biology reading quiz q1: which of the following is/are example(s) of analogous structures? So both the statements are incorrect. Well, depending on what you are looking at, they are homologous and analogous. However, analogous structures themselves are evidence for the theory of natural selection and the accumulation of adaptations over time. This example of analogous structures is especially useful because one of the most common claims made by religious creationists is that something as complex as an eye couldn't possibly have evolved naturally - they insist that the only viable explanation is a supernatural designer … a) the front leg of a frog and a bat wing b) the front leg of a horse and a human arm c) an octopus eye and a human eye d) the wing of a bird and a bat wing. On cursory examination, the single-chambered eyes of octopus with their spherical lenses resemble vertebrate eyes. Structurally, that is the only difference between the eyes. The diagram below shows the similarities of evolutional structures between the two eyes of a human and octopus. New research studies on ocular gene expression are being performed using cephalopod eyes due to the evidence of their convergent evolution with the analogous human eye. Usually, the cause of convergent evolution is similar selection pressures in the environment. Their version of the camera eye was converging evolutionary up until the point of their common ancestor of the bilateria group . However, sharks are fish and dolphins are mammals. Campbell, without blinking an eye, tells us that RNA splicing in Pax6 "has been used to create a camera eye in a surprising lineage…. The eye of a human is very similar in structure to the eye of the octopus. Why would different species become more similar? For instance, the avian ancestors of birds and the mammalian ancestors of bats both evolved wings independently, in an example of convergent evolution. Now that he has this one "master control" gene timed before the Cambrian explosion, he feels free to let it orchestrate any work Darwin puts on the playlist: compound eyes of bees, whale eyes, squid eyes, and human eyes. Although the acquisition of camera eyes in the cephalopods is yet a problem, Pax-6 variants in cephalopods have been acquired in a lineage-specific manner. Remarkably these features have evolved multiple times in different lineages of animals. One kind of editing, called splicing, removes a piece from the middle of the code, and stitches the two ends together. Therefore the eyes of octopuses are also referred to as ‘Camera Eyes’. But then —. But then — without any possible cross-communication — another Pax6 gene on a completely separate branch leading to vertebrates had to learn to create a camera eye all over again. A hint of that embarrassment surfaces in the last sentence of his first paragraph: Eyes and wings are amongst the most stunning innovations evolution has created. In other words, the environments in which the two different species live are similar and those species need to fill the same niche in different areas around the world. Their eye shared 1019 out of the 1052 ancestral sequences. In this video, Dave shows Ultra Super Macro images of octopus eyes, taken at the Blue Heron Bridge in South Florida. Despite their many differences (e.g., aquatic vs. terrestrial, predator vs. scavenger), sharks and mice are closely related; they are both vertebrates and share many other anatomical homologies (such as a vertebral column). It takes more than appearance to determine which species are closely related and which have evolved from different ancestors to become more similar through their analogous structures. The question is... did that worm possess eyes that it passed on to the octopus and/or the human? The paper he references actually says very little about evolution. It certainly doesn’t explain how this one gene could "create a camera eye." Rather than providing instructions to make an eye part, these genes provide information about where and when parts need to be constructed and assembled. The human eye is categorized the same way. RNA code is interesting in that it can be edited. However, the octopus and the human are not closely related and reside far from each other on the phylogenetic tree of life. And this shows that the evolutionist claim based on resemblances is completely unscientific. A reasonable observer should be astonished at the brashness of such claims. Sounds good for design theory so far. The primary structures of an octopus’ eye are the iris, lens, vitreous gel (the mass of the eyeball), pigment cells, photoreceptors, retina, and the optic nerve. This can lead to analogous structures in different species that occupy the same type of niche and environment in different locations. Octopuses, on the other hand, focus by moving the lens closer to or further away form the retina. the lineage that includes squid, cuttlefish, and octopus — the cephalopods." Another difference is in the cellular structure of the octopus eye and a mammalian eye. However, the octopus and the human are not closely related and reside far from each other on the phylogenetic tree of life. (Emphasis added.). However there are also apparent differences. This is an example of . RNA made from the Pax6 can be spliced in just such a manner. This means that dolphins are more closely related to rats than they are sharks on the evolutionary scale. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. However, the question of which category they will put an organ into, homologous or analogous, is answered totally in line with the theory of evolution's preconceptions. Since natural selection works the same way in these environments, the same types of adaptations are favorable, and individuals with favorable adaptations survive long enough to pass down their genes to their offspring. Campbell, writing about a paper in Nature Scientific Reports, "Cephalopod eye evolution was modulated by the acquisition of Pax-6 splicing variants," has to tackle genetic convergence along with functional convergence. Malcolm Campbell must feel at least a tinge of embarrassment for his proposal in The Conversation that the same "stunning innovations" in nature evolved not just once, but multiple times independently, here specifically in vertebrates and cephalopods. But a bat is more closely related to a human than to a bird or an insect based on homologous structures. Exactly how such convergent evolution arises is not always clear. These Pax-6 splicing variations in cephalopods were