Presentation on theme: "Historical Background to Darwin's Theory of Evolution"— Presentation transcript:
1Historical Background to Darwin's Theory of Evolution
2Evolution is the core theme of biology The 3 main beliefs about Origins
347% 40% 9% Creationist view: Theistic evolution: God created man pretty much in his present form at one time within the last 10,000 years47%40%Theistic evolution:Man has developed over millions of years from less advanced forms of life, but God guided this process, including man's creation.Naturalistic Evolution:Man has developed over millions of years from less advanced forms of life. God had no part in this process.9%
4Four Factors that limited the development of theory of evolution 1. Lack of knowledge on age of Earth2. The Concept of fixity of species3. Lack of scientific method4. Notion of separate creation for humans and animals
5Plato ( BC)Saw variations in plant and animal populations as imperfect representations of ideal formsOnly the perfect forms of organisms were real: idealism, essentialism philosophy
6Aristotle (384-322 BC) Plato’s student all living forms could be arranged on a scale of increasing complexity “scala naturae” (scale of nature)no vacancies and no mobility in this ladder of lifespecies are fixed, permanent, and do not evolve
7Bishop Ussher 1650 Earth is very young (based on Bible) 1st Day of creation: Sunday 23 October BC
8Carolus Linnaeus c. 1735Swedish physician and botanist: father of taxonomyHe believed that species were permanent creations, “God creates, Linnaeus arranges”Wanted to organize the “scale of nature”
9Georges Cuvier ( ):Founder of Paleontology (the study of fossils)Opposed evolution, thought that boundaries between fossil layers corresponded to catastrophic events such as floods or droughtsCatastrophism = Earth is young
10Natural Theology:saw the adaptation of organisms to their environment as evidence that the creator had designed each and every species for a particular purpose(based on Judeo-Christian culture)
11James Hutton:In 1795 suggested Gradualism, profound change is the cumulative product of slow but continuous processes
12Charles Lyell (1797-1875): Uniformitarianism Embellished Hutton’s gradualism, geological processes are so uniform that their rates and effects must balance out through timeEarth is very old
13Jean Baptiste Lamarck (1744-1829) Published a theory of evolution in 1809 (year Charles Darwin was born)Individuals can evolveBelieved that evolution responded to an organisms “felt needs”modifications acquired during a lifetime can be passed on to offspringno evidence for this Ex mice tails
14DARWIN 1809 -1885 Darwin trained to be a clergyman Beetlemania turned him into a naturalistLyell and Hutton made him rethink the age of the EarthGot a position as the Naturalist on a 5 year voyage
15Beagle Voyage (1831-1836) Naturalist aboard the Beagle Collected plant & Animal specimensTook Lyell’s Book on Geology with himVisited many places including Galapagos
16500 miles off coast of South America New Volcanic IslandsOrganisms migrated to Islands
18Developed idea’s on Evolution after the voyage. Didn’t recognize what he was seeingFinches and Tortoises
19DARWIN After the Voyage Darwin developed his theory of Natural SelectionWhat inspired him?Hutton - GradualismLyell - Earth is OldFarmers/Animal Breeder - Variation in populationsMalthus - Populations grow rapidily- Not enough resources for all offspring
20All populations have variation Darwin knew many farmers and animal breeders. From them and his own research he knew all individuals in a population are different.
21DARWIN reads Malthus 1838In 1838, Darwin reads for amusement Malthus’s book Population.In nature, animals and plants produce more offspring than can survive.This leads to a struggle for existence.Darwin see that favourable variations in a population would tend to be preserved, and unfavourable ones to be destroyed.He at last has a theory by which to work.
22Darwin publishes the Origin of Species:1865 Didn’t publish is ideas for 20 years!!! Why?Wallace comes up with the idea of Natural Selection independently of Darwin.Forces Darwin to finally publish his book on Evolution
23Darwin’s Five major theories of Evolution 1. The nonconstancy of species (species can evolve)2. The descent of all organisms from common ancestors (branching evolution)3. The gradualness of evolution (evolution takes time)4. The multiplication of species (speciation: formation of new species)5. Natural selection (the mechanism of evolution)
24Darwin’s Explanatory Model of Natural Selection Fact - #1Every population has such high fertility that its size would increase exponentially if not constrained. (source: Malthus)
25Fact - #2The size of populations, except for temporary annual fluctuations, remain stable over time. (source: observation)
26Fact - #3The resources available to every species are limited (source: observation & Maltus)Inference 1. There is intense competition (struggle for existence) among the members of a species.
27Fact - #4No two individuals of a population are exactly the same: (source: animal breeders & taxonomists)Inference 2. Individuals of a population differ from each other in the probability of survival
28Fact - #5Many of the differences among the individuals of a population are, at least in part, heritable. (source: animal breeders)Inference 3. Natural selection, continued over many generations, results in evolution.
29To sum up: Populations evolve, not individuals. Every species produces vastly more offspring than can survive from generation to generationAll individuals of a population differ genetically from each other.They are exposed to the adversity of the environment, and almost all of them perish or fail to reproduce.Only a few of them (on average two per set of parents) survive and reproduce.There survival is not random, but is aided by the possession of certain attributes that favor survival
30Truth or Misconception? 4/15/2017Truth or Misconception?Evolution has a plan for usHumans are the pinnacle of EvolutionSpecies evolve by choiceHumans have finished evolvingNatural selection causes changes in an organismChanges in your physical character's an individuals life will be passed on to your offspring
31Truth or Misconception? (cont.) Evolution is concerned with the good of the individualEvolution is concerned with the good of the speciesNatural selection picks organisms that are best adapted to their environmentHumans are better adapted than DolphinsSurvival of the fittest: Lions are fitter than zebrasEvolution is the creation of new speciesAn Elk with bigger antlers is fitter than the one with smaller antlers
321. Organisms reproduce like organisms 2. In most species only a small percentage of the offspring will actually survive to reproduce3. There are variations in individuals in a given population & these variations can be passed on.4. Whether an individual will survive to breed depend upon the interaction between the organism, other organisms & the environment.Some variations will be favorable. These variations will become more common from one generation to the next.5. Given time natural selection will lead to different groups of organisms (speciation)nn