Research an Ecosystem (possible

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Project 1

Evaluation 31

Biology 1 (SCIH 025 062)

Be sure to include ALL pages of this project (including the directions and the assignment) when you send the project to your teacher for grading. Don’t forget to put your name and I.D. number at the top of this page!

This project contains a total of 100 points possible and will count for 14% of your overall grade for this course. Be sure to read all the instructions and assemble all the necessary materials before you begin. You can complete this entire project electronically by downloading and saving this editable copy of Project 1. You can complete all three parts using your word processing program, and save them in either .pdf (Portable Document Format), or .doc (Microsoft Word Document) format. When you have completed this project you can submit it electronically through the online course management system. Remember that a file that is larger than 5,000 K will NOT go through the online system. Check the instructions in the online course for more information.

This needs to be your own work. DO NOT copy and paste information from the sources that you use. You need to write everything you learn in your own words. REMEMBER: failing to cite sources or submitting another person’s work as your own is PLAGIARISM, which will result in a failing grade.

Part A – Research an Ecosystem (possible 60 points)

Follow the procedures below to complete this part of the project. Save it as SCIH025062Project1A.doc

Objective

The objective of the first part of this project is for you to demonstrate your understanding of the complex interrelationships between organisms in an ecosystem, and their living and nonliving environment.

Procedure

Your job is to choose an ecosystem that interests you and research it. It can be one near your home, or far away. You are investigating an ecosystem NOT a biome, so if you wanted to investigate a ‘wetland’, chose a ‘wetland’ in a particular area, don’t investigate ‘wetlands’ in general.

You can organize your research in one of several different ways for submission. Be sure to pick the format that you enjoy the most to present your research and make the most of the tools that are available to you. You can choose between one of the following formats:

1. Informational brochure

2. Essay format

3. Web site

4. PowerPoint Presentation

Regardless of the format you choose, you should be sure to include all the required information as well as any pictures, graphics, web resource URLs, and other additional information that will make your project interesting as well as informational. DO NOT just fill in the outline with pertinent details. Create your project for an audience that is not familiar with your ecosystem. Include all the information they need to get the full understanding of the ecosystem that you are researching! Feel free to add pages to this document to make sure you have all the space you need.

**If you choose to complete your project in a non-document format, be sure your name, course number, and student ID are on the project so that your teacher can give you the credit you earn with your hard work.

Required Elements:

DEFINITION of an ecosystem (1.5 pts) and DESCRIPTION of the ecosystem (1.5 pts) of your choice (wetland, desert, riparian forest, etc.).

DESCRIBE and EXPLAIN aspects of the ecosystem and how they relate to one another.

A. Animals (fauna)

species that are a part of the ecosystem (3 pts)

food web (Hint: Please include an image of a food web for your ecosystem. Please explain the image such as what they eat, what the flow of energy arrows represent and how it is related to the environment.) Create your own image or properly cite from the Internet. (3 pts)

relationships to plants (Hint: Between plants and animals—this is different than explaining feeding relationships, i.e. symbiotic relationships such as mutualism, commensalism and parasitism.) (3 pts)

adaptations (Hint: What adaptations do the animals show to this specific ecosystem, to the climate, or geological features?) (3 pts)

B. Climate

seasons (Duration of/when do they occur?) (3 pts)

weather patterns. (Hint: For example, grasslands located in Nebraska would/could experience tornadoes or thunderstorms in the spring. Discuss the type of weather that occurs during each season. Try to be more specific than simply indicating it’s cold in the winter and warm in the summer.) (3 pts)

temperature range and variation (Quantify by month or season) (3 pts)

rainfall (Quantify by month or season) (3 pts)

wind (Quantify by month or season) (3 pts)

humidity (Quantify by month or season) (3 pts)

extreme events: hurricanes, tornadoes, flash floods, etc. (3 pts)

C. Plants (flora)

species that are a part of the ecosystem (3 pts)

adaptations: (Hint: What adaptations do the plants show to this specific ecosystem, to the climate, or geological features?) (3 pts)

D. Geological Features

soil/substrate types (3 pts)

terrain (mountains, plains, valleys, etc.) (3 pts)

continental orientation (coastal, island, interior, etc.) (3 pts)

rock structures (3 pts)

hemispheric orientation: where the ecosystem is on the face of Earth (3 pts)

E. Other

Indicate how humans have are positively and/or negatively affecting the ecosystem. (3 pts)

Part A of your project will be graded using the following rubric:

Objective

Exceeds minimum project expectations

Meets minimum project expectations

Approaches course expectations

Does not meet course expectations

 

60 Points Possible

60-50

50-40

40-30

29 and below

 

Demonstration of content knowledge

 

Project content applies, identifies, and uses appropriate course-related scientific concepts. Student went beyond the course-based resources to incorporate additional information.

Project content applies, identifies, and uses most of the appropriate course-related scientific concepts.

 

Project content sometimes applies, identifies or uses appropriate course related scientific concepts.

Project content does not apply, identify or use appropriate course related scientific concepts.

 

Integrating and organizing content

 

In addition to all required elements, student provided clearly articulated descriptions for someone who knows little or nothing about the topic. Student went beyond the course-based resources to incorporate additional information.

Student incorporated the required elements as well as provided clearly articulated descriptions for someone who knows little or nothing about the topic.

Student incorporated most of the required elements in the project.

Student did not incorporate the required elements in the project.

 

Use of resources

Student went beyond the course-based resources to incorporate personal ideas, additional information and described or developed additional media to enhance the activity.

Student critically analyzed resources and used most or all available course-related resources in the project.

Student used some course related resources in the project.

 

Student did not use resources effectively in the project.

 

 

Part B – Lab Activity 3 (20 points possible)

Complete MiniLab 2: Prepare a Scientific Argument on page 77 of your textbook. See Lesson 3 for additional instructions about completing this lab. Save it as SCIH025062Project1B.doc

Part C – Lab Activity 4 (20 points possible)

Complete Data Analysis Lab 4.1 of your textbook. See Lesson 4 for additional instructions about completing this lab. Save it as SCIH025062Project1C.doc

This project can be submitted electronically. Check the Project page under “My Work” in the UNHS online course management system or your enrollment information with your print materials for more detailed instructions.

Project 1 PAGE * MERGEFORMAT 102 SCIH 025

Name I.D. Number

Project 1 PAGE * MERGEFORMAT 99 SCIH 025

 
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Bio 101 Experiment Species Interactions: Competition

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How to Proceed

  • Read through the introductory materials below.
  • Open the Unit 8 Experiment Answer Sheet and complete the following Experiment exercises this unit:
    • Experiment 8 Exercise 1 – Species Interactions: Competition
    • Experiment 8 Exercise 2 – Biomes

Species Interactions: Competition – Introduction

This unit we are learning about species-species interactions and how species influence each other (see pp 428-432 and our online lecture). One important interaction is interspecific competition, in which two or more species compete for limited resources. Competition, along with predation and symbioses (e.g., commensalism, mutualism, and parasitism) are important biological interactions that affect the size of species populations.

In the first exercise, we will examine the population growth of two species of freshwater ciliates. Populations of these species initially grow exponentially (see p 408), but the population does not increase in size forever. Eventually it reaches what is known as the carrying capacity of the environment, or the maximum population size the environment can support due to limitations in food, water or other resources.

Competitive exclusion (see p 429) may occur between two species that compete for the same resources. In this situation, only one species will be successful, such that the other species is forced to move elsewhere or die out. This rarely happens in nature though, since the species on the losing end typically switches to an alternate resource. However, under artificial situations, elimination of one species can occur.

The purpose of this exercise is to use a simulation to model competitive exclusion using the microscopic organisms that Gause used to come up with his competitive exclusion principle (see p 429). You will need to use the following website. Be sure you can access it and use it:

Glencoe/McGraw Hill. No date. Population Biology
http://www.mhhe.com/biosci/genbio/virtual_labs/BL_04/BL_04.html (Links to an external site.)

When you are ready to begin, go to the above website and open the Unit 8 Experiment Answer Sheet and follow the instructions.

In Biomes – Introduction

This unit we have learned about the large scale ecosystems called Biomes. They have developed over millions of years and the flora and fauna found in each biome type have adapted to the long term climate conditions (e.g., average rainfall, average temperatures). The purpose of this exercise is to see how well you understand the biotic and abiotic factors that shaped the various biomes. Review pp 384-390 and our online lecture this unit before beginning.

