Paired Arthropods

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

All animals with limbs have a common design. If a batwing were to be formed from a person’s hand, make the fingers extremely long; a horse elongates the middle fingers and reduce and lose the outer ones; frogs elongate the bones of the leg and fuse several of them together. All in all, despite radical changes in what limbs do and what they look like, this underlying blueprint is always present.

The octopus has several main organs that are vital to its survival; the brain for its intelligence; the ink sack for its defense; and the arms for capturing its prey. This paper will discuss these different organs and how they have evolved physiologically to its environment.

Vertebrates are known to be animals with backbones. Tooth reduction is one of the major evolutionary trends that developed among major vertebrate groups that allowed for the transition from aquatic to terrestrial life. Evolution of limbs and being able to breath air are other evolutionary trends that took placeThese trends include improved respiration and protective and insulating body coverings. More over the transition from water to land also included changing to more efficient reproductive methods like having a placenta for some animals or egg layers for other animals. Lastly, the morphology of organisms evolved such that for land they would have paired, muscular appendages used for crawling and

DNA contains the information that builds our bodies from a single fertilized egg. Cellular diversity gives rise to our tissues and organs, with distinct shapes and functions. Yet, all cells in our body contain exactly the same DNA. The resolution to this apparent paradox lies in the fact that different pieces of DNA are turned on in every cell, and these pieces are called genes. When a gene is turned on, It makes a protein that affects what the cell looks like and how it behaves. Our bodies are a composition of individual genes turning on and off inside each cell during our development. We use this information about gene “switches” to compare the activity of different genes, with the end goal of assessing what kinds of changes are involved in the origin of new organs. For limbs, we catalogue the genetic differences between fins and mammalian limbs. Then, we study the function of these genes in embryos and do experiments to manipulate genes, mutate specimens, and observe the responses to these changes. Each gene has a distinctive sequence, and using molecular tools, researches can scan another species’ DNA for identical sequences. It turns out that the DNA “recipe” to build upper arms, forearms, wrists, and digits is identical in every creature that has

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.

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

These two features earlier are examples that we can see with our naked eyes, but the DNA make up that we cannot see with our eyes alone are also laid out the same as well. In the evolutionary pathway, the genes that turn on and off for humans and fish are related through the instructions on how they function. All living things with limbs have in common the Sonic hedgehog gene (Shubin, p. 53). The Sonic hedgehog gene can control the development of the limbs in these creatures. To determine if the development of vertebrate animals can be interpreted in the same way, or have the same effect, the injection of vitamin A was used to inject into a shark, mice, and chicken embryos to see if the results were the same. The results turned out that the injection of vitamin A has indeed changed the development of limbs in these embryos. The effects cause the shark to have a mirror image of its fin, and the mice and chicken have duplication of bones in the limbs (Shubin, p.56-57). It becomes clear of what will happen if

insect, we still have to have a backbone in which we can actually add that gene towards. For

Cell proliferation in planarians carried out through the formation of the blastema regeneration and proliferating, having to require steps, mitosis and migration, to active area of planarian regeneration. Interactions between pre-existing and regenerated tissues distinguish the positional identities of tissues due to the origin of influence. Not all planarian species display morphallaxis pattern therefore not all triclad planarians such as, free-living flatworms with the characteristics of having three branches. D. lugubris species display relationship between pre-existing tissues and the blastema, forming new structures or having old structure be remodeled within pre-existing tissue. Studying planarians have hinted that organ system and cell type regulation that occur are produce d in proper proportions, developing the result defining that proportion of specific tissues in planarians models and their cell numbers correspond to each

The genome series exposed that 2 varieties of acorn worm, are the very first genomes of hemichordates. That implies that they preserve resemblances to the initial pets to develop pharyngeal or “gill” slits.

Planarians are bilaterally symmetric metazoans of the phylum Platyhelminthes usually found in freshwater streams and ponds. Planarians have the ability to regenerate large regions of missing structures and are useful for the investigation of anterior-posterior (AP) polarity in occurrence with molecular and cellular mechanisms. Regeneration involves integration of newly made self-assembled tissue into older pre-existing tissues (Alvarado 2006). Adult somatic stem cells called neoblasts that are distributed throughout the planarian body (Reddien and Alvarado 2004) allow for the regeneration of individuals from minute fragments. Neoblasts are the only mitotically active cells in planarians (Newmark and Alvarado 2000), and can generate any of the

What type of structure does Insectopia have and what are the positive/negative effects of such a structure?

Another advancement in sophisticated animals is the development of a head. This is an obvious gain on the animal's part but is often taken for granted. Heads allow for extremely complex structures such

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).