Download Evidence processes

EVIDENCE OF EVOLUTIONARY PROCESS
In determining who is more closely related to whom, or if 2 species are closely related, many scientific
practices are used. Below are the largest areas (disciplines) providing scientific evolutionary evidence. The
evidence tells the pattern of evolution and rate of separation of the species being studied!
1. Embryology- studying the development of organisms before they are born.
EX: all vertebrates have gill slits and a tail at one time in their embryo development.
2.
Paleontology- studies fossils to determine information of extinct species and the formation of new
species, as well as a look at what our world was like as it was forming.
EX: Fossil deposits of oyster shells in the Grand Canyon walls, indicate evidence about what our climate
used to be like as well as gives evidence of what prehistoric marine creatures were like.
3.
Molecular Biology- studies the similarities and differences in organisms at the biochemical level.
The closer related 2 species are, the lower the percent difference in any given biochemical.
EX: Comparing things like; DNA sequences, number, order and types of amino acids made, hemoglobin
(molecule that carries O2 and CO2) and cytochrome c, (proteins made that assist organism in breaking
down foods for energy) reveals what species are closer than others. (Based on how different or similar
these items are.)
4.
Comparative anatomy- studying homologous, analogous and vestigial structures in different
species reveals common ancestry.
EX: Homologous structures are those that have the same anatomy (tissues, bones, ligaments, tendons, etc)
even though the actual structure may serve a different function in each species. (Whale flipper and human
hand)
Analogous structures are those that have the same function for each species, but do not share common
ancestry. (Bird and bee wings)
Vestigial structures are those that have a huge function in one species and a limited (if any) function in
another species. (Tail bone in humans)
Science uses combinations of the above in order to paint a clearer picture of organismal relationships. Now
that we have introduced this concept, perform the following:
a) What parts of extinct organisms are well preserved in the fossil record? What parts are not?
b) What does inference have to do with fossils? (You may look it up in the dictionary on the front
counter, use the entry that deals with logic.)
c) If you were using comparative anatomy to look at relatedness of 2 species, which of the 3
comparative anatomy structures would you think would provide the most evidence for being
closely related? Why?
d) What evolutionary pattern would account for analogous structures?
e) Between species A and C the hemoglobin molecule shows a difference of 67%. Between species
A and B, there is a 12% difference. Which 2 species are more closely related? Why? What type of
science evidence is this?
f) Why do you have a tail bone, since there is no immediate function?
g) Name another vestigial structure in humans. (Think about it! Come up with one more!)
h) Why are bee wings and bat wings not an indication of relatedness? (Explain this) They are both
used for flight!!
i) Complete the additional coloring sheet to practice identifying homologous structres.