Geology Earth History lecture_notes Roy Mod

The History of Life on Earth: 

The History of Life on Earth Geology for Grades 4 -8

Early Attempts at Earth’s Dating: 

Early Attempts at Earth’s Dating 17 th century - Counting generations Earth created on October 23, 4004 BC 18 th century – Principle of Uniformity Processes that could serve as geological clock: Operating since earth began Uniform (or be able to average over time) Measurable 19 th century – finding geological clock Processes explored were the rates of: Salt added to ocean Sediment deposition (20 million – 1500 million yrs) Cooling of earth (20 – 40 million years)

Modern Techniques for Dating the Earth: 

Modern Techniques for Dating the Earth Radiometric age 4.5 billion years Determines age of rocks by measuring radioactive decay of unstable elements Rate of radioactive decay constant for radioisotope Geomagnetic time scale Based on magnetic orientation of magnetic minerals Established from magnetic field reversals during last 6 million years

Arranging events in order: 

Arranging events in order Principle of uniformity Today’s geologic features were formed in the past by the same geologic processes observed today Principle of original horizontality Applies to sedimentary rocks On a large scale, sediments are deposited in flat-lying layers Any non-horizontal layers have been subjected to deformation forces

Re-Arranging Continents: 

Re-Arranging Continents Plate Tectonic – Continental Drift describes the large scale motions of Earth's lithosphere builds on the concepts of continental drift tectonic plates are able to move because the Earth's lithosphere has a higher strength and lower density than the underlying layers

More principles: 

More principles Principle of superposition Sedimentary rocks on the bottom were usually deposited first Exception: layers turned over by deforming forces Principle of crosscutting relationships Any geologic feature that cuts across or intrudes into a rock mass must be younger than the rock mass Concerns relationships between igneous, metamorphic and sedimentary rock Also applies to faults and folds

Shifting erosion and deposition sites : 

Shifting erosion and deposition sites Erosion and deposition processes vary over time and location Unconformity A time break in the rock record Angular unconformity Bedding planes above and below unconformity are not parallel Processes include tilting or folding, followed by erosion and deposition Application of numerous principles needed to unravel complex sequences

Fossils : 

Fossils Any evidence of former life Can include actual or altered remains of plants and animals Also less direct evidence such as leaf imprints, dinosaur footprints and bat droppings Knowledge of rocks containing fossils can provide clues about their origins

Early ideas about fossils: 

Early ideas about fossils Herodotus Realized fossil shells were remnants of earlier living organisms Aristotle Believed fossils formed inside rocks Early 1800’s True nature of fossils became widely accepted Paleontology The science of discovering fossils Versus archeology The study of past human life from artifacts Discovery of Burgess Shale

Types of Fossils : 

Types of Fossils Preserved whole organisms Must be protected from scavengers and decomposers Freezing Entombment Preserved hard parts More easily preserved Composed of calcium carbonate, calcium phosphate, silica, chitin Shells bone, teeth, exoskeleton, spores Insects in Amber

Types of Fossils : 

Types of Fossils Traces, Molds, Casts Carbon trace Does not preserve detail of internal structure Good idea of shape Molds Shell may dissolve but leave mold in rock Cast Sediment may fill mold

Types of Fossils : 

Types of Fossils Petrified fossils Formed by modification of original chemicals Mineralization Filling of pore spaces with calcium carbonate, silica, pyrite Replacement Dissolving original material and depositing new material Petrified wood formed by both processes Takes place over long time Fossils that are not remains Footprints, tunnels, nests, dung

Using Fossils to Determine the Order of Geological Events: 

Using Fossils to Determine the Order of Geological Events Principle of faunal succession Life forms changed through time Rocks can be placed in chronological position based on fossils Index fossils Distinctive and widely distributed plant or animal fossils Lived only briefly with a common extinction time Allow age correlations of exposed rock in different locations Relative dating technique Used for sedimentary rock

Geologic Time Scale: 

Geologic Time Scale Phanerozoic eon From 540 million years ago to present Animals developed Cenozoic era – recent life Mesozoic – middle life Paleozoic – ancient life Proterozoic eon 2500 million to 540 million years ago First eukaryotic organisms, simple marine life Archean eon 3800 million to 2500 million years ago All organisms prokaryotic and marine Hadean eon Earlier, before life, before earth solidified Eons  Eras  Periods  Epochs

Phanerozoic Eras, Periods and Epochs: 

Phanerozoic Eras , Periods and Epochs Precambrian Chiefly deposits of algae, fungi and burrow holes of worms Paleozoic Time of ancient life Fossils of this era are very different from anything living today Abundant oceanic life Swamps appear on land First reptile, fish and winged insect fossils formed Mesozoic Middle life Some fossils similar to today’s; many are very different Dinosaurs appear in Triassic period Fossils of the first birds, mammals, flowering plants and deciduous trees Ended with great extinction, including the dinosaurs Cenozoic Time of recent life Fossils similar to life today The Age of Mammals

