| Unit 1 Objectives |
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| The students will learn: |
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Take a look at your hands, your hair, your eyes. Examine the roots of an onion, the leaf and branches of a maple, the mold growing on bread. Observe the colorful plumage of a cardinal or a mallard, the nose of your pet dog, the gills and fins of a fish. All of these are made up of amazing cells -- the foundation of life and the key to biotechnology.
Tiny, inconspicuous units, cells do all the work an organism needs to survive, like breathing (or metabolism), giving protection against foreign microscopic bodies, and growing. Some organisms are just one-celled, like yeast or bacteria. Most organisms are much more complex -- made up of billions of cells joined together like lace or a honeycomb.
Cells are usually specialized, just as some people are teachers, others farmers and others, scientists. Cells in different parts of the organism may have different jobs and may contain different substances.
Organisms grow by adding more cells. For instance, the trunk of a tree becomes wider as new layers of cells form new rings each year.
Clearly, there are a tremendous number of cells that constitute most types of organisms. However, constituting an organism is not simply a random act of mixing up different cells. Just as preparing a dish is not simply an ad hoc affair, but a careful combination of certain ingredients according to a recipe, so organisms are constituted out of elaborate recipes: which elements to produce, in what amounts, when to introduce them, etc.
Every cell within an organism contains the complete recipe book with all of the instructions required to assemble and sustain life in that organism. However, any individual cell within the organism will only read the recipes necessary for the functioning of that particular cell. For instance, there are genes in a Red Delicious apple that instruct the cells in the skin to produce its bright red color. Each organism has its own unique book of instructions which leads to the great diversity of life on earth. These instructions (or genes) are passed on from generation to generation.
Suppose we have one apple that is sweet but green and another that is red but sour. It is possible to combine the two and produce a variety of apple which is red and sweet. For that matter, we can produce one that is green and sour. We have created new varieties of apple by trading genetic information.
Another way of thinking about this is that we often use ingredients of one recipe in another. Of course, the result is not always tasty or what we might expect. In the same way, we cannot be sure of the results when we combine genes except after much trial and error. We will look at this process more closely in the next unit.
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| Purpose of Activity |
| Use this activity to introduce students to the cellular nature of organisms and to the idea that cells contain information that instruct their work. |
Before beginning the unit, make enough copies of the characteristics of the apple for each student to receive one trait. Introduce students to the idea that organisms are made of cells by opening up a discussion with the following questions:
Give each student a leaf. Ask the students to look at it and guess how many cells thick it is. Then, project the transparency of the cross-section of the leaf. The leaf is about 9 cells thick.
Explain that we are going to understand cells by looking at how things grow. Ask the students how a tree grows. Have them imagine a nail in a tree. Where would it be in 20 years?
Demonstrate how a tree grows from the terminal bud using shaving cream. The can represents the bud and the cream that falls is the tree the bud "leaves behind." Thus, the tree grows upwards and the nail does not move.
Next, have students form teams of three and give each team a branch. Tell them to feel for the bud. Ask the students what they think the bud does? Slice open the head of cabbage to reveal the "world's largest bud." Explain that the bud is where the cells are manufactured.
Next, ask the students:Peel off a piece of bark from a branch. Explain that the bark is like a bud that covers the tree. The bark lays down the new tree. Use the roll of paper towels to represent a tree, where new rings are added each year. Use the shaving cream to make the rings around the roll of paper towels.
Tell the children the story of how we come to have the red big apples of today.
When the pioneers arrived in this country, the only apples in North America were crab apples. They tasted so sour that the Native Peoples never ate them. Eventually, the pioneers brought seeds of edible apples, seedlings, and even small trees from their home countries. In fact, most pioneers had at least one apple tree in their yard. However, these apples were small, green, and coarse tasting compared to today's modern apples.
The only things they were good for was cider, applesauce, and baking.
