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THE SCIENTIFIC METHOD - BLACK BOX EXPERIMENT Science and the methods of science are not mystical or mysterious. Modern science attempts to understand the natural world in a way that will increase the confidence in its concepts, and that can be evaluated and accepted by other scientist, despite their area of expertise. The general procedure followed by scientists in acquiring and evaluating new information is called the Scientific Method. There are several generalized steps to the Scientific Method,
"BLACK BOX" EXPERIMENT
In real science you cannot always test directly for a substance, process, or event, but must test indirectly. For instance, a chemical in a chemical pathway may occur in amounts too small to be tested for directly, or exist for only a fraction of a second, but its presence might be tested for indirectly. Field observations or experiments may be difficult to perform, so laboratory experiments that mimic the field conditions are performed to get an estimate about how the organism functions in nature. The "black box" experiment is a way of using your senses to determine indirectly what is in the boxes without actually being able to observe the objects. The ten lettered and wrapped boxes each contain an item of laboratory equipment. Examples of the possible contents are also provided. Your causal question is "what is in each box?" Using a hypothesis that each box contains a 50 ml (milliliter) beaker, you will test the hypothesis to determine if it is correct. If you determine the original hypothesis is not supported by the evidence, you will need to formulate a new one. Record you results below and in the chart on the blackboard. You may be asked to work in small groups. "BLACK BOX" EXPERIMENT DATA Record the letter or number of the box you are working with, and if you determine that a 50 ml beaker is not in the box, formulate a new hypothesis for what you do believe is in the box and list the evidence you have gathered to support your hypothesis. For example: Box 1 Hypothesis 1 - the box contains a 50 ml glass beaker. Prediction A - If box 1 contains a beaker, then it should sound like a beaker put into an empty box. Prediction B - If box 1 contains a beaker, then it should weigh the same as a beaker put into an empty box. Result A - the object in Box 1 did not sound like the beaker put in an empty box. It sounded softer. Result B - the object in Box 1 weighed 57 g, and the control box with a beaker weighed 110 g. Conclusion - reject hypothesis 1. Hypothesis 2 - the box contains red rubber tubing. Prediction C - (etc.)
Answer these questions after deciding on the contents of all boxes:
What additional tests could be performed to determine what is in the boxes without opening them?
How much support can be given to any one hypothesis made by a student or a group?
Do the results from all the groups in the lab help support any single hypothesis?
The professor will demonstrate the magic candle phenomenon by performing the following. Water will be added to a finger bowl so that it stands about 4 or 5 cm deep in the bottom. A candle will be stuck in a ball of clay and stood upright in the middle of the container. The candle will be lit, and a cylinder (i.e. a test tube), smaller in diameter than the glass container, will be lowered down over the candle. As the cylinder is lowered with a steady motion, what do you actually observe?
What is the difference between an observation and an hypothesis?
What are the questions raised by this phenomenon?
What are all possible explanations (hypotheses) to explain these phenomena?
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6. What tests can be done to evaluate any or all of the explanations? What were the results of the experiments? 1.
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What has this experiment proven about the phenomena?
The ability to use a microscope is very important in science. This exercise is designed to develop an understanding of the procedures, safety rules, and capabilities of using the microscope. The Microscope is an instrument constructed of a series of lenses that is used to magnify the size of very small objects. The kind of microscope most commonly used in biology laboratories is the Binocular Compound Light Microscope. Binocular refers to the two eyepieces (you can use both eyes), and compound means that there are two sets of lenses used for magnification. A Light Microscope uses electromagnetic radiation in the visible range to illuminate the objects under the lenses, while a Electron Microscope would use electrons to create an image. The ability to separate or distinguish between small objects that are close together is called Resolution. The resolving power of a microscope is related to the wavelengths, or type, of electromagnetic radiation used to illuminate the object. A light microscope has a maximum resolution of 1500x. Electrons occur at much smaller wavelengths than visible light and therefore Electron Microscopes have a resolution power wp to 1,000,000x.
