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 ...
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... as stated previously, the capacity that Archaeopteryx was able to fly is unclear.
Several models have been proposed to explain why might Archaeopteryx or its decedents develop the ability to fly. The “pouncing proavis” or “trees-down” model was proposed by J.P. Garner and colleagues in 1999. They theorize that birds evolved to the ability to fly by first living in trees and then gliding down to ambush prey. Natural selection favoured individuals that could glide the furthest to catch prey and eventually led to the origin of flight. Garner and colleagues (1999) believed that this theory explained three aspects of early flight: the model matches observed secession in flight evolution based on fossil records, it predicts a primitive bird-like animal had few adaptions to flapping but very complex aerodynamic feathers, and it explains the origin of rachis in feathers.
The four-pointed forkbird has the best suited evolutionary fitness. By the end of the activity, there were only two two-pointed forkbirds, one one-pointed forkbirds, and seventeen four-pointed forkbirds. This shows that four-pointed forkbirds have a better chance of surviving and passing on their traits.
Web. The Web. The Web. 11 February 2014 “Biology: Evolution”. The New York Public Library Science Desk Reference.
Paul, Gregory S. (2002). "Looking for the True Bird Ancestor". Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press. pp. 171–224. ISBN 0-8018-6763-0.
Many people once believed that pterosaurs were weak flyers, or at least the larger ones were. The idea was that they used their large wings to glide instead of flap like flying creatures. This is now known to be false. Pterosaurs were also thought to be dinosaurs with similar anatomical features. Studies have shown now though that since the pterosaurs were not flappers but active flyers, their hearts were similar to those of mammals with four chambers, needed for an active way of life, unlike reptiles. In the past century, pterosaurs fossils have been known to be found with fur, which leads scientists to believe that pterosaurs needed insulation to keep in heat which indicated pterosaurs were active like mammals and warm blooded. 1
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,...
Before tetrapods existed, all vertebrates were confined to living in aquatic habitats. The only animals that lived on land were arthropods. Through natural adaptations, the fish developed into amphibians. This colossal stage of change made necessary the evolution of new ways of breathing, locomotion, and reproduction. Paleontologists needed to understand how this transition took place. If the changes in anatomy of the fish developed on land, then they served the same purposes they serve today, such as walking. But what advantages would those same body parts give to the aquatic creatures still living in water? This is one of the questions the scientists are asking themselves. There have been a few hypotheses on this matter. The most recent one states that the transformations of the aquatic creatures happened underwater in order to help them survive. This time period is very difficult to study because there is a very small amount of fossils preserved. A...
The cursorial hypothesis postulate that Archaeopteryx were likely fast ground runners and generated thrust for lift off by flapping their wings. The hypothesis is supported by calculations from an aerodynamic model, suggesting that Archaeopteryx could run at 6 metres per second before takeoff (Burgers & Chiappe, 1999). Their bone structure also support that they were fast bipedal ground runners, as Archaeopteryx had a larger hind limb to body proportion and slender limb joints that allowed them to bend their knees with ease (Lucas, 2007). Their fast, bipedal running speed, agility, and ability for flight suggest that Archaeornithes were endothermic, as these energetically demanding tasks would not be possible without the high basal metabolic activity of an endotherm.
The debate among creationists and evolutionists as to the origin of modern life on Earth has pushed increasingly into the limelight over the last several years. Unfortunately, such mainstream coverage has caused many of the related issues to become skewed and misinterpreted. In the article “Five Major Misconceptions about Evolution,” Mark Isaak attempts to make clear the true nature of evolutionary theory so that, if it must be challenged, such arguments can be made on a purely factual basis rather than, as Isaak says, “against a set of misunderstandings that people are right to consider ludicrous” (“Misconceptions” Para. 1). He presents these misconceptions and his explanation of the faulty logic behind each one in five main categories: “Evolution has never been observed,” “Evolution violates the 2nd law of thermodynamics,” “There are no transitional fossils,” “The theory of evolution says that life originated, and evolution proceeds, by random chance,” and “Evolution is only a theory; it hasn't been proved” (“Misconceptions” Para. 2). In addressing each of these proposed falsehoods individually, Isaak forms an argument with few faults that is clear, precise, and effective.
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).
Vertebrates have two independent extentions of flight evolution. These two evolutionary markers are the aves, and chiroptera. The origin of flight led to two main theories that flight originated form the ground up or from the trees down. One theory does not explain both evolution in flight as it may be possible that the trees down theory supports Chiroptera or bat evolution. The other theory of ground up evolution could be the explanation for Aves or birds. Aves flight origin is believed to have began with the ancestor Archaeopteryx in the late Jurassic era. Chiroptera origin traces back to early Eocene period but a small fossil record is not helpful to establish their origin. Studies show that Skeletal and muscle structure differences could
In the past few decades, the hypothesis that birds evolved from dinosaurs has been widely accepted by many scientists because of fossil evidence. Now scientists are looking for ways to prove the origin of flight through extensive research of newly found fossils. The origin of flight has been debated between scientists for years, but without strong evidence, they have yet to come to a conclusion on the issue. The disagreement between the two sides is whether flight arose from creatures that lived in the trees or ones on the ground. A new discovery in western Liaoning, China shed some light on the debate and many scientists now conclude that flight evolved from creatures living in the trees.
Zacherl, Danielle. “Biology 171 Evolution and Biodiversity.” National Association of Research in Science Teaching 2007 Annual Meeting, New Orleans LA. (2007):n. page. Print.
Although modern evolutionists are thought to be divided on the issues surrounding evolutionary theory, a close look at the evidence suggests that both the gradualist school of thought and the punctuationist school of thought share many characteristics in common. This is especially true when evaluating their beliefs about the fossil record, disagreement with the theory of saltation, and the misinterpretation of the word “rapid” in terms of punctuationist theory. Although this may be the case, the two theories do diverge on one important point, the notion of periods of stasis, but when taken as a whole, the evidence suggests that punctuationism is not as radical as it has been hyped up to be.
...for more accurate predictions of how species will evolve and whether or not certain species will survive and what adaptations could promote or inhibit that process. There are different methods of adaptation available for animals and plants to employ in nature. Thus, exploring adaptations during our lectures would grant us better insight into what caused certain things to demonstrate specific adaptations and would aid in the explanation and expansion of convergent evolution.
Without evolution, and the constant ever changing environment, the complexity of living organisms would not be as it is. Evolution is defined as a process that results in heritable changes in a population spread over many generations (8).Scientists believe in the theory of evolution. This belief is based on scientific evidence that corroborates the theory of evolution. In Figure 1 the pictures of the skulls depict the sequence of the evolution of Homo-sapiens. As the figure shows, man has evolved from our common ancestor that is shared by homo-sapiens. The change of diet of homo-sapiens over time has thought to contribute to the change in jaw structure and overall skull shape.