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

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. AAATCGGCAAACCGGC

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.

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).

AAAGAGAAAGAAGAG 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.

Addition/Deletion

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.

Germ Cell Mutation

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. tripEnglandSouth AmericaNew

ZealandAustraliaSouth AmericaEngland. 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

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: 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

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

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. These traits soon predominate in the

population.Leads to new species development over time.

Lamarck’s Theory of Acquired Characteristics

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.

Does not account for new species generation.

Hardy Weinberg (Where Math meets Biology) Allele frequency remains unchanged over time. For this to be true the following assumptions must be

met: 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 Very Large Population

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.

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.

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

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.

Non Random Mating

Inbreeding Results in an increase of homozygous

individuals

Hardy Weinberg Notation

P represents the allele frequency of the dominant alleleThe percentage of the alleles in a population

which are dominant for the trait being studied q represents the allele frequency of the

recessive alleleThe percentage of the alleles in a population

which are recessive for the trait being studied

Hardy Weinberg Formulas

P + q = 1The frequency of the dominant allele (P) plus

the frequency of the recessive allele (q) = 1All the white eye alleles plus all of the red eye

alleles equals all of the eye color alleles for the population.

Hardy Weinberg Formulas

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

RR, Rr, rr Depending on the information you have,

you can calculate actual frequencies or estimated frequencies

Allele CalculationGenotype Individuals # R # r

RR 20 40*

Rr 40 40** 40**

rr 40 80*

Totals 100 80 120

*You have 20 RR individuals, that means each individual possesses 2 R allelesSo the total number of R alleles is 2 x 20 = 40You 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 is40 R alleles and 40 r alleles

Actual Allele Calculation

To calculate the actual allele numbers use the total allele numbersFrom the preceding slide:Total # r alleles = 120Total # of all alleles = 80 R + 120 r = 200The actual allele frequency is 120/200 = 0.6So q = 0.6 You calculate P by using P + q = 1P = 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

Estimated Allele Frequencies

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

Try these …

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

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 …

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?

Genotype # in Population A alleles a alleles

AA 44 88

Aa 25 25 25

aa 31 62

total 100 113 87

Answers …

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 …

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

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 …

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.

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

Archaebacteria. Eubacteria. Prostista. Fungi. Plantae. Animalia.

How Are Organisms Put Into These Groups? Symmetry

RadialBilateralNone

Skeletal typeEndoskeletonExoskeletonNone

How Are Organisms Put Into These Groups? Add the rest of them … internal systems

(circulatory, nervous, digestive)

How Are Ecosystem Organized

Populations Individuals of the same species in the same location.

Southeastern Pennsylvania White tail Deer.

Communities Population of different species in the same location:

Deer, trees, grass, insects, bears, Mountain Lions in Pocono Forest.

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

Biomes Large 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.

Food Webs ProducersMake their own food. ConsumersEat other life forms.

How Are Ecosystem Organized

PlantsProducers.Harness energy from the sun.Light reactions versus Dark reactions.

Herbivores VegetariansEat plants.Primary consumers.

How Are Ecosystem Organized

Carnivores Eat Animals Secondary consumers. Eat primary consumers.

Omnivores Eat anything Eat 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.

Planetary Cycles Water Cycles

Water cycles back and forth. Between the atmosphere. And the surface of the planes.

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

Carbon Cycle Plants remove CO2 from the

atmosphere in photosynthesis CO2 in atmosphere diffuses

into oceans. What role does the

temperature of the ocean play in this ability?

CO 2 released to atmosphere by: Cellular respiration. Burning of fossil fuels. Decomposition of organic

materials.