Inquiry into the structure and function of living systems is usually inherently interesting to students. For example, students are naturally interested in the workings of their own bodies and are often wowed when observing animal behaviors. The recent documentary March of the Penguins provides a good example of animal behavior that wows all of us. Why does the emperor penguin population behave as it does: long grueling migrations in almost perfect single file? How coincidental is it that the emperor penguins usually lay only one egg which fits so nicely on top of their feet, under their body? What is the relationship between their body structures and organ functions and these behaviors? How do individuals in this species return to their place of birth as adults to breed?

To middle school students, answers to questions regarding animal behavior may appear to be nothing more than wild guesses. But good working knowledge of the nature of and methods of science allows learners to understand that these explanations of animal behavior can be substantiated with empirical evidence derived from sound scientific inquiry. What can we infer from those cases where no plausible explanation for the observed behavior exists? That science has failed? That a supernatural explanation is thus plausible? Of course not — only that science has yet to collect the required evidence to develop an explanation, assuming the question being asked lends itself to scientific inquiry.

For instance, questions of “how” are more science oriented than questions of “why.” The former implies elucidation of a mechanism, a theory, which is after all an aim of science; the latter lends itself to methods of philosophy. It is hard to imagine the empirical evidence needed to answer: Why are flower colors as they are? Although life scientists can infer how various colors appear to be advantageous or adaptive, they are usually reluctant to state that the apparent advantage is the reason why the flower is that color. To say "The flower is yellow because yellow attracts a greater number of pollinators than any other color" is to say that pollinators cause the effect of yellow flowers. Rather, life scientists use an evolutionary framework in developing their explanations.

Within an evolutionary framework, the observed yellow flower color is understood as a function of at least three things: (1) competition, both within the species and between competing species; (2) the current environment, including the relative numbers and kinds of pollinators; and (3) genetic variation. The pressures of competition and environmental factors acting on genetic variation effectively selected for yellow flowers. Thus, the pollinators alone are not the cause of the effect of yellow flowers, and to say that they are the cause is misleading. This is admittedly a subtle difference, but an important one, especially in the larger context of the nature of science and scientific literacy — two areas the educational research community is currently calling for greater attention to.

Animals are not the only living systems to exhibit interesting behaviors. Students can be turned on to the variety of living systems on our planet through inquiry into other kinds of populations:

1. bacteria; What is up with bacteria resistance to antibiotics? How do extremophiles thrive in hot springs, icebergs, and extremely saline solutions?

2. plants; What accounts for so much variation in shape, size, color, flower types, fruits, and toxins?

3. fungi; How has the leaf cutter ant's relationship with fungi endured? Which fungi are harmful to whom and which are helpful and how? and

4. protists; Could life as we know it exist in the absence of protists? In fact, organisms in these domains and kingdoms are easier to study than animals due to their often shorter life cycle and limited mobility.

This discussion has highlighted several important guidelines in teaching structure and function in living systems: (1) Behaviors are inextricably tied to structure; both behaviors/functions and structures are subject to selection pressures; (2) Questions of how can be addressed through the methods of science and plausible explanations derived from sufficient empirical evidence while questions of why are subject to greater uncertainty; and (3) Evolutionary theory frames life scientists' research from their initial observations, to formulation of how questions, to the kinds of data collected, to the interpretations of the data and to the conclusions drawn.

In this publication, we provide a wide variety of resources to enrich your content knowledge of the characteristics of living things, including their diversity, extinction, and evolution. Three groupings of lessons and activities have been selected to introduce your students to the organization of living systems, to organ systems and organism behavior, and finally to the functions of natural selection. Another section illustrates how our knowledge of living systems is applied to uncovering the nature of extreme life forms here on earth as well as to preparing ourselves for space travel. You will also find an overview of the alignment of these topics with the National Science Education Standards.

---

by Mary LeFever

Mary LeFever is a resource specialist for the Middle School Portal, and a doctoral candidate in science education at Ohio State University. She has taught middle school and high school science and is an adjunct instructor of biology and natural sciences at Columbus State Community College. Please email any comments to msp@msteacher.org.

---

 Back to top

Copyright August 2007 — The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 0424671. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

This work is licensed under a Creative Commons License.