1. Determine variations in a population.
2. Generate hypotheses regarding variation and adaptation.
3. (f) Construct a habitat to select for or against one variant.
4. (s) Use a metric ruler to measure individuals in a population.
5. (s) Calculate the area of each individual in a population using graph paper.
6. (s) Construct graphs of data collected.
7. (s) Determine dispersal distance in seeds.
8. (s) Determine percent and rate of germination in seeds.
9. (*s) Determine growth rate of plants.
10. (*f) Use Hardy Weinberg equilibrium formula to determine if evolution has occurred in a population.
11. (*s) Determine the mass of each individual in a population.
Evolution, natural selection, adaptation, fitness, species, Hardy-Weinberg Equilibrium, over-production of offspring, requirements for survival of organisms, population, allele, gene, mutation.
To successfully complete this activity, students must have a knowledge of
1. Drosophila handling techniques.
2. The concepts of evolution, natural selection, adaptation, and fitness, and Hardy-Weinberg equilibrium should have been discussed in lecture or recitation.
3. The difference between metric and English on a ruler.
Any or all of these activities may be used in any order or combination.
A. Fruit flies - "Drosophila Park"
1. Give students two (or more) vials of flies. One set should be Wild type and the other(s) mutant, e.g. apterous (wingless), eyeless, etc. Or give students examples of 2 or more types of flies in a Petri dish.
2. Anesthetize flies and observe.
3. Ask students to characterize flies: what characteristics do they notice? What do they share, what is different? These should be listed.
4. Ask students which characteristics they think might confer some advantage or disadvantage to the flies with that characteristic and what that advantage or disadvantage might be.
5. Challenge students to design a habitat that would select for (or against) one characteristic: brainstorm some things required to support organisms that must be included in the habitat (moisture, food for larvae, oxygen for fish if used, light for plant if used to provide oxygen for fish).
6. Have students develop a hypothesis. Which characteristic will be selected for or against in their habitat? Include a control.
7. Allow students to construct habitats from materials available in lab. (see attached list). Once constructed, students should draw diagram of habitat and/or describe it.
8. During habitat construction , containers of media should be installed in each chamber. Ask students to consider how food will be added during the experimental period.
9. After completion, students introduce flies into the habitat. Have them record the number of each phenotype and sex introduced and where they are introduced. These numbers should be discussed with the instructor. Females should be virgin and all flies should be homozygous.
10. Set habitats aside for one or several weeks depending on your schedule.
11. Open habitats and observe where flies are located. Count the numbers and sexes. If barriers are placed, which animals did or did not make it over? Students should suggest possible reasons why and why not.
12. Record observations. Do the results support the hypothesis? Why or why not?
13. Can lead into Hardy Weinberg equilibrium analysis of the populations and any other aspects of fly biology you want.
Then lead into short discussion of how all organisms in a population (ask for definition, refine if necessary) are not the same and that these variations may be beneficial or harmful, depending on the environment.
1. Give students packet of maple samaras (can be collected locally or ordered from biological supply companies). Samaras are 1-seeded, dry, winged fruits.
2. Observation of fruits. Ask students the following questions: What are these? What organism produced them? Where are they produced on this tree? How are they constructed? How are they similar? How are they different? How do they function? Why not just the bare seed?
3. Measure the characteristics the students come up with. Length, width, area (use graph paper), mass.
4. Formulate hypothesis regarding characteristics and dispersal.
5. Test dispersal by dropping from about 10 and 20 ft height (stairwell or balcony) and record data.
6. Graph data. e.g. distance vs. area, distance vs. length, distance vs. mass/area ratio.
7. Do the data support the hypothesis?
8. Why are the seeds different? Are there any possible advantages or disadvantages?
9. Compare with acorns, pecans, or other nuts (characteristics, measurements, dispersal distance). If wings are necessary for dispersal, why don't acorns or pecans have wings? How might they be dispersed?
Germination/growth can be done as continuation of the maple seed dispersal exercise if the seeds are not dried out or preserved.
1. Give each group one set of large bean seeds. What are these? (embryonic bean plants, 2 large cotyledons & NO endosperm)
2. Is here any variation in these seeds? What characteristics could you measure?
3. Measure (e.g.length) 100 seeds per group and divide the seeds into size categories (six or more). Place categories in large test tubes lined up in a rack to illustrate a size distribution. (should approach a normal distribution)
4. Ask students about the advantages or disadvantages that may be conferred by this characteristic. Students should come up with the idea of germination - if not, lead discussion in that direction.
5. Formulate a hypothesis about seed characteristic and germination or plant growth.
6. Have students germinate the seeds of various categories on agar in test-tubes or in plastic cups with paper towels or vermiculite to observe percentage and rate of germination, and (if in agar) measure growth of root and shoot.
7. Record data, graph and analyze.
8. Do the data support the hypothesis?
9. This exercise can be continued to study plant growth.
1. Have supply of materials for habitats.
2. Maple samaras: collect fresh and place in ziploc bags and near freezing refridgeration. Keep in refrigerator while in class use. If dried out, ratio of mass to wing area is altered affecting results, and of course, dead seeds will not germinate.
3. Media for flies should be placed in small cups or vials in the bottom of habitat chambers, not spread thinly.
1. Fruit flies: two or three morphs (wildtype, eyeless, apterous), flynap or alternative (CO2), media and yeast, bottles for flies, scissors, scalpels razor blades, punch, drill, plastic soft drink bottles, foam cups, clear plastic cups, fly paper, single and double-sided tape, glue, rubber cement, petroleum jelly, hot glue gun, straws or tubing, mosquito fish, Elodea, foil, colored cellophane, dissection microscope or hand lens.
