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Standard 8—Evolution
Speciation
Standard 8 Vocabulary
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Diversity
Speciation
Gradualism
Punctuated Equilibrium
Adaptive Radiation
Divergent Evolution
Polyploidy
Geological Time Scale
Extinction
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Convergent Evolution
Bottleneck Effect
Founder Effect
Geographical Isolation
Reproductive Isolation
Macroevolution
Microevolution
Fossil
8. Evolution is the result of
genetic changes that occur in
constantly changing
environments.
8a. Know how natural selection
determines the differential
survival of groups of organisms.
8b. Know a great diversity of
species increases the chance
that at least some organisms
survive major changes in the
environment.
Publication of On the Origin of
Species
• Publication of On the Origin of Species
• Darwin filled notebooks with his ideas about
species diversity and the evolution process.
• Darwin was stunned and disturbed by his
discoveries.
• He shelved his manuscript for years and told his
wife to publish it in case he died.
Publication of On the Origin of
Species
• In 1858, Darwin received a short essay
from naturalist ___________ _________.
• The essay summarized Darwin’s thoughts
on evolutionary change.
• Later that year, Wallace’s essay was
presented with some of Darwin’s work.
• In 1859, Darwin published his book, On
the Origin of Species.
Publication of On the Origin of
Species
• In his book, Darwin:
• proposed a mechanism for evolution called natural
selection.
• presented evidence that evolution has been taking
place for millions of years—and continues in all
living things.
Inherited Variation and Artificial
Selection
• Inherited Variation and Artificial Selection
• Members of each species vary from one another
in important ways.
• In Darwin’s day, variations were thought to be
unimportant, minor defects.
• Darwin argued that this _____________
mattered.
Inherited Variation and Artificial
Selection
• Darwin noted that plant and animal
breeders would breed only the largest
hogs, the fastest horses, or the cows that
produced the most milk.
• Darwin termed this process
______________ selection.
Inherited Variation and Artificial
Selection
– How is natural variation used in artificial
selection?
– Artificial selection is the selection by
_____________ for breeding of useful traits
from the natural variation among different
organisms.
Inherited Variation and Artificial Selection
Cauliflower
Brussels
Sprouts
Broccoli
Kohlrabi
Ancestral
Species
Kale
Evolution by Natural Selection
• Evolution by Natural Selection
• Darwin compared processes in nature to artificial
selection.
• By doing so, he developed a scientific hypothesis
to explain how evolution occurs.
Evolution by Natural Selection
• The Struggle for Existence
• Darwin realized that high birth rates and a shortage of life's
basic needs would force organisms to compete for
resources.
• The ___________ ________ ___________
means that members of each species compete
regularly to obtain food, living space, and other
necessities of life.
• The struggle for existence was central to
Darwin's theory of _______________.
Evolution by Natural Selection
– How is natural selection related to a species' fitness?
– Survival of the Fittest
• The ability of an individual to survive and reproduce in its
specific environment is _____________.
• Darwin proposed that fitness is the result of adaptations.
• An ________________ is any inherited characteristic that
increases an organism's chance of survival.
Evolution by Natural Selection
• Successful adaptations enable organisms to
become better suited to their environment and
better able to survive and reproduce.
• Individuals with characteristics that are not well
suited to their environment either die or leave
few offspring.
• Individuals that are better suited to their
environment survive and reproduce most
successfully.
• Darwin called this process _____________ of
the _______________.
Evolution by Natural Selection
• Because of its similarities to artificial selection,
Darwin referred to the survival of the fittest as
_________ __________.
• In natural selection, the traits being selected
contribute to an organism's fitness in its
environment.
– Over time, natural selection results in changes in
the inherited characteristics of a population. These
changes increase a species' fitness in its
environment.
Summary of Darwin's Theory
• Summary of Darwin's Theory
• Individual organisms differ, and some of this
______________ is heritable.
• Organisms produce more offspring than can
survive, and many that do survive do not
reproduce.
• Because more organisms are produced than can
survive, they compete for limited resources.
Summary of Darwin's Theory
– Individuals best ___________ to their
environment survive and reproduce most
successfully.
– These organisms pass their heritable traits to
their offspring. Other individuals die or leave
fewer offspring.
– This process of natural selection causes
____________________ to change over time.
Summary of Darwin's Theory
– Species alive today are descended with
______________ from ancestral species that
lived in the distant past.
– This process, by which diverse species
evolved from common ancestors, unites all
organisms on Earth into a single tree of life.
Evolutionary Theory
• Evolutionary Theory
• Scientific advances in many fields of biology,
geology, and physics have confirmed and
expanded most of Darwin’s hypotheses.
• Evolutionary theory continues to change as new
data are gathered and new ways of thinking arise.
Testing Natural Selection
in Nature
• Testing Natural Selection in Nature
• Studies showing natural selection in action involve
_______________ of the finches that Darwin
observed in the Galápagos Islands.
• The finches Darwin saw were different, but he
hypothesized that they had descended from a
___________ ___________.
Testing Natural Selection in Nature
Testing Natural Selection in Nature
Testing Natural Selection
in Nature
• Peter and Rosemary Grant tested
Darwin’s hypothesis, which relied on two
testable assumptions:
• For beak size and shape to evolve, there must be
enough heritable variation in those traits to provide
raw material for natural selection.
• Differences in beak size and shape must produce
differences in fitness, causing natural selection to
occur.
Testing Natural Selection
in Nature
• The Grants tested these hypotheses on
the medium ground finch on Daphne
Major, one of the Galápagos Islands.
• During the rainy season, there is plenty of
food.
– During droughts, food becomes scarce.
– Individual birds with different-sized beaks had
different chances of survival during a drought.
Testing Natural Selection
in Nature
• When food was scarce, individuals with
large beaks were more likely to survive.
Testing Natural Selection
in Nature
• The Grants provided evidence of the
process of evolution.
• Beak size can be changed by natural
selection.
Summary
Natural Selection _____________ organisms that
are well ______________ to their
environment. Organisms that are less sated to
the environment may die off before passing on
their traits. ___________ _____________
can be used to explain adaptation and its
effects on the number and types of species
that currently exist. When a species is unable
to adapt to meet its needs, it may _____ out
completely.