You will need to use the following websites. Be sure you can access them and use them:

NASA. No date. The Great Graph Match
http://earthobservatory.nasa.gov/Experiments/Biome/graphmatch_advanced.php  (Links to an external site.)

NASA. No date. To Plant or Not to Plant
http://earthobservatory.nasa.gov/Experiments/Biome/plant_it.php (Links to an external site.)

When you are ready to begin, open the Unit 8 Experiment Answer Sheet to complete this exercise.

WEEK 8 EXPERIMENT ANSWER SHEET Please submit to the Week 8 Experiment dropbox no later than Sunday midnight.

SUMMARY OF ACTIVITIES FOR WEEK 8 EXPERIMENT ASSIGNMENT

· Experiment 8 Exercise 1 – Species Interactions: Competition

· Experiment 8 Exercise 2 – Biomes (Part I and II)

Experiment 8 Exercise 1: Species Interactions: Competition

In this exercise you will be evaluating the effect of competition on the population size of two species of microorganisms. Be sure you have read through the readings for Week 8 as well as the introductory information for the Week 8 Experiment. When you are ready to begin, open in the following website:

Glencoe-McGraw Hill. No date. Population Biology http://glencoe.mcgraw-hill.com/sites/dl/free/0078759864/383928/BL_04.html

Procedure

A. Click on the Information button on the bottom and read through the material before beginning. You will need to scroll down to read all of the information. Close the window when you are done. Note that the two species we will be using will be competing for the same food source; bacteria.

B. First, you need to set up the experiment by distributing the two species to the three test tubes.

a. Click on the pipette (the purple bulb) in the flask containing P. caudatum, fill it and place the contents in Tube #1.

b. Then click on the pipette in the flask containing P. aurelia, fill it and place the contents in Tube #2.

c. Finish by putting a pipette full of both species in the Tube #3.

C. Answer the question below before proceeding.

Question

1. The number of P. caudatum and P. aurelia grown alone would be expected to increase until the population size reaches the carrying capacity of the test tube. What do you think will happen in terms of population growth in Tube #3 that contains both species combined and why (2 pts)?

Procedure (continued)

D. You now need to count the number of organisms in each Tube beginning on Day 0 and continuing every 2 days until you reach Day 16. These values will need to be recorded in Table 1 below (do NOT use the Table provided by the website).

a. Click on the Microscope to get started.

b. Click on Clean microscope slides and then Take Sample.

c. Click on the first slide and drag it on to the microscope. Count the number of P. caudatum (note its shape) and multiply by 2 to get the number of cells per ml (your slide holds 0.5 ml). Record this number in the Table below; this is Day 0.

d. Next, click on the second slide and drag it to the microscope. Count the number of P. aurelia (note its shape), multiply by 2 and record this number in the Table for Day 0.

e. Finally, drag the third slide on to the microscope and count the number of each type of organism, multiply by 2 and enter the data into the Table.

f. Click on Clear Slides (on the bottom) and then on the Calendar that says Day 0 to advance it two days.

g. Repeat steps b – f until you reach 16 days.

h. As the days go on, you will have more and more individuals to count. Click on the Grid On button on the microscope to make them easier to count.

Table 1. Results (4 pts).

  Grown Separately (cells per ml) Grown Together (cells/ml)
Day P. caudatum P. aurelia P. caudatum P. aurelia
0        
2        
4        
6        
8        
10        
12        
14        
16        

E. Now it is time to analyze your data.

a. You will need to generate two graphs, one which depicts the number of both species per day of culture when grown separately and one that depicts the number of both species per day of culture when grown together.

b. You must use the Scatter type graph in Excel and each graph should have two lines (one for each species).

c. Be sure you label your axes and your series; meaning you will need to indicate which line pertains to P. caudatum and which to P. aurelia.

Paste your two graphs below (4 pts):

Questions

2. What were the carrying capacities (maximum population size) for the two species when grown separately and on what day were they reached (1 pts)?

3. Describe what happened when the two species were grown together and explain why. Be sure to discuss the magnitude and timing of each species’ carrying capacity compared to when they were grown separately (3 pts).

