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Evolution & Natural Selection Notes
REVIEW
List the six characteristics all living things have in common:
1. ______________________________
4. ______________________________
2. ______________________________
5. ______________________________
3. ______________________________
6. ______________________________
NEW STUFF
Fill in the missing information by using the page numbers listed in the light green Cells and Heredity
textbook.
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Define the following terms:
o Evolution (pg 199) - _______________________________________________________
o Natural selection (pg 201) - _________________________________________________
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Natural selection is sometimes referred to as “survival of the fittest”
Who was responsible for creating the Theory of Evolution by Natural Selection (pg 138)?
___________________________________________________________________________
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What is an adaptation (pg 198)? ________________________________________________
________________________________________________
o Give an example of an adaptation that helps an organism with the following (pg 141):
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Obtaining food: ________________________________________________
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Avoiding being eaten: ___________________________________________
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Reproducing: __________________________________________________
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There are 4 major parts to the idea of how natural selection works (pgs 143 – 144).
o __________________ - more organisms are born than can survive
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Resources that there are not enough of for all the organisms in an area are
called limiting factors.
o __________________ - individual members of a species have slightly different traits
o __________________ - organisms fight to get the limited resources
o __________________ - the organisms with the best traits to get the resources in their
environment live longer and reproduce more

Darwin was not able to explain where the variations came from or what caused them. Where
do we now know they come from (pg 145)? ________________________________________

How does natural selection say that new species form (pg 152)? _______________________
___________________________________________________________________________
___________________________________________________________________________
o The process of a new species forming from an old species is called speciation.
o Branching trees are diagrams that show how scientists think ____________________
______________________________________________________________. (pg 152)
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Branching trees are also called phylogenies, phylogenic trees, or cladograms.
Darwin’s Theory of Evolution by Natural Selection can be summed up like this
o
There’s not enough stuff for everything to live
o
Organisms fight to get the stuff they need
o
The bigger, stronger, smarter, faster organisms get the stuff they need
o
The organisms that get the stuff they need live longer and make more babies
o
Those babies inherit (passed down genetically) those good traits from their parents
o Since the good traits get passed on and the bad traits get weeded out, living things change over time
(evolve)

Since Evolution by Natural Selection is a theory, there is a lot of evidence to support it.
o What is a fossil (pg 199)? ________________________________________________

How do fossils support evolution (pg 149)? _____________________________
________________________________________________________________
o How do similarities in early development support evolution (pg 149)? ______________
______________________________________________________________________
o What is a homologous structure (pg 200)? _________________________________
______________________________________________________________________

How do homologous structures support evolution (pg 150)? ________________
________________________________________________________________
o A body part that no longer serves a purpose in an organism is called a vestigial organ.
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Vestigial organs support evolution because they served a purpose in the
common ancestor, but the needs of the organism have changed over time.
o How do similarities in DNA and protein structure support evolution (pg 151)? ________
______________________________________________________________________

Since Evolution by Natural Selection is a theory, some questions still remain unanswered.
o What is the fossil record (pg 199)? ________________________________________
o What is gradualism (pg 200)? _____________________________________________

What should the fossil record show if gradualism is correct (pg 163)? _________
________________________________________________________________

What does the fossil record actually show (pg 163)? ______________________
________________________________________________________________
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Fossils that show a combination of traits of an older species and a newer species
on the same organism are called transitional fossils.

Transitional fossils show speciation and evolution happening.
o What is punctuated equilibria (pg 202)? ____________________________________
______________________________________________________________________
o What is a mass extinction (pg 162)? _______________________________________
______________________________________________________________________

There is another theory called the Cell Theory that also raises questions about the Theory of
Evolution by Natural Selection.
o List the 3 statements that make up the Cell Theory (pg 10).
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________________________________________________________________
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________________________________________________________________
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Since the Cell Theory says all cells come from other cells, and the idea of speciation says that new
species evolve from old species, this leaves us with another unanswered question…
Where did the first cell in the first species come from?
(we’ll attempt to answer this later)
Symbols and Events on Evolution Diagrams
(branching trees, phylogenies, phylogenic trees, cladograms)
Understanding a phylogeny is a lot like reading a family tree. The root of the tree represents the
ancestral (older) lineage, and the tips of the branches represent the descendants (newer) of that
ancestor. As you move from the root to the tips, you are moving forward in time (closer to present
day).
When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation
event occurs, a single ancestral lineage gives rise to two or more daughter lineages.
Phylogenies trace patterns of shared ancestry between lineages. Each lineage has a part of its
history that is unique to it alone and parts that are shared with other lineages.
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared
with other lineages (common ancestors). Common ancestors are organisms that existed in the past
that two or more modern organisms can trace their evolutionary history back to.