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Introduction to Geology |
Chapter 13 - Evolution of Life Through Earth History |
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1. Review the origin of fossils and the theory of evolution. 2. Review early (precambrian) Earth history and cell theory. 3. Explain the appearance of skeletal shell remains in the Cambrian Period. 4. Discuss the evolution of plant and animal life as revealed in the Paleozoic fossil record. 5. Examine the large mass extinctions as preserved in the fossil record. 6. Review the changes in life and landscapes in the transition to the Mesozoic Era. 7. Review the Cretaceous-Tertiary boundary. 8. Discuss the changes in life forms through the Cenozoic Era. 9. Review current thought on the evolution of humans and the rise of modern civilization. |
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| Keywords and Essential Concepts |
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1. Review the origin of fossils and the theory of evolution. geologic time scale—a systematic and chronological organization of time related to the history of the Earth and universe used by scientists (geologists, paleontologists, astronomers) to describe the timing and relationships between events that have occurred during the history of the Earth. paleontology—the scientific study of life forms existing in former geologic periods, as represented by their fossils; the science involves reconstructing the physical characteristics of organisms, life habits, and the environments where they lived (paleoecology). fossil—A remnant or trace of an organism of a some earlier geologic age, such as a skeleton or leaf imprint, embedded and preserved in the earth's crust. fossil record—term used by paleontologists (scientists who study paleontology) to refer to the total number of fossils that have been discovered, as well as to the information derived from them. fossilization—the processes that turn plant or animal remains to stone. trace fossil—a fossil impression of a footprint, trail, burrow, or other trace of an animal rather than of the animal itself.
Theory of Evolution and the origin of life on Earth evolution—gradual development of "something" from a simple to a more complex form; in biology (natural sciences), evolution refers to the processes by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the Earth. * The Theory of Evolution has itself "evolved" over time, with new knowledge being added and old ideas being challenged or revised. * Knowledge and concepts related to evolution have roots that extend back to early civilizations around the world. * Concepts of evolution are fundamental to all modern sciences—without evolution, science and history would make no sense.
Key developments in understanding the origin of life on Earth Carl Linnaeus—a Swedish botanist, physician, and zoologist (lived 1707-1778), who laid the foundations for the modern scheme of binomial nomenclature and considered a founder of modern taxonomy and ecology. * Linnaeus's system of classification grouped organisms based on shared characteristics. Modern taxonomy attempts to connect taxonomy to the evolutionary framework of shared common ancestors ("the evolutionary tree of life"). Charles Darwin—scientist/explorer credited with presenting the first published work dedicated to "natural selection" (fundamental to evolution theory) in his book "Origin of Species" (1859)—a compilation of his observations and thoughts about plants, animals, and fossils initially gathered during a five-year voyage around the world studying nature onboard the Royal Navy ship, the HMS Beagle. Note: Darwin did not release his research for nearly two decades after the expedition largely out of fear of repression, but his work arguably became one of the world's greatest scientific works of modern times. Gregor Johann Mendel—an Austrian geneticist/researcher (and monk) who conducted experimental research on creating hybrids of garden peas. In 1865 and 1866, he published his research on how hereditary characteristics are passed from parent organisms to their offspring. Mendelian theory is fundamental to much of what is known about modern genetics theory. * Over the past two centuries, many scientific discoveries about the nature of biochemistry, cell structure and processes, and development of analytical methods equipment (such as microscopes and chromatography) have contributed to the modern knowledge base fundamental to understanding genetic evolution. In 1951, James Watson and Francis Crick discovered and reported the double helical structure of the DNA molecule. Today, the entire genetic structure of human DNA has been mapped and reported via the Human Genome Project.
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| 2. Review early (precambrian) Earth history and cell theory. *Note about geologic time dates: new data is constantly helping to resolve geologic time periods. For instance, new locations are being found where more detailed data about rock sequences preserving time boundaries can be observed and radiometric ages can be determined Scientific data is reviewed by the International Commission on Stratigraphy (ICS) for recommended changes to the latest version of a global geologic time scale.
