Geologic Time Scale PDF

General Biology 2  Learning objectives: Describe general features of the history of life on Earth, including generally accepted dates and sequence of the geologic time scale. Describe characteristics of major groups of organisms present during these time periods....

General Biology 2  Learning objectives: Describe general features of the history of life on Earth, including generally accepted dates and sequence of the geologic time scale. Describe characteristics of major groups of organisms present during these time periods. Background: It is estimated that the Earth formed along with the solar system 4.6 billion years ago. Life on Earth arose around 3.5 billion years ago. Over Earth’s vast history, both gradual and catastrophic processes have produced enormous changes. Protocells – the term for first cells Stromatolites – the first fossil evidence of life, were thought to have lived on earth 3.5 billion years ago. – are layered sedimentary rocks formed by ancient cyanobacteria.  Oxygen revolution about 2 Fossil evidence shows that billion years ago. eukaryotic organisms are The sudden increase in about 2.1 billion years old. oxygen is due to the Endosymbiotic theory – evolution of eukaryotic cells. an explanation on the origin of eukaryotes Evidence supporting endosymbiotic theory Prokaryotes show the same Present prokaryotes and the enzyme and transport endosymbionts have similar systems as those of the ribosomal structures. mitochondria and plastids. Endosymbionts contain a Circular DNA is present in both machinery that can transcribe with few or no histones or other and translate DNA into proteins types of protein. similar to present prokaryotes. Binary fission, as a mode of reproduction in prokaryotes, is similar to splitting mechanisms involved in reproduction of endosymbionts. Background: WHAT IS ? Geological Time Scale a record that depicts Earth’s history and the order of life from 2,500 million years ago to the present Scientists developed the time scale by studying fossils and layers of rock worldwide. It spans Earth's entire history and is separated into four principal divisions Geological Time Scale PALEONTOLOGY - is the study of the history of life on Earth as based on fossils. Fossils are the remains of plants, animals, fungi, bacteria, and single-celled living things that have been replaced by rock material or impressions of organisms preserved in rock. Geological Time Scale STRATIGRAPHY - scientific discipline concerned with the description of rock successions and their interpretation in terms of a general time scale. It provides a basis for historical geology, and its principles and methods have found application in such fields as petroleum geology and archaeology Geological Time Scale RADIOACTIVE / RADIOMETRIC DATING - helped determine the absolute divisions in the time scale. It is a technique used to determine the age of materials such as rocks.  Hadean Pre-Cambrian Archean Paleozoic Proterozoic Mesozoic Phanerozoic Cenozoic largest segment of geologic time; spans hundreds to thousands of million of years ago  Hadean (4.5 – 4 billion years ago) – the oldest eon and was officially recognized only in 2012 - derived from the word Hades (God of the underworld in Greek mythology), referring to the hellish conditions and violent cosmic collisions that characterized Earth four billion years ago - represents Earth's earliest history, during which the planet was characterized by a partially molten surface, volcanism, and asteroid impacts - earths continental and oceanic crust began to solidify.  Archean (4,000 – 2,500 mya) – still not much clear among geologists due to the few fossils or mineral evidence that could support it - began after the formation of Earth’s crust, atmosphere, and seas - protocells evolved into anaerobic cells, and into prokaryotic archaea and bacteria  Proterozoic (2,500 – 541 mya) – characterized by the presence of oxygen in the atmosphere due to the emergence of cyanobacteria, allowing other organisms, such as eukaryotes and other multicellular organisms to live - many anaerobic unicellular organisms disappear because oxygen is toxic to them - prokaryotes with smaller prokaryotic symbionts evolved to become the first eukaryotic unicellular organisms which later gave rise to multicellular organisms  Proterozoic (2,500 – 541 mya) - during the Ediacaran Period (635 mya), multicellularity is evidenced by the fossil of