Category: 1st Semester

 

Human Hand Adaptation

Introduction:        Living things have bodies that are adapted for the places they live and the things they do. Fish have gills so that they can remove oxygen that is dissolved in water. Most plants have green leaves which contain chlorophyll so that they can make food. Jellyfish have stinging cells to capture prey. Birds have hollow spongy bones so that they will be light enough to fly. Arctic animals have layers of fat and thick coats of fur to keep warm in the frigid Arctic climate. There are hundreds of examples of ways that organisms are adapted for a successful lifestyle.       Humans, too, are adapted for the things they do. One of our adaptations is our hand. Humans, as well as monkeys, gorillas, and other primates, have a hand that can grasp objects. We are able to grasp objects because of our opposable thumb. When students first hear or read about the opposable thumb during discussions of human evolution, they may perceive it as an anatomical fact with little seeming importance. In this activity, students will discover which of their simplest daily activities are possible only because of their opposable thumbs, which activities take longer without the use of an opposable thumb, and what sort of human activities would not be likely in the absence of an opposable thumb.   In this lab exercise, you will perform several common actions. Then you will change your hand so that it resembles that of a non-primate animal. You will determine whether or not you can successfully perform the same actions. This will demonstrate how the human hand is adapted for the actions it performs. You will work with a partner to do this exercise.   Materials: (per group)

• masking tape
• scissors
• paper clips
• zip-lock storage bag
• plastic fork and knife
• small amounts of food items to be cut
• pencil
• jar with screw-on lid
• paper
• roll of tape
• balloons
• comb
• book
• lace-up shoe
• clock with a second hand
• Piece of yarn or string
• balloon
• clothes with zippers & buttons

Procedure: Using masking tape, have your partner tightly tape each of your thumbs to the palm of the hand. Then, try to complete the tasks that are listed below. Be careful not to use your thumbs. Have your partner record on your data table how long it takes to do each task with your thumb taped and then with your thumb free. If an activity takes longer than 2 minutes, record the event as unsuccessful . After completing each item, write out the answers to the following questions:

• Is the task more difficult with or without an opposable thumb?
• How did you have to change your usual technique in order to complete this task?
• Do you think organisms without opposable thumbs would carry out this task on a regular basis? Why or why not?

Tasks:

1. Pick up a single piece of paper. Put it down on your desk.
2. Pick up a pen or pencil from the table top. Use it to write your name on the piece of paper.
3. Open a book. Turn single pages in the book.
4. Unscrew a bottle cap or jar cover.
5. Use a fork and knife to cut a food item into small pieces.
6. Tear off a small piece of tape.
7. Turn on the water faucet. (Complete activity #8!) Turn it off.
8. Moisten a paper towel and wash and dry the desktop.
9. Sharpen a pencil.
10. Cut a circle out of a piece of paper using scissors.
11. Pick up all the scraps from activity #10 and throw them into the recycling box.
12. Comb your hair.
13. Open a door.
14. Pick up one paper clip. Clip a pile of papers together.
15. Tie your shoelaces.
16. Button several buttons.
17. Zip up your jacket.
18. Blow up a balloon and tie it.
19. Tie a knot in a piece of string.
20. Close a zip-lock bag.

Data:

 

Task	Time Taken for Event:		Task Difficulty With Taped Thumb (More/Less)	Modification Made to complete Task
Thumb Free	Thumb Taped
Pick up paper
Write name
Turn book pages
Open jar
Use knife & fork
Tear off tape
Turn faucet on & off
Clean desk top
Sharpen a pencil
Cut out a circle
Pick up the scraps of paper
Comb hair
Open door
Clip papers together
Tie shoelaces
Button & unbutton garment
Use zipper
Blow up & tie balloon
Knot string
Close zip-lock bag

Conclusion:   1. Explain why dog and cat paws are not adapted for doing the six actions you tested.     2. What are cat and dog paws adapted for?     3. Describe how your hand is adapted for doing the actions you tested.       4. You have an opposable thumb. Explain what this means.     5. Why do you feel that human hand adaptations have helped to make humans such a successful species on earth?

