{ Macroevolution & Hardy Weinberg Equilibrium Mr. Joey Norman BGHS 5/3/2014

  Multiple-Choice Strategies   * Don't be afraid to write in the test book. When you take the exam, you will be given a test book and a Scantron® answer sheet on which you will bubble in your answers. No one is going to look at the test book itself -- only your answers on the answer sheet will be scored. Therefore, feel free to write all over your test book (but keep the answer sheet neat). Circle the questions in the book that you skip so you can easily find them again... cross out the letters of choices that are definitely wrong... mark up graphs... write whatever it takes in the book to get the right answer.   * Don't think too hard. There are easy questions and there are hard questions. Don't let the easy questions mislead you. If you come across what seems like an easy question, it probably is. Don't suspect everything to be a trick question. May 12, 2014

  Multiple-Choice Strategies   * Pace yourself. Don't spend too much time on any problem. You have 90 minutes to answer 63 multiple choice questions & 6 grid-in, quantitative questions -- that leaves you about 45 seconds per question. If you come across a question you can't answer, mark it so you can easily come back to it later. If you can eliminate some answer choices right off, mark those too. The questions on the exam are NOT arranged from easy to hard, so you don't want to waste time mulling over hard questions and not try all the questions on the test. Why spend so much time answering a hard question when you can answer three easy ones and get three times the points in the same amount of time? The test is designed so that the average person earns a score of 50%, so it is recommended to guess and not to leave any question blank.   Watch for key phrases like "all of the following EXCEPT" and "NOT" in the questions. The College Board loves questions with these words in them. By adding these words, the test writers force you to go through each answer choice and determine whether or not it is true or false. Normally, a multiple- choice question will ask you to pick out the correct answer (true statement). When the phrases "EXCEPT" and "NOT" are used, however, you must pick out the incorrect answer (false statement). To avoid confusing themselves, many students find it useful to mark true statements with a "T" in their test book and false statements with an "F." May 12, 2014

  Free-Response Strategies   * 90 minutes – 2 long FRQ’s & 6 short FRQ’s   Write your strongest answer first.   Unload all the information in your brain.   Answer all parts of the question.   Don't do more than is required.   Answer each part of the question separately.   Try every question.   Don't be afraid to guess.   ATFQ May 12, 2014

Macroevolution

 The only source of NEW genes & NEW alleles  Only mutations in cell lines that produce gametes can be passed on to offspring I. Mutations

 A) Point Mutation  Change in one base in a gene  Can impact phenotype  Sickle cell anemia Types of Mutations

 B) Chromosomal Mutation  Delete, disrupt, duplicate, or rearrange many loci at once  Most are harmful, but not always Types of Mutations

 Population loses or gains alleles by genetic additions or subtractions  Results from movement of fertile individuals or gametes  Reduces the genetic differences between populations, makes populations more similar II. Gene Flow

 Unpredictable fluctuation in frequencies from one generation to the next  The smaller the population, the greater chance  Random & nonadaptive III. Genetic Drift

 A) Founder effect = individuals are isolated and establish a new population – gene pool is not reflective of the source population III. Genetic Drift

 B) Bottleneck effect = a sudden change in the environment reduces population size – survivors have a gene pool that no longer reflects original III. Genetic Drift

1. Genetic drift is significant in small populations 2. Genetic drift causes allele frequencies to change at random 3. Genetic drift can lead to a loss of genetic variation within populations 4. Genetic drift can cause harmful alleles to become fixed III. Genetic Drift

 Alleles are passed to the next generation in proportions different from their frequencies to the present generation  Those that are better suited produce more offspring than those that are not IV. Natural Selection

 Natural selection acts more directly on the phenotype and indirectly on the genotype  Can alter the frequency distribution of heritable traits in 3 ways:  1) Directional selection  2) Disruptive selection  3) Stabilizing selection IV. Natural Selection

 1) Directional selection  Individuals with one extreme of a phenotypic range are favored, shifting the curve toward this extreme  Example: Large black bears survived periods of extreme cold better than small ones, so they became more common during glacial periods IV. Natural Selection

 2) Disruptive Selection  Occurs when conditions favor individuals on both extremes of a phenotypic range rather than individuals with intermediate phenotypes  Example: A population has individuals with either large beaks or small beaks, but few with intermediate – apparently the intermediate beak size is not efficient in cracking either the large or small seeds that are available IV. Natural Selection

 Stabilizing Selection  Acts against both extreme phenotypes and favors intermediate variations  Example: Birth weights of most humans lie in a narrow range, as those babies who are very large or very small have higher mortality rates IV. Natural Selection

 Why Natural Selection cannot produce perfect organisms:  1) Selection can only edit existing variations  2) Evolution is limited by historical constraints  3) Adaptations are often compromises  4) Chance, natural selection, & the environment interact IV. Natural Selection

Hardy-Weinberg

 Used to test whether a population is evolving  Used to describe a population that is NOT evolving  Frequencies of alleles & genes in a gene pool will remain constant over generations Hardy-Weinberg Equilibrium

5 Conditions for Hardy-Weinberg  1) No mutations  2) Random mating  3) No natural selection  4) The population size must be large (no genetic drift)  5) No gene flow (Emigration, immigration, transfer of pollen, etc.)

p 2 + 2pq + q 2  p = dominant allele  p 2 = homozygous dominant (BB)  q = recessive allele  q 2 = homozygous recessive (bb)  2pq = heterozygous (Bb) Hardy-Weinberg Equilibrium

Example:

Example: 90% = B (p) = % = b (q) = 0.10  What percentage is Bb? p 2 + 2pq + q 2 p 2 ?pq? q 2 ? 2pq = 2(0.90)(0.10) =.18 or 18% Bb Hardy-Weinberg Equilibrium

Examples: 1 2 3

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