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THE EARTH THROUGH TIME
TENTH EDITION
H A R O L D L. L E V I N
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1
CHAPTER 6
Life on Earth: What do Fossils Reveal?
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FOSSILS
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
burrows—called trace fossils).
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FOSSIL PRESERVATION
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).
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TYPES OF FOSSIL PRESERVATION
1.
2.
3.
4.
5.
Chemical Alteration of Hard Parts
Imprints of Hard Parts in Sediment
Preservation of Unaltered Soft Parts
Trace fossils or Ichnofossils
Preservation of Unaltered Hard Parts
Hard Parts—mineralized material such as shells
Soft Parts—soft tissue
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PRESERVATION OF UNALTERED HARD
PARTS
The shells of invertebrates and single-celled
organisms, vertebrate bones and teeth:
a.
b.
c.
d.
e.
Calcite (echinoderms and forams)
Aragonite (clams, snails, modern corals)
Phosphate (bones, teeth, conodonts, fish scales)
Silica (diatoms, radiolarians, some sponges)
Organic matter (insects, pollen, spores, wood, fur)
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CHEMICAL ALTERATION OF HARD PARTS
a.
Permineralization—filling of tiny
pores
b.
c.
d.
Replacement—molecule-by-
molecule substitution of one mineral
for another (silica or pyrite replacing
calcite)
Recrystallization—aragonite alters
to calcite
Carbonization—soft tissues
preserved as a thin carbon film
(ferns in shale)
All photos by Harold Levin
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IMPRINTS OF HARD PARTS IN SEDIMENT

Impressions
 External
molds
 Internal molds

Cast
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PRESERVATION OF UNALTERED SOFT
PARTS





Freezing
Desiccation
Preservation in amber
Preservation in tar
Preservation in peat bogs
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TRACE FOSSILS OR ICHNOFOSSILS
Markings in the sediment made by the
activities of organisms









Tracks
Trails
Burrows—in soft sediment
Borings—in hard material
Root marks
Nests
Eggs
Coprolites
Bite marks
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Art by Harold Levin
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TRACE FOSSILS OR ICHNOFOSSILS
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.
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TAXONOMY
Organisms are grouped based on their
similarities into taxonomic groups or taxa.
Broad grouping
Narrow grouping
Domain
Kingdom
Phylum (plural = phyla)
Class
Order
Family
Genus (plural = genera)
Species (singular and plural)
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BIOLOGICAL CLASSIFICATION
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.
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THE SPECIES
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.
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CLASSIFICATION OF THE HUMAN
Domain Eukarya
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo
Species sapiens
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DOMAINS
1. Domain Eukarya
2. Domain Bacteria
3. Domain Archaea
There are six Kingdoms distributed into three
Domains
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CELLS
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).
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DOMAIN EUKARYA
Organisms with eukaryotic cells (cells with a
nucleus)
•
•
•
•
Kingdom Animalia (animals)
Kingdom Plantae (plants)
Kingdom Fungi (mushrooms, fungus)
Kingdom Protista (single-celled organisms)
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DOMAIN BACTERIA
Organisms with prokaryotic cells (cells without
a nucleus)
•
Kindgom Eubacteria (bacteria and cyanobacteria
or blue-green algae)
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DOMAIN ARCHAEA
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
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EVOLUTION = CHANGE


Organic evolution refers to changes in populations
In biology, evolution is the "great unifying theory" for
understanding the history of life.
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.
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LAMARCK'S HYPOTHESIS OF EVOLUTION
Jean Baptiste Lamarck (1744–1829) 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.
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LAMARCK'S HYPOTHESIS OF EVOLUTION
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."
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LAMARCK'S HYPOTHESIS OF EVOLUTION
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.
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DARWIN'S NATURAL SELECTION
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.
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DARWIN'S NATURAL SELECTION
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.
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DARWIN'S NATURAL SELECTION
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."
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INHERITANCE, GENES, AND DNA
Gregor Mendel (1822–1884) 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.
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.
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CHROMOSOMES AND DNA
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.

