It is easy to say that species are constantly changing, and branching off into totally new species. But how do we know where the species originate? Phylogenies help to show us how all kinds of species are related to each other, and why. These relationships are put into what can be called a cladogram, which links species to common ancestors, in turn showing where, when, how, and why these ancestors diverged to form new species. Without phylogenies, it would be extremely difficult to put species in specific categories or relate them to one another. Along with phylogenies can come conflict on which species should be related to one another. This conflict causes many hypotheses and experiments, which can lead to phylogenetic retrofitting, which means adding some kind of data to a phylogeny that was not originally included. In M. S. Y. Lee’s article “Turtle origins: insights from phylogenetic retrofitting and molecular scaffolds”, the origin of the turtle (Testudines) is very controversial, and has been the source of experimenting to try to prove whether it should be placed under anapsid-grade parareptiles, according to Bayesian analyses, or diapsids as sisters to living archosaurs. The use of experiments including molecular scaffolding, which is an experiment involving using the scaffold protein of the backbone to place the turtles in a certain taxa, is used to show where turtles should actually be placed. I find it very interesting that scientists continue to go back and forth between new and old phylogenies, constantly rearranging and questioning the placement. Phylogenies are not just important for showcasing where species originated from, but also to illustrate how DNA sequences evolve as well. For example, in class, we t...
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...gly supported and implicated by this experiment. While Bayesian inference puts turtles in a wide range, parsimony puts turtles more specifically near pareiasauromorphs. Also, in molecular scaffolding, a turtle-archosaur clade in the diapsid matrices is very evident, but highly unstable for Eunotosaurus. Eunotosaurus, though, remains with parareptiles in a majority of the scaffolding. This states that turtles could very well be considered parareptiles, while being sister groups to archosaurs. Further evidence should be done on other close relatives to these taxa, including the research of synamorphies to help support the evidence. The more experiments that are applied to studying the different ancestors and possible sisters of turtles, and even Eunotosaurus, could be what it takes to properly place turtles in the specific phylogeny and taxa that they belong to.
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
Pianka, E. and Hodges, W. 1995. Horned Lizards. University of Texas. Web. Accessed at http://uts.cc.utexas.edu/~varanus/phryno.html
Shubin, N.H, Tabin, C., & Caroll, S. 2009. Deep homology and the origins of evolutionary novelty. Nature, 457: 818-823.
The second of Tinbergen’s questions Phylogeny looks at the evolutionary explanations of development, as opposed to just how behaviour has adapted, including mutations in response to environmental changes. Some of these mutations remain in species even after necessity has gone, and can influence future characteristics of that species. The third of Tinbergen’s questions looks at Causation,...
The species A. afarensis is one of the better known australopithecines, with regards to the number of samples attributed to the species. From speculations about their close relatives, the gorilla and chimpanzee, A. afarensis’ probable social structure can be presumed. The species was named by Johanson and Taieb in 1973. This discovery of a skeleton lead to a heated debate over the validity of the species. The species eventually was accepted by most researchers as a new species of australopithecine and a likely candidate for a human ancestor.
Biodiversity is the variation and amount of species across the globe, or within in a specific geographical habitat. There are three different areas of study within biodiversity; ecological diversity, species diversity and, genetic diversity. Science Book Species diversity is the variety of different organisms and relationships within a specific species, this essay will discuss the declining of species diversity among sea turtles and the implications it has on the worldwide seas. I have chosen to research about the topic because, sea turtles are believed to have been alive during the Jurassic period. However, now all seven sea turtle species are critically endangered or vulnerable, due to human activities such as; commercial fishing, bycatch and, climate change. (WWF, OCEANA, ACTIONBIOSCI)
The concept of transitional species is an important and complex notion in evolutionary biology. To begin with, there is no such thing as transitional species since all living things were always evolving in the past, not stopping at one stage or another, and they will continue to evolve in the future. In terms of evolutionary biology, we use the concept of transitional species as a way to dim ambiguity. Much like the use of the Linnean taxonomic system of species, we come up with concepts like transitional species to organize and classify species in order to understand their evolutionary roots and how those species changed through life’s history to become what they are today. “In the same way that the concept of species can be provisionally meaningful to describe organisms at a single point in time, the concept of transitional species can be provisionally meaningful to describe organisms over a length of time, usually quite a long time, such as hundreds of thousands or millions of years” (111). Though it can be difficult to distinguish what can be considered an ancestral species from another, the fossil record can show us how species change through time as they develop ways to adapt to stresses found in their environments. “In the modern sense, organisms or fossils that show intermediate stages between ancestral and that of the current state are referred to as transitional species” (222). The concept of transitional species is, in essence, fairly straight forward. This paper will outline the concept of transitional (or sometimes termed intermediate) species and the latter’s role in evolutionary biology, as well as go in depth about several common transitional species: Tiktaalik, an animal at the cusp between life in the water and ...
