Transcript Evolution

Biological Diversity

Variety in living things
Evolution
Changes over time.
 The process by which modern organisms
have descended from ancient organisms.

The Problems
Hoaxes (Piltdown Man,
 Fossil evidence was sporadic
 Geology and Biology are both young
sciences….only 300 years old.
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The Piltdown Man
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The "Piltdown Man" is a famous hoax consisting of
fragments of a skull and jawbone collected in 1912 from a
gravel pit at Piltdown, a village near Uckfield, East Sussex, in
England. The fragments were thought by many experts of the
day to be the fossilized remains of a hitherto unknown form of
early human. The Latin name Eoanthropus dawsoni
("Dawson's dawn-man", after the collector Charles Dawson)
was given to the specimen.
The significance of the specimen remained the subject of
controversy until it was exposed in 1953 as a forgery,
consisting of the lower jawbone of an orangutan combined
with the skull of a fully developed, modern man.
The Piltdown hoax is perhaps the most famous
paleontological hoax in history. It has been prominent for two
reasons: the attention paid to the issue of human evolution,
and the length of time (more than 40 years) that elapsed from
its discovery to its full exposure as a forgery.
Hoax….Archaeoraptor liaoningensis
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In October 1999 paleontologist Philip J. Currie of the
Royal Tyrrell Museum of Paleontology in Drumheller,
Alberta along with Stephen Czerkas of the Dinosaur
Museum in Blanding, Utah, and Xing Xu of the
Institute of Vertebrate Paleontology and
Paleoanthropology in Beijing announced the
discovery of Archaeoraptor at a National
Geographic Society press conference in Washington,
D.C.
The fossil was considered to be a missing link
between birds and dinosaurs because it manifested
the long bony tail of dromaeosaurid dinosaurs and
the specialized shoulders and chest of birds.
Continued…..
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Let it be noted that this fossil did not even make it to
peer review. Science doing what science does and
scientists doing what real scientists do have revealed
this fossil (or rather fossils) for what it is. This is not
an embarrassment for science but a reason for
science to stand proud. This fossil was rejected
during the most preliminary of studies - it did not
even reach the first step of scientific acceptance, that
of description. While laypeople may not understand,
publication in National Geographic, which is a
general interest magazine for the public and not a
peer reviewed scientific journal, is not scientific
recognition and acceptance.
Problems
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(Williamson, 1981, p.214). "Scientists have dug up
fossils of what they say are some of the earliest
ancestors of modern sea turtles. The 110 million
year old fossils of several turtles are the earliest
remains of their kind found in Australia.
Palaeontologists from the South Australian
Museum and the University of Adelaide made the
discovery, from the Early Cretaceous period, at a
dig near Boulia in western Queensland. Research
scientist Dr Ben Kear says the fossils suggest the
Cheloniidae family of modern turtles had some of
their earliest origins in Australia. "They look like
they might be at the base of the modern sea
turtle," he says. ... One of the Boulia fossils was
"about as complete as you can get with fossils",
Kear says, showing the turtle's blood vessels,
nerve channels and muscles, and allowing
detailed exploration of the brain cavity. He says
the turtle closely resembled a modern sea turtle."
(Skatssoon J., " Early turtle ancestor found," ABC,
21 February 2005) [Another example of stasis, i.e.
no evolution. - for ~110 million years.]
Problems
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"A spider relative called a harvestman trapped in amber could shed light on how
arachnids were affected by the extinction that wiped out dinosaurs. The 100million-year-old arachnid, which looks like it might have died last year, wandered
though a dinosaur-dominated world. .... "This specimen came from the Mesozoic
Era, so basically the same time as the dinosaurs and generally there are very
few fossil arachnids from this period," said co-author Jason Dunlop. ... One of the
reasons this specimen is causing excitement is that it might help tackle the
question of how many arachnid groups managed to survive the great extinction
of around 65m years ago. ... . The harvestman hit on a successful evolutionary
"design" fairly early on and has changed rather little over the past few hundred
million years. "We think they would have lived a similar life to modern
harvestmen," said Dr Dunlop. "If you go back to a very, very ancient fossils and
look at the internal organs, you see it actually has reproductive organs just the
same as a living one; it has a breathing system the same as a living one. So, it
looks like there hasn't been any major change in the body plan." ... [So yet
another example of stasis (no evolution for ~300 million years! How many
generations? How many environmental changes? And this "100-million-year-old
arachnid, ... looks like it might have died last year"!] ("Arachnid's clue to dino
wipeout," BBC. 18 May, 2005). [So yet another example of stasis, i.e. no
evolution - for ~300 million years! How many generations? How many
environmental changes? Yet no RM&NS? And this "100-million-year-old arachnid
... looks like it might have died last year"!] [top]
Support
The gradual change of fins to feet.
