Download Evidence for Evolution

Evidence for Evolution Web Quest
Lizzy Butler
April 1, 2010
Period 3
Fossil Evidence
Paleontologists are scientists who study the fossil record of ancient animals such as dinosaurs and
human’s ancient ancestors. They research historical information, and transform that data into hypotheses and
hopefully prove these theories correct by examining the evidence. The fossil record is one way to help scientists
find not only links to the past, but evidence for the process of evolution. Each new fossil shows new clues that
increase our knowledge of life’s history and help us understand questions about their evolutionary story.
One example is the fossil of the Archaeopteryx, an animal that
lived between 150 and 145 million years ago. The creature was composed
of a long bony tail, jaws with teeth, broad wings and feathers like birds,
and the skeletal features of both reptiles and birds. The discovery proved
that the hypothesis which stated that birds and reptiles were descended
from a common ancestor. Because of the Archaeopteryx, many holes were
filled in the fossil record.
Nicholas Steno of the 17th century discovered a similarity between
shark teeth and the rocks, glossopetrae, commonly called tongue stones.
This was the first perception that fossils were a record of ancient life. The
discovery led him to conclude that solid objects that form first will cause
other solids that form around the original object to conform to the shape of
the first object. The tongue stone was buried in soft sediments of dirt which hardened later into rock; meaning
the stone did not grow inside the rock. He proved this by showing that objects which hardened later – such as
tree roots growing into rocks – conform to the shape of the rocks, rather than the rocks conforming to the shape
of the tree root.
Another example is the tooth of a dinosaur, Iguanodon, which was mistaken for a large iguana. This
proved that many fossils were representations of extinct organisms. This fossil, discovered by Mantel, was the
second dinosaur fossil named; the translation of the name Iguanodon is “iguana tooth.” Many of these
Iguanodon fossils have been found around the world (Europe and America).
The ammonite fossils contains holes that scientists’ derived to be the bite mark of a mosasaur which is a
predatory marine reptile which lived during the same time period. It is argued that the punctures are related to
the shapes and capabilities of mosasaur teeth and jaws as well as the holes being created by limpets attached to
the fossil.
“Iguanodon.” Enchanted Learning. EnchantedLearning.com, 2009. Web. 20 Mar. 2010. <http://www.enchantedlearning.com/subjects/dinosaurs/
dinos/Iguanodon.shtml>.
“The Theory of Evolution.” Biology: The Dynamics of Life. Columbus: McGraw-Hill Companies, 2004. 392-419. Print.
University of California. “Nicholas Steno.” Evolution Entrance. UC Museum of Paleontology, 2006. Web. 24 Mar. 2010.
<http://www.ucmp.berkeley.edu/history/steno.html>.
O’Neil, Dennis. “Evidence of Evolution.” Early Theories of Evolution. N.p., 12 Mar. 2010. Web. 18 Mar. 2010. <http://anthro.palomar.edu/evolve/
evolve_3.htm>.
Anatomical Evidence
Scientists use comparative anatomy to determine the relationships between species and populations.
Scientists look at three facets of an organisms’ anatomy to determine their evolutionary path. They look at
vestigial, homologous, and analogous structures across species to help them identify common ancestors and
environments. By examining this evidence, scientists can determine what species are related to each other, and
which species have evolved independently of each other. Taxonomists use these similarities to classify animals
into species and genus. Two early scientists who used anatomical evidence in furthering the theory of evolution
were Lamarck and Buffon.
Vestigial structures are parts of a body that no longer serves a useful function for the organism, but are
still inherited as part of the body plan for the species. Vestigial comes from the Latin word vestigium, meaning
sign. The blind eyes of naked-role rats and cavefish are vestigial because the animals no longer use them for
sight.
Homologous structures are those that are similar in function
and appearance between species. The forelimbs of many mammals,
such as humans, cats, whales, and bats are very similar. All these
forelimbs show the presence of digits at the end of the forelimb, even
though in whales and bats the flesh and skin link the digits together
into a seamless whole, the bones underneath are separate. Even
though the organisms make different use of these forelimbs, the
similarities in structure have led scientists to conclude that they are
all descended from a common ancestor.
Analogous structures are those that serve a common purpose, but are different in structure or design.
Although the wings of butterflies and birds perform similar functions, they are different in form and structure.
Scientists have concluded that these species evolved independently from each other, but adapted to similar
lifestyles.
Scientists use anatomical similarities among a variety of species to group them into Genera. The species
that make up a genus have evolved from a recent (in evolutionary terms) common ancestor. For example, the
members of the genus Canis exhibit many anatomical similarities. Wolves and dogs are close relations to each
other. While they show some similarities with foxes, their common ancestor would have been further back in
the evolutionary chain.
“Evidence for Evolution.” SparkNotes. SparkNotes, 2010. Web. 23 Mar. 2010. <http://www.sparknotes.com/biology/evolution/evidence/section3.rhtml>.
“Evidence for Evolution Can Be Found in Other Fields of Biology.” Evidence for Evolution. Txtwriter, 2008. Web. 22 Mar. 2010. <http://txtwriter.com/
Backgrounders/Evolution/EVpage11.html>.
