1. 1. Life on Earth: What do Fossils Reveal? Chapter 6 1
2. 2. Fossils are the remains or traces of ancient life which have been preserved by natural causes in the Earth's crust. Fossils include both the remains of organisms (such as bones or shells), and the traces of organisms (such as tracks, trails, and burrowscalled trace fossils). Fossils 2 Xiphanctinus (Portheus) Molossus, once swam in the sea that covered much of present-day Kansas.
3. 3. Organisms do not all have an equal chance of being preserved. The organism must live in a suitable environment. Marine and transitional environments are more favorable for fossil preservation. Higher rate of sediment deposition. To become preserved as a fossil, an organism should: Have preservable parts. Bones, shells, teeth, wood are more readily preserved than soft parts. Be buried by sediment to protect the organism from scavengers and decay. Escape physical, chemical, and biological destruction after burial (bioturbation, dissolution, metamorphism, or erosion). Fossil Preservation 3
4. 4. 1. Chemical Alteration of Hard Parts 2. Imprints of Hard Parts in Sediment 3. Preservation of Unaltered Soft Parts 4. Trace fossils or Ichnofossils 5. Preservation of Unaltered Hard Parts Hard Partsmineralized material such as shells Soft Partssoft tissue Types of Fossil Preservation 4
5. 5. The shells of invertebrates and single-celled organisms, vertebrate bones and teeth: a. Calcite (echinoderms and forams) b. Aragonite (clams, snails, modern corals) c. Phosphate (bones, teeth, conodonts, fish scales) d. Silica (diatoms, radiolarians, some sponges) e. Organic matter (insects, pollen, spores, wood, fur) Preservation of Unaltered Hard Parts 5
6. 6. a. Permineralizationfilling of tiny pores b. Replacementmolecule-by-molecule substitution of one mineral for another (silica or pyrite replacing calcite) c. Recrystallizationaragonite alters to calcite (hard to distinguish) d. Carbonizationsoft tissues preserved as a thin carbon film (ferns in shale) Chemical Alteration of Hard Parts 6
7. 7. Impressions External molds Internal molds Cast Imprints of Hard Parts in Sediment 7 In some cases the original remains of the organism completely dissolve or are otherwise destroyed. The remaining organism-shaped hole in the rock is called an external mold. If this hole is later filled with other minerals, it is a cast.
8. 8. Freezing Desiccation (extreme drying) Preservation in amber Preservation in tar Preservation in peat bogs Preservation of Unaltered Soft Parts 8
9. 9. Tracks Trails Burrowsin soft sediment Boringsin hard material Root marks Nests Eggs Coprolites Bite marks Trace fossils or Ichnofossils 9 Markings in the sediment made by the activities of organisms Art by Harold Levin
10. 10. Trace fossils provide information about ancient water depths, paleocurrents, availability of food, and sediment deposition rates. Tracks can provide information on foot structure, number of legs, leg length, speed, herding behavior, and interactions. Trace fossils or Ichnofossils 10
11. 11. Organisms are grouped based on their similarities into taxonomic groups or taxa. Domain Kingdom Phylum (plural = phyla) Class Order Family Genus (plural = genera) Species (singular and plural) Taxonomy 11 Broad grouping Narrow grouping
12. 12. A system of binomial nomenclature (i.e., two names) is used to name organisms. The first of the two names is the genus and the second name is the species. Genus and species names are underlined or italicized. Genus is capitalized, but species is not. Biological classification 12 Kainops invius Orthoceras regulare
13. 13. A group of organisms that have structural, functional, and developmental similarities, and that are able to interbreed and produce fertile offspring. The species is the fundamental unit of biological classification. Paleontology relies on physical traits of fossils and the range in the appearance to identify species. The Species 13
14. 14. Domain Eukarya Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapiens Classification of the human 14
15. 15. Domains 15 1. Domain Eukarya 2. Domain Bacteria 3. Domain Archaea There are six Kingdoms distributed into three Domains
16. 16. All organisms are composed of cells. Eukaryotic cells have a nucleus (or nuclei) and organelles. Organisms with this type of cell are called eukaryotes (Domain Eukarya). Prokaryotic cells have no nucleus or organelles. Organisms with this type of cell are called prokaryotes (Domain Archaea and Domain Bacteria). Cells 16
17. 17. Organisms with eukaryotic cells (cells with a nucleus) Kingdom Animalia (animals) Kingdom Plantae (plants) Kingdom Fungi (mushrooms, fungus) Kingdom Protista (single-celled organisms, protists) Domain Eukarya 17
18. 18. Organisms with prokaryotic cells (cells without a nucleus) Kindgom Eubacteria (bacteria and cyanobacteria or blue-green algae) Domain Bacteria 18
19. 19. Organisms with prokaryotic cells, but which are very unusual and quite different from bacteria. Archaea tend to live under extreme conditions of heat, salinity, acidity. Kingdom Archaebacteria Domain Archaea 19
20. 20. Organic evolution refers to changes in populations In biology, evolution is the "great unifying theory" for understanding the history of life. Evolution = change 20 Plants and animals living today are different from their ancestors because of evolution. They differ in appearance, genetic characteristics, body chemistry, and in the way they function. These differences appear to be a response to changes in the environment and competition for food.