...e single origin perspective but not the multiregional perspective (1988). For example, the first appearance of Homo sapiens raises problems. The newest fossils of Homo sapiens were discovered in Africa while Europe, the Far East and Australia have the oldest fossils (Stringer & Andrew 1988). If there was one linearly evolving species we should see the oldest fossils in Africa. Also, Although Europe and southwest Asia have the most complete fossil record there is an absence of Neanderthal and modern Homo sapiens transitional fossils, which goes against the idea that species evolved together (Stringer & Andrew, 1988). The fossils better describe the single origin perspective.
The debate of whether dinosaurs were cold blooded or warm blooded has been ongoing since the beginning of the century. At the turn of the century scientists believed that dinosaurs had long limbs and were fairly slim, supporting the idea of a cold blooded reptile. Recently, however, the bone structure, number or predators to prey, and limb position have suggested a warm blooded species. In addition, the recent discovery of a fossilized dinosaur heart has supported the idea that dinosaurs were a warm blooded species. In this essay, I am going to give supporting evidence of dinosaurs being both warm and cold blooded. I will provide background information on the dinosaur that was discovered and what information it provides scientists.
...nder, C., Tsai, C., Wu, P., Speer, B. R., Rieboldt, S., & Smith, D. (1998/1999/2002). The permian period. Informally published manuscript, Biology 1B project for Section 115, University of California Museum of Paleontology, CA, Retrieved from http://www.ucmp.berkely.edu/permian/permian.php
Charles Darwin’s theory of natural selection explains the general laws by which any given species transforms into other varieties and species. Darwin extends the application of his theory to the entire hierarchy of classification and states that all forms of life have descended from one incredibly remote ancestor. The process of natural selection entails the divergence of character of specific varieties and the subsequent classification of once-related living forms as distinct entities on one or many levels of classification. The process occurs as a species varies slightly over the course of numerous generations. Through inheritance, natural selection preserves each variation that proves advantageous to that species in its present circumstances of living, which include its interaction with closely related species in the “struggle for existence” (Darwin 62).
With its abundance of genera, the Burgess Shale is one of the world’s most important fossil fields. It’s discovery in 1909 led to over 100 years of paleontological study in the Canadian Rockies, a majority of which has been carried out in two quarries known as the Walcott and Raymond quarries (Hagadorn, 2002). Though he was originally in search of trilobites in the Burgess Shale Formation, paleontologist Charles Walcott also discovered a diverse group of soft- and hard-bodied fossils, from algae and sponges to chordates and cirripeds (Hagadorn, 2002). Soft-bodied fossils are incredibly rare due to their delicate structure and susceptibility to decay, so it is hard-bodied fossils that more regularly occur in fossil findings. However over 75,000 soft-bodied specimens have been found in the Burgess Shale formation (Hagadorn, 2002). These specimens are preserved in layers of shale formed from deposits of fine mud. One of the most significant species discovered is the Pikaia gracilens. Believed to be an early chordate, the Pikaia gracilens existed very close to the beginning of the evolutionary path that ultimately lead to humans (McGraw-Hill Encyclopedia, 2006).
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.
Reptiles are vertebrate, or backboned animals constituting the class Reptilia and are characterized by a combination of features, none of which alone could separate all reptiles from all other animals.The characteristics of reptiles are numerous, therefore can not be explained in great detail in this report. In no special order, the characteristics of reptiles are: cold-bloodedness; the presence of lungs; direct development, without larval forms as in amphibians; a dry skin with scales but not feathers or hair; an amniote egg; internal fertilization; a three or four-chambered heart; two aortic arches (blood vessels) carrying blood from the heart to the body, unlike mammals and birds that only have one; a metanephric kidney; twelve pairs of cranial nerves; and skeletal features such as limbs with usually five clawed fingers or toes, at least two spinal bones associated with the pelvis, a single ball-and-socket connection at the head-neck joint instead of two, as in advanced amphibians and mammals, and an incomplete or complete partition along the roof of the mouth, separating the food and air passageways so that breathing can continue while food is being chewed. These and other traditional defining characteristics of reptiles have been subjected to considerable modification in recent times. The extinct flying reptiles, called pterosaurs or pterodactyls, are now thought to have been warm-blooded and covered with hair. Also, the dinosaurs are also now considered by many authorities to have been warm-blooded. The earliest known bird, archaeopteryx, is now regarded by many to have been a small dinosaur, despite its covering of feathers The extinct ancestors of the mammals, the therapsids, or mammallike reptiles, are also believed to have been warm-blooded and haired.
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.