Historical Geology Review for Exam II
Fossils and Paleontology
Introduction to Fossils and Speciation:
Define:
1. FOSSIL: The remains or indications of an organism that lived in
the geologic past (at least 10,000 years old).
2. SUBFOSSIL: The remains or indications of an organism that lived
in the more recent past: younger than 10,000 years old.
3. ARTIFACT: Something made or produced by the activities of man:
arrowheads, pottery, etc. These are not considered fossils.
4. PALEONTOLOGY: The study of ancient life through the
investigations of the fossils found and their relationships to the
environments of deposition.
5. BIOFACIES: The unique assemblage of fossils in a stratum that
tells the investigator the paleoenvironment, paleoecology, or other
paleo-biological aspects of the time in which the stratum was
deposited.
6. TAXONOMY: The science of classifying forms of life living or fossil.
7. TAPHONOMY: The study of the ways in which organisms die and
become fossilized. Fill in examples provided by your instructor for
the following modes of fossilization:
Modes of Fossilization:
1.) Whole Organism – The most rare forms of fossils. All parts are
preserved…even soft tissues. Examples include an elephant frozen in
ice, a mummified sloth sealed up in a cave, or any complete remains of
an organism.
2.) Hard Parts Preserved – These are common. This is where the hard
parts (bone, teeth, shells) are the only part preserved. These withstand
many sedimentary environments better than soft tissues.
3.) Permineralization – After the remains are buried, the action of water
can dissolve the original organic material and replace it with another
mineral from ions dissolved in the groundwater. Petrification of wood is
a good example of permineralization.
4.) Carbonization – Under some environments of fossilization, the
carbohydrates, proteins, etc., breakdown leaving only a carbon film of
the organic remains. Plant leaves and fish are common examples.
5.) Entombment – If the organic remains are sealed up and decay is
slowed greatly the fossil is said to have been entombed. Insects or
other organisms trapped in amber (fossil tree sap) or tar
6.) Trace Fossils – These are indications of past life but not really
organic remains. These include footprints or tracks left in mud that
subsequently turned into sedimentary rock. Other trace fossils include
worm burrows, impressions of scales or skin, molds and casts (see
below), and coprolites (fossil dung). Trace fossils are indications of the
organism having been there, but no body parts are found.
7.) Molds and Casts – (A Type of Trace Fossil) – If a clam dies and is
buried in sediment that later turns to stone, groundwater may percolate
through the fossil, dissolving the original shell away, leaving only a 3diminsional impression of the shell. This impression is the mold. Later,
if foreign sediment fills in the mold, the rock may become eroded in a
way that the cast falls away from the mold. Neither cast or mold is the
original shell (or bone as the case may be) but a type of natural replica.
Sometimes (especially in clams and snails), after death, the organic
tissues decay away and sediment fills in the internal portion of the shell.
Later the outer original shell may become dissolved away leaving behind
an internal cast of the shell called a steinkern.
8.) Pseudo-fossils - This category describes inorganic rocks and
minerals that happen to erode or form to resemble the organic remains
of some plant or animal. A common pseudo-fossil is seen in dendrites,
which are crystals of dissolved substances such as manganese oxides
that grow between bedding planes of some strata. When the bedding
plane is broken, the “dendrites” resemble plant fossils…but , of course,
they are not.
Environments Conducive to Fossilization
In order for organic remains to become fossilized, the best prerequisites
are:
1. if the remains hard parts: bones, teeth, shells
2. quickly buried to prevent being scavenged or destroyed
3. the lithification of the sediments containing the remains
This does not mean that soft-bodied organisms cannot become fossils
(they do), but that they need to be placed in low energy, reducing
environments…lagoons, deltas, swamps.
Ecological Environments
1. Terrestrial - organisms living on dry land
2. Supratidal – area of a beach that only is covered by water
during a storm surge…the dune area of a beach.
3. Intertidal – the beach area between high and low tide…a harsh
environment in which to live: part of the day underwater, part in
the sun and desiccating conditions
4. Littoral – always underwater from low tide mark outward
5. Planktonic Life Habit – organisms that have no means to swim
against wind or currents…floaters
6. Nektonic Life Habit – organisms that can swim against wind or
currents
7. Benthic (Sessile & Vagrant) Life Habit – organisms that live on
the bottom either attached (sessile) or moving along the bottom
(vagrant)
8. Infaunal & Infloral Life Habit – organisms that live/burrow into
the mud of the sea floor
9. Epifaunal & Epifloral Life Habit – organisms that live on top of
the mud on the sea floor
10. Demersal Life Habit – organisms that live primarily on the
bottom, but can become nektonic if needed…octopus
11. Pelagic Waters – waters of the sea past the continental shelf
12. Neritic Waters – waters of the sea from the continental break
shoreward
13. Oceanic Waters – open waters of the deep sea…i.e. over the
MOR
Taxonomy and the Species Concept:
Taxonomy is the science of classifying and naming plants and animals.
The taxonomic system we use today is derived from an 18th century
Swedish botanist by the name of Carl Linné. He formed a filing system
of sorts that classified life forms into groups that share many common
attributes.
Common attributes are characteristics such as whether or nor the
organisms in question all possess a backbone, or do they not possess a
backbone, but maybe all possess stinging cells…or do they all possess
a hard endoskeleton…or do they possess a chitin exoskeleton…do they
have 6 legs? 8 legs?… no legs?…Do they have wings or not?…Is their
body segmented? etc….etc. So, whenever a new organism or fossil is
discovered, it is placed into a named category that contains other
organisms that share the same or similar characteristics.
The Binomial System of Nomenclature is the name of this filing
system. It starts with the most general, the Kingdom level (or Kingdom
taxon), and ends with the most specific level, the Species taxon. The
Genus and Species of any organism is the Scientific Name of that
organism. Kingdoms are divided into smaller, more specific groups
called Phyla (Phylum singular), Phyla are divided into the smaller more
specific Classes, Classes into Orders, etc.
Kingdom (Most General)
Phylum
Class
Order
Family
Genus
Species (Most Specific)
There are currently 6 recognized Kingdoms of life:
1.
2.
3.
4.
Kingdom Animalia for all animals
Kingdom Plantae for all “true” plants
Kingdom Fungi for all mushrooms, molds, etc.,
Kingdom Protista for all unicellular or simple multi-celled
organisms such as Amoeba sp., Paramecium sp., algae,
etc.