Interesting Link for deep reading
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http://plato.stanford.edu/entries/evolution/
Support for Gradual Change
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The anatomy of the hand of a blue
whale.
Support for Gradual Change
Evidence for Evolution and Controversy
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Fossils offer evidence that life on the
earth is measured in millions and billions
of years, rather than thousands as
believed by young-earth creationists.
Fossils also reveal that there are ancient
forms of organisms that no longer exist;
in other words, that extinction is a fact.
The geologic time scale shows the
history of life on earth, as determined by
the fossil record.
Continued…..
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In addition, the fossil record supports the
view that events of speciation are normally
concentrated in geologically short periods
of time, and that species tend to remain
morphologically stable throughout most of
their existence. Such a fossil record is
consistent with the theory of punctuated
equilibrium as presented by Stephen Jay
Gould and Niles Eldredge.
This is currently contrary to the theory of small changes over time
according to the evolutionary hypothesis. This theory seems to be true
for time scales within geologic strata.
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The fossil record also offers evidence of the theory
of descent with modification—that organisms
descend from common ancestors. For example,
Georges Cuvier documented that the lower (older)
the rock strata, the more different the fossils were
from living organisms. Indeed, fossils found in more
recent geological strata tend to be very similar to, or
indistinguishable from living species, but fossils in
older geological strata tend to be markedly different.
Fossils also reveal that organisms of increasing
complexity have appeared on the earth over time.
This is consistent with the view that each stage
builds upon preceding stages. Fossil evidence that
supports the view of species stability throughout
their existence, and sudden appearances of new
species, is not problematic for the theory of descent
with modification, but only with Darwin's concept of
gradualism.
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Some fossils have been considered to be transitional
fossils—having characteristics that appear to be
between the (assumed) ancestral and descendant
forms. For example, Archaeopteryx has been
presented as a transitional fossil between reptiles and
birds. In 2006, a fossil fish (Tiktaalik roseae) was
found in northern Canada that appeared to bridge the
gap between fish and tetrapods (four-legged
vertebrates), looking like a cross between a fish and a
crocodile. However, few transitional fossils have been
reported, and many scientists are cautious about
these findings. Among other problems,
Archaeopteryx, which appears fully formed in the
fossil record, is not preceded or followed by fossils
showing a gradual transition between reptiles and
birds and, according to some theories of bird
evolution, appears to have lived after the common
ancestor. In general, the gap between separate fossils
is so large that it is difficult to be definitive on
ancestral-descendant relationships.
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One of the problems with fossil evidence for evolution
is that there are few gradually sequenced
intermediary forms. Fossil lineages from therapsid
reptiles to mammals, between supposed land-living
ancestors of the whales and their ocean-living
descendants, and from an ancestral horse (Eohippus)
to the modern horse (Equus) are reasonably wellrepresented. But, generally, discontinuities or gaps
are found in phyletic series rather than a gradual
change from ancestral forms to descendant forms.
The incompleteness of the fossil record is one
explanation given for this, as well as rapid speciation
via punctuated equilibrium.
What fossil evidence does not support is the view of
natural selection as the creative force of evolution
(theory of natural selection). Rather, the fossil record
is neutral with respect to the mechanism of
evolutionary change.
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Archaeopteryx is a Jurassic
fossil bird that shares both bird
and reptile features; it is widely
accepted as the earliest and
most primitive known bird.
Fossils show the presence of
wings and feathers, as in birds,
but also teeth (which modern
birds do not have), claws on the
wings, and a long, lizard-like tail,
with tail vertebrate, such as with
reptiles (Mayr 2001). The
description of the first intact
specimen in 1861 (two years
after Charles Darwin published
The Origin of Species), set off a
firestorm of debate about
evolution and the role of
transitional fossils that endures
to this day.
Further support of evolution
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Over the years, ten specimens of
Archaeopteryx have been found, all in a
limestone deposit near Solnhofen,
Germany. The fine-grained limestone,
which preserves detailed casts of features
not often fossilized, is used by artists and
printers for lithographic plates, thus the
species name Archaeopteryx lithographica.
These fossils are attributed to the Upper
(or Late) Jurassic period, about 145 million
years ago.
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As a fossil that fills a large gap between
reptiles and birds, Archaeopteryx has been
referred to as a missing link (Mayr 2001).
At one point, it was also widely considered
a direct ancestor of modern birds, but
many current paleontologists view it now
as a side branch. There are divergent
theories on whether birds arose from
archosaurian reptiles in the late Triassic,
more than 200 million years ago, or from
theropod dinosaurs in the more recent
Cretaceous, about 80-110 million years
ago. The two camps, understandably, view
differently where Archaeopteryx fits in the
scheme between reptiles, or dinosaurs,
and modern birds.
