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Page 1 of 46 Name: Class: Unit 7
Evolution Solution Topics/ Daily Outline:
Day A B Content: Text CW #: HW #: 1 3.29 3.30 Variation 16.3, 17.1 1, 2 1
2 3.31 4.3 Natural Selection, Rainfall and Bird Beaks 17.1 17.2 3, 4 -- 3 4.4 4.5 Speciation 17.3 5, 6 2
4 4.6 4.7 Allele Frequency 17.1 7, 8 -- 5 4.18 4.19 Project -- -- --
6 4.20 4.21 Project -- -- 3
7 4.24 4.25 Mutation and Selection 17.2 9 4 8 4.26 4.27 Evidence of Evolution 16.4 10 Review
9 4.28 5.1 Unit Test, Unit Packet Collected -- -- --
http://www.srhsbio.wikispaces.com If you are absent, please use this sheet to determine what you missed and collect the materials from the make-up work bins up front. Get help from a friend, the links above, or the instructor.
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Scientific Theory
Definition:
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Adaptation
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Speciation
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LINCs
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Natural selection
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Artificial selection
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Allele (Gene) Frequency
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Analogous Structures
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Vestigial Structures
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Homologous Structures
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CW 1: Just a Theory
The word theory, unfortunately, is misused in everyday language. Link: http://www.youtube.com/watch?v=gklQ3GbmufI
1. What is the difference between a theory and a scientific theory?
2. Why is the phrase “evolution is just a theory” incorrect?
3. Can a scientific theory be changed?
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CW 2: Feeding the Birds - Beak Variation Lab
Problem: Which bird has the best beak adapted for gathering food? (Spoon-billed Sparrow, Fork-billed Sparrow, or Tweezer-billed Sparrow) Variables: Independent:
Dependent:
Constants:
Hypothesis: Materials:
Spoons (Spoon Billed Sparrow)
Forks (Fork Billed Sparrow)
Tweezers (Tweezer Billed Sparrow)
Sunflower/ bead mix Cup (bird nest) Stopwatch Procedures:
1. Design a data table to record the mass of food each type of bird food gathered. 2. Use your bill to gather as much food as you can in the time allotted. Place the food you
gather into your nest. You may only use your bill to pick up the food and your nest needs to stay flat on the lab bench.
3. Count the number of the bird food collected by each type of bill and record your data in the data table you have created.
4. Graph your data.
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Data Table: Graph:
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Analysis and Conclusion Questions: 1. What can you conclude about the relationship between the independent and
dependent variables?
2. All the birds in this experiment were the same species, the Billed Sparrow. What variations were present within this species?
3. Over time, a small variation in a species can lead to an adaptation. An adaptation is a trait which helps an organism to survive in its environment. Which adaptation(s) are best suited each food source below?
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4. In the forest where the Billed Sparrow lives, a fungus kills off all the plants that produce large seeds.
a. Which variation(s) will allow the Billed Sparrow species to survive?
b. How will the population of Billed Sparrows change after 100 years, assuming the large seed plants do not grow back?
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CW 3: NOTES: Natural Selection in a Nutshell
Main Ideas Notes 1. There is
variation in traits
2. There is differential reproduction
3. There is heredity
4. End Result
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CW 4: Rainfall and Bird Beaks Gizmo
Vocabulary: adaptation, beak depth, directional selection, drought, evolution, natural selection, range, stabilizing selection Prior Knowledge Questions (Do these BEFORE using the Gizmo.) During the voyage of the HMS Beagle (1831–1836), the young Charles Darwin collected several species of finches from the Galápagos Islands. Two of Darwin’s finches are shown below.
1. Which species do you think is best adapted to a diet of small, delicate seeds? Explain why you think so. _____________________________________________________________________ _____________________________________________________________________
2. Which species do you think is best adapted to a diet of large, tough-to-crack seeds?
Explain. _____________________________________________________________________ _____________________________________________________________________
Gizmo Warm-up Darwin’s finches are one of many types of animals on the Galápagos Islands that have unique adaptations, or traits that help an organism survive in its environment. The Rainfall and Bird Beaks Gizmo™ allows you to explore how rainfall influences the range of beak shapes found in a single finch species. 1. The beak depth of a finch is the distance from the top of the beak to the bottom, as shown.
