Download Gene Pool

Friday 4/18
Wed. 2/13 – 16.1
LT:
1. Explain what a gene
pool is
2. Identify the main
sources of
inheritable variation
in a population
3. State what
determines how a
phenotype is
expressed
ET:
• Outline sections 16.1 and
16.2
• Highlight headings and
underline new vocabulary
words (the bolded ones)
• These must be quality
outlines if you want to
receive full credit
Friday 4/18 – Genes and Variation
_______________________________________________________
Daily Objective:
By the end of today I should be able to…
• Explain what a gene pool is
• Identify that main sources of inheritable
variation in a population
Entrance Activity:
What are the 2 important factors that
Darwin was unable to explain? (17.1)
Why was he unable to explain them?
Gene Pool: The combined genetic information
of all the members of a particular population
Relative Frequency: The number of times
an allele occurs in a gene pool
• Pg. 483 – How many alleles for black fur are
there vs. alleles for white fur?
What are the 2 main sources of
genetic variation?
1. Mutations: Any change in a sequence of DNA
Q: how do mutations occur?
radiation, environment, replication of DNA
2. Gene Shuffling: Your 23 pairs of chromosomes
can produce 8.4 million different combinations
of genes!
Q: how do chromosomes get arranged so
differently?
Independent assortment and crossover
The number of phenotypes produced for
a given trait depends on how many
genes control the trait.
• Single-Gene Traits:
Controlled by a single
gene that has 2 alleles
Ex. Widows peak pg. 395
• Polygenic traits: Controlled
by 2 or more genes, each
with 2 or more alleles
Ex. Height
• Polygenic traits produce a
bell-shaped curve when
graphed – “normal
distribution.”
• Create a data table
to record the height
of each individual in
the room
• Create a graph
using frequency and
height, just like the
one on pg. 396
Friday, February 15th, 2013
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Daily Objective:
By the end of today I should be able to…
• Explain genetic drift
• Describe the conditions necessary for
genetic equilibrium to be maintained.
Entrance Activity:
What are the 3 ways that natural selection
can affect the distributions of phenotypes
Natural Selection on…
Directional Selection
• When nature selects
individuals at one end of
the bell curve as the
fittest
Directional Selection
Key
Directional Selection
Food becomes scarce.
Low mortality,
high fitness
High mortality,
low fitness
Stabilizing Selection
• When nature
selects individuals
in the middle of
the curve as more
fit and the bell
narrows
Stabilizing Selection
Key
Low mortality,
high fitness
High mortality,
low fitness
Birth Weight
Selection against
both extremes
keep curve
narrow and in
same place.
Disruptive Selection
• When nature
selects individuals
at opposites ends
of the curve as
more fit.
Genetic Drift
• In small populations,
individuals with a specific
trait may leave more
desendents, just by chance.
• When allele frequency is
altered by the migration of
a small population it is
called the – “founder
effect”
Evolution vs. Genetic Equilibrium
5 conditions can disturb equilibrium
and cause evolution to occur…
Genetic Equilibrium
Hardy-Weinberg principle:
Allele frequencies in a population will remain constant
unless one or more factors cause those frequencies to
change.
5 conditions that must be constant for equilibrium …
If conditions are not met, the population will evolve.
REVIEW!!!
What is genetic drift?
A population’s gene pool has
to be kept together and
separate from the gene
pools of other
populations
No selective pressures!!
Thursday. 2/23 – 16.3
LT:
• Identify conditions
necessary for a new
species to evolve
• Describe the process of
speciation
Speciation
• The formation of new species based on a
significant change in allele frequency
As new species evolve, populations
become reproductively isolated from
each other
Behavioral Isolation
• 2 populations are capable
of interbreeding but have
differences in courtship
rituals or other types of
behaviors
• Ex: Eastern Meadowlark
and Western Meadowlark
Geographic
Isolation
• Two populations are
separated by geographic
barriers such as rivers,
mountains or bodies of
water.
• Ex: Abert squirrel and
Kaibab squirrel
Temporal Isolation
• 2 or more species
reproduce at
different times
• Ex: different frog
species live and
breed in the same
pond, but they
reproduce at
different times of
the year.
BioEd Online
Common water frog
Rana esculenta
Speciation in Darwin’s Finches
• Read and summarize steps 1-6 on pg. 408
• Compare your steps to fig. 16-17 pg. 410
Analyzing Data: complete the activity on pg. 408
“How Are These Fish Related”
Answer #1-4 in NB
Tuesday 2/28/2012
LT: Last day to review for
exam!
*Test Tomorrow