It wasn't until 1810-1811, when John McIntosh discovered some young apple seedlings on his land in Ontario, Canada. Being a lover of apples, he carefully uprooted the seedlings and planted them in the garden beside his house. Eventually, the trees flourished and bore fruit in their new location. Oddly enough, one of the trees began producing the juiciest, sweetest, reddest apples that John McIntosh had ever seen. All of his neighbors wanted to taste it. Soon word of his apple spread throughout Canada and even New York. The apple became known as the McIntosh Red.
Now, divide the class into two groups. Have one group sit down. Ask them to imagine their "ideal" apple. It can be something different from what is available in the supermarket. Have them draw and color their "ideal" apple.
Meanwhile, take the second group aside. Give each student one apple characteristic that has been cut out from the first page. Set aside the taste traits for now. Tell the students that they are cells and that the pieces of paper are "instructions" so the cells know what to do. Have the students rehearse a movement that may be associated with the characteristic.
Then, prepare a table, placing chairs leaning on the table on both sides. Tell the whole class that the table is an apple bud and the children in the first group are cells. Have the children crawl through and as they emerge at the other end, shout out their characteristic and make the movement.
Now, have the first group of apple cells sit down. Repeat the activity with the other group using the remaining characteristics.
Go through the discussion questions and then offer real apples sliced to the students as a demonstration of the new apple with combined traits.
Explain that the first apple did not have any taste characteristics. But we can make a big, round, red, crunchy, juicy, and sweet apple by joining the cells of the two. This is possible because cells have instructions that can be understood by other cells.
Tell the students that as we move on, we will explore how to obtain their "ideal" apples.
This activity can be done in conjunction with the "A Tale of Two Moths" activity in Unit II.
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| Purpose of Activity |
| Use this activity to illustrate that cells have information, or genes, that make them grow into different parts of an organism. |
Before the activity, prepare the 1" squares of construction paper according to the instructions and place them in plastic bags. These are the cells. Be sure each bag contains one set of instructions and the appropriate cells. The students will work in pairs to make 5 parts of a moth separately, so there should be as many parts to make enough whole moths as pairs. Have all moths look the same except one, e.g. 10 pairs of students will form 2 different colored moths; 15 pairs of students will make 2 moths of the same color and the third a different color and so forth.
Tell the students that they are about to witness a "miracle": they will help to form an organism. In order to find out what that organism is, they will have to work with cells. Show the students the squares of construction paper.
Explain that just as the apple contains cells which make it sweet and red, etc., all organisms are made up of cells that make them what they are.
Recall that students were given papers with information on what type of cell they would be (red, sweet, etc.). In the bags, there is also a piece of paper that will tell them what the cells will be.
Have students work in pairs. Give each pair a bag with the cells and the instructions, the glue stick, and a sheet of 11" x 14" art paper.
When the students are done, ask them to figure out what has emerged. Cut out the shape of the parts and paste them together as moths on the large sheet of paper. Hang it on the wall.
Explain that the cells had instructions which told them what they would become. One moth was different because it had a different instruction for color. These instructions are known as genes. Apples and moths both have genes in their cells. They have different genes but all genes are made up of the same thing, DNA.
| Cut out these instructions: |
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| Here are your instructions: There are 20 pink cells in this bag. On your art paper, draw two curved lines in the shape of a V, 1 inch thick and about 4 inches long. Glue the cells on the line you have drawn. Use 10 cells for each curve. Cells may overlap. |
| Here are your instructions: There are 10 blue cells in this bag. On your art paper, draw a circle 2 inches wide. Glue all the cells in the circle you have drawn. Cells may overlap. |
| Here are your instructions: There are 30 black cells in this bag. On your art paper, draw a rectangle that is 7 inches long and 1 and 1/2 inches wide. Make the ends curved so you get a long oval shape. Paste all 50 cells to fill the oval. Cells may overlap. |
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| Purpose of Activity |
Use this activity to show that different cells perform different tasks. In every organism, all the cells contain a substance called DNA which "instructs" the cells on what to do. DNA is like a common language for all organisms. |
Explain that we are going to learn about how cells work together so that an organism can survive.
Before the activity, place 2 sets of marbles, pebbles, or some small object of equal number, at one end of the room. At the other end of the room, place the 2 buckets.
Divide the group into 2 equally-numbered teams.
