Scientific Inquiry Review

Transcription

1 Scientific Inquiry Review Adapted from Regentsprep.org Be able to USE AND APPLY the steps of the scientific method to solve a problem and design an experiment: Scientific Method: 1. Make observations about the world around you. 2. Identify a problem- This is in the form of a question - Example: How does fertilizer affect plant growth? 3. Form a hypothesis- This is a statement about what you think will happen - Hypotheses are NOT randomly written. They are based on background information and prior research. - Be specific- for example: The fertilizer will affect plant growth is NOT a good hypothesis. It does not state HOW the fertilizer will affect the growth- faster? Slower? More leaves? A better hypothesis is The fertilizer will increase plant growth. This is a better hypothesis because it describes how you think the fertilizer actually affects plant growth. It is measurable. It helps us determine what type of data to collect. In this example, we can measure if there is an increase or decrease in plant growth and then support or not support the hypothesis. - Hypotheses are SUPPORTED or NOT SUPPORTED Avoid saying: correct, prove, false - Even if a hypothesis is not supported, it is valuable because it can lead to further experiments. 4. Design a controlled experiment: - The experiment should have a control. The control is a standard for comparison. o A placebo (sugar pill) is used as a control for experiments involving medication. Water is also used as a control in some experiments. - The independent variable is what a scientist purposely changes between two groups (for example drinking coffee or not drinking coffee); it is what is tested. - The dependent variable is what the scientists measures, or what changes as a result of the experiment. The DATA. o for example, you would measure the heart rate of the coffee/non-coffee drinkers 5. Collect data: This is when you measure some type of change between the experimental or control groups (for example, measure the heart rates of the coffee and non-coffee drinkers and organize it into the data table). This could involve counting, measuring the height, distance, volume, amount, etc. - Be specific. If you can state, when, how often and in what units you collect the data. 6. Analyze results- Interpret what the data means. Describe the relationship or trend displayed in the graph or data table. Ex- the coffee drinkers had a higher average pulse rate than the non-coffee drinkers. Sometimes, you have to apply a statistical analysis to analyze the results (standard deviation, percent error, chi square analysis- don t worry- you do not ACTUALLY have to learn what these are (until AP bio ) 7. Form a conclusion- State whether the hypothesis was or was not supported by that data. - Again, stay supported or not supported and do not say proved. All scientific explanations/conclusions are subject to change and can be improved upon. Sometime, they can, lead to more questions. This can lead to new hypotheses being created. (think: further experimentation and improvement of experiments)

2 Well-accepted bodies of knowledge are theories. They are supported by a wide amount of scientific experiments which have been replicated and similar results have been obtained each time. o A theory is a generalization. For example, the Theory of Evolution is a general statement: species change over time. The experiments and evidence that support it however, are not general, but very specific. For example, comparing DNA of humans and apes, looking at how a bacteria colony evolves to have antibiotic resistance. Here is an example: The Scientific Method in Action You are the head of the research division of the Leafy Lettuce Company. Your company is experimenting with growing lettuce using hydroponic technology. Hydroponic technology involves growing plants in containers of growth solution in a greenhouse. No soil is used. The growth solution that the company uses contains water, nitrogen, and phosphorus. The company wants to know if adding iron to this formula will improve lettuce growth. state a hypothesis to be tested in the new experiment state how the control group will be treated differently from the experimental group state what type of data should be collected to support or refute the hypothesis A good hypothesis relates the independent and dependent variables of the experiment together. In this experiment, a good hypothesis could be that the addition of iron to the growth formula will improve the growth of the lettuce. (Note that the hypothesis is phrased as a statement, not a question.) The control group is not given the variable being tested. The experimental or variable group would receive the iron added to its growth solution, while the control group would not. The type of data collected involves how the independent variable (the kind of growth solution) influences the dependent variable which is the growth of the lettuce. The experimenter would want to collect precise measurement data, such as how much more the lettuce grew in cm. or gained weight in grams. Valid experiments: a valid experiment is one that is carried out properly so you are able to draw conclusions. When people make a claim (you can get washboard abs by doing 8 minutes of ab workouts a day, for example), you should determine if the experiment is valid to determine if you should value that claim. What makes an experiment valid/ways to improve experiments so they are valid: a large sample size is used (large number (over 100) of mice, people, plants, etc. are used) only one variable is tested (there is only one thing different between the control and experimental groups) There is a control group. You must be able to compare what you are testing to a standard to determine if there is an actual change (sometimes the control can be a before/after experimentmeasuring blood sugar levels before and after eating).

