Lab number three PDF

Preview

Summary

Lab for biology...

Description

Laboratory 3 Write-Up: Introduction to Evolution II Due to the length of this lab, there are no post lab questions. Each question is worth 0.5 points. II. Stickleback Evolution Virtual Lab 1. Define “model organism.” A model organism is a nonhuman species that is vigorously studied to further an understanding of a biological phenomena. 2. Why is the threespine stickleback a model organism for studies in evolution? (List at least two reasons.) It is a model organism for studies in evolution because they are easy to study due to their short generation time and their small demeanor. 3. How do spines protect ocean stickleback fish? Spines protect ocean Stickleback fish sticking out its pelvic spines and dorsal spines so predators have a hard time swallowing it. 4. Describe where its spines are located. Three spines are on its dorsal side, and two spines are on its ventral side. The spines on its ventral also help protect it from its pelvis. 5. The loss of stickleback pelvic spines is similar to the loss of which body parts in some other fourlegged vertebrates? It is similar to the loss of hind limbs. 6. Name two other vertebrate animals whose evolutionary histories included the loss of hind limbs. Two other vertebrate animals are manatees, snakes, and whales. 7. In addition to the spines, what is another component of the “armor” of a stickleback fish? Another component of the armor is the row of plates on both sides of its body. 8. Explain how the stickleback armor protects the fish from some predators. The spines stick out in almost a 90-degree angle making it really hard for predators to swallow them. The plates stick out a little too and makes it extra hard for the predators to swallow it. 9. How did ancestral populations of ocean-dwelling fish come to live in freshwater lakes?

During the end of the ice age, glaciers started to melt creating freshwater lakes. This opened up a new place for them to reproduce, but then the fresh water lakes got cut off from the ocean causing them to adapt to living in freshwaters. 10. What is the difference between marine, sea-run, and freshwater stickleback fish populations? Be specific. Marine stickleback fish only live and reproduce in the ocean, sea-run stickleback fish breed in freshwaters but live predominantly in the ocean, and freshwater stickleback fish live and reproduce in freshwater lakes. 11. From a researcher’s perspective, what is the benefit of having access to hundreds of postglacial lakes? The lakes allow for scientists to compare a trait such as pelvic reduction in all the populations throughout the lakes. The vast number of lakes helps researchers make hypotheses about how environmental conditions effect a trait. Describe the following structures: 12. Complete pelvis: This has full pelvic girdle and two pelvic spines.

13. Reduced pelvis: This pelvis can vary from a simplified girdle and no pelvic spines to an oval nub in place of the girdle. 14. Absent pelvis: This has no pelvis girdle or pelvic spines 15. Explain in your own words the overall objective of Experiment 1. The overall objective was to look at the pelvic structures of the stickleback fish from two lakes. The information gathered about the lakes in addition to the data collected will be used to formulate a hypothesis about certain environmental factors that effect pelvic morphology. 16. What lake is located between Bear Paw Lake and Frog Lake just to the north? It was Prator lake. 17. In a population, what happens to organisms that are better adapted to the environment in which they live?

If organisms are better adapted to the environment which they live in, they will live longer with a higher chance for breeding and pass on genetic variants to future generations. This causes certain traits to increase in frequency in the population. 18. Why do you think it is important to empty the used stain, destaining solution, and water under a fume hood? It is important because the hood has a vacuum that helps decrease the exposure to toxic fumes used in destaining the solution. 19. How were the fish you will be using in this virtual lab caught? They were caught using traps that are left overnight. These traps are cylinder shaped with funnel openings on the ends, and they catch the fish by the fish swimming in but not being able to swim out. 20. According to Dr. Bell, what is an important difference between Bear Paw Lake and Frog Lake? An important difference is that Bear Paw Lake is surrounded and does not drain at the surface. This does not allow predators to enter the lake whereas Frog lake has a small stream which easily allows predators to go into the lake. 21. Why are random samples, rather than entire populations, used in most research studies? They are used the most because it would take an abundance of time and money to look over all the individuals in a population, so they use random samples to make interpretations of a population. 22. What is one advantage of studying larger-sized samples? One advantage is larger-sized sample are more indictive of a population than smaller-sized samples are. 23. Give an example of sampling bias. An example is that fish in shallow parts of a body of water are caught because the traps are set there, so organisms in deeper waters do not get observed. These two samples could have different traits due to the conditions they are living in. 24. Why do you think it is important that the labels included in specimen jars be made of special paper that does not disintegrate in alcohol over time? It is important because labels contain very important information like location and date. The paper cannot disintegrate in alcohol because the fish are stored in isopropyl alcohol. If the label is damaged the scientists may not be able to tell the specimens apart.

