history of the earth

• Geologic Time Scale


  A record of life forms and geological events in Earth's history
• Geologic Time Scale


  • Divides up the history if the earth based on life-forms that have existed during specific times since the creation of the planet
• Fossils


  Remnant, impression, or trace of an animal or plant of a past geologic age that has been preserved in Earth's crust
• Fossil Record


  The primary source of information about the history of life on Earth
• Eon


  The largest division of geologic time scale; half billion – nearly 2 billion years
• Eons

  • Precambrian
  • Phanerozoic
• Precambrian


  • 4.5 billion years; about 88% of the Earth's history
• Hadean


  Formation of the Earth
• Archean


  Formation of the oldest fossil
• Proterozoic


  Formation of bacteria and blue algae
• Phanerozoic


  The current geologic eon in the geologic time scale, and the one during which abundant animal and plant life existed
• Era


  Divisions that span time periods of tens to hundreds of million years
• Eras

  • Paleozoic Era
  • Mesozoic Era
  • Cenozoic Era
• Paleozoic Era


  • Known as the "ancient or old life"; started more than 540 million years ago Many organisms that have emerged during this time were invertebrates.
• Period


  A division of geologic history with spans of no more than 100 million years
• Periods

  • Paleozoic Era
  • Mesozoic Era
  • Cenozoic Era
• Cambrian Period


  The era began with a spectacular burst of new life. This is called as Cambrian Explosion
• Ordovician Period


  • A division of geologic history with spans of no more than 100 million years. A great evolutionary radiation of marine life
• Silurian Period


  In the oceans, coral appeared, and fish continued to evolve. On the land, vascular plants appeared
• Devonian Period


  The first seed plants evolved. Fish with lobe fins evolved
• Carboniferous Period


  Widespread forests of huge plants left massive deposits of carbon that eventually turned to coal. The first amphibians evolve to colonize land. The first reptiles evolved
• Permian Period


  All the major land masses collided to form a supercontinent called Pangaea. Plants and animals evolved adaptations to dryness
• Mesozoic Era


  "Middle Life"; started more than 280 million years ago. Age of Reptiles, Also known as "Era of Dinosaurs"
• Triassic Period


  • The first dinosaurs branched off from the reptiles and colonized the land, air and water. Huge seed ferns and conifers dominated the forests, and modern corals, fish and insects evolved. The supercontinent Pangea started to separate into Laurasia and Gondwanaland.
  • The Triassic Period ended with a mass extinction
• Jurassic Period


  "The Golden Age of Dinosaurs" earliest birds evolved from reptile ancestors. All the major group of mammals evolved, though individual mammals were still small in size. Flowering plants appeared for the first time, and new insects also evolved to pollinate the flowers
• Cretaceous Period


  Dinosaurs reached their peak in size and distribution. Earth's overall climate was warm; even the poles lacked ice
• Cenozoic Era


  "Recent Life" started 65 million years ago and continues up to present. Also known as "The Age of Mammals"
• Tertiary Period


  Earth's climate was generally warm and humid. Mammals called primates evolved, including human ancestors. Modern rainforests and grasslands appeared. Flowering plants and insects were numerous and widespread
• Quaternary Period


  Earths climate cooled leading to a series of ice ages. This created land bridges between continents, allowing land animals to move to new areas
• Epoch


  Smallest division of the geologic time scale