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CHROMOSOMES AND DNA
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).
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DNA
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.
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REPRODUCTION AND CELL DIVISION
Reproduction in organisms may be:
 Sexual
 Asexual
 Alternation of sexual and asexual generations
All reproductive methods involve cell division.
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GENETIC RECOMBINATION
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.
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ASEXUAL REPRODUCTION


Binary fission—single-celled organisms that divide
to form two organisms
Budding—a 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).
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DIPLOID AND HAPLOID CELLS
In a human cell there are 23 pairs of
chromosomes. One of these pairs
determines the sex of the individual.
 Diploid cells—cells with paired chromosomes.
 Haploid cells—sex cells (or gametes) with only
one half of a pair of chromosomes. Example:
egg cells or sperm cells
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CELL DIVISION

Mitosis—Division of body cells of sexual
organisms. Produces new diploid cells with
identical chromosomes to the parent cells.

Meiosis—Division 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.
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RECOMBINATION OF GENES
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.

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MUTATIONS
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.
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MUTATIONS
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.
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CAUSES OF EVOLUTION
Evolution may involve change from three
different sources:
 Mutations
 Gene recombination as a result of sexual
reproduction
 Natural selection
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EVOLUTION IN POPULATIONS
Evolution is a process of biologic change that
occurs in populations.
 Population—A group of interbreeding
organisms that occupy a given area at a given
time.
 Gene pool—The sum of all of the genetic
components of the individuals in a population.
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EVOLUTION IN POPULATIONS
There is no exchange of genes between
different populations because they are
reproductively isolated.
Barriers keep their gene pools separate
(distance, geographic barriers, reproductive
barriers, etc.)
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GEOGRAPHIC BARRIERS


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.
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REPRODUCTIVE BARRIERS

Ecological isolation—Populations inhabiting the
same geographic area, but living in different
habitats

Temporal isolation—Populations that reproduce at
different times (such as plants that flower in
different seasons)

Mechanical isolation—Incompatible reproductive
organs due to differences in size, shape, or
structure

Gametic isolation—Fertilization is prevented by
incompatible gametes
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SPECIATION

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.
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SPECIATION
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.
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ADAPTIVE RADIATION
Defined as the branching of a population to
produce descendants adapted to particular
environments and living strategies.
Bill shapes are adaptations to
different means of gathering
food.
FIGURE 6-17 The honeycreepers of Hawaii
are a fine example of adaptive radiation.
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MODELING HOW EVOLUTION OCCURS
The question is not whether evolution occurs, but
rather, exactly how it occurs. What is the
mechanism of evolution?

Phyletic gradualism—gradual progressive change
by means of many small steps (old idea).

Punctuated equilibrium—sudden changes
interrupting long periods of little change (stasis).
Most change occurs over a short period of time.
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MODELING HOW EVOLUTION OCCURS
Phyletic gradualism
vs.
Punctuated equilibrium
FIGURE 6-21 Evolutionary models: (A)
punctuated equilibrium, (B) phyletic
gradualism.
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SPECIATION
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.
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PHYLOGENY—THE TREE OF LIFE
Phylogeny = the sequence
of organisms placed in
evolutionary order.
Diagrams called
phylogenetic trees are
used to display ancestordescendant
relationships.
Branches on the tree are
called clades.
FIGURE 6-22 The phylogenetic tree of horses.
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CLADOGRAMS
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.
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LINES OF EVIDENCE FOR EVOLUTION
CITED BY DARWIN