diverse algae and soft-bodied invertebrates - grazers and suspension feeders or scavengers are called Ediacaran fauna that have given rise to cnidarians and bilaterians - Dickinsonia costata – organism that lived during Ediacaran period  Phanerozoic (541 mya – present) - “visible life” - is divided into three major spans of time largely on the basis of characteristic assemblages of life-forms: 1. Paleozoic 2. Mesozoic 3. Cenozoic ERAS…  span time periods to tens to hundreds of millions of years PRE-CAMBRIAN – 88% of Earth’s History - The earliest living organisms were microscopic bacteria, which show up in the fossil record as early as 3.4 billion years ago. - Some three billion years ago the Earth's atmosphere was virtually devoid of oxygen. - It's thought the final stages of Precambrian time were marked by a prolonged global ice age.  PALEOZOIC ERA (541 – 251 mya) - The Cambrian period is the 1st Period of the Paleozoic Era. - Explosion of life in the oceans began during this era. - Most of the continents were covered in warm, shallow seas.  PALEOZOIC ERA (ANCIENT LIFE) – Events: 1. Invertebrates were dominate – Trilobites 2. Fish emerged during this time 3. Fish led to the arrival of amphibians 1. The End of the Paleozoic Era is called the “Age of Amphibians”  PALEOZOIC ERA (ANCIENT LIFE) –Events: 1. Early land plants including mosses, ferns and cone-bearing plants. 2. The early coal forming forests were also formed during this time.  PALEOZOIC ERA (ANCIENT LIFE) – At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals. - Possible causes of this Mass Extinction Event: 1.Lowering of sea levels when the continents were rejoined as Pangaea (convergent boundary) 2.Increased volcanic activity (ash and dust) 3.Climate changes – cooler climate  Paleozoic Era Cambrian Period (541 – 488 mya): Explosion of life All existing phyla come into being at this time Classes of marine animals with definite skeleton are present during this period Ediacaran animals – soft-bodied that leads to the appearance Marks the appearance of Marine invertebrates -trilobites and brachiopods, as well as echinoderms and arthropods. Cambrian Period is known as the “Age of the Trilobites” Brachiopods Marine animals that resemble clams.  Jawless (agnathan) vertebrates – emerge during this time Haikouichthys ercaicunensis – have notochord, gill pouches, eyes, segmented musculature, and other features similar to the present larval lampreys. Conodonts – have teeth made of cellular bones.  Paleozoic Era Ordovician Period (488 – 444 mya): The 1st animals with bones appear, though dominant animals are still trilobites, brachiopods and corals Marine animals are either: Epifaunal – live on the surface of the seafloor Infaunal – burrowing types Sea stars and nautiloids – marine predators Agnathans – lack of jaw, being armored, and having no fins, survivors during this period Hagfishes and lampreys  Paleozoic Era Silurian Period (444 – 416 mya): Evolution of the jawed and finned marine vertebrates - gnathostomes Groups of arthropods that appeared during this period: Chelicerates – spiders, scorpions Mandibulates – millipedes and centipedes Wingless insects also appeared during this period. Small vascular plants (less than 10cm high) appeared. – with roots and vascular tissues Cooksonia – a vascular plant that lived during Silurian Coral reefs expand and land plants begin to colonize barren land.  Paleozoic Era Devonian (416 – 359 mya) - Age of the Fish Nautiloids – gave rise to ammonoids (shelled cephalopods) Dominant animal: fish Sarcopterygii – lobe-finned fishes Lungfishes and rhipidistians – sacopterygians Ichthyostegids – evolved from Sarcopterygii become the first terrestrial tetrapod Actinopterygii – ray-finned fishes Actinopterygians – ancestors of the modern teleosts.  Paleozoic Era Devonian (Age of the Fish) Plants become prominent Plants evolved from Chlorophyta (marine green alga) Mosses Liverworts tracheophytes Land plants diversified and ferns, club mosses, horsetails, and large trees Small plants have sporangia (spore-bearing structure)  Paleozoic Era Carboniferous Period (359-299 mya): Warmer climate allowed the development of swamp forests populated by horsetails, clubmosses, and ferns. Seeds protect the embryo from desiccation and to keep embryo nourished during development Anthracosaurs – classified as either amphibian or reptile First wing insect evolved – that diversified to dragonflies, orthopteroids, and hemipteroids.  