1. The atmosphere of early earth contained N2, CO2, H2O, H2S, NH3, CH4, and maybe H2. O2 was absent. Then the atmosphere was reducing, now it is oxidizing as a result of several millions years of photosynthesis.
2. These experiments took compounds assumed present in the early atmosphere, bombarded them with electricity, and observed the formation of simple organic molecules-formic acid, urea, and the amino acids glycine and alanine.
3. RNA-worlders claim that without molecules capable of transmitting genetic information, proteins and other complex molecules could not have evolved successfully. Protein-firsters maintain that enzymes (proteins) would have had to exist for anything to replicate at all. The discovery of ribozymes and their apparently autocatalytic properties has therefore been very attractive to many theoreticians.
4. Cellular organization, growth and metabolism, reproduction, and heredity are necessary. Most living things also exhibit sufficient characteristics such as movement, sensitivity, and complexity.
5. Coacervates are protein/lipid aggregations, have a quasi-lipid bilayer membrane, accumulate more organic materials inside themselves, and divide by "budding." They are not alive because they possess no known genetic material.
6. Prokaryotic organisms were probably the earliest known organisms, appearing about 3.5 billion years ago. They are most closely related to cyanobacteria.
7. Archaebacteria are similar to the eubacteria except in a few key areas: their cell walls lack peptidoglycan, they possess a lipid in their cell membranes unique to that group, their genetics are surprisingly similar to eukaryotic genetics (eubacterial genetics are very different), and their biochemistry is unique, permitting them to survive in extreme environments (such as high temperature or salt content). Methanogens are characteristic archaebacteria. Photosynthetic prokaryotes are limited to the eubacteria.
8. The first eukaryotes known are fossils 1.3 to 1.5 billion years old. Eukaryotes differ from earlier prokaryotes in that they have a nucleus. Eukaryotes are thought to have evolved through the phenomenon of endosymbiosis.
9. The six kingdoms of life are the Archaebacteria (methanogens); Eubacteria (true bacteria); Protista (single-celled eukaryotes), Fungi (multicellular saprophytes such as mushrooms), Plantae (multicellular eukaryotic autotrophs such as trees, bushes, and flowers); and Animalia (multicellular eukaryotic heterotrophs such as jellyfish, spiders, sea cucumbers, fish, and birds).
10. It is likely that there is some form of life elsewhere because by the sheer mathematical probability that with so many stars and so many planets, life should have evolved somewhere out there. For carbon-based life forms to evolve, a planet must have temperature and atmospheric characteristics similar to those on earth.