# BIO

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```					BIO.1 The student will plan and conduct investigations in which a) observations of living organisms are recorded in the lab and in the field; Activities such as this are used in content instruction. The key is that respect for life and safety considerations should be modeled and emphasized throughout such investigation. b) hypotheses are formulated based on direct observation and information from scientific literature; c) variables are defined and investigations are designed to test hypotheses; d) graphing and arithmetic calculations are used as tools in data analysis; e) conclusions are formed based on recorded quantitative and qualitative data; f) sources of error inherent in experimental design are identified and discussed; g) validity of data is determined; The earliest steps in scientific investigation involve observation, inference, and questioning. The most productive form of observation is comparison. A really simple, informal activity is to compare a potted blooming chrysanthemum plant to a bunch of fake chrysanthemums stuck in a pot of dirt. If you just ask kids to observe a pot of flowers, they may or may not make important observations. But asking how the real and fake flowers are alike and how they are different can lead to a discussion of the characteristics of life. From their observations they may infer that the potted plant is alive and the silk flowers are not alive. Raise the question, how can we demonstrate that one is alive and the other is not alive… kids can then be encouraged to design an experiment to show that the silk flowers are not alive. In a classic experiment, there are two variables (factors which change): the independent and the dependent variables. The experiment is designed to find the effect of the independent variable on the dependent variable. The independent variable is directly manipulated by the experimenter; its values are chosen by the experimenter. A valid experiment can have only one independent variable. The dependent variable changes as an indirect result of the manipulation of the independent variable. Changes in the dependent variable cannot be predetermined; they can only be passively observed by the experimenter. An experiment can have many dependent variables. Example: Janice wanted to find out if the concentration of fertilizer given to tomato plants had an effect on their productivity. She made concentrations of 0 g, 10 g, 20 g, 40 g, and 80 g of fertilizer per liter of water and used these solutions to water 5 different groups of 10 tomato plants each. Over two months of growth, Janice recorded the number of tomatoes produced, the total mass of tomatoes produced, and the number of tomato flowers produced. At the end of the experiment, she harvested the plants, washed and dried the plants and measured the total biomass of plants. Janice had one independent variable, the concentration of fertilizer. She chose the amounts of fertilizer to use. She could have chosen different amounts of fertilizer. She was completely in charge of this variable. She had several dependent variables: number and mass of tomatoes; the number of flowers; the plant biomass. She could only observe these measures of plant productivity. Janice could even have gone further and separated biomass into an above ground and below ground components. Janice then found the mean, median, and mode for each group of tomato plants and presented the results in tabular and graphical form. She could perform statistical tests to find out if the differences among the groups were significant. One of her data tables would look something like this:

Amount Fertilizer g/L 0 10 20 40 80

1

Biomass of Tomatoes Produced in Two Months (grams) 2 3 4 5 6 7 8 9

10

Mean Biomass g

Notice that the independent variable is on the left and the mean dependent variable is on the right. The ten columns in the middle are for the data from individual plants in each experimental group (row). Each of the ten columns constitutes a complete repeat of the experiment, a trial. Thus there were 10 trials because each of the five experimental groups (0, 10, 20, 40, 80 g/L fertilizer) contained ten tomato plants. A valid experiment must have at least 3 trials to allow for the identification of error and more trials are better. Janice would have had one such data table for each of her dependent variables: number of tomatoes; biomass of tomatoes; number of flowers; total plant biomass. The experimental group receiving no fertilizer is the control, often called the zero group. A control is one set of results to which the others are compared. When working in the field rather than the lab, it is not always possible to have a true zero group. In such instances, one particular set of results (usually the lowest value of the independent variable) is chosen as the control. Before doing the experiment, Janice would have made a hypothesis, usually in the form of an “if…then…” statement: If the amount of fertilizer is increased, then the biomass of tomatoes will increase. A hypothesis is an educated guess as to the outcome of an experiment. If this is done to the independent variable, then this will happen to the dependent variable. Intellectual honesty is important here. Students want to be right and will often change their hypothesis after the experiment to match their conclusion, or they will not analyze the data and simply state that the data do support their hypothesis, even when the data do not support the hypothesis. A real scientist is most happy when his hypothesis is not supported! It means he/she has learned something new! Science advances through failure. Another means of presenting data is in graphical form. In this case, the independent variable is presented on the horizontal (x) axis and the dependent variable is on the vertical (y) axis. Graphs may be scatter plots, where the mean dependent variable is plotted as a dot against the mean independent variable. A line of best fit can then be drawn visually or statistically using graphing calculators or spread sheets. Alternatively, a bar graph can be used, where the height of the bar is the mean for any given experimental group. A bar graph must be used if the values of the independent variable are not quantitative. For example, suppose Janice had used different brands of fertilizer instead of different amounts. Then she would have to use a bar graph. Since graphs are visual representations of data, they are the easiest means to a conclusion. In making a conclusion, one simply examines the relationship between the independent and dependent variables. As the independent variable increases, what happens to the dependent variable? It increases, or it may decrease, or perhaps it remains the same. Examine the graphs below for examples:

dv

dv

iv

iv

In the case of the first graph on the left, as the independent variable increased, so did the dependent variable. On the right, as the independent variable increased, the dependent variable decreased.