C. Using the microscope.
ALWAYS FOCUS WITH THE STAGE MOVING AWAY FROM THE LENS. 5. Center the specimen in the field of view (the area seen while looking through the microscope), and move the low power lens into position until it "clicks" into place while watching from the side to ensure the lens does not hit the slide. Focus with the fine adjustment knob. These microscopes are parfocal, which means when the specimen is in focus under one lens it should be approximately in focus under all lenses. 6. Again, center the specimen in the middle of the field of
7. NEVER, NEVER USE THE OIL EMERSION OBJECTIVE LENS without the implicit instructions from the Professor!! 8. When finished with the microscope turn the light source off
For the scanning lens (4x) this is 4 x 10 = 40.
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POND ECOSYSTEMS
In this laboratory the class will be starting an ecological experiment that will be observed throughout the semester. Ecology is the study of the interrelationships between living organisms and their non-living environment. Pond ecosystems will be used as models for the interactions that occur in natural ecosystems, and how they can be disturbed by human impact. An ecosystem is the sum of biotic (living) and abiotic (non-living) interrelationships in a defined area. The ponds will be created by adding 500 ml of pond mud and 1500 ml of pond water to large glass jars. After the mud has settled to the bottom of the jars they may be examined for the types of organisms normally found in a pond ecosystem. Although water may be taken from any part of the jar for making wet mounts, most organisms will be found at the surface, along the sides of the jars, and at the bottom in the upper surface of the mud. Using keys provided by the instructor, identify and draw as many of the organisms from your sample as possible. Be sure to look at samples of other students, especially if they got their sample from other parts of the jar. Note the relatively abundance of each type of organism.
Every living cell, in order to maintain its existence, must take in energy and minerals, and remove wastes. The cell structure that has the function of regulating molecules entering and leaving the cell is the cell membrane. Some molecules passing through the membrane do so due to a purely physical process that does not require energy - diffusion. Diffusion is the movement of a molecule from an area of its high concentration to an area of its low concentration, and each molecule moves independently of all other molecules in the system. The movement of molecules through a differentially permeable membrane, such as a cell membrane, have special terms. The movement of solute molecules (substances dissolved in a solvent) through a membrane by diffusion is called dialysis. Solutes that can pass easily through the membrane move solely due to their concentration gradient, from high to low concentration. The movement of water (a solvent) through a membrane is called osmosis. Its movement follows the basic principles of diffusion, but its concentration is affected by the number of solutes dissolved in it. Solute molecules dissolved in a solvent lowers the concentration of the solvent. The affects of the solvent can be counteracted by creating pressure. This can occur in cells with a cell wall, such as plant cells. In this laboratory you will be investigating the principles of diffusion, and practicing the application of the scientific method. Problem:
Hypothesis:
Methods:
Results:
Conclusions:
All life on earth depends on the heredity information stored in the nucleus of each cell in the form of deoxyribonucleic acid (DNA). The structure of DNA is the same in all living organisms on earth. The section of the DNA that codes for one specific polypeptide is called a gene. Other types of nucleic acids, ribonucleic acid (RNA), are used to transport the code or to assemble a polypeptide. In this laboratory you will investigate the molecular structure of DNA and how it is used to code for a specific product, a polypeptide. In this laboratory plastic beads will be used to simulate the molecular building blocks of DNA and RNA, and to model their structure and function. The colors of the beads will be used to distinguish different molecular subunits. The color key will be:
White = sugar [deoxyribose or ribose] Orange = phosphate [pink may also be used] Red = adenine (A) --- Blue = thymine (T) | Yellow = cystine (C) |--- nitrogen bases Green = guanine (G) | Purple = uracil (U) --- A. The Structure of DNA. The basic building blocks of DNA and RNA are nucleotides, so to make DNA you must first make some nucleotides. A nucleotide is composed of a phosphate + a sugar + a nitrogen base. To make a model of a nucleotide take a red bead (nitrogen base) and stick it into the side of a white bead (sugar), and then stick the knob of the white bead into an orange (phosphate) bead. The knob of the phosphate should be sticking up and the nucleotide should look like: Now make other nucleotides using blue (thymine), yellow (cystine) and green (guanine) beads for the nitrogen bases. Make the number of each nucleotide as instructed by your professor. To make a strand of DNA you will need to connect the nucleotides together. Lay a nucleotide containing adenine on the table with the phosphate pointing the left, and the adenine pointing down. Position a nucleotide with thymine to the right of the first one and oriented in the same manner. Push the knob of the phosphate of the thymine nucleotide into the sugar of the adenine nucleotide.