 

Chromatography of Inks

Introduction:

One of the main jobs of biochemists is to unravel the complexities of chemical compounds and reduce them to their individual components.  The term chromatography comes from two Greek words, “chromat” meaning color and the word “graphon” meaning to write.  Separation of the components of chemical compounds can be done by using several methods. Liquids can be separate by High Performance liquid Chromatography (HPLC), while the components of gases are separated by Gas Chromatography.  Chromatography is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.

Chromatography was first used to separate pigments (colors) in leaves, berries, and natural dyes. Paper chromatography is a technique used to separate, isolate, and identify chemical components of a compound. In paper chromatography, the solid surface is the cellulose fibers in the chromatography paper.  A solvent or developer (water, alcohol, or acetone) is placed in the bottom of the chromatography chamber. The paper acts as a wick to pull the solvent up the paper. The solvent front will “wick” up the chromatography paper by capillary action.  A minute drop of the ink or chemical mixture to be separated is placed near the bottom of the strip of chromatography paper, but slightly above the level of the solvent in the chamber.  As the solvent passes over the drop of ink, the components of the ink dissolve in the solvent. Because the components of the ink do not all dissolve at the same rate, as the components of the mixture move upward, they show up as colored streaks.  The separated substances on the chromatography paper form a color pattern called a chromatogram.

To determine the rate of migration for each pigment or component of the ink, the Rf value for each pigment must be calculated. The Rf value represents the ratio of the distance a pigment moved on the chromatogram relative to the  distance the solvent front moved. Each pigment or compound will have a unique Rf value that scientists can use to identify the substance. The Rf value is calculated using the following formula:

Rf = distance traveled by the compound / distance traveled by the solvent

Objective:

Use the process of paper chromatography to separate the pigments in various markers and then determine the Rf value for each color on your chromatogram.

Materials:

Plastic vials, paper clips, markers in assorted colors, chromatography paper, scissors, pencil

Procedure:

1. Obtain chromatography vials and chromatography strips, and different color markers so that each person in the group will have two chromatograms.
2. Cut one end of the chromatography strip to a point. The bottom of the point will mark the starting point for movement of the solvent (H2O).
3. About 2.0 centimeters from the bottom of the strip, draw a faint horizontal line with pencil. This will mark the starting point for measuring the migration distance of each color.
4. Using a different color marker for each strip, drop a dot of ink on the center of the horizontal pencil line.  Let this dry a moment & then add more ink to the dot.
5. Add a small amount of water to the bottom of the chromatography chamber. (The ink dot should be ABOVE the surface of the water.)
6. Straighten a paper clip and poke a hole through the top of your chromatography strip
7. Use the paper clip to hang the strip in your chamber. (The straighten paper clip will lay across the top of the chamber.)
8. MAKE SURE THE TIP OF THE STRIP BUT NOT THE INK IS IMMERSED IN THE WATER!
9. Notice the separation of the ink as both the solvent and ink travel up the chromatography strip.
10. Once the solvent front has neared the top of the strip, remove the strip from the chamber and lay it on a piece of paper towel.
11. Immediately mark the solvent front with a faint pencil line.
12. Immediately mark the leading edge of each color with an “x”.
13. Measure, in millimeters, the distance the solvent migrated from the tip of the strip to your solvent front pencil line.
14. Measure, in millimeters, the distance each color migrated from the point of origin (pencil line where the ink dot was placed) to the leading edge of the color (marked with an “x”.
15. Record all data in Data table 1.
16. Calculate and record the Rf value for each color using the formula below.

Rf = distance traveled by the compound / distance traveled by the solvent

Data Table 1

 

 

Questions:

1. Which color of marker did you use?

2. which color separated out first from your ink dot?

3. Why did the inks separate?

 

4. What was your solvent?

5. If you had used markers that weren’t water-soluble, how would you have had to change this lab?

 

6. Why did some inks move a greater distance than others?

 

7. How do scientists use paper chromatography in their investigations?