controlled spatio-temporally during eye formation. To accommodate this, evolution increased the number of instructions that arose from a single Pax6 gene…. Analogous structures are not necessarily evidence that two species came from a common ancestor. Both eyes are round and have the same structural traits. Pax6 RNA splicing in cephalopods is a wonderful demonstration of how evolution fashions equivalent solutions via entirely different routes. The Difference Between Analogy and Homology in Evolution, Anatomy, Evolution, and the Role of Homologous Structures, The Difference Between Homology and Homoplasy, Questions to Ask Your Biology Teacher About Evolution, M.A., Technological Teaching and Learning, Ashford University, B.A., Biochemistry and Molecular Biology, Cornell University. These studies replace the previous Drosophila studies for gene expression during eye development as the most accurate, although Drosophila studies remain the most common. There are many types of evidence supporting evolution, including studies in the molecular biology field, such as DNA, and in the developmental biology field. selected answers: an octopus eye and human eye the front leg of. Both have an eyelid, cornea, retina, pupil, iris, lens, and optic nerve. The wings of a bird and of an insect are analogous organs. Even though all these species have wings and can fly, they are very different in other ways. Cephalopods -- which include octopus, cuttlefish, and squid -- have a camera eye similar to ours, even though they belong to a different clade altogether. As a consequence, two different kinds of instructions can be generated from the same Pax6 RNA. While homologous structures show how similar species have changed from their ancient ancestors, analogous structures show how different species have evolved to become more similar. Great job! Both of these species have wings that they use for flight and yet their wings came from dissimilar ancestral origins. Cephalopods have a camera eye with the same features as the vertebrate camera eye. Sign in Register; Hide. The human eye and the octopus eye both have the same morphology as each other, and are structured the same way. An example of an Analogous Trait would be a human eye and an octopuses eye. In some cases, systems emerged that are unique to modern cephalopods (e.g., the chromatophore system; for review see Packard et al., 1988; Demski, 1992), while other systems evolved analogous in structure and function to those of vertebrates (e.g., camera eyes … Design advocates know all this and see it as evidence for design. Then, tens of millions of years later on the branch leading to cephalopods, it had to "create a camera eye" that is a wonder of nature in squids and octopus. Using analogous structures, evolution can provide remarkable innovations. The octopus and the human are not closely related, whatsoever, yet the eye of a human is very similar in structure to the eye of the octopus. Two different species that have analogous traits are the human eye, and the octopus eye. They may go through different developmental and functional stages before they are fully alike. Structural similarities between human and octopus eyes. This led to incorrect groupings compared to evolutionary origins of the species. Another important example would be the development of a camera-type eye in both mollusks and vertebrates. One of the most notable examples of analogous structures is human and octopus eyes. because they both have different structures of eyes but evolving for the same function and hence having similarity. In fact, the octopus eye is superior to the human eye in that it does not have a "blind spot". However, the most commonly used types of evidence for evolution are anatomical comparisons between species. Is it ever? Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. The eye has evolved independently several times over earth's history and is a great example of convergent evolution. Both are used for seeing of course but have very different structures. Analogous structures don't have to share the same evolutionary path. Humans bring their eyes into focus by changing the shape of our lenses using the cilliary muscle. For example, the retina of the octopus is everted instead of inverted, and it is equipped with primary rhabdomeric photoreceptors rather than secondary ciliary variety found in the retina of the vertebrate eye. Just because species look or behave the same doesn't mean they are closely related. In order to create such an elaborate structure, the activities Pax6 controlled became more complex. They have lenses that refract light, pupils that dilate to restrict, or let in more light. The human eye and octopus eye are used to hunt for … The most important of master control genes implicated in making eyes is called Pax6. Which of the following is/are example(s) of analogous structures? : Mapping the eyes on the tree. Although the Octopi shares a common ancestor with many different unique homologous organisms it eye was not the only part of the octopus undergoing evolution. *Homologous Structures. But both the organs perform a related function, that is focusing the light on the retina, and are therefore an example of Analogous … The human leg is of homologous pattern and cockroaches have analogous pair of the leg. The ancestral Pax6 gene probably orchestrated the formation of a very simple eye — merely a collection of light-sensing cells working together to inform a primitive organism of when it was out in the open versus in the dark, or in the shade. On the contrary, they conclude: In summary, we identified the acquisition of splicing variations of Pax-6 in cephalopod eyes … and found that the acquisition occurred independently in vertebrates and cephalopods. Phylogenies Quiz. The answer is no. Body parts can be gained, lost, or rearranged depending on whether their function is the same as the original function of that part. Pax6 just had to wave its arms; the instrumentalists show up and make the music. Heather Scoville is a former medical researcher and current high school science teacher who writes science curriculum for online science courses. Firstly, octopus eyes and human eyes focus light on the retina in different ways. They are also from different ancestry, so they do not met up anywhere down the road. Structurally, that is the only difference between the eyes. It doesn’t sound compatible with unguided processes. They just happen to fill the flying niche in their locations. Campbell agrees that "the eye is