Fossils provide direct evidence for changes in
life in rocks of different ages.
Homologous structures—Certain 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 similarlooking embryos.
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OTHER LINES OF EVIDENCE FOR
EVOLUTION
1.
2.
3.
Genetics—DNA molecule
Biochemistry—similar in closely-related
organisms, but very different in more
distantly related organisms.
Molecular biology—sequences of amino
acids in proteins
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EVIDENCE FOR
EVOLUTION FROM
PALEONTOLOGY
Many examples of gradual or
sequential evolution in the fossil
record, including:
1.
2.
3.
Horses
Cephalopods and other
molluscs
Foraminifera and other
microfossils
FIGURE 6-25 Evolutionary change in
Permian ammonoid cephalopods.
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EVIDENCE FOR
EVOLUTION FROM
BIOLOGY
Homologous
structures—body
parts with similar
origin, history and
structure, but
different functions.
FIGURE 6-26 Bones of the right
forelimb from several vertebrates
reveal similarity of structure.
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EVIDENCE FOR EVOLUTION FROM
BIOLOGY
Vestigial organs suggest a common ancestry. Vestigial organs
serve no apparent purpose, but resemble functioning organs in
other animals.
FIGURE 6-27 The pelvis and femur (upper leg bone) of a whale are vestigial organs.
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EVIDENCE FOR EVOLUTION FROM
BIOLOGY
Similarity of embryos of
all vertebrates
suggests a common
ancestry.
FIGURE 6-28 Embryos of
different vertebrates.
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EVIDENCE FOR EVOLUTION FROM
BIOLOGY
Biochemistry - Chemicals (such as proteins,
antigen reactions of blood, digestive enzymes,
and hormone secretions) are more similar in
related organisms.
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EVIDENCE FOR EVOLUTION FROM
BIOLOGY
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 of
analyses.
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FOSSILS AND STRATIGRAPHY
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.
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GEOLOGIC RANGE
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.
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USING FOSSILS TO CORRELATE
ROCK UNITS
FIGURE 6-29 Use of geologic
ranges of fossils to identify
time-rock units.
Geologic range
for fossil “X”, “Y”,
and ‘z’
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USE OF COSMOPOLITAN AND
ENDEMIC SPECIES IN CORRELATION
Cosmopolitan species have a widespread
distribution.
Endemic species are restricted to a specific
area or environment.
Cosmopolitan species are most useful in
correlation
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PITFALLS OF CORRELATING WITH
FOSSILS
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
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INDEX FOSSILS
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)
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BIOSTRATIGRAPHIC ZONES
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.
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FOSSILS AND PAST ENVIRONMENTS
1.
2.
3.
Ecology = Interrelationship between organisms
and their environment.
Paleoecology = Ancient ecology; interaction of
ancient organisms with their environment.
Depends on comparisons of ancient and living
organisms (modern analogs).
Ecosystem = Organisms and their environment—
the entire system of physical, chemical, and
biological factors influencing organisms.
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FOSSILS AND PAST ENVIRONMENTS
4.
5.
6.
7.
Habitat = Environment in which an organism
lives.
Niche = Way in which the organism lives; its
role or lifestyle.
Community = Association of several species
of organisms in a particular habitat (living
part of ecosystem).
Paleocommunity = An ancient community.
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MARINE ECOSYSTEM
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
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MARINE ECOSYSTEM
Pelagic realm
Neritic zone = The water overlying the
continental shelves.
 Oceanic zone = The water seaward of the
continental shelves.

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MARINE ECOSYSTEM
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 zone—200–4000 m deep
 Abyssal zone—4000–6000 m deep
 Hadal zone — >6000 m deep; deep sea
trenches.
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MARINE ECOSYSTEM
FIGURE 6-35 Classification of marine environments.
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MODES OF LIFE OF MARINE ANIMALS
Plankton—Small plants and animals that float,
drift, or swim weakly.
• Phytoplankton—Plants and plant-like
plankton, such as diatoms and
coccolithophores
• Zooplankton—Animals and animal-like
plankton, such as foraminifera and
radiolaria
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MODES OF LIFE OF MARINE ANIMALS
Nekton—Swimming animals that live within the
water column
Benthic organisms or benthos—Bottom 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
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MARINE SEDIMENTS


Terrigenous sediment—from weathered rocks
Biogenous sediment—of 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
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CARBONATE COMPENSATION DEPTH
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.
FIGURE 6-44 Carbonate compensation depth (CCD).
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77
CARBONATE COMPENSATION DEPTH
Below the CCD (below about 4000–5000 m), water is colder,
and CaCO3 dissolves. Clay or siliceous sediments are
deposited.
FIGURE 6-44 Carbonate compensation depth (CCD).
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.
78
USE OF FOSSILS IN RECONSTRUCTING
ANCIENT GEOGRAPHY
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.
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.
79
LAND BRIDGES, ISOLATION AND
MIGRATION
Migration and
dispersal
patterns of land
animals can
indicate the
existence of:
• Former land bridge
• (Bering Strait)
• Mountain barriers
• Former ocean
barriers between
continents
FIGURE 6-46 Intercontinental migrations of camel
family members.
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.
80
SPECIES DIVERSITY AND GEOGRAPHY
Species diversity is related to geographic location,
particularly latitude.