2. Maple samaras: metric rulers, graph paper, large grid with plumb bob, tape measure, sharpies, wind or table fan.
3. Bean seeds: 100 seeds (kidney, lima, or other large bean seed) per group, test-tube rack and 10 large test tubes, metric ruler.
4. Germination and plant growth: two clear plastic cups, one inside the other, with paper towels between the cups, or a cup filled with vermiculite. Seeds should be placed around periphery so they are visible through the outer cup, -OR- test tubes with non-nutrient agar and cap or cotton. Light is not necessary since you want to measure germination and growth as a function dependent on size (food) stored in the embryo during pre-dispersal development.
1. Fruit flies
a. Reproduction of flies and dispersal.
b. Some characteristics are not as advantageous in some habitats as in others.
c. Appearance of recessives in the F2 (if carried through F2).
d. Variation in allele frequencies in F2.
e. Barriers to dispersal.
a. Variation in individuals of the population.
b. Adaptation for dispersal.
c. Correlation of structure with function.
d. Graph of dispersal vs. length, mass, area.
e. Advantage of area and or mass?
a. Variation - characteristics.
b. Graph or visual histogram in large test tubes showing normal bell-shaped distribution of size.
c. Advantage of size in germination and growth.
d. Germination: percent, rate.
e. Growth rate.
f. Relation of germination and growth to characteristics observed.
g. Time Frame
1. Fruit flies: 1-2 hr period to set-up. Continue as long as you want. Check as often as desired. Run for 30 days for hatching of F2.
2. Maple samara dispersal: 2-3 hr. Planting 15-30 minutes more (longer if comparing to other seeds).
3. Beans and planting: 1-2 hrs.
4. Germination: check next lab period, continue to grow if want to observe growth up to point of expansion of 1st primary leaves. Even if in light, growth up to the point of expansion of the 1st primary leaf uses almost wholly stored energy reserves.
<5>OBJECTIVES:
Upon completion of this unit, you should be able to: i. Determine variations in a population. ii. Generate hypotheses regarding variation and adaptation. iii. Construct a habitat to select for or against one variant. iv. Use the Hardy-Weinberg equilibrium formula to determine if evolution has occurred in a population. 1. You have been given a Petri dish of fruit flies, Drosophila melanogaster. Use a dissecting microscope or hand lens to observe these organisms. List the characteristics of these flies. Are the flies all the same?_______ How are they alike or different? Which of the characteristics do you think would be the more advantageous to the flies and in what kind of environment? Which would be disadvantageous and in what kind of environment? 2. Design an environment that would favor one characteristic (either the one you decided was advantageous or the one you decided was disadvantageous.) What components would be necessary to the keep the organisms alive? 3. Develop a hypothesis regarding your designed environment and the chosen characteristic. 4. Build your designed environment using the materials available in lab. 5. Count the numbers and sexes of flies with each characteristic. Then introduce your flies into your constructed environment. 6. Observe at various times of the semester/quarter. 7. After the prescribed time, capture the flies from the environment and count numbers and sexes with each characteristic. 8. Are the ratios of flies present the same now as at the beginning? If not, flies with which characteristic are now present in higher numbers? lower numbers? 9. Do your results support your hypothesis? Suggest possible reasons for your results. Optional: Calculate allele frequencies for the before and after situations. Has there been a change in allele frequencies? Has evolution occurred? Determine phenotypic ratios of the before and after situations. What changes do you see? Explain why and how these changes may have occurred. STUDENT PROTOCOL - Leaving Home (Seed dispersal) OBJECTIVES: Upon completion of this unit, you should be able to: i. Determine variations in a population. ii. Generate hypotheses regarding variation and adaptation. iii. Use a metric ruler to measure individuals in a population. iv. Calculate the area of each individual in a population using graph paper. v. Construct graphs of data collected. vi. Determine dispersal distance in seeds. vii. Determine the mass of each individual in a population. 1. You have been given a packet of maple "seeds", which are actually samaras, 1-seeded, dry, winged fruits. 2. What do you think a seed is? (or What are these? Where do they come from?) 3. What do you think the purpose of the fruit is? 4. What advantages or disadvantages might these differences provide for this species? 5. Even though these samaras appear different from other fruits/seeds, are they themselves all identical? 6. In what ways are they different from one another? 7. How could you measure these differences? 8. Use materials available in the lab to measure any differences. 9. Construct a graph of your data. 10. For one characteristic, are all the samaras the same? If not how are they different? 11. How might any differences in one characteristic benefit an individual seed? 12. Develop a hypothesis based on your answer to number 11. 13. Design a way to test your hypothesis. Discuss your design with your instructor and then test your hypothesis. 14. Do your results support your hypothesis? Explain. STUDENT PROTOCOL - Magic Beans: Variation and Germination OBJECTIVES: Upon completion of this unit, you should be able to: i. Determine variations in a population. ii. Generate hypotheses regarding variation and adaptation. iii. Use a metric ruler to measure individuals in a population. iv. Construct graphs of data collected. v. Determine percent and rate of germination of plant seeds. vi. Determine growth rate of plants. vii. Determine the mass of each individual in a population. 1. You have been given approximately 100 beans. What is a bean? Where do they come from? To a bean plant, what are beans? 2. Are all of these alike? If not, how are they different? 3. How could you measure some of these differences? Use materials available in the lab to measure the differences. 4. Construct a graph of your data. 5. For one characteristic, are all of the seeds alike? If not, do the differences confer any possible advantage to the individual seeds? 6. Develop a hypothesis based on your observations. 7. Design a way to test your hypothesis. Discuss your design with your instructor and then test your hypothesis. 8. Do your results support your hypothesis? Explain your results.