Scientific Method: Videos & Practice Problems

The scientific method is a systematic approach used by scientists to answer questions and test ideas, starting with observation and inquiry. It involves formulating a hypothesis, conducting experiments, collecting data, and drawing conclusions. Key concepts include differentiating between predictions, which forecast outcomes, and hypotheses, which provide testable explanations. Theories, supported by extensive evidence, represent broader hypotheses. Fundamental biological theories include the cell theory, homeostasis theory, and the theory of evolution, all of which remain falsifiable but are supported by substantial evidence.

Scientific Method

In this video, we're going to introduce the scientific method. And so here's a question that maybe some of you guys have never thought of before. It's asking, how can you possibly trust the information that you learned from your science textbook? Well, the answer to that question is you can trust the information in your science textbook because the information in your textbook has been subjected to the scientific method. So then the question becomes, well, what in the world is this scientific method?

The scientific method is defined as a procedure that is used by scientists to answer questions, test ideas, and gain scientific knowledge. And so this scientific knowledge that has been subjected to the scientific method is going to make its way into your textbook so that you can learn from it and trust it. The scientific method is a series of steps that we'll talk about down below in our image, but the scientific method always starts with an observation and a question.

And so if we take a look at our image down below, what we have here are the 7 steps to the scientific method. Again, the scientific method always starts with an observation and a question. The very first step is going to be to make an observation and the second step will be to ask a question. Now we're going to apply the scientific method to an example that might be a little bit more relatable for you all.

Let's imagine that one night, some evening, you're studying for your biology test, but then you realize that the desk lamp does not work. Here, notice that we have your desk and we've got the lamp here on your desk, and you're observing that the desk lamp does not work. That would be your observation. After you've made your observation, you would move on to the second step of the scientific method, which would be to ask a question. For example, your question might be, why doesn't the lamp work?

After the second step, you would move on to the third step of the scientific method, which would be to formulate a hypothesis and to make a prediction as to why your lamp might not be working. For now, for simplicity's sake, let's just say that the hypothesis is an explanation for your question. Why doesn't the lamp work? You might think that it's not working because the bulb in the lamp is simply loose. Really all you need to do is just screw in the light bulb a little bit tighter and maybe it'll start working.

So after you've formulated your hypothesis and made your prediction, you would move on to the fourth step of the scientific method, which is to design and conduct an experiment. The experiment in your example here might be to just screw in the light bulb a little bit tighter. You just go in and screw that light bulb tighter. After the fourth step, you would move on to the fifth step of the scientific method, which is to collect and interpret the data from your experiment. This would be like checking to see if your lamp actually works after you've screwed in the light bulb a little bit tighter.

After the fifth step, you would move on to the sixth step of the scientific method, which is to draw conclusions. When you're drawing conclusions, you're basically asking, should we accept or reject the original hypothesis that you made? Let's say that you screwed in your light bulb a little bit tighter, checked to see if it worked and then all of a sudden it did work. At that point, you would accept your hypothesis and move on to the last step of the scientific method, which is step number 7, peer review and publish.

By peer review, what this means is that you would get one of your peers, maybe your parents or one of your classmates, to check your entire scientific method process. They would check it for errors and mistakes. If your peers review your process and approve it, you can go on to publishing your data, your results, and your conclusions, which could be published in primary literature. All of the information in your textbook comes directly from published primary literature that has undergone this scientific method multiple times.

Now let's say, for example, that you went through this process. You screwed in your light bulb a little bit tighter, checked to see if your lamp worked, but then you realized that it did not actually work. In that case, you would need to reject your original hypothesis. If you reject the original hypothesis, you would not go to step 7; instead, you would go on to repeat the entire process so it would be a cycle. You would have to make an observation, maybe it's the same observation. You would ask a question, maybe it's the same question. But then you would need to formulate a new hypothesis and make a new prediction, and that would require the design and conduction of a new experiment. Of course, you would repeat this entire process over and over again until you are capable of accepting your original hypothesis and publishing your information.

So this here is really the scientific method and that concludes our introduction to the scientific method. In our next video, we're going to distinguish between predictions, hypotheses, and theories. So I'll see you guys in that video.

