Transcript Unit 4 Power Point Notes

Unit 4
Evolution and Ecology
Mutations

Any alteration in the base sequence of DNA
 Errors
can occur naturally during DNA replication.
 DNA can be changed by radiation and other
mutagens
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Most discovered and corrected by proof reading
enzymes.
Some still are missed.
Theoretical basis for Natural Selection.
Point Mutation

The substitution of one base for another.
 AAATCGGCAAACCGGC
 Replacing the “T” with a “C” changes the T/A pair to a C/G
pair.
 The particular change would alter the amino acids for the
codon from SER to GLY.
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May or may not affect the functioning of the
protein.
The effect may be positive; i.e., a change which
results in a more efficient protein.
Silent Mutation

An alteration of the DNA sequence which
does not alter the amino acid sequence.
 Remember
the codon table
 there is usually more than one codon for each
amino acid. (Same protein produced mutation has no effect).

AAAGAGAAAGAA
 GAG
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is Glutamate … GAA is Glutamate
no difference in the protein
Frame Shift Mutation
Insertion or deletion of 1 or 2 DNA bases
shifts the reading frame for the entire
downstream sequence.
 Alters virtually every codon downstream.
 Results in a nonfunctional protein.
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Addition/Deletion
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Large insertion or deletion of DNA results
in nonfunctional protein.
Somatic Cell Mutation
Somatic cells—Every cell in your body that
is not a sex cell (sperm/egg).
 Mutations in somatic cells not passed
along to offspring.
 Result most often from external damage.
 Precursor to cancer.
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Germ Cell Mutation
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Mutation in egg/sperm.
Passed on to offspring.
`Basis for Natural Selection.
Why does changing the A.A. change the
protein?
20 Amino Acids
 Each has own unique shape and properties.
 Proteins fold into 3-D shape and specific active
sites.
 Altering the A.A. may disrupt either the 3-D shape or
the active site.
Causes Of Mutations

Internal
 Defective
DNA polymerase. (Makes more DNA).
 Error/proof reading enzymes.

External Mutation
 Gamma
rays
 UV radiation
 Free radicals
 Carcinogens—any substance which causes DNA
damage.
Darwin’s Theory Of Selection

Darwin was the Naturalist who sailed on the
Beagle
5
yr. tripEnglandSouth AmericaNew
ZealandAustraliaSouth AmericaEngland.
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Collected living specimen and fossils throughout
the trip.
Fossils were similar but not identical to current
living organisms.
Observed that characteristics varied within the
same species in different populations.
Natural Selection
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Those individuals better equipped to survive will reproduce at a
higher rate and with greater success.
Overtime the traits of these individuals will accumulate in a given
population.
Eventually a new species:
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E.g., Differences in beak shape and size arose in varying population to
exploit different food sources.
Species isolation leads to differentiation.

Species are defined by their ability to mate and reproduce viable
offspring.
 Horse + donkey = Mule

Mules are sterile therefore horses and donkeys are separate species
because they cannot create viable fertile offspring.
Artificial Selection
Man chooses which individual will send
their DNA into the next generation.
 Select those individuals which passes the
traits which you find desirable.

 E.g.,
Dogs, descended from wolves.
 Man has selectively bred dogs for specific
characteristics creating all the dog breeds we
have today
Types Of Selection
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Stabilizing:
Selection for the average.
Selection against the extreme.
Chicken & ducks—Eggs of intermediate weight have
best hatching success.
Directional:
Selection for one extreme & against the other extreme.
Humans—Height is increasing generation after
generation.
Types Of Selection
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Disruptive: (Least Common)
Selection for extremes.
Selection against the average.
Nonpoisonous butterfly mimics the color marking
of the poisonous one.
Those who are completely successful survive.
Those butterflies who miss by a little are eaten
by predators.
generation.
Natural Selection Leads to Evolution

