Fossils and the History of Life on Earth PDF

MODULE 12 LESSON 1 : What are Index Fossils? FOSSILS  FOSSILS The word ‘fossil’ comes from the Latin word fossus, which means ‘dug up’. - This refers to the fact that Fossils are the remains of ancient species or past life that have been preserved, or evidence of their re...

MODULE 12 LESSON 1 : What are Index Fossils? FOSSILS  FOSSILS The word ‘fossil’ comes from the Latin word fossus, which means ‘dug up’. - This refers to the fact that Fossils are the remains of ancient species or past life that have been preserved, or evidence of their remains. - It can be body fossils which are remains of the organism itself, or trace fossils, such as burrows, tracks, or other evidence of activity. FOSSIL RECORD The fossil record shows us that present-day life forms evolved from earlier different life forms. It shows us that the first organisms on Earth were simple bacteria that dominated the Earth for several billion years.  CLUES FROM FOSSILS Fossils provide crucial evidence regarding the history of life on Earth. They also offer insights into past climates, tectonic movements, and significant geological events. One key piece of information that fossils reveal is whether an environment was marine (underwater) or terrestrial (on land). When considered alongside rock characteristics, fossils can indicate whether the water was shallow or deep and whether sedimentation occurred slowly or rapidly. Additionally, fossils can shed light on historical climates. For instance, plant fossils and coal deposits have been discovered in Antarctica. While Antarctica is currently frozen, it must have had a much warmer climate in the past.  INDEX FOSSILS are the remains of ancient INDEX FOSSILS species that have been preserved, or evidence of their remains. Index fossils are the preserved remains of particular species found within layers of sedimentary rock. They are easily identifiable by their shape and existed for a relatively brief geological period or disappeared during a known extinction event. Typically, index fossils come from marine organisms, as the conditions for their preservation are more favorable, and ocean- dwelling species tend to be widespread. FOSSILS FORM IN FIVE WAYS: Preserved Remains Permineralization. Molds and Casts Replacement Compression 1. PRESERVED REMAINS The rarest form of fossilization is the preservation of original skeletal material and even soft tissue. These are fossils where the organism’s actual remains are preserved without much alteration. This can happen through freezing, amber, or tar pits. For example, insects have been preserved perfectly in amber, which is ancient tree sap. Several mammoths and even a Neanderthal hunter have been discovered frozen in glaciers. SUMMARY: the organism's soft tissues and bones can Example: An Insect stay intact for thousands or millions of years. preserved in amber 2. PERMINERALIZATION The most common method of fossilization is permineralization. After a bone, wood fragment, or shell is buried in sediment, it may be exposed to mineral-rich water that moves through the sediment. This water will deposit minerals into empty spaces, producing a fossil. Fossil dinosaur bones, petrified wood, and many marine fossils were formed by permineralization. SUMMARY: Water with minerals flows into tiny holes in bones or wood. The minerals harden and fill up these Example: Petrified wood empty spaces, turning the remains into rock-like fossils with lots of detail.  3. MOLDS AND CASTS When an organism is buried in sediment and then decomposes, the original bone or shell dissolves away, leaving behind a space in the shape of the shell or bone. This depression is called mold. Later the space may be filled with other sediments to form a matching cast in the shape of the original organism. Many mollusks (clams, snails, octopi, and squid) are commonly found as molds and casts because their shells dissolve easily. SUMMARY: When an organism buried in sediment breaks down, it leaves a hole shaped like itself, called a mold. If the Example: cast and mold mold later fills up with minerals, it makes a cast of the of an ammonite fossil original shape. 4. REPLACEMENT This process occurs when groundwater rich in minerals flows through the sediment, depositing minerals into the spaces left by decaying organisms. Over time, the original material is completely replaced, leaving behind a fossilized replica. For example, shells that were originally calcite may be replaced by dolomite, quartz, or pyrite. If quartz fossils are surrounded by a calcite matrix, the calcite can be dissolved away by acid, leaving behind an exquisitely preserved quartz fossil. Example: SUMMARY: The original shell or bone dissolves away and is pyritized ammonite replaced by a different mineral. 5. COMPRESSION Some fossils form when their remains are compressed by high pressure. This can leave behind a dark imprint on the fossil. Compression fossils are formed when organic material is compressed by overlying sediments, causing it to flatten and preserve impressions. This process occurs over millions of years, as heat and pressure cement the sediments together. The resulting fossils provide a detailed record of ancient life, including leaves, ferns, insects, and even dinosaur footprints. SUMMARY: the organism's soft tissues and bones can Example: compression stay intact for thousands or millions of years. fossil of a fern EXCEPTIONAL PRESERVATION Some rock beds have produced exceptional fossils. Fossils from these beds may show evidence of soft body parts that are not normally preserved. Two of the most famous examples of soft organism preservation are the Burgess Shale in Canada and the Solnhofen Limestone in Germany Archaeopteryx was an early bird. Anomalocaris was an enormous predator (one meter long) that lived 500 million years ago.  