A. What is the current average beak depth in the Gizmo? ____________________________________ B. Select the HISTOGRAM tab. Do all the finches have the same beak depth? ____________________
2. Click Play ( ) and let the simulation play for five years with average rainfall (5 inches/yr). Select the
GRAPH tab and view the Finches vs time and Beak depth vs time graphs.
A. How does the finch population change? ________________________________________________
B. Does the beak depth change significantly? ______________________________________________
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Activity A: Normal years
Get the Gizmo ready:
Click Reset ( ).
Introduction: The Galápagos Islands are very dry, with an average rainfall on some islands of only five inches per year. The amount of rainfall has a large impact on the abundance and types of seeds that are available to be eaten by finches. In the process of natural selection, only the finches that are best adapted to the available seed types survive and have offspring. Question: How is the finch population affected by a period of average rainfall? 1. Observe: With the Rain sliders set to 5 inches, click Play, and then Pause ( ) after one year has passed.
Select the TABLE tab and look at the Month and Finches columns.
A. How did the finch population change over the course of one year? __________________________ _________________________________________________________________________________
B. The finches have their young during the rainy season. Based on the table, which part of the year do
you think is the rainy season? ________________________________________________________
2. Analyze: Click Reset, and choose the HISTOGRAM tab. The bars represent the numbers of finches that have different beak depths. The range of beak depths is equal to the difference between the largest and smallest beaks.
A. What is the average beak depth of the current finch population? ____________________________ B. What is the range in beak depths in the population? ______________________________________
C. Do most of the finches have beak depths near the lower extreme, the middle, or the higher
extreme of the range? ______________________________________________________________
3. Experiment: Click Play, and observe the histogram as the simulation plays for five years.
A. What is the average beak depth now? _________________________________________________ B. What is the current range of beak depths? ______________________________________________
C. Based on what you have seen, are finches with very small, medium, or very large beaks most likely to survive in times of normal rainfall? Justify your answer.
_________________________________________________________________________________
_________________________________________________________________________________
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Activity B: Drought
Get the Gizmo ready:
Click Reset.
Introduction: In years of extreme drought, Galápagos plants don’t produce new seeds. The small, delicate seeds get eaten up quickly, leaving behind only the largest, toughest seeds. Question: How does drought affect the finch population and average beak depth? 1. Form hypothesis: What type of beak do you think will be best for finding food in a drought?
_______________________________________________________________________________________ 2. Predict: Select the HISTOGRAM tab. On the left side below, sketch the current histogram and list the
average beak depth and range of beak depths. On the right side, sketch what you think the histogram will look like after five years of drought. Explain your prediction.
Initial beak depths Beak depths after 5 years (predicted)
Initial number of finches: ___________ Explanation: ________________________ Initial average depth: _________ ___________________________________ Initial range of beak depths: _________ ___________________________________
3. Experiment: Use the sliders to set the Rain to one inch for each of the five years in the simulation. Click
Play, and wait for five years. Observe the beak of the finch.
A. How does the beak depth change over time? ____________________________________________ B. What is the final average beak depth? _________________________________________________
C. What is the final range of beak depths? ________________________________________________
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4. Describe: Compare the final histogram to the initial histogram. How have the finches been affected by drought? Describe at least two changes that you notice.
_______________________________________________________________________________________
_______________________________________________________________________________________
5. Analyze: Was the increase in the average beak depth caused by an increase in large-beaked finches or a
decline in small-beaked finches? Explain your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________ 6. Draw conclusions: What do you think caused the changes in the finch population and average beak size
during the drought? _______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
7. Interpret: Directional selection occurs when individuals at one end of a range are more likely to survive
than intermediate individuals or individuals at the opposite end of the range. Stabilizing selection occurs when intermediate individuals are the most likely to survive.
Is directional selection, stabilizing selection, or both operating in this example? Explain.
_______________________________________________________________________________________
_______________________________________________________________________________________ _______________________________________________________________________________________
8. Think and discuss: Evolution is the process by which populations of organisms can change over time. How
is directional selection related to evolution?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
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Activity C: Rainy days
Get the Gizmo ready:
Click Reset.
