tailieunhanh - EARTH AS AN EVOLVING PLANETARY SYSTEM Part 6

Tham khảo tài liệu 'earth as an evolving planetary system part 6', khoa học tự nhiên, địa lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Conclusions 221 events described in Chapter 9 may have profound effects not only on long-term variations in the atmosphere-ocean system but also on life on this planet. Further Reading Frakes L. A. Francis J. E. and Syktus J. L. 1992. Climate Modes of the Phanerozoic. Cambridge University Press New York 274 pp. Holland H. D. 1984. The Chemical Evolution of the Atmosphere and Oceans. Princeton University Press Princeton NJ 581 pp. Huber B. T. Wing S. L. and MacLeod K. G. eds. 1999. Warm Climates in Earth History. Cambridge University Press Cambridge UK 480 pp. Kasting J. F. 1993. Earth s early atmosphere. Science 259 920-926. Wigley T. M. L. and Schimel D. S. 2000. The Carbon Cycle. Cambridge University Press Cambridge UK 310 pp. This Page Intentionally Left Blank Living Systems 7 General Features Although the distinction between living and nonliving matter is obvious for most objects it is not easy to draw this line between some unicellular organisms and large nonliving molecules such as amino acids. It is generally agreed that living matter must be able to reproduce new individuals it must be capable of growing by using nutrients and energy from its surroundings and it must respond in some manner to outside stimuli. Another feature of life is its chemical uniformity. Despite the great diversity of living organisms all life is composed of a few elements chiefly C O H N and P grouped into nucleic acids proteins carbohydrates fats and a few other minor compounds. This suggests that living organisms are related and that they probably had a common origin. Reproduction is accomplished in living matter at the cellular level by two complex nucleic acids ribonucleic acid RNA and deoxyribonucleic acid DNA . Genes are portions of DNA molecules that carry specific hereditary information. Three components are necessary for a living system to self-replicate RNA and DNA molecules which provide a list of instructions for replication proteins that promote replication and a host .