C2 Allele Frequency and Evolution Key Question: What Happens to the Frequency of an Allele in a Population Over Time?

INVESTIGATION C2

C2 Allele Frequency and Evolution Key Question: What happens to the frequency of an allele in a population over time?

This investigation teaches an advanced topic that builds GETTING STARTED on concepts explored in Investigations B5 through B8. Here, students learn to use a mathematical model used Time 150 minutes by scientists to track how alleles change over time in populations of the same species. They determine the Setup and Materials genome of a Crazy Creature and identify the alleles it 1. Make copies of investigation sheets for students. carries for two traits. Then they study those traits in two different populations of Crazy Creatures. Students will 2. Watch the equipment video. model how favorable alleles are passed on to offspring 3. Review all safety procedures with students. and how allele frequencies within one of the populations change over time. Finally, they compare the allele Materials for each group frequencies for the two traits in each population. yy Crazy Chromosomes set

Learning Goals Online Resources ✔✔Explain how changes in allele frequency over time are Available at curiosityplace.com an indication that evolution is occurring. yy Equipment Video: Crazy Chromosomes ✔✔Calculate allele frequencies for populations given the yy Skill and Practice Sheets frequency of homozygous recessive individuals. yy Whiteboard Resources ✔✔Evaluate the importance of genetic variation to yy Animation: Galapagos Finches the survival of a species when changes in the yy Science Content Video: Heredity environment occur. yy Student Reading: Traits

NGSS Connection This investigation builds conceptual understanding and skills for the following performance expectation. HS-LS4-3. Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.

Science and Engineering Practices Disciplinary Core Ideas Crosscutting Concepts

Analyzing and Interpreting Data LS4.B: Natural Selection Patterns LS4.C: Adaptation

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Vocabulary genes and traits, they discovered patterns of inheritance adaptation – an inherited characteristic that enhances that did not match Mendel’s results. This led to the an organism’s chance for survival in its current discovery of linked genes. Linked genes are found on environment the same chromosome pair and do not follow the law of independent assortment. allele frequency – a number that relates the occurrence of a particular allele for a gene within a population In linked genes, recombination can occur through a crossover – a physical exchange of chromosome process called crossover. In crossover, segments of DNA segments that most commonly occurs early in the first are exchanged between non-sister chromatids of division of meiosis homologous pairs. The diagram below shows how evolution – a change in the genetic makeup of a crossover can occur. The chance of crossover happening population over time is directly proportional to the distance of a gene from the centromere. The further from the centromere the gene is fitness – the ability of an organism to survive and reproduce to pass its genes on to the next generation located, the greater the chance of crossover occurring. If a test cross is performed using genes that are known to be genetic variation – the diversity of alleles in a population linked, and some of the offspring do not resemble either of organisms parent, we can deduce that crossover has occurred. Hardy-Weinberg formulas – mathematical relationships Because crossover does not happen in every line of that are used to calculate allele frequencies in a gametes, the ratios are different than the ratios in population of organisms non‑linked genes. Students will discover that usually, linked genes – genes that are found on the same most offspring resemble at least one parent and only a chromosome pair smaller number bear no resemblance to their parents.

mutation – a change in the hereditary material of Greater chance of an organism crossover natural selection – the process by which organisms with favorable adaptations survive and reproduce at a higher Lesser chance of rate than those with less-favorable adaptations crossover non-linked genes – genes that are found on different chromosome pairs and are inherited independently from Greater chance of each other crossover Crossover recombination – a mixing of alleles that occurs during meiosis A mutation is a change in the hereditary material of an organism. A mutation may lead to different alleles of a gene which, in turn, lead to variations of a trait. Mutated BACKGROUND alleles may cause favorable or unfavorable traits to surface. An adaptation is an inherited trait that helps an The law of independent assortment was derived from organism survive. Adaptations include body structures Gregor Mendel’s work with pea plant traits. Although he that help an organism feed, move around, and protect knew nothing about genes or chromosomes, Mendel itself. Adaptations are inherited; therefore, they must be deduced that there was a mixing force that caused carried on genes. Some mutations are harmful because alleles (he called them “factors”) to segregate into they cause genetic disorders. Mutations may also be different gametes independently of each other. It turns helpful because they contribute to genetic variation. out that Mendel’s data was collected from non-linked Genetic variation refers to the diversity of alleles in a genes: genes found on different chromosome pairs that population, and ensures that a population has a better segregate independently. But as other scientists studied chance of survival should the environment change.

