Constructing Trees through Phylogeny and
Evolution
By: Bernice Onuoha, Will Zepeda-Campos, Edima Akpan, and Kelechi
Okereke
Phylogeny is basically the study of how closely related organisms are to one another
through what derived traits they share. Phylogeny has been used throughout time by
scientists who specialize in the study of evolution and phylogeny to figure out where and
when organisms have originated. The study of phylogeny is important so we can, for
example, trace back how we humans evolved from a common ancestor and what common
derived traits we humans shared with other organisms. It is especially crucial to know
where we humans in general come from in terms of an “arms race” with the rapid
evolution of viruses. We have constructed tree phylogenies for candy (for practice in
making phylogenetic trees), mammals, human migration, and virus evolution.
Mammal Phylogeny
For hands-on type of experience, we learned how to classify real skulls of
mammals on to phylogenetic trees according to the derived characteristics that the
mammals shared. The skulls that we were trying to classify were the echidna, hedgehog,
porcupine, monkey, human, rabbit, kangaroo, wolf, cat, and the chicken. Through
constructing the phylogenetic tree for the mammals, we were able to determine how
closely related the mammals were to each other and see the challenges of figuring which
traits go where on the phylogenetic tree and determine the order of organisms. In order
to make our diagrams, we had to physically look at the skulls and determine their
features. In terms of the timing of adaptation evolving, the time for when that trait
evolves on the phylogenetic tree can be determined if we knew about when the organisms
diverged from one another. Through classifying the organisms, we were able to
determine that hair was the most derived characteristic among all the given mammals
except for the chicken. The chicken is the out-group because it does not possess the trait
for hair, but the trait for feathers instead. The chicken is closely related to the mammals,
but possesses the least common trait. We also discovered that the trait for open-eye
sockets evolved before the chicken and the trait for the closed-eye sockets evolved for
only the human and the monkey who had a clade of their own. A couple of polytomies,
where more than two branches extend from the base of the tree diagram, emerged from
constructing this diagram like the monkey branched together with the human and the
wolf branched together with the cat and the hedgehog. In addition, convergence, where a
similar trait evolves more than once in different organisms, occurred three times on the
diagram with the trait for quills. Finally, we concluded that the rabbit was the most
derived character because of its placement being at the end of the phylogenetic tree.
Virus phylogeny
Another project we experienced was the making of a virus phylogeny. In that
project, we learned about the different strains of the swine flu virus and how it evolved
through the year. Through the phylogeny we learned that the virus has erupted recently
in large number. We know this happens because of the way that viruses and human affect
each other. Viruses and humans are in what is called an arms race, or co evolution. That
is when one species affects another species evolution. Humans and viruses are examples
of co evolution because humans create vaccines that “kill” viruses. What the vaccines do
is that they put a small amount of the virus into your immune system, so that your body
will recognize the virus when they see it. The antibodies then know what they should
attack if the virus were ever to enter into your body. Viruses mutate, and with those
mutations they can still infect. This is because when the vaccine is injected, your immune
system only knows to look out for what looks like the virus that was injected. When the
virus mutates, the immune system does not recognize it, and the antibodies do not attack
it. Every time a virus mutates, humans make new vaccines. Also, every time humans
make new vaccines, viruses mutate. Hence, you have co evolution between viruses and
humans.