Introduction: In years of abundant rainfall, there can be up to 10 inches (25 cm) of rain. In these years, plants produce an enormous number and variety of seeds. Question: How does plentiful rainfall affect the finch population and average beak depth? 1. Form hypothesis: What beak shape do you think will be best for finding food in a period of abundant
rainfall? ________________________________________________________________________________
2. Predict: Select the HISTOGRAM tab. On the left side, sketch the current histogram and list the average beak depth and range of beak depths. On the right side, sketch what you think the histogram will look like after five years of abundant rain. Explain your prediction.
Initial beak depths Beak depths after 5 years (predicted)
Initial number of finches: ___________ Explanation: ________________________ Initial average depth: _________ ___________________________________ Initial range of beak depths: _________ ___________________________________
3. Experiment: Click Reset. Use the sliders to set the Rain to 10 inches for each of the five years in the simulation. Click Play, and wait for five years. Observe the beak of the finch.
A. How does the beak depth change over time? ____________________________________________ B. What is the final average beak depth? _________________________________________________
C. What is the final range of beak depths? ________________________________________________
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4. Describe: Compare the final histogram to the initial histogram. How have the finches been affected by abundant rain? Describe at least two changes that you notice.
_______________________________________________________________________________________
_______________________________________________________________________________________
5. Analyze: Was the decrease in the average beak depth caused by an increase in small-beaked finches or a decline in large-beaked finches? Explain your answer.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
6. Draw conclusions: What do you think caused the changes in finch population and average beak size during
the period of abundant rain?
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________ 7. Extend your thinking: Most scientists think that a small group of finches colonized the Galápagos Islands
thousands of years ago. They would have been the only seed-eating birds on the islands. Suppose one island was very dry and another had plentiful rainfall.
A. How would the finch populations on these islands change over time? ________________________
_________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________
B. What might happen to the finch populations after millions of years? _________________________
_________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________
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CW 5: Speciation: An Illustrated Introduction
Link: http://www.youtube.com/watch?v=8yvEDqrc3XE
1. How many bird species are there on the planet?
2. What is a species?
3. How did the mainland bird first colonize the volcanic island?
4. After how many generations were the mainland and island birds no longer able to mate?
5. In reality, bird blind dating does not occur. How do scientists classify species separated in space as different species?
6. What factors led to evolution of the three island bird species?
7. How did the eastern and western birds differ after 10,000 generations?
8. The western females still mated with eastern males after 10,000 generations, but the eggs were not viable. Are the two types of bird different species?
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CW 6: Species Story
Write definitions for the following words:
1. Selection Pressures:
2. Bottleneck Effect:
3. Founder Effect:
4. Geological Isolation:
5. Behavioral Isolation:
6. Temporal Isolation:
You must write a story about a population of animals which eventually evolves into two or more different species. You must use at least three of the factors above in your story. Each major event in your story must:
Be illustrated WITH COLORS!
Explain how the factors (from above) led to speciation
Have the factor underlined During the course of your story anything can happen – a species may go extinct, start a war with another species, two star-crossed lovers may perish knowing that they can never produce fertile offspring… BE CREATIVE
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CW 7: Breeding Bunnies
Introduction: In this activity, you will examine natural selection in a small population of wild rabbits.
Evolution, on a genetic level, is a change in the frequency of alleles (alternate form of a gene) in a population over a period of time. Breeders of rabbits have long been familiar with a variety of genetic traits that affect the survivability of rabbits in the wild, as well as in breeding populations. One such trait was first discovered in England by W.E. Castle in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a definite selective force against it.
The dominant allele for normal fur (the presence of fur) is represented by F and the recessive allele for no fur (furless) is represented by f. Bunnies that inherit two F alleles (FF) or one F and one f allele (Ff) have fur, while bunnies that inherit two f alleles (ff) have no fur. Materials:
Small Containers
Markers
Tape
Paper Bags
50 Black Beans
50 White Beans Question/Problem: How does natural selection affect gene frequency over several generations? With your group, come up with a more specific question regarding the influence of fur on rabbit survival and therefore the presence of furry rabbits in the population. Hypothesis: State what you would predict (if your hypothesis is true) about the frequency of F (fur) alleles and f (furless) alleles in the population of rabbits after 10 generations, where ff bunnies do not survive (selected against).
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Procedure: 1. The black beans represent the allele for fur (F) and the white beans represent the allele
for no fur (f). The paper bag represents the English countryside, where rabbits randomly mate.