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Since its timely discovery in 1860 and description the
next year, shortly after Darwin predicted such
transitional fossils in The Origin of Species,
Archaeopteryx has been presented as evidence for
Darwin's theory of descent with modification. As such it
has gained a great deal of notoriety, not only in
scientific discourse but also in textbooks and the public
media. Nonetheless, despite the significance attributed
to this species, Archaeopteryx does not significantly
illuminate possible transitions between
reptiles/dinosaurs and birds, since it appears in the
fossil record fully formed, with a lack of any transitional
forms between reptiles or dinosaurs and itself. The
history surrounding Archaeopteryx does reveal,
however, much about the process of science, with
competing theories espoused by different camps, and
at times a tendency to espouse seemingly definitive
conclusions beyond that of the known facts.
It is unclear where Archaeopteryx fits in the evolution of birds. There
are two major conjectures regarding the origin of birds. The
thecodont theory holds that birds arose from archosaurian reptiles,
perhaps in the late Triassic more than 200 million years ago. The
dinosaurian theory holds that birds evolved from theropod dinosaurs
at an earlier date.
 Some consider Archaeopteryx to be a powerful piece of evidence
that birds evolved from dinosaurs. The skeleton is similar to the
dinosaurs of the families Dromaeosauridae and Troodontidae.
However, Archaeopteryx also presents a complication in this matter.
The most bird-like, bipedal dinosaurs, which are presented as the
ancestors of birds, actually trace to the Cretaceous, about 70 to 100
million years ago, or well after Archaeopteryx, the earliest known
bird, had disappeared.
 Mayr (2001) feels that Archaeopteryx, which lived 145 million years
ago in the Jurassic, has so many advanced avian characters that the
original birds must have existed sometime earlier, perhaps in the
Triassic, 200 million years ago. Yet, there have not been any bird-like
dinosaurs known from the Jurassic, or earlier. This would offer
support for the view that birds arose from archosaurian reptiles.
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TimeScales
Deep Time
 Geologic Time Scale
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Darwin’s Theories
Individual organisms in nature differ from
one another. Some of this variation is
inherited.
 Organisms in nature produce more
offspring than can survive, and many of
those that survive do not reproduce.
 Because more organisms are produced
than can survive, members of each species
must compete for limited resources.
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Darwin’s Theories contin….
Because each organism is unique, each has
different advantages and disadvantages in the
struggle for existence.
 Individuals best suited to their environment
survive and reproduce most successfully.
The characteristics that make them best
suited to their environment are passed on to
offspring. Individuals whose characteristics
are not as well suited to their environment die
or leave fewer offspring.
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Darwin’s Theories Contin….
Species change over time. Over long
periods, natural selection causes
changes in the characteristics of a
species, such as in size and form. New
species arise, and other species
disappear.
 Species alive today have descended
with modifications from species that
lived in the past.
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Darwin’s Theories Contin…
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All organisms on
Earth are united
into a single tree
of life by common
descent.
Voyage of the HMS Beagle
Hutton’s Theory of Geologic Change
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In 1785, the geologist James Hutton
published a detailed theory about the
geologic forces that have shaped Earth.
He proposed that layers of rock form very
slowly. Also, some rocks are moved up by
forces beneath Earth’s surface. Others are
buried, and still others are pushed up from
the sea floor to form mountain ranges. The
resulting rocks, mountains, and valleys are
then shaped by natural forces. These
processes happen over millions of years.
Lyell’s Principles of Geology
Charles Lyell stressed that scientists
must explain past events in terms of
processes that they can actually
observe.
 Processes that shaped the earth millions
of years ago are happening in the
present.
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Lamarck’s Theory of Evolution
In 1809, Lamarck published his theory of
how organisms changed over time.
 He proposed that by selective use or
disuse of organs, organisms acquired or
lost certain traits during their lifetime.
These traits could then be passed on to
their offspring. Over time, this process
led to change in a species.
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Lamarck’s Theories
Tendency toward Perfection - All
organisms have an innate tendency
toward complexity and perfection.
Changing features help them to be more
successful in their environment.
 Use and disuse  Acquired characteristics could be
inherited.
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Problems with Lamarck’s Theories
Lamarck did not know how traits were
inherited.
 Behavior has no effect on inheritable
characteristics.
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Population Growth
In 1798, Thomas Malthus observed that
babies were being born faster than
people were dying.
 He reasoned that if the human
population continued to grow
unchecked, sooner or later there would
be insufficient living space and food for
everyone.
 Forces that worked against growth were
war, famine, and disease.
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