1. Introduction

  • Structure refers to something’s form, makeup or arrangement.
  • Function refers to something’s job, role, task, or responsibility.
  • Determine means to cause, direct, govern.

In biology, a key idea is that structure determines function. In other words, the way something is arranged enables it to play its role, fulfill its job, within an organism (a living thing). Structure-function relationships arise through the process of natural selection. But before explaining how that process works, let’s get our heads around the structure-function connection.

Structure determines function is also a key idea in engineering. In this human realm, structure/function relationships are often more obvious and easier to grasp than they are in the biological realm. Let’s use a hammer as an example:

1280px-Claw-hammer
Hammer

Function: This tool has two functions. Pounding nails in, and pulling them out.

Structure to Function Relationship:

The handle allows the tool to be easily grasped. The length of the handle allows for a swing that increases the speed of the head of the hammer. The head is composed of hard metal. When the head hits the nail, the metal transmits the force of the swinging hammer into the nail, driving it into the wood .

The claw allows the user to grab a nail. The rounded head acts as the fulcrum of a lever. The long handle allows for leverage to pull the nail out of the wood.

2. Apply the idea: Human Artifacts

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[h]Application: Structure and Function in Human Artifacts
[q]Describe the function of the tool shown below, and explain how the structure relates to the function.

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[q]Describe the function of this tool, and explain how the structure relates to the function.

[c]wqBzaG93IHRo ZSBhbnN3ZXI=

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[q]Describe the function of this tool, and explain how the structure relates to the function.

[c]wqBzaG93IHRo ZSBhbnN3ZXI=

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3. Structure and Function in Biology

Biological structures come about as a species adapts to its environment. The result is an adaptation: a trait that helps the members of a species to survive and reproduce. Adaptation comes about through evolution, which we’ll study later in this course. But for now, let’s look at some structure function relationships in living things.

3a. Structure and function in the human hand

Anatomy of the human hand, from Gray's Anatomy (source: Wikipedia)
Anatomy of the human hand, from Gray’s Anatomy (source: Wikipedia)

Function: The human hand has many functions, but we’ll focus just on two: grasping things for fine control (such as a pencil), and grabbing objects for power (as in the example of the hammer above).

Structure to function relationship: the opposable thumb (the ability to touch the thumb to the fingers) makes fine control possible. The ability to touch the fingers to the base of the hand and to wrap the thumb on top makes the power grip possible.

3b. Structure and function in human teeth

Human teeth (Gray's Anatomy, from Wikipedia)

Function: The overall function is tearing and grinding food down into tiny pieces that can be easily swallowed, and later absorbed into the body.

Structure to function relationship: The sharp incisors (the teeth in front) can tear food; while the molars (the flat teeth in back) can grind food into tiny pieces. The molars are also closest to the hinge of the jaw, so that’s where chewing can occur with the most force (especially useful for grinding up harder-to-digest plant foods).

3c. Structure and function in biology

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[h]Application: Structure and Function in Biology

[q]Describe the function of the adaptation below, and describe how the structure is related to the function (note: focus on the wings).

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[q]Describe the function of the adaptation below, and describe how the structure is related to the function (note: focus on the ears)

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[q]Describe the function of the adaptation below, and describe how the structure is related to the function.

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[q]Describe the function of the adaptation below, and describe how the structure is related to the function.

[c]wqBzaG93IHRo ZSBhbnN3ZXI=

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4. Next steps

If you need more practice, please scroll up to the top and work through this tutorial again. Otherwise, follow the links below: