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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.

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Presentation on theme: "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."— Presentation transcript:

1 Unit 4 Evolution and Ecology

2 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.

3 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. 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.

4 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 is Glutamate … GAA is Glutamate no difference in the protein

5 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.

6 Addition/Deletion Large insertion or deletion of DNA results in nonfunctional protein.

7 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.

8 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.

9 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.

10 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. 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.

11 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.

12 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

13 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.

14 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.

15 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.

16 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.

17 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.

18 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.

19 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.

20 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

21 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.

22 Non Random Mating Inbreeding Results in an increase of homozygous individuals

23 Hardy Weinberg Notation 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

24 Hardy Weinberg Formulas 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.

25 Hardy Weinberg Formulas P 2 + 2Pq + q 2 = 1  P 2 - this represents the homozygous dominant individuals  2Pq – this represents the heterozygous individuals  q 2 – 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

26 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

27 Allele Calculation GenotypeIndividuals# R# r RR2040* Rr4040** rr4080* Totals10080120 *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

28 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

29 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

30 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 P 2 + 2Pq + q 2 = 1 that homozygous recessive individuals are the q 2 But you want q. Soooo q 2 = 0.4 Take the square root this to calculate q √0.4 = 0.63

31 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

32 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?

33 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.

34 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 PopulationA allelesa alleles AA4488 Aa25 aa3162 total10011387

35 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

36 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.

37 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.

38 Even more practice … 8. Calculate the estimated frequencies for both A and a.. Show all your work.

39 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

40 Life Forms Are Categorized Into Six Kingdoms  Archaebacteria.  Eubacteria.  Prostista.  Fungi.  Plantae.  Animalia.

41 How Are Organisms Put Into These Groups? Symmetry  Radial  Bilateral  None Skeletal type  Endoskeleton  Exoskeleton  None

42 How Are Organisms Put Into These Groups? Add the rest of them … internal systems (circulatory, nervous, digestive)

43 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.

44 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  Producers  Make their own food.  Consumers  Eat other life forms.

45 How Are Ecosystem Organized Plants  Producers.  Harness energy from the sun.  Light reactions versus Dark reactions. Herbivores  Vegetarians  Eat plants.  Primary consumers.

46 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.

47 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.

48 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.

49 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.


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