Evidence for Evolution Web
Quest
Yanique Bell
April 1, 2010
Period 9/10
Fossil Evidence
Fossils have been used by scientists since as early as the seventeenth century. Fossils are physical
evidence of historic organisms. They are used as proof of what organisms lived in the past. Paleontologists are
scientists who study existing life forms through the use of fossils. There are five types of fossils: trace, casts,
molds, petrified or permineralized, and amber-preserved or frozen fossils. To explain, a trace fossil is any
indirect evidence left in a sedimentary rock, like a footprint. A cast is formed when rock minerals fill the empty
space left by a decayed animal and an identical shell is formed. A mold is a fossil that is formed when an
organism is buried in sedimentary rocks leaving an imprint. A petrified fossil is formed when minerals go
through and replace the hard parts of an organism or fill up the empty spaces of the organism. Finally, frozen
fossils are fossils of an entire organism frozen in ice or amber from tree sap (Biggs 370-371, 1127). Clearly,
many fossils formed millions of years ago and scientists are able to gather information from them today.
Furthermore, paleontologists use these fossils in several ways as evidence of evolution. For example,
fossils can be used to compare existing species to extinct ones. To illustrate, in the 17 th century Nicholas Steno
found that “tongue stones” resembled shark teeth. It turned out that the “tongue stone” was a fossil of a tooth of
a shark that was extinct. Second, fossils can also be used to determine the behavior of past organisms and how
they interacted with their environment. To explain, a trace fossil was left on a cast fossil of an ammonite.
There was several bite marks thought to be from a mosasaur, a carnivorous marine lizard, on the ammonite
fossil. Scientists concluded that it would have been possible for the mark to be from a mosasaur because they
are predators and their teeth and jaw size and shape are similar to the marks. Plus, there are other possibilities
such as limpets that could have made these marks. This fossil evidence can tell paleontologists what and how
mosasaurs ate or how limpets interacted with their environment. In addition, fossils can also be viewed on a
cellular level. In explanation, the photo on the left is of a thigh bone of a duckbill
dinosaur called Maiasaura. This fossil shows that this organism had many blood
vessels which are represented by the white spots; this means that it grew quickly. The
dark, almost black, curvy line towards the center shows a period of time when the
organism stopped growing for a while (Fossil evidence). Finally, fossils are also used
to show transitional forms. Transitional forms are evidence of changes. An example
of transitional forms is that in the skull of a Pakicetus, which is one of the early
ancestors of a whale. The nostrils of the Pakicetus fossil was low showing that it was once a land animal. Then
as paleontologists discovered other whales and saw that over time their noses became closer to the top of the
skull, they were able to conclude that the whales changed from being a land animal to a sea inhabitant
(Transitional forms). Clearly, fossils are a great source of evidence.
Biggs, Alton, et al. Biology: The dynamics of life. New York, New York: McGraw Hill, 2004. Print.
Fossil evidence. N.p., 2004. Web. 27 Mar. 2010. http://evolution.berkeley.edu/evolibrary/article/0_0_0/lines_02.
Transitional forms. N.p., n.d. Web. 27 Mar. 2010. <http://evolution.berkeley.edu/evolibrary/article/0_0_0/lines_03>.
Anatomical Evidence
Anatomically, we are all made of the same basic elements and have similar structures and processes. In
fact, all living things are made of the same six elements. Also, although there are an immense amount of living
things on Earth, they all consist of twenty amino acids. By using anatomical evidence, it is safe to say that
organisms that are very similar came from the same ancestor. Anatomical evidence can be used in many ways.
