Download Molecular Record - Ms. Herzan`s Biology

Evidence of Change: Molecular Record
As the molecular biologist in your group, your job is to present the evidence of the molecular
biology and how it supports evolution. You have been provided with some readings and diagrams
that will help your case, along with some guiding questions that will help the other scientists
understand your field.
Start by looking through the diagrams and articles, then answer the questions that highlight the
important points of molecular biology and how it provides evidence for evolution. Be sure that you
are able to explain these main points to your group members.
1. What is the molecular record?
The molecular record is the record of molecular data that is used to compare DNA and
protein structures between species.
2. How does the molecular record support evolution?
The molecular record is comparing the changes in DNA over time. Since DNA is where
variation first appears, the molecular record is catching every bit of variation that occurs in a
population. It is recording each change over time that is occurring and keeping a record of
these changes.
3. What will the molecular record reveal about two species that have recently diverged from
one another?
Species that have recently diverged are considered to be closely related and the DNA
sequences are more similar in species that are closely related.
4. Why will the molecular record show many differences between species which diverged from
their common ancestor a very long time ago?
More time has passed for mutations in the DNA to have formed. Since molecular biologists
compare the DNA sequences between species, they will find more variation in the DNA
sequences in species which have diverged from their common ancestor a very long time ago.
5. How does molecular evidence prove that modern birds and dinosaurs lived together?
Molecular studies suggest that the genetic divergences between many lineages of birds
occurred during the Cretaceous period, when dinosaurs still existed.
6. How is molecular evidence used to determine how long since two species last had a
common ancestor?
A molecular clock is used to determine the evolutionary relationship among organisms, and
it indicates the time in the past when species started to diverge from one another.
Genes evolve at different rates because some proteins are more tolerant of changes in their
amino acid sequences than others. The average rate at which a particular kind of gene or
protein evolves gives rise to the concept of a molecular clock. Molecular clocks run rapidly
form less constrained proteins and slowly for more constrained proteins, though they all
time the same evolutionary events.
7. What does the molecular record say about the relationship between humans and other
primates?
The total gene difference between humans and chimpanzees is about 6%. Since this is a
relatively small number, we can assume that humans and chimpanzees are closely related.