HSA Review
Skills and Experimental Design
SKILLS & EXPERIMENTAL DESIGN: BIOLOGY HSA REVIEW
A. True/False: Write T if the statement is true; if the statement is false, change the underlined term or phrase to make the statement true.
______1. On a microscope, the coarse adjustment knob controls the amount of light passing through the object to be viewed.
______2. In an experiment, the one and only factor that is changed by the experimenter is called the conclusion.
______3. A hypothesis is a statement that can be tested as a possible explanation for a set of observations.
______4. The maintenance of a relatively stable internal environment is called metabolism.
______5. Heredity is the production of genetically similar (or identical) offspring.
______6. On a microscope, the revolving nosepiece rotates to allow for a choice of lenses or objectives.
______7. The factors that remain the same during an experiment are the dependent variables.
______8. All living things show cellular organization in that they are composed of one cell or many cells.
______9. Homeostasis is the process of using and/or releasing energy to move and grow.
______10. A logical and organized way to solve a problem is called the scientific method.
B. Order: Place these steps in Using a Microscope in the correct order, from a
through g. The first step (a) is already identified for you.
______1. Look through the eyepiece to observe the specimen under low power. If needed, adjust the diaphragm to control the amount of light entering the field of view.
______2. Return the objective to low power and raise the body tube using the coarse adjustment knob. Remove the slide after use.
______3. Change to the high power objective after locating the specimen under low power. While looking at the specimen, use the fine adjustment knob to bring the specimen into clear focus.
______4. Raise the body tube by turning the coarse adjustment knob.
______5. Carry the microscope properly by placing one hand underneath the base and one hand grasping the arm.
______6. Place a prepared slide on a microscope so that the specimen is located over the center of the opening in the stage.
______7. Carefully place the microscope on the lab table with the arm facing you.
C. Matching Laboratory Equipment: Match the following pieces of lab equipment with the most correct function in the box on the right. Write the letters of the correct answers in the blanks to the left.
______1. graduated cylinder
______2. glass slide
______3. forceps
______4. triple-beam balance
______5. thermometer
______6. metric ruler
______7. microscope
______8. funnel
______9. Petri dish
______10. beaker
D. Small and Large Numbers
1. Complete the following table:
Decimal Notation / Scientific Notation93,000,000 / 9.3 X 107
0.000000072 / a)
b) / 2.58 X 109
c) / 6.39 X 10-10
2. A red blood cell is about 0.000007 m in length. Write this in scientific notation.
E. pH: Create a pH scale
Place the following substances on the chart below in order from most acidic to most basic: eggs (pH = 7.8); acid rain (4.9); vinegar (3.0); lemons (2.0); milk of magnesia (10.2); sodium hydroxide (13.5); sea water (8.2); milk (6.5)
Acidic Basic
F. Identifying Parts of a Controlled Experiment: For each of the following descriptions, identify: hypothesis, independent variable, dependent variable(s), control, and any factors that would need to be constant.
A scientist believes that mice exposed to microwaves will be extra strong. He decided to perform the following experiment: He carefully selected 20 mice of equal size and weight. He placed 10 mice in a microwave for 10 seconds. The other 10 mice were not exposed to microwaves. To test strength, he placed a heavy block of wood over the food dish. He found that 8 out of 10 mice that were exposed to microwaves were able to push the block away to get to their food. Five of 10 mice that were not exposed to microwaves were able to push the block away to get to their food.
Hypothesis:
Independent Variable:
Dependent Variable:
Control group:
Constants:
Lisa has a stained glass window with lots of green glass in her room. She thought that the green light that shines through that glass might help her plants grow better. She decided to place three plants in front of the green stained glass window, and three plants in front of a regular window with clear glass. She measured the number of leaves and height of the plants every week for three weeks. She found that the plants in front of the clear glass window grew a total of 5 cm and had an average of 10 leaves per plant. The plants in front of the green window grew 1 cm and had an average of 5 leaves per plant.
