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Ch. 15 - 16
Evolution
By: Gabrielle Carlos Julio Sanchez Rios
Austin Paco Kay
James Enrique Grant
Alex Eduardo Handzel
Vocabulary
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Evolution: Is the change over time, is the process
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Theory: A well-supported testable
explanation of phenomena that have
occurred in the natural world.
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Fossil: Preserved remains of ancient
organisms.
by which modern organisms have descended from
ancient organisms.
Ch. 15 Section 1
Key Concepts
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During his travels, Darwin made numerous
observations and collected evidence that led
him to propose a revolutionary hypothesis
about the way life changes over time.
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Darwin observed that the characteristics of
many animals and plants varied noticeably
among the different islands of the Galápagos.
Ch. 15 Section 1
Key Concepts
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Hutton and Lyell helped scientists recognize that
Earth is many millions of years old, and the
processes that changed Earth in the past are the
same processes that operate in the present.
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Lamarck proposed that by selective use or disuse
of organs, organisms acquired or lost certain
traits during their lifetime. These traits could
then be passed on to their offspring. Over time,
this process led to change in a species.
Ch. 15 Section 2
Key Concepts
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Malthus reasoned that if the human
population continued to grow unchecked,
sooner or later there would be insufficient
living space and food for everyone.
Ch. 15 Section 2
Vocabulary
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Artificial Selection: In artificial selection, nature
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Struggle for Existence: Members of each
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Fitness: The ability of an individual to survive
provided the variation, and humans selected
those variations that they found useful.
species compete regularly to obtain food, living
space, and other necessities of life.
and reproduce in its specific environment.
Ch. 15 Section 3
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Adaptation: Is any inherited characteristic that
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Survival of the Fittest: Individuals with
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Natural Selection: Results in the changes of inherited
increases an organism's chance of survival.
characteristics that are not well suited to their
environment—that is, with low levels of fitness—either
die or leave few offspring. Individuals that are better
suited to their environment—that is, with adaptations
that enable fitness—survive and reproduce most
successfully.
traits in a population by survival of the fittest.
Ch. 15 Section 3
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Descent with Modification: Each living species has
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Common Descent: Many animals come from a common
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Homologous Structures: Structures that have
different mature forms but develop from the same
embryonic tissues
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Vestigial Organs: Small Traces of homologous
structures in different species.
descended, with changes, from other species over time.
ancestor or animal that sprouted into other different
animals.
Ch. 15 Section 3
Key Concepts

In artificial selection, nature provided the
variation, and humans selected those
variations that they found useful.
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Over time, natural selection results in
changes in the inherited characteristics of
a population. These changes increase a
species' fitness in its environment.
Ch. 15 Section 3
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Darwin argued that living things have
been evolving on Earth for millions of
years. Evidence for this process could be
found in the fossil record, the
geographical distribution of living species,
homologous structures of living
organisms, and similarities in early
development, or embryology.
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In genetic terms, evolution is any change in
the relative frequency of alleles in a
population.
The two main sources of genetic variation
are mutations and the genetic shuffling that
results from sexual reproduction.
The number of phenotypes produced for a
given trait depends on how many genes
control the trait.
The number of phenotypes a given trait has
is determined by how many genes control
the trait.
Ch. 16 Section 1- Key Terms
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A gene pool consists of all genes, including all
the different alleles, that are present in a
population.
The relative frequency of an allele is the
number of times that the allele occurs in a gene
pool, compared with the number of times other
alleles for the same gene occur.
Among humans, a widow's peak—a downward
dip in the center of the hairline—is a singlegene trait. It is controlled by a single gene that
has two alleles.
Many traits are controlled by two or more genes
and are, therefore, called polygenic traits.
Ch. 16 Section 1-Vocabulary
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Natural selection on single-gene traits can lead to changes in allele frequencies
and thus to evolution.
Natural selection can affect the distributions of phenotypes in any of three ways:
directional selection, stabilizing selection, or disruptive selection.
Directional selection occurs when individuals at one end of the curve have higher
fitness than individuals in the middle or at the other end.
Stabilizing selection takes place when individuals near the center of a curve have
higher fitness than individuals at either end.