5. Kingdom Archeobacteria for the very primitive extreme
thermophilic, extreme halophilic, and the methogenic forms
of bacteria.
6. Kingdom Eubacteria for the more complex bacteria such
as the Gram-negative or Gram-positive bacteria.
In order for an organism to be placed into one of these Kingdoms, it
must possess common characteristics shared by the other organisms in
that Kingdom. The same rule applies whenever the organism in
question is later classified as to Phylum, Class, Order, etc. For humans,
the taxonomic classification is as follows:
Kingdom Animalia – Humans are active heterotrophs (getting their
food from sources outside their bodies), no cell wall, non-photosynthetic,
purposeful movement, etc.
Phylum – Chordata - Those organisms possessing a stiffened
cartilage rod (notochord) running the length of their bodies that supports
the body and nerve cord.
Subphylum – Vertebrata – Those chordates that possess bony
structures (vertebrae) that encase and protect the spinal cord
Class – Mammalia – Those vertebrates whose females
possess mammary glands to feed the young, bodies covered with hair,
the ability to create and maintain a constant body temperature, etc.
Order – Primates – Those mammals that possess
stereoscopic vision, an opposable thumb, flexible girdle assemblages
(shoulders and hips), etc.
Family – Hominidae – Those primates that possess
upright stance, non-opposable big toes, larger brain to body ratio, etc.
Genus – Homo – Latin for “Man”
Species – sapien – Latin for “Wise”
The Scientific Name for humans is then, Homo sapiens. If, for
instance, humans did not possess a notochord, they would not be
classified in the Phylum Chordata. If we possessed stinging cells such
as jellyfish, we might be classified in the Phylum Cnidaria, those
organisms that possess Cnidocytes (stinging cells). If any common
attribute or characteristic for a particular organism is missing or is vastly
different from other “similar” organisms, the common attributes that
“define” a certain taxonomic level (or “taxon”) may warrant placing the
organism into a different taxon.
Biologic "species" - is a group of sexually isolated organisms that are
all capable of reproducing with one another, but not (at least in Nature)
with members of a different biospecies.
Range or “Fatherland” of a Species - is the geographic area within
which the species can obtain all the necessary items for survival:
enough food and water, an appropriate reproductive mate, appropriate
nesting materials, hiding places, etc.
Niche – the ecological role an organism fulfils in an ecosystem: Vultures
have the niche of being a scavenger; Lions have the niche of being
carnivorous predators; Zebra are prey animals for carnivores, etc.
Habitat – where the organism lives: terrestrial woodlands, deep-water
marine, nektonic arctic marine waters, etc.
Environmental Pressures are any changes in the environment
(changes in temperature, climate, diseases, radiation levels, decreases
in vegetation, etc.) that causes “stress” upon a population. This causes
those individuals that have the genetically established ability to cope
with these changes to survive; those that do not have the genetic
makeup either die (become extinct) or move to a different, more livable
environment (become extirpated). The term extant refers to the
individuals that are still in existence in their ranges (i.e. humans are
extant, so are alligators, cardinals, red squirrels, oak trees, etc.).
The Geologic Range of any species of organism is the time from its
evolutionary separation from another group as a distinct species, until
the time of its extinction as a species.
Classification of Fossils
Paleontologists classify fossils mainly upon the fossil’s morphology or
structural features. Since this is so, the symmetry of an organism is an
important aspect of the organism’s morphology.
I. Symmetry refers to the number of imaginary planes that could “cut”
the organism into two equal mirror images. For instance, if you stood
halfway behind a full-length mirror that was slightly tilted inward toward
you, it would appear to an observer in front of you that they were seeing
a “complete you”. In reality, of course, the observer would only be
seeing half of you and a “mirror image” of that half. Humans have only
one plane to “cut” our bodies into two mirror images. The plane
obviously runs between the middle of the forehead downward to the
groin area. Therefore, we exhibit bilateral symmetry, one plane of
symmetry. This is also the symmetry type of “higher” forms of life.
 Radial symmetry describes organisms that are generally circular
and have a flattened, disk-like body. Since there are an infinite
number of diameters the can cut a circle, organisms exhibiting
radial symmetry have an infinite number of mirror planes and
spherical symmetries describe round organisms
 Bivalve symmetry describes those organisms, particularly clams,
whose symmetry plane passes between the valves of the
organism.
 Pentameral (5-ray) is generally reserved to describe the type of
symmetry associated with the members of the Phylum
Echinodermata (starfish, sand-dollars, sea urchins, etc.).
 Asymmetrical – In organisms such as some calms (oysters) and
some sponges, there are no planes of symmetry.
II. Other morphological features include:
 The presence (or absence) of spines on shells
 The direction shells coil (dextral – “right-handed” or sinestral – “lefthanded)
 Bones are identified by comparison with known skeletons
(comparative anatomy)
 Exoskeleton composition – CaCO3, chitin, etc.
 Numbers of appendages or absence of appendages
 The “geologic age” of the fossil is considered
 The “biofacies” of the fossil in the strata is also included in its
description
 Any other distinguishing characteristic is also recorded.
Biologic Evolution: How Life Changes in
Response to Changes in the Environment.
Evolutionary Terms:
Deoxyribonucleic Acid (DNA) – the molecule of life.
A double helix shaped
molecule made of nucleic acid components called nucleotides that consist of:
 A five carbon sugar – Deoxyribose
 A phosphate group – PO-4
 A nitrogenous base – Adenine, Guanine, Cytosine, and Thymine
Whenever DNA is in its relaxed state in the nucleus, it is referred to as Chromatin.
How the nitrogenous bases are arranged in the molecule designates the production or
synthesis of proteins and other compounds. The interpretations of these sequences of
chemical messages on the DNA molecule comprise the genetic “blueprints” of an
organism, and regulate the functions of the organisms cells, and ultimately the tissues,
organs, etc. It makes the organism unique to that species, although able to reproduce
within that population of organisms.
Chromosome – Chromatin (DNA) that has “pulled in” upon itself forming a “rodshaped” body.
Gene – a portion of a chromosome that is a discrete unit of heredity information the
codes for the synthesis of a particular protein, enzyme, etc.
