Fossil Vocabulary 1.) Paleontologist (70) – Scientist who studies fossils. 2.) Principle/ Law of Superposition (78)In undisturbed layers of rock, the oldest layers are found on the bottom and the youngest on the top. 3.) Relative Age/ Dating (79) - Its age in comparison to the age of other things. 4.) Index Fossil (75) The remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically. 5.) Trilobites (100/105) - Small, hard-shelled organisms that crawled on the seafloor and sometimes swam through the water. They are considered to be index fossils. 6.) Extinction Causes: Natural Causes- Meteorite colliding with Earth, Mass volcanic activity, draught, climate change (leading to loss of vegetation/habitat), Intro. Of predator due to natural causes i.e. migration Man-made CausesPollution, Deforestation/Habitat destruction, Hunting, New predators 7.) Geologic Time Scale (100) – The division of Earth’s history. 8.) Era (101) - Next to Eons, the longest subdivisions, which are marked by major, striking, and worldwide changes in the types of fossils present. 9.) Period (101) - Units of geologic time characterized by the types of life existing worldwide at the time, Eras are divided into these. 10.) Epoch (101) - When periods are divided into smaller units of time. 11.) Precambrian (108) -The longest part of Earth’s history which lasted from 4.5 billion years ago to about 544 million years ago. Not many fossils at all. 12.) Paleozoic (110) – “Era of ancient life”. An abundance of organisms with hard parts, such as shells, marked the beginning of this era. Many marine fossils due to shallow seas covering a large part of Earth. Vertebrates, amphibians, and reptiles evolved during this era. 13.) Mesozoic (116) – “Era of Middle Life” Pangaea began to break apart. Reptiles and Dinosaurs evolved. Birds, Mammals, Gymnosperms/ Non-Flowering Plants (ex. Pine trees), and Angiosperms/ Flowering Plants. 14.) Cenozoic (120) “Era of Recent Life” Climate became cooler and “ice ages” occurred. Alps, Andes and Himalayan Mountains were created. Large Mammals- Elephants, horses, camels, deer, humans, kangaroos, koala’s (marsupials). 15.) Present day Earth: Cenozoic Quaternary Holocene Era Period Epoch END OF MESOZOIC- Meteorite collided with Earth, causing a huge dust cloud to rise into the atmosphere, blocking out the Sun. END OF PALEOZOIC- meteorite and/or changes in climate and lowering of sea-level due to the formation of Pangaea. More land, less seas meaning less marine life.