3 o There is a control (water, placebo (sugar pill) are examples of controls)the experiment has been repeated many times the experiment is able to be preformed again by another scientist (reproducible, replicable) The experiment is performed many times, deriving the same results There is no bias (ex. The scientist influences the results to get a certain outcome) Incorrect conclusions are drawn based on the data 1. Identify the variables to be plotted Technique for Constructing a Line Graph independent variable -- the variable changed by the experimenter (the soap in the water) --is plotted on the x-axis (horizontal axis) dependent variable What is measured or observed; the data that is collected (number of drops) -- is plotted on the y-axis (vertical axis) 2. Determine the scale of the axes -- determine each axis individually -- may easily be determined by taking the largest value to be plotted and dividing by the number of blocks and then rounding up to the nearest convenient number -- the graph should be spread to occupy the most available space -Go in EVEN INTERVALS, regardless of what numbers are in the data table (2, 4, 6, 8 5, 10, 15, 20..5, 1.0, 1.5, 2.0..) -If you skip lines in between each interval, then skip the first line (after the origin) too. -DO NOT a zero on the origin, unless zero is in the data table 3. Number and label each axis indicating the appropriate units. 4. Plot each data value on the graph with a point. 5. Draw a line connecting the data points. -- do not connect data points to the origin unless there is data to support this 6. Provide a title which clearly indicates what the graph is about. Include the dependent and independent variable (ex. The Effect of Fertilizer on Plant Growth) 7. If the graph has more than one set of data, provide a key to indicate what is represented by the different lines. Example: put a square around one set of points and connect the line THEN put a circle around the second set of points and connect the line. DO NOT plot points for both lines simultaneously. Measurement Volume Measurement A commonly used instrument to measure liquid volume is the graduated cylinder. This instrument usually measures liquid volume in milliliters (ml). Using a Graduated Cylinder

4 It is important to remember to read to the bottom of the curved line or meniscus when measuring solutions involving water or most liquids. You must also determine how many increments, what volume, each line represents. The graduated cylinder on the left is divided into increments of 2 ml, so the volume in it is 12 ml. The graduated cylinder on the right is divided into increments of 1 ml, so the volume in it is 16 ml. Mass Measurement The triple beam balance is commonly used to measure mass in the biology lab. This device is named for its three long beams on which sliding bars called riders (or tares) are used to determine the mass of an object placed on its platform. It is very important that the riders on the rear beams are in the notch for the whole number of grams and not in between notches. The front beam is a sliding scale graduated in grams. The rider on this beam can be positioned anywhere on the scale. Masses on a triple-beam balance can be read to tenths of a gram and estimated to hundredths of a gram. Using the Triple Beam Balance The mass of the object appears to be grams (g). Length Measurement Most measurements in biology will involve metric units of measurement. It is good to start at a whole number increment that isn't 0. Many times the end of a ruler will be worn away by student/teacher use or is inaccurate due to the manufacturing process. It is important to remember to take away the whole number increment one has moved in on the ruler (in the example below 1 cm) from the measurement obtained.

5 There s more Using a Ruler to Measure Length: BE CAREFUL!!! They throw in the same trick, every time!!! Typically the Regents does not place the object that is measured at the zero mark on the ruler (see below: the leaf STARTS at the 1cm mark) Problem: How long is leaf A? The tip of the leaf is at about 6.5 cm, but note the measurement started at 1 cm. Therefore, Leaf A is 5.5 cm or 55 mm. in length. ***They also may give you a rule in cm and the answer in mm. You must be able to convert! From cm to mm, move the decimal one place to the right. From mm to cm, move the decimal one place to the left. Conversions: milli Know how to convert from milli (m) to micro (µ) and micro (µ) to milli (m). Milli (m) to MicRo (µ)- move the decimal three places to the Right) micro Micro (m) to milli (µ)- move the decimal three places to the Left Example: Milli to micro: Micro to milli: mm= µm µm = mm The size of a microscopic field of view can be determined on low power using a device called an optical micrometer. Finding the Size of a Microscope Field of View

6 In the pictured field of view at the left, it can be observed that there are approximately 3 1/2 divisions equal to a length of 3.5 mm. Therefore this field of view is equal to 3.5 mm or 3,500 micrometers. The field of view: the diameter of the circle of light, how much you can see of the specimen you observing. As you increase the magnification, the field of view decreases (you see less of the specimen because you are zooming in on it) As you decrease the magnification, the field of view increases (you see more the specimen because you are zooming out) Microscope: To determine the magnification, MULTIPLY the magnifications of the lenses. For example: 10X ocular, 10X objective= 100X magnification 10X ocular, 40X objective= 400X magnification A microscope flips the image 180 of what you are looking at. Just turn the paper upside down to see how its drawn. The specimen moves the opposite direction when viewing under a microscope. Move the slide to the right to center the e Left: regular e Right: e when viewed under a microscope Microscope parts and functions: