Name:_________________________________ Date:_________________ Pd:________
Evolution and Natural Selection Notes
1) What is Evolution?
 Evolution  the process by which __________________________________ change
over many generations through ________________________________________.
•
No __________________________ organism can evolve, but given the right
conditions over enough time, _______________ within a population will gradually
change until the _____________________________________ is different.
•
Populations tend to evolve due to external environmental factors such as
predators, food sources, and changes in climate.
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New species arise through this very process, and all life on earth can be traced
back to simpler common ancestors.
2) Natural Selection
• The driving mechanism behind evolution.
•
Certain organisms survive to pass on their traits to successive generations, but
most do not.
•
Often summed up as “_______________________________________________________”
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Thomas Malthus
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No population can grow indefinitely. Many more offspring are born than
will actually survive to pass on their genes. Therefore, individuals must
____________________________________________________ to survive.
•
Darwin recognized that limited resources in any environment lead to a
struggle for existence, in which traits of some individuals will give them an
advantage over others. However slight this advantage, it will lead to
certain traits being “_________________________________” by nature to
survive and reproduce… NATURAL SELECTION!
•
Where did all the millions of species come from?
•
•
Name:_________________________________ Date:_________________ Pd:________
•
The Principles of Natural Selection
• ________________________________
• Parents produce _____________ offspring than will survive. Similarly,
plants produce thousands of seeds even though only a few may
germinate.
• _____________________________________________
• There are genetic differences in any population which result in
many combinations of different traits among offspring. These traits
are __________________________________________ from parents to
offspring.
• _________________________________
• In any population, organisms must compete for resources to
survive. Some individuals have _________________ which allow them
to survive better than others; often referred to as “survival of the
fittest”.
• ___________________________________
• Those who have a survival advantage are more likely to
__________________________ and pass on their favorable genes and
traits to successive generations, resulting in new
________________________ and eventually new ___________________.
•
Explain the Peppered Moth Study and why there were periods of light colored
moths, and periods of dark colored moths. How do the 4 principles of natural
selection apply to this example?
3) Evidence for Evolution
• Geographic Distribution  Related native species are found only where they
could have migrated on their own.
• The Wallace Line
•
Even though the climates were almost identical, the flora and
fauna were drastically different on either side of the line because
_________________________________________________________________
_____________________________, just as the species on Madagascar
Name:_________________________________ Date:_________________ Pd:________
had been isolated from the mainland of Africa.
•
Homologous Anatomy  Traits that are _____________________ between species
because they originate with a
__________________________________________ who had the
same trait.
•
The example to the right compares the internal
structure of a human arm with the forelimb of a
whale.
•
Although the shape of each bone is different, each
bone in the human arm has a corresponding
match in the whale.
•
Analogous Structures lead to convergent evolution.
• When two species evolve a similar adaptation not because of
common ancestry but because they have become adapted to a
_____________________________________, or use the trait for a similar
__________________________.
•
Birds and bats have both evolved wings because they both use
them to fly. Rather than “homology”, this is called an “analogous
trait” or simply, an analogy.
•
Both homologous and analogous traits are excellent evidence for
evolution, because they show how ___________________________________
are related and how they evolved their adaptations for survival.
•
Vestigial Structures  Physical remnants of organs that once helped a species’
ancestors survive, but are no longer useful.
• Vestigial structures tend to be very ______________, because they are not
needed for ______________________. Hence, they are only “vestiges” of
what they once were.
•
If a species has an anatomical structure that appears to be out of place,
many times it is vestigial.
Name:_________________________________ Date:_________________ Pd:________
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Example: The human appendix is a good example of a “vestige” of
an earlier digestive organ that helped our ancestors process plant
material
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The Fossil Record  A physical history of the life on Earth in the form of fossils
buried within chronologically oriented layers of sedimentary rock.
•
Shows ______________________________________, including transitional
species
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Embryology Very close similarities in early developmental stages of related
species
• All vertebrates start out almost the same because they all share a
_____________________________________________________ which was much
more primitive.
•
All vertebrates embryos start out with a tail and tiny neck slits resembling
gills. This includes humans!
•
In land-dwelling groups such as mammals and reptiles, these slits
disappear as the embryo develops, eventually becoming parts of
the throat and mouth.
•
In humans, the tail is absorbed into the growing body and remains
as the tailbone.
•
DNA and Genetics  Genetic code shared by all living things on Earth
•
Allows us to look at different species at the ____________________________
level and compare their genes and chromosomes.