Genetic Mutation - Any disturbance of the sequence of nitrogenous bases alters the
“blueprints” of the DNA. This results in changes in the expressions of the gene causing
different characteristics to be expressed in the adult form.
NOTE: 99% of all genetic mutations that occur in nature are deleterious to the
organism possessing them. The remaining 1% develop advantages to cope with the
environmental changes and subsequently pass on their genetic heritage to the next
generation.
Mitosis – a type of cell division in which the cell “clones” itself.
This is seen in
structural growth (from fertilization of an egg to development of the individual) and
repair (repairing damaged cells) in life forms.
Meiosis – This is a reduction division occurring in the Primary Sex Cells (testes and
ovaries), reducing the chromosome count from the somatic 2N count (a full set of
chromosomes) to the gametic 1N count (sperm & egg). This mechanism provides a
continuance of the correct chromosome count from generation to generation. (You
received half of your genetic makeup from one parent and half from the other) In
humans the normal chromosome count in cells is 46. The count of chromosomes in
sperm or eggs is 23 as a result of meiosis in the primary sex cells. The result (after
fertilization of an egg by a sperm) is a zygote containing 46 chromosomes…continuance
of chromosome count.
Trophic Level – a “feeding level” in an ecosystem’s food chain or food web:
Top Carnivore Level
Secondary Consumer Level
Primary Consumer Level
Producer Level
There is only a 10% energy transfer from a lower trophic level to the next highest. For
instance, at the producer level, there is 100% of energy available from the plants to the
primary consumer. After the 10 consumer eats and uses energy for its needs, and is eaten
by the 20 consumer, only 10% of the potential initial energy from the plants is passed to
the 20 consumer. The energy transferred to the Top Carnivore is only 10% of the energy
of the 20 consumer. In essence, the Top Carnivore receives only 1% of the potential
energy available at the producer level.
Where did the energy go?…Much of it is lost as endothermic body heat, used up in the
energy required for biochemical reactions, defecated away unusable, undigested
foodstuffs to be used as energy by other organisms such as bacteria and fungi that enrich
the soil for more plants to grow etc., etc. etc….
Ecological Producer – the term to describe the photosynthetic green plants of an
ecosystem whose role is to “produce” food for other organisms. They have the ability,
through the process of photosynthesis, to convert sunlight energy into chemical energy.
6CO2 + 12H2O  C6H12O6 + 6O2 + 6H2O
Carbon Dioxide
Water
Light/Pigment
Glucose
oxygen
Water
Primary Consumer – an organism that feeds directly on the producer.
“Herbivores” – plant-eating organisms.
They are
Secondary Consumer – an organism that feeds upon the primary consumer.
They
are “Carnivores” – meat-eating organisms.
Top Carnivore – an organism that is the final recipient of energy in an ecosystem.
Niche – “The ecological/biological role (its “Job”) the organism plays in an
ecosystem”. This can be the role of a Scavenger taking care of the dead remains of other
organisms; being the “Top Carnivore” or the top predator in an area; being the Producer
such as a green plant whose role in the ecosystem is to convert sunlight energy into
sugars for other organisms.
Habitat – “Where the organism lives”; The geographic area in which the organism is
found. This term is closely related to the biologic “Range” of an organism.
Biologic Range - The range of an organism is the geographic area in which the
organism can find everything it needs for survival:
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Appropriate food
Suitable reproductive mate
Appropriate nesting material (if needed)
Appropriate hiding places
Sufficient water
Correct climate for survival.
Etc.
Carrying Capacity of an Environment – This is the maximum amount of biomass
(life forms) that a certain geographic area can support in terms of food, water, etc. For
example, if a person had one acre of land upon which to raise cattle, and only put one
cow on the acre, the grass probably would grow fast enough to support the single cow
with unlimited food. With the addition of more and more cows, there would be a point
reached whenever the grass could not keep up with the demands of food by the cattle. At
this point, the “Carrying Capacity” of that acre had been surpassed. Every
environmental ecosystem has its own carrying capacity dependent upon the amount of
food that can be produced.
All of the arable farmlands of the earth have been calculated as to area and capacity of
food production. With a world population of 6 billion today, at current population
growth, the human population of the earth will be 11 billion by the year 2050 – 2100.
The demand for foods will so great that the carrying capacity of the entire earth’s
farmlands will be surpassed. Many researchers expect the onset of a worldwide famine.
Extinct – a species, for whatever reason, has lost the ability to transfer its genetic
make-up to a new generation. The sequence of DNA that defined that particular species
as “that species” is gone.
Extant
- the species is still in existence in its niches and habitats. Humans are extant,
red squirrels, coyotes, oak trees, etc.
Extirpated – A species has moved to another geographic local (range), or has been
driven out of its natural habitat/range for some reason, although it is not extinct. It still
survives in some area, but not in all its past ranges. For example: Black Bears used to be
found in most areas of Texas. Over the years, they were hunted out, or forced to move to
a more reclusive area. They are still extant, but not inhabiting the geographic ranges that
they once had.
I. Microevolution – Small, sometimes subtle changes within the characteristics
of a species reflecting environmental changes in a relatively small geographic area.
Example:
 In Pre-Industrial London, the streets were lined with imported eucalyptus trees for
ornamentation.
 These trees had a light colored, smooth bark much like a Crepe Myrtle tree.
 There existed a moth that during the day (while resting/hiding) would land on these
eucalyptus trees.
 In every population of organisms (A “Population” is a group of organisms of the
same species and capable of inter-breeding) there is genetic variation seen in its
offspring.
 Color variation is common with one end of the spectrum of color being
“Melanistic” (individuals possessing an abundance of pigment giving them a dark
color), the other end of the spectrum being “Albinistic” (individuals lacking
pigment giving them a light color), and some “Norm” in between representing the
color that works best for the present environment.
 Prior to the coal using Industrial Revolution, the barks of the eucalyptus trees were
clean and the color selected for was a light beige color as the “Norm” for the
population of moths. If a melanistic or an albinistic form were to hatch, it would
easily be picked off by predators such as birds since it had no camouflage at all.
Its genome (genetic makeup) would be taken out of the population.
 After the burning of lots of coal, the trees became sooty and the “environment” for
the moths changed. A moth hatched with darker pigmentation now would survive
and the lighter colored variations would perish.
 This is “Microevolution” in action. Small, subtle genetic changes in a population
of organisms reflect small changes in the environment.
