CH. 15
EVOLUTION
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Ch. 15.1 – DARWIN’S THEORY OF EVOLUTION BY
NATURAL SELECTION
 MAIN
IDEA – Charles Darwin developed a
theory of evolution based on natural
selection.
 QUESTION:
What do you think you can look
at to see how species change over time?
 Where did Charles Darwin do most of his
studies in regard to figuring out evolution?
Developing the Theory of Evolution
 In 1831 when Charles ______________ began his
voyage most people believed that the world was
_______ yrs. old & animal & plants did _____ change.
 During Charles Darwin voyage on the HMS ________,
which lasted 5 years, he collected biological (plants &
animals) and geological specimens (fossils).
 Darwin read a book by Charles Lyell, which proposed
that the Earth was __________________ of years old.
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This book influenced Darwin’s thinking as he observed
fossils of marine life at __________ elevations, giant fossils
looking similar to smaller living mammals, and saw how
earthquakes could lift rocks great distances very quickly.
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Darwin in the Galapagos Islands
______________________________________ are located
off the west coast of S. America.
Darwin studied the mockingbirds, _________________ &
__________________ from the _______________ islands
 Discovered that he could recognize what island the
tortoises came from by their ____________________.
 After returning to England Darwin discovered that the
finches of the Galapagos were found ____ where else,
but they closely resembled the species from mainland
S. America.
Should ____________ have resembled each other
because of _____________________ environments.
Began to suspect the populations changed _______
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Tortoises and Finches of the Galapagos Islands
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DARWIN CONTINUED HIS STUDIES
Darwin hypothesized that ________ species could appear
gradually through small changes in ancestral species.
Darwin looked to breeders of pigeons to help understand
these changes.
 __________________________ or selective breeding is
the process of directed breeding to produce offspring
with the _____________________________________.
 Learned that breeders do select and breed the
pigeons for the __________ exaggerated certain traits.
EX: larger tails
 Concluded that if humans can do artificial selection
then the same process could work in nature. Given
enough _____________ could produce a new species.
 NATURAL
SELECTION
 Natural selection says that some
_____________________ in the struggle for
existence would be _____________________
equipped for survival than others. The
competitors ___________ equipped ______.
Thomas ___________ influenced Darwin’s
thinking on natural selection. Malthus’
essay suggested that the human
population if left unchecked would
outgrow its food supply, leading to a
_________________ struggle for existence.
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Natural Selection – Cont.
Darwin’s theory of evolution by natural selection has 4
principles:
 1. Individuals in a population show differences or
________________________________________.
 2. Variations can be __________________________.
 3. Organisms have _____________ offspring than can
_________________________ on available resources.
 4. Variations that ___________________ reproductive
success will have a ____________________ chance of
being passed on than those that do not increase
reproductive success.
Given enough time, natural selection could ___________
a population enough to produce a ____________ species.
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The Origin of Species
About 1840 Darwin formulated his theory of evolution
and he began writing his book that explained natural
selection.
Darwin compiled evidence to support his theory of
evolution for years.
In 1858 Alfred _________________________ proposed a
theory almost identical to Darwin’s theory.
Both men presented their ideas on evolution and a year
later Darwin published his book, “On the _____________
____________________ by Means of Natural Selection.”
Evolution is defined as the cumulative _______________
in groups of organisms through ____________________.
 _________________________________________ is the
mechanism by which evolution occurs.
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QUICK QUIZ
1. Darwin referred to the process of promoting certain traits by breeding
members with those traits as___________.
A. Natural selection
B. Artificial selection
C. Evolution
D. Ancestral breeding
2. What theory accounts for why populations can be modified over time?
A. Natural selection
B. Artificial selection
C. Ancestral modification
D. Fossil theory
3.
A.
B.
C.
D.
Which statement is true regarding evolution?
It describes changes over many generations.
It is the same as natural selection.
It only involves artificial selection.
It occurs within a single generation.
4.
A.
B.
C.
D.
What are 2 main components of natural selection?
Vestigial structures and camouflage
Artificial Selection and selective breeding
Variation and inheritance
Mimicry and artificial selection
 Section
15.2 – EVIDENCE OF
EVOLUTION
 MAIN IDEA – Multiple lines of evidence
support the theory of evolution.
 QUESTION:
What evidence supports the
theory of evolution by natural selection?
 What are the 4 principles of natural
selection?
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SUPPORT FOR EVOLUTION
A ___________________ provides an explanation for a natural
phenomenon based on ________________. Theories explains
available data and suggest further areas for experimentation.
Theory of evolution states that all organisms on Earth have
____________________ from a _________________ ancestor.
The _______________________________ provides a record of
species that lived long ago and supply some of the most significant
______________________ of evolutionary change.
 Shows how ancient species are _____________________ to
current species.
