# Scientific Model: Definition, Types & Uses

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll be explaining what a model is, how scientists use them and how you can use them in your science classes. We'll go over 2D, 3D and mathematical models and give examples of each.

## What Is a Model?

Imagine being a scientist studying human development. You want to know how a single cell grows into a full human in a mother's uterus. However, it doesn't seem ethical, or even scientifically possible to test different conditions to see what happens to the baby. But, scientists actually do know a lot about how humans develop. So, how did they obtain all this information?

Sometimes, if scientists can't observe an event directly, or the experiments might not be safe for humans yet, they use a model. Models are smaller scale representations of a process or system that scientists can't readily experiment on. For example, imagine having a model airplane. It's called a model because it's smaller than the real thing, but you can still experience flight with it. The plastic wings provide lift and the tiny motor provides the thrust. Even though you are using a much smaller scale, these forces are the same ones that keep real planes in the air.

Today, we're going to look at three types of models used in science, two and three-dimensional models and mathematical models.

## Two-Dimensional Models

A two-dimensional (2D) model is a representation of a system or process on paper. These are commonly used in school. A diagram, picture, or drawing is a 2D model. Let's look at some examples.

If you've ever learned about cells, your teacher probably gave you a diagram to compare plant cells, animal cells, and bacteria cells. The organelles, or compartments of the cell, were drawn out, color coded and labeled. Normally, with the microscopes you have in school, you can't see all these organelles and they would be otherwise hard to identify. However, with a 2D model, it's easy to see how the organelles differ, and to try to categorize them in your mind.

## Three-Dimensional Models

Sometimes, a diagram or image isn't enough. We need to test some things out in three dimensions. There are two main types of three-dimensional models, or models that have length, depth, and breadth, structural models and model organisms.

### Structural Models

Structural models are miniature versions of the larger structure that scientists hope to build. They can be a replica of a new bridge, a prototype for a car, or a design for a new building. Engineers work with architects to build these tiny models to see how the structure will look, and how it will stand up to the forces it will be exposed to when fully built. Models can help engineers determine what magnitude earthquake a bridge can withstand, how well a building will fare in a hurricane, and how much impact a car can take.

In physics class, you might build a model of your own. A popular model is a tin foil boat designed to hold pennies. This project will teach you about force and how to design a boat to hold the most weight. By experimenting with different structures of your model boat, you can understand how the shape of a boat influences its function.

### Model Organisms

Our understanding of the human body has skyrocketed in recent years. Scientists have sequenced the entire human genome and understand the mechanisms that underly diseases such as cancer, Alzheimer's, and diabetes better than ever. One advantage that led to this increase in understanding of human biology is model organisms. These organisms have similar characteristics of development, and even some of the same genes as humans, despite looking unrelated, like a fruit fly. Even though they aren't a perfect match, it's easier, and much more ethical, to experiment on a fruit fly than a human.

For example, the genes that cause the development of body structures in fruit flies, like where the head, arms, and legs go, are the same ones that control development in humans. By studying fly development, we can understand how humans develop and gain insight into genetic diseases.

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