Scientists finish a 53-year-old classic experiment on the origins of life

Harold Urey, circa 1963

Urey, circa 1963. Image via Wikipedia

Sometimes an article is so well written that you can do nothing to better it.  Ed Yong is the type of writer to consistently put out articles of that quality-level.

And so all I can do is send you to his blog, for you to read for yourself.

It concerns the Urey experiment on possible origins of life, meticulous science, and more than 50 years of advances around undisturbed samples.

Read all about it here.

Theories & Laws

To round out our discussion on experiments, we need to talk about what happens after experiments are finished.  In a work setting, you would do an experiment as research for either industry (a private or publicly shared company) or academia (a university).  Your results would be published in a peer-reviewed journal, like Science, where other scientists would read about your experiment.  (In many ways, journal publication is the life-blood of professors and graduate students, but that’s a story for another day.)

If many other experiments are run that point to the same conclusions, a theory or a law can be formed, and you would generally publish all the results with in a new journal article that proposes your theory or law.

But what’s the difference, you ask.

First, they are two different things.  A popular misconception is that theories turn into laws as more proof becomes available.  A theory is always a theory and a law is always a law.

A scientific law applies to every observation made with regards to a particular event or element.  For example, Newton’s Laws of Motion describe the relationship between the forces acting on a body and the motion of that body.  If an observation is made about the relationship between the forces acting on a body and the motion of that body that doesn’t fit the Laws of Motion, the law or laws have been disproved.

In brief, a law tends to explain what happens.

A scientific theory attempts to explain how or why something happens. For example, the Big Bang Theory attempts to explain how the universe came to exist.  An alternate theory wouldn’t disprove the Big Bang Theory, rather merely offer another explanation.  It is important to realize, however, that the best theories are supported by numerous observations and/or experiments.  To dismiss something as “Oh, that’s just a theory” doesn’t give credit to the scientists who have worked to explain that phenomenon.

Here’s a list of some notable theories.  And another of some laws.

Spontaneous Generation: A Brief History Of Disproving It.

In discussing experiments, it must be mentioned that frequently experiments are improved upon after they’re finished.  Ideally, you would be able to foresee all problems with an experiment before you begin, but that’s not always the case.  Sometimes you think you’ve done something wonder and had the results published, only to find out later that someone else sees a flaw in your work.  Maybe someone else continues your work and publishes their findings.  Let’s look at a case that is rooted in Biology’s history: spontaneous generation.  For centuries, people have realized the correlation between sex and reproduction in humans.  But some living things were thought to come to life on their own–to spontaneously generate.  In other, living organisms came to life from nonliving matter.

In 1668, an Italian physician named Francesco Redi came up with a hypothesis to disprove the idea of spontaneous generation–specifically, the thought that maggots could come to life from meat.  Redi observed that after meat sat out, flies would be attracted to it, and a few days after that maggots would appear.  Redi thought that maggots were from fly eggs too small to be seen.  Redi set up an experiment–with the control and variable groups–to prove his hypothesis that flies produce maggots.  In the experiment, the control group was a piece of meat in an uncovered jar.  The variable group was a piece of meat in a jar covered with gauze; the gauze allowed air through, but not the flies.  After a few days, Redi observed that the control group had maggots on the meat and the variable group didn’t. He then concluded that maggots only form when flies come in contact with meat and that spontaneous generation is not at play.

In the 1700s, an English scientist proposed that spontaneous generation was possible and performed an entirely different experiment that he suggested proved it.  Later, another Italian scientist, improved on that experiment and concluded that Redi was indeed correct the first time.  So for almost 200 years after Redi, there was still much debate as to whether or not spontaneous generation could happen.

Until there was Pasteur.  Louis Pasteur, in 1864, settled the argument once and for all.  Taking the basic idea of the two scientists from the 1700s and answering critics that said air was necessary for life, Pasteur developed a special flask.  It had a curved neck that allowed air in, but would trap any microorganisms and not let them contaminate his findings.

Pasteur's Experiment
Click for full image

Pasteur showed that his flask was free from microorganisms, even though it was open to the air.  For a year, there was no microbial growth. Until Pasteur broke the neck of the flask.  And when microorganisms appeared, he proved to the world that life could only come from other life.  Because of his findings in this and many other experiments throughout his life, Louis Pasteur is considered one of the greatest Biologists in history.

Experiments

In our last meeting, we discussed the scientific method. I covered a vital part of the scientific method, design and run an experiment, but I’d like to expand a little on that today.

