What is Evolution - Lecture Notes | Evolutionary Biology | BIOL 346, Study notes of Theory of Evolution

Download What is Evolution - Lecture Notes | Evolutionary Biology | BIOL 346 and more Study notes Theory of Evolution in PDF only on Docsity! Chapter 1 EVOLUTIONARY BIOLOGY WHAT IS EVOLUTION? The word evolution comes from the Latin word evolvere, which means to unfold or unroll. -To reveal the hidden potentialities. -It has come to mean “change”. Biological evolution refers to the change in the characteristics of groups of organisms over many generations, over time. The development or ontogeny of an individual organism is not considered evolution.  Individual organisms do not evolve.  Populations of organisms evolve; they undergo descent with modification. Changes that are passed from one generation to the next are considered evolutionary; these are genetic changes.  The resurgence of antibiotic resistant diseases is an example of natural selection. BEFORE DARWIN Darwin’s theory of biological evolution revolutionized the prevailing worldview in the West that had existed from the time of Plato and Aristotle. Plato, 428-348 B. C. Greek Philosopher. “Idea” or “form” is real and everything else is a reflection of this reality. The essence or idea is imperfectly imitated by its earthly representations. The real world is the world of ideas, and what we see on earth is only an imitation of those ideas. The essence or form of a structure could be understood from its function, since the function dictated the form. Species became the initial mold for all later replicates of that species.  Theory of essentialism. Aristotle, 384-322 B. C. Greek philosopher. Aristotle developed the Plato’s concept of immutable essence into the notion that species have fixed properties. Aristotle proposed that the last stage of development, the adult form, explains the changes that occur in the immature forms (teleological explanation); the advanced stages influence the earlier stages. He also proposed that all living forms are linked in a progression from imperfect to most perfect. He called this the Scale of Nature. Christian thought elaborated on Platonic and Aristotelian philosophy that existence is good and the God’s benevolence is complete, therefore, He must have bestowed existence on every creature giving each its own essence. Since order is superior to disorder, God’s creation must follow a plan, especially a gradation from imperfect to perfect.  Inanimate objects to plants to invertebrates up to vertebrates, human, and finally, angels.  Scala Naturae or Scale of Nature or the Great Chain of Being. The Principle of Plenitude The legacy of Plato to European thinking about the natural world has been expressed as the Principle of Plenitude (Lovejoy, 1936; Rolfe, 1985). This was the belief that all possible kinds of things exist in the world already and nothing more can be created. Aristotle's legacy was more complicated but has been summarized by Rolfe as the concept of continuity and gradation between adjacent kinds of being when hierarchically arranged (1985, p. 300). Together, the Principle of Plenitude and the Great Chain of Being led to the belief, from medieval times, that a continuous chain extended from the inanimate world of non-living matter, such as earth and stones, through the animate world of plants, zoophytes, and the lowest forms of animal life, upwards to the quadrupeds and eventually through Man to the realms of angels and finally to the Christian God. This belief also entailed the view that just as nothing new could be created; neither could anything be exterminated, since this would counteract the will of God (Rolfe, 1985, p. 10). http://www.findarticles.com/p/articles/mi_m2267/is_n3_v62/ai_17909868/pg_4 Aristotle, the Scale of Nature, and modern attitudes to animals - In the Company of Animals Social Research, Fall, 1995 by Juliet Clutton-Brock Linnaeus, Carolus. 1707-78, Swedish botanist and taxonomist, Linnaeus is considered the founder of the binomial system of nomenclature and the originator of modern scientific classification of plants and animals. He used the species as the basic unit in building his system upward to larger categories. He grouped related species into genera, and related genera into orders, and so on. In his mind, this species had been related in the mind of the Creator. Hutton, James. 1726-97, Scottish geologist. Hutton formulated controversial theories of the origin of the earth in 1785. He was of the opinion that the earth must be very old.  Uniformitarianism: the doctrine that past geological changes in the earth were brought about by the same causes as those now taking place. It stressed the slowness and gradualness of rates of change. Lyell, Sir Charles. 1797-1875, English geologist. Lyell argued in his book that, at the time, presently observable geological processes were adequate to explain geological history. He thought the action of the rain, sea, volcanoes and earthquakes explained the geological history of more ancient times. Lyell conclusively showed that the earth was very old and had changed its form slowly, mainly from conditions such as erosion. Lyell was able to date the ages of rocks by using fossils embedded in the stone as time indicators. Lyell helped win acceptance of James Hutton's theory of uniformitarianism and of Charles Darwin's theory of evolution. H.M.S. Beagle, under the command of Captain Robert Fitzroy, left for Patagonia, South America, in 1831 with Charles Darwin on board. At this time Charles did not believe in evolution, including his grandfather’s theory, as any evidence presented so far could not convince him. The Beagle reached South America in 1832 and Charles took care to observe the flora and fauna. Charles went then to Buenos Aries where he saw fossils of more ancient animals, including a mastodon. He experienced a violent earthquake in Chile that raised the land in some places between 2 and 10 feet. Darwin was most interested in the plants and animals on the Galápagos, a group of 16 large islands (and many smaller) off the coast of Ecuador.  Giant tortoises inhabit every one of the islands, which gave the island chain its name, from the Spanish Galápagos, meaning tortoise.  Each island has its own type of tortoise, distinguishable by the shape and pattern of its shell.  Darwin was astonished that the islanders felt that this was due to the difference in environment on each island.  