1. PTYS 214 – Spring 2011  Lecture 1 can be downloaded from the class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/Pierazzo_214/  Homework #1 DUE Thursday, Jan. 20 (download it from the class website)  Useful Reading: check out the class website, under “Reading Material” http://www.ibiblio.org/jstrout/uploading/potter_life.html http://www.astrobio.net/news/article428.html http://www.astrobio.net/news/article1319.html Announcements

2. What Is Life? How would we distinguish between living and not living?

3. Identify Some Common Characteristics of Living Things  “Common” means it should include all types of life  “Living Things” by definition are living things we know, so they only represent life on Earth

4. Can You Think of some Properties That Are Important for Life?

5. Some Properties of Life  Order, organization  Energy utilization and production  Maintenance of internal constancy (homeostasis)  Reproduction, growth and development (directed in part by heredity)  Response to the environment  Evolutionary adaptation (slow change)  Motion  Waste Production

6. Order/organization Multicellular organism Organ system Organ Tissue Cell Organelle Molecule Atom

7. Energy Use Photosynthesis: process that converts CO 2 into organic compounds, especially sugars, using the energy from sunlight Metabolism : biochemical reactions that acquire and use energy

8. Homeostasis Ability of an organism to maintain its internal environment despite conditions in the external environment E.g., human body temperature –If body temperature rises, you sweat –If body temperature lowers, you shiver

9. Reproduction Asexual reproduction: involves a single parent; offsprings are genetically identical to the parent (exact copies) Examples? Sexual reproduction: involves two parents; offsprings are genetically diverse (not a copy) Examples?

10. Growth and Development

11. Immediate Response Immediate response to a stimulus

12. Evolutionary Adaptation Inherited behavior or characteristics that enables an organism to survive and reproduce Over time, adaptations are modified by natural selection

13. Darwin and Natural Selection See it online at: http://www.youtube.com/watch?v=pPghdBIGW9g

14. 1)Any population of a species tends to produce far more offsprings than the environment can support 2) The overproduction leads to a struggle for survival among individuals 3) Individuals of any population are slightly different from one another in many heritable traits 4) Some individuals possess traits that allow them to better compete for resources Charles Darwin (1809-1882) “The origin of species by means of natural selection” (1859) Conclusion: In any local environment, heritable traits that enhance survival and successful reproduction will become progressively more common in the following generations

15. All finches on the Galapagos Islands had a common ancestor from South America but all 13 species adapted to particular microenvironments Natural Selection (Darwinian Evolution)

16. Descendants of a gray wolf Artificial Selection

17. Non-living objects are not a subject to Darwinian Evolution

18. Activity: Is It Alive? (5-10 minutes)  Get together in groups and discuss the examples presented  Which of the six requirements presented represent a necessary and which a sufficient condition for life?

19. Activity Discussion MuleCrystalFireRobotVirus Reproduce Energy use Grow Adapt Order Evolve

20. Activity Discussion MuleCrystalFireRobotVirus ReproduceNO Energy useYES GrowYES AdaptYES OrderYES Evolve?

21. Activity Discussion MuleCrystalFireRobotVirus ReproduceNO? Energy useYES? GrowYES AdaptYES? OrderYES Evolve??

22. Activity Discussion MuleCrystalFireRobotVirus ReproduceNO?? Energy useYES? GrowYES AdaptYES?? OrderYES ? Evolve???

23. Activity Discussion MuleCrystalFireRobotVirus ReproduceNO??? Energy useYES? GrowYES ? AdaptYES??? OrderYES ? Evolve????

24. Activity Discussion MuleCrystalFireRobotVirus ReproduceNO???? Energy useYES? ? GrowYES ?? AdaptYES??? OrderYES ? Evolve????? Which is ALIVE?

25. Necessary vs. Sufficient Conditions “A” cannot be true unless “B” is true “B” is a necessary condition for “A” If “B” is true then “A” has to be true “B” is a sufficient condition for “A”

26. Examples: Condition: Effect: living in New York City living in the United States Necessary? Sufficient? Condition: Effect: not smoking living long Necessary? Sufficient? No Yes No

27. Examples: Condition: Effect: being a male being a father Necessary? Sufficient? Condition: Effect: being human being a mammal Necessary? Sufficient? Yes No Yes

28. Definition of Life  “A system capable of evolution by natural selection” (Carl Sagan, 1970)  “A self-sustaining chemical system capable of undergoing Darwinian evolution” (NASA’s definition)

29. Problem: Looking for Life  NASA’s definition of life is not very useful in search for extraterrestrial life  In searching for life we need to know the ecological requirements for life

30. Basic Necessities of Life Premise: our limited knowledge of life is based on the only reference system available: planet Earth Life (as we know it!) requires: 1. Building blocks : organic molecules based on C plus a few other elements, like H and O, and nutrients N, P, S, Fe 2. A source of energy (food) 3. The presence of a solvent: liquid water (H 2 O) 4. Suitable environmental conditions Necessary and sufficient conditions to support life Is the set of conditions necessary and/or sufficient for life to start?

31. Carbon is abundant in the Universe but Earth is depleted in carbon So why did life “choose” carbon? Carbon

32. Chemical element: Atom distinguished by the number of protons in the nucleus (atomic number) Ion: atom with a net charge, # electrons  # protons Atoms

33. Discrete electron levels are arranged in shells, each with a maximum occupancy: - First shell has the lowest energy (maximum 2 electrons) - Second and third shells have room for 8 electrons - Fourth and fifth shells have room for 18 electrons - Etc. Atoms are most stable if their outer shell is full Modern Atom