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Imagine a population of brown squirrels that has The Hardy-Weinberg formulas can be used by scientists a single gene that determines fur color. A mutated to determine whether evolution has occurred. Using allele causes white fur instead of the usual brown fur. the equations, any changes in the allele frequencies The squirrels with brown fur can hide from predators in a population over time can be detected. An allele more easily than squirrels with white fur. Most of the frequency is a measure of the occurrence of a particular squirrels that survive to reproduce are brown. This allele of interest in a population. The Hardy-Weinberg example illustrates the process of natural selection. principle states that if no evolution is occurring, an Explain: Since brown fur is a favorable adaptation, the allele for equilibrium of allele frequencies will remain in effect boilerplate text brown fur is selected over the allele for white fur. In in each succeeding generation of sexually reproducing natural selection, organisms with favorable adaptations individuals. In order for equilibrium to remain in effect survive and reproduce. They pass favorable adaptations (or, in order to conclude that no evolution is occurring), on to offspring. Over many generations, the alleles for the following conditions must be met: favorable adaptations increase in the population. 1. No mutations can occur, so that new alleles do not enter the population. 2. No migration of individuals into, or out of, the population can occur. 3. Random mating must occur (individuals must pair by chance). 4. The population must be large.

Hardy-Weinberg Formulas

p + q = 1, where: p = frequency of the dominant allele in the population q = frequency of the recessive allele in the population

Fitness refers to the ability of an individual to survive, and reproduce, and contribute its alleles to the next generation in the population. The term "Darwinian p2 + 2pq + q2 = 1, where: fitness" is often used to distinguish this term from 2 physical fitness. Over generations, the alleles with higher p = frequency of homozygous dominant individuals fitness become more common in the population. 2pq = frequency of heterozygous individuals

Natural selection is the driving force behind evolution. In 2 evolution, the alleles of a population change over time q = frequency of homozygous recessive individuals as favorable phenotypes are selected over unfavorable Evaluate: phenotypes. Through evolution, the genetic makeup of boilerplate text the population changes over time. Eventually, evolution leads to the formation of new species from a common ancestor. The new species are genetically different from each other and they can no longer interbreed.

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5E LESSON PLAN

Engage Take your students outside into the schoolyard. Have them bring their notebooks. Ask students to find a single organism, either an animal or plant, and have them make a sketch of the organism or take a digital photo to print out and paste into their notebook later. Ask them to make a list of the characteristics of the organism. Science Content Video Animation Then ask them to identify three characteristics from Heredity Galapagos Finches their list and describe how those characteristics may be adaptations to the organism’s environment. For example, Elaborate a plant’s fuzzy leaves may help the plant trap moisture in The concept taught in this investigation, allele frequency, a dry environment. allows scientists to study genes at a population level. In previous investigations, students used Punnett squares Explore to study the genes of individuals. The development of the Hardy-Weinberg formulas was an important Complete Investigation C2, Allele Frequency and Evolution. milestone in the science of genetics and evolution. In this investigation, students apply what they have Before Hardy and Weinberg, it was thought that learned about genes, mutations, and the processes of dominant alleles must, over time, inevitably drive meiosis and fertilization, to studying the process of natural recessive alleles out of existence. This incorrect theory selection and evolution. They will study two fictional was called “genophagy” (literally “gene eating”). populations of organisms (Crazy Creatures) and compare According to this wrong idea, dominant alleles always allele frequencies using the Hardy-Weinberg formulas. increase in frequency from generation to generation. They will deduce whether evolution is occurring in one of Hardy and Weinberg were able to demonstrate with their the populations based on their data. equation that dominant alleles can just as easily decrease in frequency. Use this example to illustrate an important Explain idea about the process of science: that scientific ideas Revisit the Key Question to give students an opportunity change and evolve over time as new information is to reflect on their learning experience and verbalize acquired. understandings about the science concepts explored in the investigation. Curiosityplace.com resources, including Evaluate student readings, videos, animations, and whiteboard yy During the investigation, use the checkpoint resources, as well as readings from your current questions as opportunities for ongoing assessment. science textbook, are other tools to facilitate student yy After completing the investigation, have students communication about new ideas. answer the assessment questions on the Evaluate student sheet to check understanding of the concepts presented.