dv

dv

dv

iv

iv

iv

In the two cases on the left, there is no relationship between the independent and dependent variables. As the independent variable increases, there is no change in the dependent variable. In the case on the right, there are two distinct groups of data present. These groups would presumably have some biological meaning. If we are looking at beak length and beak depth, then the two groups might represent two species or subspecies!

dv

dv

iv

iv

These two graphs represent typical maxima and minima relationship between variables. For example, in the first instance, enzyme activity (dv) may be maximized at a certain temperature (iv).

Another type of graph that is important in biology is the frequency distribution. For example, suppose a ratio of tail length to body length is measured for a large number of marine iguanas in a single population on an island. A frequency distribution allows the scientist to examine one experimental group in detail. Each individual is graphed, not a mean. The relationship between the mean, median, and mode of a population can then be visually presented. The horizontal axis is the observed data (ratio of tail to body length). The vertical axis would be the numbers of individuals falling into that data category. This is usually done with a bar graph. These types of graphs are useful in environmental and evolutionary studies. If enough trials are conducted, then frequency distribution can be analyzed for each change made in the independent variable.

numbers of individuals

ratio tail length to body length
In this case, it is clear that the data fall into two distinct populations, it is bimodal. These could represent age cohorts, or subspecies, or sexes. Clearly, further investigation would be necessary! This kind of graph can be illustrated to your classes by having them measure the height of everyone in the class and constructing a graph similar to that above. In this case, the mean (arithmetic average), median (mid point, 50% are greater, 50% are less) and mode (most frequent observation) can be analyzed. Extremes in a population could be error, or they can actually represent real data and the variability inherent in natural populations. To return to Janice’s experiment with tomato plants, there are many things that could have changed, but should not be allowed to change. These are constants. If a constant changes, it becomes a second independent variable and invalidates the experiment. For example, Janice’s tomato plants should all receive the same amount of water on the same schedule, the same amount of light, the same temperature, the same soil type, the same type of fertilizer, etc. They should be the same variety of tomato. A change in any of these things would be a source of error and would be a second independent variable. h) chemicals and equipment are used in a safe manner; You should refer to your county policy and/or safety contract for details. Safety cannot be strongly enough emphasized. As a practical matter, students should be prohibited from horseplay, eating or drinking anything in a lab. The most common unsafe behavior is “freelancing” in which students fool around with lab chemicals or equipment prior to receiving instructions or in contradiction to instructions. This should be emphasized even with such “safe” materials as rulers and markers. Also, it is imperative that students be given enough time for clean up at the end of lab and that they always wear goggles.

i) appropriate technology including computers, graphing calculators, and probeware, is used for gathering and analyzing data and communicating results; j) research utilizes scientific literature; These are beyond the scope of this course. k) differentiation is made between a scientific hypothesis and a theory; A hypothesis is a specific educated guess as to the outcome of a given experiment. As such it is tested and accepted or rejected on the basis of that experiment. A theory is the highest form of scientific thought. It is an all encompassing idea which has stood the test of time. It has always been substantiated in lengthy and varied research projects. It unifies and explains many, many observations. When we refer to the theory of evolution, we are saying this is a unifying concept in biology and practically every line of investigation in biology can be brought back to evolution. To say that evolution is “just a theory” is totally misleading and indicates a lack of understanding of the concept of a theory. Theories are the work of many individuals over long periods of time. They can be modified and extended as more information becomes available, but usually remain close to the original formulation. As a science matures, unifying theories are developed. In earth science, the theory of plate tectonics is similar in scope to the theory of evolution in biology. l) alternative scientific explanations and models are recognized and analyzed; and m) a scientific viewpoint is constructed and defended (the nature of science). These are met through examination of specific content areas in biology and specific lab activities. http://nemo.sciencecourseware.org/BLOL/ A series of inquiry based biology lessons. Data are simulated and interpreted on a variety of subjects. Great for data interpretation. After reviewing material in your textbook, go to the file labeled BIO.1 Review Response and open it in Word. Type your answers below each question and make them a distinctive readable color or font. E-mail this file as an attachment word document to the address provided in the introduction and please keep your answers succinct.

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 views: 29 posted: 11/29/2009 language: English pages: 5