 If the change in the environment is great enough that there is no genetic expression
in the “genome” of the population (the total genetic scheme of the population – all
possible genetic expressions) to cope with the environmental change, the species
will become extinct.
II. Macroevolution – This term is used to describe genetic/organismic changes
over a broader timeframe such as the changes in a biologic lineage taking place over a
long time geologically:
Air-breathing fish-like organisms to Amphibians to Reptiles
“Evolutionary Lineage” is the key term here. The lineage of the horse, of humans, etc.,
over time.
Evolutionary Theory
Jean Baptiste de Lamarck – developed the concept referred to as “Lamarkism”.
This idea comes from Lamark’s observations of life form diversity and his concluding
that life forms characteristics come about from other past life forms by “Use or Disuse”
of certain attributes, or of an “Inner Want” or “Desire” of the organism to change for the
better. Lamarck believed that snakes evolved from lizards that had this “Inner Desire” to
crawl, instead of walking.
His famous example is that of giraffes having long necks because of their constant
stretching to reach higher and higher leaves: hence their offspring would have longer
necks. If this were so, a blacksmith, developing large muscles due to his constant
exertion, would always have children that had large muscles because the father needed
them in his life. This is not so. Lamarkism was quickly discredited because there is no
evidence that the physical experiences of one generation can be directly and completely
transferred to the next generation.
Charles Darwin – From his life experiences gained in the natural sciences, and those
experiences he had while serving as the naturalist on the H.M.S. Beagle, he formulated
several observations of how life could change or evolve over time:
Darwin’s 4 Observations that Lead to the Formation of the Concept
of Natural Selection:
1. “The Size of a Population of organisms within a geographic area remains
relatively constant over time.” Darwin is saying that the number of individuals making
a species’ population remains constant over time due to a number of intrinsic and
extrinsic factors:
 Predator/Prey Ratios: In the springtime when there are abundant
grasses (primary foods), the consumers increase in number.
 At the same time, the numbers of predators rises in response to
increased food supplies.
 As the population of both predators and prey approach the carrying
capacity of the environment, competition for food increases and
population numbers of both predator and prey cycle downward to
await the springtime grasses to start the cycle over again.
2. “Even though the Population size is constant over time, the number of offspring
produced is HIGH”. Most forms of life produce more offspring than will ever survive
to adulthood because of the likelihood of death from predation, starvation, competition
with others for mates, nesting sites, etc.
3. Because so many offspring are produced, the individual genetic variability within
the population is high.
 The “gene pool” is diverse.
 No two individuals are genetically identical, so they possess varying
physiological and “somatic” strengths and weaknesses (“soma” =
“body”, and refers to bone, muscle, etc.).
4. With the population size relatively constant, the number of offspring produced
high, the genetic variability high, the Competition between organisms is also high.
This leads to Darwin’s idea of the “survival of the fittest”
 Competition success is determined by “chance” as to which genetic
make-up succeeds within a given environment.
 Intraspecific Competition – competition for food, reproductive mates,
territory, etc. between members of the same species.
 Interspecific Competition – competition for food or territory (but
NOT reproductive mate since these organisms are of different species)
between organisms in a geographic area…This is competition on the
Biologic Community level.
 Gametes, sperm and eggs, genetically reflect the genetic make-up of
the individual producing them.
 If the environment changes, those individuals with characteristics
allowing them to survive pass those genes to the next generation.
 Those individuals not possessing the necessary characteristics do not
survive and their specific genetic make-up is lost unless they are able
to find another geographic area (away from the competition) in which
they are capable of surviving.
The Species Concept
Morphospecies:
 An outdated concept whereby a species is determined strictly upon
measurements of physical attributes: beak length, antler size, foot
length, tooth size, braincase size, etc.
 Numerical limits were set on certain characteristics, and if an
individual’s measurements were too different, that individual was
considered to be of a different species.
 This was the way to determine “species” prior to modern technologies
such as electrophoresis and DNA studies.
 Problems with the morphospecies concept is that it is not clear how
genetic differences are expressed morphologically, and it is difficult to
determine how much morphological difference warrants a new
species.
Biospecies:
Fatherland:
 A group of organisms that may show somatic genetic diversity, but
are “Sexually Isolated” from other groups.
 Sexual Isolation refers to reproductive success: the only successful
reproduction is done within the group…If reproduction is tried with a
member not in this genetic group, most of the time it is a failed
attempt.
 The original geographic area on earth where a species developed: That
species is “indigenous” to that area.
Biologic Range:
 The geographic area on earth whereby within this area, the species is
able to find everything necessary for survival: food, water needs,
appropriate mate, nesting materials, enough territory, etc.
 Outside this range, the species cannot survive.
Cell Division
The number of chromosomes in the cells of an individual is a specific characteristic of
that particular species.
 For instance, in humans, in any body or “somatic” cell, the normal
chromosome count is 46 or 23 pair.
 For mosquitoes, a body cell contains 8 chromosomes…for goldfish it
is around 258 or so…
 It is very difficult to remember the somatic chromosome count for the
40 million or so species that are thought to be on earth today, so
geneticists have devised a shorthand of sorts. Somatic counts are said
to be ”Diploid” and the symbol “2N” is used to designate this state.
Mitosis: “Structural Growth and repair”…From fertilization through development
to adulthood, cells replicate themselves, and repair wounds as needed. These are 2N
Diploid somatic cells replicating (cloning) themselves to form 2N somatic cells. If you
cut your hand, “hand cells” grow back, not feet cells or liver cells.
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Meiosis: A “Reduction Division” occurring in the primary sex cells whereby the 2N
spermatocytes or oocytes undergo a two stage division resulting in the “mixing” of
genetic material and a reduction of the cells from a 2N diploid somatic state to the 1N
haploid gametic state: sperm or eggs.
 In order to perpetuate the chromosome count, Gametes (sperm and
eggs) contain ½ the chromosomes of the somatic count (You get ½ of
your genetic material from each parent).
 Gametes arise from special somatic cells called “Primary Sex Cells”:
Spermatocytes in the testes and Oocytes in the ovaries.
 If all goes well, the offspring will receive the genetic characteristics
that enabled their parents to survive the environment in which they
live. (Restate Darwin’s Observations)
Mutations:
 If mistakes take place either from defects within the cell’s division
mechanics, or contaminants (toxins, harmful radiation, etc.),
Mutations (aberrant gene expression) can occur.
