The great debate over how the head segments of existing arthropods are aligned was largely dispelled in the late 1990s when the expression domains of Hox genes were first applied to the study of Arthropod evolution. The traditional concept that chelicerates had lost a deuto cerebral segment and that the chelicerae was innervated by the tritocerebrum was overturned when the anterior expression domain of labial, the anteriormost gene of the arthropod Hox cluster, was found to align the chelicerae with the first antenna of mandibulates (Edgecombe and Legg 2014). This alignment of the head was later confirmed by resemblances in the developing nervous systems of Limulus and crustaceans and is now widely supported by scientists. Another study that …show more content…
Even greater controversy surrounds the segmental alignment of head structures in many fossil arthropods and those of extant taxa, a exhibition of the so-called arthropod head problem. Much of the debate involves the interpretations of structures in Cambrian fossils variably described as frontal appendages or great appendages. Whether predatory appendages in such taxa as anomalocaridids and megacheirans belong to the same head segment and with which neuromere of the brain they are associated is the heart of the problem(Edgecombe and Legg 2014). More recent studies consider these appendages to either be or not be segmentally …show more content…
The traditional basis for identifying the segmental association of modified appendages in fossil arthropods has been to use structural correspondence in appendage morphology (e.g. the elbow joint and chelate tip of megacheiran great appendages suggest homology with chelicerae) and to integrate their relationships to other appendages (i.e. an apparent association of megacheiran great appendages and antennae in some taxa suggests the former are trito cerebral/postcheliceral if the antennae are deuto cerebral as in extant arthropods) (Edgecombe and Legg
Fox, R. 2001. Invertebrate Anatomy OnLine: Artemia Franciscana. Lander University. http://webs.lander.edu/rsfox/invertebrates/artemia.html, retrieved February 13, 2011.
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
One hundred and fifty million years ago, large aquatic species of reptile such as the Plesiosaur dominated the ocean, and were pre-eminent predators of the sea. The branch of now extinct Plesiosaurs, or ‘near lizards’, evolved into variant closely related species specialised to take different niches in the food chain. Such species of Plesiosaur include the phenotypically similar Plesiosauroid and Pliosauroid. The physiological adaptations of the long necked variant, the Plesiosauroid, as it relates to deep sea diving, will be addressed in depth.
Acanthostega had a fish-like tail and gills for breathing under water, this being the aquatic part of it. But at the ends of the arms were “peddle-shaped” appendages, thought to be the first “hands” on Earth. Clack’s discovery proved that some fish had arms and legs in the water. It showed that arms and legs were already evolved before organisms started actually living on land, they were used more for survival than walking. In a sense, the “blueprints” of an arm were already in place.
There are two distinct infraorders of Anthropoidea that have been evolving independent of each other for at least 30,000,000 years. They are the Platyrrhini (New World monkeys) and the Catarrhini (Old World monkeys, apes, and humans). These two diverse groups of species can be distinguished from each other most easily based on the form of their noses and by the number of specific types
Pigeon’s Egg Head (The Light) Going and returning from Washington is painted by George Catlin in 1837-39. This painting portraits the extraordinary changes an Assiniboine warrior underwent by comparing his appearance when he was traveling to and coming back from capital city Washington, DC in 1831. In his amazing art work, Catlin argued the cultural conflicts that rose when indigenous people and Euromericans interact. Incorporating different formal elements such as using of lines in different direction, variety of colors at a different intensity, value and tone, changing texture at different part of the painting and organization of individuals and objects in such specific relationships helped Catlin to convey his massage effectively for almost
The Kore shows Roman admiration for early Greek art; the statue is created with outstanding quality. Kores were votive offerings to Athena originally, but were soon seen as gifts for all Goddess. Whole Korai’s were normally painted and dressed in peplos, which was a rectangular cloth particular made of wool. Korai’s were also statues that showed significant realism, with the ability to show the straight lines and detailed effects. Ancient Greeks have the trait of competition to give credit to, sculptors often competed with each other in an attempt to see who created the most naturalism sculptures. Which wasn’t a bad thing as you see how beautiful the sculptures of ancient Greek
Greek mythology is thought to be very fascinating to many people; I personally wanted to learn more about it and the Hellenistic period. A new cultural age was led by Alexander the Great when he took over Egypt and the Near East, historians refer to this period as Hellenistic.
Although the Hippocampus spp. are placed into the same class as other organisms more traditionally viewed as fish, their morphology bears distinct differences in comparison to other bony fish. The various species belonging under the genus Hippocampus range in maximum size from 20 mm to 300 mm(Foster 8). Their physical appearance is distinct from other members of its class due to their "horse-like head, monkey-like tail, and kangaroo-like pouch."( Lourie et al 12) Morphologically, seahorses do not have scales like traditional fish, but rather posses bony plates covered by skin. The appearance of bony extrusions and skin ...
Hammond, N. G. L. "The Branchidae at Didyma and in Sogdiana." The Classical Quarterly 48.2 (1998): 339. Academic OneFile. Web. 5 May 2014.
The eye is an extremely diverse organ, ranging in complexity across and within animal phyla. Here, a comparative approach is taken to outlining the diversity of the eye forms within vertebrates and invertebrates. The eye morphology of a variety of organisms was examined. Eye function, and placement on the body was also considered. Here, variation in eye form is discussed in relation to the environment the organism is adapted to. It is shown that an organisms eye morphology functions optimally for the ecological niche it occupies. Evolutionary analysis is used to account for the emergence of the different eyes. Convergent evolution is used to justify the similarities in eye types seen in organisms of different species. This analysis begins with the simplest of eye forms composes of single cells, present in the zooplankton larvae. Such primitive forms are identified in mollucs, annelids, cnidarians, and are then compared to more advanced eye forms contain lenses. This comparative approach provides a breadth of examples of vertebrates and invertebrates, making visible, the diversity of eye morphology within the animal kingdom.
...nder, C., Tsai, C., Wu, P., Speer, B. R., Rieboldt, S., & Smith, D. (1998/1999/2002). The permian period. Informally published manuscript, Biology 1B project for Section 115, University of California Museum of Paleontology, CA, Retrieved from http://www.ucmp.berkely.edu/permian/permian.php
.... (2011). A New Arthropod Jugatacaris agilis n. gen. n. sp. from the Early Cambrian Chengjiang Biota, South China. Journal of Paleonotology, 85(3), 567-586. doi:10.1666/09-173.1
When these alterations are helpful, they grow to be fixed in a population and can result in the evolution of new phyla. Evo-devo seeks to figure out how new groups happen by understanding how the method of development has evolved in different lineages. In other word, evo-devo explains the interaction between phenotype and genotype (Hall, 2007). Explanation of morphological novelty of evolutionary origins is one of the middle challenges in current evolutionary biology, and is intertwined with energetic discussion regarding how to connect developmental biology to standard perspectives from the theory of evolution (Laubichler, 2010). A large amount of theoretical and experiential effort is being devoted to novelties that have challenged biologists for more than one hundred years, for instance, the basis of fins in fish, the fin-to-limb change and the evolution of feathers.
The world we live in today is full of an exceptional variety of animals. The time it took to conclude to the various sorts of species seen today has been throughout a period of millions of years. The vast majority of these animals are accredited to evolutionary advancements. When the environment changes, organisms have become accustomed to changing to fit their environment, to ensure their species does not die off. These physical changes have resulted in different phyla, ranging from basic structures, like sponges to advance systems, like that of an octopus.