Paleozoic Era Permian Period (299-251 mya): Last period of the Paleozoic Reptiles spread across continents. Anthracosaurs – gave rise to first amniotes (captorhinomorphs) that later gave rise to the synapsids and diapsids Synapsids – gave rise to the therapsids (mammal-like reptiles) Insects evolved to undergo complete metamorphosis including beetles, flies, caddisflies, and lepidopterans (moth and butterflies) MESOZOIC ERA (MIDDLE LIFE) (251-66 mya) – Events: 1. Pangaea broke up around the middle of this era. 2. Reptiles became the most abundant animals because of their ability to adapt to the drier climate of the Mesozoic Era. - Skin maintains body fluids - Embryos live in shells  Mesozoic Era The main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers. Pine Trees Flowering plants appeared during the END of this era. Mesozoic Era This era ended with a mass extinction event about 65 million years ago. Many groups of animals, including the dinosaurs disappeared suddenly at this time. Many scientists believe that this event was caused by a comet or asteroid colliding with the Earth.  Mesozoic Era – Mass Extinction Event Asteroid or Comet collides with Earth. Huge cloud of smoke and dust fills the air Blocks out sunlight Plants die Animals that eat plants die Animals that eat plant-eaters die. However, not all forms of life died during this event. Many animals that you see today are descendants from the survivors of this extinction event.  Mesozoic Era Triassic Period (251-199.6 mya): First dinosaurs appear First mammals- small rodents appear Life and fauna re-diversify First turtle fossil from this period Foraminiferans, modern corals, and bony fishes evolved Mollusk developed thick shells and spines Ichthyosaurus – marine reptiles with a dolphinlike appearance that gave birth to live young  Mesozoic Era Triassic Period (251-199.6 mya): two groups of diapsids evolved: Lepidosauromorphs – related to lizard Archosauromorphs - predators Pterosaurs – capable of powerful flight that later diversified into large flying vertebrates and small sparrows. Saurischia are carnivores, bipedal theropods, and herbivores, quadrupedal sauropods. Tyrannosaurus rex and Deinonychus – are theropods Apatosaurus – herbivores sauropods with a small head and long neck (such as Brontosaurus, Brachiosaurus, and Diplodocus)  Mesozoic Era Jurassic Period (201.3 – 145 mya): Dinosaurs flourish “Golden age of dinosaurs” First birds appear Gymnosperms such as cycads and conifers, including Ginkgo and giant ferns Cretaceous Period (145 – 66 mya): T-Rex develops First snakes and primates appear Deciduous trees and grasses common First flowering plants Mass extinction (K/T (Creataceous-Tertiary) extinction) marks the end of the Mesozoic Era, with the demise of dinosaurs and 25% of all marine life.  Cenozoic Era – Recent Life (66 mya – present) Began about 65 million years ago and continues today. Climate was warm and mild. Marine animals such as whales and dolphins evolved. Mammals began to increase and evolve adaptations that allowed them to live in many different environments – land, air and the sea. Grasses increased and provided a food source for grazing animals Many mountain ranges formed during the Cenozoic Era Alps in Europe and Himalayas in India; Rocky Mountains in the USA  Cenozoic Era Growth of these mountains may have helped to cool down the climate Ice Ages occurred late in the Cenozoic Era (Quaternary Period). As the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers. This era is sometimes called the “Age of Mammals”  Cenozoic Era Marine organisms examples: Algae, Mollusks, Fish and Mammals Land animal examples: Bats, Cats, Dogs, Cattle and Humans Humans are thought to have appeared around 3.5 million years ago (during the most recent period – Quaternary). Flowering plants were now the most common plant life. EPOCH – smallest segment of geologic time; characterized by distinctive organisms  Cenozoic Era Tertiary: First horses appear and tropical plants dominate (Paleocene) Grasses spread and whales, rhinos, elephants and other large mammals develop. Sea level rises and limestone deposits form. (Eocene) Dogs, cats, and apes appear (Oligocene) Horses, mastadons, camels, and tigers roam free. (Miocene) Hominids develop and the Grand Canyon forms (Pliocene) Quaternary: Modern humans develop and ice sheets are predominant- Ice age (Pleistocene) Holocene Humans flourish (Holocene)