Period+3+GR+23


 * ​ AP Biology**
 * Guided Reading Chapter 23**

1. Define the following terms: beal. . . good!

a. Microevolution evolutionary change below the species level; change in the genetic makeup of a population from generation to generation.

b. Population a localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).

c. Population genetics the study of how populations change genetically over time.

d. Gene pool the total aggregate of genes in a population at any one time.

2. What is the Hardy-Weinberg Theorem and why does it appear to be an apparent contradiction to evolution? beal. . . good!

-The principle that frequencies of alleles and genotypes in a population remain constant from one generation the the next. -It contradicts that evolution exists because if any one of the H-W standards* aren't met, evolution occurs.
 * Standards are: extremely large population size, no gene flow, no mutations, random mating, and no natural selection.

3. What is Hardy-Weinberg equilibrium? beal. . . good!

The condition describing a non-evolving population (one that is in genetic equilibrium).

4. Use the blank diagram below to relate the H-W equation to a Punnett square.

beal. . . cool...

5. What are the five conditions for H-W equilibrium to maintained? 1. Large population 2. No mutations 3. No migration 4. Random mating 5. No natural selection

beal. . . good!

6. How can the H-W equation be used to today in terms of human health? It can help determine the amount of people who carry the gene. beal. . . what kind of gene?

7. What are the two broad processes that make evolution possible? beal. . . good!

Sexual recombination and mutations.

8. What is the impact of the following: a. Point mutation -most are harmless because the DNA in eukaryotic genomes does not code for protein products. In sickle cell anemia theres a mutation in one cell causing the disease. beal. . . a change in a gene at a single nucleotide pair!

b. Gene duplication -if the duplication has no effects it can be helpful over generations, if it does have effects it can be very harmful beal. . . how?

c. Sexual recombination -recombines alleles into new arrangements in offspring and new phenotypes are made

9. What is the relationship between mutation rates and generation span? The mutation rates in plants and animals tend to be low, about 1 mutation in every 100,000 genes per generation. In viruses and microorganisms, which have shorter generation spans, mutations causing genetic variation occur more rapidly. For example, HIV has a generation span of only abot two days and has a much higher mutation rate than typical DNA genomes so mutant forms arise much more quickly. beal. . .good!

10. Define the following: beal. . .good! a. Genetic drift ​ ​ unpredictable fluctuations in allele frequencies from one generation to the next because of a population's finite size

b. Bottleneck effect ​ genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population

c. Founder effect ​ genetic drift that occurs when a few individuals become isolated from a larger population with the result that the new population's gene pool is not reflective of the original population

d. Gene flow ​ genetic additions to or subtractions from a population resulting from the movement of fertile individuals or gamates

11. Why would we discuss adaptive evolution and what role does natural selection play? To understand how a population changes over time because of its environment. Natural selection is the only change to a gene pool likely to adapt a population to its environment. beal. . .OK!

12. Give examples of phenotypical variation that is not inheritable. beal. . .good! When map butterflies emerge in spring they are orange and brown, but when they emerge in late summer they are black and white.

13. Explain the terms phenotypic polymorphism and genetic polymorphism in common terms giving an example from your own experience. I will be looking for a reasonable answer for this question.

Phenotypic Polymorphism: A phenotype that morphs or mutates 2 or more distinct times and is represented in high frequencies is noninheritable Example: I have a Widow's Peak and my sister does not.

 ** Beal ...Phenotypic polymorphism is 2 or more distinct morphs, each represented in a population with high enough frequency to be readily noticeable. An example is being male or female. **

Genetic Polymorphism: The result in height for alleles that influence height. These Genetic Polymorphism is heritable. Example: Eye color is a genetic Polymorphism. I have hazel green eyes and my mom has hazel green eyes.

14. How do we measure genetic variation? beal. . .good! To measure genetic variation you determine the amount of heterozygosity at both the level of whole genes and the molecular level of DNA.

15. How can very small differences in nucleotide sequences lead to such diversity in the human population? Since nucleotide sequences are crutial for identification of an organism, a small change in one sequence can alter every generatrion after that specific mutation. That leads to such diversity in the human population becasue of all the different traits humans posses.

beal. . .if the nucleotide change leads to a phenotypic change that is noticable and not bad for the population. . . this phenotypic change is then allowed to survive in the species and is expressed. the more of these types of changes. . . the more diverse the population!

16. What is geographic variation and how does the term cline relate? Geographic variation is the observation that organisms which are related or structuarlly similar are different because of differnces in the habitat and geography. Similar organisms seperated by geopraphy and global positioning depends on the location of the species a cline can occur. beal. . .but what is a cline?

17. What is different about the terms fitness and relative fitness? beal. . .good!

Fitness is the reproductive success according to a lifestyle which makes that particualr organism thrive. Relative fitness is the contribution of a genotype from the same lucs, meaning that the offspring will vary in genes and alleles in the in the future.

18. Why is it said that evolution acts on phenotypes and not genotypes? It is said that evolution acts on phenotypes and not genotypes becasue the enviroment can change the phenotype and not the genotype.

beal. . .evolution is said to act on the phenotype first because it is that phenotype that is selected to survive and reproduce (although it is the genes of an organism that control the phenotype). for example. . . female deer chose their males based on the size (phenotype) of their antlers!

19. Use the diagram below to differentiate between the modes of selection. beal. . . a bit of an explanation might be good here! a. directional selection b. disruptive selection c. stabilizing selection

20. Why does diploidy preserve genetic variation? It allows recessive traits to continue to exist. If both parents give a recessive trait, the trait will persist. Even if a heterozygote is born, the heterozygote has potential pass on the trait if matched another who is heterozygote or homozygous for the recessive trait.

beal. . .allows for different combinations found in offspring.

21. How does balancing natural selection relate to the term balanced polymorphism? Balancing natural selection occurs when natural selection keeps stable frequencies of phenotypic forms. This state is called balanced polymorphism.

Balanced natural selection is when stable frequencies of two or more phenotypic forms found in a population. Balanced polymorphism is the ability of natural selection to maintain diversity in a population. Therefore, they relate because they both are about diversity, and keeping the diversity, in the species found in a population

22. Define and give an example of the following: beal. . . good! a. Heterozygote advantage ​This is when heterozygotes having greater fitness levels than homozygotes. An example is that heterozygotes are more resistant to the severest effects of malaria. b. Frequency dependent selection ​This is the fitness of one morph declines because it is too common. When a type of moth becomes too common, jays learn to prey on it more quickly. c. Neutral variation ​ This is variation that has little to no impact of reproductive success. Half of the amino-acid changing mutations in Drosophilia have no selective effect. d. Sexual dimorphism ​ This is marked differences between sexes in secondary sex characteristics. An example is how males are generally the showier sex in a species. e. Intrasexual selection ​ This is selection within the same sex. An example is when a male monitors a group of females to make sure no other males express interest. f. Intersexual selection ​This type of selection is when individuals of one sex are picky in selecting mates. An example is how females select therir male based on the male's showiness.

23. What are the limitations to Natural Selection? ​ It is limited by historical constraints, adaptations are often compromises, chance and anatural selection interact, and it can only edit existing variations.

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