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Name ______Date ______Table 1: Creature genome

Allele on Allele on C2 Allele Frequency and Evolution Materials: Gene color Trait chromosome 1 chromosome 2 Genotype for trait Phenotype for trait ✔ Crazy Chromosomes set of the pair of the pair What happens to the frequency of an allele in a population over time? ✔ Allele coins Chromosome pair #1 Evolution is a change in the genetic makeup of a population over time, driven Black Skin Color by a process called natural selection. All organisms compete for limited resources such as food and shelter. TT TT red In natural selection, individuals with favorable phenotype variations will be more likely to survive and pass Light Purple Leg t t tt long the alleles for those phenotype variations on to their offspring. Eventually, the favorable phenotype becomes prevalent in the population. Imagine a population of Crazy Creatures that lives on the mainland where there Light blue Foot T t Tt webbed are plenty of food sources. This is the original population. A huge storm carries some of that population to a White Arms secluded island called Walnut Island. The only food source for this population is rock hard walnuts that fall t T Tt long out of the trees. Will certain phenotypes be more favorable than others in this new environment? One hundred Red Hands t t tt claws years later, how might we determine if evolution is occurring in the new population? Chromosome pair #2  Determining the genome of a creature in the original population Yellow Eye color t T Tt red/green Let’s start the investigation by studying the original population of Crazy Creatures that existed before the Dark Purple Eyebrows TT TT unibrow storm. Working by yourself, you will randomly determine the genome of an individual in the population. Orange Beak TT TT trumpet Follow the steps below to determine your creature’s genome. Gray Ears t t tt mouse 1. Take out the small plastic bag with the coins in it. You will need to share these coins with other members of your group since everyone is going to flip for their own creature. Green Antenna length T t Tt long

a. Find the blue coin that has a T on one side and a t on the other. Use this coin to flip for the first Dark Blue Antenna shape t T Tt knob chromosome in each pair. Find the green coin with a T on one side and a t on the other. Use this coin to Yellow-green Tail t t tt none flip for alleles on the second chromosome in each pair. We won’t worry about the sex of our creatures for this investigation, and will focus only on genes that code for other traits. Pink Wings TT TT none 2. The first trait you will flip for is skin color. Flip the blue coin and record the result in Table 1 in the skin color row. Flip the green coin and record the result in the skin color row as well. Pass the coins around in your group so everyone has a chance to flip for the trait. 3. Record the genotype for your creature’s skin color in the genotype column. An organism’s genotype is the set of alleles for a particular gene found in the organism’s genome. To record the genotype, simply write the letters in columns 2 and 3. In genetics, the capital letter is always written first, regardless of which chromosome it is located on. For example, if you recorded a t in column 2 and a T in column 3, the genotype for that trait would be Tt. 4. Flip the coins for the rest of the traits. Record the alleles on each chromosome in each pair as well as the genotypes for all of the traits. Share the coins with other members of your group so everyone can determine the genotypes for their creatures. 5. Use Table 2 to decode your creature’s genome and fill in the phenotype column of Table 1 for each trait.

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 Determining the genome of a creature in the original population If students have completed Investigation B1, they will be familiar with the process of flipping coins to determine the genotype and phenotype of a Crazy Creature. You may have them use their data from that investigation. Unlike in earlier investigations, each individual student should flip for his or her own creature for this investigation. This is because we want a larger starting population for the rest of the investigation. Students flip the allele coins that come with the Crazy Chromosomes set and take turns using them. Alternatively, you can have them use regular coins, with heads representing the dominant allele and tails representing the recessive allele.

