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...
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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...
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.
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.
Vision plays a huge role in the lives of non-human primates. Non-human primates have exceptional binocular vision, due to forward-facing eyes with overlapping visual fields (Prescott). This binocular stereoscopic color vision allows primates to see the world in terms of height, width, and depth, also known as three-dimensional vision (Haviland et al. 2010). Highly developed vision allows the later arboreal primates to judge depth, distance, and location when moving at speed from branch to branch (Haviland et al. 2010). This bino...
Peripheral vision is used amongst every species ranging from a deep-sea marine animal to a bird flying hundreds of feet above the ground. However, each species’ vision differs to some degree and also differentiates within the species itself. This can be due to various types of eye conditions.
Long standing arguments against the theory of natural selection stem from the occurrence of incipient structures and complex traits in organisms despite the seemingly stochastic nature of mutations. Many complex adaptations observed in nature today are thought to have arisen from less complex ones with simpler functions, therefore these characters are thought to have been “pre-adapted.” In order to go from a simple to a complex structures there must have been a transitional phase, where the two structures function simultaneously or where the new function is assumed without interfering with the old function. These structures are termed incipient or incomplete, and given what we know to be true of natural selection and the theory of evolution it becomes hard to reconcile the idea that natural selection continued to favor these structures despite the lack of selective value. Incipient structures are thought to be neither sufficiently large enough not elaborate enough to perform an adaptive function and thus it also becomes difficult to understand how larger complex characters arise. A discussion of morphological and developmental genetics explains that these structures have been performing useful functions since their simple origins, therefore being selectively favored while at the same time evolving to become large enough to accumulate new more complex functions. Modification of pre-existing genes and regulatory circuits in early development has been extensively studied in metazoans, Hox genes and the development of complex structures such as eyes, limbs and appendages. Phenotypic variation is therefore generated via the modification of existing genes, regulatory processes and developmental processes and this variation is acted o...
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.
the eyes had densely packed lenses and may have served merely as a light sensitive
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...
...is. Moreover, the relationship between neo-Darwinian evolutionary theory and evo-devo is highly contested (Hoekstra and Coyne, 2007; Minelli, 2010). However, the understanding of evo-devo methods and how the characteristics of the morphologies of different species diverged eventually is still comparatively limited. Craig (2010) stated that this field has obviously contributed to the understanding of genes and, subsequently, the understanding morphological characteristics of evolution in intricate organisms. There has been significant confirmation of evo-devo’s claim that regulatory modifications play an essential role in the evolution of shape. Evo-devo is the process of becoming a conceptual hub for an even larger integration of research areas in organismal biology, including genetics, ecology, paleontology, behavior, cognition, and other fields (Gerd B. Müller)
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
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 evolution from water to land was a major event in the vertebrates. Species respiratory, circulation, and reproduction system show how they evolved and adapted to the environment. Vertebrates who belong the phylum Chordata had at least at some point of their life, a dorsal hollow nerve cord, a notochord, pharyngeal pouches, and a tail that extends beyond the anus. It is said that fishes were amongst the first vertebrates. The earliest fish to appear in the fossil record were jawless, covered with bony plates, gills, scales, but no fins. According to Arreola, they later evolved by adapting to their environment and began to form jaws and paired fins. The jaws were useful with their muscles and teeth, which helped them eat a wider variety of food, and were even able to defend themselves by bi...
The Eye is the organ of sight. Eyes enable people to perform daily tasks and to learn about the world that surrounds them. Sight, or vision, is a rapidly occurring process that involves continuous interaction between the eye, the nervous system, and the brain. When someone looks at an object, what he/she is really seeing is the light that the object reflects, or gives off.