4. Do these results support the principle of competitive exclusion; why or why not? Be sure to cite your sources. (4 pts).

Experiment 8 Exercise 2: Biomes

In these two relatively short exercises, we will be examining the biotic and abiotic factors that define a biome. You should have completed the readings for this week before beginning.

Procedure – Part I: The Great Graph Match

A. Open the following website:

NASA. No date. The Great Graph Match http://earthobservatory.nasa.gov/Experiments/Biome/graphmatch_advanced.php

B. In the Great Graph Match, you will need to match abiotic information (annual rainfall and temperatures) to the appropriate biome. Follow the instructions on the page and fill-in the Table below. For the Explanation column, you need to briefly explain why you chose the biome you did based on the data presented.

C. Be sure to provide complete citations for the sources used.

Table 2. Locations, biomes and explanations (4 pts).

Location Biome Explanation
Frogmore, England    
Goteborg, Sweden    
Koombooloomba, Australia    
Barrow, Alaska    
Alice Springs, Australia    
San Bernadino, California    
Centralia, Kansas    

Citations:

Procedure – Part II: To Plant or Not to Plant

A. Open the following website:

NASA. No date. To Plant or Not to Plant http://earthobservatory.nasa.gov/Experiments/Biome/plant_it.php

B. In the To Plant or not to Plant, you will need to determine which in which biomes to plant various plants, based on the information presented. Follow the instructions on the page and fill-in the Table below. For the Explanation column, you need to briefly explain why you chose the biome you did.

C. Be sure to provide complete citations for the sources used.

Table 3. Plants, biomes and explanations (4 pts).

Plant Biome Explanation
Creosote bush    
Spruce    
Flowering dogwood    
Orchid    
Lichen    
Bluestem grasses    
White sage    
Saguaro cactus    

Citations:

Week 8 Questions

1. Are most invasive (exotic) species K-selected or r-selected species? Explain your choice and why that makes sense in terms of their ecological success.

 

Citation(s):

2. Briefly define a community and an ecosystem and describe how the two are interrelated.

 

Citation(s):

3. Which of the following levels of organization are in order, from simplest to most complex.

a.  population, organism, community, ecosystem b.  community, ecosystem, population, organism c.  organism, community, population, ecosystem d.  population, ecosystem, organism, community e.  organism, population, community, ecosystem

4. Mosses growing on bare rock will eventually help to create soil.  These mosses are involved in ___ succession.

a.  primary b.  secondary c.  tertiary

5. If a farmer sprays a pesticide onto a field and kills half of the insect pests, he has caused a reduction in________.

a.  field capacity b. carrying capacity c. population size d. More than one of the above

6. What type of survivorship curve would you expect for a plant species in which only a few seeds are produced and most of these survive to produce adult plants?

a.  type I b.  type II c.  type III

7.  An ecological niche is an organism’s_______ in an ecosystem.

a. location b.  habitat         c.  resources         d.  function

8. No matter how rapidly populations grow, they eventually reach a limit and begin to stabilize. This is called the ______________.

9. Unicellular algae live in the tissues of coral animals.  The algae provide food for the coral, while the coral provides a stable home for the algae. This is an example of

a.  Parasitism b.  Commensalism c.  Mutualism

10. The vast majority of energy taken into an ecosystem is____________.

a.  converted into biomass by plants. b.  utilized by secondary consumers. c.  lost as heat. d.  used by the primary consumers. e.  concentrated in the decomposers.

11. A farmer is using an insecticide to treat his crops. While most insects do not survive their first exposure to the insecticide some have a gene that enables them to survive. When these survivors reproduce they will likely pass along this resistance to their offspring. This results in an increase in numbers of the insects over time. Which of the following processes applies to this survival?

a. cloning b. mutation c. natural selection d. genetic engineering

12. What is the ecological relationship between insects and crops?

a. mutualism  b. competition c. predation

13. Sea anemones growing on the backs of crabs without damaging the crabs are an example of

a.  Parasitism b.  Commensalism c.  Mutualism

14. Which of these is a population density-independent regulating factor?

a.  Competition b.  Predation c.  Size of population d.  Weather e.  Resource availability

15. Producers are_________.

a.  Autotrophs b.  Herbivores c.  Omnivores d.  Carnivores

16.If biological magnification occurs, the ___ will have the highest levels of toxins in their systems.

a.  producers b.  herbivores c.  primary carnivores d.  top carnivores

17. Given the amount of sunlight that hits the plants on our planet, and the ability of plants for rapid growth and reproduction, how come we aren’t all hip deep in dead plants?

