Arthropoda Phyla

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.

a) The structures and the afferent division of the peripheral nervous system that are involved in

On this image, we see the external dorsal side of a preserved crayfish. As part of the largest animal phylum the Arthropoda, the body of the crayfish is segmented, with jointed appendages and exoskeleton. The paired antennae (1) are long appendages located the front of the mouth and modified for help the animal to sense touch and taste. The antennules (2) are shorter, also paired with the same function but they also help to maintain balance. The chelipeds (3) are located on the front of the thorax, and they are responsible for defence and grasping food. On the at ventral part of the thorax, we found four pairs of walking legs (4), with these legs the crayfish changes locations on the bottom of freshwater lakes, streams and also on land. They

Fig. __ Feed-forward projections from the eyes to the brain and topographic mapping. In each eye the visual field on the left and right of the fovea (the cut goes right through the fovea!) projects to different cortical hemispheres: the ipsilateral retina projects to the ipsilateral visual cortex, and the contralateral retina crosses the contralateral cortex (hemifield crossing in the optic chiasma). The first synapse of the retinal ganglion cells is in the lateral geniculate nucleus (LGN), but information from the left (L) and right (R) eye remains strictly separated. The LGN consists of six layers, layers 1 and 2 are primarily occupied by the magnocellular pathway, and 3–6 by the parvocellular. Information from both eyes comes first together

The planarian is the first organism ever to have a fully productive synaptic nervous system (Mueller 2002). The synaptic nervous system contains nerve cells and it is when a neuron sends a signal, either electric or chemical, to another neuron and that signal contains information to be passed on or acted on (Mueller 2002). With the neural genes that are in planaria, they are able to build another fully function central nervous system, or CNS, without any of the old CNS (Cebria 2002). The CNS of a planarian is consisted of a brain in the head region and two ventral nerve cords that run down the body (Cerbria 2002).

Steele, V.J., and Oshel, P.E 1989. Ultrastructure of the attachment cells of the organ of Bellonci in Gammarus setosus (Crustacea, Amphipoda). Journal of Morphology, 200(1), 93-119.

Phase 2: Retina is placed in the back side of the eye and it has to „collaborate“ with cornea and lens in order to provide an image for

The kingdom Animalia means animal. The phylum Chordata includes animals with vertebrates. The class Chrondrichthyes includes cartilaginous fish, which are fish that has a skeleton made of cartilage rather than bones. The family Lamnidae includes sharks as the white shark and mackerel sharks. These sharks are usually very large and can swim really fast. The genus is the group before the species which includes other sharks that are very similar to the white shark. The species is the last group, which contains the Latin name of the specific organism. Through taxonomy, scientists are easily able to identify and classify species.

From the beginning of time the simplest of life forms can be linked to those characteristics that human possess. Amphioxus is a small sea dwelling creator that has no eye, ears, or jaw but can be linked to humans by its nerve cord, segmented muscles that aid in movement, notochord that acts like a backbone, and the gill slits just like the ones human embryos possess.

In this lab, we conducted multiple experiments on planarians and examined their reactions toward variety of stimuli. First and foremost, we have to be able to identify the fundamental structure of the planarians; especially the nervous system. Planarians are grouped into Class Turbellaria. They have a central nervous system that consists of 2 to 6 ventral nerve cords and subepideral nerve net also known as cephalization. Cephalization is more advanced because the system now has more neurons, sense cells, larger ganglia compared to the simple nerve net system. The ventral nerve cords are connected to ganglia that lay interiorly to the ventral epidermis that close to the midline and run the length of the body (Scott, 2014, p. 54). The information

According to Moroz (2009) two hypotheses are given to describe the evolution of the CNS. These are monophyly and polyphyly. According to monophyly all the neuronal cells originated from a single ancestral cell lines. Another hypothesis known as polyphyly, complex brains originated from multiple origins in different animal lineages. In 1830, Geoffroy suggested the homology of ventral and dorsal sides of the vertebrates. In 1994, Arendt et al., repotedted that during the evolution of chordates inversion of the dorso-ventral body axis took place and the ventral side of the ancestral arthropods become the dorsal side of the

cesses; glial cells; and an investment of sheath cells. Sheath cells are absent in Octopus

The terrestrialization of tetrapods was a major evolutionary achievement and the basis for the diversification of all future land vertebrates. Among the most important innovations was the tetrapod limb, which evolved from the fins of ancestral lobbed-finned fish. Most notably, the dermal fin rays and rigid fin fibrils common to all fish species disappeared during limb evolution. Early pectoral fin formation in teleost embryos share many morphological similarities to early limb development. One of the first major differences is the fate of the apical ectodermal ridge (AER). The AER is a thickening of ectodermal cells in the distal bud. It is responsible for mesenchymal survival, proliferation, and bud outgrowth. In tetrapods, the AER regresses

Visual processing in our brain cannot be done without actual vision. The anatomy of the eye is carefully arranged with all the parts that assist our vision in an optimal way. A layer of connective tissue called the sclera surrounds the eyeball. Underneath it is the choroid, which is rich in blood vessels that supply the eye. Attached to this layer is the lens by cililary muscles. The lens focus light to the retina and the amount of light entering is controlled by pupil dilation or constriction. Pupil dilation and constriction is regulated by the iris of the eye which consist of two layers of smooth muscle layers that contract or constrict to increase or decrease the diameter of the pupil respectively. The retina is the inner most layer of the eye. It the main site of photoreceptors that convert light energy into electrical energy where the information gets sent to the brain and is what we perceive as vision. (Marieb, 2014)

To understand the applications of mantis shrimp vision; we must first understand how the eyes of the mantis shrimp work. The compound eye of the mantis shrimp is made up of many ommatidia; “an ommatidium is like a simple but complete photoreceptor organ consisting of optical components and receptor cells” Most research suggests that the vision experienced by the mantis shrimp is due to three distinct regions in its eye; there is an upper and lower hemisphere separated by the midband; these regions are made of distinct ommatidia; adapted and responsible for different functions in the eye of the mantis shrimp. The research I have come across suggests that the most important region is the modified midband because this is the