21. 21. Jean Baptiste Lamarck (17441829) observed lines of descent from older fossils to more recent ones, and to living forms. He correctly concluded that all species are descended from other species. Lamarck's Hypothesis of Evolution 21
22. 22. Lamarck assumed that new structures in an organism appear because of the needs or " inner want " of the organism. Structures acquired in this way were thought to be somehow inherited by later generations - inheritance of acquired traits. The idea was challenged because there was no way to test for the presence of an "inner want." Lamarck's Hypothesis of Evolution 22
23. 23. Lamarck also suggested that unused body parts would not be inherited by succeeding generations. The hypothesis was tested and rejected after an experiment in which the tails were cut from mice for twenty generations. The offspring still had tails. Similarly, circumcision has been practiced for more than 4000 years with no change among newborn males. Lamarck's Hypothesis of Evolution 23
24. 24. Charles Darwin and Alfred Wallace were the first scientists to assemble a large body of convincing observational evidence in support of evolution. They proposed a mechanism for evolution which Darwin called natural selection. Darwin's Natural Selection 24
25. 25. Natural selection is based on the following observations: 1. More offspring are produced than can survive to maturity. 2. Variations exist among the offspring. 3. Offspring must compete with one another for food, habitat, and mates. 4. Offspring with the most favorable characteristics are more likely to survive to reproduce. 5. Beneficial traits are passed on to the next generation. Darwin's Natural Selection 25
26. 26. Darwin's theory was unable to explain WHY offspring exhibited variability. This was to come many years later, when scientists determined that genetics is the cause of these variations. This principle can be stated as: " the survival of the fittest." Darwin's Natural Selection 26
27. 27. Gregor Mendel (18221884) demonstrated the mechanism by which traits are passed to offspring through his experiments with garden peas. His findings were published in an obscure journal and not recognized by the scientific community until 1900. Inheritance, Genes, and DNA 27 Mendel discovered that heredity in plants is determined by what we now call genes. Genes are recombined during fertilization. Genes are linked together to form chromosomes.