the product of many genes working together." In fact, the octopus eye is superior to the human's in that it doesn't have a "blind spot." The same happened for the eyes of squids and humans. It occurs in the lineage that includes squid, cuttlefish, and octopus – the cephalopods. Ah well, for those who refuse to consider intelligent design, it’s a familiar song and dance. One of the popular theories, paranotal hypothesis, suggests that their wings developed from the paranotal lobe… Those similarities involve a particular master control gene, Pax6. Yet octopi and humans aren’t very related and are located far away from one another on the phylogenetic tree.Dolphins and sharks are another notable examples of analogous structures and convergent evolution. Today the legacy of that early Pax6 gene lives on in an incredible diversity of organisms, from birds and bees, to shellfish and whales, from squids to you and me. Identify the following pairs as homologous or analogous organs. When you consider that they, and their … Homologous structures: are body parts of organisms that have different functions but similar body structures that all derived from the same body part in a common ancestor. One analogous structure might have come into existence long ago, while the analogous match on another species may be relatively new. Ultimately it would be considered Macro-evolution as the many series of the eye's evolution (from all the way from a pigment spot eye with the Pax gene to a camera eye still containing the Pax gene) as well as the evolution from the common … The eye of the octopus and human resembles the same, this means they have evolved from the same origin. Strictly speaking, scientists have only found uncanny similarities in vertebrate and invertebrate camera eyes. How the insect flight evolved remains unclear. (i) Sweet potato and potato (ii) Eye of octopus and eye of mammals (iii) Thorns of Bougainvillaea and tendrils of Cucurbits (iv) Fore limbs of … The octopus is an extraordinary animal in many ways, but the eyes of this creature are especially incredible. In fact, the octopus eye is superior to the human eye in that it does not have a "blind spot". This means the Pax6 gene predates the evolutionary diversification of these lineages — during the Cambrian period, some 500m years ago. But some genes orchestrate the construction of the eye. Why the eye? Even though there are some differences between human and octopus eyes, each of the tissues such as eyelid, cornea, pupil, iris, ciliary muscle, lens, retina, and optic nerve/ganglion corresponds well to each other. Importantly, the cephalopod camera eye arose completely independently from ours. University. Great choice of analogous traits! The marvel of splicing is that it can be used to produce two different kinds of instructions from the same piece of RNA code. Cephalopod eye evolution was modulated by the acquisition of Pax-6 splicing variants, Behe’s New “Mousetrap” Book — The Fragility of Darwinism, Galápagos Finches — Some Contradictions Solved, Design Triangulation: My Thanksgiving Gift to All, Podcast with Michael Behe: “You Can’t Deny the Data Forever”, Look: On Thanksgiving, Be Grateful for the Intelligent Design of Your Eyes, Gonzalez Extends “Privileged Planet” Arguments, A Disappointing Decade for Human Evolution. https://pediaa.com/difference-between-homologous-and-analogous-structures Then, tens of millions of years later on the branch leading to cephalopods, it had to "create a camera eye" that is a wonder of nature in squids and octopus. For example, mammals such as a humans arm, bat wing, and whale flipper all consist of very similar bones. Bats, birds, insects, and pterosaurs all had wings. Shark and mouse eyes are homologous to one another. Cephalopods have a camera eye with the same features as the vertebrate camera eye. Master control; informational control; this corresponds pretty well with irreducible complexity and hierarchical organization, features of designed systems. u … Let’s see if this instance is clear (without assuming Darwinian theory, that is). The human eye is very similar in structure to the eye of the octopus. When Carolus Linnaeus first began classifying and naming species with taxonomy, the science of classification, he often grouped similar-looking species into similar groups. In keeping with their role in controlling the process of eye formation, these genes are called "master control genes". b.) Eyes of octopus and mammals is an example of convergent evolution . But think of the problems for Darwinian evolution: whatever that gene did in the Precambrian oceans (perhaps "orchestrating" a light-sensitive spot), it had to get an instant PhD in orchestration to manage the compound eyes in trilobites and other animals that suddenly appeared in the Cambrian explosion. Sometimes, these types of adaptations can change the structure of the individual. Other types of evolutionary evidence, such as DNA similarities, have proved this. Sharks and dolphins look very similar due to color, placement of their fins, and overall body shape. The last common ancestor of cephalopods and vertebrates existed more than 500m years ago. The eyes of humans and the eyes of octopi are very similar for the most part, with the only substantial difference being that the eye of an octopus doesn’t have a blind spot like the human eye does. It is more likely they came from two separate branches of the phylogenetic tree and may not be closely related at all. Cephalopods have a camera eye with the same features as the vertebrate camera eye. Wings are a popular adaptation for many animals. The human eye is very similar in structure to the eye of the octopus. Eye construction is more than just a "parts list" (although some genes work that way, generating single parts). The octopuses eye is said to be superior over a human eye because it does not have a "blind spot". For example, in their view, the human eye and the octopus eye are analogous organs. Both eyes are round and have the same structural traits. In fact, the octopus eye is superior to the human's in that it doesn't have a "blind spot." ;-) Eyes developed further along both lines of descent. Quiz Questions and answers from Bio 152 Phylogenies Quiz. Speciation is the change over time of one species into a new species. But then — without any possible cross-communication — another Pax6 gene on a completely separate branch leading to vertebrates had to learn to create a camera eye all over again.
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