Transcript Evolution Evidence

QUESTIONS:



1) How do changes in DNA affect the organism
they occur in?
2) What are the major mechanisms that drive
evolution?
3) What is speciation and how does it occur?
EVIDENCE OF EVOLUTION
“They’ll laugh as they watch us fall,
The lucky don’t care at all,
No chance for fate,
It’s unnatural selection,
I want the truth”
Muse, Unnatural Selection
GENETIC EVIDENCE



Organisms which are more closely related share
more of the same genes
Therefore, it is most likely that these organisms
arose from a common ancestor possessing those
genes, and thus acquired them from a common
source
It is unlikely that these genes would have arisen
independently in various organisms
MOLECULAR EVIDENCE



Similarly, structural elements that make up
related organisms are conserved, as from a
common ancestor
The structure of proteins within the cell will tend
to remain the same, unless a mutation produces
a more favourable variant
This means that organisms are related not only
on a physical level, but on a molecular level.
MATHEMATICAL INTERLUDE

Take a small protein, 50 amino acids long

Each amino acid is coded by 3 nitrogenous bases



Each base needs to be a specific one in order to
generate the proper amino acid (mostly, there is
some flexibility), and has a ¼ probability of being
that amino acid
Thus, there are 4^(3x50) possible combinations =
2.0 x 1090
4.9 x 10-91% chance of occurring at random


That is a
0.000000000000000000000000000000000000000
00000000000000000000000000000000000000000
000000000049% chance
Repeat this for every protein that is conserved,
many of which are MUCH larger than 50 amino
acids long
ANATOMICAL EVIDENCE



There are many physical structures which have
clear descent from a common ancestor
These are called homologous structures, and tend
to be common in organisms which are related
If the similarity is not apparent in the adult
versions of an organism, then it may be necessary
to observe the embryonic structure
FOSSIL EVIDENCE
You can trace an organisms evolution by following its
progress through the fossil record
 Fossils will occur in sequences of increasing
complexity and diversity, indicating that organisms
were evolving to become more adapted to their
surroundings
 Key fossils especially include those known as
“missing links”, which provide bridges between
ancient ancestors and more modern creatures
