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Evolutionary BiologyEvolutionary BiologyEvolutionary Thought ygbefore DarwinThe modern field of evolutionary biology can be traced back to Charles Darwin There were ideasCharles Darwin. There were ideas about biological change and interactions between organisms iDihifl dhiprior to Darwin that influenced his thinking. An understanding Darwin’s observations, motivations, hypotheses, tests, and conclusions rests on understanding his times and the thinking of day2his times and the thinking of day.Every culture has explanations for its origins: http://www.magictails.com/creationlinks.htmlExplanations that have a physical basis began with the Greeks:Thales (640-546 B.C.) - the first natural explanation. All life came from water. X h (576480 B C ) d H d t (484425 BC)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 and change in living creatures accompanying itand change in living creatures accompanying it.Democritus (500-404 B.C.) distinguished between organic and inorganic systems. Organic systems were derived from i i t th h th t l ti f3inorganic 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.and two basic forces. love and hate.A proper mixture created a functional living organism.An improper mixture resulted in reduced survival. The first example of a hypothesis of differential survival in natureexample 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 characteristics of the parent will be passed to the offspringcharacteristics 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 habits4Variation was due to differences in environments and habitsPlato (427-347 B.C.) believed that the universe had general laws that could be discerned through pure thought and be describedthat 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 ygobject Plato thought that underlying every object’s existence was its essence or essential natureessence, or essential nature. The variation among types of an object or types of organisms was an error, or just various degrees of imperfection from the true essential nature.5Plato 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 thoughtbe understood through pure thoughtThe Platonic system replaced naturalistic explanations.Nonnatural and natural explanationsNonnatural 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 potentially reject something that does not make predictions.potentially reject something that does not make predictions. Such explanations are outside the realm of science.6Aristotle (384-322 B.C.) The first great lidfPljdThe Great Chain of naturalist. - a student of Plato - rejected metaphysical speculation but accepted the idea that species have fixed properties.Being (scala naturae):HumansMlpppReturned to empiricism - studying by observing-and developed the beginningsMammalsBirdsReptilesobserving and developed the beginnings of biology: anatomy, reproductive biology and ecology of many plants and animals.ReptilesFishHigher InvertebratesHe was the first to use the gradations in form among organisms to arrange them gSimple AnimalsHigher Plantsinto a ladder like scale - with man at the top of the living world - a teleologicalsystemLower PlantsInanimate matter7system.Early Christians readily adopted Aristotle’sscala naturaeandEarly Christians readily adopted Aristotle s scala naturaeand viewed it as the product of a perfect creation - because it was perfect it was unchanging.During 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 physical S i l t d i t th t d f lifprocesses. Science was slow to spread into the study of life.81600s - 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 ofThey suggested that species can change through the actions of physical processes upon them.Voltaire (16941778)questioned the idea the species were fixedVoltaire (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 rank.rank.9George Louis Leclerc - “Comte de Buffon” - 1707-1788 -studied fossils-noted changes in organisms in the fossil recordstudied 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 f di t d it th t th th i fof sedimentary deposits, that the earth was in excess of 160,000 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


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NICHOLLS BIOL 370 - Evolutionary Biology

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