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Explore INVESTIGATION C2 Explore INVESTIGATION C2 Table 2: Genotypes and phenotypes for Crazy Creatures  Calculating allele frequencies using the Hardy-Weinberg formulas Trait Genotypes and phenotypes To determine if evolution is occurring, we can start by determining the allele frequencies for alleles in the 1. Sex XX – female XY – male original population, then comparing those frequencies with the population on Walnut Island today (100 years after the storm that carried them there). If there are differences in the allele frequencies, we will have evidence 2. Skin color TT – red Tt – purple tt – blue that favorable phenotypes are being selected by the environment (i.e., natural selection is occurring). The Hardy-Weinberg formulas can be used by scientists to determine whether evolution has occurred. Using 3. Leg TT – short Tt – short tt – long the equations, any changes in the allele frequencies in a population over time can be detected. The law states that if no evolution is occurring, then equilibrium of allele frequencies will remain in effect in each succeeding 4. Foot TT – webbed Tt – webbed tt – talon generation of sexually reproducing individuals. In order for equilibrium to remain in effect (or, in order to 5. Arms TT – long Tt – long tt – short conclude that no evolution is occurring), the following conditions must be met: 1. No mutations can occur, so that new alleles do not enter the population. 6. Hands TT – paws Tt – paws tt – claws 2. No migration of individuals into, or out of, the population can occur. 7. Eye color TT – red Tt – one red and one green tt - green 3. Random mating must occur (individuals must pair by chance). 8. Eyebrows TT – unibrow Tt – unibrow tt – separate 4. The population must be large. 9. Beak TT – trumpet Tt – trumpet tt – crusher

10. Ears TT – elephant Tt – elephant tt – mouse Obviously, all of these conditions cannot be met in real-life situations. But we can use the formulas to take a “snapshot” of the allele frequency for a gene in a population. By comparing the allele frequencies of the 11. Antenna length TT – long Tt – long tt – short original population and the present-day Walnut Island population, we can determine whether evolution is occurring on the island. If there is a difference in the allele frequency between the two populations, then all 12. Antenna shape TT – knob Tt – knob tt – star of the Hardy-Weinberg conditions have not been met, and evolution may be occurring on the island. If the two frequencies are the same, then we can hypothesize that evolution is not occurring. 13. Tail TT – long Tt – short tt – none There are two Hardy-Weinberg formulas. 14. Wings TT – no wings Tt – no wings tt – wings Hardy-Weinberg Formulas

p + q = 1, where: p = frequency of the dominant allele in the population q = frequency of the recessive allele in the population

and

p2 + 2pq + q2 = 1, where: p2 = frequency of homozygous dominant individuals 2pq = frequency of heterozygous individuals q2 = frequency of homozygous recessive individuals

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SCIENCE AND MATH Go through the example in Part 2 of the investigation as a class to make sure students have a grasp of how Using the Hardy-Weinberg formulas If your to use these formulas. If they are having trouble, they students are good with algebra, they will quickly will need practice before continuing. Here is another understand the Hardy-Weinberg formulas. These example to use in addition to the one presented in the formulas are called “equilibrium formulas” because all investigation. of the variables add up to 1. In this equation (p² + 2pq Within a population of moths, brown color (B) is + q² = 1), p is defined as the frequency of the dominant dominant to white color (b). If 30% of the population is allele and q as the frequency of the recessive allele for white, what is the frequency of homozygous dominant a trait controlled by a pair of alleles (T and t). In other and heterozygous individuals in the population? words, p equals all of the alleles in individuals who are homozygous dominant (TT) and half of the alleles bb== q2 0.30 in individuals who are heterozygous (Tt) for this trait q ==0.30 0.55 in a population. Likewise, q equals all of the alleles in individuals who are homozygous recessive (tt) and p =−1 0.55= 0.45 the other half of the alleles in individuals who are 2 p2 ==0.45 0.20= BB heterozygous (Tt). () 22pq ==(0.45)(0.55) 0.50= Bb q ==0.30 bb 150