Add to the strand in the same manner so that the sequence of bases is: A-T-G-T-G-T-T-A-C-A-T-C-C-A-A-A-A-C-T-G-C-C-C-G-C-T-A-G-G-A-T-A-G
This is the coding strand of DNA, the one that actually carries the code and is the gene.
The other strand of DNA (anti-coding stand) is complementary to the coding strand, in that wherever an A occurs in one, a T occurs in the other, and where a C occurs in one, a G occurs in the other. So where first nucleotide of the coding stand contains adenine, the first nucleotide of the anti-coding strand will be a nucleotide containing thymine. The other difference is that the phosphate will stick-out in the opposite direction. The First Nucleotide will contain thymine:
The second nucleotide will contain adenine.
Make a complete strand with the sequences of bases: T-A-C-A-C-A-A-T-G-T-A-G-G-T-T-T-T-G-A-C-G-G-G-C-G-A-T-C-C-T-A-T-C
Take the two strands of DNA and lay them side-by-side so that the A's match with T's and C's with G's.
Connect the bases using the clear or black dumbbell shaped plastic pieces. These represent hydrogen bonds.
If you gently pick the structure up and twist it slightly you will have a two strands of DNA with a helical (twisted) shape...a double helix of nucleotides". NOTE:
1) the strands were made with nucleotides as building blocks.
2) the sugars and phosphates form a "backbone" for the bases.
3) the two stands are connected by the nitrogen bases.
B. Gene Expression.
The heredity information, or blueprint for polypeptides, is the DNA which is located in the nucleus, but the polypeptides are assembled at ribosomes which occur in the cytoplasm. To get the proper code to make a polypeptide to the ribosome a copy must be made that can carry the code from the nucleus to the ribosome. This is accomplished by RNA.
Make the appropriate RNA nucleotides as instructed by your professor. NOTE: uracil will be used instead of thymine. Nucleotides of RNA are made exactly like DNA nucleotides, a base is added to a sugar and a phosphate, except the sugar is ribose instead of deoxyribose.
Your professor will instruct you on the completion of the process. Table 1: The 20 amino acids found in proteins. PRINTOUT Table 2: Genetic code in RNA, consisting of 64 triplet combinations and their corresponding amino acids. PRINTOUT
When researches first discovered the properties of genes, they believed that each characteristic (or trait) had one gene, and that each gene was expressed in only one way. In reality, most genes found in living organisms either code for more than one characteristic, are part of a group of genes that are all required for one characteristic, have multiple alleles, and/or interact with other genes in complex mechanisms. Humans do have around 8,000 simple, dominant/recessive single gene traits. This laboratory will investigate the expression of a few of these genes and allow you the opportunity to determine their own individual genotype for each trait. The class can also determine if the frequency of a trait for the class is what is predicted by mendelian genetics. Determine your genotype for each of the following traits. The professor will give you information so that you can determine if you express the dominant or recessive form of the trait. A distinct ear lobe (unattached) is dominant to one that is attached (recessive). Widow's peak - A point of hair in the middle of the forehead is dominant to a straight line of hair (recessive). Bent little finger - holding your hands together in front of your face with the palms facing you and the little fingers side-by-side, see if the little fingers bend away from each other (dominant) or are straight throughout their length (recessive). Short second finger - with your hands flat on a table, a 2nd finger that is shorter than the 4th finger is a dominant trait. If the 2nd finger is equal to, or longer than the 4th finger, you have the recessive trait. Hairy knuckles - having hair on the middle joint of a finger is a dominant trait, and each finger is a different gene. Hairless middle knuckle is recessive. Grasp you hands together interlacing your fingers. Your left thumb is on top is a dominant trait, and right thumb on to is recessive. Hitchhikers' thumb - in the relaxed condition, a straight thumb is the dominant condition, and a thumb that is bent back toward the wrist is recessive. Having freckles is a dominant condition, and freckless is recessive. Curly hair is a homozygous dominant phenotype (DD). Wavy hair is heterozygous (Dd). Straight hair is recessive (dd). Tasters - the ability to taste certain chemicals [sour, bitter, or sweet] are dominant traits, and no taste is recessive.
