Evolution
Write down what you think evolution
is
Charles Darwin (1809–1882)
Voyage of the HMS Beagle 1831–
1836 (Captain Fitzroy)
Galapagos Islands (near Ecuador;
volcanic archipelago [very isolated])
— looked at tortoises, finches, + other
organisms
observed wide variations in natural
populations, particularly in tropical
islands
Evolution summarized
Thebasic theory of evolution is
surprisingly simple. It has three
essential parts:
1. It is possible for the
DNA of an organism to
occasionally change,
or mutate.
A mutation changes the
DNA of an organism in a
way that affects its
offspring, either
immediately or several
generations down the
line.
Note: mutations are
random
2. The change
brought about by a
mutation is either
beneficial, harmful or
neutral.
If the change is harmful,
then it is unlikely that
the offspring will survive
to reproduce, so the
mutation dies out and
goes nowhere.
Ifthe change is
beneficial, then it is likely
that the offspring will do
better than other offspring
and so will reproduce
more.
Through reproduction, the
beneficial mutation
spreads. The process of
culling bad mutations and
spreading good mutations
is called natural
selection.
Darwin’s Ideas
Related organisms descended from
common ancestors
More individuals produced than can
possibly survive
Physical traits of individuals of a species
vary and these variations are inherited
Some variants better adapted than
others in a particular environment
Better-adapted individuals more
likely to survive and reproduce
Over time, natural selection can
produce gradual changes in existing
species and create new species
from pre-existing ones
Evolutionary Concepts
―Evolutionis survival of the fittest‖
Fitness: Who has greater fitness?
Incredible Hulk Rush Limbaugh
Evolutionary Concepts
Fitness: The ability of an organism to
propagate his/her genetic material in
the gene pool through mating
(whoever has the most kids is the
‗most fit‘)
So….. Rush with 2 children has
greater fitness that the Hulk, who has
no children.
Common Evolution Misconceptions
1.
"Evolution has never been
observed.”
Wrong
Peppered Moths
Prior to 1800 in
England, most
moths of a
certain species
had a light
pattern.
Dark colored or
melanic moths
were rare and
were therefore
collectors' items.
During the Industrial Revolution, soot and
other industrial wastes darkened tree
trunks and killed off lichens.
The light-colored moth became rare and
the dark morph became abundant.
In 1819, the first melanic morph was seen;
by 1886, it was far more common
Eventually light morphs were common in
only a few locales, far from industrial
areas.
Light Moths Dark Moths
Recaptured Recaptured
Polluted 13% 28%
Woods
Non-Polluted 15% 5%
Woods
Why?
Light moths
blend in with
tree bark in non-
polluted areas
and dark moths
blend in with
bark in polluted
regions
Moths that blend
in are less likely
to be eaten by
birds.
Conclusion
Dark moths have a survival
advantage over light moths in polluted
areas, and light moths have the
advantage in non-polluted areas.
Moths in the ‗wrong‘ area have a
decreased chance of passing on their
genes (having more offspring)
Interestingly
since the 1950's as soot
producing chimneys started to
disappear the white version of the
moth has started to reappear.
Antibiotic Resistance
Mostof the time antibiotics work
perfectly.
=
+
Add Bacteria
Petri Dish and Antibiotics Killed
Salmonella
BUT
Everyonce in a while a single bacteria
has a mutation that allows it to survive
Chance mutation
=
+
Add
Petri Dish and Antibiotics
Salmonella
That single bacteria can then reproduce
and re-populate the colony because there
is no competition for resources
The next time that same antibiotic is
used it is completely ineffective as the
whole colony is ‗resistant‘ to the
antibiotic
Through this mechanism many
bacteria harmful to humans are
becoming resistant to multiple
antibiotics huge problem.
Common Evolution Misconceptions
-there are numerous examples of insects
becoming resistant to pesticides.
eg. Mosquitoes in Africa took 1 year to
become resistant to DDT after spraying in the
1950‘s
-this all started with 1 mutation that
increased one mosquito's fitness. The mutant
mosquito was able to spread his genes until,
after multiple generations the entire population
had the beneficial mutation. The mutation was
―selected for‖
Common Evolution Misconceptions
2. ―Man evolved from the apes‖
Common Evolution Misconceptions
Everything on the
earth is just as
―evolved‖ as
everything else as
we all originated
from a common
ancestor.
Through a process
called ―speciation‖
(see later note)
Apes are just as
―evolved‖ as man
Common Evolution Misconceptions
―Man is gradually evolving to be
3.
smarter‖
Talosians… from the original Star Trek Pilot “The Cage”
Common Evolution Misconceptions
Lifedoes not evolve towards ―perfection‖,
or any predetermined form
Populations evolve when certain traits are
selected for due to environmental
pressures
The future form of an organism is
impossible to predict, as we cannot know
what environmental constraints it will run
up against in the future.