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NICHOLLS BIOL 370 - Evolutionary Biology

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1Evolutionary BiologyEvolutionary Thought before DarwinThe modern field of evolutionary ybiology can be traced back to Charles Darwin. There were ideas about biological change and interactions between organisms prior to Darwin that influenced his thinking. An understanding 2Darwin’s observations, motivations, hypotheses, tests, and conclusions rests on understanding his times and the thinking of day.2Every culture has explanations for its origins: http://www.magictails.com/creationlinks.htmlExplanations that have a physical basis began with the Greeks:Thales (640546 B C )the first natural explanation All lifeThales (640-546 B.C.) -the first natural explanation. All life came from water. Xenophanes (576-480 B.C.) and Herodotus (484-425 BC) recognized fossils as the remains of living creatures. and based on the distribution of fossil marine life speculated that oceans had formerly covered some of the land.- the first recognition of environmental change through time 3gggand change in living creatures accompanying it.Democritus (500-404 B.C.) distinguished between organic and inorganic systems. Organic systems were derived from inorganic systems through the natural properties of inorganic systems.Empedocles (495-435 B.C.) gave a detailed explanation of the a natural origin of life. There were 4 basic inorganic materials : fire, air, earth, and waterand two basic forces. love and hate.A proper mixture created a functional living organismA proper mixture created a functional living organism.An improper mixture resulted in reduced survival. The first example of a hypothesis of differential survival in nature.Hippocrates (460-370 B.C.) stressed an empirical approach. He stated two principles that seemed to be valid.1. the inheritance of acquired characters - habits or 4qcharacteristics of the parent will be passed to the offspring2. principle of use and disuse - a part that is used will become more elaborate and a part that is not used will be lostVariation was due to differences in environments and habits3Plato (427-347 B.C.) believed that the universe had general laws that could be discerned through pure thought and be described. Plato developed many ideas about the nature of the universe. One that was very influential and still survives in some form today is ESSENTIALISM or IDEALISM.The form of an object or organism is an outward expression of its essence – an unseen underlying truth about the nature of an object Plato thought that underlying every object’s existence was its essence, or essential nature. Th i ti t f bj t t f i5The variation among types of an object or types of organisms was an error, or just various degrees of imperfection from the true essential nature.Plato also introduced the idea of an animate or living cosmos -all physical and living systems are linked together into a harmonious whole – a supernatural harmony that could only be understood through pure thoughtThe Platonic system replaced naturalistic explanationsThe Platonic system replaced naturalistic explanations.Nonnatural and natural explanations -natural explanations depend on physical cause and effect and often make testable predictions nonnatural explanations propose nonphysical causes and can’t make predictions that can be critically tested. We can’t 6pypotentially reject something that does not make predictions. Such explanations are outside the realm of science.4Aristotle (384-322 B.C.) The first great naturalist. - a student of Plato - rejected metaphysical speculation but accepted the idea that species have fixed properties.The Great Chain of Being (scala naturae):HumansMammalsReturned to empiricism - studying by observing - and developed the beginnings of biology: anatomy, reproductive biology and ecology of many plants and animals.He was the first to use the gradations in BirdsReptilesFishHigher InvertebratesSimple AnimalsHi h Pl t7form among organisms to arrange them into a ladder like scale - with man at the top of the living world - a teleologicalsystem.Higher PlantsLower PlantsInanimate matterEarly Christians readily adopted Aristotle’s scala naturae and viewed it as the product of a perfect creation - because it was perfect it was unchanging.i h iddl h A b i d h G k di iDuring the middle ages the Arabs carried on the Greek tradition of natural explanations for biological phenomena.The Christian church in Paris in 1209 banned any Arabic literature dealing with natural explanations.The Age of Enlightenment - (1650-1800) - Real science began to emerge with rational and testable explanations of physical8to emerge with rational and testable explanations of physical processes. Science was slow to spread into the study of life.51600s - Francis Bacon (England) and Renee Descartes (France) suggested that natural laws surpassed Christian dogma in the understanding and explanations of natural phenomena. They suggested that species can change through the actions of physical processes upon themphysical processes upon them.Voltaire (1694-1778) – questioned the idea the species were fixed quantities and stressed that there was variation within species He questioned the idea of a great chain of being with humans being the ultimate living things - this served to satisfy human egos. He saw living things as all part of a continuum of equal 9gggp qrank.George Louis Leclerc - “Comte de Buffon” - 1707-1788 -studied fossils - noted changes in organisms in the fossil record and involved both improvement and degeneration of parts.Calculated from rates of sedimentation, and from the thickness of sedimentary deposits, that the earth was in excess of 160 000 ldid hilid hi160,000 years old -viewed as a heretical idea at the time.Histoire Naturelle (1749) - all species have an internal mold and the mold organizes the body Similar species share a common ancestor and were modified by climate. Speculated about the inheritance of acquired characteristics.Original molds arose by spontaneous generation10Original molds arose by spontaneous generation.Archbishop James Ussher (1581-1656) - calculated from Biblical records that the earth was created 4004 BC, on Sunday October 23.6James Hutton (1726 - 1797) - observations of geology should be explained by processes that we observe in the present. -“Uniformitarianism”Uniformitarianism was later championed by Charles Lyell (1797-py y(1875) who had an important influence on Charles DarwinUniformitarianism is an important part of science


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