Hypothesis:
Independent Variable:
Dependent Variable:
Control group:
Constants:
G. Reading Passage
BIAS IN SCIENTIFIC INVESTIGATIONS
Sometimes a conclusion may seem pretty clear at first glance; but it is the job of the scientist to be skeptical. That does not mean a scientist must be negative, but that he or she must not blindly accept the conclusions of others. Instead, the scientist must critique arguments in case they are based on faulty or misleading information or an incomplete use of mathematical data. Consider the following examples:
Experiment 1: Dr. Cloud is conducting interviewed of Davisville and Springville High School students to determine the rate of smoking among American teenagers. Dr. Cloud got a list of all of the students from each high school and randomly selected 50 students from each school. He scheduled an appointment to interview each student and his/her parents. Each student was interviewed with the parents in the room. The students were asked questions such as, “Do you smoke regularly?” “Have you ever smoked?” and “What percentage of your friends smokes?” After finishing the interviews, Dr. Cloud concluded that only 1% of American teenagers smoke regularly and that 18% of teenagers have tried smoking.
Experiment 2: Dr. Nandi is using confidential interviews to estimate the rate of smoking among American teenagers. She contacted principals at three high schools (rural, urban, and suburban) and asked for entire lists of the student body. After randomly selecting 50 students from each school, she gave permission slips and confidentiality forms to each student so that the students’ parents would know that their child was participating in the study and they, as parents, would not have access to the file on their own child. Roughly 35 students from each school returned the permission slips and confidentiality forms. Students were asked fifteen questions about their experiences with smoking. Dr. Nandi found that 53% of the high school students had tried smoking and 25% of high school students smoked a half pack of cigarettes or more a day.
In Example 1, the conclusions were based on a faulty experimental design. It is important for scientists to include experimental design and procedure in a summary of their research. Without realizing it, a scientist might design an experiment that leads to an expected conclusion or might interpret the data in only one way. Predisposition to a particular idea or conclusion is known as bias. By allowing other scientists with different reviews to repeat the investigation or to review their data, scientists can develop a more objective and reliable conclusion.
_____1) The original conclusions of Experiment 1 were faulty because
a) Dr. Cloud did not have appropriate questions for the students
b) having parents in the interview room may have caused students to answer Dr. Cloud’s questions untruthfully
c) it is a well-documented fact that more than 1% of students in high school are smokers
d) Dr. Cloud’s analysis of the data was based on poor mathematical principles
_____2) The data from Experiment 2 may be more reliable than those from Experiment 1 because
a) it is obvious to most adults that about half of all high school students are smokers
b) Dr. Nandi’s results seem more realistic than Dr. Cloud’s
c) Dr. Nandi used a larger sample from each high school
d) Dr. Nandi’s experiment was designed to allow students to answer the questions more truthfully than Dr. Cloud’s
_____3) Dr. Cloud and Dr. Nandi can avoid bias by
a) publishing results that will allow other scientists to repeat the investigations or design other investigations
b) publishing results in a respected scientific journal before anyone else can complete more research
c) using the newspaper or popular journals to publicize their findings
d) limiting their research to students who drive to each high school as subjects for their investigations
H. BCR
Gibberellic acid (GA) is a hormone that affects the growth of plants. A student predicted that spraying a gibberellic acid solution on corn plants would increase their rate of growth. To test this theory, she planted a corn plant and sprayed the same amount of gibberellic acid solution on it every day for one week. At the end of the week, she found that the corn plant had grown seven centimeters. Based on this observation, she concluded that gibberellic acid caused the plant to grow faster.
- How valid is the student’s conclusion? Explain your answer using what you know about correct experimental design
- Describe how she should have designed her investigation to get more useful results.
Write your answer on notebook paper.
I. BCR
A “computer virus” is a program that can reproduce itself inside a computer. In time, it can grow and evolve. Is a computer virus alive? Why or why not?
In your answer, be sure to
- Explain what it takes for something to be considered alive.
- Support your determination about whether a computer virus is alive or not.
- Use appropriate scientific terminology.
Write your answer on notebook paper.
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Biology HSA Review Spring 2006