General Biology 2

• Earth has been around for about 4.6 billion years
• Early Earth environment


  • Constantly bombarded with meteorites and other space debris
  • Extreme temperature, evaporating the liquid water into the atmosphere
  • Atmosphere filled with water vapor, nitrogen oxide, carbon dioxide, methane, ammonia, and hydrogen sulfide but not oxygen
  • Continuous volcanic eruptions released gases that added to the atmosphere making it more toxic
  • Lightning, torrential rains, and ultraviolet radiation combined with the intense volcanic activity and constant meteorite bombardment made early Earth an inhospitable environment

  
• Oparin-Haldane hypothesis


  Suggests that life arose gradually from inorganic molecules, with "building blocks" like amino acids forming first and then combining to make complex polymers
• Miller-Urey experiment


  Provided the first evidence that organic molecules needed for life could be formed from inorganic components
• Endosymbiotic theory


  Explains that early eukaryotes and early prokaryotes existed at the same time

  
• RNA can regulate its own synthesis with an enzyme-like RNA called as ribozyme
• Mitochondria and chloroplasts were originally prokaryotic cells in the earliest years

  
• The Earth is 4.6 billion years old
• Protocells were called as the first cells
• Earth's atmosphere before had no oxygen, when life didn't begin yet
• According to studies, DNA was not the first to form than RNA
• The Oparin-Haldane hypothesis and Miller-Urey experiment did not contradict each other's claims explaining the origin of life on Earth
• Early Earth


  • Constantly bombarded with meteorites and other space debris still in circulation from the Big Bang
  • Extreme temperature, evaporating the liquid water into the atmosphere
  • Atmosphere filled with water vapor, nitrogen oxide (NO2), carbon dioxide (CO2), methane (CH4), ammonia (NH4), and hydrogen sulfide but not oxygen
  • Continuous volcanic eruptions released gases that added to the atmosphere making it more toxic
  • Lightning, torrential rains, and ultraviolet radiation combined with the intense volcanic activity and constant meteorite bombardment made early Earth an inhospitable environment

  
• Oparin-Haldane hypothesis


  • Life arose gradually from inorganic molecules, with "building blocks" like amino acids forming first and then combining to make complex polymers
  • Chemicals in the Earth's atmosphere reacted with other organic compounds, and energy for this reaction was provided by lightning and radiation
  • Oceans at that time were a soup of organic molecules, which was termed as "primordial soup"
  • Recreated in 1953, called as the Miller-Urey experiment, which supports the claim of the Oparin-Haldane hypothesis

  
• RNA World Synthesis


  • RNA (ribonucleic acid) was first to form since RNA can regulate its own synthesis with an enzyme-like RNA called ribozyme
  • Subsequent events of random combination of already existing molecules took place which gave rise to other macromolecules and eventually to the first cells – protocells
• Endosymbiosis theory


  • Ancient eukaryotes came from the ancient prokaryotes
  • Explains the evolution of mitochondria and chloroplasts, two of the organelles from eukaryotic cells which were free prokaryotic cells during ancient time
  • Evidence: Both prokaryotes and chloroplasts/mitochondria have circular DNA, their own ribosomes, divide through binary fission, and have their own cell membranes

  
• Chronological order of the inorganic materials that emerged first on earth

  1. simple elements

  2. molecules

  3. macromolecules

  4. RNA/ ribozyme

  5. DNA and proteins

  6. CELL
• The Miller-Urey experiment recreated the Oparin-Haldane hypothesis
• RNA was first to form since RNA can regulate its own synthesis with an enzyme-like RNA called ribozyme
• Endosymbiosis theory explains the evolution of mitochondria and chloroplasts, two of the organelles from eukaryotic cells which were free prokaryotic cells during ancient time

  
• Geologic time scale divisions

  • Eons
  • Eras
  • Periods
  • Epochs
• Eons have a duration of hundreds of million years
• Earth's geologic history is divided into four eons: Hadean, Archaean, Proterozoic, and Phanerozoic
• Eons are divided into eras, and eras are further subdivided into periods
• Epochs are subdivisions of the time scale which are the shortest among the divisions
• Rise of the Single-Celled Organisms occurred 3.5 billion years ago
• Photosynthesis and Oxygen Revolution occurred 2.4 billion years ago
• The First Eukaryotes developed 1.6–2.1 billion years ago
• Rise of the Early Multicellular Eukaryotes occurred 1.1 billion years ago

  
• Cambrian Explosion occurred 542 million years ago
• Colonization of Land by larger forms of life began about 500 million years ago
• K/T (Cretaceous-Tertiary) Extinction occurred 66 million years ago
• Early Invertebrates

  • Brachiopods
  • Trilobites
  • Anomalocaris
  • Pikaia gracilens
• Early Coral Reefs, Fishes, Vascular Plants

  • Crinoids
  • Brachiopods
  • Jawless fish
  • Jawed fish
  • Cooksonia
• Early Coral Reefs, Fishes, Vascular Plants (Devonian Period)

  • Placoderms
  • Ray-finned fish
  • Lobe-finned fish
  • Lycophytes
  • Horsetails
  • Ferns
  • Tetrapods
  • Insects
• Amphibians, Origins of Reptiles, First Seed Plants (Carboniferous Period)

  • Ferns
  • Fernlike trees
  • Horsetails
  • Club mosses
  • Seed ferns
  • Cordaites
  • Early amphibians
  • Earliest reptiles
• Reptiles (Dinosaurs), First Angiosperms, First Mammals (Mesozoic Era)

  • Marine reptiles
  • Dinosaurs
• Mammals (Cenozoic Era)


  • First primates
  • First rodents
  • Apes
  • Homo sapiens
• Fossils


  Evidences of organisms that lived in the past, including actual remains and traces of past activities
• Stromatolites


  Layered sedimentary rocks formed by ancient cyanobacteria