around ever since require oxygen.  It works extremely well, so there's no reason to change it.  Most sea creatures 'breath' gasses that are dissolved in water.  Their ancestors did too, and there was no need to change.  However, there are some organims that live at the bottom of the ocean (many of which have only been discovered within the past decade or so) that have evolved somewhat different mechanisms for aquiring necessary compounds (like oxygen) because the concentration of dissolved gasses is too low that deep.  When conditions necessitate that a highly conserved process or structure change, it does.  The rest of the time it tends to remain relatively constant.\n\nPerhaps the best example of a conserved process is the genetic code.  Basically all organims use not only the same nucleotides, but the same triplets to code for the same 26 amino acids.  I think there are a couple of organims that have 1 or 2 amino acids that are either extra or missing (just through random mutations that didn't do anything bad), but for the most part it's universal.  Why is it univeral?  It works really well!  The genetic code appeared in the most primative cells, and as those cells mutated, any mutation that caused a major change in the genetic code tended to also kill the organism.  Mutations that kill the organism tend not to stick around too long, so we don't see them in any existant organisms.\n\nAs another example, you mentioned the animal's eye.  Well, an ancestoral animal developed light sensing cells.  This gave it a survival advantage, so it did well, and passed a lot of genes on to the next generation.  Through random mutation, some of its decendents (within many generations) had more developed eyes, and others had none at all.  The ones with none at all tended to die, whereas the ones with more developed eyes did well.  So most animals have eyes because not having eyes is the result of losing a trait that already exists, and eyes are adaptive so losing them is bad.\n\nSimilar structures can also result from convergent evolution.  These are known as homoplastic structures.  The classic example is bird and bat wings.  These structures serve the same purpose (flying) and have similar appearances, but the internal bone structures and the mechanical opperation of the wings is quite different.  Basically, there was this whole untapped niche of the sky, and both birds and bats independently evolved mechanisms to fly.  These structures are similar because that's the most effective way to fly.  Incidentally, the bird and bat wings are actually homoplastic as wings but homolgous as forelimbs.\n\nTo sum up, "almost all creatures on earth evolve, by chance, with so many similar structures" because it isn't by chance!
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There are missing links they know of because evolution would not make such a big leap from one type of the species to another. They can't post them because they haven't found them yet.
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a) cyanobacteria \n\nOur atmosphere would have virtually no free oxygen nor any eukaryotes if not for them....