FOSSILS INDEX FOSSILS LIVING FOSSILS  INDEX FOSSILS Index fossils are widespread but only existed for a relatively brief period. When a particular index fossil is found, the relative age of the bed is immediately known. Ammonites, trilobites, and graptolites are often used as index fossils, as are various microfossils, or fossils of microscopic organisms. Ammonites  LIVING FOSSILS Living fossils are organisms that have existed for a tremendously long period without changing very much at all. For example, the Lingulata brachiopods have existed from the Cambrian period to the present, a period of over 500 million years. Lingulata brachiopods CORRELATION BY INDEX FOSSILS To be considered an index fossil, it must meet 3 criteria: 1. The fossilized organism must be easily recognizable. It must be easy to ID and look unique. 2. The fossils must be geographically widespread or found over large areas so that we can use them to match layers separated by huge distances. 3. The fossil must have lived for only a short time so that it appears in only a horizontal layer of sedimentary rocks.  CORRELATION BY INDEX FOSSILS The diagram shows several rocks outcrops separated by large distances. In each outcrop are several fossils. Which of the fossils shown is an index fossil?  CORRELATION BY INDEX FOSSILS Which of the fossils shown is an index fossil? Based on the 3 criteria shown earlier, This is an Index fossil We can eliminate “Fossil 1” because it shows up in multiple layers in the same outcrop. We can eliminate “Fossil 2” 1) Found over a large area because it shows up in multiple layers in Column 2. 2) Existed for a short time We can eliminate “Fossil 3” because it is only in one layer in one outcrop. USING INDEX FOSSILS TO CORRELATE ROCK LAYER USING INDEX FOSSILS TO CORRELATE ROCK LAYER We can use index fossils and key beds to correlate or match rock layers with the same age. By doing this, we can then place other layers of rocks in order of their relative ages to find the oldest and youngest rocks in a series of outcrops. USING INDEX FOSSILS TO CORRELATE ROCK LAYER Example: Examine the outcrop and determine which layers are the oldest and youngest? To find the oldest and youngest layers in the entire diagram, we first must correlate the three outcrops. We can do this by using the trilobite index fossil because it appears in all three outcrops. USING INDEX FOSSILS TO CORRELATE ROCK LAYER By correlating them, we now know that layers A, K, and Q are of the same age. So, to find the oldest rocks we look below them, and to find the youngest rocks we look above them. If we create a chart building our way up and down by looking directly above and below each layer, we will find the top and bottom. THANK YOU! May lesson 2 pa... History of Earth’s Life Forms An Introduction to Geologic Time Scale Introduction Charles Doolittle Walcott Charles Doolittle Walcott, was a paleontologist, a scientist who studies past life on Earth. He is often noted for his discovery of the Burgess Shale fossils in Canada in the early twentieth century. After his time as USGS Director, he then served as Secretary of the Smithsonian Institution until his death in 1927.  He was searching for fossils. Riding on horseback, he was making his way down a mountain trail when he noticed something on the ground. He stopped to pick it up. It was a fossil! One of the organisms preserved in the fossils had a soft body like a worm, five eyes, and a long nose like a vacuum cleaner hose. FIGURE 2:1. OPABINIA REGALIS , A BIZARRE ANIMAL WITH FIVE EYES LIVED DURING THE CAMBRIAN. The organisms in Walcott’s fossils lived during a time of geologic history known as the Cambrian. The Cambrian period began about 540 million years ago. It marked the beginning of the Phanerozoic Eon. It also marked the beginning of many new and complex life forms appearing on Earth. In fact, the term Phanerozoi, means “time of well-displayed life.” We still live today in the Phanerozoic Eon. However, life on Earth is very different today than it was 540 million years ago. Earth’ Diversity Biological diversity, There are over 1 million species of plants and animals known or biodiversity, to be currently alive on Earth. Look around you and notice refers to all of the that the organisms on this planet have incredible variation. variety of life that exists on Earth. One of the most remarkable features of Earth’s organisms is Biodiversity can be their ability to survive in their specific environments. described and measured at three Other organisms have special features that help them hunt different levels: for food or avoid being the food of another organism. species, genetic, and ecosystem diversity. Some plants have poisonous or foul-tasting substances in them that keep animals from eating them.  Phanerozoic Eon The Phanerozoic Eon is the current and the latest of the four geologic eons in the Earth's geologic time scale, covering the time period from about 540 million years ago to the present. This eon is known for abundant animal and plant life has proliferated, diversified, and colonized various niches on the Earth's surface. The Phanerozoic eon is divided into three: Palaeozoic, Mesozoic, and Cenozoic eras. Cenozoic Era (65 Million Years ago - Now) Cenozoic Era (65 Million Years ago - Now) Mesozoic Era (245 Million Years Ago) Paleozoic Era (544 Million Years Ago)  Phanerozoic Eon (summary) Cenozoic Era (65 Million Years ago - Now This is the most recent among the eras of the Phanerozoic Era; this era marks the age of mammals and the first human evolution. Mesozoic Era (245 Million Years Ago) This era marks the beginning of dinosaurs, mammals, birds, and plants due to mass extinction. Paleozoic Era (544 Million Years Ago) The explosion of diverse marine life and the largest mass extinction of marine organisms Paleozoic Era (544 Million Years Ago) Permian Period (298.9 MYA) Pennsylvanian Period (323.2 MYA) Mississippian Period (358.9 MYA) Devonian Period (419.2 MYA) Silurian Period (443.8 MYA) Ordovician Period (485.4 MYA) Cambrian Period (541.0 MYA) Mesozoic Era (245 Million Years Ago) Cretaceous Period (145.0 MYA) Jurassic Period (201.3 MYA) Triassic Period (251.9 MYA)  Holocene Period (0.01 MYA) Cenozoic Era (65 Million Years ago Pleistocene Period (2.6 MYA) Pliocene Period (5.3 MYA) Miocene Period (23.0 MYA) Oligocene Period (33.9 MYA) Eocene Period (56.0 MYA) Paleocene Period (66.0 MYA) Thank You For Listening