 Shows that __________________ species have remained
__________________________ for _________________ of years.
 Fossil record is an important source of information for
determining the ________________________ of organisms and
patterns of ______________________________________.
 The fossil record has intermediate species
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EXAMPLE OF FOSSIL RECORD
SUPPORT FOR EVOLUTION – CONT.
 Two major classes of traits when looking at
transitional fossils are:
 _____________________ traits – newly evolved
features, like feathers, which do ____________
appear in the fossils of common ancestors
 _________________ traits – are more primitive
features, like teeth and tails, which _________
appear in the ancestral form.
 ____________________ fossils provide detailed
patterns of evolutionary ___________________
for the ancestors of many __________________
animals, like horses, whales and humans.
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COMPARATIVE ANATOMY
 _____________________________________ are
anatomically ______________ structures that are
_______________ from a ____________ ancestor.
 Evolution predicts that an organism’s body
parts are more likely to be _________________
of ancestral body parts than to be entirely
_____________ features.
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VESTIGIAL STRUCTURES
 _________________ structures are structures that
are ______________________ forms of functional
structure in other organisms.
 Evolutional theory predicts that features of
ancestors that __________ longer have a function
for that species will become __________________
over time until they are _________________.
 Ex: snake pelvis – pelvis but no legs attached
 Ex: human appendix – important for digestion
in many mammals but only limited use in
humans and apes
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ANALOGOUS STRUCTURES
 ________________ structures can be used for the
_____________ purpose and can be superficially
_______________ in construction but are ______
inherited from a common ancestor.
 Ex: wings of an eagle and wings of a beetle
have same function, but are constructed in
different ways and from different materials
 Analogous structures do ________ indicate
______________ evolutionary relationships, they
do show that functionally similar features can
evolve ____________________________ in
_____________________________ environments.
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COMPARATIVE EMBRYOLOGY
 _______________________ embryos provide more
glimpses into evolutionary relationships.
 ____________________ is an early prebirth stage
of an organism’s development.
 Vertebrate embryos exhibit __________________
______________________________ during certain
phases of development but become ___________
__________________ structures in the adult form.
 Demonstrates that the embryos of vertebrates
evolved from a ___________________ ancestor.
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COMPARATIVE EMBRYOLOGY
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ADAPTATION
_____________________ is a trait shaped by natural
selection that ______________________________ an
organism’s ___________________________ success.
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Ex: either physical or behavioral
______________________ is a measure of the relative
contribution that an individual ______________________
makes to the _________________________ generation.
 Measured as the number of reproductively viable
_______________________________ that an organism
produces in the next generation.
 Better an organism is adapted to its environment, the
______________________ its chances of ___________
and ________________________________ success.
 EX: environments _________________ on the different
________________________________ so the different
beak characteristics were selected for.
___________________________ is the ability of an
organism to _____________________ in with their
________________________________________.
 Allows organisms to become almost
____________________ to _________________.
____________ survival & ability to reproduce
 ____________________ is where one species has
evolved to __________________ another species.
 Mimicry increases _______________ because it
helps ______________ them against predators.
Ex: a harmless organism mimics a harmful
organism so predators leave them alone.
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QUICK QUIZ – SECTION 15.2
1. Recently evolved traits that do not appear in ancestral fossils
are called ________.
A. Homologous traits
B. Ancestral traits
C. Primitive traits
D. Derived traits
2. A morphological adaptation in which one species resembles
another is called _____.
A. Mimicry
B. Camouflage
C. Vestigial adaptation D. Fitness
QUICK QUIZ CONTINUED
3. Which of these is an example of analogous structures?
A. Hawk wings and fish fins
B. Hawk and insect wings
C. Horse legs and insect wings
D. Horse legs and elephant trunks.
 Section
15.3 – SHAPING
EVOLUTIONARY THEORY
 MAIN IDEA – The theory of evolution
continues to be refined as scientists
learn new information.
 QUESTION:
How would an albino of a
species that is normally green and lives
among leaves be less fit?
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Mechanisms of Evolution
Scientists Hardy & Weinberg showed mathematically that
evolution will ______________ occur in a population unless allelic
frequencies are acted upon by _____________________ that cause
_____________________________.
___________________________________________ is when allelic
frequencies remain _________________________ in a population.
For a population to stay in genetic equilibrium 5 conditions must
be meet:
 1. there must be ___________________________ genetic drift
 2. no _______________________________________________
 3. no _______________________________________________
 4. mating must be ____________________________________
 5. there must be _______________________ natural selection.
Hardly any population in nature will meet these requirements for a
long time so populations are ____________ in genetic equilibrium.
 _____________________________________
is any change in the allelic frequency in a
population that results from _____________.