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Here is an example of how to use the Hardy-Weinberg formulas. So, if an individual has claws, we know that its genotype is hh. Similarly, if the individual has a crusher beak, we know its genotype is bb. Follow the steps below to calculate the allele frequencies for the hand and beak You have sampled a population in which you know the frequency of individuals out of the total population genes for the class population. is 0.24 (which is equal to 24%) homozygous recessive for a trait (tt). Use the Hardy-Weinberg formulas to calculate the frequency of the T and t alleles in this population. Then find the frequency of each possible 1. Your teacher will guide the class in filling out Table 3. Use this data to calculate the allele frequencies genotype (TT, Tt, tt). for the hand and beak genes. The allele frequencies are equal to the number of creatures with the allele divided by the total number of creatures in the population. 1. What do you know? The value of q2 = the frequency of the population that is tt (0.24). 2. Use the Hardy-Weinberg formulas to calculate the frequency of the alleles of each gene and record the 2. What do you want to find out? The allele frequencies of T and t in the population, and the frequencies frequencies in the last two columns of Table 3. of each possible genotype (TT, Tt, and tt). Table 3: Frequency of homozygous recessives in original population 3. Formulas to use: p + q = 1 and p2 + 2pq + q2 = 1

4. Solution: Number of Frequency of Frequency of Frequency of Trait homozygous recessive homozygous recessive recessive allele dominant allele 2 To find the frequency of t, simply take the square root of 0.24, since q = tt: individuals individuals (h or b) (H or B) Total 0.24= 0.49 Population 24 24 Hands Since p + q = 1 and we now know the value of q, we can calculate p using this relationship: 3 0.13 0.36 0.64 Beak 5 0.21 0.46 0.54 p + 0.49 = 1 p = 1 – 0.49 = 0.51 Since p2 + 2pq + q2 = 1, and we know the values of p and q, we can easily determine the frequencies of  Modeling reproduction on Walnut Island each genotype in this population. The storm blew a random sample of the mainland population to Walnut Island. In this part of the investigation, p = 0.51 and q = 0.49, so: we will model reproduction in the P1 generation to produce the F1 offspring. 2 Frequency of TT = (0.51) = 0.26 1. Randomly choose the genome of the creature in your group that you choose to be a parent. You can do Frequency of Tt = 2(0.51)(0.49) = 0.50 this by choosing the creature made by the person with the earliest birthday in a calendar year.

Frequency of tt we already know is 0.24 2. Build a diploid set of chromosomes for the chosen creature. To check your work, add the values to make sure they add up to 1: (0.26) + (0.50) + (0.24) = 1 3. Take the chromosomes through the process of meiosis to produce gametes. First, build a sister chromatid for each chromosome in the homologous pair and attach the sister chromatids together with a centromere.  Calculating allele frequencies in the original population Now, let’s think about recombination. Will recombination occur during meiosis? Locate the hand and beak genes on your chromosomes. Since they are found on separate chromosome pairs, they are non-linked genes We will study the genes for hands and beak in Crazy Creatures because we know that both traits follow the law and will segregate independently into gametes. Recombination can also occur in the form of crossover on of dominance. For the purpose of our study, let’s use new letters as symbols for each trait. linked genes. The hand gene is located farthest from the centromere, so crossover is a possibility with the first For hands, let H = paws and h = claws chromosome pair. But the beak gene, located close to the centromere, is an unlikely candidate for crossover. For the purpose of this investigation, we will assume that crossover will not occur in the beak gene. For beak, let B = trumpet and b = crusher 4. With that information, model crossover with the hand gene, then separate homologous pairs for the first division.

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 Calculating allele frequencies in the  Modeling reproduction on original population Walnut Island To increase your study population, you may wish to This part of the investigation assumes that students complete parts 1 and 2 of the investigation on the have a solid understanding of meiosis and the first day and spend some time working through recombination forces that occur during meiosis. If your Hardy-Weinberg calculations. Then, collect data from students have not been exposed to these concepts all of your classes and give it to the students on the before, be sure they complete investigations B5 second day to complete the rest of the investigation. through B8 prior to this investigation. If they do have Larger populations in this investigation yield better a good understanding, you may need to review the results from the activities. Work with the entire class to processes of independent assortment and crossover complete Table 3. with them. Work with the students as a class to make their gametes for Part 4; then they will be able to make them on their own for Part 5, where they will have to model the process two more times.