28. 28. Within the nucleus of each of our cells are chromosomes. Chromosomes consist of long DNA molecules (deoxyribonucleic acid). Genes are the parts of the DNA molecule that transmit hereditary traits. Chromosomes and DNA 28
29. 29. The DNA molecule consists of two parallel strands, which resemble a twisted ladder. The twisted strands are phosphate and sugar compounds, linked with nitrogenous bases (adenine, thimine, guanine, and cytosine). Chromosomes and DNA 29
30. 30. The structure of the DNA molecule was discovered by Watson and Crick in 1953. DNA carries chemically coded information from generation to generation, providing instructions for growth, development, and functioning. DNA 30
31. 31. Reproduction in organisms may be: Sexual Asexual Alternation of sexual and asexual generations All reproductive methods involve cell division. Reproduction and Cell Division 31
32. 32. New combinations of chromosomes result through sexual reproduction. One of each pair of chromosomes is inherited from each parent. This sexual genetic recombination leads to variability within the species. Genetic Recombination 32
33. 33. Binary fissionsingle-celled organisms that divide to form two organisms Buddinga bud forms on the parent that may: Separate to grow into an isolated individual, or Remain attached to the parent (colonial organisms). Budding occurs in some unicellular and some multicellular organisms. Spores shed by the parent (as in a seedless plant like moss or ferns) that germinate and produce male and female sex cells (leading to alternation of sexual and asexual generations). Asexual reproduction 33
34. 34. In a human cell there are 23 pairs of chromosomes. One of these pairs determines the sex of the individual. Diploid cellscells with paired chromosomes. Haploid cellssex cells (or gametes) with only one half of a pair of chromosomes. Example: egg cells or sperm cells Diploid and Haploid Cells 34
35. 35. MitosisDivision of body cells of sexual organisms. Produces new diploid cells with identical chromosomes to the parent cells. MeiosisDivision of cells to form gametes or sex cells (haploid cells), with half of chromosomal set of the parent cell; occurs in a two-step process, producing four haploid gametes. Cell division 35
36. 36. Fertilized egg forms when two gametes (egg and sperm) combine. Fertilized egg has paired chromosomes (diploid cell). Variation occurs because of the sexual recombination of genes. Genes are recombined in each successive generation. Recombination of Genes 36
37. 37. Mutations are chemical changes to the DNA molecule. Mutations can be caused by: Chemicals (including certain drugs), Radiation (including cosmic radiation, ultraviolet light, and gamma rays). Mutations may also occur spontaneously without a specific causative agent. Mutations 37 Mutations may occur in any cell, but mutations in sex cells will be passed on to succeeding generations. Mutations produce much of the variability on which natural selection operates.
38. 38. Evolution may involve change from three different sources: Mutations Gene recombination as a result of sexual reproduction Natural selection Causes of Evolution 38
39. 39. Evolution is a process of biologic change that occurs in populations. PopulationA group of interbreeding organisms that occupy a given area at a given time. Gene poolThe sum of all of the genetic components of the individuals in a population. Evolution in Populations 39
40. 40. Barriers keep their gene pools separate (distance, geographic barriers, reproductive barriers, etc.) There is no exchange of genes between different populations because they are reproductively isolated. Evolution in Populations 40
41. 41. Isthmus of Panama, is a barrier between oceans and populations of marine organisms. Islands with isolated populations of land animals. Galapagos Island finches Galapagos Island tortoises Hawaiian Island honeycreepers (birds) Grand Canyon separates different species of animals living on opposite sides of the canyon. Geographic barriers 41
42. 42. Ecological isolationPopulations inhabiting the same geographic area, but living in different habitats Temporal isolationPopulations that reproduce at different times (such as plants that flower in different seasons) Mechanical isolationIncompatible reproductive organs due to differences in size, shape, or structure Gametic isolationFertilization is prevented by incompatible gametes Reproductive barriers 42
43. 43. Speciation = The process through which new species arise. When a population is split by a barrier each population becomes isolated. Over many generations, the genetic differences may accumulate to the point that the different populations are no longer able to interbreed. At this point, the different populations would be considered separate species. Speciation 43 Once a new species is established, segments of the population around the fringes of the population may undergo additional speciation. With successive speciations, diverse organisms arise with diverse living strategies.
44. 44. Defined as the branching of a population to produce descendants adapted to particular environments and living strategies. Adaptive Radiation 44 Bill shapes are adaptations to different means of gathering food. FIGURE 6-17 The honeycreepers of Hawaii are a fine example of adaptive radiation.
45. 45. The question is not whether evolution occurs, but rather, exactly how it occurs. What is the mechanism of evolution? Modeling how evolution occurs 45 Phyletic gradualismgradual progressive change by means of many small steps (old idea). Punctuated equilibriumsudden changes interrupting long periods of little change (stasis). Most change occurs over a short period of time.
46. 46. Phyletic gradualism vs. Punctuated equilibrium Modeling how evolution occurs 46 FIGURE 6-21 Evolutionary models: (A) punctuated equilibrium, (B) phyletic gradualism.
47. 47. Punctuated equilibrium model suggests that evolution occurs in isolated areas around the periphery of the population (peripheral isolates). Speciation may occur rapidly in these isolated areas. When the new species expands or migrates from the isolated area into new areas, it looks like a sudden appearance in the fossil record. Speciation 47
48. 48. Phylogeny = the sequence of organisms placed in evolutionary order. Diagrams called phylogenetic trees are used to display ancestor- descendant relationships. Branches on the tree are called clades. PhylogenyThe Tree of Life 48 FIGURE 6-22 The phylogenetic tree of horses.
49. 49. Diagrams drawn to show ancestor-descendant relationships based on characteristics shared by organisms. They show how organisms are related but do not include information about time or geologic ranges. Cladograms 49
50. 50. Fossils provide direct evidence for changes in life in rocks of different ages. Homologous structuresCertain organs or structures are present in a variety of species, but they are modified to function differently. Modern organisms contain vestigial organs that appear to have little or no use. These structures had a useful function in ancestral species. Animals that are very different, had similar- looking embryos. Lines of evidence for evolution cited by Darwin 50
51. 51. 1. GeneticsDNA molecule 2. Biochemistrysimilar in closely-related organisms, but very different in more distantly related organisms. 3. Molecular biologysequences of amino acids in proteins Other Lines of evidence for evolution 51
52. 52. 1. Horses 2. Cephalopods and other molluscs 3. Foraminifera and other microfossils Evidence for Evolution from Paleontology 52 Many examples of gradual or sequential evolution in the fossil record, including: FIGURE 6-25 Evolutionary change in Permian ammonoid cephalopods.
53. 53. Homologous structuresbody parts with similar origin, history and structure, but different functions. Evidence for Evolution from Biology 53 FIGURE 6-26 Bones of the right forelimb from several vertebrates reveal similarity of structure.
54. 54. Vestigial organs suggest a common ancestry. Vestigial organs serve no apparent purpose, but resemble functioning organs in other animals. Evidence for Evolution from Biology 54 FIGURE 6-27 The pelvis and femur (upper leg bone) of a whale are vestigial organs.
55. 55. Similarity of embryos of all vertebrates suggests a common ancestry. Evidence for Evolution from Biology 55 FIGURE 6-28 Embryos of different vertebrates.
56. 56. Biochemistry Chemicals are more similar in related organisms: Proteins Antigen reactions of blood Digestive enzymes Hormone secretions Evidence for Evolution from Biology 56
57. 57. DNA sequencing If organisms appear to be similar on the basis of form, embryonic development, or fossil record, we can predict that they would have a greater percentage of DNA sequences in common, compared with less similar organisms. This is proven to be correct in hundreds (if not thousands) of analyses. Evidence for Evolution from Biology 57
58. 58. Fossils and Stratigraphy 58 The Geologic Time Scale is based on the appearance and disappearance of fossil species in the stratigraphic record. Fossils can be used to recognize the approximate age of a unit and its place in the stratigraphic column. Fossils can also be used to correlate strata from place to place.
59. 59. Geologic range = The interval between the first and last occurrence of a fossil species in the geologic record. The geologic range is determined by recording the occurrence of the fossils in numerous stratigraphic sequences from hundreds of locations. Geologic range 59
60. 60. Using Fossils to Correlate Rock Units 60 Geologic range for fossil X, Y, and z FIGURE 6-29 Use of geologic ranges of fossils to identify time-rock units.
61. 61. Cosmopolitan species have a widespread distribution. Endemic species are restricted to a specific area or environment. Cosmopolitan species are most useful in correlation Use of Cosmopolitan and Endemic Species in Correlation 61
62. 62. Appearances and disappearances of fossils may indicate: Evolution Extinction Changing environmental conditions that cause organisms to migrate into or out of an area Reworked fossils Pitfalls of Correlating with Fossils 62
63. 63. Index fossils (or guide fossils) are useful in identifying time-rock units and in correlation. Characteristics of an index fossil: 1. Abundant 2. Widely distributed (cosmopolitan) 3. Short geologic time range (rapid evolution) Index Fossils 63
64. 64. Biozone = A body of rock deposited during the time when a particular fossil organism existed. A biozone is identified only on the basis of the fossils it contains. Biozones are the basic unit for biostratigraphic classification and correlation. Biostratigraphic Zones 64
65. 65. 1. Ecology = Interrelationship between organisms and their environment. 2. Paleoecology = Ancient ecology; interaction of ancient organisms with their environment. Depends on comparisons of ancient and living organisms (modern analogs). 3. Ecosystem = Organisms and their environment the entire system of physical, chemical, and biological factors influencing organisms. Fossils and Past Environments 65
66. 66. 4. Habitat = Environment in which an organism lives. 5. Niche = Way in which the organism lives; its role or lifestyle. 6. Community = Association of several species of organisms in a particular habitat (living part of ecosystem). 7. Paleocommunity = An ancient community. Fossils and Past Environments 66
67. 67. The ocean may be divided into two realms: Pelagic realm = The water mass lying above the ocean floor. Benthic realm = The bottom of the sea Marine Ecosystem 67 Neritic zone = The water overlying the continental shelves. Oceanic zone = The water seaward of the continental shelves.