When individuals at the upper and lower ends of the curve have higher fitness
than individuals near the middle, disruptive selection takes place.
In small populations, individuals that carry a particular allele may leave more
descendants than other individuals do, just by chance. Over time, a series of
chance occurrences of this type can cause an allele to become common in a
population.
Five conditions are required to maintain genetic equilibrium from generation to
generation: (1) There must be random mating; (2) the population must be very
large; and (3) there can be no movement into or out of the population, (4) no
mutations, and (5) no natural selection.
Ch. 16 Section 2-Key Terms
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When individuals at one end of the curve have higher fitness than individuals in
the middle or at the other end, directional selection takes place.
When individuals near the center of the curve have higher fitness than
individuals at either end of the curve, stabilizing selection takes place.
When individuals at the upper and lower ends of the curve have higher fitness
than individuals near the middle, disruptive selection takes place
random change in allele frequencies that occurs in small populations is
genetic drift.
A situation in which allele frequencies change as a result of the migration of a
small subgroup of a population is known as the founder effect
The Hardy-Weinberg principle states that allele frequencies in a population
will remain constant unless one or more factors cause those frequencies to
change.
The situation in which allele frequencies remain constant is called genetic
equilibrium .
Ch. 16 Section 2-Vocabulary
As new species evolve, populations
become reproductively isolated from
each other.
 Speciation in the Galápagos finches
occurred by founding of a new
population, geographic isolation,
changes in the new population's gene
pool, reproductive isolation, and
ecological competition.
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Ch. 16 Section 3-Key Terms
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But how do these changes lead to the formation of new
species, or speciation?
When the members of two populations cannot interbreed
and produce fertile offspring, reproductive isolation has
occurred.
One type of isolating mechanism, behavioral isolation,
occurs when two populations are capable of interbreeding
but have differences in courtship rituals or other
reproductive strategies that involve behavior.
With geographic isolation, two populations are separated
by geographic barriers such as rivers, mountains, or bodies
of water.
A third isolating mechanism is temporal isolation, in
which two or more species reproduce at different times.
Ch. 16 Section 3-Vocabulary
http://www.pbs.org/wgbh/evolution/
 http://evolution.berkeley.edu/
 http://www.darwins-theory-ofevolution.com/
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Web resources
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a.
Who went to the Galápagos islands to study variations in the characteristics of
animals and plants?
James Hutton, b. Charles Lyell, c. Charles Darwin, d. Thomas Malthus.
Among individuals of a species, differences are referred to as
Natural variation, b. fitness, c. natural selection, d. adaptation.
Tissues and organs animals have but don’t use, but may have used in the past
are called what?
Vestigial Organs.
Structures that come from the same tissues and organs in different species from
a common ancestor are called what?
Homologous structures.
Difference among individuals of a species are referred to as?
Fitness.
An inherited characteristic that inscreases an organism’s ability to survive and
reproduce is a what?
Adaptation.
True or false. Artificial Selection is the process by which nature chooses the fittest
to survive in their environment through characteristics.
False. It is Natural Selection.
Questions
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a.
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True or false. An animal in the past that is related to two present day animals is a
common ancestor.
True.
An animals Fitness is a result of:
A) Common Descent
B) Adaptations
C) Vestigial Organs
D) Mr. Umlor
The answer is B (or D)
Preserved remains of ancient organisms are called what?
Fossils.
Random change in allele frequencies is called what?
Genetic Drift.
If in a population, the middle sized organism is best fit, what would eventually
happen?
Stabilizing selection.
True or false. The combined getentic information of all members of a particular
population forms a gene pool.
True.
The success of an organisms survival and reproduction is its what?
Fitness.
Questions
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True or False. Directional selection is when individuals at one end of the curve are
equal to the other extreme.
False. It is disruptive selection.
A random change in a small populations allele frequency is called hwat?
Variation.
If a group of an individuals of the same species can interbreed, that makes it a
_____?
A population.
Once two animals of a population cannot interbreed anymore, what two things
occur?
Reproductive isolation, a new species is formed.
True or false. temporal isolationis when two or more species reproduce at different
times.
True.
Is Mr. Umlor cool?
A) Yes.
B) Maybe.
C) NO?!
D) How does this relate to biology?
Questions