In an experiment, I said we’re always going to have two groups that we test. The first group, the control group, tells us what would happen without our interaction. The second group, the variable group, tells us what happens when we perform our experiment. If our experiment was to test the amount of growth of plants by adding fertilizer, our setup would look something like this:

Experiment

You can see that only 1 thing separates our control group from our variable group. Our variable, then, is the fertilizer. The variable you choose to change is called the independent variable. The variable that changes based on what you do in the experiment is called the dependent variable.

Note: When designing an experiment be careful to not have more than one independent variable. In the event of more than one, you cannot be sure as to which variable actually resulted in the change you’re measuring. For example, in our experiment if we changed both the amount of water we gave the plants and whether or not we used fertilizer, we couldn’t be sure as to whether a change in plant growth was because we used fertilizer or because some plants didn’t get the same amount of water as the others.

In our example experiment, our independent variable is the fertilizer (specifically, the amount we use). A way to remember this is that it’s the independent variable because it is independent of what’s going on in the experiment. Only the experimenter decides how much fertilizer to use. Our dependent variable is the plants’ growth (the amount of growth measured). A way to remember this is that it’s the dependent variable because it is dependent on the other variable. The amount of plant growth is only affected by how much fertilizer we used.

In an effort to not overload you today, I’ll call it quits. Next time, we’ll have a talk about some famous experiments and how they were improved upon by other scientists. In the meantime, feel free to leave me messages, comments, or questions. You can do that here, on my about page, or on my new Twitter account: @amoebamike

What Is Science?

Last time we met, we said that biology is the study of life. Biology is also known as the science of life, or life science. Today we’ll discuss what science is. You probably have an idea of what science is. Ultimately, at least philosophically, we can say that science is the pursuit of truth. However, we’d like to believe that all subjects strive to find the truth. But science is different than every other type of study out there. You can study languages like English; you can study math; you can study history; you can study religion. The one thing that separates science from those other fields is the scientific process, frequently called the scientific method. Most sources vary somewhat in their specific steps (and even the number of steps) that compose the scientific method, however the process as a whole is the same. The basic steps of the scientific method are as follows:

Scientific Method

Ask a question. The most powerful thing the human possess is its inquisitive nature. As long as we are curious, we will continue to grow. So when you look at something and think, “Gee, I wonder why that is?” you’re starting the scientific process. As an example, you might wonder, “Why do bees like flowers?”

Form a hypothesis. A hypothesis is your attempt to answer that question, based on information you already have or can research. So, you might know based on what you have read that bees don’t eat other bugs. Your hypothesis may be, “Bees like flowers because they use flowers for food.”

Design and run an experiment. Now you have to figure out how you can prove that bees use flowers for food. For this, you would need two groups of bees. One would be bees you don’t give access to flowers. If you’re hypothesis is right, then the bees that you keep away from the flowers will starve and die. This first group is called the variable group. The second group of bees, you would do nothing to. This is your control group. The purpose of the control group is to show you what would happen to these bees in nature, if they weren’t in your lab. A great example would be if all your variable bees died and your control bees didn’t. This would mean, whatever was different between the two groups possibly caused the variable bees to die. But if you didn’t have a control group and all your variable bees died, maybe you just got a batch of sick bees and their deaths had nothing to do with your experiment!

Observe and record. During your experiment, a scientist makes many observations. An observation is any gathering of information. You’ll use your senses, or use a specifically designed piece of equipment, to make observations. The information gathered is referred to as data (singular: datum). While observing, you’ll record the data to look over and make any number of decisions with later. In groundbreaking work, the records will also serve to allow other scientists to read what you observed. In the bee experiment, an example of an observation would be “93 out of 100 bees died from the variable group (those withheld from the flowers), and 4 out of 100 bees died from the control group (those that had access to flowers).”

Draw a conclusion. After properly recording your observations, you’ll get to decide what it all means. Analyze your results and come to a final decision on your hypothesis. The decision could just be that the experiment was potentially flawed and should be run again differently (and you would support this conclusion with facts). In our bee experiment the conclusion could be, “Our analysis shows there is a strong correlation (a strong link) between flowers and bees, so it is likely that bees use flowers for food.” Now, we might observe in our experiment that the bees didn’t appear to eat the flowers, so we might suggest a follow up experiment to determine how bees use flowers as food if they don’t actually eat the flowers.

In our next meeting, I’ll give you a little more on experiments. See you then!

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