The better suited individuals produce more
offspring.
 Their
DNA passed down more often & with
more success.
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These traits soon predominate in the
population.
 Leads
to new species development over time.
Lamarck’s Theory of Acquired
Characteristics
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Abilities developed in the current
generation would be passed on to the next
generation:
 Example:
Giraffes stretched their necks to
reach food so next generation would be born
with stretched necks.
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Does not account for new species
generation.
Hardy Weinberg (Where Math meets
Biology)
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Allele frequency remains unchanged over time.
For this to be true the following assumptions must be
met:
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Very large population.
Random mating.
No mutation.
No migration into or out from the population.
No Natural Selection.
May seem restrictive but if the population is large
enough the other conditions have a minimal impact.
Hardy Weinberg Principles
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Very Large Population
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Small populations do not have the numbers for these statistical equations to hold true
Random Mating
Each individual must have an equal chance of mating with every other individual.
Utilizing criteria for choosing a mate can affect allele frequencies.
Mutation
Alteration of DNA.
Usually at such low frequency it does not directly affect the allele frequencies from one generation to the next.
Migration
Movement of individuals into or out from a population.
Depending on the size of the population & the size of migration can affect Hardy Weinberg Theory.
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Natural Selection
Applying pressure which selects a set of individuals will definitely alter allele frequencies.
Like mutation, however, it occurs in general very slowly so as not to alter allele frequencies from one generation to
the next.
Genetic Drift
Characteristic of very small populations.
 If an allele has a very low frequency it can
be lost from a population in a single
generation.
 A single individual not mating can remove
the allele.
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Founder Effect
Small group of individuals migrate to begin
new population.
 Only those alleles in the founders will be
represented in the resulting population.
 May have very different allele frequencies
than the original generation.
 Amish
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Bottle Neck Effect
Same outcome as the founder effect.
 Population decimated by natural disaster.
 Only a small number remain.
 New population will only have the alleles
from the survivors.
 Cheetahs—All cheetahs are virtually
genetically identical.
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Non Random Mating
Inbreeding
 Results in an increase of homozygous
individuals
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Hardy Weinberg Notation
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P represents the allele frequency of the
dominant allele
 The
percentage of the alleles in a population
which are dominant for the trait being studied

