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Evolution 01.22.08 / 01.23.08
What if I don’t believe it? • Consider Acts 17:22-23 • Paul then stood up in the meeting of the Areopagus and said: "Men of Athens! I see that in every way you are very religious. For as I walked around and looked carefully at your objects of worship, I even found an altar with this inscription: TO AN UNKNOWN GOD. Now what you worship as something unknown I am going to proclaim to you.
What if I don’t believe it? • Ask yourself if you even understand it? • Realize that you really do believe it… at least, some of it. • Evolution is a theory, which means it’s complex • Parts of evolution are fact that no one contests
So, why should I care? • Do you know why purebred dogs are more likely to have health problems than mutts? • Do you know why 1.7 million Americans now contract “superbug” infections each year? • Pay attention and maybe you’ll find out even more.
So, why should I care? • It’s everywhere
Chapter 14History of Life 01.22.08 / 01.23.08
Biogenesis • Biogenesis – all living things comes from other living things • From Greek bioun meaning “life” and gignesthai meaning “beginning” • Like the book of Genesis (the beginning) • Spontaneous generation – the now abandoned view that life spontaneously arises • used to explain why maggots appeared on rotting meat
Biogenesis • Redi’s experiment (1600s) • observed that maggots turned into flies and that maggots often seemed to appear after flies had been in the area • experimental group had meat covered with netting to keep flies out • control group had meat exposed to flies • demonstrated that maggots are produced from living flies
Biogenesis • Redi’s experiment • Hypothesis: maggots develop from flies • Independent variable: exposure to flies • Dependent variable: development of maggots • Data: observed maggots (yes or no) • Conclusion: maggots form from flies, not spontaneously
Biogenesis • Spallanzani’s experiment (1700s) • Tested the idea of a “vital force” • Boiled broth to kill microorganisms • Sealed flask of exp. group • Left control flask open • Critics said the heat killed the “vital force”
Biogenesis • Pasteur’s experiment (1800s) • used a curved, but open, neck on a flask to keep microorganisms out of broth • broth remained clean for up to a year • once the neck was broken, broth was contaminated within a day
Cell Theory • These experiments led to Cell Theory, which states: • All living organisms are made of one or more cells • Cells are the basic unit of structure and function in all living organisms • All cells come from other cells • In general, evolutionary theory makes no effort to explain how life began, just how it has changed
Earth’s History • The earth is about 4.6 billion years old • Age is determined by radiometric dating • radioactive materials decay from their parent isotopes into daughter isotopes • this decay occurs at a specific rate, known as half-life
Earth’s History • So, how did life begin? • Oparin and Haldane proposed in the 1920s that the earth’s early atmosphere contained large amounts of ammonia, hydrogen gas, water vapor and methane • These chemicals might have collected in water and, with the energy of lightning and solar radiation, combined into macromolecules, such as amino acids
Earth’s History • Miller-Urey experiment • Tested Oparin and Haldane’s hypothesis by combining inorganic chemicals with electricity • Created organic materials, such as amino acids • Various revisions have been made to test differing hypotheses for the early atmosphere
Earth’s History • But, didn’t I say evolution does not try to explain how life began? • Yes • Miller received his PhD in chemistry, not biology • But, science is interdisciplinary, so I said, “in general.” • In general, evolutionary theory makes no effort to explain how life began, just how it has changed
Earth’s History • That leads us to astrobiology • Formerly known as exobiology • Study of life in the universe • Organic molecules have been found in meteorites
Earth’s History • Experiments have shown some organic molecules can form spontaneously • Microspheres are made of proteins that form a membrane • a certain type of radioactive microsphere is now used in oncology • Coacervates are made of various molecules, including fats, amino acids and sugars
The First Life-Forms • Read if you want to know more….
Check-up • Describe the difference between spontaneous generation and biogenesis. • Describe Redi’s experiment. • Describe Spallanzani’s experiment. • Describe Pasteur’s experiment.
Check-up • How do you personally benefit from the research of Spallanzani and Pasteur? • Describe cell theory. • Describe the Miller-Urey experiment and its importance.