History-of-Life-on-Earth.pdf

17/09/2024 Today's Objectives Identify the dates and sequence of the periods in the geologic Identify the major events i...

17/09/2024 Today's Objectives Identify the dates and sequence of the periods in the geologic Identify the major events in each time scale major period Describe the characteristics of the major groups of organisms present Identify types of fossils during a time period Describe the causes of mass extinctions. 1 2 What What is was the the age Earth of the like Earth? millions of years ago? 3 4 When we study the Earth’s age, we are also studying the fossil record and ultimately, the theory of evolution. The Earth is approximately 4.6 billion years old – a very big number ordinary humans can’t easily relate with, especially, the specific time frame when we appeared. 5 6 1  17/09/2024 When did life appear on Earth? When did life appear on Earth? Bedrock along the northeast coast of Hudson Bay, Canada, has the oldest rock on Earth. Early Earth was pummeled by Geologists estimate that Credit: Jonathan O'Neil https://www.nsf.gov/news/news_im asteroids and other celestial the Earth formed around ages.jsp?cntn_id=112299&org=NSF objects. Temperatures also 4.6 billion years ago. would have been very high (with water taking the form of Earth's oldest known rock is a gas, not a liquid). composed of the mineral amphibole, which contains abundant garnet, seen as large round "spots" in the rock. Credit: Jonathan O'Neil https://www.nsf.gov/news/news_ima ges.jsp?cntn_id=112299&org=NSF 7 8 When did life appear on Earth? The earliest fossil evidence of life The first life might have emerged during a break in the The earliest evidence of asteroid bombardment, life on Earth comes from between 4.4 and 4.0 billion fossils discovered in years ago, when it was cool Western Australia that enough for water to condense date back to about 3.5 into oceans. However, a second billion years ago. bombardment happened about 3.9 billion years ago. Image credit: "Stromatolite," by Didier Descouens, CC BY-SA 4.0. 9 10 11 12 2  17/09/2024 How might life have arisen? How might life have arisen? In the 1920s, both Oparin and Haldane thought that the early Earth had a separately proposed reducing atmosphere. Under these conditions, they what's now called the suggested that: Oparin-Haldane Simple inorganic molecules could have reacted (with hypothesis: that life on energy from lightning or the sun) to form building blocks. Earth could have arisen The building blocks could have combined in further step-by-step from non- reactions, forming larger, more complex molecules. living matter through a The polymers could have assembled into units or structures process of “gradual that were capable of sustaining and replicating themselves. chemical evolution.” Aleksandr Oparin J. B. S. Haldane 13 14 From inorganic compounds to building blocks From inorganic compounds to building blocks In 1953, Stanley Miller and Miller and Urey built a Harold Urey did an closed system containing a experiment to test Oparin heated pool of water and a and Haldane’s ideas. They mixture of gases that were found that organic thought to be abundant in molecules could be the atmosphere of early spontaneously produced earth H2O, NH3, CH4 and under reducing conditions H2. thought to resemble those Stanley Miller Harold Urey of early Earth. Image credit: "Miller and Urey's experiment," by CK-12 Foundation, CC BY-NC 3.0. 15 16 The Geologic Time It organizes Earth's history into Scale is a system that different sections based on major scientists use to events: describe the timing and mass extinctions relationships of events appearance of new life forms in Earth's history. significant environmental changes 17 18 3  17/09/2024 What is the significance The geologic time scale of the helps us understand geologic time scale? Earth's long history and how life evolved over time. 19 20 Geologic Time Scale 4 Epoch Era 2 Largest division of the geologic time scale; spans 3 Period Eon 1 hundreds to thousands of million of years ago (mya) 21 22 Division in an Era A division of that span time geologic history periods that of tens to hundreds spans no more of millions of years than one hundred million years 23 24 4  17/09/2024 The smallest division of the geologic time scale characterized by distinctive organisms 25 26 A BRIEF DESCRIPTION OF EARTH’S HISTORY PRECAMBRIAN Comprises about 88% or a total span of roughly 4.1 billion years. Hadean was considered the “chaotic eon”. (4.6 to 3.8 BYA) [Hades = “hell”] Hadean lasted for 800 years 27 28 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Earth’s surface was continually The Archean eon bombarded by meteorites and stretched from 3.8 to 2.5 the very hot mantle caused BYA. It lasted for 1.3 severe volcanism. billion years. Ocean and atmosphere were formed, and the core, as well as the crust, were stabilized. 29 30 5  17/09/2024 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Earth was probably warm. There was a profusion of The atmosphere contained volcanoes, the sky was mostly methane and little orange due to abundance to no oxygen. of methane, the sea was green because of iron and Most of the Earth was shorelines were marked covered with ocean. with stromatolites. Continent formation began. 31 32 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY The Proterozoic eon It was the time of great changes: stretched from 2.5 billion - Oxygenation of atmosphere to 542 million years. It - Origin and diversification of eukaryotic lasted for 1.9 billion years. life - Appearance of multicellular life - Motion of continental drift 33 34 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY PHANEROZOIC EON Paleozoic Era Consists of three eras: Many fossils were found in layers - Paleozoic of sedimentary rocks. - Mesozoic Marine invertebrate probably lived near the shores of shallow - Cenozoic water. Fossils of trilobites and brachiopods were found in the preserved rocks. 35 36 6  17/09/2024 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Paleozoic Era By the middle of the Paleozoic era, marine life had developed shells. The first animal to succeed in adapting itself to breath air was an amphibian that came out of the sea during the Devonian period. 