 

Citation(s):

 

Week 8 Experiment Grading Rubric

Component Expectation Points
Experiment 8 Exercise 1 Correctly conducts experiment, records data (Table 1) and generates two graphs. 8 pts
Experiment 8 Exercise 1 Demonstrates an understanding competition between species and the effect it has on population growth (Questions 1-4). 10 pts
Experiment 8 Exercise 2 Develops an appreciation of the diversity of ecosystems around the globe and understands the environmental conditions that lead to their development (Tables 2 and 3). 8 pts
TOTAL  

 26 pts

Updated October 2013

 
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Osmosis WEEK 3 EXPERI

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Please submit to the Week 3 Experiment dropbox no later than Sunday midnight.

SUMMARY OF ACTIVITIES FOR WEEK 1 EXPERIMENT ASSIGNMENT

 

·         Experiment 3 Exercise 1 – Diffusion: Movement of Solutes across a Membrane

·         Experiment 3 Exercise 2 – Osmosis: Movement of Water across a Membrane

 

Experiment 3 Exercise 1: Diffusion – Movement of Solutes across a Membrane

We will be using dialysis tubing to simulate a semipermeable membrane. This tubing allows small molecules (e.g., water, ions, glucose) to pass while preventing large molecules (e.g., macromolecules like proteins, starch, glycogen) from moving across.  Be sure you have read over the suggested material before starting this exercise and that you have reviewed the following animations:

Experimental Design

 

A.      The dialysis bag we will use is permeable to water and small molecules (e.g., less than 500 g/mol) and impermeable to large molecules (e.g., more than 500 g/mol).

B.      The dialysis bag is filled with a mixture of glucose (molecular weight = 180 g/mol) and protein (molecular weight = 10,000 g/mol) dissolved in water. A small subsample of the dialysis bag contents is saved and will be used in Step 4.

C.      The dialysis bag is then placed into a beaker of water. A small subsample of beaker water is also saved and is to be used in Step 4 as well.

The presence or absence of glucose and protein will be determined using indicators. Indicators change colors in the presence certain materials. The two tests that we’ll use are the Benedict’s test for simple sugars (e.g., glucose) and theBiuret test for the presence of proteins.

·         If glucose is present, the Benedict’s indicator will turn green. If no glucose is present, the solution will be blue.

·         If protein is present, the Biuret indicator will turn violet.  If the solution remains clear, then no protein is present.

4.    The subsample of dialysis bag solution and the beaker water are tested for the presence of glucose and protein. SeeTable 1 below for the results.

5.    The dialysis bag is then left in the beaker of water for 60 minutes.

6.    At the end of 60 minutes, the dialysis bag solution and the beaker water are again tested for the presence of glucose and protein. See Table 1 below for the results.

 

Table 1. Results of testing of the dialysis bag and beaker contents at the beginning and end of the Experiment.

 

Questions

1.    Summarize the results regarding the presence (+) or absence (-) of glucose and protein in the dialysis bag and beaker in Table 2 below (4 pts):

 

 

2.    Explain the movement or lack of movement of protein and glucose across the dialysis bag membrane (4 pts)

3.    Which solution, that in the bag or that in the beaker, is hypotonic compared with the protein solution (2 pts)?

4.    What factors affect the movement of molecules across a semipermeable membrane? Which factor plays the greatest role in biological systems (4 pts)?

 

5.    Briefly explain what active transport is and how it differs from passive transport, especially in terms of concentration gradients (4 pts).

 

 

 

Experiment 3 Exercise 2: Osmosis – The Movement of Water across a Membrane

 

Before starting, let’s see what you know about the terms hypotonic, isotonic and hypertonic. Examine the diagrams below. Note that the small green circles represent dissolved solutes like salt, glucose, and amino acids. You can assume that the additional space surrounding the solutes is water and that the tan area is INSIDE the cell.

