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.
An inspection of the modern animal phyla will reveal that eyes are just as diverse as they are complex. Some organisms like the rag worm have pigmented cup eyes while other like he box jellyfish have two lens eyes and two pairs of pigment pit eyes. To account for the diversity in eye structure, we must first examine the eye ‘prototype’, the original structure that was acted upon by evolution. The simplest organ that can be considered an eye is composed of a single photoreceptor cell and a single pigment cell, without any lens or other refractive body (Arendt, 2003). Such organs are know as eyespots, and...
... middle of paper ...
...2007).Evolution of the vertebrate eye: opsins, photoreceptors, retina and eye cup. Nat. Rev. Neurosci. 8: 960–976.
Land, M.F.1965. Image formation by a concave reflector in the eye of the scallop, Pecten maximus. J. Physiol. (Lond.) 179: 138 153.
Piatigorsky, Z., Kozmik. 2004.Cubozoan jellyfish: an Evo/Devo model for eyes and other sensory systems. Int J Dev Biol 48: 719–729
Singla, C. L. 1974. Ocelli of hydromedusae. Cell. Tiss. Res. IJ9; 413-429.
Sousounis, k., A. Ogura, and P.A. Tsonis. 2013. Transcriptome Analysis of Nautilus and Pygmy Squid Developing Eye Provides Insights in Lens and Eye Evolution. PLoS ONE 8(10): e78054
Wells, M.J. 1997. Cephalopod Behaviour. Trends ecol evol 12(2): 82-83
Wistow, G. J., and J. Piatigorsky. 1988. Lens crystallins: the evolution and expression of proteins for a highly specialized tissue. Annu. Rev. Biochem. 57: 479-504.
Barlow (1953) first postulated the existence of feature-sensitive ganglion cells in a frog’s retina based on an inhibitory-surround structure of the receptive field. He maintained that the “on-off” units of these cells triggered by the presence of a particular stimulus corresponded to certain behaviour in the frog. For example, presenting a spot of light in the visual field would cause certain neurons to fire in a particular ganglion cell, and in a live frog, would cause the frog to snap at the stimulus. Barlow concluded that these cells must be “fly detectors”. Lettvin et al. (1959) further examined the visual mechanisms of the frog and discerned fo...
Suddenforf, T. (2009). The Evolution of Primate Visual Self-Recognition: Evidence of Absence in Lesser Apes. Proceedings: Biological Sciences, 1671-1677. Retrieved May 2, 2014, from http://www.jstor.org/stable/10.2307/30244994?ref=search-gateway:81407c811d684607878e4295bbbf261a>
Palka, J. and Olberg, R. (1977). The cercus-to-giant interneuron system of crickets. III. Receptive field organization. J. comp. Physiol. 119, 301–317
Introduction: The Lophophore is a characteristic feeding organ possessed by four major groups of animals: the Brachiopod, Bryozoan, Entoprocts, and Phoronida, which collectively constituted the Lophophorata. [1] All Lophophore are found in aquatic organisms The Lophophore can most easily be described as a ring of tentacles, but is often horseshoe-shaped or coiled. Why do we call the tentacles a Lophophore? Because the tentacles have several distinctive characteristics that differentiate them from the tentacles of other animals. The tentacles are hollow. Hollow cavities in the bodies of animals (except for the gut) are called coeloms: the hollow cavity in the Lophophore is the second of the three divisions of the coelom in the entire body. The mouth is always inside the Lophophore ring of tentacles the Lophophore tentacles are covered with cilia (hair) they are responsible for generating a current of water that flows toward the mouth. These distinctive characters make the Lophophore a complex structure. Since it is complex, the possibility that it evolved independently in three separate groups of animals is low. Therefore, one can form a hypothesis that the last common ancestor of brachiopods, bryozoans and Phoronida also had a Lophophore.
The optic nerves communicate information from the retina to the brain for decoding. The optic nerves, although lacking their myelin coating, are all formed in the womb before b...