37 38 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Paleozoic Era Paleozoic Era Marine life also Land plants also began to developed. develop. Clams and snails increased in number. Giant ferns and marsh plants Fish became more provided food to land animals abundant and showed a which increased in number. greater variety of form. 39 40 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Paleozoic Era Paleozoic Era The late Paleozoic era Toward the end of the Paleozoic showed appearance of era, the land climate changed. reptiles. Many kinds of plants grew and the remains of these plants formed the huge coal deposits. 41 42 7  17/09/2024 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Mesozoic Era Mesozoic Era The largest creatures that The early Mesozoic existed during this era era saw the formation were the dinosaurs. of the several Some dinosaurs were continents. carnivores and some were herbivores. 43 44 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY Mesozoic Era Mesozoic Era The fossils of the Toward the end of the Mesozoic biggest dinosaur were era, more continents broke up. found in Argentina Reptiles were the first true and was believed to terrestrial vertebrates existed be 130 ft long, 65 ft which flourished during this era. tall and weighed However, many reptile groups 170,000 lbs. became extinct. 45 46 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY CENOZOIC ERA CENOZOIC ERA Warm blooded animals and During this era, mountains primitive mammals, were uplifted and new life roamed the land. forms started appearing. Volcanic activity was also widespread, forming immense flows of lava and basalt. 47 48 8  17/09/2024 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY CENOZOIC ERA CENOZOIC ERA Fossils during this This era also era showed mammals with shared the tooth structures for development of specific diets, limb modern horse, structures for various postures, modern birds and increased brain and deciduous size. trees. 49 50 A BRIEF DESCRIPTION OF EARTH’S HISTORY A BRIEF DESCRIPTION OF EARTH’S HISTORY CENOZOIC ERA CENOZOIC ERA Toward the end of During this period, this era, glaciers humans left their marks covered the on land. Some of the Northern earliest record of hemisphere. humans were stone tools. 51 52 Mold fossils A fossil is a remnant or - are hollow impressions of a living trace of organisms of a thing in a rock. The mold reflects only past geologic age. Fossils are classified the shape and surface marking of the based on their organisms. formation. 53 54 9  17/09/2024 Petrified Fossil - result from permineralization, the Cast fossils replacement of once-living matter by minerals. - are created when mold Solutions containing fossils get filled with mineral. silicates, carbonates, iron The minerals harden and form or other minerals seep into the gaps and spaces a replica of the original fossil. between the cells, first encasing the cells and eventually replacing the cells themselves. 55 56 Carbon Film Fossil True form fossils - When an organism dies and is - are the entire animals buried in sediment, the or plants trapped and materials that make the preserved in ice, tar, or other organism break down and material, such as remains of eventually only the carbon prehistoric elephants or remains. The thin layer of mammoths that were frozen carbon left behind can show an in the Arctic tundra of organism's delicate parts like Siberia and Alaska. leaves or plant 57 58 Trace fossils or ichnofossils - are impressions on rocks that showed various activities. Fossils can be footprints, eggs, droppings, or nest of animals. 59 60 10  17/09/2024 How do scientists Dating Fossils determine the Relative Dating Absolute Dating geologic time? 61 62 Dating Fossils 1. RELATIVE DATING I. Based upon the study of layer of rocks II. Does not tell the exact age: only compare fossils as older or younger, depends on their position in rock layer III. Fossils in the uppermost rock layer/ strata are younger while those in the lowermost deposition are oldest 63 64 Dating Fossils Relative Dating – places How Relative Age is Determined? events or rocks in their I. Law of Superposition: if a layer of rock is chronological sequence undisturbed, the fossils found on upper or order of occurrence layers are younger than those found in lower layers of rocks without knowing their II. However, because the Earth is active, actual age. rocks move and may disturb the layer making this process not highly accurate 65 66 11  17/09/2024 Dating Fossils Principle of Superposition Rules of Relative – In the sequence of Dating sedimentary rocks, the layer at the bottom of the A. LAW OF sequence is the oldest, SUPERPOSITION: Sedimentary layers are and the successively deposited in a specific higher levels are time- youngest rocks on successively younger. top, oldest rocks at the bottom 67 68 RELATIVE & ABSOLUTE DATING Dating Fossils Rules of Relative Dating B. LAW OF ORIGINAL HORIZONTALITY: Deposition of rocks happen horizontally- tilting, folding or breaking happened recently 69 70 Principle of Original Horizontality Dating Fossils Rules of Relative – Sedimentary rocks are Dating deposited as horizontal or nearly horizontal layers. Any C. LAW OF CROSS-CUTTING RELATIONSHIPS: If an deviation from horizontality igneous intrusion or a fault indicates that deformation cuts through existing rocks, occurs after the deposition. the intrusion/fault is YOUNGER than the rock it cuts through 71 72 12  17/09/2024 Dating Fossils Rules of Relative Dating D. LAW OF LATERAL CONTINUITY: Layers of sedimentary rocks extend sideways in the same order. 73 74 Dating Fossils Dating Fossils Rules of Relative Rules of Relative Dating Dating E. LAW OF INCLUSION: If F. LAW OF FAUNAL rocks or rock fragments are SUCCESSION: Fossil included within another groups are succeeded by rock layer, the rock other fossil groups fragments must be older through time. than the rock layer where they were embedded. 75 76 Dating Fossils Thank you for listening! 2. ABSOLUTE DATING Determines the actual age of the fossil Through radiometric dating, using radioactive isotopes carbon-14 and potassium-40 Considers the half-life or the time it takes for half of the atoms of the radioactive element to decay The decay products of radioactive isotopes are stable atoms. 77 78 13