HONORS - Evolution Guided Notes
__________________– A scientific theory that states that living species are _______________
____________________ that were ___________________ from present day ones (the genetic changes
in a _____________________________________________________)
___________________ – a well-supported explanation for some aspect of the natural world that
includes ____________________________________________________ (it is not “_______ _ __
_________________________”)
o
Main difference between scientific law and theory is that a law says that something
does occur while a theory attempts to explain why it occurs.
Jean Baptiste Lamarck
Like Darwin, he also believe populations change over time
BUT, his beliefs are no longer supported
Lamarck’s ideas on evolution:
1. Believed in Spontaneous Generation
2. Simple forms of life eventually develop into more complex forms
3. Traits gained in life by ________________________ (use or disuse makes traits better or
worse) could be passed on to offspring
(Ex. Bodybuilder parents make Bodybuilder baby)
About Darwin
Darwin was 22 years old when he sailed from Great Britain on the H.M.S. Beagle.
He spent the voyage collecting thousands of specimens of the fauna and flora, observing various
adaptations of organisms. He was particularly struck by the uniqueness of the fauna of the Galapagos
Islands.
Eventually he released the book “On the origin of Species by Natural Selection”.
(He was not the first or only person to believe that life changes over time, but he was the first
to come up with the correct method by which evolution occurs).
Charles Darwin’s Ideas
(1) Descent with Modification
Basically, the process of evolution
Living species __________________________________________________________________
Species must be able to _______________________________
Ex. Darwin’s Finches
(2) Natural Selection “Survival of the fittest”
The process by which organisms _________________________________________________ survive,
reproduce, and pass their genes to the next generation.
Fitness -(1) __________________________, (2) _____________________________
(3)
_____________________________________________
Occurs in ____________________________________________
◦ Note: It is not essential to survive longer. The longer life simply gives more time to
produce more offspring. Ex. Evolution would favor someone who was 20 and had 4
kids rather than someone who is 80 with 1 kid.
IMPORTANT!!! How does evolution occur through natural selection?
1. Organisms produce more offspring than can survive.
2. ____________________ - Individual organisms in a population have slight variations or
adaptations.
3. Individuals _________________________________, those with ________________________
best suited to the environment are more likely to survive.
4. Survivors pass on _____________________________________________ to their offspring.
5. Gradually, the population’s gene pool changes and the population evolves.
Example of Darwin’s Observation of Natural Selection - Darwin’s Finches
13 different species of finches on the Galapagos Islands
Each species has a beak that is best adapted for a certain kind of food that is found on the different
islands
Another Example of Natural Selection
Beetles living on brown tree bark are either brown or green.
Predator (bird) can more easily see green beetles and will catch them more often than brown.
Brown beetles live longer and produce more offspring, to whom they pass the gene for brown.
Note
Natural selection is an “________________” process, not a ___________________ one
If the environment changes and there is not a suitable phenotype to survive in the new environment
then the species will go _________________________.
There is no amount of “______________________________” that can help you evolve.
Nature simply “selects” the greatest physical traits to survive in different environments and those are
passed on.
Also, what is beneficial in one environment may not be beneficial in another.
3 Types of Natural Selection
1) Directional Selection
o Selection that favors _________________________________________________ (physical type)
o This causes _________________________________________________________ to become
much more common (the look of the population is pushed in
________________________________)
o Ex. Peppered Moths
2) Disruptive Selection
o Selection that favors ___________________________________________ (physical type)
o This causes extreme phenotypes to become _____________________________________
__________________ (the look of the population shows __________________________
_____________________________________)
o
Ex. Darwin’s Finches
3) Stabilizing Selection
o Selection ________________________________ the extreme phenotypes (physical type)
o This causes _____________________________________________________ to become much
more common (the look of the population is ____________________________________)
o Ex. Human weight at birth
Causes of Evolution

1) MUTATIONS!!
Meiosis (and sexual reproduction) gives us variation in a population that creates a _________________
____________ that can be acted upon by natural selection.
Mutations can give rise to completely new characteristics.
MUTATION: ____________________________________________
o Remember that a gene is enough DNA to control 1 trait
On the rare occasion when mutations produce favorable traits, a population’s gene pool (___________
___________________________________________) is changed because of the introduction of this
new, favored trait. The population will then evolve through natural selection to show a greater
percentage of the new, beneficial trait.