 In the case of genetic mutations, 99% of all genetic mutations are
harmful, or in some cases, deadly to the recipient.
The Species Concept (continued)
How a “Species” Develops:
 If a fatherland contains a certain species, say of a bird like the
“Flicker”. This is a relative of the woodpecker and comes in at least
two varieties: the “Yellow-shafted” and the “Red-shafted” forms.
 These used to be considered two distinct species according to the
“Morphospecies” concept. (They have since been reclassified as
“varieties” rather than separate species after information from DNA
analysis was gathered.)
 Within the fatherland/range of this species there is everything needed
for survival toward the center, but towards the edges, it becomes
harder and harder for the individuals to survive. Remember that once
the individual gets outside its range, it cannot survive.
 This is similar to humans that live in the “rich” side of town compared
to the humans forced to live under a bridge or someplace like that. It
is harder to survive being “poor” economically or biologically. It is
more likely that the “poorer” individuals would suffer the extremes in
the environmental changes rather than the “rich” ones.
 This phenomena is described by paleontologist Stephen J. Gould
whereby these “outsiders” are called Peripheral Isolates: “those
members of a population living on the fringes of a range that are
subject to the most Environmental Pressures”.
“Natural Selection is driven by competition between species due to environmental
presseure.”
Environmental Pressures include changes in:
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Food availability
Finding an appropriate reproductive mate
Climate: temperature, humidity, precipitation, and etc.
Appropriate nesting materials
Harmful bacteria, viruses, and pathogenic organisms
Topographic changes due to tectonics
Availability of sunlight
Air circulation/Oxygen concentration changes
Salinity changes
Anything in the dynamic environment that would effect survival
The Species Concept (continued)
How a “Species” Develops:
 In every biologic population there is genetic diversity on the species
level: not every individual is exactly alike. (meiosis)
 Take tail feather length, for instance. Some flickers have shorter tail
feathers, some longer, and a spectrum of lengths in between.
 There would be an average or mean tail feather length that could be
plotted on a normal curve. Most of the population would be within
the “normal” range that, for example, I will call 4 inches.
 Some fewer number of individuals in this population would have tail
feathers of the extremes: 2 inches to 8 inches.
 Suppose that the 6-inch tail feather worked best in the current
environmental pressures of the fatherland. This is what is referred to
in evolution as a “Stock Group”.
 Suppose that the fatherland was split in two areas by the advancement
of some glacier, an inland sea encroachment, or the rising of some
mountain range: This “splits the fatherland into two environmentally
distinct areas called “Allopatric Zones”.
 The environment will be different in each zone and the population of
flickers will now be subjected to different environmental pressures.
 Suppose that the western Allopatric Zone was arid, dessert-like, with
short scrubby trees, and the eastern Allopatric Zone was a more
temperate, Old Growth forest with very tall trees forming a high
canopy.
 These two allopatric zones contain, at first, the same distribution of
flickers as far as the mean tail feather length of 4 inches, and the
individuals with the extremes of 2 inches to 8 inches.
 Birds use their tail feathers to guide them in flight, for control and
maneuverability.
 Longer tail feather length in those individuals in the scrub-brush
western zone would be chosen against because perhaps they were
easier prey for the foxes (predators) inhabiting the west. Over time,
the mean tail feather length of the western individuals would “shift” to
a mean of 2 inches as the “norm”.
 In the eastern zone, longer tail feathers will be needed for the long
glides between trees and the need for better and speedier food
gathering perhaps. The 8-inch tail feather length would become the
mean or “norm” for the eastern population.
 Are these now two separate Biospecies? Now, if the barrier that
separated these two “allopatric species” was removed (by erosion,
etc.), and the ranges of these two related but physiologically distinct
flickers expanded into each other’s range, this forma a third zone
called the “Zone of Sympatry”, the sympatric zone where if the two
varieties are tested of sorts.
 If the two groups are able to copulate and produce viable offspring
then they have passed the test of sympatry and NO SPECIATION
HAS OCCURRED.
 If, for whatever reason, they cannot produce viable offspring, then
they have failed the test of sympatry and can be considered sexually
isolated and referred to as separate, but related, Biospecies.
Types of Sexual Isolation
Mechanical Isolation:
 The size of the individuals no longer facilitate copulation
 The genitalia size no longer are compatible
 Some feature restricts copulation, such as tail feathers being too long
Behavioral Isolation:
 For survival, on group developed nocturnal habits while the other
group remained diurnal.
 Mating season or time of sexual readiness may differ.
 One group’s mating courtship behavior may not be receptive to the
other now.
 Any change in behavior that would interfere with mating
Hybrid Instability or Hybrid Viability:
 Even if copulation is achieved and offspring form, will they survive?
 Will the sperm even fertilize the egg?
 Will the mutation rate be too high for survival?
 Will the offspring survive but be sterile and unable to reproduce?
Earth: The Early Years
Precambrian to Phanerozoic
4.6 BYA to 570 MYA
The Precambrian or Cryptozoic Eon
“Precambrian” – is the term encompassing all geologic time from the earth’s origin to the
beginning of the Phanerozoic Eon. This term also applies to all rocks that lie stratigraphically
below Cambrian rocks. The Cambrian system was once thought to be the oldest rock on
earth…570 million years old…. But, whenever further studies revealed a gigantic sum of strata
that was much older, it was named the Precambrian Eon or the Cryptozoic Eon (meaning
“hidden life” because of the absence of abundant fossils). These terms refer to any
“undisturbed” rock layers lying beneath the Cambrian strata. This time frame from the
formation of the earth, 4.6 billion years ago to the beginning of the Phanerozoic Eon at 570
million years ago, comprises 88% of the entire history of the earth!!!
The Precambrian is divided into three smaller time frames also referred to as “Eons” as
follows:
I. Divisions of the Precambrian:
A. The Hadean – 4.6 BYA to 3.8 BYA
1. Early Characteristics:
 Not much rock record left…
 Some continental crust existed as long ago as 3.8 BYA as seen in
Minnesota, Greenland, and South Africa.
 During this time, the earth’s first outer crust was beginning to solidify as
ultramafic (rock high in iron and magnesium) began to cool. This early
crust was thin and mobile.
