MiddleSchoolPortal/Structure and Function in Living Systems

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Structure and Function in Living Systems - Introduction

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.

Background Information for Teachers

This variety of resources will enrich your content knowledge in the areas outlined by the Life Science Content Standard, grades 5-8, of the National Science Education Standards regarding structure and function in living systems. These areas include the characteristics of living things, levels of organization, diversity, extinction, and evolution. With so many themes, you may be asking, "Where do I start?" For guidance see NSDL Strand Map Service. These maps illustrate connections between concepts and across grade levels. An image of the middle grades (6-8) only part of the some related maps appears below. These represent three of the ten maps under the heading The Living Environment.Clicking on a concept within the maps will show NSDL resources relevant to the concept, as well as information about related AAAS Project 2061 Benchmarks and National Science Education Standards. Move the pink box in the lower right hand corner of the page to see the grades 6-8 learning goals.

Molecular Phylogeny Familiarity with the tree of life allows for deeper comprehension of the diversity of life and evolutionary theory, including the concept of “descent with modification.” This resource provides a concise description and representation of the shared common ancestor of all life on earth and the science of phylogeny using molecules as a basis of the tree’s organization. The page also contains links to information about protozoa and study guides.

Understanding Evolution The heart of the web site that bills itself as a “one-stop source for information on evolution” is Evolution 101! This section can serve as a primer to evolutionary theory or an intensive course in the nitty-gritty details of speciation, micro - and macroevolution, and ongoing research into how evolution happens. The site is replete with examples of how evolution impacts our daily lives, including the problem of antibiotic resistance in disease organisms and the conservation and breeding of endangered species. Before technology enabled construction of phylogenies based on DNA for example, evidence for evolution relied on comparative anatomy alone; now comparative anatomy supplements the growing abundance of evidence. The site also gives lesson plans and activities, as well as strategies for teaching and responding to misconceptions and overcoming roadblocks.

Speciation and Biodiversity: Interview with Edward O. Wilson In this interview, entomologist and conservation advocate Edward O. Wilson answers questions about what species are, how new species arise, and why humans should be concerned about the loss of biodiversity. ESA (energy, stability, and area) is his shorthand for the factors that support a large number of species per unit area. Wilson discusses sympatric and allopatric speciation and how species can evolve relatively rapidly on islands. He recommends that work to ward off species extinctions be focused on areas called hot spots of biodiversity. He also cites evidence that the protection of natural systems does not undermine economic expansion. Links to further information, opportunities for involvement, and biodiversity lesson plans (including one involving this article) are provided.

Skulls: Structure and Function Skulls have been designed for both form and function. Through the use of text and labeled photographs, this web site explains how specific skull adaptations meet the needs of organisms. For instance, visitors will discover that macaws’ beaks are attached to their skull through ligaments to limit the amount of force put on the skull when the birds crack open nuts. The site also presents a series of skull facts, questions, and answers provided by scientists. A unique feature allows visitors to rotate the images of skulls so they can view the different adaptations in form from all angles. While this site is appropriate for high school students, many middle school students would have difficulty abstracting the images into coherent alignment with concepts of evolution and adaptation.

Human Ectoparasites As a living organism part of a bigger ecosystem, humans play host to innumerable other living things. This site lists several related web sites on the topic. We recommend the second, Human Body Lice Reveal the Birthdate of Fashion, and the third one, Humans Less Hairy Thanks to Parasites and Sex, illustrative of how evolutionary theory relates structure and function to animal behavior.

All Lives Seek Balance: Intro to Homeostasis Maintaining balance between a living system’s internal conditions and fluctuating environmental (external) conditions is called homeostasis. This site illustrates and describes feedback loops and contains links to Balance in Natural Communities, Balancing the Planet: Gaia Theory, and teacher resources.

The Pleistocene - Holocene Event: The Sixth Great According to environmentalist Dave Foreman, life today faces the sixth great extinction event in earth’s history. He says the cause is eating, manufacturing, traveling, warring, consuming, and breeding by six billion human beings. For the first time in the history of life on earth, one species, Homo sapiens, is waging a war against nature.