Two Types of Mutations:
(1) Changes in genes in _____________________________________: can affect the ________________
________, but cannot be passed to _________________________________________.
(2) Changes in genes in ________________________________________________: do not affect the
______________________________________ itself, can be passed to ___________________________
Mutations may result in a trait that improves an organism’s chances for survival, so that organism would
be more likely to reproduce. Then the favorable mutation would be passed on to offspring.
This results in evolution.
Mutations occur very rarely (and are almost always bad), so populations evolve slowly.
NOTE: EVEN THOUGH EVOLUTION GENERALLY OCCURS SLOWLY…IT SOMETIMES CAN OCCUR
RAPIDLY IF THE NEW MUTATED TRAIT IS STRONGLY FAVORED OVER ALLOTHER PHENOTYPES
PRESENT IN THE POPULATION

2) Genetic Drift – changes in gene pool due to chance (has greater effect on smaller
populations)
Examples



1) _____________________________ – drastic decrease in population size may leave
only certain alleles available. These alleles will quickly be perpetuated.
2) ______________________________ –When a few individuals colonize a new area
(same reasoning as bottleneck)
3) Gene flow
_____________________________________________ of alleles in a population whenever
individuals ____________________________________________.

Note on Causes of Evolution
Notice that all 3 causes for evolution (mutations, genetic drift, and gene flow) all have 1
similarity – they change the GENE POOL of the population.
Evidence for Evolution
1) Molecular Biology
All living things use ______________________________.
The genetic code amongst all living things is ______________________________. (In other words, the
fact that the RNA codon AUG gives the amino acid MET in humans is seen in every other living thing as
well)
This fact more than any other (at least to me) indicates that all living things originated from a common
ancestor.
The closer 2 different species DNA is to one another, then the closer those 2 are ___________________.
Which 2 species are closer related?

Species A: AACTGGCTTA

Species B: AACTAACCCG

Species C: TACTGGCTTA
2) Fossils
The remains or traces of organisms that have once lived on Earth.
Fossil Record: the history of life on Earth, based on fossils that have been discovered
The fossil record shows how organisms have changed over time and shows that the Earth is about
___________________________________________.
Extinctions occur when there are _____________________________________ and species do not have
the _________________________________________________.
The fossil record helps scientists to discover relationships between different groups of organisms and
determine common ancestors.
The Earth is divided into layers called ____________________________
Generally speaking, the lower the strata = _________________________________________ (each new
layer becomes stacked on the older layer below it)
This means if two fossils are found, the fossil found in the lowest layer would be the oldest
There are also techniques for determining the absolute (or relatively exact date) of a fossil’s age
3) Comparative Anatomy
o
Convergent evolution (DID NOT EVOLVE TOGETHER) – process by which ___________________
____________(SAME FUNCTION, DIFFERENT ANCESTOR)
Example: Birds, bats, and moths have wings, but they did not evolve from a recent common ancestor.
Caused by:
◦ ___________________________________________________________________
Analagous Structures (derived from Convergent evolution)
Structures with closely related function but do not come from the same ancestral structure
◦ Same function, different structure
Example: Birds, bats, and moths have wings, but they did not evolve from each other.
o
Divergent evolution (EVOLVED TOGETHER)- build up of differences between groups which can
lead to the development of a new species
In other words, two different species that ____________________________________________
Caused by populations of the same species:
1. moving to _____________________________________________________ or..
2. ___________________________________________________ of the same environment
Homologous structures (derived from divergent evolution)
Structures in different species that originated from common ancestor
May have ____________________________________________________________
4) Vestigial Structures – no longer have a use, but may have had a use in evolutionary history.
Ex: human tail bone (coccyx) made of 4 fused vertebrae that resemble the bones in an animal’s tail.
Other examples: the appendix, and ear muscles!
5) Coevolution
 When two or more species have _____________________, the situation is called coevolution.
Example:
◦ Insects and Flowers
 Flowers provide food for insects. Insects take pollen from one flower to the next
so they can reproduce.
Behavioral Evolution
Behavioral evolution -a behavior that is selected for strongly enough that all organisms in a species
exhibit this behavior because of the _____________________________________________________
________________________________that behaviors gives
Examples:
 The dancing of the blue footed booby may have seemed peculiar to you, but the
execution of this courtship ritual determines whether or not they will reproduce.
 Migration is another example of a behavioral adaptation that would be essential in the
survival and ability to reproduce (if you don’t migrate, you die) of a species.
Sexual Selection
Sexual selection-form of natural selection in which individuals with certain characteristics are more likely
than other individuals to __________________________________(leads to sexual dimorphism –
____________________________________________________)
 Physical Examples:
Feathers of a male peacock
Antlers of a male deer
Humans

Behavioral Examples:
Darwin Beetles
Blue footed Booby
Humans