q represents the allele frequency of the
recessive allele
 The
percentage of the alleles in a population
which are recessive for the trait being studied
Hardy Weinberg Formulas
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P+q=1
 The
frequency of the dominant allele (P) plus
the frequency of the recessive allele (q) = 1
 All the white eye alleles plus all of the red eye
alleles equals all of the eye color alleles for
the population.
Hardy Weinberg Formulas
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P2 + 2Pq + q2 = 1
 P2
- this represents the homozygous dominant
individuals
 2Pq – this represents the heterozygous individuals
 q2 – this represents the homozygous recessive
individuals
 This formula says that the number of homozygous
dominant plus the heterozygotes plus the
homozygous recessive = all of the individuals in the
population
Allele Frequencies
Round allele (R) and Wrinkled allele (r)
 There are three possible genotypes
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 RR,
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Rr, rr
Depending on the information you have,
you can calculate actual frequencies or
estimated frequencies
Allele Calculation
Genotype
Individuals
#R
RR
20
40*
Rr
40
40**
rr
40
Totals
100
#r
40**
80*
80
120
*You have 20 RR individuals, that means each individual possesses 2 R alleles
So the total number of R alleles is 2 x 20 = 40
You have 40 rr individuals each has 2 r alleles so 2 x 40 = 80
** The heterozygotes have 1 R allele and 1 r allele so 40 Rr individuals is
40 R alleles and 40 r alleles
Actual Allele Calculation
To calculate the actual allele numbers use
the total allele numbers
From the preceding slide:
Total # r alleles = 120
Total # of all alleles = 80 R + 120 r = 200
The actual allele frequency is 120/200 = 0.6
So q = 0.6
You calculate P by using P + q = 1
P = 0.4
Estimated Allele Frequencies
The only individuals you know their
genotype are the homozygous recessive
 You can use the proportion of
homozygous recessive individuals in a
population to estimate the allele
frequencies for that population
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Estimated Allele Frequencies
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From the example you have 40 homozygous
recessive individuals in a population of 100 or
40/100 = 0.4
You know from P2 + 2Pq + q2 = 1 that
homozygous recessive individuals are the q2
But you want q. Soooo q2 = 0.4
Take the square root this to calculate q
√0.4 = 0.63
Estimated Allele Frequencies
Now you know q … you calculate p by
using P + q = 1
 q = 0.63
 P + 0.63 = 1
 P = 1 – 0.63
 P = 0.37
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Try these …
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In HW Lingo, P is the frequency of the dominant
allele while q is the allele frequency of the
recessive allele.
1. How do you identify the dominant vs the
recessive alleles?
2. In the equation P2 + 2Pq + q2 = 1
What does P2 represent?
What does 2 Pq represent?
What does q2 represent?
Answers
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1. How do you identify the dominant vs the recessive alleles?
 1. Dominant is denoted by the upper case letter in Aa the A,
recessive is the lower case letter
2. In the equation P2 + 2Pq + q2 = 1 What does P2 represent?
 P2 are the homozygous dominant individuals of the population
What does 2 Pq represent?
 2 Pq are the heterozygotes in the population.
What does q2 represent?
 q2 are the homozygous recessive individuals of the population.
More to try …
Genotype
# in Population
A alleles
AA
Aa
aa
total
44
25
31
100
88
25
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113
a alleles
25
62
87
Why with only 44 AA individuals are there 88 A alleles?
Why with 25 Aa individuals are there 25 A and 25 a alleles?
Which three numbers do you use to calculate the actual frequency of
the A allele?
Answers …
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Why with only 44 AA individuals are there 88 A alleles?
 44 AA individuals, each one has 2 A alleles so 2 x 44
= 88
Why with 25 Aa individuals are there 25 A and 25 a
alleles?
 25 Aa individuals, each one has one A and 1 a so
there are 25 A and 25 a from this group of
heterozygotes of the population.
Which three numbers do you use to calculate the actual
frequency of the A allele?
 To calculate the actual frequency of A you need the
total number of A alleles = 113, and the total of the A
alleles + a alleles (113 + 87) = 200
More practice …
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5. Calculate the actual frequency of the A allele.
Show your work.
6. Which two numbers do you use to calculate
the estimated frequencies?
7. Why do you use those numbers (from
question 6) to calculate the estimated
frequencies?
8. Calculate the estimated frequencies for both
A and a.. Show all your work.
More practice … answers
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5. Calculate the actual frequency of the A allele. Show your work.
 Total number of A alleles = 113 divided by the total of all alleles
200
 113/200 = .56
6. Which two numbers do you use to calculate the estimated
frequencies?
 You use the number of homozygous individuals in the population
for this group 31 homozygous out of a population of 100.
7. Why do you use those numbers (from question 6) to calculate the
estimated frequencies?
 You use the homozygous recessive individuals because they are
the only ones whose phenotype tells you their genotype.
Even more practice …
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8. Calculate the estimated frequencies for
both A and a.. Show all your work.
Even more practice … answers
8. Calculate the estimated frequencies for both A and a.. Show all your
work.
You cannot use the homozygous dominant for estimated frequencies. When
you have a dominant individual you don't know by looking whether they are
homozygous or heterozygous. That's why you use the homozygous
recessive individuals to calculate estimated frequencies. They are the only
individuals that you know their genotype just by their phenotype.
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q2 = 31/100 = .31
Take the square root of .31 = .556 = q
P+q=1
P + .556 = 1
P = 1 - .556
P = .444
Life Forms Are Categorized Into
Six Kingdoms
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Archaebacteria.
Eubacteria.
Prostista.
Fungi.
Plantae.
Animalia.
How Are Organisms Put Into These
Groups?
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Symmetry
 Radial
 Bilateral
 None
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Skeletal type
 Endoskeleton
 Exoskeleton
 None
How Are Organisms Put Into These
Groups?
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Add the rest of them … internal systems
(circulatory, nervous, digestive)
How Are Ecosystem Organized
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Populations
 Individuals of the same species in the same
 Southeastern Pennsylvania White tail Deer.
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location.
Communities
 Population of different species in the same location:
 Deer, trees, grass, insects, bears, Mountain Lions in Pocono
Forest.
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Ecosystems
 Community plus its non-living regions.
 Elevations, soil types, rainfall, temperature, etc.
 Deer, trees, grass, insects, Mountain Lion in Pocono
Mountain Forest.
How Are Ecosystem Organized
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Biomes
 Large
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geographical regions of similar characteristics:
Desert, Tropical Rain Forest, Deciduous Forest, prairie.
 The
Pocono Mountain Forest has much in common
with the Colorado Deciduous Forest.
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Food Webs
 ProducersMake
their own food.
 ConsumersEat other life forms.
How Are Ecosystem Organized
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PlantsProducers.
 Harness
energy from the sun.
 Light reactions versus Dark reactions.
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Herbivores Vegetarians
 Eat
plants.
 Primary consumers.
How Are Ecosystem Organized
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Carnivores  Eat Animals
 Secondary
consumers.
 Eat primary consumers.
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Omnivores  Eat anything
 Eat
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plants and animals.
Decomposers
 Recycle
dead organic matter (plants and animals).
 Bacteria, fungi, insects, worms.
How Are Ecosystem Organized
Energy decreases as you go up in the
food web.
 Number of individuals decreases as you
go up in the food web.
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Planetary Cycles
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Water Cycles
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Water cycles back and forth.
 Between the atmosphere.
 And the surface of the planes.
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Sublimation - Ice and snow skip the liquid stage and can directly
add H2O to the atmosphere.
Liquid water from lakes, rivers and oceans evaporate into
atmosphere.
Water returns to the surface via precipitation.
Planetary Cycles
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Carbon Cycle
Plants remove CO2 from the
atmosphere in photosynthesis
CO2 in atmosphere diffuses
into oceans.
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What role does the
temperature of the ocean play
in this ability?
CO 2 released to atmosphere
by:
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Cellular respiration.
Burning of fossil fuels.
 Decomposition of organic
materials.