WHAT IS EVOLUTION

Birds evolution

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Natural Selection

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Natural selection is treated as the primary—and by some scientists the sole—mechanism producing evolutionary change. In essence it involves the process whereby some aspect of an organism’s environment (either climate, competition, predation, or parasitism) inter-acts with one or more traits of the organism, such that the survival or reproduction of that organism is enhanced (or diminished) relative to organisms that lack those traits. Natural selection is intimately tied to the phenomenon of adaptation: adaptations are honed by natural selection; over time the proportion of organisms with these adaptations will increase in a population because of natural selection.

Natural selection is associated with the idea that nature is red in tooth and claw, the implication being that there is a fierce competitive struggle among all organisms, with natural selection weeding out those less fit organisms while favoring those that are more fit.

What would Darwin say to today's creationists?

2012-09-29T13:45:00.001-07:00

Evolution evidences ( Morphological Similarity)

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Very suggestive evidence for common descent is also provided by the study of comparative anatomy. It was customary already in the eighteenth century to call certain organisms "related" when they were similar. At that time the French naturalist Comte Buffon described this for horses, donkeys, and zebras. The less similar that two kinds of organisms were, the less closely they were considered to be "related." The systematists, the students of classification, used the degree of similarity to establish a hierarchy of taxonomic categories. The most similar organisms were placed in the same species. Similar species were placed in the same genus, similar genera in the same family, and thus all the way up to the taxa of the highest category. This arrangement of organisms by the degree of their similarity and relationship is called the Linnaean hierarchy , after the Swedish botanist Carolus Linnaeus, who developed the system of binomial classification. Such a classification groups organisms into larger and larger taxa, finally comprising all the animals and all the plants. Beginning with a particular species, let us say the cat, one was able to construct this hierarchy. It was known that there were other species of cats rather similar to the house cat, which Linnaeus also placed in the genus Felts. This group of cats could be combined with the lion, the cheetah, and other genera of cats into the family Felidae. This family of catlike mammals could then be combined with other predatory mammals such as the Canidae (doglike), Ursidae (bears), Mustelidae (weasels), Viverridae (civets), and related groups into the order of Carnivora. In a similar manner, other mammals could be combined into the orders of Artiodactyla (deer and relatives), Perissodactyla (horses, etc.), Rodentia (rodents, etc.), and those of whales, bats, primates, marsupials, and so on to form the class Mammalia (mammals). A similar hierarchy exists for all other kinds of animals, such as birds and insects, and for plants. The nature and causation of this grouping, unless ascribed to creation, was a complete riddle until Darwin showed that it was evidently due to "common descent." Each taxon (group of organisms), Darwin demonstrated, could be explained as consisting of the descendants from the nearest common ancestor, and such descent required evolution.

The Linnaean hierarchy. Each category is nested within the next higher category,

such as the species in the genus.

E.Mayer

Evolution evidences (The Fossil Record)

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The most convincing evidence for the occurrence of evolution is the discovery of extinct organisms in older geological strata. Some of the remnants of the biota that lived at a given geological period in the past are embedded as fossils in the strata laid down at that period. Each earlier stratum contains the ancestors of biota fossilized in the succeeding stratum. The fossils found in the most recent strata are often very similar to still living species or, in some cases, even indistinguishable. The older the strata are in which a fossil is found—that is, the further back in time—the more different the fossil will be from living representatives. Darwin reasoned that this is to be expected if the fauna and flora of the earlier strata had gradually evolved into their descendants in the later, more recent strata.

Given the fact of evolution, one would expect the fossils to document a gradual steady change from ancestral forms to the descendants. But this is not what the paleontologist finds. Instead, he or she finds gaps in just about every phyletic series. New types often appear quite suddenly, and their immediate ancestors are absent in the earlier geological strata. The discovery of unbroken series of species changing gradually into descending species is very rare. Indeed the fossil record is one of discontinuities, seemingly documenting jumps (saltations) from one type of organism to a different type.

Transitional forms in evolution of the whale are illustrated by Hans Thewissen’s discovery of fossils of the Ambulocetus from 47 million years ago.

