the history of life on earth

• geologists believe that the earth is 4. 6 billion years old
• life arose on earth around 3.5 billion years ago
• over the earth's vast history, both gradual and catastrophic processes have produced innermost changes shown by geologic pieces of evidence such as fossils.
• Columbus is the one who rediscovered the new world
• understanding the geologic time scale (gts) reminded us of our time and place in the universe.
• geologic time scale is a calendar of events of earth's history of life where they are arranged in chronological order.
• paleontologists and geologists commonly used this to present the earliest form of life that appeared, evolved, and go extinct on Earth.
• Many of the ancient life forms were discovered through the layers of rocks like sedimentary rocks and through fossilized or petrified remains.
• the four eras in geologic time scale is pre-cambrian era, paleozoic era, mesozoic era, and cenozoic era.
• Precambrian- which is 542 million years ago where single-celled organisms came into existence
• precambrian era- The end of this span is the rise of few more complex animals in the oceans such as Jellyfish
• Precambrian- There was still no life on land, and the atmosphere was just beginning to accumulate the oxygen requirement for higher-order animals to survive.
• Paleozoic Era- an era that began with the Cambrian Explosion a relatively rapid period of speciation kicked off a long period of life flourishing on Earth.\
• paleozoic era- There are a huge number and kinds of living organisms from the ocean that moved towards the land.
• paleozoic era- The end of this Era comes with the largest mass extinction in the history of life on Earth, wiping out 75 percent of marine life and nearly 70 percent of life on land.
• Mesozoic Era- which was also known as the “age of dinosaurs” since dinosaurs were the dominant species of this age.
• mesozioc era- The climate during this Era was very humid and tropical, which many lush, green plants sprouted all over the Earth. Herbivores thrive and small mammals came into existence, birds developed evolved from the dinosaurs.
• Cenozoic Era- During this Era, there has been a significant increase in the size of brains among vertebrates, including humans.
• Cenozoic Era- This is the most recent geological time period, starting about 66 million years ago when the last major extinction event occurred.
• Cenozoic Era- The Cenozoic Era is characterized by the rise of mammals, flowering plants, and insects.
• The Cenozoic Era is divided into three periods: Paleogene Period, Neogene Period, and Quaternary Period.
• Cenozoic Era – which began 65 billion years ago to the present, this final era on the GTS wherein smaller mammals survived and become dominant.
• Cenozoic era- The climate of this Era is cooler and drier compared to the Mesozoic Era. This is an “Ice Age” which covered most temperate regions of the Earth with glaciers. All species of life- including humans evolved into their present-day form throughout this era.
• Fossils are evidence of organisms that lived in the past. They may be actual remains like burrows, nests, and dinosaurs’ footprints or even the ripples created in our prehistoric shore
• Six ways of Fossilization are; Unaltered preservation,Per mineralization/ Petrification,Replacement,Carbonization/ or Coalification,Recrystallization, and Authigenic preservation.
• Unaltered preservation- wherein small organisms or past trapped in amber, hardened plant sap is being observed.
• Per mineralization/ Petrification- the organic contents of bone and wood are replaced by silica, calcite, or pyrite, forming a rock-like fossil.
• Replacement- hard parts are dissolved and replaced by other minerals, like calcite, silica, pyrite, or iron.
• Carbonization/ or Coalification- the other elements are ionized and only the carbon remained.
• Recrystallization- the hard parts are converted into more stable minerals or small crystals turned into larger crystals.
• Authigenic preservation – molds and casts are formed after most of the organisms have been destroyed or dissolved.
• Molds- The impression is made in a substrate negative image of an organism. ( hint; type of fossil)
• Casts- When a mold is filled in.
• Petrified- Organic material is converted into stone.
• Original remains- Preserved wholly (frozen in ice, trapped in tar pits, dried/desiccated inside caves in arid regions, or encased in an amber/fossilized resin).
• Carbon film- Carbon impression in sedimentary rocks.
• Trace/ Ichnofossils- Records the movements and behaviors of the organism.
• Knowing the age of fossils can help a scientist establish its position in the Geologic Time Scale and find its relationship with other fossils.
• There are two ways to measure the age of fossils: relative dating and absolute dating.
• Scientists also use several types of fossils which are referred to as index fossils to aid in relative dating. Index fossils are fossils that are identified to be found only within a very specific age span.