Predictions, Hypotheses, & Theories

In this video, we're going to differentiate between predictions, hypotheses, and theories. A prediction is pretty straightforward for the most part, and a prediction can be defined as an expected outcome of an event that can either be correct or incorrect. Predictions will only address the answer to the question: what will happen? For example, I could make a prediction that tomorrow it will rain. Now tomorrow, it will either rain or it will not rain, and so my prediction will either be correct or incorrect. Predictions are pretty straightforward.

Now, a hypothesis, on the other hand, is often confused with a prediction. However, a hypothesis is different from a prediction as it is a proposed and testable explanation for an observation, and the term 'explanation' is incredibly key when it comes to a hypothesis. A hypothesis will address the answers to two questions: what will happen? And why will it happen? The 'why' here is what ties in the explanation term with this hypothesis. Since the hypothesis should answer the question: what will happen, just like a prediction, a good hypothesis or a well-structured hypothesis will often include a prediction. This is why hypotheses are often confused with predictions. However, a hypothesis is different because it is testable and will provide an explanation for the observation, meaning it will answer the question why something will happen. For example, if we go back to that rain analogy, I could make a hypothesis that tomorrow it will rain because I pointed to the sky. This might sound a little ridiculous, and it's not necessary for you to accept the hypothesis. However, the hypothesis must always be testable, meaning that you can design an experiment to determine if you want to accept or reject the hypothesis. The hypothesis must always provide an explanation and should answer the questions: what will happen and why it will happen.

Last but not least, we are going to discuss theories. A theory can be defined as a testable and broad hypothesis of many observations, supported by a large body of evidence. A theory is a broad hypothesis, and in many ways, it is similar to the hypothesis. But again, the theory is going to be much broader on a larger scale, and the key terms that differentiate the hypothesis from the theory are the terms 'broad,' 'many,' and 'large.' A theory is much broader with many observations and a large body of evidence. It's basically a hypothesis at a much larger scale.

If we take a look at our image down below, we can get a better understanding and look at another example to help us better differentiate predictions, hypotheses, and theories. Notice that we are starting with an observation, we have a motorcycle here, and this motorcycle won't start, which is our observation. After we make our observation that the motorcycle will not start, we ask ourselves a question: why doesn't the motorcycle start?

To differentiate predictions from hypotheses, from theories, let's examine these next three boxes. A prediction once again is going to be an expected outcome of an event that can either be correct or incorrect and will only answer the question: what will happen. The prediction here could be, if you add gas then the motorcycle will start. This is simply a prediction because it is an expected outcome of an event, but it will either be correct or incorrect. We could add gas to this motorcycle, and it will either start or it will not start, and so that is a prediction answering the question: what will happen if we add gas, but it doesn't answer any other questions.

Moving on, a hypothesis again is going to be a proposed and testable explanation for the observation. It will not only answer the question: what will happen but it will answer the question: why it will happen as well. For example, we could say that the motorcycle stopped working because it ran out of gas. So, if you add gas then it will work again. Notice that it includes the word 'because' here, and that 'because' automatically shows that this is an explanation explaining why something will happen. It’s saying that it ran out of gas, which is the explanation and it also answers the question, what will happen? So it says that if you add gas, it will work again. Notice here we have a gas meter that is on empty to show that this is explaining why this will happen.

Last, over here what we have is the theory. Again, the theory is very similar to the hypothesis but it's going to be at a much broader scale, supported by many observations, and also supported by a large body of evidence. Here with this theory, notice that we have multiple motorcycles here, so it's not just one motorcycle, it's multiple motorcycles, and we're looking at a much larger scale here. With this theory, what we're saying here is that all motorcycles stop working when they run out of gas so adding gas will allow them to work again. Notice that some of the keywords here are 'all motorcycles' so now it's at a much broader scale than just the one motorcycle we were looking at before. It’s also similar to a hypothesis in that it's answering the questions: what will happen and why it will happen. So it’s saying that they stop working when they run out of gas; that's an explanation, and if we add gas, they will work again; that's answering what will happen.

Now, another important note that I want to mention here is that technically, hypotheses and theories can never be proven to be correct, but they can be falsified, meaning that they can be proven incorrect. This is something that's important to keep in mind because, whereas a prediction can be determined to be correct or incorrect, hypotheses and theories can never be proven to be correct, and so this is why we can only accept a hypothesis and we can only accept a theory, but we can never say that they are true. As we move forward in our course, we will discuss some theories such as the cell theory and the theory of evolution, and again there are large bodies of evidence that support these theories and there are many observations that support these theories, but they can never be proven to be true. They can only be accepted, and they can also always be falsified. So there can always be some finding in the future that may falsify these hypotheses and theories. This is an interesting fact to keep in mind.

This concludes our brief lesson differentiating predictions, hypotheses, and theories, and I'll see you all in our next video.

Scientific Method Example 1

Alright. So here we have an example problem that says, a scientist observed a new phenomenon and wonders how it happens. What is the next step in their study? And we've got these 5 potential answer options down below. And so what we need to realize is that when the scientist observes the new phenomenon and then wonders how it happens, this is really telling us that the first two steps of the scientific method have been completed. And so the observation step and the question step have both been completed already. And so, really what we're looking for here in this problem is the next step, which would be the third step of the scientific method. And so that would be to essentially hypothesize. And so option e here is going to be the correct answer for the next step. Observe has already happened. Experiment does not take place until after the hypothesis has been generated, so that won't be the next one. Design the experiment. Once again, that is not going to happen until after the hypothesis has been created. And then peer review is one of the last steps of the process. And so once again, option e, hypothesize is the correct answer here. And that concludes this example, so I'll see you guys in our next video.

Which of the following shows the best order of steps of the scientific method?

• A. Observation → Data Analysis → Hypothesis → Conclusion → Peer Review & Publish → Experiment.
• B. Observation → Hypothesis → Experiment → Peer Review & Publish → Analysis → Conclusion.
• C. Observation → Hypothesis → Experiment → Data Analysis → Conclusion → Peer Review & Publish.
• D. Experiment → Hypothesis → Observation → Data Analysis → Conclusion → Peer Review & Publish.

Answer: (C)

A scientist observes that even after sterilizing a broth, cells reappear in the broth over time. The scientist then asks: 'Why do cells reappear in the broth after sterilization?' and designs/conducts an experiment. Considering this, appropriately label each of the following blanks as either a 'prediction, hypothesis or theory.'
________________: Cells will only appear in the broth exposed to a source of preexisting cells.
________________: Cells appear only when preexisting cells grow & divide; therefore, cells only appear in exposed broths.
________________: All organisms consist of cells & all cells come from preexisting cells.

Alright. So here we have a practice problem that says, a scientist observes that even after sterilizing broth, cells reappear in the broth over time. The scientists then ask the question, why do cells reappear in the broth after sterilization? And then designs and conducts an experiment. Considering this, appropriately label each of the following blanks down below right here as either a prediction, a hypothesis, or a theory. And so notice that we've got each of these 3 blanks down below that correspond with the, sentence that follows. And so, what we need to recall from our previous lesson videos is that a prediction is an expected outcome of an event, and of course the prediction is really only going to answer the question to what will happen. Now recall that the hypothesis is going to be a testable explanation for an observation. And so not only will it answer the question of what will happen, but it will also answer the question of why it will happen. And then also recall from our previous lesson videos that the theory is really just a testable and broad hypothesis. And so really the key word here is that it is going to be broad. So keeping this in mind, what we can do is take a look at the first blank here, which says cells will only appear in the broth exposed to a source of preexisting cells. Now this sounds like it's answering the question to what will happen. Cells will only appear in this broth when they're exposed to this. But it does not answer the question to why it will happen. Why is it that the cells will only appear in this broth when it's exposed to preexisting cells? Why? And that why is not fully answered. And so that means that this first one is going to be the prediction. Now moving on to the next blank here it says that cells will appear only when preexisting cells grow and divide. Therefore, cells only appear in exposed broths. So this part over here, cells only appear in exposed broths, is basically answering the question to what will happen. However, to say that cells appear only when preexisting cells grow and divide, that's answering the question of why it will happen. The cells will appear in the exposed broth because, cells only appear, when preexisting cells grow and divide. And so because this one is answering the question to both what and why, it will happen, This will be the hypothesis. And then, of course, last but not least, what we have is this last blank here, which says all organisms consist of cells and all cells come from preexisting cells. And so because it's including all organisms, it's very very broad, and that means that this will be the theory. And it turns out that this theory here that all organisms consist of cells and all cells come from preexisting cells is actually a basic fundamental theory, that we will introduce in our next video. And so this here concludes, the answers to this practice problem, and I'll see you guys in our next video.