High latitudes have low
species diversity
Low latitudes have high
species diversity.
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.
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81
USE OF FOSSILS IN THE INTERPRETATION
OF ANCIENT CLIMATIC CONDITIONS
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
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82
USE OF FOSSILS IN THE INTERPRETATION OF
ANCIENT CLIMATIC CONDITIONS
4.
5.
6.
7.
Marine molluscs with spines and thick
shells inhabit warm seas
Planktonic foraminifera vary in size and
coiling direction with temperature
Shells in warmer waters have higher Mg
contents
Oxygen isotope ratios in shells.
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83
OVERVIEW OF THE HISTORY OF LIFE
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84
OLDEST EVIDENCE OF LIFE
Remains of prokaryotic
cells (blue-green
algae or
cyanobacteria) more
than 3.5 billion
years old. Found in
algal mats and
stromatolites.
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85
EARLIEST METAZOAN ORGANISMS
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.
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86
GEOLOGIC RANGES AND RELATIVE
ABUNDANCES OF FOSSIL ORGANISMS
FIGURE 6-54 Geologic ranges and relative abundances of
frequently fossilized categories of invertebrate animals.
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.
87
EARLY PALEOZOIC—CAMBRIAN PERIOD







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
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88
LATER DURING PALEOZOIC






Trilobites
Articulate (hinged)
brachiopods
Nautiloids
Crinoids
Rugose (horn) corals
Tabulate corals
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.


Branching twig-like
bryozoans (moss
animals)
Vertebrates



Fishes
Amphibians
Reptiles
89
MESOZOIC ERA




Modern scleractinian
corals
Bivalves
Sea urchins
Ammonoids
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Vertebrates



Dinosaurs
Primitive mammals
Birds
90
CENOZOIC ERA






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
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91
EXTINCTIONS
Mass extinctions occurred at the ends of the
following periods:





Ordovician
Devonian—roughly 70% of marine invertebrates
extinct
Permian—the greatest extinction. More than 90% of
marine species disappeared or nearly went extinct
Triassic
Cretaceous—affected dinosaurs, other land animals,
and marine organisms; about 25% of all known
animal families extinct
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92
EVOLUTIONARY HISTORY OF PLANTS
FIGURE 6-53 Geologic ranges, relative abundances, and evolutionary
relationships of vascular land plants.
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93
EVOLUTIONARY HISTORY OF PLANTS
1.
2.
3.
Earliest photosynthetic organisms were
single-celled organisms during
Precambrian.
Green algae or chlorophytes may be the
ancestors of vascular land plants.
Plants invaded the land during Ordovician,
reproducing with spores.
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94
EVOLUTIONARY HISTORY OF PLANTS
4.
5.
6.
First plants with seeds appeared during
Devonian. Gymnosperms (such as
conifers). Had pollen.
Carboniferous coal swamps dominated by
seedless, spore-bearing scale trees.
Flowering plants appeared during
Cretaceous. Angiosperms. Dominant plants
today.
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95
IMAGE CREDITS
•
•
•
•
•
•
•
•
•
•
•
•
•
•
FIGURE 6-17 The honeycreepers of Hawaii are a fine example of adaptive radiation. Source: Harold Levin.
FIGURE 6-21 Evolutionary models: (A) punctuated equilibrium, (B) phyletic gradualism. Source: Harold
Levin.
FIGURE 6-22 The phylogenetic tree of horses. Source: Based on Macfaddan, B.J. 1992. Fossil Horses:
Systematics, Paleobiology, and Evolution of the Family Equidae. Cambridge: Cambridge University Press.
FIGURE 6-25 Evolutionary change in Permian ammonoid cephalopods. Source: Harold Levin.
FIGURE 6-26 Bones of the right forelimb from several vertebrates reveal similarity of structure. Source:
Harold Levin.
FIGURE 6-27 The pelvis and femur (upper leg bone) of a whale are vestigial organs. Source: Harold Levin.
FIGURE 6-28 Embryos of different vertebrates. Source: Harold Levin.
FIGURE 6-29 Use of geologic ranges of fossils to identify time-rock units. Source: Harold Levin.
FIGURE 6-35 Classification of marine environments. Source: Harold Levin.
FIGURE 6-44 Carbonate compensation depth (CCD). Source: Harold Levin.
FIGURE 6-46 Intercontinental migrations of camel family members. Source: After Ross, C., 1967,
Development of fusulinid (Foraminiferida) faunal realms. J Paleo 41: 1341-1354.
FIGURE 6-47 Species diversity ranges from low at polar latitudes to high at equatorial latitudes. Source:
Harold Levin.
FIGURE 6-54 Geologic ranges and relative abundances of frequently fossilized categories of invertebrate
animals. Source: Harold Levin.
FIGURE 6-53 Geologic ranges, relative abundances, and evolutionary relationships of vascular land plants.
Source: Harold Levin.
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96