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Explore INVESTIGATION C2 Explore INVESTIGATION C2 5. Next, separate sister chromatids at the centromere to form your gametes.  Modeling two more generations 6. Place your gametes into separate plastic bags, then put those bags into a paper bag. Mix them up and pull In genetic variation, the alleles of organisms within a population can change through natural selection. a gamete out of the bag. Natural selection is the process by which organisms with favorable adaptations survive and reproduce at 7. Place your gametes next to the gametes of the group to which you were assigned. a higher rate than do those with less-favorable adaptations. Genetic variation is important to the process of 8. Fill in the genotype and phenotype of the offspring for Trial 1 in Table 4. Be sure to use H/h for hands natural selection. Variations in alleles and phenotypes caused by mutations and recombination happen by and B/b for beak instead of T/t. chance, but the process of natural selection is influenced by the environment. To model the influence of the environment, follow the steps below to produce the F2 and F3 generations. 9. Return the gametes to their original paper bags, mix them up, and repeat steps 6 through 8 for a total of 10 trials. 1. Choose the creature from Table 4 that has the highest fitness value.

10. Fill in the last column of Table 4 with a value for fitness. The term fitness refers to the ability of an 2. Build that creature’s diploid set of chromosomes. organism to survive and reproduce. In our system, a fitness of 10 means the greatest chance of surviving to reproduce and 1 means the smallest chance. Use the following key as your guide to assigning values: 3. Follow steps 3 through 7 of Part 4 to produce the F1 creature’s gametes. claws and crusher beak = 10 4. Follow steps 8 through 10 of Part 4 to complete Table 5 for the F2 generation. claws and trumpet beak = 7 5. Follow steps 1 through 4 above to complete Table 6 for the F3 generation. paws and crusher beak = 5 paws and trumpet beak = 1 Table 5: F2 generation on Walnut Island

Table 4: F1 generation on Walnut Island Genotype for Phenotype for Phenotype for Trial Genotype for beak Fitnessvalue hands hands beak Genotype for Phenotype for Phenotype for Trial Genotype for beak Fitnessvalue hands hands beak 1 Hh paws Bb trumpet 1 1 Hh paws BB trumpet 1 2 hh claws Bb trumpet 7 2 Hh paws Bb trumpet 1 3 hh claws BB trumpet 7 3 hh claws Bb trumpet 7 4 hh claws bb crusher 10 4 Hh paws bb crusher 5 5 Hh paws bb crusher 5 5 Hh paws Bb trumpet 1 6 Hh paws bb crusher 5 6 HH paws BB trumpet 1 7 HH paws BB trumpet 1 7 Hh paws Bb trumpet 1 8 hh claws Bb trumpet 7 8 HH paws bb crusher 5 9 hh claws bb crusher 10 9 hh claws Bb trumpet 7 10 Hh paws Bb trumpet 1 10 Hh paws bb crusher 5

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STEM CONNECTION cause death. In addition, the malarial parasite cannot survive in the blood of heterozygous individuals. A real-life Hardy-Weinberg problem Sickle-cell Have your students solve this problem using the anemia is a well-studied genetic disease to discuss Hardy-Weinberg formulas: with your students. It also acts as a good example of Suppose 11% of a population is born with sickle-cell why it is advantageous to carry alleles for a genetic anemia. What percentage of the population would be disorder in a population. In sickle-cell anemia, being resistant to malaria? normal is dominant (S) to having the disease (s). 2 Homozygous dominant individuals (SS) are easily q ==0.11 ss infected with the parasite carried by mosquitoes q ==0.11 0.33 that causes malaria. Eventually, individuals infected with malaria will become sick and perhaps die. p =−1 0.33= 0.67 Homozygous recessive individuals (ss) have red blood 2 p2 ==0.67 0.45 = SS cells that are “sickle” shaped and cannot properly carry () oxygen. These individuals often die at a younger age. 22pq ==()0.67() 0.33 0.44 = Ss However, individuals who are heterozygous (Ss) have some sickle-shaped blood cells, but not enough to In this example, 44% of the population would be heterozygous and resistant to malaria.

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Table 6: F3 generation on Walnut Island a. How do the allele frequencies compare between the original population and the population on Walnut Island? Genotype for Phenotype for Phenotype for Trial Genotype for beak Fitnessvalue hands hands beak The frequency of the recessive allele for both genes increased, while 1 hh claws Bb trumpet 7 the frequency of the dominant allele for both genes decreased.