Important considerations: 

Important considerations Time periods are extremely long Life goes back at least 3.5 billion years The Earth has changed greatly over its history Warming, cooling; sea level changes; continental drift Many periods of mass extinction have passed Most took millions of years New forms of life evolved to replace those that went extinct Many descendents of early life-forms are present today Bacteria, algae, primitive plants, starfish, jellyfish, clams The kinds of organisms present have changed the nature of the Earth Photosynthesis and oxygen; plants reduce erosion; man’s influence is ever increasing Mass Extinction Today

The Australopiths: 

The Australopiths Africa: 4 million to 1 million years ago Climate becoming drier Few fossils Short, stocky Males 1.5 m (5 ft): Females 1.1 m (3.5 ft) Walked upright Allowed for rapid movement Ability to see long distance Reduced amount of heat gained from sun Freed arms Herbivores Small brain

The Genus Homo: 

The Genus Homo Homo habilis 2.5 million years ago Larger brain, smaller teeth than austrolopiths Used stone tools Carnivorous Homo ergaster; Homo erectus 1.8 million years ago Larger size (up to 6 ft) Larger brain Manufactured and used stone tools Originated in Africa, migrated to Asia Homo heidelbergensis 800,000 years ago Fossils found in Africa, Europe and Asia Homo neanderthalensis Europe, Asia Not in Africa Homo sapiens Only remaining hominid species

Origin of Homo Sapiens: 

Origin of Homo Sapiens Out-of-Africa hypotheses H. sapiens originated in Africa migrated to Asia and Europe and displaced other species Multiregional hypothesis H. erectus evolved into H. sapiens H. heidelbegensis intermediate Neandertals Muscular, larger brain capacity than homo sapiens, Evidence of culture (collective group memory) Cave paintings, carvings, tools, burial Disappeared ~25,000 yrs ago Theories: Climate change, displaced or absorbed by H. sapiens population

Taxonomy: The science of naming and grouping organisms: 

Taxonomy: The science of naming and grouping organisms Modern system begun by Carolus Linnaeus Bi-nominal system of nomenclature Two name system Genus Group of closely related species Specific epithet Identifies species within genus Placed organisms into groups Two kingdoms Plantae, Animalia Further divided into smaller units

Modern System: 

Modern System 3 Domains Eubacteria Archaea Eucarya Composed of eukaryotic cells Four kingdoms Plantae Animalia Fungi Protista Prokaryotic organisms Number of kingdoms unknown

Phylogeny: 

Phylogeny Science of evolutionary relationships among organisms Seeks to reconstruct evolutionary history Based on: Fossil links Comparative anatomy of fossils or living organisms Developmental biology and life cycle information Molecular/biochemical similarities

Domains Eubacteria and Archaea: 

Domains Eubacteria and Archaea Prokaryotic Previously one taxonomic unit Still commonly referred to as bacteria Domains very different Eubacteria (true bacteria) Evolutionarily older than Archaea Archaea Thought to have branched off ~1.3 million - 2.6 million years ago

Eubacteria: 

Eubacteria Small prokaryotic single-celled organisms Cell walls contain peptidoglycans Polymers of sugars and unusual amino acids Heterotrophs Require organic molecules as source of food Some are parasites Pneumonia, TB, syphilis, gonorrhea, strep throat, staphylococcus Several autotrophs Cynobacteria – blue-green bacteria Thiobacillus ferrooxidans – derives energy from oxidation of iron and sulfur

Archaea: 

Archaea Many chemical similarities to Eucarya Extremophiles Extreme environments Three groups Methanogens Heterotrophic, anerobic, methane-producing Halobacteria Very salty environments Some use light to generate ATP Thermophilic High temperature, high sulfur environments Some are heterotrophs, some are chemoautotrophs Hydro-thermal vents, hot springs

Eucarya: 

Eucarya Kingdoms Protista Most single-celled Diverse form, metabolism, reproductive methods Fungi Most stationary, multi-cellular Non photosynthetic Cell wall composed of chitin Plants Stationary, terrestrial Cell wall composed of cellulose Photosynthetic: contain chlorophyll Animalia Heterotrophic, multicellar Sexual reproduction

Viruses: 

Viruses Obligate intracellular parasites Lack all functional organelles Not considered a member of a kingdom Consist of nucleic acid core surrounded by coat of protein Some have DNA Some have RNA Infectious Can function only when inside a living cell Host specific Need cell that has proper receptor sites

Other Acellular Infectious Particles: 

Other Acellular Infectious Particles Viroid Small single strand of RNA Infects plants Prions Infectious protein that cause brain disease Spongiform encephalopathies Symptoms: abnormal behavior, death Mad cow disease, scrapie