The Development of Chondrocranium of Chondrichthyes Essay

16. In bone structure, the cortex can best be described as which of the following?

s Flat bones Irregular bone Sesamoid bones Anatomy of a Long Bone Epiphyses Metaphyses Epiphyseal growth plate Epiphyseal growth line Diaphysis Periosteum Medullary cavity Endosteum Articular cartilage Microscopic Anatomy Compact bone Osteons Spongy bone Trabeculae Bone Formation Intramembranous ossification Endochondral ossification Cells in Bone Osteogenic cells Osteoblasts Osteocytes Osteoclasts Hormonal Control of Bone Calcitonin Parathyroid hormone Osteology of the Axial Skeleton Frontal Parietal Temporal Zygomatic arch Mastoid process Occipital Foramen magnum Occipital condyles Sphenoid Sella turcica Greater wing Lesser wing Ethmoid Cribriform plate Crista galli Nasal Maxilla Alveolar process Palatine process Zygomatic Zygomatic arch Lacrimal Palatine Inferior nasal conchae

It lacks a backbone, but has a nerve cord that runs down its back and a rod that runs the length of its body parallel to the nerve cord that supports the body (notochord). Humans have a notochord as an embryo, but it breaks up and becomes part of the disks that lie between our vertebrae. Also shared with Amphioxus are gill arches, the bar of cartilage associated with each arch and the cartilage that form jaws, ear bones and our voice box.

After this Shubin goes on to talk about the genes that control the development of the arches. Some of these genes include Hox genes which can be found in all of the arches, these genes turn other genes on and off. This knowledge allows for experiments that test what genes control what. This leads Shubin to talk about Amphioxus, an ancient worm, and first animal with a nerve cord, and a notochord to support it, but no backbone. These worms also have the same arches that we have when developing, showing how our heads similarity to this ancient

gills sprouting small feather-like appendages. Although colloquially known as a ‘walking fish’, it is in fact

animal in the early stages of growth when it’s basic structure and organ development is forming.

Growth is an important part of a humans life, from bone growth to even brain growth. Development refers to change that occurs from birth to death. Surprising developments occurs before birth during the creation of an organism, but many changes still occur after birth. “Development usually involves growth, but it also involves differentiation and morphogenesis. Differentiation is change in cell structure and function from generalized to specialized, and morphogenesis (mōr-fō-jen′ě-sis) is change in the shape of tissues, organs, and the entire organism.”

Obviously a very fierce animal, the skate, related to the ray, has special adaptations that can allow it to be protected from predators and to perform actions with ease. Seeking and consuming prey with ease, the skate has its mouth on its underside and it can eat prey that is hiding in the sand below it. Quickly swimming away from predators or to attack prey, the skate also has tiny teeth-like structures on its skin. The FLMNH Ichthyology Department reports, “The skin feels exactly like sandpaper

Significant changes in internal organs development can be revealed from larval and pupa stages in complete metamorphosis. According to [1] between day one to day thirteen, the chrysalis shows development of numerous aspects of morphology which include wing veins, midgut, flight

Fish started to evolve during the Cambrian explosion. Early fish fossil records act for by a small group of fish that are jawless and that have armored scales, which are known as ostracoderms. Jawless fish lineages are mostly extinct. An extant clade, the lampreys may indefinite ancient pre-jawed fish. The first fish with jaws were found in Placoderm fossils. The range of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is not clear if the advantage of a hinged jaw has a stronger biting force, improved respiration, or a combination of

Because of this body shape the skate’s eyes are positioned on the top of its head, while the mouth and gill slits are found on the bottom side. While the placement of the skate’s jaw and gills may look comical, this morphology has been expertly honed through thousands of years of evolution for the dietary needs of the ray. The rays mouth contains rounded teeth that that they use to grind food from the bottom of the ocean floor. Most fish have well discernable pectoral fins, the leopard skate’s fins resemble an elongation of the back. The pectoral fins run the full length of the skate’s body, where as a typical pectoral fin is much smaller and typically ends before the first dorsal fin. Along with comparatively large pectoral fins, skates

Look at the photo of a Pacinian corpuscle. Notice the onion-like bulb of connective tissue. Describe briefly —

1. Many experiments were conducted during the 1950s and 1960s with chick embryos and they showed that two patches of tissue essentially controlled the development of the pattern of bones inside limbs.  Describe at

Through research of the embryonic development of the ascidians, scientists were able to better understand the vertebrate gene function and regulatory networks of several processes. The ascidia genes involved in the formation of the notochord, which were shown to be analogous to those of tadpoles, and were consequently mapped in order to obtain information regarding gene function in vertebrates. In addition, the developmental processes in ascidia embryogenesis were studied in great detail, leading to advances in the conception of the regulatory network's involvement in governing notochord differentiation and also the process leading to the formation of the tail (Corbo et al. 2001).

In the science of paleontology, the history of life is studied. Paleontologists study fossils to learn the past ecologies, evolution, and the origins of humans. In order to understand the processes that have led to both the origination and destruction of organisms since life began, paleontologists incorporate both scientific knowledge and studies. Fossil findings are critically important for confirming predictions of evolution theory. Of the many discoveries that are made yearly to add depth to the understanding of evolution, an example is a recent discovery of a creature they named Tiktaalik. The Tiktaalik was uncovered to be a transitional animal between shallow-water fishes and limbed animals. The creature supports the idea that it emerged from both mammals and reptiles, suggesting that the two are related. These findings support prediction of evolution, contradicting the belief that God