25. Examine the pelvic score data you just collected. Does the pelvic phenotype differ between Bear Paw Lake and Frog Lake fish? Explain. Yes it does differ because Bear Paw Lake has mainly stickleback fish that do not have pelvic spines, and Frog Lake mainly has stickleback fish that have pelvic spines. 26. How do your data compare to those obtained by Dr. Bell and colleagues? The data is very similar and was consistent with Dr. Bell’s data. 27. Explain why the stickleback fish in Frog Lake are more similar to ocean and sea-run stickleback than they are to the stickleback fish in Bear Paw Lake. Fish that are in a marine and sea-run population are made up of complete pelvises, where the pelvic spines protect them from predators. The majority of the stickleback fish in Bear Paw Lake have an absent or reduced pelvis. The population of stickleback fish in Frog lase is predominantly made up of complete pelvises. 28. In addition to predators, what other environmental factors do you think might be responsible for the differences between Bear Paw Lake and Frog Lake stickleback populations? How would you test your prediction? The water in which the population of stickleback fish occupy may not contain enough calcium or other important minerals to form pelvic spines. This can be tested by measuring the amount of each mineral in the body of water and compare it to the ocean. 29. What score would you assign to a fossil specimen that has only one pelvic spine visible? Complete would be assigned. 30. A stickleback fossil may show no signs of pelvic structures. What are possible sources of error associated with scoring the pelvis of such a fossil as “absent”? Sources of error are damage due to decay or physical processes. This could cause some body structures to be invisible in the fossil. 31. In your own words describe the overall objective of Experiment 2 and explain what the data you collect will allow you to estimate. The overall objective is to analyze the pelvic structures of fossil stickleback fish in the Truckee Formation region. The fossils being found are fish that were in the lake during a 15,000-year period. This will allow for the rate of change in the frequency in relation to the complete pelvic phenotype to be estimated over time. 32. Watch the short video on the Truckee Formation in Nevada. What does each sedimentary rock layer of the Truckee Formation represent?

The layers represent a year of deposition. In the Truckee Formation sedimentary rock, there was the skeletal remains of microscopic algae. 33. What is one type of information that researchers can gain from studying fossils that they cannot obtain from living populations? One type of information is the study of fossils can indicate long-term patterns of evolutionary change which can help researchers calculate the rate of change for specific traits. 34. Approximately how many years apart are any two adjacent samples? They were approximately 3,000 years apart. 35. You will collect data on pelvic structures using fossils from rock layers 2 and 5. Approximately how many years of deposition separate these two layers? It is approximately 9,000 years. 36. Which layer is older, 2 or 5? Explain your answer. The layers are numbered in increasing order, therefor layer two is older. 37. Based on the pelvic phenotypes you measured, do the fossils in layer 2 differ from those in layer 5? Explain how. Yes because in layer two, the stickleback fossils pelvic spines were more prominent than they were in layer five. Most of layer five had fossils with no pelvic spines. 38. How do your data compare to those collected by Dr. Bell and colleagues? The data from the graph was again similar and consistent with Br. Bell’s data. 39. What can be inferred about the presence or absence of predatory fish when the Truckee Formation was a lake? Describe the evidence. It can be inferred that the pelvic spines did not give an advantage because the frequency of the fossils with pelvis spines decreased over 15,000 years. This also tells researchers that there was no predators in the lake because the pelvic spine protect against them. 40. Complete the tables below as you perform the rate calculations. (The link to the instructions is very helpful.)