Banded-iron formations (BIF)—sedimentary mineral deposits consisting of alternating beds of iron-rich minerals (mostly hematite) and silica-rich layers (chert or quartz) formed about 3.0 to 1.8 billion years ago. BIFs are the major source of the world's iron ore and are found preserved on all major continental shield regions. Theory suggests BIF are associated with the capture of oxygen released by photosynthetic processes by iron dissolved in ancient ocean water. Once nearly all the free iron was consumed in seawater, oxygen could gradually accumulate in the atmosphere, allowing an ozone layer to form. Cells are divided into two main classes: prokaryotic cells and eukaryotic cells prokaryotic cells—(bacteria and related organisms) lack a "nucleus" (or nuclear envelope) and are generally smaller, structurally simpler, and less complex genomes (genetic material) than eukaryotic cells. eukaryotic cells—have contain cytoplasmic organelles or a cytoskeleton, and contain a nucleus in which the genetic material is separated from the cytoplasm. Eukaryotes include fungi, plants, animals, and some unicellular organisms. Eukaryotic cells are capable of sexual reproduction. *The same basic molecular processes are involved in the lives of both prokaryotes and eukaryotes, suggesting that all present-day cells are descendent from a single primordial ancestor. endosymbiosis—theory that suggests organelles evolved in eukaryotic cells occurred when one type of cell became incorporated into another type of cell, creating a symbiotic relationship to the benefit of both (such as chloroplasts in plants, and mitochondria in animals). viruses—"non-living" organic structures capable of genetic self replication that are not classified as cells and are neither unicellular nor multicellular organisms; viruses lack a metabolic system and are dependent on the host cells that they infect to reproduce. stromatolite—a mound of calcareous sediment built up of layers of lime-secreting cyanobacteria (blue-green bacterial, algae and other "simple" eukaryotic life forms) that trap sediment, creating layers accumulations. Stromatolites are found in Precambrian rocks and represent some of the earliest known fossils. Stromatolites are known from all geologic time periods and are still occurring today, with exceptional examples resembling ancient life forms still being formed today in places like Shark Bay, Australia. metazoans—multicellular animals having cells differentiated into tissues and organs and usually a digestive cavity and nervous system. Metazoans appeared on earth in Late Precambrian time (late Proterozoic Era) consisting of cells in that with growth would differentiated into unique tissue or organs used for special purposes, such a locomotion, feeding, reproduction, respiration, sensing the environment, etc. * Late Precambrian life forms have been discovered, but fossils from this period are scarce and poorly preserved because they did not contain hard parts (skeletons, teeth, etc.). Impression is sediments (tracks, trails, resting and feeding traces) and rare body impressions have been found. Ediacaran fauna—one of the earliest known occurrence of multicellular animals is the, first named for the Ediacaran hills of South Australia where they were first discovered Traces of Ediacaran fauna has been found worldwide in sedimentary rocks of 635 to 542 million years (very late Precambrian age and consisted of frond- and tube-shaped, soft-body organisms, mostly sessile life forms (sessile meaning attached to the seabed). Many of the fossils from this time period match "families"or "classes" of organisms found on Earth today (segmented worms, jellyfish, chordates, and other invertebrates).