Instruct the group that the goal is for each team to create the most amazing marble moving machine possible. Each person will be responsible for one movement and one sound. No two team members should use the same movement and sound.
Explain that each student is like a cell. The movement and sound represent the traits expressed by the cell. In order to survive, the organism has to do certain things (e.g. breathe), represented by the passing of the marbles. The cell knows what to do (which traits to express) because it has understood the "instructions."
Students may need individual instructions written out on pieces of paper to perform the movement and sound, such as:
"Stretch out your left hand in front of you and raise your right hand. Move up and down by bending your knees. Receive the marble in your left hand and make the sound of a duck."
These will need to be prepared before class. Verbal or written instructions represent genes.
Have one member from each team stand next to a set of marbles. Have the student create their movement and sound. When they are each ready with a movement and a sound, have them pick up a marble and attempt to pass it on. The student should not walk toward the bucket.
Point out that the first students are ready to pass on the marbles. Call for another student from each team to join in to receive the marble. The second student should stand at least one arm's length away from the first student and work out a unique movement and sound.
When they are ready, have a third person from each team join the line. Add a fourth, fifth, etc., until all children are in line with a gesture and sound.
Have each team practice their machine for a few minutes. Then, have each team watch the other team.
Return all the marbles to the start of the line. Have a race to see which team can pass the marbles on more quickly.
Repeat the activity but tell the students that the objective this time is not to pass the marble quickly but smoothly so that the machines work very well.
In the machines,
Lead the discussion about how each student in the machine is like a cell. The cells are connected and form one organism--the machine. Although each cell (child) has different genes (instructions) operating, and do different jobs (movements and sounds), they share common structures--heads, arms, legs, knees, etc.
In a similar way, every cell in all living things comes equipped with a master coding device: DNA. This coding device is a molecule which cells depend on for information to go about its work. DNA is like a universal language that is understood by all cells.
Recall the "Abundance of Apples" activity. The information in the cells of organisms can be exchanged so that a new organism can be formed.
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| Purpose of Activity |
| Use this activity to reinforce the understanding that organisms are made up of cells. Cells are unique and separate but they are all linked together like a honeycomb to make one organism. |
Inform the students that they are "worker bees" in a hive. Their task is to design a hive to contain the honey. Show students several types of containers and discuss their features. For example, some bottles have long necks, other containers are shallow and square.
If you are using honey, have the students describe the honey.
Inform the "worker bees" that they will design containers for honey in teams of two. They can use the paper, scissors, and rubber cement or tape.
When the containers are finished, use rubber cement or tape to hold them together to form a "honeycomb."
Explain that the containers, like the cells of the honeycomb, are like cells in a organism. Each cell is unique and separate, but are linked together to form the organism. Thus, changing the way cells work may affect the organism, for better or for worse.
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| Purpose of Activity |
| Use this activity to illustrate how genes combine to produce variations in traits |
Divide the group into teams. Inform the group that they are about to uncover the secrets of the Ingot Theobroma Cacao* (pronounced Kah Kay-O). Have students guess what it means.
*Ingot = bar, Theobroma Cacao = the cacao tree from which cocoa or chocolate is derived (In Latin, the noun is before the adjective). Distribute one candy bar, one plastic knife, and one paper plate to each team.
Have each team unwrap the bar and place it on the paper plate.
With adult present, have each team cut a piece at least 1/4 to 1/2 inch wide from the middle of the bar. Analyze the Ingot Theobroma Cacao using the Observation guidelines.
After studying the bars, mount the cross section on a piece of cardboard and cover with plastic wrap. Observations and comparisons can be attached (Optional).
For example,
Explain that the ingredients in the chocolate bars are like the genes in the cells of organisms. Different combinations of genes will produce variations. For example, human beings are made up of water, minerals, elements, etc., but genetic variation produce differences in our appearance. Some of us have blond hair, some of us have green eyes, some of us have brown skin, etc. Sometimes, the differences are subtle (a daughter that is slightly taller than her mother when full grown) and sometimes they are very obvious (a son that stands 6' 7" when both parents are 5' 6" or less).