 1989 – The rock unit called the Acasta Gneiss in the PC Slave Province
of Canada is the oldest known rock to date – 3.96 BYA.
 Archean sedimentary rocks in Australia contain detrital zircons (ZrSiO4)
that date to 4.2 BYA.
 No Hadean crust exists today. It was probably ultramafic and, because of
its high density, was destroyed at subduction zones against newly formed,
less dense mafic and sialic crustal materials.
 Radiogenic Heat – the heat generated inside the earth due to radioactive
decay of certain isotopes. This caused upwellings of magma refining the
earlt Hadean ultramafic crust by partial melting and fractional
crystallization. This resulted is the separation of the mafic crustal
material (high in ferromagnesium compounds) from the sialic crustal
materials (high in silica and aluminum).
 Plate motions accompanied by subductions and collisions of island arcs
formed several sialic continental nuclei by the Early Archean.
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Stratification of the earth – As the early earth began to cool, the heavier,
denser elements such as Iron, Nickel, and Magnesium were pulled inward
under the gravitational pull. The intense pressure caused the formation of
a solid inner core of nickel and iron, surrounded by a liquid outer core
of molten nickel and iron.
The remaining bulk of materials formed the mantle that is comprised of
ultramafic materials. During the Hadean Eon, a thin ultramafic crust
formed a semi-solid (and temporary) surface of the early earth. This
stratification of the interior of the earth is important because the intense
pressures, the residual heat from the earth’s formation, and the heat
associated with the decay of radioactive elements create a “HEAT
ENGINE” of sorts.
This internal heat causes the slow rise of mobile magma belts called
magma plumes that slowly rise upward underneath the outer crust, cool,
then return to the depths of the mantel to be heated again.
This cyclic movement of mantel plumes within the earth that ultimately
moves the outer crustal plates is called magma convection and is the
driving force of plate tectonics.
2. Formation of the earth’s crust  As hot mantle plumes (the tops of convection cells deep within the earth)
slowly churned upward, the outer crust was uplifted, forming volcanic
mountain ranges. Further subjection to heat and pressure from these
mantle plumes started a series of refining processes of the ultramafic
outer crust, eventually separating the outer crust into two rock categories:
Sialic Continental Crust (Plates) and Mafic Oceanic Plates.
 These refining processes were Partial Melting and Fractional
Crystallization:
1. Partial Melting – “Sialic minerals have a lower melting
temperature than mafic minerals and ultimately become
liquid first”… Think of the ultramafic early crust as a mixture of
mafic rock material (high in iron and magnesium minerals) and
sialic rock material (high in silica and aluminum compounds).
Imagine a cube-shaped candle composed of wax with marbles
suspended within. If this “candle” were completely melted, the
marbles would sink to the bottom covered with molten wax. The
marbles are denser than the wax, so they would sink. Mafic
rock materials (i.e. basalt) has a density of 3.0 grams per cubic
centimeter. Sialic rock materials have a density of 2.7 grams
per cubic centimeter. So as the early ultramafic “mixture” was
subjected to the effects of partial melting, the denser mafics
would separate from the lighter sialics.
2. Fractional Crystallization – “Minerals with higher melting
points crystallize first in a cooling magma body. Mafic
minerals have higher melting temperatures than sialic
minerals”… If you took a handful of lead beads and another
handful of wax beads, placed them in a crucible and shook them
up, they would make a random mixture. Imagine that the lead
beads are mafic materials and the wax beads are sialic
materials. Let’s say the melting point of lead is around 9000
Fahrenheit, and the melting point of wax beads is around 1500
Fahrenheit. As you heat this mixture and the temperature
surpasses 1500F, the wax would begin to melt, but the lead
would still be in a solid state. As the temperature rises to 9000
F, both substances would become melted (assume the wax
does not ignite or vaporize). Now allow the crucible to cool. As
the temperature dropped below 9000 F, the lead would solidify,
but the wax would still be molten. The cooling lead that was
representing the mafic, denser material would sink to the
bottom. As the temperature dropped below 1500 F, everything
would be solid, but the lead beads would all be on the bottom
with the wax on top. This is how fractional crystallization
separated the mafic, denser material from the sialic, less dense
material ion the early Hadean ultramafic crust.
3. It is thought that the rock record of the Hadean has since been
destroyed because of being recycled by tectonics, and the
refining processes that formed the sialic continental plates.
3. Formation of the Continents and Ocean Basins –
 Continental Accretion - As small areas of sialic material began to
separate from the mafic material, many of the small pieces (of future
continents) fused together in a process known as continental accretion
forming the major continental plates. The thinner mafic areas between the
sialic plates would one day become the thinner, mafic oceanic crust.
 This was also a time of the formation of the ocean basins between these
early sialic continental plates. These early ocean basins were filling with
water from the out-gassing of steam from volcanic eruptions. As the water
vapor escaped from the volcanoes, it condensed into clouds and the water
precipitation flowed across the mineral-rich volcanic rocks, dissolving
minerals and carrying them to the lowlands. These mineral-rich waters
filled the basins between the continental plates forming the first oceans of
the earth. This began the Hydrologic Cycle of the modern earth.
4. Formation of the Atmosphere (from the Hadean ongoing through the Archean)
 The early atmosphere of the earth (as well as the 4 inner terrestrial
planets) prior to 4.6 BYA is thought to have had a composition similar to
that of the gas giant planet Jupiter. This would have been composed of
nitrogen, methane, ammonia, hydrogen, argon, hydrogen sulfide,
CO2, and water vapor.
 Because of cosmic winds (solar radiation), the volatiles (lighter gasses)
were “blown away” leaving behind an atmosphere from 4.6 BYA until 3.0
BYA of nitrogen, CO2, water vapor, argon, and sulfur dioxide.
 Evidence shows that from 3.0 BYA until today the atmosphere consisted
of approximately 78% nitrogen, 20% oxygen, and the remaining 2% of
CO2, water vapor, argon, and minor gasses. Where did the oxygen come
from?
 The sources of free oxygen in the atmosphere: Photochemical
dissociation and Photosynthesis. Photochemical dissociation is the
liberation of free oxygen from gas compounds in the upper atmosphere by
the actions of extraterrestrial radiation (cosmic radiation, UV radiation,
etc.). A gas such as CO2 can be released from volcanic activity and as it
travels to the upper atmosphere, it can become “broken” apart whenever
some form of radiation strikes it, releasing free oxygen. Photosynthetic
organisms (algae, early plant-like organisms, etc.) absorb CO2 and water,
and in the presence of sunlight energy and some pigment (i.e.
chlorophyll), the water molecule is split in a process called “photolysis”.