The flower is the specialized reproductive structure of Anthophyta (Angiosperms) plants which gives rise to fruit and seeds. The stalk that connects the flower to a stem is called a pedicel. The flower parts are attached to the enlarged pedicel tip that is celled the receptacle. The flower parts are usually arranged in a series of 'whorls' or circles with one within another.
A complete flower consists of the following, from the outside most whorl inward:
Considerable variations in shape, size, and color of flowers and flower parts are obvious. A selection of flowers is may be provided. Identify and count the various flower parts.
The ovule(s) found within the ovary contain a female reproductive cell (egg) that may be fertilized by a sperm from the pollen. The developing embryo produces hormones that cause the ovule to develop into a seed, and the ovary matures into the fruit. The seed contains the embryo. The fruit is the dispersal mechanism to get the seed away from the parent plant to prevent competition. The fruit may be formed from one or more than one ovary or flower. Simple fruit are produced from one ovary of one flower. Most fruit are of this type and there are many sub-types. Aggregate fruit are formed from many ovaries of one flower. And Multiple fruit are formed from the ovaries of many flowers fusing together into one fruit.
On the following page is an identification key to distinguish between fruit types. Key out (identify) the fruit provided by the professor. Dichotomous Key for Common Fruit
1. Fruit from one ovary of one flower ........[Simple Fruit].... 2
forming a pod ....................................... Legume
10. Dehiscent along two sutures ........................ Legume
This laboratory will use a very simple model to illustrate the process of natural selection. The model consists of a brightly colored cloth representing the environment, construction paper dots that represent prey organisms with only one variable characteristic - color, and a student that will act as a predator and 'eat' the prey.
PROCEDURE:
The class will decide what species of predator and prey are being observed, real or imaginary (i.e. eagles and rabbits).
Each group of 3-5 students will be given a cloth 'environment' and eight vials of colored dots. One person in the group will be designated as the 'predator', and they will leave the group until the environment is ready. The other people in the group will count out 10 of each color of dots (80 total), and randomly distribute them throughout the cloth environment. The group will also predict the order of prey colors from the one that the predator is most likely to eat to the one least likely to be eaten.
The predator will then return to the environment and begin to 'eat' the prey by picking them up one by one from the environment and placing them in a pile to one side (their nest). The predator will eat 60 prey and then stop.
The group will then count the surviving prey on the cloth and record the numbers by color. [It is very important that exactly 60 prey are eaten, and 20 remain on the cloth!].
The surviving 20 prey will then reproduce, with each prey organism making 3 offspring. For example, suppose there were 10 black, 7 red, and 3 white prey surviving the predator. The 10 black prey would make 30 black offspring, the 7 red would make 21 red, and the 3 white would make 9 white offspring. [The total for offspring must add up to 60!]. The 20 survivors and their 60 offspring [80 total] will then be randomly distributed on the cloth environment, and the predator will again eat 60 prey.
The group will then record the number and colors of the 20 survivors, the survivors will make 3 offspring each, and the predator will feed again.
When your group completes 4 feeding cycles, the numbers and colors of surviving prey will be recorded on the blackboard. Also record the feeding round that any of the prey colors became 'extinct'.
DISCUSSION:
Did the outcomes for each environment match the predictions?
Did different groups with the same environment have the same results? If not why?
Did the different environments have the same outcomes?
What factor is actually selecting for, or against, a specific color of prey?
What other characteristics might the prey have to aid in their survival?
What would be the affect if each color of prey had a different reproductive rate (i.e. black produced 5 offspring, and red only 1)?
THE EVIDENCES OF ORGANIC EVOLUTION
A. The Molecular Record:
monkeys ___ dogs ___ birds ___ frogs ___ lampreys ___
Does this pattern fit that predicted by evolution?
B. Embryonic Development.
C. Homologous and Analogous Structures.
D. Vestigial Organs.
Examine photos or examples of other vestigial organs.
E. The Fossil Record.
This material is used with the permission of Dr. Doug Jeffries. |
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