E.Mayer

The Giant Tortoises Of Galapagos

2012-08-25T07:35:00.002-07:00

What is Creationism

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Creationism is the belief that evolutionary science is wrong and that the history of the Earth and life can be explained only by numerous miracles. There is a range of beliefs ranging from the most extreme forms of creationism to evolutionary science:

• Young-Earth creationists insist that the universe and all its components were created recently by God and the entire fossil record was produced by a single flood, the Deluge of Noah.

• Old-Earth creationists believe that the Earth is old but that life-forms were created miraculously throughout the history of the Earth.

• Theistic evolutionists accept the general outline of the evolutionary history of life on Earth but believe that God intervened miraculously, perhaps subtly, in the evolutionary process.

• Deists believe that God set the natural laws in motion at the beginning and has not physically acted upon the universe since that time. Deism, in terms of scientific evidence, cannot be distinguished from evolutionary science, except perhaps in cosmology (see universe, origin of).

In the review that follows, the young-Earth definition is used. Creationism consists of a creationist theology, in which the Christian Bible is interpreted literalistically, and “creation science,” in which scientific information is presented to support those literalistic Bible interpretations.

Although many evolutionary scientists believe in God (see essay, “Can an Evolutionary Scientist Be Religious?”), evolutionary science operates under the assumption that God,

if God exists, has not influenced the processes that are being studied.

What is Origin of species

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In 1859, On The Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life, the English naturalist Charles Darwin (1809-1882) explains his theory of evolution. His proof is based on two observations. All living beings, he says, are likely accidental individual variations related to the use or non-use of any organ or external conditions (climate, food, etc..) In which they are placed . At the same time, the multiplication of species on the surface of the earth causes a struggle for existence. Therefore ensures Darwin, individuals have variations that give them an advantage in this fight and they will transmit to their offspring. This is what he called natural selection. The action of the latter over a long period allows divergence of character and thus the formation of new species. Conversely, natural selection determines the extinction of the less improved forms. In many cases, sexual selection, which ensures the best adapted males a larger number of offspring is added to it. Darwinian theory, constantly reworked, still constitutes the general framework of the research conducted by biologists.

Universalis Encyclopedia

Darwin's Dangerous Idea

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DARWIN & DARWINISM

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Charles Darwin was born on February 12,1809, the second son of a physician in a small English country town (Fig. 1.2). From his boyhood on, he was an ardent naturalist, particularly passionate about beetles. At his father's wish, he studied medicine in Edinburgh for a while, but was so appalled, particularly by the operations, that he soon gave it up. The family then decided he should study for the ministry, and this seemed a perfectly natural education for a young naturalist, for nearly all leading naturalists of his time were ordained ministers. Although Darwin conscientiously did all the required reading in the classics and in theology, it was really natural history that he pursued with single-minded devotion. After obtaining his degree at Cambridge University (Christ College), he received through one of his teachers at Cambridge the invitation to join one of the Navy's survey ships, HMS Beagle, for a survey of the coasts of South America, particularly the harbors. The Beagle left England at the end of December 1831. On the five-year cruise of the Beagle, Darwin shared a cabin with the commander, Captain Robert Fitzroy. While the ship surveyed the coast of Patagonia in the east, the Strait of Magellan, and parts of the western coast and adjacent islands, Darwin had abundant opportunity to explore the mainland and the biota of the islands. Throughout the trip, he not only made significant collections of natural history specimens, but more importantly he asked endless questions about the history of the land and its fauna and flora. This was the foundation on which his evolutionary ideas grew.

After his return to England in October 1836, he devoted his time to the scientific study of his collections and to the publication of scientific reports, at first on some of his geological observations.

After a few years, he married his cousin Emma, the daughter of the famous potter Wedgwood, bought a house near London (Down House), and lived there until his death on April 19,1882, at the age of 73. It was at Down House that he wrote all of his major papers and books.

What made Darwin such a great scientist and intellectual innovator? He was a superb observer, endowed with an insatiable curiosity. He never took anything for granted but always asked why and how. Why is the fauna of islands so different from that of the nearest mainland? How do species originate? Why are the fossils of Patagonia basically so similar to Patagonia's living biota? Why does each island in an archipelago have its own endemic species and yet they are all much more similar to each other than to related species in more distant areas? It was this ability to observe interesting facts and to ask the appropriate questions about them that permitted him to make so many scientific discoveries and to develop so many highly original concepts.

