Evolution

Evolution

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  Evolution Submitted by: Nikko DaveFrancisco III-1
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  Introduction to Evolution Humanshave undergone major anatomical changes over the course of evolution. This illustration depicts Australopithecus afarensis (center), the earliest of the three species; Homo erectus (left), an intermediate species; and Homo sapiens (right), a modern human. H. erectus and modern humans are much taller than A. afarensis and have flatter faces and much larger brains. Modern humans have a larger brain than H. erectus and an almost flat face beneath the front of the braincase.
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  Before Darwin Georges Cuever(1769-1832) French vertebrate zoologist, comparative anatomist and paleontologist names as the "Father of Comparative Anatomy and Paleontology“ proposed fixity of species and catastrophism
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  Fixity of Species -no changes occured in the structure of species due to adaptation - unable to adapt will result to extinction of the species Catasrophism - belief that periods of catastrophic extinction occured - after the mass extinction, repopulation of surviving species took place, giving the appearance of change through time
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  Jean Baptiste deLamarck (1744-1829) French invertebrate zoologist and botanist proposed the theory of inheritance of acquired characteristics
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  Theory of Inheritanceof Acquired Characteristics - belief that characteristics acquired during the lifetime of an organism can be passed on to the offspring - classic example he used to explain this theory was the long neck of giraffe - he believed that the long neck of giraffe developed over time because previous generations that stretched their necks to reach food high in trees passed on their long necks to their offspring - this theory was rejected because phenotypic changes acquired during an organism's lifetime do not results in genetic changes that can be passed on the next generations
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  Darwinism the explanation ofevolution proposed by Charles Darwin in his book The Origin of Species by means of Natural Selection (1859)
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  Charles Darwin(1809-1882) British naturalist bornon February 12, 1809 at Shrewsbury, England finished a BA degree in 1831 joined a 5-year voyage of the HMS Beagle (1831) as naturalist to study the geology and biology of the journey published several books such as Zoology of the Beagle (1840), The Structure and Distribution of Coral Reefs (1842), Geological Observations on Volcanic Islands (1844), The Origin of Species by means of Natural Selection (1859), The Descent of Man (1871) proposed and formulated the process of evolution in his book The Origin of Species by means of Natural Selection
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  Concepts of Evolution Thecharacteristics of living things change with time. Change in the characteristics of population over the course of many generations. The change is directed by natural selection process. Changes are in the genetic makeup of the population.
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  Evidences of Evolution fossil- a record of the history of life that shows that organisms have changed over time biogeography - the study of the distribution of life forms shows that organisms evolve in one locale and then spread to other regions comparative anatomy - related organisms share a unity of plan e.g. all vertebrate forelimbs contain the same sets of bones despite a similar functions comparative embryology - related organisms developed similarly, all vertebrates at some time have paired pharyngeal pouches bordering gill clefts, yet only fishes and amphibian larvae have gill comparative biochemistry - almost all living things use the same basic biochemical molecules, including DNA, ATP, and many identical or nearly identical enzymes
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  Organic Evolution defined aschange in genetics of a population over time (generations) a population refers to all individuals of the same species living in a defined area at the same time can be studied at two different levels: microevolution, which refers to small-scale genetic changes within populations macroevolution, which refers to the large-scale results of genetic changes in population, including the formation of new species and the evolution of large scale trends seen across species in what traits they have
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  Microevolution - occurs throughseveral mechanisms - the first of these that was discovered, and the form which is best known, is natural selection by Charles Darwin and Alfred Russel Wallace - natural selection is evolution that occurs because individuals with some traits survive and reproduce better than do individuals with other traits - as a result, those traits that result in high survival and reproduction are passed from generation to generation, through reproduction, at a higher rate than other traits - these traits become increasingly more and more common in populations - fitness refers to the degree to which individuals with certain traits are expected to survive and reproduce - natural selection can also be said to occur because of difference in fitness within a population - adaptation refers either to the process of natural selection, or to a trait that has evolved through natural selection - there are four properties of a population called as "Darwin's Four Postulates" that, together, result in natural selection; these are: 1. more young are produced each generation that can survive to reproduce; this is generally observed in species; many of the offspring born to any generation die before reproduction 2. individuals in a population vary in their characteristics; this is also generally observed in species; individuals are not identical to one another 3. the differences among individuals are based on genetic differences; the genetic basis for many traits in natural populations and often have observed that the differences among individuals are present because of genetic differences 4. individuals with some characteristics survive and reproduce better (have higher fitness) than do individuals with other characteristics; this has now been observed in hundreds of populations - if these four postulates are all true of a population, they result in natural selection - those individuals with higher fitness end up being the ones who survive each generation, and as a result reproduce more - since the traits are genetic, they get passed on to the next generation, and therefore become more common than they were in the previous generation
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  Macroevolution - evolution withinpopulations (microevolution) can occur through several other mechanisms - speciation refers to the formation of new species; it occurs when one ancestral species evolves into more than one (typically two) descendant species - species are typically defined as groups of organisms that are so similar to each other that they can reproduce and produce healthy fertile offspring - the idea is that if organisms belong to the same species then they can reproduce and their offspring can also survive and reproduce - if organisms belong to different species, they can't reproduce with each other or, if they do, their offspring die or are sterile - since speciation occurs when one species evolves into more than one new species, it increases the number of species that exist
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  Natural Selection the mechanismfor evolution proposed by Charles Darwin and Alfred Wallace in 1858 caused by environmental selection of organism most fit to reproduce, resulting in adaptation
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  Preconditions of NaturalSelection The members of the population must have heritable variations. After each generation, in the population, more individuals are produced than can survive and reproduce. Some individual possessed adaptive characteristics giving them greater chances of survival than any other individuals.
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  Results of NaturalSelection Advance body organization and improve species. Preserve and accumulate small-inherited modifications that are profitable for the species. The favored form increases in number and generally the less favored decreases and become rare.
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  Summary Evolution is aslow process of change by which organisms have acquired their distinguishing characteristics. It has been going on since the Earth was formed billions of years ago. The theories of evolution are Lamarck's Theory of Acquired Inheritance and Darwin's Theory of Natural Selection. Natural Selection as proposed by Darwin was the mechanism for evolution.