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| 3. Explain the appearance of skeletal shell remains in the Cambrian Period. Cambrian Period—the first geological period of the Paleozoic Era, lasting from about 543 to 488. "Cambrian Explosion"—Evidence in the fossil record shows that all major phyla were established in the transition from latest Precambrian to Early Cambrian time (about 700 to 540 million years ago. The cause of this radiation from earlier metazoan life forms is uncertain, but it may have been driven by global climate changes (hot to cold cycles) and the establishment of micro habitats (niches) which allowed species to evolve separately from common ancestors. In this time, chitonous and calcareous shells and exoskeletons appear. Many organisms have eyes, legs (pods), spinal chords, segmented body plans, and other unique body parts and characteristics. Representatives of all phyla from the Cambrian Explosion still exist in the world today. invertebrate—an animal lacking a "backbone," such as an arthropod, mollusk, annelid worm, coelenterate, echinoderm, and many others. The classification of invertebrates constitute a "fabricated" division of the animal kingdom, comprising about 95 percent of animal species and about 30 different "known" phyla. *By the end of the Cambrian Period several groups of invertebrates were well established in shallow marine environments, perhaps most notably were trilobites, brachiopods, crinoids, bryozoans, sponges, and gastropods are locally common fossils preserved in Cambrian sedimentary rocks.
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| 4. Discuss the evolution of plant and animal life as revealed in the Paleozoic fossil record. Paleozoic—the era of geologic time spanning about 543 to 248 million years ago. The Paleozoic Era follows the Precambrian Era and precedes the Mesozoic Era. The term also applies to rocks that formed and accumulated in that time period. Highlights of the Paleozoic Era Cambrian Period (543-490 million years): at the beginning of the Cambrian Period the combination of tectonic forces and erosion of the landscape allowed shallow seas to gradually cover much of North America. Shallow seas covered most of what is now the Great Basin, Rocky Mountains, and Great Plains in the west, and the East Coast, Appalachian region and most of the Midwest. The seas withdrew at the end of Cambrian time, but what was left behind was a blanket of Cambrian sedimentary rocks, collectively called the Sauk Sequence. The base of the Sauk Sequence rests on an eroded surface of ancient Precambrian-age (mostly metamorphic and igneous rocks) on a surface called the Great Unconformity. The Great Unconformity is exposed in many places throughout the western United States, and is particularly well known from exposures in the base of the Grand Canyon above the Inner Gorge). After a long period of exposure and erosion... the seas once again flooded across much of North America through much of the Ordovician Period. Deposition of sediments during this marine transgression resulted in the Tippecanoe Sequence which rests unconformably on top of the Sauk Sequence. However, when the seas returned (millions of years later) life in the oceans had significantly change. Ordovician Period (490-443 million years): Trilobites no longer dominated the fossil record, but other life forms began to dominate the shallow marine environment. Corals (unrelated to modern varieties), crinoids, cephalopods, brachiopods, bryozoans and other fossils with calcareous skeletons dominate the fossil record (because of their ability to survived burial and fossilization processes). Rare early examples of fish and land plants have been discovered in Ordovician age sedimentary rocks. Silurian Period (443-417 million years): Few rocks of Silurian age are preserved in North America's fossil record (New York and Michigan are notable exceptions). The fossil record shows that the Silurian world was dominated by marine invertebrates, but the first fish-like chordates appear. Land plants began to flourish, allowing the first animals to emerge onto dry land (including insects and scorpions).
Devonian Period (417 to 354million years): On land, free-sporing vascular plants adapted and spread across the landscape, allowing the first forests to cover the continents. By the middle of the Devonian several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Terrestrial arthropods began to flourish. In the marine world, early ray-finned, lobe-finned bony fish, and sharks appear in the fossil record. The first ammonoid mollusks appeared. Holdover families of marine invertebrates from earlier times persisted, including trilobites, brachiopods, cephalopods, and reef-forming corals remained common. Mississippian and Pennsylvanian Periods: These periods are also collectively called the Carboniferous Period (354 to 290 million years ago) because great quantities of coal are preserved in rocks of these ages. Great coastal forests and swamplands covered much of North America. Amphibians became the dominant land vertebrates. Descendent from amphibian ancestors, reptiles evolved and became the first terrestrial vertebrates. With the abundance of vegetation on land, arthropods flourish, including species of insects that are much larger than any found on Earth today. Toward the end of the Carboniferous, glaciation cycles caused repetitious rise and fall in sea levels. The Appalachian and Ouachita Mountain systems also began to develop. Permian Period (290 to 248 million years): The last period of the Paleozoic Era was a time of colossal changes. All the continents of the world combined to form the supercontinent of Pangaea. In the fossil record, a group of tetrapods (four legged animals with backbones) called amniotes appeared, capable of producing are a group of tetrapods (four-limbed animals with backbones or spinal columns) that have a terrestrially adapted eggs. All modern land species are descendant from a common ancestral group of amniotes. During the Permian, the expansive forests that existed during the Carboniferous disappeared, and vast desert regions covered the continental interior. Reptiles adapted and flourished in the more arid environment. Great reef tracks developed in the Texas and New Mexico region. The end of the Permian Period (and Paleozoic Era) is marked by the greatest mass extinction in Earth history.