Fox, R. 2001. Invertebrate Anatomy OnLine: Artemia Franciscana. Lander University. http://webs.lander.edu/rsfox/invertebrates/artemia.html, retrieved February 13, 2011.
The feeding structure of an echinoderm, for example a sea star, has both a mouth and an anus making it a complete digestive system. The mouth is on the oral side of the sea star and the anus is located on the abor...
The middle layer of the eye includes the iris, the ciliary body, the lens and the choroid. The iris gives a person’s distinct eye colour, controls the size of the pupil and hence the amount of light entering the eye. It separates the anterior and posterior chambers in the front part of the eye. These chambers contain the aqueous humour, which is important in nourishing the lens and cornea. The lens is a shear, flexible structure, which changes its shape and hence participate in focusing one’s vision on close or distant objects. The vitreous humor is a jelly-like substance that fills the back portion of the eye. It has a structural function and is involved in maintaining the eye’s shape, but also helps transmitting the light to the retina. The choroid is a membrane found between the sclera and the retina. It lines the back of the eye and is rich in blood vessels. It is highly pigmented in order to absorb light and prevent scattering.
A whole lot of hypotheses have been used to explain the quick expansion of animal species in the early Cambrian period about from about 541.0 million to about 485.4 million years ago. The most modern explanations for the Cambrian explosion takes pieces of a lot of these hypotheses and melds them together; incorporating genetic, ecologic, abiotic conditions that set the evolutionary wheel in motion. The current state of understanding the Cambrian explosion still remains a topic of open and exciting debate. The processes in the hypotheses can be stand-alone or very tightly interconnected and mutually supporting of another. One can say the complexity of modern Animalia can be attributed to the complexity of the processes that happened during the rapid diversification attributed from an interaction of biotic and abiotic processes in the Cambrian period.
of the eye, this is what gives form to the eyeball. The vascular tunic has three
However, they are neglected by many Darwinists and isn’t considered to be proof against Darwinism. Many of the evidence Darwin proposed to prove his evolution does not exist, as said in the beginning of the paper, many Darwinists create fraudulent evidence to prove evolution. If evidence has obvious evidence, why does scientist go out of their way to create false evidence for evolution. Darwin also admitted that it would be obstinately absurd that the human eye could be a product of natural selection. His uncertainties are voiced in his book, The Origin of Species,”To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.” Here Darwin admits that the human eye, in all of its intricacies, could have not been made by trial and error. However, the human eye is not considered to be stable evidence against evolution. University of Chicago biology Professor Jerry Coyne doubt that the human eyes could have suddenly appeared as full fledged eyes, but rather evolved from simpler eyes. However, the oldest eye in the fossil record, a trilobite eye, is a very complex faceted compound eye that “dates” back to the Cambrian explosion, approximately 540 million years ago. Darwinists often claims the primate eye is the most evolved amongst the species, but the bee’s eye can register 5 times more images per second than
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.
More than 40 million people across the world that suffer from blindness, but the bionic eye has advanced leaps and bounds ahead of its time and it could recover a very large portion of their blindness (Bhojani). The advancements in the visual prosthesis field started with the invention of the cortical prosthetic. Since then, there has been a variety of different devices which target different places along the visual processing pathway. These devices can be broken down into categories depending upon where the device is taking action. The history and development of these devices can be broken down into two different categories: electrical stimulation, and electronic prosthesis (Ong).
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.
As further protection, the eyelids automatically close when an object suddenly moves close to the eye.Parts Of the EyeThe eye is made of 3 coats, or tunics. The outermost coat consists of the cornea and the sclera. The middle coat contains the main blood supply to the eye and consists of the choroid, the ciliary body, and the Iris. The innermost layer is the retina.Cornea and ScleraThe Sclera, or the white of the eye, is composed of tough fibrous tissue. On the exposed area of the eye the scleral surface is covered with a mucous membrane called the conjunctiva.