Diagrams generally are of three types: generalized diagrams, diagrams that represent processes, and biological drawings. Generalized diagrams show biological features (these are not a drawing of any particular specimen but an interpretation by an artist/biologist to show the features of something e.g. a drawing of an animal cell or a nephron). Diagrams that represent processes usually are showing the relationship between several steps in a process e.g. a diagram to explain “the triplet code” or the “Loading and unloading of respiratory gases” in mammals. Biological drawings are actual drawings of specific biological specimens showing the precise detail that one can see either with the naked eye or microscope. Textbooks usually only have the first two types unless they are showing a photograph of something with an accompanying biological drawing. The diagrams that you must know for the first year courses are listed in the “Course Outline”. Exams may also test your ability to apply your knowledge and analyze diagrams that you have never seen before.
Interpreting Generalized Diagrams
Generalized diagrams can be used as a reference for interpreting actual biological specimens (in the lab) or for visualizing and learning content of the course such as the name, shape, size, features of structures and their position relative to other structures.
One of the best ways of learning material like this is to draw your own diagram of the generalized diagram. The first time you draw it, draw and label it while looking at it. Concentrate on the size, shape, position and features of the structures so that your drawing is accurate. Next compare your diagram to the original and make sure all details of the diagram are well represented and labeled correctly. Test how much you learned by drawing and labeling it again this time without looking at it. Again compare your drawing with the textbook diagram and make sure there are no missing elements. If there are errors or omissions keep on drawing, labeling and checking it until you are certain that you can replicate the drawing on demand.
For students in Biology 1002 try this technique on the following diagram of a nephron, copied from “Biology 6th edition” by Campbell and Reese.
Using Generalized Diagrams as References in the Lab
Generalized diagrams can be used as a means of interpreting what you see with your naked eye or with the microscope. Since the size, position, colour, orientation or other features of the structures of your specimen may look different from the diagram you may have to make some inferences (reasoned conclusions) as to what the structures are on your specimen. Some people have no trouble guessing what a structure looks like from another view but others struggle with the concept. The more practice you get at interpreting specimens from diagrams the better you get at it. Suppose you saw structures on your specimen that looked like this:
They may in fact be structures that are represented on the diagram as:
So you can see that sometimes some interpretation is required. Often by looking at a number of diagrams of the same structure you get a better idea of whether you are correct in your interpretation. In any case this is a valuable skill to develop in the lab. The advantage of trying to develop this skill in the lab is that there are lots of people that can help you.
A few students completely misunderstand the purpose of reference diagrams in the lab. Instead of using reference diagrams to interpret specimens and developing those all important interpretive skills they simply copy the diagram and go home and memorize the diagram for the lab exam. Unfortunately they find out on the lab exam that they won’t be asked to simply label a reference diagram that they have studied but they are asked to draw a diagram of a specimen and label it. Students that have not developed the interpretive skills cannot effectively draw and label their own diagrams. Copying and memorizing diagrams does not help with the development of interpretative skills.
Interpreting Diagrams that Represent Processes
Textbooks attempt to clarify how processes work by means of diagrams. Mostly these diagrams are an attempt to help students visualize the steps of processes and see how the steps are related to one another.
In “Biology 6th ed.” the authors (Campbell and Reese) usually have a detailed word description of the steps in a process written under the diagram. In order to understand the diagram you first must understand the content that the diagram represents from the text. Next you have to relate the written description under the diagram to the diagram itself. Sometimes this can take a long time to interpret and digest. If you do this stepwise you can draw your own version of the diagram in understandable steps and write what is going on in each step on your diagram.
Sometimes it is hard to see where to start on the diagram other times it easy. Some diagrams actually number the steps on the diagram for you and give you a written description of each step (this is particularly true for life cycles: See Fig. 30.17: The life cycle of an angiosperm Campbell and Reese (6th Ed.)). In some diagrams, the process starts at the top of the diagram and proceeds to the bottom e.g. Fig. 17.3 Campbell and Reese (6th Ed.) and in others they start at the left side and proceed to the right e.g. Fig 9.6 Campbell and Reese (6th Ed.). Some diagrams do not have a set starting point and/or may lack the written description underneath the diagram such as Fig 42.27 Campbell and Reese (6th Ed.).
After you have pieced apart the diagram into steps and written a description of each step on your diagram you might try to create your own written description of the diagram. Make reference to your own figure and use your own words. Reread the information under the figure from the book and see if you have omitted or misrepresented any content.
Biology 1002 students try this exercise with Fig 42.27 Loading and unloading of respiratory gases from Campbell and Reese (6th Ed.) p 894.
Biology 1002 students may want to construct their own diagram of a process. Go to Processing Information/concept Maps/Concept maps 1002/ “Concept Map Exercise 1002 a process” and try to draw your own word description of homeostatic control of water balance by ADH.