Basic Theories of Biology

So now that we've introduced the term theory in our previous lesson videos, here in this video we're going to talk about some basic theories of biology. And so, really, there are 3 basic theories of biology that your professors tend to want you all to know. And so, notice down below in this table, we're going to show you each of these three theories and the concept that they apply to. And so, the very first basic theory of biology that you should know is the cell theory. And the cell theory is pretty much saying that all living organisms are made up of cells and that all cells come from pre-existing cells. And so here we have a little image of a cell. Now, once again, recall that theories are really just broad hypotheses. And so, we can tell that it's broad here because it includes this word all.

Now, the second theory that you should be familiar with is the homeostasis theory. And the homeostasis theory pertains to the internal environment. And so here, what we're showing you is a little picture of a person sweating in the hot sun since sweating is a mechanism that helps to maintain homeostasis. But really, all living organisms have this ability to maintain relatively consistent internal environments. And once again, we can tell that this is broad because it includes the word all again.

Now the third and final basic theory of biology that you should be familiar with is the theory of evolution. Now the theory of evolution does not say that evolution itself is a theory. Instead, the theory of evolution says that all living organisms evolved from a single common ancestor. And so here, what we have is a little image that's used commonly to represent evolution. But the idea here is that, once again, theories can never be proven to be true. Instead, there's a large body of evidence that supports the theory. But once again, the theories will always remain falsifiable, which means that they can be proven to be false moving forward in the future, but once again, they will never be proven to be true.

And so, there is quite a lot of evidence that suggests and supports all three of these theories. But for now, this here concludes the basic theories of biology that you should be familiar with, and I'll see you guys in our next video.

Which of the following statements about the cell theory is false?

• A. All living organisms are made of cells.
• B. All cells arise spontaneously.
• C. Cells are the basic structural & functional unit of life.
• D. All cells arise from preexisting cells.

Answer: (B)

Here’s what students ask on this topic:

What are the steps of the scientific method?

The scientific method consists of seven steps: 1) Make an observation, 2) Ask a question, 3) Formulate a hypothesis, 4) Conduct an experiment, 5) Collect and interpret data, 6) Draw conclusions, and 7) Peer review and publish. It begins with observing a phenomenon and asking a question about it. A hypothesis is then formulated as a testable explanation. Experiments are designed to test this hypothesis, and data is collected and analyzed. Conclusions are drawn to accept or reject the hypothesis. Finally, the findings are peer-reviewed and published, contributing to scientific knowledge.

How do hypotheses differ from predictions in the scientific method?

Hypotheses and predictions are often confused but serve different purposes. A hypothesis is a proposed and testable explanation for an observation, addressing both what will happen and why it will happen. For example, 'The lamp doesn't work because the bulb is loose.' A prediction, on the other hand, is an expected outcome of an event, addressing only what will happen, such as 'If I tighten the bulb, the lamp will work.' While a hypothesis includes a prediction, it also provides an explanation, making it testable through experiments.

What is the difference between a hypothesis and a theory?

A hypothesis is a proposed, testable explanation for a specific observation, addressing what will happen and why. It is narrower in scope and can be tested through experiments. A theory, however, is a broad hypothesis supported by a large body of evidence and many observations. It explains a wide range of phenomena and is generally accepted within the scientific community. For example, the cell theory states that all living organisms are made of cells, supported by extensive evidence. While hypotheses can be tested and falsified, theories are broader and more comprehensive.

What are the basic theories of biology?

There are three basic theories of biology that are fundamental to understanding life: 1) Cell Theory, which states that all living organisms are made up of cells and all cells come from pre-existing cells; 2) Homeostasis Theory, which posits that all living organisms maintain a relatively stable internal environment; and 3) Theory of Evolution, which suggests that all living organisms evolved from a single common ancestor. These theories are broad hypotheses supported by extensive evidence and numerous observations, forming the foundation of biological science.

Why can hypotheses and theories never be proven true?

Hypotheses and theories can never be proven true because scientific knowledge is always open to revision based on new evidence. While a hypothesis can be tested and supported by experimental data, it can also be falsified by future findings. Similarly, theories are broad explanations supported by a large body of evidence, but they remain falsifiable. This means that new discoveries could potentially disprove them. Therefore, in science, we can only accept hypotheses and theories based on current evidence, but we cannot claim them to be absolutely true.