Download earth 101 basic evidence for evolution still stands after 150 years

Earth 101 Basic Evidence for Evolution Still Stands After 150 Years
By Rob Ross and Trisha Smrecak, The Ithaca Journal
February 6, 2009
Feb. 12, 2009 is a very significant day. It's the bicentennial of Lincoln's birth, but it's also
a significant date in the biological community: the 200th birthday of Charles Darwin. This
year also marks the 150th anniversary of the publication of his book, "The Origin of
Species." Thus, the week of Feb. 7-14 is one of celebration in museums, universities
and cities around the world.
In Ithaca, people are coming together to present on evolution, science, and its
relationship to society today as part of "Ithaca's Darwin Days;" a collaboration between
Cornell University and the Museum of the Earth. Darwin convinced the scientific
community of the theory of evolution. Today, there are six basic evidences for evolution,
and all but genetics were apart of Darwin's original arguments.
Exhibit A: Biogeography - Organisms don't live everywhere they can possibly survive,
and similar species are usually found in the same geographic region. For example,
marsupials, like possums and kangaroos, are only found in the Americas and Australia,
though other regions could support them. This is because they evolved from a common
ancestor when South American and Australian continents shared a connection because
of plate tectonic movement. After South America and Australia split, marsupials evolved
differently in each locality.
Exhibit B: The Fossil Record - Geologists observed a consistent change in fossil
organisms found in lower, older, rocks to those in higher, younger, rocks. Fossils found
in the oldest rocks are significantly different from those in younger rocks. Intermediate
fossil forms found between the oldest and youngest layers show the transitional path.
Countless examples of such transitions exist, from small changes between similar
species to changes between major groups, like dinosaurs to birds or fish to amphibians.
In this way, we see evolution in action.
Exhibit C: Classification - Like your family tree, organisms can be organized in a 'nested'
pattern in terms of similarity of their shape, appearance, and lifestyles. Evolution
explains this sort of variation among organisms. For example, clams and snails evolved
from a common ancestor, so are grouped together in the Phylum of Mollusks, part of the
Kingdom of Animals. Called biological classification, this grouping now reflects our best
understanding of evolutionary relationships.
Exhibit D: Comparative Anatomy - Organisms that look different and live in different
environments can have very similar structures in their bodies. Comparing the hand
bones in a human to the wing of a bat and the toe bones of a horse, the bone structure
is similar in each mammal. The horse's toe bones are fused, and the bat has elongated
fingers forming the architecture of their wing, but the bones are versions of the same
basic structures that have been modified for each descendant organisms' use. Vestigial
structures, like our tailbone or ear muscles, are leftovers from ancestor species that no
longer have a function. Thus, organisms carry their evolutionary history in their anatomy.
Exhibit E: Recent Evolution - Tiny things with short life spans and quick reproductive
strategies actually bear witness to the evolution process. For instance, we get a flu shot
each year because the flu virus has evolved to resist our antibodies by the next flu
season. Also, hospitals closely watch strains of infections in their patients, because
some strains have become extremely resistant to our antibiotics and can be dangerous if
spread. Fruit fly experiments in high school biology classrooms show the same
phenomena, as did Darwin's observations of breeding, a human-caused example of
natural selection.
Exhibit F: Genetics - Darwin knew that offspring inherit traits from their parents, but
couldn't explain how it happened. Later genetic studies long after Darwin's life could
have showed patterns that refuted evolution. Instead, it supported the other evidences of
evolution wonderfully. When we compare our DNA to that of a fruit fly, we see a 47
percent similarity. Evolution explains that is because we shared some common ancestor
hundreds of millions of years ago. And we share 99 percent of our DNA with that of
chimpanzees, indicating a closer common ancestor only seven million years ago.
This is just some of the evidence supporting the theory of evolution. Everything we've
learned in modern medicine, evolutionary biology, and paleontology has supported that
evolution occurs.
For this year's Ithaca Darwin Days events, visit www.ithacadarwindays.org.
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