68. 68. Benthic realm Supratidal zone = Above high tide line Littoral zone (or intertidal zone) = Between high and low tide lines Sublittoral zone (or subtidal zone) = Low tide line to edge of continental shelf (~200 m deep) Bathyal zone2004000 m deep Abyssal zone40006000 m deep Hadal zone >6000 m deep; deep sea trenches. Marine Ecosystem 68
69. 69. Marine Ecosystem 69 FIGURE 6-35 Classification of marine environments.
70. 70. PlanktonSmall plants and animals that float, drift, or swim weakly. PhytoplanktonPlants and plant-like plankton, such as diatoms and coccolithophores ZooplanktonAnimals and animal-like plankton, such as foraminifera and radiolaria Modes of Life of Marine Animals 70
71. 71. NektonSwimming animals that live within the water column Benthic organisms or benthosBottom dwellers, which may be either: Infaunal: Living beneath the sediment surface; they burrow and churn and mix the sediment, a process called bioturbation Epifaunal: Living on top of the sediment surface Modes of Life of Marine Animals 71
72. 72. Terrigenous sedimentfrom weathered rocks Biogenous sedimentof biological origin Calcareous oozes: foraminifera, pteropods, and coccolithophores Siliceous oozes: radiolarians and diatoms Phosphatic material: fish bones, teeth and scales Hydrogenous sediment: precipitated from sea water manganese nodules Marine Sediments 72
73. 73. A depth in the oceans (about 4000-5000 m), which affects where calcareous oozes can accumulate. Above the CCD (shallower than 4000-5000 m), the water is warmer, and CaCO3 is precipitated. Calcareous sediments (chalk or limestone) are deposited. Carbonate Compensation Depth 73 FIGURE 6-44 Carbonate compensation depth (CCD).
74. 74. Below the CCD (below about 40005000 m), water is colder, and CaCO3 dissolves. Clay or siliceous sediments are deposited. Carbonate Compensation Depth 74 FIGURE 6-44 Carbonate compensation depth (CCD).
75. 75. Environmental limitations control the distribution of modern plants and animals. Note locations of fossil species of the same age on a map Interpret paleoenvironment for each region using rock types, sedimentary structures, and fossils. Plot the environments to produce a paleogeographic map for that time interval. Use of Fossils in Reconstructing Ancient Geography 75
76. 76. Migration and dispersal patterns of land animals can indicate the existence of: Land Bridges, Isolation and Migration 76 Former land bridge (Bering Strait) Mountain barriers Former ocean barriers between continents FIGURE 6-46 Intercontinental migrations of camel family members.
77. 77. High latitudes have low species diversity Low latitudes have high species diversity. Species Diversity and Geography 77 Species diversity is related to geographic location, particularly latitude. As a general rule, species diversity increases toward the equator. FIGURE 6-47 Species diversity ranges from low at polar latitudes to high at equatorial latitudes.
