BioDreamMachine Exploring Nature's Solutions

Form from Function: in the living world, often you can learn a lot about what an organism has to do by the shape that it has... and vice versa. Existing natural forms are, because of natural selection, successful forms, and successful forms do their jobs well.

Nature forms to shape: living forms are growing forms and that means that organisms grow into the forms that work. These forms are the result of the DNA recipe contained in each cell of the organism and the physical forces of the environment that act on the organism. An example is a tree growing in a windy spot: the basic recipe for roots, shoots and leaves will be affected by the stresses placed on the tree by the wind.

Nature builds from the bottom up: living organisms are able to form to shape because the basic building blocks for growth and maintenance exist at the molecular and cellular level. Structural challenges, like growing a branch of a tree at a windy site, are solved across scales: chemical signals trigger cell production, these cells are differentiated into various forms of tissue and integrated into the entire organism in selected areas to reduce stress. All scale solutions, therefore, may work together to counteract the effects of the environment.

Natural Selection: Charles Darwin's 1858 theory of evolution contains three basic ideas about natural selection: there is competition in the natural world for scarce resources, certain random traits or characteristics of individuals allow them to compete more successfully for these resources and therefore survive and reproduce, and this reproduction of these successful individuals, over time, leads to an evolutionary dominance of these traits and even to new species.

• Hierarchy

  Hierarchy

  Wed, 2009/07/29 - 15:51 — nhoeller

  Life builds from the bottom up: a few simple components form chains and then are folded to make complex shapes. These shapes are then combined to make even more complex structures up through a nesting hierarchy of scale, from sub-atomic particles to the universe.
   
• Laws and Limits

  Laws and Limits

  Wed, 2009/07/29 - 15:53 — nhoeller

  Nature (the living world) is bound to obey the laws of physics and limits of space and is shaped by these laws and limits into patterns and forms. For example, there are only so many ways that you can fill space or join two points or fit certain shapes into a container. Living organisms must abide by these limits. Organisms must also respond and adapt to forces like gravity or the surface tension of water. Their forms are often shaped by these adaptations and different creatures face different challenges. For example, large animals must struggle against gravity and inertia, while small insects must struggle against forces like drag and surface tension.
• Form Follows Function

  Form Follows Function

  Wed, 2009/07/29 - 15:54 — nhoeller

  The shapes and patterns you see in Nature can be explained often by the functions that an organism has to perform. These shapes are subject to the laws of physics and the confines of space, but they are also the result of billions of years of evolution. The natural selection associated with this evolution has tended to extinguish forms that were not successful within a dominant environment. What we see around us are the forms that worked.
• Structures: force is any influence that causes a free body to undergo acceleration.
• Structures: work is when force moves an object
• Structures: tension is pulling, a force related to stretching.
• Structures: compression is pushing, a force related to making an object more compact.
• Structures: torque is twisting. It is the tendency of a force to rotate an object about an axis.
• Structures: stress is a measure of the force per unit area of surface

Design and analysis for those students who tend to do well in open problem-solving.

Linking physical science to everyday life through structural design in architecture and engineering.

Linking physical science to natural science through a discussion of its effects on living tissue.

Linking biological science to mathematics through a discussion of geometry.

STANDARDS:

Link to California State Science Standards

Part One: natural artifacts (see description), images/diagrams of at least one of the artifact for more in depth explanation of its functions in living world.

Part Two: standard brick and sheet of 8.5 x 11 inch cardstock.

Part Three: material sets for student teams to be chosen by teacher (see description), standard test weight to be chosen by teacher.
 

Part One

In a roundtable format, students are allowed to examine artifacts from the teacher's collection: bird breast bones can be gotten from the supermarket, scallop shells from the beach or gift shop, various seed pods from the outdoors, plant stems from the garden. The local nature preserve often will have natural artifacts that might be borrowed or shown by an outdoor educator: turtle shells, birds' eggs, skulls. Artifacts can be passed around all at the same time, or one by one, or assigned to individual students or teams who must give their best explanation for the shape in their hands, depending on the behavior of the class.

A  short lecture follows this general inquiry after potentially distracting artifacts are collected. It  might use the bird breast bone as an demonstration: first showing the overall anatomy of a bird and locating the breast bone within the organism, then explaining the parts of the artifact and the functions. For example, the largest muscles in most birds are the flight muscles and these are anchored to the so-called keel of the breast bone. The keel also forms a "t" with the main plate and therefore is similar to a steel beam that we might manufacture. Finally, parts of the breast bone are thicker than others and represent the response of living cells to stress and the technique of equalizing that stress. This can also be seen in trees where branches thicken to meet trunks relieve stress.

Part Two

The students have now been engaged with the artifacts, offered some theories about their shapes and been shown one example in more depth. This is followed by some general background which is presented as information they will need to compete in the design portion of the session. This is a short explanation and demonstration of some structural engineering terms: force, resistance, tension, compression, and torque. They can all be demonstrated using a simple wooden ruler. Finally, the group as a whole is given this puzzle: using this 8.5 x 11 inch sheet of cardstock, can I (the teacher) support this brick? If yes, how? If no, why not? The teacher then demonstrates her ability to support the brick by folding the sheet accordion fashion and forming it into a cylinder. It's possible to lock the sheet into a cylinder without tape by making two interlocking slits in the joined ends.

Part Three

Organized into teams of 2 or 3 the students are issued identical material sets and charged with constructing a bridge between two desks that can support a small weight. The team that uses the least amount of material wins. A typical material set might be simply five sheets of cardstock, no tape, forcing the students to make shaped connections, rather than solve their structural problems with an adhesive. Whatever the distance between the desks, material list and test weight, the teacher should try this herself before issuing the challenge to students, so that she knows what a practical weight is, how much material students will need for the span, etc.

Part Four

After declaring the winner, the teacher has the opportunity to tie the competition back to some of the natural artifact strategies the students had observed, and some of the physic principles they were taught. It is also an opportunity to get to know what their thought processes were to arrive at their solutions. What worked and what didn't work (and why) is always a good question to ask of them.
 

No spying on other groups, each team must discuss their solutions separately.

Students are allowed to hold each end of the bridge to the desk, but lots of extra points for those who don't have to.

Only the materials issued can be used, but they can be shaped, cut, or combined in any way.
 

Teachers will need to assemble some few simple props: artifacts, diagram or images of the artifact that is explained in more depth, brick, test weight.

Teachers will have to be prepared to talk about structural principles as defined in principles section, and tie to the natural world.

This is a fun exercise that is enjoyed by a range of ages and can be as deep or shallow as needed, depending on the audience and the teacher's knowledge.
 

Variation: this could be combined with a field trip to a state park where artifacts can be shown and explained and the exercise done there.

Variation: students could be assigned particular methods of using shape for strength in the competition based on what they observed in part one.

Extension: students could be assigned a homework launched from this exercise: research an organism that uses shape for strength and explain how and why it does it. In our bird example, the animal needs to reduce its weight in order to fly, but still be structurally strong enough to resist the stresses of flight.