Cumulative Scientific Evidence & the Development of Models & Theories

Instructor: Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

Scientific theories don't come together on their own. The development of theories and models often involves an accumulation of data from many different scientists, working together and independently. Read on to learn the role cumulative scientific evidence plays in theories and models.

What is a Theory?

Albert Einstein. Charles Darwin. Isaac Newton. You've heard all these names before. Each of these people has developed their own scientific theory, guessing at how the world works.

Well, that's not entirely accurate. In science, a theory is actually much more than a hunch or a guess. A scientific theory is an explanation of how something in nature works, supported by evidence from many different fields. Relativity, gravity, and evolution are all examples of scientific theories. And these theories do not materialize out of thin air. They require an accumulation of evidence over time to be developed.

The Scientific Method

How are theories developed? How is scientific evidence accumulated and turned into a theory? This is done by first using the scientific method to address a question. The scientific method is a series of steps taken to help gather evidence.

First, the scientist develops a hypothesis, or educated guess to explain why something in the natural world has happened. Then, the hypothesis is tested using an experiment. When designing the experiment, the scientist must make a prediction: 'If my hypothesis is correct, when I do X, I will get Y as a result.' After the experiment, the scientist can then make conclusions based on the results, and share the information with others in the field.

Let's look at cell theory as an example. Cell theory states that all living things are made of cells, cells are the smallest unit of life, and cells can come only come from other cells. How was this theory developed? In the 1600s, Robert Hook and Anton van Leeuwenhoek were among the first people to look at living things using microscopes. Hook saw tiny pieces that came together to make up plants. Van Leeuwenhoek saw tiny organisms in pond water. Neither man immediately proved all the tenets of cell theory. However, both started the process.

Model Development

After many experiments, scientists may begin to put together a model, or an idea showing how they think something in nature works. The model is similar to an expanded hypothesis, and can be a helpful way to show how many different pieces can come together to make something work. Just like an airplane model helps you see what an airplane looks like better than reading about it in a book, scientific models help scientists understand how a phenomenon might occur.

In our cell theory example, even though Hook and van Leeuwenhoek weren't able to develop any type of model themselves, further experiments by other researchers added to their work. In the 1800s, a German scientist named Matthias Schleiden noticed that every type of plant he looked at was made of the same cells that Hook had described. He hypothesized that plants were therefore all made up of tiny, individual cells.

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