First, invertebrates are organisms with an internal skeleton, such as, dogs, cats, birds, whales, and seals. These
organisms all have the same type of bones inside their arms; they all have a humerus, radius and ulna. Due to
the fact that these vertebrates have similar structures scientists are able to conclude that all vertebrates evolved
from the same ancestor (Biggs 400-402). The bones in this case would be considered homologous structures,
because they emanated from the same ancestor. Homologous structures are similar in arrangement, function or
both. Next, if organisms have structural or functional similarities, they do not have to be closely related; these
are known as analogous structures. Analogous structures are body parts that have a similar function but do not
have the same ancestor. For instance, birds and butterflies both have wings. These wings do not have similar
structures but they are similar in function in allowing both organisms to fly. Bird and insect wings are not
related and evolved over time separately from each other because they have two completely different groups of
ancestors. Clearly, analogous structures do not prove that the organisms’ ancestors are related. On the other
hand, it does show some evidence of evolution. From the wings of flies and butterflies anatomists, scientists
who specialize in anatomy, can tell that they most likely evolved away from each other and their ancestors
independently adapted to their similar surroundings and lifestyles. To continue, vestigial structures are body
parts in a currently living organism that is no longer used for its original job. Vestigial structures show
evolution because the structure was used by the species’ ancestors. The species would have had to evolve and it
was no longer in need but is still passed on to every generation. Anatomists can study
vestigial structures in animals like the baleen whale who has a pelvic bone that is no
longer needed and try to figure out what their ancestors were and what they used this
body part for (O’Neil). In addition, in 1798 a French anatomist, É´ienne Geoffroy St.
Hilaire, traveled to Egypt with Napoleon and he saw and described a Cassowary bird that no longer used its
wings to fly. Instead of using its wings to fly as its ancestors did it now uses its wings to balance when running
and to attract attention when mating (Miller). Another way that anatomical evidence is used is to compare
organisms. For example, scientists have compared the forelimbs of mammals like humans, whales, dogs and
bats and they have the same amount of bones and structure, but different function; this means they share those
homologous structures and evolved from a common ancestor. Hence, anatomic evidence is used in many ways
to find evolutionary evidence or relationships (Comparative).
Biggs, Alton, et al. Biology: The dynamics of life. New York, New York: McGraw Hill, 2004. Print.
Miller, Brandon. “The top 10 useless limbs (and other vestigial organs).” LiveScience. N.p., 2010. Web. 28 Mar. 2010. <http://www.livescience.com/
animals/top10_vestigial_organs-1.html>.
“Comparative anatomy.” Science.jrank. N.p., 2010. Web. 28 Mar. 2010. <http://science.jrank.org/pages/348/Anatomy-Comparative.html>.
O’Neil, Dennis. “Evidence of evolution.” Anthro.palomer. N.p., 2010. Web. 28 Mar. 2010. <http://anthro.palomar.edu/evolve/evolve_3.htm>.
Embryology Evidence
Biologists study life, living organisms and their build up,
function, development, where they came and evolved from; this
includes embryology. Embryology is a branch of biology that studies
how
embryos
(Embryology).
form,
develop,
their
structure
and
function
An embryo is the earliest stage of growth and
development in plants and animals. By comparing and contrasting
embryos, scientists can find evidence of evolution. For example,
when looking at the embryos of a fish, bird, reptile, bird and mammal, it is clear that they look very similar and
almost identical. Each embryo has a tail and pharyngeal pouches. These pouches develop into different parts of
the body in each organism. The pouch forms gills in fish, but they form ear, jaw, and throat body parts in the
reptile, bird, and mammal. Overall, these similar embryos tell biologists that these organisms evolved from the
same ancestor (Biggs 402). Furthermore, embryos can be compared but the way they develop can also show
proof of evolution. To demonstrate, human embryos along with rabbits, dogs and apes, undergo a stage of
development where they have a tail. Also, at some point in development, humans have a fish like heart, gillslits and circulatory system. These similarities in development show that mammals, birds and reptiles probably
evolved from fish like ancestors (Embryological). Next, scientists are also able to view the development of the
embryos. Although, Ernest Haeckel (1834-1919), a German biologist, created inaccurate drawings of embryos
to prove that he was right about certain embryos being similar from the first stage of development, he was not
completely wrong about the similarities of the embryos. Invertebrates, fish, and other groups of organisms do
not look completely identical at the beginning of development. On the other hand, during some stages a group
of organisms develop a familiar trait. For example, during one stage, all vertebrates develop a two chambered
heart with a single circulation. Then, as development continues, embryos gain their special features and they no
longer look identical. For instance, looking at the embryos of a pig and human, they look very similar but the
adults have no resemblance. Therefore, by analyzing the development of embryos scientists can see what
structures the organisms’ ancestors had and their many adaptations during evolution (Comparative). Clearly,
embryological evidence is very useful.