“Homologies: anatomy.” Understanding Evolution. UCMP, 2010. Web. 22 Mar. 2010. <http://evolution.berkeley.edu/evolibrary/article/0_0_0/lines_05>.
O’Neil, Dennis. “Evidence of Evolution.” Early Theories of Evolution. N.p., 12 Mar. 2010. Web. 18 Mar. 2010. <http://anthro.palomar.edu/evolve/
evolve_3.htm>.
“The Theory of Evolution.” Biology: The Dynamics of Life. Columbus: McGraw-Hill Companies, 2004. 392-419. Print.
Embryology Evidence
An embryo is the earliest stage in the growth and development of multi-cellular organisms. When
embryologists see that young embryos from different species exhibit shared features, it provides the evidence
that the species evolved from a distant, common ancestor. Different species in the same Class tend to have very
similar or identical embryos, but then develop more specialization as the embryo grows. According to some
sources, “the embryo serves as a microcosm for evolution, passing through many of the stages of evolution to
produce the current state of the organism.” In addition, homologous structures may appear in stages of
embryonic development, but then disappear when the organism develops into an adult.
Embryos display our evolutionary history. Fish, reptiles, birds, and mammals all will undergo different
stages of embryonic development, but at some stage will show signs of similarity. In the early stages of
development, all of the embryos will have a tail and pharyngeal pouches. These pouches will develop into
supports for gills in fish; in the other animals the pouches will develop into parts of the ears, jaws, and throat.
These shared features lend credence to the theory that these animals have developed from common ancestors.
The embryos of snakes show that at one time in their evolution snakes had limbs. Some species alive
today have limb-buds as early embryos, but then lose these buds during their development. Others develop these
buds into vestigial structures. The study of the developing embryos of snakes, along with the fossil evidence of
ancient snakes displaying hind limbs, provides support for the theory that snakes developed from limbed
ancestors.
Human embryos provide evidence of our own evolution. Specifically, every human embryo has a long
bony tail, the vestige of which we carry to adulthood as the coccyx at the end of our spine. Early in the
development, we also show gill slits just as fish display. Additionally, human fetuses have a fine fur during the
fifth month of development. These developments show that new instructions get layered on top of old ones,
suggesting the course that the evolution of the human species has followed.
“Evidence for Evolution.” SparkNotes. SparkNotes, 2010. Web. 23 Mar. 2010. <http://www.sparknotes.com/biology/evolution/
evidence/section3.rhtml>.
“Evidence for Evolution Can Be Found in Other Fields of Biology.” Evidence for Evolution. Txtwriter, 2008. Web. 22 Mar. 2010.
<http://txtwriter.com/Backgrounders/Evolution/EVpage11.html>.
O’Neil, Dennis. “Evidence of Evolution.” Early Theories of Evolution. N.p., 12 Mar. 2010. Web. 18 Mar. 2010.
<http://anthro.palomar.edu/evolve/evolve_3.htm>.
“The Theory of Evolution.” Biology: The Dynamics of Life. Columbus: McGraw-Hill Companies, 2004. 392-419. Print.
Biochemistry Evidence
Biologists, scientists who study life, and chemists, scientists who study the composition of matter,
combine to study the field of biochemistry in the search of evidence for evolution. Since the discovery of DNA
in the 1950’s, scientists have been able to study the similarity and differences in DNA between different
species. Organisms that are considered “biochemically similar” contain less differences in their amino acid
sequences. If these organisms had developed from different ancestors, then we would expect there to be more
differences in their DNA.
Since Charles Darwin, scientists have created evolutionary
diagrams which represent levels of similarity among different species.
Originally, these diagrams were drawn based on observable features and
behavior. Then in the 1970s, some biologists used RNA and DNA
nucleotide sequences to construct these diagrams. Their reasoning was that
if two organisms have similar features and structures, and DNA molecules
are the code used by the organisms to develop these features and structures,
then the DNA molecules should be similar. Additionally, scientists also
compared the sections of DNA and RNA that were not directly related to
the coding for specific features. If evolution had not occurred, then these
“junk DNA” strands would show little or nor similarity. However, these
strands show the same levels of similarity as those for other parts of the
genome. This observation only makes sense if evolution has occurred.
We can study the process of natural selection – which normally
happens over millennium – in a significantly shorter period by observing
the behavior of bacteria in a Petri dish. When a lethal dosage of antibiotic is added to the Petri dish, there will
be a mass die-off of the bacteria. Some bacteria will survive displaying immunity to the antibiotic. The next
generation will most likely be immune to the antibiotic, because they will have inherited the immunity from the
surviving population. These bacteria will continue to produce succeeding generations that are immune to the
antibiotic.
“The Molecular Record.” Evidence for Evolution. Txtwriter, 2008. Web. 22 Mar. 2010. <http://txtwriter.com/Backgrounders/
Evolution/EVpage13.html>.
O’Neil, Dennis. “Evidence of Evolution.” Early Theories of Evolution. N.p., 12 Mar. 2010. Web. 18 Mar. 2010.
<http://anthro.palomar.edu/evolve/evolve_3.htm>.
“The Theory of Evolution.” Biology: The Dynamics of Life. Columbus: McGraw-Hill Companies, 2004. 392-419. Print.