2. Label each of the small containers with the possible genotypes (FF, Ff, ff) and the phenotype.
3. Place the 50 black and 50 white beans (alleles) in the paper bag and shake up (mate) the rabbits.
4. Without looking at the beans, select two at a time, and record the results on the data table next to "Generation 1."
a. For instance, if you draw one red and one white bean, place a mark in the chart under "Number of Ff individuals."
5. Continue drawing pairs of beans and recording the results in your chart until all beans have been selected and sorted. Place the "rabbits" into the appropriate container: FF, Ff, or ff. (Please note that the total number of individuals will be half the total number of beans because each rabbit requires two alleles.)
6. The ff bunnies are born furless. The cold weather kills them before they reach reproductive age, so they can't pass on their genes. Place the beans from the ff container aside before beginning the next round (don’t put them back into the mating bag).
7. Count the F and f alleles (beans) that were placed in each of the "furred rabbit" dishes (FF or Ff) in the first round and record the number in the chart in the columns labeled "Number of F Alleles" and "Number of f Alleles." (This time you are really counting each bean, but don't count the alleles of the ff bunnies because they are dead.) Total the number of F alleles and f alleles for the first generation and record this number in the column labeled "Total Number of Alleles."
8. Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age) back into the mating bag and mate them again to get the next generation.
9. Repeat steps 4-7 to obtain generations 2-10. If working as a team, make sure everyone in your group has a chance to either select the beans or record the results.
10. Determine the gene frequency of F and f for each generation and record them in the chart in the columns labeled "Gene Frequency F" and "Gene Frequency f."
a. Gene frequency of F = number of F / total number of alleles b. Gene frequency of f = number of f / total number of alleles c. Record your group's frequencies on the data table below.
11. Graph your frequencies. Use the prepared graph with the horizontal axis as the generation and the vertical axis as the frequency in decimals. Plot all frequencies on one graph. Color code your graph for “frequency of F” and “frequency of f”.
12. Complete the Discussion Questions with your group.
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Data Table:
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Graph:
Key: Gene frequency of F: Gene frequency of f:
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
A
l
l
e
l
e
F
r
e
q
u
e
n
c
y
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Questions: 1. Based on your lab data, do you need to revise your hypothesis? Why or why not?
2. Compare the total number of alleles for the dominant characteristic with the number of alleles for the recessive characteristic. Over the course of 10 generations what trend do you observe?
3. Compare the frequencies of the dominant allele to the frequencies of the recessive allele over the course of 10 generations. What trends do you observe?
4. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How might emigration and immigration affect the gene frequency of F and f in this population of rabbits?
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5. How does a changing allele frequency relate to the formation of new species?
6. During the performance of this lab what part of the activity simulated the mechanism of natural selection on the genetics of the rabbit population?
7. Based on our definition of evolution explain how the results of this simulation acts as an example of evolution?
8. Why is reproduction so important to the process of evolution?
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CW 8: Lions, Tigers, and Ligers? …Ligons? Tigons?
Video Link: http://www.youtube.com/watch?v=1zOWYj59BXI
1. How was the Liger bread?
2. What is the inhibitor growth gene?
3. Why does mating a male lion with a female tiger result in such a large cat?
4. Why would a lion and a tiger never mate in the wild?
5. THINK ABOUT IT. Lions and tigers are separate species. Yet, it is possible for them to mate in captivity to produce offspring. Should lions and tigers be considered the same species? Are Ligers a new species? Explain.
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CW 9: Mutation and Selection Gizmo
Vocabulary: adaptation, allele, allele sequence, chromosome, evolution, fitness, gene, genotype, mutation, natural selection, phenotype, trait Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Imagine a white lizard and a brown lizard sitting on a brown rock. A hawk is circling overhead
hunting for its next meal. Which lizard do you think the hawk would most likely try to catch? Explain your choice.
__________________________________________________________________________ __________________________________________________________________________
2. Now imagine that the same two lizards were sitting on a dune of white sand. Which lizard do you
think the hawk would then most likely try to catch? Why?
__________________________________________________________________________ __________________________________________________________________________
Gizmo Warm-up
How long could a parrot survive in Antarctica? It would probably not survive long. Parrots do not have adaptations—or helpful characteristics—to survive icy cold weather. Because of this, a parrot is not fit for Antarctica. Fitness describes how well an organism can survive and reproduce in an environment.
