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Lecture 4

Astronomy 2232F/G Lecture 4: 2232 Lecture 4-The Search for Life

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Astronomy 2232F/G
Els Peeters

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Lecture 5 Page 1 - 3 questions driving what is defined as astrobiology: o Where do we come from? o Are we alone? o Where are we going? Page 2 - What is alive and what is dead? o Needs energy to function, can move at carrying speeds and turn corners, expel waste but animals are alive and vehicles are not? What separates a car/rock from a living organism? Page 3&4 - 6 Key properties of life: 1. Materials in living organisms exhibit some kind of ORDER. Books and rock crystals have order but are not alive. It is a necessary condition for life, but alone does not work 2. Living organisms REPRODUCE and are products of REPRODUCTION. Mules are alive but cannot reproduce, and are products of reproduction. Viruses cannot reproduce alone because they need a host. Alive or not? (not dont need energy or have a metabolism) 3. Living organisms GROW and DEVELOP at some point in their life; heredity 4. Living organisms USE ENERGY to create and maintain order within cells, reproduce and to grow. A fridge utilizes energy life needs a long-term continual energy source 5. All living organisms interact with their surroundings and RESPOND TO CHANGES IN THE ENVIRONMENT. Sweating, panting, BF to maintain temperature thermostat also does this 6. Life EVOLVES over (geologic) time new organisms evolve better suited to environments new species form Page 5 - Fire conforms to 4 of 5 properties of life BUT is not alive Page 6 - The most general definition of what is life is adopted by NASA in 1992: life is a self- sustained chemical system capable of undergoing Darwinian evolution. - Alternatively, life is defined by what it does not what it is made of much less restrictive than other ideas (non-biological life aka artificial intelligence) Page 7 - All earth life is carbon based - Finding carbon-based life is the assumption which drives our current exploration of the solar system - Carbon forms the backbone for polymeric chemistry essential for life: nucleic acid polymers of DNA and RNA, amino acids and polymers of proteins - Circle image is periodic table of what life on earth need
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