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| 5. Examine the large mass extinctions as preserved in the fossil record. extinction—the state or process of a species, family, or larger group being or becoming extinct (ceasing to exist). * Extensive studies of microfossils in deep well cores extracted from around the world show that the appearance and disappearance (extinction) of species has happened continuously through geologic time, but the rate is not constant. *As climates and landscapes change, new species evolve to fit ever changing ecological niches, older species fade away. mass extinction—an episode or event in earth history where large numbers of species vanish from the fossil record. The causes of mass extinctions are debated, but are linked to possible global climate changes associated with asteroid impacts, massive volcanism episodes, onset of ice ages, or a combination of effects that affect environments globally.
*Current estimates are that 90 percent of all species that have ever lived on Earth are now extinct. However, the rate of extinction has not been constant. At least five times in the last 500 million years, as much as about 50 to 90 percent of all species on Earth have disappeared in very short periods of geologic time. * The greatest extinction event occur at the end of the Permian Period (about 250 million years ago). Most families of organisms that existed in the Paleozoic Era vanished. This occurred during the assembly and breakup of the supercontinent Pangaea. Great amount of volcanism are known from that period with the rifting and opening of the Atlantic Ocean basin, however, other causes, such as glaciation, ocean circulation collapse, or asteroid or comet impacts, extraterrestrial radiation events, and others have been suggested. *Great extinction events created opportunity for new life-forms to emerge. For instance, dinosaurs appeared after the mass extinction at the end of the Permian Period (about 250 million years ago). * Perhaps the most studied extinction event has been the Cretaceous-Tertiary Boundary where strong evidence suggests at least one asteroid collided with earth in the vicinity of the Yucatan Peninsula in Mexico (about 65 million years ago). This extinction killed off the dinosaurs and many other families of organism that lived in the oceans. However, the catastrophe made room for mammals to rapidly diversify and evolve. *Many scientists believe evidence suggests that a sixth mass extinction is under way. Global climate change and the expansion of human activity are to blame. Some estimates suggest that human activities such as land clearing, pollution, and over fishing may have drive more than half of the world's marine and land species to extinction within the next century. |
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| 6. Review the changes in life and landscapes in the transition to the Mesozoic Era. Mesozoic Era—the era between the Paleozoic and Cenozoic eras, comprising the Triassic, Jurassic, and Cretaceous periods; commonly referred to as the "Age of Reptiles." Triassic Period (248 to 206 million years): Following the great extinction event at the end of the Permian Period, life on Earth gradually reestablished itself both on land and in the oceans. Scleractinians (modern corals) replaced earlier forms as dominant reef-forming organisms. On land, reptilian therapsids and archosaurs became the dominant vertebrates. New groups evolved in the middle to late Triassic Period including the first dinosaurs, mammals, and flying vertebrates (pterosaurs) but these families did not flourish until another global extinction event at the close of Triassic time. During the middle Triassic, the supercontinent of Pangaea began to rift apart into separate landmasses, Laurasia to the north and Gondwana to the south. With the breakup of Pangaea, terrestrial climates gradually change from mostly hot and dry to more humid condition. Another mass extinction in the fossil record marks the end of the Triassic Period. Jurassic Period (206 to 144 million years): The cause of the mass extinction at the end of Triassic is still unclear, but evidence shows that it was rapid and massive amounts of volcanism was taking place with the ongoing breakup of Pangaea. With other life forms out of the way, dinosaurs