Biggs, Alton, et al. Biology: The dynamics of life. New York, New York: McGraw Hill, 2004. Print
“Embryology.” Dictionary.com. N.p., 2010. Web. 28 Mar. 2010. <http://dictionary.reference.com/browse/
embryology>.
“Embryological evidences of evolution.” Transtutors. N.p., n.d. Web. 28 Mar. 2010.
<http://www.transtutors.com/homework-help/Biology/Evidences+of+Evolution/embryologicalevidences-of-evolution.aspx>.
“Comparative embryology.” Tutorvista. N.p., 2008. Web. 28 Mar. 2010. <http://www.tutorvista.com/content/
biology/biology-ii/heredity-and-evolution/comparative-embryology.php>.
Biochemistry Evidence
Biochemists study biochemistry, a combination of biology and chemistry.
Biochemistry is the
chemistry of living organisms. A great amount of proof for evolution comes from biochemistry evidence
because almost all organisms have DNA, ATP, and enzymes. First, biochemistry evidence can be used to prove
relationships between organisms. To explain, the enzyme cytochrome c is located in many different organisms.
Biologists can use cytochrome c to see how diverse or similar species are by finding the amino acid sequences
in this enzyme and comparing them. If the sequence is very different then the species are also very different
and probably evolved separately. Meanwhile, if there are fewer differences and many similarities then they are
closely related and most likely share a close ancestor (Biggs 402-403). So, the cytochrome of cows and
monkeys are more similar than those of monkeys and fish. This means that cows and monkeys are more similar
(Evolution). Furthermore, protein homologies are great evidence of evolution. To explain, all organisms, from
cats to whales, are made of the same twenty amino acids. This suggests that all organisms were originated from
the same organism. Plus, the protein, hemoglobin, has many different amino acid sequences that have the same
function. The reason why these proteins are so similar in many different organisms is due to the fact that they
probably evolved from the same ancestor (Cline).
Moreover, genetic homologies are also used as biochemistry evidence to prove that all organisms
descended from the same organism. In explanation, all organisms have the same four bases that make up their
DNA. These bases can base pair with other bases from other organisms as well. Second, all organisms use
ATP as an energy storing molecule. This and many other biochemistry evidence proves that all organisms have
a common ancestor but non believers might believe that these common factors in every organism are due to the
divine plan of whatever god they worship. This is a very controversial part of evolution and debates will
continue to go on. To conclude, biochemistry is one of the best sources of evidence because there is a lot of
detailed evidence and it always leads to organisms originating from the same organism (Cline).
Currently, scientists are continuing to use fossils, anatomy, embryology and biochemistry in their
searches and connections to evolution. These forms of evidence support the theory of evolution that is known
today. Therefore, the theory of evolution will continue to change as scientists continue to discover more and
more evidence of evolution.
Biggs, Alton, et al. Biology: The dynamics of life. New York, New York:
McGraw Hill, 2004. Print
Cline, Austin. “Genetic & protein homologies - How genetic & protein
homologies prove evolution.” About.com. N.p., 2010. Web. 28 Mar. 2010.
<http://atheism.about.com/od/evolutionexplained/a/
GeneticProteinHomologies.htm>.
“Evolution.” Earlham. N.p., n.d. Web. 28 Mar. 2010.
<http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html>.