Lessons on Cells, Tissues, and Organs

"Living systems" is a broad term. The National Science Education Standards include study into the organization of living systems, which most people equate to cells, tissues, organs, organ systems, and organisms. Thus, several resources in this section focus on structures and the related functions, such as the nose and related nerve tissues and the brain. To emphasize that not every living thing’s organization follows this pattern to its end, we included a stand-alone resource on microorganisms. Since the eye is a popular topic of discussion in evolution, we have included an inquiry activity on that as well.

Biology4Kids With lots of information and neat photos, this is a great site to learn about how to study and classify life forms, ranging from cells and microbes to plants and animals. Click on Animal Systems for information about cells, tissues, and organs.

Visit Cell City In this online activity, students search the Web in order to learn about human body cells. After collecting their research, they make an analogy between the structure of a human liver cell and a real city. Included are activity pages, team pages, teacher pages, and a list of electronic resources that students will need to complete the activity.

Bring Um Back Alive: Techniques for Finding and Studying Living Microorganisms This image-rich BioMedia article features tips from a micro-naturalist about finding and studying microorganisms. Topics include sampling micro-life communities, care of collected samples, collection techniques, protists and pollution, culturing protists, microscope techniques for viewing living protists, and observing protists in the field. The article is part of a series called The Lives of Micro-Organisms: A MicroNaturalist’s Notebook. The web site also contains links to other articles and features of BioMedia, including a gallery of images and a teacher resources page.

Tissues of Life This web site from the Science Museum of Minnesota offers a fun and interactive way to learn about the structure and function of the body's tissues. While some activities are designed to complement an on-site visit to the Tissues of Life exhibit, the site also includes many stand-alone web-based features. For example, with Explore Body Tissues, students can look at cross-sections of actual human bodies, browse through a gallery of scar photos (and perhaps add a photo of their own!), explore parts of the human body at 30X actual size, or play a game while learning about the different cells involved in wound healing. Tissues of Life does not include lesson plans, but this engaging web site would be a great addition to related classroom activities for a range of grade levels.

Inch of Skin What are the different nerve receptors located in the skin and where are they? This resource is part of a series of hands-on science activities designed to arouse student interest. Here students mark off a square-inch section of skin and gently poke the area, stimulating different nerve receptors. The activity includes a description, a list of science process skills and complex reasoning strategies being used, and a compilation of applicable K-12 science education standards. Also provided are content topics, a list of necessary supplies, instructions, and presentation techniques. The content of the activity is explained, and assessment suggestions are provided.

Habits of the Heart]] This site is a resource for students and teachers interested in learning about the cardiovascular and circulatory systems. Included are lesson plans, classroom activities, online interactive activities, videos, and links to sites about the heart and lungs. Students can also investigate X-rays or build a heart rate monitor. In the lessons section, we recommend lessons 1, 2, and 4a as particularly helpful in developing conceptual understanding of structure and function relationships of living systems.

Enose Is Enose Is Enose This five-page article discusses how scientists and engineers study biological systems to develop artificial systems, in this case artificial olfaction. It describes several simple experiments students can do to raise their awareness of olfaction. We recommend having students begin their inquiry into olfaction with the activities described on page 5, followed by exposure to and discussion of the text on pages 2-4, as opposed to presenting the material in the order it appears. The sense of smell is extremely complex, and scientists working on artificial olfaction have had to study this biological system extensively to extract some basic principles upon which to build their devices. Disciplines of emphasis will involve biology, chemistry, electronics, and teamwork.

Sight and Light Students will learn about the eyeball, pupil, retina, and optic nerve. During this two-day lesson plan, students make a model of an eyeball. Included are adaptations, discussion questions, a rubric for evaluation, suggested reading, links to other sites, vocabulary, and academic standards. When done in conjunction with dissections of animal eyes, such as cow or sheep and shark eyes, this lesson plan allows for a comparative anatomy lesson and thought regarding the different functions of these eyes relative to their structure. A printable version of the lesson plan can be downloaded.'

3-D Brain Anatomy In this interactive model of the brain, users can learn about its parts and specific functions. The model consists of side-by-side image and text areas. Users can employ a variety of control options. For example, they can click on a colorized area of the brain to call up information about it and alter the position of the three-dimensional brain to feature the selected part. There are also buttons for rotating the brain and for zooming. In addition, users can select from pop-up menus to learn about a specific brain area, such as the corpus callosum, and brain functions, such as speech.