During other reactions, hydrogen atoms are bonded with CO2 forming
sugars. The oxygen originally contained within the water was released
into the atmosphere. Evidences for the early atmosphere:
 1.) Studying the effects of solar winds on atmospheric components and
comparing the compositions to that of modern-day Jupiter.
 2.) Examining “Banded Iron Formations”. In the Precambrian seas,
conditions warranted the formation of massive layers of non-oxidized iron
interspersed with layers of silica. This formed the banding effect of these
formations. Banded Iron Formations that date to a time BEFORE 3.0
BYA (in the Archean Eon) contain un-oxidized iron, since they formed in
an oxygen-poor atmosphere. Those banded iron formations forming
AFTER 3.0 BYA (Archean Eon until today) contain iron that is oxidized
indicating that it formed in an oxygen-rich atmosphere.
 3.) Analysis of gasses given off from volcanoes (“outgassing”) today
indicate that volcanic activity does not release sufficient oxygen to account
for the oxygen enrichment of the atmosphere. Indications are that
photosynthetic organisms were responsible for the oxygen enrichment.
B. The Archean – ranges from 3.96 billion years ago to 2.5
billion years ago.
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Stabilization of Earth’s Crust and Atmosphere - This was a time of
stabilization of the earth’s crust and the formation of the first forms of life
occurred forming some of the first ecosystems of the earth. The oldest
fossil forms of life on earth are “stromatolites” that are Cyanophytic Bluegreen algae appearing during this Eon, with the oldest dating around 3.5
to 3.6 billion years old. These photosynthetic organisms are thought to
have been responsible for the oxygen enrichment of the atmosphere.
From around 3.0 BYA until today, the atmosphere was pretty much the
same.
Archean Rocks – These are predominately “greenstone belts” and
“granite gneiss” complexes. The greenstone belts have a synclinal
structure and occur as linear bodies within much more extensive areas of
granite and gneiss. Typical greenstone belts can be divided into three
major rock sequences: ultramafic volcanics forming the first two, and the
upper unit consisting of sedimentary rocks of greywacke-argillite
assemblages that were deposited by turbidity currents. The presence of
the greenstone belts indicates tectonic activity as the ultramafics
contained within may represent intra-continental rifts, while those rich in
andesites may represent having formed in the back-arc marginal basins.
Late Archean Tectonic Deformation – During the Late Archean
deformation, The Canadian Continental Shield consisting of the Superior,
Slave, and other provinces were formed. This deformation was the last
major Archean event in North America. Plate tectonics similar to that of
the present did not begin until the Early Proterozoic, but it is thought that a
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type of tectonics occurred. Archean plates may have moved more rapidly
because the Earth possessed more radiogenic heat.
Archean Life – (See Origin of Life Handout) The Archean ossil record is
very poor. A few localities contain unicellular, prokaryotic bacteria fossils
– “Stromatolites”. These mats of algae not only grew in the Archean
seas, but evidence shows that they inhabited inter-tidal pools and perhaps
lowland areas. As they grew in number, they influenced weathering and
erosion rates leading to the formation of soils upon certain areas of the
continents. This helped set the stage for the exploitation of the land by
plant life in the future.
Archean Minerals – The most important Archean mineral deposits are
gold, chrome, and massive sulfides of zinc, copper, and nickel.
Algoman Orogeny – Diastrophism (bending, warping) of the Canadian
Shield//craton at 2.5 BYA resulting in the formation of extensive granite
series of the Precambrian of this time. This event is a “bookmark” in time
between the stable geologic events from Proterozoic until today (i.e. rates
of tectonic movement, other physical conditions), and the different, hotter,
faster conditions of the Archean and Hadean. The Algoman Orogeny can
be thought of as a transitional period between the Archean and the
Proterozoic.
C. The Proterozoic – ranges from 2.5 billion years ago to 570
million years ago.
General Characteristics:
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Stabilization of Earth’s Crust and Atmosphere continues throughout
the Precambrian
Continental Accretion continued forming larger continental plates
Tectonics continued into the Proterozoic until today but at a slower,
reduced rate.
Ophiolites (series of ultramafic continued to developed in the
geosynclines between the Precambrian continents
Ocean basins essentially were filled with water so that wave action, tidal
activity, and weathering and erosion were shaping the surface of the
earth.
Rain storms, lightning, carbonate and clay mineral formation were
major activities of the earth’s atmosphere and its surface rocks.
Evidences of widespread Glaciation (in the form of tillites, striated rocks,
etc.) are found in Proterozoic strata, and not seen in abundance in earlier
Archean materials.
Laurentia (North America) continued to develop platform material around
its core.
Life forms became abundant in the Proterozoic seas. Especially
during the upper Proterozoic (700MYA – 570 MYA) called the
“Ediacarian”. Some early prokaryotic life forms had already evolved into
early eukaryotic forms giving rise eventually to the first multi-celled plant
and animal organisms.
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Ediacarian refers to the strata deposited in parts of Australia during this
time of the upper Proterozoic. It contains abundant fossils of soft-bodied
organisms.
The Origin of Life
The current Hubble Telescope findings date the universe beginning (the
Big Bang) at 8 – 10 BYA or 10 – 15 BYA depending upon which
investigation is used.
The oldest known fossil = “Stromatolites” of 3.6 Billion Years Old. They are
colonies of blue-green algae that inhabited (and still inhabit) intertidal pools in
some of the more calm, reducing beachfronts of the world (i.e. Shark’s Bay
Australia)
Kingdom Eubacteria
Phylum Cyanophyta (the Blue-green Algae)
These colonies grow as irregular, spherical, rocky balls, with their outer surface
covered with a dense mat of living Cyanophytic Algae. As the algae grow, they
deposit CaCO3 inward, which over time, form larger and larger concentric rings.
In cross-section, they resemble a hailstone or layered “Jaw-Breaker” candy.
They were important in establishing free O2 in the atmosphere and changing the
sea’s chemistry from reducing to oxidative.
Where did they come from?
Where and how did life start on earth?