In _________________ populations allelic
frequency remains relatively ___________
from one generation to the next.
In _____________ populations the effects
of genetic drift becomes more pronounced
and the chance of losing an allele
becomes __________________________.
___________________________ can occur when a
______________________ sample of a population
settles in a location ________________________
from the rest of the population.
 EX: Amish or Mennonite populations in the US
 ___________________ occurs when a population
___________________ to a very __________ number
and then __________________________________.
 ____________________ of the rebound population
often is genetically ___________________ to the
population at its ____________________________
level and has reduced diversity.
 ______________________ has random movement of
individuals between populations, migration, which
increases genetic variation within a population and
reduces differences between populations.
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Nonrandom mating – _______________________ is
mating completely random in a population, usually
will mate with an individual in __________ proximity.
 EX: Promotes __________________________
 _______________________________ is a random
change in genetic material.
 Mutations may cause a ______________________
in allele frequency, which violates genetic
equilibrium.
 Mutations can be harmful, helpful, or no affect
 When a mutation gives an organism an
_____________________________, the mutation
will be selected _______________ and become
___________ common in subsequent generations.
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 Natural
selection acts on an organism’s
_____________________________ and
changes allele frequencies.
 3 ways that natural selection alters
phenotypes:
_______________________ selection
________________________ selection
________________________ selection
 Stabilizing
selection
Stabilizing selection is the ____________
common form of natural selection
Will _____________________________
extreme expressions of a trait when the
average expression leads to __________
__________________________.
Ex: babies born of average weight
have best chance of survival
 Directional
selection
 Directional selection occurs when the
_______________________ version of a
trait is _______________ fit for survival.
EX: Galapagos Island finch beak size.
 Disruptive
Selection
 Disruptive selection is a process that
______________ a population into ____
groups. It will ____________________
individuals with the ________________
traits and retain individuals that express
the extreme traits at _______________
ends of a bell curve.
 Sexual
Selection
 Sexual Selection is another type of natural
selection based on the frequency of a trait
that enables an organism to _____________
a ______________.
Occurs in populations where male and
female organism ____________________
in appearances.
Usually males are ___________________
than females and more _______________.
EX: peacock – males have the brightly
colored tails.
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Reproductive Isolation
2 types of ______________________________________:
 Prezygotic isolating mechanism
Operate ___________________ fertilization occurs
which prevents ________________________ from
entering the population’s _____________________
Ex: birds mating songs or dances are different or
the time when mating occurs is different
 Postzygotic isolating mechanisms
The _________________ offspring are ___________
Ex: tiger & lion produce liger, which is sterile
______________________________ is the process
where members of a sexually reproducing
population change so much that they can ______
longer produce ___________ offspring with
members of the original population.
 2 types of speciation:
 Allopatric speciation (geographic isolation)–
where a physical ______________ divides one
population into 2 or more populations.
Eventually after enough time has passed the
populations will _______ longer be able to
____________________ successfully with one
another
Most common form of speciation.
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 Sympatric
speciation – where a species evolves into a
_______ species ________________ a physical barrier.
Ex: polyploidy plants
 Temporal
Isolation – Members of that species
will ______ mate together because the
_________ that they mate has ______________.
Ex: Used to mate in the morning, now mates
in evening
 Behavioral Isolation – Members of that species
will no longer mate together because the
_____________________________ has changed
EX: Birds song has changed
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Patterns of Evolution
_____________________________, also called divergent
evolution, can occur in a relatively ______________ time
when one species gives rise to many species in response
to the creation of a _______________________________
or another ecological opportunity.
 Adaptive radiation often follows large scale
________________________________________.
Ex: mammals increased drastically after the
extinction of dinosaurs.
_____________________ occurs where 2 species living in
close relationship with another species affects the
evolution of ________________ species. Another form of
coevolution is where one species can evolve a parasitic
dependency on another species.
 EX: Mutualism
 Convergent
Evolution
 _______________________________ occurs
when ___________________ species evolve
_________________ traits even though they live
in ________________ parts of the world but with
similar ecology and ____________.
 ______________________ is a theory which
states that evolution proceeds in ________,
gradual steps.
 _____________________ equilibrium is a theory
which states that _______________ transitions
in the _____________ record occurs due to rapid
spurts of genetic change causing species to
diverge _____________________.
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CONVERGENT EVOLUTION
QUICK QUIZ:
 1. What occurs when average traits benefit a
population rather than extreme traits?
 A. Unnatural selection B. Directional selection
 C. Disruptive selection D. Stabilizing selection
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2. What has occurred when fertilization produces
a hybrid offspring that cannot develop or
reproduce?
 A. prezygotic isolation
B. Postzygotic isolation
 C. Non-reproductive isolation
 D. Speciation
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