Lessons on Organ Systems and Organism Behavior

Keeping with the traditional idea of organization of living systems, this section focuses on the higher levels of organ systems and organism levels. Both animal- and plant-related resources are included. Since behavior includes the concept of homeostasis, has evolutionary roots, is related to both genetics and environment, and is adaptive, we have included resources addressing those topics as well.

Body Control Center Throughout the day, your nervous system monitors and makes endless adjustments to your body's basic systems — all to keep you alive. This interactive feature illustrates the complexity of such a task.

Inside the Human Body: The Respiratory System This web site from the Canadian Lung Association contains an excellent collection of learning resources about the respiratory system for grades 1-12. Older students focus in on smoking, air pollution, and other issues in addition to covering respiratory system biology. The site also offers a teachers' guide.

Reptile Adaptations In this two- to three-day lesson plan, students research a reptile, make a diagram of that reptile, and label the animal's adaptations. Included are the objectives, needed materials, procedures, adaptations, a rubric for evaluation, extension activities, suggested reading, links to other sites, and vocabulary. Students will understand that adaptations can be both physical and behavioral.

Biology of Plants This nicely organized, highly visual site has several subsections, each aligning with the national standards. Topics include characteristics of living things, germination and growth, the basic parts of plants, otherwise known as the organs and organ systems, photosynthesis, reproduction, and ecological adaptations of plants.

Feeding Facilitation: A Lesson in Evolution and Sociobiology This is an outdoor activity designed to demonstrate evolution of feeding behavior in flocking, schooling, or herding animals that maximizes allocation of food resources and enhances survival. Students simulate foraging by searching for and gathering toothpicks. The activity shows the relationships among the energy costs of foraging, predator avoidance, flocking behavior, and evolution. Though written for high school students, the activity is easily adapted for younger students.

Lessons on Diversity, Extinction and Evolution

The National Science Education Standards suggests middle school students obtain an understanding of diversity of species, evolution, and extinction — all functions of natural selection: Species diverge, evolve and go extinct via natural selection. Thus, comprehension of natural selection is the first order of business in this section, and so we provide three activities. Following these is an activity that illustrates one way evolution can be measured and a radio broadcast concerning ancient extinctions.

Natural Selection A common criticism of natural selection is: How can it produce novel, complex and useful structures by pure random chance? Darwin argued that selection is cumulative, not a random process. This lesson provides a way for students to actually compare the cumulative nonrandom selection of Darwin with the noncumulative version so often erroneously implied. Students attempt to produce a full sequence of 13 cards of one suit (ace to king). This must be done by shuffling the suit of cards for each round, then checking the cards. Half the teams must look for the full sequence each time, and repeat the process until this is accomplished. The other teams start to build their sequence by pulling the ace when it first appears as the top card, then adding to the stack whenever the next card for the sequence is shuffled to the top. Discussion reveals how the second method mimics Darwinian natural selection, while the first does not.

Evolution: Online Lessons for Students: Lesson 4 - Flashy Fish John Endler traveled to Trinidad in the 1970s to study wild guppies. The guppies live in small streams that flow down the mountains from pool to pool. In this activity, students take part in an online simulation of Endler's work. They collect data, formulate a hypothesis, run a series of experiments, and find out about the interplay between natural selection and sexual selection in this population of guppies.

Molecular Clocks: Proteins That Evolve at Different Rates Four different proteins from humans and horses are compared in this graphic and article from The Human Evolution Coloring Book by Adrienne Zihlman. The reasons why each protein evolves at its own characteristic rate are discussed. Each protein is useful for measuring evolutionary change over a different time scale.

Time-Lapse Extinctions The last ice age ended about 10,000 years ago, and was followed by a mass extinction of large mammals. This radio broadcast reports on research into how human activity and climate change may have wiped out the big animals. The clip from 2005 is two minutes in length.

Applications of Living Systems Knowledge

This section highlights resources that demonstrate how knowledge of living systems, obtained through the methods of science, enables predictions and technological innovations, driving home the value of scientific pursuits.

Journey North: A Global Study of Wildlife Migration This annual program, running February to June, allows students to participate in the journeys of a dozen migratory species. Students share their own field observations with classrooms across North America. In addition, students are linked with scientists who provide their expertise directly to the classroom. Several migrations are tracked by satellite telemetry, providing live coverage of individual animals as they migrate. Complete program details are found on site. Free registration is required. (The Journey South program begins in August.)