2 hh claws bb crusher 10 b. Does this data provide evidence that evolution is occurring on Walnut Island? Use evidence from your data to argue your explanation. 3 hh claws bb crusher 10 Yes. Since the only food source on Walnut Island is walnuts, 4 Hh paws bb crusher 5 having claws is favorable to having paws. Also, having a crusher 5 Hh paws Bb trumpet 1 beak is favorable to having a trumpet beak. Both phenotypes are 6 Hh paws Bb trumpet 1 recessive and the data shows that the frequency of the recessive 7 hh claws bb crusher 10 allele for both genes is much higher than it was in the original 8 hh claws Bb trumpet 7 population. 9 Hh paws bb crusher 5 c. If the dominant allele completely disappeared for both traits in the Walnut Island population, would that 10 hh claws bb crusher 10 be a good or a bad thing? Explain your answer. It would be a bad thing, because genetic variation is important to  Analyzing the data the survival of a population. If the environment changed somehow, Now, 100 years after the storm, we are studying the F3 generation on Walnut Island. Our population consists of all of the individuals in Table 6 for the entire class. Your teacher will help you fill out columns 3 and 4 genetic variation would allow for other phenotypes that could be of Table 7. Using that information, calculate the allele frequencies for hands and beak in the Walnut Island population. Then, transfer the allele frequencies for the original population from Table 3 into Table 7. better adaptations to the new environment. Table 7: Allele frequencies for Walnut Island d. Look at the phenotypes of your original creature in Table 1. Does it have any other phenotypes that you Number of Frequency of Frequency of recessive Frequency of think would be favorable for the Walnut Island habitat? Choose one phenotype and describe why it would Trait homozygous recessive homozygous recessive allele dominant allele be favorable. What would you expect to happen to the allele frequency for that allele if your creature individuals individuals (h or b) (H or B) ended up on Walnut Island? Total population 40 My creature has long arms, which would be a good adaptation for Hands 18 0.45 0.67 0.33 picking walnuts off of the trees if there are none on the ground. Beak 16 0.40 0.63 0.37 Long arms are dominant to short arms so I would expect the allele Allele frequencies of the Walnut Island Allele frequencies of the original population population frequency for T to increase on Walnut Island and the allele for t Trait Recessive allele Dominant allele Recessive allele Dominant allele (short legs) to decrease over time. (h or b) (H or B) (h or b) (H or B) Hands 0.36 0.64 0.67 0.33 Beak 0.46 0.54 0.63 0.37

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 Analyzing the data You may want to collect data from all of your classes prior to completing Part 6, especially if you used that larger data set earlier in the investigation. Work with the entire class to complete the numbers in the top rows of Table 7. Then, have students compile the numbers in the bottom rows for comparison.

You may wish to use this opportunity to have students create bar graphs of the allele frequencies for comparison. This is a good visual way to compare the data.

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Notes and Reflections Evaluate INVESTIGATION C2

Name ______Date ______

1. What is evolution? Evolution is the change in the genetic makeup of a population over time.

2. How are the Hardy-Weinberg formulas used by scientists to determine if evolution is occurring? We can measure a change in the frequency of an allele between two separate populations to determine if the frequencies have changed between the two. If they have changed, then we can hypothesize that evolution is occurring.

3. What is natural selection and how is it related to evolution? Natural selection is the process by which organisms with favorable phenotypes are able to reproduce and pass the alleles for those phenotypes on to offspring. Natural selection is the driving force behind evolution.

4. What is meant by the term fitness, from an evolutionary point of view? Fitness measures the ability of an individual to survive, reproduce, and pass its alleles on to future generations.

5. In a population of 100 Crazy Creatures, 17 individuals have the star antenna shape, which is recessive to having a knob-shaped antenna. Calculate the allele frequency of the dominant and recessive alleles. Then, calculate the frequencies of homozygous dominant, heterozygous, and homozygous recessive individuals.

Question tt5 =÷answer17 100= 0.17 WRAPPING UP t== 0.17 0.41 T=+p 0.41= 1 Have students reflect on what they learned from p = 0.59 the investigation by answering the following question: pp22++21qq= TT ==p220.59= 0.35 We know it is important to study the evolution of genes at an individual level. Why is it also important Tt ==22pq (0.59)(0.41)= 0.48 to study the evolution of a species at the population tt = 0.17 level?

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