Period+2+GR+23


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

1. Define the following terms: 0 a. Microevolution- Evolutionary change below the species level: change in 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? Frequencies of alleles and genotypes in a populations remain constant from generation to genration only. Only mendelian segregation and recombination of alleles are at work. If a population is not in hardy equilibrium evolution occurs. It is impossible for it to be in H.W.E.

beal. . but what about: 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!

Hardy-Weinberg equilibrium is the condition describing a non-evolving population.The 5 conditions must be met in order for the allele and genotype frequencies to remain constant from generation to generation.

4. Use the blank diagram below to relate the H-W equation to a Punnett square. -Mr. Beal, you told Alyssa and I that if we couldnt figure out a way to upload this to leave you a message, so here it is!

beal. . . cool. ..

5. What are the five conditions for H-W equilibrium to maintained? The five conditions are: 1. a very large population size 2. no migration 3. no net mutations 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? beal. . . good!

It can be used to find the estimated number of people who are carriers of a genetic disease.

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

Mutation and sexual recombination.

8. What is the impact of the following: a. Point mutation- Usually harmless, but can be significant i.e. sickle-cell anemia beal. . . a change in a gene at a single nucleotide pair!

b. Gene duplication- Usually always harmful if it is in big segments, but in smaller segments it could be helpful, but it is very rare. beal. . . why. . . how?

c. Sexual recombination- Very important for evolution, and most genetic changes occur because of this. beal. . . but what is it?

9. What is the relationship between mutation rates and generation span? Mutation rates are low in animals and plants, about one in every 100,000 genes per generation. In microorganisms and viruses with short generation spans, mutations can rapidly generate genetic variation. beal. . .good!

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

b. Bottleneck effect- a sudden change in the environment, such as fire or flood, drastically reduces the size of a population. The survivors pass through a restrictive "bottleneck" and their gene pool may no longer be reflective of the original populations gene pool.

c. Founder effect- a few individuals become isolated from a larger population, the smaller group may establish a new population whose gene pool is not reflective of the source population.

d. Gene flow- genetic additions to or subtractions from a population resulting from movement of fertile individuals or gametes.

11. Why would we discuss adaptive evolution and what role does natural selection play? beal. . .good! A daptive evolution is when organisms adapt or adjust to their surrounding environment over time. We discuss this with natural selection because chooses the traits that help organisms better survive. Natural selection is what causes evolutionary adaptation.

12. Give examples of phenotypical variation that is not inheritable.
 * Examples include changes in muscle mass because of body building, changes in features because of plastic surgery, changes in hair color because of chemical dyes. **


 * Beal. . . your examples are Lamarkian and not Darwinian. The below is more correct and found in the text book. **

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. beal. . .good! ** 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 is 1 or 2 more distinct alleles at a given locus in a population's gene pool. An example is height. **

14. How do we measure genetic variation? beal. . .good! **By determining the amount of heterozygosity at both the level of whole genes (gene variability) and at the molecular level (nucleotide variability).**

15. How can very small differences in nucleotide sequences lead to such diversity in the human population? Nucleotide sequences are crutial for identification of an organsim. A small change in one sequence can alter every generation after that specific mutation. The orgigonal organism starting off with the change is still a part of the population, however, as that particular nucleotide sequence is spread throughout a population, it becomes a new species. So within the human population, it would bring about diversity among the differenty triats humans possess.

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? beal. . .good!

Geographic variation is the observation that organisms which are related/strucutrally simiar are different because of differencesi n the habitat and geography. Similar organisms separated by geography and global positioning. Depending on the location of the species a cline can occure. For example, birds in north America tend to be larger as the latitude increases to the north. beal. . .but what is a cline?



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

Fitness is reproductive success acording to a life style which makes that particular organism thrive. Relative fitness is the contribution of a genotype from the same lucs. This means that offspring will vary in genes and alles 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 enviornment can change the phenotype. For example: If you take a flamingo and place it in a different environment and change its food you will see a change in the color of its feathers. The color of its feathers will fade away from a bright pink to a faded pink.

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. ​ ​In this diagram, it is showing us the different types of selections and the divisons in populations. In the top diagram it is showing a normal bell curve where the extreme's, light and dark deer mice, are at a lower level when the medium is at a higher level. The three bottom diagrams are explaining three different things that can happen to a population. First, there is evolved population where the average darkness changes while the species evolves, making the medium more to one extreme. Then you have disruptive evolution where the higher number of mice were at the extreme's with a break in the middle. Finally, there is stabalizing seletion which narrows the extreme variants and leaves little variation in the species.

beal. . . what are the selection types?

20. Why does diploidy preserve genetic variation? Diploidy, the quality of being diploid, preserves genetic variation because the cells have two chromosomes and therefore two copies of genes. When they reproduce, their offspring can have a combination of genes from their parents that differ.

beal. . .good!

21. How does balancing natural selection relate to the term balanced polymorphism? beal. . .good. 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 - The greater reproductive success of a heterzygou individual compared to the homozygous individuals. This tends to preserve gene pools since each allele is kept.

b. Frequency dependent selection - A decline in the reproductive success of a morph which is a result from the morph's phenotype becoming too common in a population's gene pool.

c. Neutral variation - Genetic diversity that confirms no apparent selective advantage.

d. Sexual dimorphism - A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females.

e. Intrasexual selection - A direct competition among individuals of one sex for mates of the opposite sex. This is most common among males.

f. Intersexual selection - Selection in which individuals of one sex choose their mates by their traits.

23. What are the limitations to Natural Selection Natural Selection is limited by the environment, if the animal is well suited for its environment- it has no need to adapt.

beal. . . []