Darwin also observed the finches, which varied in size and shape from island to island.  Their beaks also varied depending on which food they ate and some even had extra long tongues for grabbing certain types of foods such as insects, nuts or seeds. Island animals and plants were different to those on the mainland but a relationship could be seen. What was even stranger though, to Darwin, was the fact that organisms on different islands varied, but still seemed related. ALFRED RUSSEL WALLACE, 1823-1913.  8 January 1823: Alfred Russel Wallace born at Usk, Monmouthshire.  mid/late 1837: Joins the eldest brother William in Bedfordshire to learn the surveying trade.  25 April 1848: Wallace and Bates leave England for Amazonian South America to begin a natural history collecting expedition.  March 1854: Leaves England for the Far East to begin a natural history collecting expedition.  20 April 1854 to 20 February 1862: Collecting expedition in the Malay Archipelago.  February 1858: Writes 'On the Tendency of Varieties to Depart Indefinitely From the Original Type' and sends it off to Charles Darwin for comment.  1 July 1858: Wallace and Darwin's writings on natural selection are presented at a meeting of the Linnaean Society.  November 1859: “On the Zoological Geography of the Malay Archipelago,” the paper describing Wallace’s Line is read before the Linnaean Society; Darwin's “On the Origin of Species” is published.  1 April 1862: Returns to English soil.  7 November 1913: Dies at Old Orchard. "In February of 1858, while suffering from an attack of malaria in the Moluccas (it is not fully certain which island he was actually on, though either Gilolo or Ternate seems the likely candidate), Wallace suddenly, and rather unexpectedly, connected the ideas of Thomas Malthus on the limits to population growth to a mechanism that might insure long-term organic change. This was the concept of the "survival of the fittest," in which those individual organisms that are best adapted to their local surroundings are seen to have a better chance of surviving, and thus of differentially passing along their traits to progeny. Excited over his discovery, Wallace penned an essay on the subject as soon as he was well enough to do so, and sent it off to Darwin. He had begun a correspondence with Darwin two years earlier and knew that he was generally interested in "the species question"; perhaps Darwin would be kind enough to bring the work, titled 'On the Tendency of Varieties to Depart Indefinitely from the Original Type,' to the attention of Lyell? " http://www.wku.edu/~smithch/index1.htm DARWIN’S EVOLUTINARY THEORY Darwin’s evolutionary theory has two thesis: 1. Descent with modification: All living and extinct species have descend without interruption from one or several original forms of life. These new species accumulated changes over great expanse of time and now look different from one another. 2. Natural Selection: Useful variation will allow those organisms that possess them to survive and reproduce and pass these good variations to their offspring. DARWIN'S THEORY OF NATURAL SELECTION. Fact #1 - Without constraints, populations will grow exponentially, producing an ever more rapidly growing number of organisms. Fact #2 - In spite of this prediction, the numbers of individuals in a population remains near equilibrium, fluctuating above and below some mean value. Fact #3 - Resources are limited. From these three facts, Darwin concluded that there was a struggle for existence. Darwin combined this with two additional facts: Fact #4 - Individuals are unique. There is individual variation. This came from observing animal breeding. Fact #5 - Much, but not all, of the individual variation is heritable. This observation also came from animal breeders. Some of the observed variation is environmental, some is genetic. Conclusion: These facts led Darwin to the conclusion that some individuals are better equipped to survive and reproduce (Natural Selection) in their struggle for existence. Through many generations of time, evolution is the result. Darwin used "descent with modification." Mayer (1982) stated that Darwin’s Theory of Evolution included five theories: 1. Evolution as such: lineages of organisms change over time. 2. Common descent: all life can be represented as a single family tree where there is common ancestor to all species. 3. Gradualism: gradual changes produced new species; this is in contrast with saltation, the hypothesis that proposes that evolution occurs by sudden leaps. 4. Population change: evolution occurs due to the proportion of individuals in the population that inherit a given characteristic. 5. Natural selection: survival and reproduction. A big gap in Darwin’s theory was the lack of an explanation about the origin of the variations found in a population: where do these variations come from?  Darwin’s theory was a “variational theory” in which populations change due to survival reproduction and selection of certain genes.  Lamarck’s theory was a “transformational theory” in which the individual changes, is transformed, and then passes those traits to the offspring. Blending Inheritance. This was the prevailing hypothesis about the inheritance of traits.  Maternal and paternal contributions blend in the offspring.  As a result, a new adaptation will be diluted in successive generations and eventually disappear. Therefore, variation should decrease and not increase. Darwin never knew that Gregor Mendel had solved the problem of inheritance in a paper published in 1865. EVOLUTIONARY THEORIES AFTER DARWIN After Darwin’s theory was proposed in the 1850s there was period of substantial controversy and several theories were proposed, which included neo-lamarckism, orthogenetic and mutationists theories. A great deal of information was accumulated after the 1870 due to the work done in paleontology, comparative morphology and comparative embryology  Neo-Lamarckism: several theories based on the idea of the inheritance of acquired characteristics  Orthogenetic theory: evolution proceeds toward a predetermined goal and does not require natural selection. No mechanism was ever proposed for this theory.  Mutationist theory: geneticists observed that mutations arise and produce new variations in the population, therefore, natural selection was not necessary for evolution to occur; the mutants represent new species.