Darwin also saw clearly that there are two aspects of evolution. One is the "upward" movement of a phyletic lineage, its gradual change from an ancestral to a derived condition. This is referred to as anagenesis. The other consists of the splitting of evolutionary lineages or, more broadly, of the origin of new branches (clades) of the phylogenetic tree. This process of the origin of biodiversity is called cladogenesis. It always begins with an event of speciation, but the new clade may become, in time, an important branch of the phylogenetic tree by diverging increasingly from the ancestral type.
The study of cladogenesis is one of the major concerns of macroevolutionary research. Anagenesis and cladogenesis are largely independent processes (Mayr 1991). Already in the 1860s knowledgeable biologists and geologists accepted that evolution was a fact, but Darwin's explanations of the how and why of evolution faced protracted opposition.
E.Mayer

EVOLUTION

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Everything on this Earth seems to be in a continuous flux. There are highly regular changes. The change from day to night and back again, caused by the rotation of the Earth, is such a regular cyclical change. So are the changes of the sea level in the tides, caused by the lunar cycle. Even more pervasive are the seasonal changes due to the annual circling of the Earth around the sun. Other changes are irregular, such as the movements of the tectonic plates, the severity of the winter from year to year, or aperiodic climatic changes (El Nino, ice ages), as well as periods of prosperity in a given nation's economy. Irregular changes are largely unpredictable, being subject to various stochastic processes.

There is, however, one particular kind of change that seems to keep going continuously and to have a directional component. This change is referred to as evolution. The first widespread feeling that the world was not static as implied by the story of Creation, but rather was evolving, can be traced to the eighteenth century.

Eventually it was realized that the static scala naturae could be converted into a kind of biological escalator, leading from the lowest organisms to ever higher ones and finally to man. Just as gradual change in the development of an individual organism leads from the fertilized egg to the fully adult individual, so it was thought that the organic world as a whole moved from the simplest organisms to ever more complex ones, culminating in man.. Evolution, one said, consists of a change from the simple to the complex and from the lower to the higher. Evolution, indeed, was change, but it

seemed to be a directional change, a change toward ever greater perfection, as it was said at that time, not a cyclical change like the seasons of the year or an irregular change like the ice ages or the weather.

Evolutionary thinking spread throughout the second half of the eighteenth and the first half of the nineteenth century, not only in biology but in linguistics, philosophy, sociology, economics, and other branches of thought. Yet, on the whole, in science it remained for a long time a minority view. The actual shift from the

belief in a static worldview to evolutionism was caused by the dramatic event of the publication of Charles Darwin's On the Origin of Species on the 24th of November in 1859.

LAMARCKISM

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The naturalist Jean-Baptiste de Lamarck had proposed in 1809 a full-fledged evolutionary theory, a more or less biblical worldview prevailed up to 1859, not only among people but also among natural scientists and philosophers. It provided a simple answer to all questions about the world: God had created it and he had designed his created world so wisely that every organism was perfecdy adapted to its place in nature.

A constant world of short duration (Creationism)

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This was, of course, the Christian view, as presented in the Bible.

It was the prevailing view of the Western world in the Middle Ages and up to the middle of the nineteenth century. It was based on a belief in a supreme being, an all-powerful God, who had created the entire world as well as the human species, as described in the two stories of creation in the Bible (Genesis).

The belief that the world was created by an Almighty God is called creationism. Most of those who hold this belief also believe that God designed his creation so wisely that all animals and plants are perfectly adapted to each other and to their environment. Everything in the world today is still as it was when it was created.

This was an entirely logical conclusion based on the known facts at the time the Bible was written. Some theologians, on the basis of the biblical genealogy, calculated that the world was quite recent, having been created in 4004 B.C., that is, about 6,000 years ago.

The beliefs of creationism are in conflict with the findings of science, and this has resulted in a controversy between creationists and evolutionists.

E.Mayer

A world of infinite duration

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The Greek philosopher Aristotle believed that the world had always been in existence. Some philosophers thought that this eternal world had never changed, that it was constant; others thought that it was going through different stages ("cycling") but would ultimately always return to an earlier stage. However, such belief in an infinite age of the world was never very popular. Thereseems to have been an urge to account for a beginning.