Lìfe

生命的省思 周成功 陽明大學生命科學系 ckchou@mail.pmf.org.tw 生命是什麼？ 地球生命的起源 ? • 來自外太空 ? • 發生於地球 ? • 無論發生地何在，問題仍舊一樣 – 「生命如何開始？」 – 「細胞的資訊系統如何形成？」 Stanley Miller and origin of life Harold Urey 1950 The building blocks of life can be formed from inanimate environment ！ What is life? E Schrondinger, 1943 • Highly organized structure – How to combat the tendency of increasing entropy in the life system? • Inherited genetic information – How to precisely copy the genetic information from generation to generation? “Postage stamp collection” By Ernest Rutherford “A mature physicist, acquainting himself for the first time with biology, is puzzled by the circumstance that there are no ‘absolute phenomenon’ in biology Everything is timebound and space-bound The animal or plant or micro-organism he is working with is but a link in an evolutionary chain of changing forms, none of which has any permanent validity.” By Max Delbruck For biology• Life was originated around 3.8 billions years ago and was restricted to the earth! • Always has exceptions • Explanation usually were not based on universal laws but rather were pluralistic • Two key questions in biology • “How?” or “how come?” • “Why?” or “what for?” What is the cause of bird migration to south in the autumn? How? • An extrinsic physiological cause – Cold air or short daytime • An intrinsic physiological cause – Photo- or temperaturesensor tie in with migration Why? • A genetic cause: an acquired genetic program in the course of the evolutionary history • An ecological cause: insect eater, must migrate before the winter come • The owl? Prediction • Is an essential qualification for physical law! • Predict the existence of one unknown planet (Neptune) due to the abnormal movement of Uranes • Predict the path of light would be curved when it pass through a big mass • For functional biology: yes! • For evolutional biology: probably no! • It is meaningless to discuss the change of life form in the wild in the future! Teleology( 目的論 ) • From egg to adult: a process with a purpose or with a predetermined state? • Important question in biology • Do not discuss “purpose” in physical sciences • Does the purpose of a pebble to become smooth and round is to make it better laying down in the river bed? Populations • For physicist: every atoms or molecules are identical • For biologist: Every individual organisms are unique (different) Biology: a science with evolutionary history Future challenge in life science Understanding of genetic program • A historically evolved genetic program coded in the DNA of the nucleus (genome program) • How the genetic program make every individual unique? (functional genomics) • How the genetic program evolved? (comparative genomics) How the new properties emerged? (Emergence) • A whole is more than the sum of its parts • Living beings are not just piles of characters or molecules, their function depends on their organization, mutual interrelations, interactions, and interdependencies • New properties emerge at higher levels of integration which could not have been predicted from knowledge of the lower-level components “The genetic program is the product of a history that goes back to the origin of life, and thus it incorporates the “experiences” of all ancestors.” From “Is biology an autonomous science?” By Ernst Mayr 1985 "Nothing in biology makes sense except in the light of evolution." T Dobzhansky 1900 1975