Sample Layer

Number of Fish with a Complete Pelvis

Total Number of Fish Sampled

1 2

20 18

20 20

Relative Frequency of Complete Pelvis Trait in Population Sampled 1.00 0.90

3 4 5 6

3 1 0 0

Time First 3,000 years (Layer 1 to Layer 2) Next 3,000 years (Layer 2 to Layer 3) Next 3,000 years (Layer 3 to Layer 4) Next 3,000 years (Layer 4 to Layer 5) Next 3,000 years (Layer 5 to Layer 6) Total 15,000 years (Layer 1 to Layer 6)

20 20 20 20

0.15 0.05 0.00 0.00

Decrease in Percentage of Complete Pelvis Trait per Thousand Years (Rate of Change) -0.033 = -3.3% -0.25 = -25% -0.033 = -3.3% -0.017 = -1.7% 0.00 = 0% -0.067 = -6.7%

41. What does it mean when the rate of change is a negative number? It means that there is a decrease in the quantity being observed in this case it was pelvic spines. 42. Describe the trend in the data over time. The relative frequency decreased rapidly the first 9,000 years, then started to plateau towards the end of the 15,000-year period. After this, there were no fish with a complete pelvis found in the fossils. 43. Why is it important to calculate the rate of change over time? It is important because it can help come to conclusions about some parts of the evolution of traits in living fish. This is not very common because of long time scale of the majority of evolutionary processes. 44. In what way is the change in the complete pelvis phenotype in the fossils from the Nevada lakebed similar to what might have occurred in Bear Paw Lake from Experiment 1? Most of the stickleback fish in Bear Paw Lake have absent or reduced pelvises because the pelvic spine phenotype has decreased. This also happened in Nevada lake. This was found in the rock layers. 45. In your own words describe the overall objective of Experiment 3.

The overall objective is to observe the reduced pelvis trait closely by scoring stickleback fish from two populations. There will be a focus on pelvic asymmetry and if the reduced pelvis is larger on one side in a population. 46. What is one function of the Pitx1 gene? It is a gene that affects the development of the pelvic girdle and pelvic spines in stickleback fish and in the hind limbs of some organisms. 47. What is the relationship between changes in body form, the process of development, and genes? Changes in the process of development can cause changes in body form, so this is because of changes in genes because genes control development. 48. Why did Dr. Kingsley do genetic crosses with stickleback fish? He did this to find out which genes affect pelvic reduction in freshwater fish. 49. Which one of the three pelvic girdle phenotypes is analyzed in more detail in this experiment? The reduced pelvis phenotype is analyzed in more detail. 50. What is the difference between left-biased and right-biased pelvic asymmetry? The pelvic vestige is usually not the same on both sides; either the left side is bigger rendering it left-biased or the right side is larger rendering it right-biased. 51. How do your data compare to those collected by Dr. Bell and colleagues? The scored pelvises are similar and consistent to Dr. Bell’s data. 52. The pelvic asymmetry observed in stickleback fish from Bear Paw Lake and Coyote Lake is biased toward which side? It is biased toward the left. 53. Based on previous research conducted in mice, what does this observed bias among Bear Paw Lake and Coyote Lake stickleback suggest about the genetic mechanisms of pelvic reduction in these two populations? The research presented mice lacking the Pitx1 gene function without complete hind limbs. The fossils showed the pelvis and hind limbs and that the left side was more prevalent. This concludes that there was left bias in Bear Paw Lake and pelvic reduction in Coyote Lake stickleback is due to mutations of the Pitx1 gene. 54. For this analysis, what is the null hypothesis?

The null hypothesis is in a certain population with pelvic reduction, it is expected that the left and right bias fish should be fairly equal. 55. Bear Paw Lake Phenotype Observed (o) 18 Left Bias

Expected (e) 10

(o-e) 8

(o-e)2 64

(o-e)2/e 6.4

Right Bias

2

10

8

64

6.4

Total = 20

Total = 20

56. Coyote Lake Phenotype Observed (o) Left Bias 20 Right Bias

χ2 = 12.8

Expected (e) 10

(o-e) 10

(o-e)2 100

(o-e)2/e 10

0

10

10

100

10

Total = 20

Total = 20

χ2 = 20

57. For each chi-square calculation, how many degrees of freedom are there? df = 2-1 = 1 58. What are the p values for the data from each lake? Bear Paw lake: 0.01 Coyote Lake: 0.01 59. Do you “reject” or “fail to reject” your null hypothesis for the data from each lake? Bear Paw lake: reject Coyote Lake: reject 60. What does it mean to reject the null hypothesis for Bear Paw and Coyote Lakes? It means that any differing data from the recorded data and the equal amount of left and right bias is unlikely to be because of chance. There can be a biological explanation of most of the fish having pelvic asymmetry....