78. 78. Fossils can be used to interpret paleoclimates (ancient climates): 1. Fossil spore and pollen grains can tell about the types of plants that lived, which is an indication of the paleoclimate. 2. Plant fossils showing aerial roots, lack of yearly rings, and large wood cell structure indicate tropical climates 3. Presence of corals indicates tropical climates Use of Fossils in the Interpretation of Ancient Climatic Conditions 78
79. 79. 4. Marine molluscs with spines and thick shells inhabit warm seas 5. Planktonic foraminifera vary in size and coiling direction with temperature 6. Shells in warmer waters have higher Mg contents 7. Oxygen isotope ratios in shells. Use of Fossils in the Interpretation of Ancient Climatic Conditions 79
80. 80. Overview of the History of Life 80
81. 81. Remains of prokaryotic cells (blue-green algae or cyanobacteria) more than 3.5 billion years old. Found in algal mats and stromatolites. Oldest evidence of life 81 By producing oxygen as a gas as a by-product of photosynthesis, cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one. Thanks cyanobacteria for our O2!
82. 82. Metazoans = multicellular organisms Trace fossils of metazoans about 1 billion years ago First body fossils of soft-bodied metazoans (worms, jellyfish, and arthropods) about 0.7 billion years ago Invertebrates with hard parts appeared during Late Proterozoic or Early Paleozoic. Earliest Metazoan Organisms 82
83. 83. Geologic ranges and relative abundances of fossil organisms 83FIGURE 6-54 Geologic ranges and relative abundances of frequently fossilized categories of invertebrate animals. Major Classes GeologicTime
84. 84. Most animals were deposit and suspension feeders Trilobites Brachiopods without hinged shells (inarticulates) Small cap-shaped molluscs Soft-bodied worms Chitin-shelled arthropods Reef-building archaeocyathids Early PaleozoicCambrian Period 84
85. 85. Trilobites Articulate (hinged) brachiopods Nautiloids Crinoids Rugose (horn) corals Tabulate corals Later during Paleozoic 85 Branching twig-like bryozoans (moss animals) Vertebrates Fishes Amphibians Reptiles
86. 86. Modern scleractinian corals Bivalves Sea urchins Ammonoids Mesozoic Era 86 Vertebrates Dinosaurs Primitive mammals Birds
87. 87. Molluscs of many types (but no ammonoids) Planktonic foraminifera Sea urchins Encrusting bryozoans Barnacles Vertebrates Age of mammals Appearance of humans Many other vertebrate groups Cenozoic Era 87
88. 88. Mass extinctions occurred at the ends of the following periods: Ordovician Devonianroughly 70% of marine invertebrates extinct Permianthe greatest extinction. More than 90% of marine species disappeared or nearly went extinct *Gave rise to DINOSAURS Triassic Cretaceousaffected dinosaurs, other land animals, and marine organisms; about 25% of all known animal families extinct Extinctions 88
89. 89. Evolutionary History of Plants 89 FIGURE 6-53 Geologic ranges, relative abundances, and evolutionary relationships of vascular land plants.
90. 90. 1. Earliest photosynthetic organisms were single-celled organisms during Precambrian. 2. Green algae or chlorophytes may be the ancestors of vascular land plants. 3. Plants invaded the land during Ordovician, reproducing with spores. 4. First plants with seeds appeared during Devonian. Gymnosperms (such as conifers). Had pollen. 5. Carboniferous coal swamps dominated by seedless, spore- bearing scale trees. 6. Flowering plants appeared during Cretaceous. Angiosperms. Dominant plants today. Evolutionary History of Plants 90
91. 91. 4. First plants with seeds appeared during Devonian. Gymnosperms (such as conifers). Had pollen. 5. Carboniferous coal swamps dominated by seedless, spore- bearing scale trees. 6. Flowering plants appeared during Cretaceous. Angiosperms. Dominant plants today. Evolutionary History of Plants 91
92. 92. Whats on the TEST?!? 92
93. 93. Do your homework, it will prepare you the most for your test! Do not just memorize the letters of the answer! 93
94. 94. Faults 94 HW - Hanging Wall (A) HW FW Foot Wall (B) HW HW FW FW FW Thrust fault is just a low-angle reverse fault Motion is relative or lateral fault
95. 95. Difference between Laurasia and Laurentia 95 Laurasia the northern part of pangea when it broke up (Laurentia + Asia) Laurentia The North American Craton
96. 96. Index fossils (or guide fossils) are useful in identifying time-rock units and in correlation. Characteristics of an index fossil: 1. Abundant 2. Widely distributed (cosmopolitan) 3. Short geologic time range (rapid evolution) Index Fossils 96
97. 97. 97 The End