In the Evolution: Mutation and Selection Gizmo™, you will see how a species’ fitness can change over time as it becomes better adapted to its environment. 1. On the SIMULATION pane, what is the Average fitness of the population? ______________ 2. On the CONTROLS pane, experiment with the Background color sliders.
A. Which background color results in the highest fitness? _________________________ B. Which background color results in the lowest fitness? _________________________
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Activity A: Inherited variation
Get the Gizmo ready:
Set the red value to 100, the green value to 255, and the blue value to 50 on the CONTROLS panel.
Introduction: An organism’s traits, or characteristics, are controlled by genes. Genes are located on rod-like structures called chromosomes. Different versions of genes that code for the same trait are called alleles. In this Gizmo, there are 3 genes on each chromosome. For each gene there are eight possible alleles: W (white), R (red), G (green), B (blue), C (cyan), M (magenta), Y (yellow), and K (black). Question: Where does variation in a population come from?
1. Observe: Hold your cursor over one of the insects on the SIMULATION pane. The two rod-like structures under Genotype on the CONTROLS pane represent chromosomes. The three letters next to each chromosome represent alleles.
Which alleles does the insect have? _____________________________________________
The alleles carried on an organism’s chromosomes make up the organism’s genotype. 2. Observe: An organism’s alleles combine to produce a trait. The physical expression of that trait is a
phenotype. In the Gizmo, phenotype is expressed in red, green, and blue values.
A. What is the phenotype of the insect? Red: _____ Green: _____ Blue: _____
B. What color is the insect? _________________________________________________ 3. Run Gizmo: Move the Sim. speed slider all the way to the left. Click Play ( ). You will see the
insects move to the left in pairs. The pairs mate and produce a set of four offspring. As soon as you see at least one offspring with an oval around it, click Pause ( ). Move your cursor over the circled offspring.
A. What is its genotype and phenotype? ______________________________________ B. How does its genotype and phenotype differ from the non-circled offspring?
_____________________________________________________________________
4. Explain: The change in the circled offspring’s genotype was caused by a mutation. A mutation is a
change in a gene. Mutations happen when a mistake is made when a cell’s chromosomes are copied. How might mutations introduce variation into a population?
__________________________________________________________________________
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5. Collect data: Move the mutation rate slider to 3.0, and click Play. Allow the Gizmo to run for another 10–15 generations. (You can see the generation number below the insects.)
Click Pause when the parents are ready to have offspring. Find a set of two parents that has four different chromosomes. (If you can’t find any, allow the Gizmo to run a few more generations and try again.) Write the allele sequences for these parents in the table below. Note the labels for each of these chromosomes: A1, A2, B1, and B2.
Organism: Parent A Parent B
Allele sequence of chromosome 1: (A1) (B1)
Allele sequence of chromosome 2: (A2) (B2)
Click Play, and then click Pause immediately after the offspring are produced. Write the allele sequences of chromosomes 1 and 2 for each of the offspring of your selected parents.
Offspring Allele sequence of chromosome 1 Allele sequence of chromosome 2
Offspring 1 ( ) ( )
Offspring 2 ( ) ( )
Offspring 3 ( ) ( )
Offspring 4 ( ) ( )
Label the offspring chromosomes A1, A2, B1, or B2. Circle any mutated chromosomes. 6. Analyze: Study the completed table.
A. Look at the inheritance patterns. What do you notice? _________________________ _____________________________________________________________________
B. Can a single offspring inherit both chromosomes from one parent? Explain. _____________________________________________________________________
C. Did any mutations occur in this set of offspring? ______________________________
If so, which chromosome mutated? ________________________________________
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Question: Are some organisms more likely to survive and reproduce than others? 1. Count: Move the Sim. speed slider all the way to the left. Click Play.
A. After the parents mate, click Pause. How many offspring are there? ______________ B. Click Play. After the birds eat, click Pause. How many offspring are left? ___________
In nature, as in the Gizmo, more offspring are born than can survive long enough to reproduce. Because of this, the offspring must compete with one another for survival. In this Gizmo, the insect offspring compete to avoid being eaten by birds.
2. Observe: Move the Sim. speed slider one notch to the right. Click Play, and wait for about 20
generations to pass. You should see a variety of insect phenotypes. (If not, click Play and wait until you do.)
