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GENES AND VARIATION
OBJECTIVES: 16.1
Explain what a gene pool is.
Identify the main source of inheritable variation in
a population.
State determines the numbers of phenotypes for a
given trait.
Genetic ________ is studied in a population (a group
of individuals of the same ______ that interbreed).
The individuals share a common group of genes called
a ____ _____.
A gene pool consists of ___ genes, including all the
different _______, that are present in a population.
The relative frequency of an _____ 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.
_________ is any change in the relative frequency
of alleles in a population.
The two main sources of genetic variation are
__________ and the genetic _________ that
results from sexual reproduction.
A mutation is any _______ in a sequence of DNA.
They can occur because of mistakes in ________,
radiation, or chemicals in the environment.
Many mutation do not produce changes in the
_________ of the individual.
Human _____ mutation.
They believed that this
man was born with the
___ virus that causes the
growth of all these
______ that cover his
body and creates the
illusion that branches
are covering his skin
Most _______ differences are due to gene
shuffling that occurs during the production of
_______.
Another process, ___________, also occurs during
________ which increases the number of different
_________ that can appear in offspring.
The number of _________
produced for a given trait
depends on how many ______
control the trait.
Among humans, a widow’ peak – a downward dip
in the center of the hair line – is a ______-gene
trait.
The allele for the widow’s peak is _________ over
the allele for the hair line with no widow’s peak.
Many traits are controlled by two or more genes
and are, called _________ traits.
Each gene of a trait has two or more ______.
EVOLUTION AS GENETIC CHANGE
OBJECTIVES: 16.2
Explain how natural selection affects single-gene
and polygenic traits.
Describe genetic drift.
List the five condition needed to maintain genetic
equilibrium.
The _______ of an organism is measured in its
ability to _____ its genes on the next generation.
_______ _______ never acts directly on _____.
Because it is an entire _______ – not a single gene
– that either survives and reproduces or dies
without reproducing.
If and individual produces many ________, its
alleles stay in the gene pool and many increase in
frequency.
Natural selection on single-gene traits can lead to
changes in allele frequencies and thus to _______.
During the ________ Revolution a lot of soot was
put into the atmosphere and it collected on trees.
The soot making the ______
peppermoth more visible.
Because of this the _____
peppermoth became predominant
over it white cousin.
Peppermoth of England
Natural selection can affect the __________ of
phenotypes in an of three ways.
1. __________ selection – when the individuals at one
end of the curve have higher fitness than those in the
middle or the other end.
2. ________ selection – when individuals near the
center have higher fitness than the individuals at
either end of the curve.
3. _________ selection – when the individuals at the
upper and lower ends of the curve have higher fitness
than those near the middle.
In _____ populations, individuals that carry a
particular allele may leave more descendants than
other individuals, just by chance.
Over time, a series of chance occurrences of this type
can cause an _____ to become common in a
population.
_____ ______ is the random change of allele
frequency.
A situation in which ____ frequencies change as a
result of the ________ of a small subgroup of a
population.
The ____________ principal states that the allele
frequencies in a population will remain _______ unless
one or more factor cause those frequencies to change.
Genetic ________ is the situation the allele frequency
remains _______.
____ conditions are required to maintain genetic
equilibrium from generation to generation:
1. There must be _______ mating; all members of the
population must have a equal opportunity to produce
offspring.
2.The population must be very large; genetic drift
has less ______ on a large population
3.There can be no movement ____ or ___ of the
population; new individuals may bring in new
_____ in to a population.
4. No _________; if genes mutate from on form into
another form, new alleles may be introduce into
the population.
5. No ________ selection; all genotypes must have
the same probabilities of _______ and
__________.
THE PROCESS OF SPECIATION
OBJECTIVES: 16.3
Identify the condition necessary for a new species
to evolve.
Describe the process of speciation in the Galapagos
finches.
__________ is the formation of new species.
A _______ is a group of organisms that breed with
one another and produce ______ offspring.
As new species evolve, population become
reproductively ________.
When the members of two populations cannot
_________ and produce ______ offspring,
reproductive isolation has occurred.
At that point the _________ had different genic
pools.
_________ isolation occurs when two
populations are capable of interbreeding but have
difference in courtship _____ or other
reproductive strategies that involve behavior.
__________ isolation occurs when two
populations are separated by geographic barriers
such as rivers, ________ or bodies of water.
_______ isolation occurs when two or more
species reproduce at different times.
Geographic isolation
Speciation in the
_______ finches
occurred by founding
of a new population,
geographic isolation,
changes in the new
population’s gene pool,
and _______
competition.
A few finches (_______) from the South American
mainland – species A – flew or were blown to one of
the Galapagos Islands.
Later a few birds of species A cross to another
island (________).
Over time, populations on each island become
_______ to their local environment.
One island may have produced a _____ with a thick
husk and the birds adapted by growing _____ beaks,
resulting in species B.
A few birds from species B fly over to the island
inhabited by species A.
Species A will not mate with species B because
species A prefers _____ beak size.
The gene pool of the two species are now ______.
The two are now _______ species.