1. Life on Earth: What do Fossils Reveal? Chapter 6 1
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. 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. 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. 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. 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. 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. Freezing Desiccation (extreme drying) Preservation in amber
Preservation in tar Preservation in peat bogs Preservation of
Unaltered Soft Parts 8
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. 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. 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. 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. 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. Domain Eukarya Kingdom Animalia Phylum Chordata Class
Mammalia Order Primates Family Hominidae Genus Homo Species sapiens
Classification of the human 14
15. Domains 15 1. Domain Eukarya 2. Domain Bacteria 3. Domain
Archaea There are six Kingdoms distributed into three Domains
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. 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. Organisms with prokaryotic cells (cells without a nucleus)
Kindgom Eubacteria (bacteria and cyanobacteria or blue-green algae)
Domain Bacteria 18
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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Evolution may involve change from three different sources:
Mutations Gene recombination as a result of sexual reproduction
Natural selection Causes of Evolution 38
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. 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. 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. 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. 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. 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. 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.
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. 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. 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. 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. 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. 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. 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. 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. Similarity of embryos of all vertebrates suggests a common
ancestry. Evidence for Evolution from Biology 55 FIGURE 6-28
Embryos of different vertebrates.
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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Marine Ecosystem 69 FIGURE 6-35 Classification of marine
environments.
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. 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. 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. 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. 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. 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. 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. 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. 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. 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. Overview of the History of Life 80
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. 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. 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. 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
86. Modern scleractinian corals Bivalves Sea urchins Ammonoids
Mesozoic Era 86 Vertebrates Dinosaurs Primitive mammals Birds
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. 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. Evolutionary History of Plants 89 FIGURE 6-53 Geologic
ranges, relative abundances, and evolutionary relationships of
vascular land plants.
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. 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. Whats on the TEST?!? 92
93. Do your homework, it will prepare you the most for your
test! Do not just memorize the letters of the answer! 93
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. Difference between Laurasia and Laurentia 95 Laurasia the
northern part of pangea when it broke up (Laurentia + Asia)
Laurentia The North American Craton
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