Living in Space This NASA web site explains how astronauts cope with zero gravity conditions in space. Everything from eating, dressing, working, and having fun is included through descriptions, photographs, movies, audio files, and more.

Microbes: Too Smart for Antibiotics? This lesson packet builds on a peer-reviewed article about antibiotic resistance in microorganisms. The packet contains discussion questions about the article, instructions for an activity about hand washing that uses fake, fluorescent germs, and two handouts of ideas for student activities. In many of the activities, students create a product, such as a public service announcement about antibiotic resistance or a funny presentation of the ways that bacteria can swap DNA. The packet also provides correlations to national science standards and a suggested timetable for the activities.

SMARTR: Virtual Learning Experiences for Students

Visit our student site SMARTR to find related virtual learning experiences for your students! The SMARTR learning experiences were designed both for and by middle school aged students. Students from around the country participated in every stage of SMARTR’s development and each of the learning experiences includes multimedia content including videos, simulations, games and virtual activities. Visit the virtual learning experiences on Cells and Genetics.


The FunWorks Visit the FunWorks STEM career website to learn more about a variety of science-related careers (click on the Science link at the bottom of the home page).

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National Science Education Standards

The references, lessons and activities provided in this publication align with the following content standards from the National Science Education Standards.

Life Science: Content Standard C

As a result of their activities in grades 5-8, all students should develop understanding of

  • Structure and function in living systems
  • Regulation and behavior
  • Diversity and adaptations of organisms

Developing Student Understanding

Some aspects of middle-school student understanding should be noted. This period of development in youth lends itself to human biology. Middle-school students can develop the understanding that the body has organs that function together to maintain life. Teachers should introduce the general idea of structure-function in the context of human organ systems working together. Other, more specific and concrete examples, such as the hand, can be used to develop a specific understanding of structure-function in living systems. By middle-school, most students know about the basic process of sexual reproduction in humans. However, the student might have misconceptions about the role of sperm and eggs and about the sexual reproduction of flowering plants. Concerning heredity, younger middle-school students tend to focus on observable traits, and older students have some understanding that genetic material carries information.

Structure and Function in Living Systems

  • Living systems at all levels of organization demonstrate the complementary nature of structure and function. Important levels of organization for structure and function include cells, organs, tissues, organ systems, whole organisms, and ecosystems See Unifying Concepts and Processes.
  • All organisms are composed of cells — the fundamental unit of life. Most organisms are single cells; other organisms, including humans, are multicellular.
  • Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs.
  • Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are in turn grouped together to form larger functional units, called organs. Each type of cell, tissue, and organ has a distinct structure and set of functions that serve the organism as a whole.
  • The human organism has systems for digestion, respiration, reproduction, circulation, excretion, movement, control, and coordination, and for protection from disease. These systems interact with one another.
  • Disease is a breakdown in structures or functions of an organism. Some diseases are the result of intrinsic failures of the system. Others are the result of damage by infection by other organisms.

Regulation and Behavior

  • All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment.
  • Regulation of an organism's internal environment involves sensing the internal environment and changing physiological activities to keep conditions within the range required to survive.
  • Behavior is one kind of response an organism can make to an internal or environmental stimulus. A behavioral response requires coordination and communication at many levels, including cells, organ systems, and whole organisms. Behavioral response is a set of actions determined in part by heredity and in part from experience.
  • An organism's behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces, and responds to danger are based in the species' evolutionary history.

Diversity and Adaptations of Organisms

  • Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.
  • Biological evolution accounts for the diversity of species developed through gradual processes over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.
  • Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow its survival. Fossils indicate that many organisms that lived long ago are extinct. Extinction of species is common; most of the species that have lived on the earth no longer exist.

Read the entire National Science Education Standards online for free or register to download the free PDF. The content standards are found in Chapter 6.

Author and Copyright

Mary LeFever is a resource specialist for the Middle School Portal 2: Math & Science Pathways project, a doctoral candidate in science education at Ohio State University, and presently teaches introductory biology at a Columbus, Ohio local high school. She has taught middle school and high school science and is an adjunct instructor of biology and natural sciences at Columbus State Community College.

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Copyright August 2007 - The Ohio State University. Last updated September 19, 2010. This material is based upon work supported by the National Science Foundation under Grant No. 0424671 and since September 1, 2009 Grant No. 0840824. 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.