The Primordial Soup Theory of the Origin of Life
Life as we know it consists of molecules made up for the most part with
compounds of Carbon, Hydrogen, and Oxygen. There are many other elements
such as phosphorous, calcium, nitrogen, sulfur, etc., but it is Carbon, Hydrogen,
and Oxygen that comprise the BASIC MOLECULES OF LIFE:
1. Carbohydrates – sugars and starches used primarily for food
(energy) by most life forms
2. Lipids – the fats and oils used for energy storage and cell
membranes among other things
3. Proteins – made of combinations of amino acids, proteins are
used as building blocks for structures from cell organelles to
muscle and skin tissue
4. Nucleic Acids – Deoxyribonucleic Acid (DNA) and Ribonucleic
Acid (RNA). These compounds serve as the chemical basis of
genetic characteristics of an organism, and are used for chemical
communication within the cell. They also have the ability to
chemically store information on the replication of other
compounds.
All of these compounds occur naturally in the seas of today.
Steps of the formation of Life in the Primordial Soup:
 The age of the earth is thought to be around 4.6 BYA.
 The age of the oldest known fossil (Stromatolites) is 3.6 BYA.
 In the remote geologic past, between 4.6 BYA and around 3.0 BYA, the
seas were still forming from the “Out-gassing” of H2O vapor from
volcanoes. The H2O came from water trapped in the crystal lattices of
some minerals in magma, deep within the earth’s interior.
 As the first water-bearing clouds cooled, they rained down on the other
chemicals spewed forth from volcanoes, dissolving them and carrying this
“Mineral-Laden Water” to the low lying basins. (This is why the sea is
salty…its been a basin of deposition and collecting water runoff for billions
of years.
 Soon all of the 4 basic molecules of life were formed in this “Primordial
Soup”.
 Fats, being polarized molecules, are “hydrophobic” while in water (which is
also polarized molecules), and form small circular “Fat Bubbles” called
“Coacervates”. Even today, sea foam consists of naturally occurring fats
and oils.
 Being very delicate molecules, the nucleic acids, (DNA & RNA) would form,
but were quickly destroyed by radiation in the form of intense U.V and
background Cosmic Radiation (Radiation in the form of particles, usually
high speed photons and protons left over since the “Big Bang”). The
atmosphere was incomplete in forming at this time and offered little
protection.
 Fat and oil coacervates have the ability to offer some protection to their
contents from certain forms of radiation. It is thought that some of those
coacervates forming in the early seas trapped fragments of nucleic acids
inside, providing them a safe haven from radiation.
 Nucleic acids are not considered to be alive, but given the correct
circumstances and chemical components, they have the ability to replicate
themselves. These circumstances were met inside the coacervate.
 A cell in life forms of today reflects closely the “Proto-cells” of the early
Precambrian: they possess a phospholipid bilayer for a cell membrane that
surrounds and protects the nucleic acids of the nucleus.
 Some early “Proto-cells” utilized the absorptive feature of the fat
coacervate to absorb needed compounds directly from the environment
(Heterotrophic Metabolism as seen in animals).
 Other early “Proto-cells” may have by chance captured elements such as
magnesium that forms compounds that are reactive with sunlight. These
would form the basis of developing the ability to convert solar energy into
chemical energy (Autotrophic Metabolism as seen in plants).
 In the seas there are a variety of environments: high energy oxidative, low
energy reducing, areas of high O2 content, areas of low O2 content, high
sulfur content, low sulfur, etc. Through natural selection, certain attributes
of the cell were chosen for, and others against.
The Two Types of Cells Found in Living Organisms:
Prokaryotic & Eukaryotic
Prokaryotic cells:
1. lack a well defined nucleus
2. have circular DNA
3. have no membrane-bound organelles.
Examples of Prokaryotic Cells: Bacteria and Cyanobacteria
Eukaryotic cells:
1. have a well defined nucleus
2. have DNA molecules in the shape of a double helix
3. have abundant membrane-bound organelles
Examples of Eukaryotic Cells: Plants, Animals, Fungi, & Protists
The Endo-Symbiotic Invasion Theory of the Origin of
Eukaryotic Cells by Lynn Margulis
Lynn Margulis is a microbiologist and while studying prokaryotic bacterial
structures and comparing them to eukaryotic organelles made an interesting find.
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When she would spin down eukaryotic cells, she was able to separate the
various organelles.
One organelle, the “Mitochondrion” (an organelle used for the complete
conversion of glucose derived products into useable energy by the cell),
when separated and placed on a Petri dish with agar grew and thrived as
bacteria would. This was also the case with chloroplast organelles in
plants.
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After spinning down and separating the mitochondria and chloroplasts for
study, she found that they possessed: 1. No nucleus; 2. circular DNA; 3.
no membrane-bound organelles. In essence they were a type of bacterial
life that responds somewhat independently from the nucleus in eukaryotic
cells.
She concluded that in the geologic past, there must have been some O2
loving proto-cells that attacked some O2 hating proto-cells, and instead of
one killing the other, a mutualisticly symbiotic relationship formed whereby
the waste products of one became the necessary compounds of the other’s
survival. Hence the Anerobic/Aerobic factors in the metabolism of glucose
by the Eukaryotic cell.
These “New Cells” also were subjected to the natural selection processes
to become even more adapted and specialized to their environments.
The Metazoans: the Development of Multicellularity
The old adage is true “There is safety in numbers”…not only for people, but for
many other life forms as well.
Theories of Multicellularity:
1. Syncytial Theory: A “syncytium” is a multinucleated mass of cells such
as found in the larges muscle groups in humans. This is the site for very
quick glucose metabolism, but also the site for the formation of lactic acid
(the stiffness/soreness after overdoing it at the gym). It is thought that
multi-celled organisms arose from the internal, independent division of the
nuclei, followed by the formation of separating cell membranes between the
nuclei, creating a “Multi-celled” organism.
2. ColonialTheory: It is also postulated that multicellularity arose from
single-celled organisms forming “colonies” whereby those on the outside
of the colonies might be subjected to environmental pressures warranting
the development of a thicker outer membrane, while the cells on the interior
might develop better, more efficient means of metabolism.
No matter what, by around 700MYA (the Edicarian portion of the Upper
Proterozoic) metazoans in the form of jelly fish, soft-bodied mollusks, arthropods,
and almost all of the major Phyla of today were established in soft-body form.