 

Question

 

1.      Define each term below in terms of solute concentration outside compared to the inside of the cell. You do not need to explain which direction water will move (3 pts).

a.      Hypotonic –

b.      Isotonic –
c.       Hypertonic –

 

Procedure

1.    Open the following website to get started:

The Biology Place. No Date. Osmosis: Movement of Water across Membranes
http://www.phschool.com/science/biology_place/biocoach/biomembrane1/osmosis.html

B.      Read over the information presented and then Click on 

C.      Then, Click on .  Read through the information presented and be sure to click on Animate beneath the illustration.

2.      What concentration of salt is isotonic to animal cells (1 pts)?

 

3.      When cells are in isotonic solution, is there movement of water into or out of the cell?  If so, describe this movement (3 pts).

 

  1. Click on  .

    E.      Read through the information presented and be sure to click on Animate beneath the illustration. When ready, answer the following question.

 

 

4.      Describe the net movement of water molecules when cells are placed in a hypotonic solution.  Explain why water moves this way (3 pts).

Procedure (continued)

G.     Read through the information presented and be sure to click on Animate beneath each of the illustrations. Answer the following questions. Your answers should incorporate the terminology used in the animations.

5.      What happens to an animal cell when placed in a hypotonic solution (2 pts)?

 

 

6.      What happens to plant cells when placed in a hypotonic solution? What accounts for the difference in outcomes between animal cells and plant cells (3 pts)?

 

 

Procedure (continued)

8.    Click on  

I.     Then,  Read through the information presented and be sure to click on Animate beneath the illustration. Answer the following question.

 

7.      Describe the net movement of water molecules when cells are placed in a hypertonic solution.  Explain why water moves this way (3 pts).

 

Procedure (continued)

10.  Click on

K.      Read through the information presented and be sure to click on Animate beneath the illustration. Answer the following questions.

8.    Compare and contrast what happens to plant and animal cells when placed in a hypertonic solution. Be sure to use proper terminology (4 pts).

9.    Based on what you learned in this exercise, explain why salt might make a good weed killer (3 pts).

 

Week 3 Experiment Grading Rubric

 
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Lab Enzymes

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Your Full Name:

 

UMUC Biology 102/103

Lab 4: Enzymes

INSTRUCTIONS:

 

·        On your own and without assistance, complete this Lab 4Answer Sheet electronically and submit it via the Assignments Folder by the date listed intheCourse Schedule (under Syllabus).

·        To conduct your laboratory exercises, use the Laboratory Manual located under Course Content. Read the introduction and the directions for each exercise/experiment carefully before completing the exercises/experiments and answering the questions.

·        Save your Lab 4Answer Sheet in the following format:  LastName_Lab4 (e.g., Smith_Lab4).

·        You should submit your document as a Word (.doc or .docx) or Rich Text Format (.rtf) file for best compatibility.

Pre-Lab Questions

 

  1. How could you test to see if an enzyme was completely saturated during an experiment?

 

  1. List three conditions that would alter the activity of an enzyme. Be specific with your explanation.

 

  1. Take a look around your house and identify household products that work by means of an enzyme. Name the products, and indicate how you know they work with an enzyme.

 

 

Experiment 1: Enzymes in Food

This experiment tests for the presence of amylase in food by using Iodine-Potassium Iodide, IKI. IKI is a color indicator used to detect starch. This indicator turns dark purple or black in color when in the presence of starch. Therefore, if the IKI solution turns to a dark purple or black color during the experiment, one can determine that amylase is not present (because presence of amylase would break down the starch molecules, and the IKI would not change color).

concept_tab_2

Materials

(1) 2 oz. Bottle (Empty)
(1) 100 mL Graduated Cylinder
30 mL Iodine-Potassium Iodide, IKI
Permanent Marker
Ruler
2 Spray Lids
30 mL Starch (liquid)
*Cutting Board

  

*2 Food Products (e.g., ginger root, apple, potato, etc.)
*Kitchen Knife
*Paper Towel
*Saliva Sample
*Tap Water

*You Must Provide

 

Procedure:

  1. Remove the cap from the starch solution. Attach the spray lid to the starch solution.
  2. Rinse out the empty two ounce bottle with tap water. Use the 100 mL graduated cylinder to measure and pour 30 mL of IKI into the empty two ounce bottle. Attach the remaining spray lid to the bottle.
  3. Set up a positive control for this experiment by spraying a paper towel with the starch solution. Allow the starch to dry for approximately one hour (this time interval may vary by location).
  4. In the mean time, set up a negative control for this experiment. Use your knowledge of the scientific method and experimental controls to establish this component (hint: what should happen when IKI solution contacts something that does not contain starch?) Identify your negative control in Table 1.

