Convergent evolution is the process in which organisms which are not closely related derive akin traits separately due to the need for adaptation to similar environments or ecological niches. According to the neo-Darwinian view, species with similar environmental living settings experience similar selection pressures. Natural selection then acts on the arbitrary changes or current genetic variability leading to identical phenotypic solutions. There may be resemblances at a phylogenetic level, but the basic DNA sequences are different. Convergent evolution gives rise to characteristics which are referred to as “analogous structures”. They are often contradicted with “homologous structures” which have the same ancestors. Convergent evolution …show more content…
They have all separately evolved wings from forelimbs for flight. Passive flight also known as gliding, has developed individually in squirrels, flying snakes, “flying” fish, , marsupial mammals, tree frogs and lizards. The first gliding mammal, Volaticotherium antiquius was discovered as a 125 million year old fossil in China. It is the only advocate of its order. Although it shared the same phylogeny as the flying squirrel, it was not the flying squirrel’s ancestor. 100 million years back, the Pangea, the supercontinent, split into current continents. Australia broke off from the Old World about 135 million years and South Africa broke off from Africa. The evolution of mammals in the separated continents began and followed similar patterns. This lead to numerous species emerging in Australia which had morphological similarities to those in the Old World. These can be observed between koalas and bears, sugar gliders and flying squirrels. Hence this is evidence that mammals began exploring flight around the same time as the birds …show more content…
There are two types of flightless birds. One is the giant flightless vegetarian bird and the other is the giant flightless carnivorous bird. This form evolved separately on a number of continents and the bigger islands. The Asian ostriches, Australian emus, South American rheas, New Zealand moas and giant “elephant birds” of Madagascar each evolved separately from rail ancestors. As for the giant flightless carnivorous birds, flightless “terror birds” from South America merged with marsupial “cats” as the dominant predators on the secluded continent. These birds were 10 feet tall and look like a smaller version of the T-rexes. North America then separately evolved its individual terror bird,
Ceratopsians and Pachycephalosaurs Around 144 million years ago, began the emergence of the Ornithischian dinosaurs during the Cretaceous period and diversified into North America and Asia. Ornithischians were classified as having a hip structure similar to that of birds, although they are not the descendants of birds. Marginocephalians, meaning "fringed heads" are a group of Ornithischians that have a distinctive skull structure, consisting of a slight shelf or bony frill on the back of the skull, a unique palate, and a short hip structure. These herbivores include two major groups: the Ceratopsians and the Pachcephalosaurians. These plant-eaters include the Ceratopsians, horned dinosaurs such as the Triceratops, Styrachosaurus, Pentaceratops, and the Protoceratops.
The idea of independence from Great Britain, it is something that is so commonplace a thing that I think very little of it on a day-to-day basis, but there was once a time when it was not so common, there was even a time when many thought the idea of fighting for independence was a foolhardy or reckless move and we were better off under the rule of Great Britain. This was not necessarily an incorrect way of thinking as Great Britain had provided the colonies with resources that would have taken far longer to develop for themselves. In 1776, Thomas Paine wrote Common Sense a pamphlet that encouraged this new way of thinking and urged the people of the thirteen colonies to fight for their independence from Great Britain, as their help was now seeming to become a hindrance.
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.
In Mivart’s Genesis of Species, the author highlights the inconsistencies of Darwin’s natural selection theory. He supports his assertion by emphasizing how species placed in similar environments acquire different traits, questioning the long-term advantages of these evolved traits, and noting the logical inconsistencies of how traits can span in all directions.
Biological evolution is a change in the characteristics of living organisms over generations (Scott, 2017). A basic mechanism of evolution, the genetic drift, and mutation is natural selection. According to Darwin's theory of evolution, natural selection is a process in nature in which only the organisms best adapted to their environmental surroundings have a higher chance of surviving and transmitting their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated. There has been many experimental research projects that relate to the topic of natural selection and evolution.
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).
According to Darwin and his theory on evolution, organisms are presented with nature’s challenge of environmental change. Those that possess the characteristics of adapting to such challenges are successful in leaving their genes behind and ensuring that their lineage will continue. It is natural selection, where nature can perform tiny to mass sporadic experiments on its organisms, and the results can be interesting from extinction to significant changes within a species.
Fossil evidence suggests that the Cathartid (New World) vultures have been around for quite some time with two fossil species dated from the early Oligocene (about 35 million years ago). During the Pliocene and Pleistocene (about 2 million years ago) th...
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.
Fossils of similar prehistoric animals were found on widely separated continents. This information was completely dismissed by the scientific community, yet supports the theory that the continents were once connected. Fossils of the Kannemeyeria and Labyrinthodont, land-dwelling animals, were discovered in North America, South America, Africa, Antarctica, Australia, and Eurasia. The Kannemeyeria and Labyrinthodont were creatures incapable of swimming long distances like those that now exist between the continents. Therefore it was nearly impossible for these creatures to travel across the bodies of water to reach the other continents. Migration patterns of the Kannemeyeria and Labyrinthodont align across the continents when fitting them together. When the continents were once one, creatures including Kannemeyeria and Labyrinthodont could travel across the continents without crossing a waterway.
Evolution is the theory that all living forms came from ancient ancestors and is the natural process to improve a species chance of survival. Through a series of mutations, genetic drift, migration, and natural selection today’s descendants show an amazing amount of similarities and diversity. Evolution on a small scale is called microevolution, an example being the
Many scientists in the past, such as Aristotle and Plato, believed that there were no changes in populations; however, other scientists, such as Darwin and Wallace, arose and argued that species inherit heritable traits from common ancestors and environmental forces drives out certain heritable traits that makes the species better suited to survive or be more “fit” for that environment. Therefore, species do change over a period of time and they were able to support their theory by showing that evolution does occur. There were four basic mechanisms of evolution in their theory: mutation, migration, genetic drift, and natural selection. Natural selection is the gradual process by which heritable traits that makes it more likely for an organism to survive and successfully reproduce increases, whereas there is a decline in those who do have those beneficial heritable traits (Natural Selection). For example, there is a decrease in rain which causes a drought in the finches’ environment. The seeds in the finches’ environment would not be soft enough for the smaller and weaker beak finches to break; therefore, they cannot compete with the larger and stronger beak finches for food. The larger and stronger beak finches has a heritable trait that helps them survive and reproduce better than others for that particular environment which makes them categorized under natural selection (Freeman, 2002).
The evolutionary journey begins on the island of Zealandia, where penguins were first able to swim freely. At the end of the Cretaceous period, Zealandia began to drift northeast and slowly isolated plants and animals along with it. The island eventually started to sink and its shores were flooded. Many marine and terrestrial animals perished but penguins found themselves without any predators around. Soon they were able to explore new areas and new climate zones.
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.
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.