A. What different colors of insects do you see? _________________________________
B. How do you think this variation might affect the competition between the offspring?
_____________________________________________________________________
_____________________________________________________________________ 3. Analyze: Scroll over the insects and note their fitness (shown under the Phenotype). The fitness of
an organism reflects how likely it is to survive and produce offspring. Each insect is given a percentage that reflects its chances of surviving to reproduce.
Compare the fitness percentages to the insect colors. How does fitness relate to the color of the insects? __________________________________________________________________________ __________________________________________________________________________
4. Predict: How do you think an insect’s fitness will affect is chances of being eaten by birds? __________________________________________________________________________
Activity B: Survival of the fittest
Get the Gizmo ready:
Click Reset ( ).
Set red to 255, green to 0, and blue to 130.
Move the mutation rate slider to 1.0.
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5. Collect data: In nature, chance alone can affect whether an individual survives. However, general trends in survival rates can be seen by studying a larger group of individuals.
Move the Sim. speed slider all the way to the left. Click Play, and then click Pause when all the offspring are visible. Write the generation number and the average fitness of all the offspring in the first two spaces of the table below.
Next, click Play, and then click Pause immediately after the birds have fed and the 10 survivors are visible. Mouse over each survivor and record its fitness. Find the average fitness of the survivors by adding these values and dividing by 10.
Repeat this experiment two more times, recording your results in the table.
Generation Ave. fitness Survivor fitness values Ave. survivor fitness
6. Recognize trends: Study the table above. What trends do you see? ____________________ __________________________________________________________________________ __________________________________________________________________________ 7. Analyze: In most situations, were the fittest insects or the least fit insects most likely to survive?
Explain how the data from your experiment supports your answer. __________________________________________________________________________ __________________________________________________________________________ 8. Think and discuss: The principle of natural selection states that the best adapted organisms are
most likely to survive and reproduce. Was this demonstrated in your experiment? Explain. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________
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Activity C: Evolution
Get the Gizmo ready:
Click Reset. Set red to 100, green to 255, and blue to 50.
Introduction: You learned in activity B that fit individuals have a better chance of surviving and reproducing than individuals that are less fit. In this activity, you will observe how natural selection affects a population over time. Question: How does a population change over time? 1. Experiment: Set the Background color to the values shown in the last column of the table below.
Record the Average fitness of generation 1 in the second column of the table. Move your cursor over the insects and find the individual with the greatest fitness. (In the first generation, all the insects will have the same fitness). Record that individual’s phenotype in the table’s third column.
Move the Sim. speed slider a quarter of the way to the right. Run the Gizmo, and complete the table for each listed generation. (The generation number does not have to be exact.)
Generation number
Average Fitness
Fitness of Fittest Individual
Phenotype of Fittest Individual (R, G, B)
Background color
1
red = 100
green = 255
blue = 50
25
50
75
100
150
200
300
2. Describe: Examine the data collected for trends.
A. How did the phenotype of the fittest individual change over time? _______________
_____________________________________________________________________ B. How did the population’s fitness change over time? ___________________________
_____________________________________________________________________
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The process by which populations change over time is known as evolution. This Gizmo only demonstrates how one trait—body color—can evolve.
3. Predict: Based on what you have just seen, how do you think the population will evolve if you
made the Background color purple? __________________________________________________________________________
4. Test: Set red to 120, green to 0, and blue to 160 to make a purple background. Click Play. After
300 more generations have passed, click Pause. Was your prediction correct? Explain. ___________________________________________ __________________________________________________________________________
5. Make connections: Why it is necessary for there to be variation in a population in order for
evolution by natural selection to occur? __________________________________________________________________________
__________________________________________________________________________ 6. Make connections: Why is it necessary for traits to be inherited for evolution to take place? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 7. Apply: Look carefully at the picture below and you will see an insect called a katydid. Katydids
evolved from grasshoppers through natural selection. Use what you have learned to explain how this could have happened.
_______________________________________________ _______________________________________________ _______________________________________________ _______________________________________________ _______________________________________________
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CW 10: Evidence of Evolution
Background When Charles Darwin first proposed the idea that all new species descend from an ancestor, he performed an exhaustive amount of research to provide as much evidence as possible. Today, the major pieces of evidence for this theory can be broken down into the fossil record, embryology, comparative anatomy, and molecular biology
The Fossil Record This is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day horse.
