chapter 14: history of life

biogenesis

biogenesis- all living things come from other living things spontaneous generation-  a thought that living things could come from nonliving things (maggots on rotting meat) Redi's experiment hypothesized that if flies were kept away from meat, it wouldn't generate maggots The control group with flies generated maggots while the experimental group with covered jars did not. Spallanzani's experiment tested the hypothesis that microorganisms just appeared control group with open flasks of broth had microorganisms while the experimental group with no microorganisms inside and was sealed did not. Pasteur's experiment tested the same hypothesis as Spallazani but with a different approach used a flask with a curved neck versus a flask without one the curved one prevent microorganisms from entering while the straight neck did not

Earth's history

its estimated that earth was formed through many collisions with space debris radiometric dating- a method of dating geological or archeological specimens by knowing the decay rate of radioactive isotopes isotopes- atoms of the same element that differ in the number of neutrons they contain mass number- the total number of protons and neutrons in the nucleous carbon is 12 and atomic number is 6 which means it has 6 protons and 6 neutrons radioactive decay- when unstable nuclei release particles or radiant energy until they are stable radioactive isotopes- isotopes that undergo radioactive decay occur naturally helped to date the age of the earth half life- the amount of time it takes for one half of any sized sample of an isotope to decay into a stable form this depends on the isotope the amount of radioactive isotope can be measured to help determine the material's age see page 283 for details first organic compounds amino acids may have been formed when high temperatures combined the gases ammonia, hydrogen, water vapor, and methane complex chemical reactions from lightning and uv radiation would resultn proteins some scientist think these have been carried to earth on debris

the first life-forms