adapted and diversified into a wide variety of groups. Although pterosaurs were the dominant flying vertebrates during the Jurassic Periods, the first birds appeared having evolved from a branch of theropod dinosaurs. Small mammals appear in the fossil record during the Jurassic, but remained insignificant compared to dinosaurs that dominated the landscape. Marine reptiles including ichthyosaurs and plesiosaurs dominated the oceans. Cretaceous Period (144 to 65.5 million years): During the Cretaceous Period the Earth was relatively warm compared to the world today. There were no glaciers on the planet and sealevel was as much as 200 feet higher that today. Fossils of warm-water organisms are found in rocks that are arctic regions today. The dinosaurs that survived into the Cretaceous Period diversified and evolved into many unusual forms. Large marine reptiles called Mosasaurs were the dominant organism in the ocean. Sediments deposited in shallow sea flooding onto the continents had an abundance of ammonites—squid-like organisms that had calcareous shells similar to modern nautilus species. Cretaceous gets its name for "Creta"—latin for the word chalk. The shallow warm seas of the Cretaceous Period were locations where the calcareous skeletal remains of planktonic organisms called coccoliths accumulated, forming great accumulations of chalk, such as exposed in the Great Cliffs of Dover, England. In many places in the equatorial realm oyster-like organism called rudists form great reefs. Flowering plants also first appear in the fossil record, birds and mammals existed in Cretaceous time but were insignificant compared to flying non-avian pterosaurs.
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| 7. Review the Cretaceous-Tertiary boundary. The Cretaceous-Tertiary boundary is one of the most investigated mass extinction event. It is has been well investigated partly because it is the youngest of the large extinctions that totally changed the nature of life on earth. * The "K/T event" is believe to have been caused by a massive asteroid impact in the Yucatan region of Mexico, although other possible sites of large impacts are being considered. What is known is that all species of dinosaurs on land, and marine reptiles and ammonites in the marine realm vanished. * The asteroid impact and following shock waves, monstrous tsunamis, firestorms, ash and gas clouds, and following global winter-like condition caused ecosystem collapse in both the food web of the oceans and on land. * All species that exist today are descendent of the few species that survived the global catastrophe... small mammals, birds, invertebrates, reptiles, amphibians, fish and other surviving groups had evolutionary advantages that allowed them to survive. With the dinosaurs, pterosaurs, large swimming reptiles and other large animals of the Cretaceous Period out of the way, the surviving species proliferated and moved into empty and new niches that allowed them to prosper and diversify.
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8. Discuss the changes in life forms through the Cenozoic Era.
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9. Review current thought on the evolution of humans and the rise of modern civilization.
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(Selected sources) The Origin and Evolution of Cells: http://www.ncbi.nlm.nih.gov/books/NBK9841/) What is a cell? National Center for Biotechnology Information website: http://www.ncbi.nlm.nih.gov/About/primer/genetics_cell.html Moodie, R.L., 1931, Geologic succession of life in Kentucky: in Paleontology of Kentucky, R. L. Jillson, ed., Kentucky Geological Survey and University of Kentucky (online at http://www.uky.edu/OtherOrgs/KPS/poky/indexpoky.htm). Sloss, L.L., 1964, Tectonic Cycles of the North American Craton: in D.F. Merriam, ed., Symposium on cyclic sedimentation: Kansas Geological Survey, Bulletin 169, pp. 449-459. Stoffer, P.W., Messina, P., Chamberlain, J.A., Jr., Terry ,D.O., Jr, 2001,The Cretaceous-Tertiary Boundary Interval in Badlands National Park, South Dakota: U.S. Geological Survey Open-File Report 01-056 (http://geopubs.wr.usgs.gov/open-file/of01-056/) |
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Quiz Questions |
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