Note: Be sure to space the positive and negative controls apart from each other to prevent cross-contamination.

  1. When the starch solution has dried, test your positive and negative controls. This step establishes a baseline color scale for you to evaluate the starch concentration of the food products you will test in Steps 7 – 11. Record your results in Table 1.
  2. Select two food items from your kitchen cabinet or refrigerator.
  3. Obtain a kitchen knife and a cutting board. Carefully cut your selected food items to create a fresh surface.
Figure 3: Sample set-up.
Figure 3: Sample set-up.
  1. Gently rub the fresh/exposed area of the food items on the dry, starch-sprayed paper towel back and forth 10 – 15 times. Label where each specimen was rubbed on the paper towel with a permanent marker (Figure 3).
  2. Wash your hands with soap and water.
  3. Take your finger and place it on your tongue to transfer some saliva to your finger. Then, rub your moistened finger saliva into the paper towel. Repeat this step until you are able to adequately moisten the paper towel.

    Note: You should always wash your hands before touching your tongue! Alternatively, if you do not wish to put your hands in your mouth, you may also provide a saliva sample by spitting in a separate bowl and rubbing the paper towel in the saliva. Be sure not to spit on the paper towel directly as you may unintentionally cross-contaminate your samples.

  4. Wait five minutes.
  5. Hold the IKI spray bottle 25 – 30 cm away from the paper towel, and mist with the IKI solution.
  6. The reaction will be complete after approximately 60 seconds. Observe where color develops, and consider what these results indicate. Record your results in Table 1.
Table 1: Substance vs. Starch Presence
Substance Resulting Color Presence of Starch?
Positive Control: Starch    
Negative Control: Student Must Select    
Food Product:    
Food Product:    
Saliva:    

 

Post-Lab Questions

1.      What were your controls for this experiment? What did they demonstrate? Why was saliva included in this experiment?

 

2.      What is the function of amylase? What does amylase do to starch?

 

3.      Which of the foods that you tested contained amylase? Which did not? What experimental evidence supports your claim?

 

 

 

4.      Saliva does not contain amylase until babies are two months old. How could this affect an infant’s digestive requirements?

 

 

 

5.      There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. Research to determine what this enzyme is called. What substrate does it act on? Where in the body does it become activated, and why?

 

6.       Digestive enzymes in the gut include proteases, which digest proteins. Why don’t these enzymes digest the stomach and small intestine, which are partially composed of protein?

 

 

Experiment 2: Effect of Temperature on Enzyme Activity

Yeast cells contain catalase, an enzyme which helps convert hydrogen peroxide to water

Figure 4: Catalase catalyzes the decomposition of hydrogen peroxide to water and oxygen.
Figure 4: Catalase catalyzes the decomposition of hydrogen peroxide to water and oxygen.

and oxygen. This enzyme is very significant as hydrogen peroxide can be toxic to cells if allowed to accumulate. The effect of catalase can be seen when yeast is combined with hydrogen peroxide (Catalase: 2 H2O2 → 2 H2O + O2).

In this lab you will examine the effects of temperature on enzyme (catalase) activity based on the amount of oxygen produced. Note, be sure to remain observant for effervescence when analyzing your results.

concept_tab_l

Materials

(2) 250 mL Beakers
3 Balloons
30 mL 3% Hydrogen Peroxide, H2O2
Measuring Spoon
Permanent Marker
Ruler
20 cm String

  

3 Test Tubes (Glass)
Test Tube Rack
Thermometer
Yeast Packet
*Hot Water Bath
*Stopwatch

*You Must Provide

 