1. Give two similarities between each of the skulls that might lead to the conclusion that
these are all related species. 2. What is the biggest change in skull anatomy that occurred from the dawn horse to the
modern horse? 3. What is the biggest change in leg anatomy that occurred from the dawn horse to the
modern horse?
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Comparative Anatomy Shown below are images of the skeletal structure of the front limbs of 6 animals: human, crocodile, whale, cat, bird, and bat. Each animal has a similar set of bones. Color code each of the bones according to this key:
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4. For each animal, indicate what type of movement each limb is responsible for. Animal Primary Functions
Human Using tools, picking up and holding objects
Whale
Cat
Bat
Bird
Crocodile
5. Compare the skeletal structure of each limb to the human arm. Relate the differences
you see in form to the differences in function.
Animal Comparison to Human Arm in Form Comparison to Human Arm in Function
Whale Whale has a much shorter and thicker humerus, radius, and ulna. Much longer metacarpals. Thumb has been shortened to a stub.
The whale fin needs to be longer to help in movement through water. Thumbs are not necessary as the fins are not used for grasping.
Cat
Bird
Crocodile
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Compare the anatomy of the butterfly and bird wing below.
6. What is the function of each of these structures? 7. How are they different in form? Give specific differences. Compare the overall body structure of the cave fish and the minnow below.
8. What is the biggest, most obvious difference between the body structures of these two
fish? 9. Assume the two fish came from the same original ancestor. Why might the cave fish have
evolved without eyesight? 10. What kind of sensory adaptation would you hypothesize the cave fish has to allow it to
navigate in a cave, including catching and eating food?
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You have now studied three different types of anatomical structures:
Homologous structures show individual variations on a common anatomical theme. These are seen in organisms that are closely related.
Analogous structures have very different anatomies but similar functions. These are seen in organisms that are not necessarily closely related, but live in similar environments and have similar adaptations.
Vestigial structures are anatomical remnants that were important in the organism’s ancestors, but are no longer used in the same way.
11. Give an example of a homologous structure from this activity: 12. Give an example of an analogous structure from this activity: 13. Give an example of a vestigial structure from this activity: 14. Below are some vestigial structures found in humans. For each, hypothesize what its
function may have been.
Structure Possible Function? Wisdom teeth
Appendix
Muscles to move ears
Body hair
Little toe
Tailbone
15. How are vestigial structures an example of evidence of evolution?
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Molecular Biology Cytochrome c is a protein found in mitochondria. It is used in the study of evolutionary relationships because most animals have this protein. Cytochrome c is made of 104 amino acids joined together. Below is a list of the amino acids in part of a cytochrome protein molecule for 9 different animals. Any sequences exactly the same for all animals have been skipped. For each non-human animal, take a highlighter and mark any amino acids that are different than the human sequence. When you finish, record how many differences you found in the table.
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Animal Number of Amino Acid Differences Compared to Human Cytochrome C
Animal Number of Amino Acid Differences Compared to Human Cytochrome C
Horse
Shark
Chicken
Turtle
Tuna
Monkey
Frog
Rabbit
16. Based on the Cytochrome C data, which organism is most closely related to humans? 17. Do any of the organisms have the same number of differences from human Cytochrome C?
In situations like this, how would you decide which is more closely related to humans?
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DNA Analysis and Gel Electrophoresis 18. Gel electrophoresis can be used to determine the
relatedness of species. Organisms with the most similar gel patterns are more closely related than organisms with very different gel patterns. Based on the gel to the left, which two species are most closely related?
19. Explain how you were able to determine the relatedness of the species from the gel. 20. Name and discuss a source of error in performing and evaluating gel electrophoresis
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Cladograms This is a cladogram for the major groups of primates. Based on the relationships shown in this cladogram, answer each of the following questions: 21. Which primate species is most
closely related to humans? 22. Which primate species is most
distantly related to humans? 23. How long ago did speciation occur
between tarsiers and the ancestor of all the anthropoids?
24. According to this cladogram, about how long ago did the common ancestor between
humans and chimpanzees exist? 25. Explain why the statement “Humans evolved from monkeys” is incorrect.
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Conclusion 26. Charles Darwin published his book On the Origin of Species in 1859. Of the different types
of evidence that you have examined, which do you think he relied upon the most, and why?
27. Given the amount of research and evidence available on evolution, why is it classified as a
theory?