Procedure

  1. Use a permanent marker to label test tubes 1, 2, and 3. Place them in the test tube rack.
  2. Fill each tube with 10 mL hydrogen peroxide. Then, keep one of the test tubes in the test tube rack, but transfer the two additional test tubes to two separate 250 mL beakers.
  3. Find one of the balloons, and the piece of string. Wrap the string around the uninflated balloon and measure the length of the string with the ruler. Record the measurement in Table 2.
  4. Create a hot water bath by performing the following steps:
    1. Determine if you will use a stovetop or microwave to heat the water. Use the 100 mL graduated cylinder to measure and pour approximately 200 mL of water into a small pot or microwave-safe bowl (you will have to measure this volume in two separate allocations).
    2. If using a stovetop, obtain a small pot and proceed to Step 4c. If using a microwave, obtain a microwave-safe bowl and proceed to Step 4e.
    3. If using a stove, place a small pot on the stove and turn the stove on to a medium heat setting.
    4. Carefully monitor the water in the pot until it comes to a soft boil (approximately 100 °C). Use the thermometer provided in your lab kit to verify the water temperature. Turn the stove off when the water begins to boil. Immediately proceed to Step 5.

      CAUTION: Be sure to turn the stove off after creating the hot water bath. Monitor the heating water at all times, and never handle a hot pan without appropriate pot holders.

    5. If using a microwave, place the microwave-safe bowl in the microwave and heat the water in 30 second increments until the temperature of the water is approximately 100 °C. Use the thermometer provided in your lab kit to verify the water temperature. Wait approximately one minute before proceeding to Step 5.
  5. Place Tube 1 in the refrigerator. Leave Tube 2 at room temperature, and place Tube 3 in the hot water bath.

Important Note: The water should be at approximately 85 °C when you place Tube 3 in it. Verify the temperature with the thermometer to ensure the water is not too hot! Temperatures which exceed approximately 85  °C may denature the hydrogen peroxide.

  1. Record the temperatures of each condition in Table 2. Be sure to provide the thermometer with sufficient time in between each environment to avoid obscuring the temperature readings.
  2. Let the tubes sit for 15 minutes.
  3. During the 15 minutes prepare the balloons with yeast by adding ¼ tsp. of yeast each balloon. Make sure all the yeast gets settled to the bulb of the balloon and not caught in the neck. Be sure not spill yeast while handling the balloons.
  4. Carefully stretch the neck of the balloon to help ensure it does not rip when stretched over the opening of the test tube.
  5. Attach the neck of a balloon you prepared in step 8 to the top of Tube 2 (the room temperature test tube) making sure to not let the yeast spill into the test tube yet. Once the balloon is securely attached to the test tube lift the balloon and allow the yeast to enter the test tube. Tap the bulb of the balloon to ensure all the yeast falls into the tube.
  6. As quickly and carefully as possible remove the Tube 1 (cold) from the refrigerator and repeat steps 9 – 10 with Tube 1 using a balloon you prepared in step 8.
  7. As quickly and carefully as possible remove Tube 3 (hot) from the hot water bath and repeat steps 9 – 10 with Tube 3 using a balloon you prepared in step 8.
  8. Swirl each tube to mix, and wait 30 seconds.
  9. Wrap the string around the center of each balloon to measure the circumference. Measure the length of string with a ruler. Record your measurements in Table 2.
Table 2: Balloon Circumference vs. Temperature
Tube Temperature (°C) Balloon Circumference (Uninflated; cm) Balloon Circumference (Final; cm)
1 – (Cold)      
2 – (RT)    
3 – (Hot)    

 

 

Post-Lab Questions

1.      What reaction is being catalyzed in this experiment?

2.      What is the enzyme in this experiment? What is the substrate?

3.      What is the independent variable in this experiment? What is the dependent variable?

4.      How does the temperature affect enzyme function? Use evidence from your data to support your answer.

 

5.      Draw a graph of balloon diameter vs. temperature. What is the correlation?

 

6.      Is there a negative control in this experiment? If yes, identify the control. If no, suggest how you could revise the experiment to include a negative control.

 

7.      In general, how would an increase in substrate alter enzyme activity? Draw a graph to illustrate this relationship.

 

8.      Design an experiment to determine the optimal temperature for enzyme function, complete with controls. Where would you find the enzymes for this experiment? What substrate would you use?

 

 
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