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New Teachers Online: How-To Articles:
Teach High School Science

Teaching About Evolution
Judy Jones

The quizzical expression of the monkey at the zoo comes from his wondering whether he is his brother's keeper, or his keeper's brother.

Evan Esar

I am asked many times about how I teach about Evolution. Fortunately, I teach in a district where a large number of the parents are scientists and/or professors who would be outraged if I did not teach the scientific theory of evolution by natural selection – and teach it well! However, I know that this is not true in many districts across the United States. And I do get isolated students each year who make it clear to me that they “do not believe in evolution.” I am always a little amused by this statement but I approach it seriously and I will share with you how I address this controversial issue. The current idea that looms as a challenge to evolution is the idea of “intelligent design.” And I will try to briefly explain this idea as I discuss my approach to the teaching of evolution.

During my discussions and activities about evolution, I am always respectful of the diversity of my students. I try to help them understand that there are multiple ways to view and understand the world – through science, through literature, through art, through religion – and many other ways, also. I explain that I am not trying to change their faith. I am merely trying to help them understand a scientific theory that is at the core of understanding biology. I try to help them understand the differences between the processes of science and the processes of faith.

I begin by talking about Science and the Nature of Science. I talk to the students about hypotheses, theories, and laws and how they are derived in science. I talk about ideas that are scientific and ideas that are not scientific. I explain that the process of science is generally this:

Observe => Ask questions => Propose hypotheses => Conduct Investigation => Alter hypotheses when repeated investigations do not support the hypotheses => etc.

Whereas faith is a belief; one does not alter one’s faith to fit observed evidence.

I ask students to learn the theory of evolution by natural selection; they don’t have to “believe” in it. Science is about evidence to support ideas, not about belief. I do not teach creationism nor intelligent design because they are not science and I am a science teacher. I will however, try and explain the controversies when my students ask. But I encourage them to ask their parents or their religious leaders as well.

The scientific method is not esoteric. It is not used just by those with scientific Ph.D.’s. Science methods are used in our daily life. When we get ready to cross a street, we gather evidence concerning traffic patterns, lights, and speeds, and we generate hypotheses about the best time to cross and then we test the hypothesis. Certainly, we attempt to gather the best evidence possible because we have no desire to disprove this particular hypothesis and get hit by a car!

Science is universal and has been used throughout the history of humankind. Prehistoric hunters certainly used science as they learned the behaviors and tracks of their prey and generated the best theories about the time to hunt, the type of weapons to use, and other things that would help them survive. As said before, science is simply a way of viewing and understanding the world. Scientists have simply formalized this process.

Scientists gather data to make initial observations, they develop hypotheses, they test those hypotheses with controlled experiments and then if the experiments negate the hypotheses, new ones are developed. And if the hypotheses are supported, then the scientists will develop new related hypotheses to test. The process is ongoing………

“In many of our classes from kindergarten through college, we teachers fail to communicate that excitement, wonder, and creativity. We teach the scientific method, experimental design, statistical significance, and multitudes of detailed facts. These are, of course, very important, but they should develop later, once the joy of science is clearly established. Many dedicated teachers do this already, and they should be admired and rewarded for it.

A better way, in my opinion, is to teach the process of science as a way of living, a means to a good life. This should not be hard to do, because everyone wants a better life. Teach that people must draw conclusions everyday, and that the best conclusions for them personally are those founded on strong evidence. Show them that certainty is seldom attained and to accept uncertainty.”

Jere H. Lipps – UC Berkeley

So what is a THEORY?
Most scientists think of a theory as a coherent explanation for a large number of facts and observations. A theory should be consistent and compatible with the evidence and have been tested against a wide range of phenomena. A theory should be effective in problem-solving. Theories are more certain than hypotheses. A theory explains how something happens.

And a LAW?
A law is a description of a natural phenomenon or principle that holds true under specific conditions. For example, the law of gravity describes what happens when we drop things. It is utterly predictable. In a way, evolution is a law; organisms change over time – and that is evolution. But the “how” of evolution is a theory – the theory of natural selection. It is the most tested and accepted explanation of how the change in organisms happens over time.

So what is the Theory of Evolution by Natural Selection?
Charles Darwin said:

  • Populations would grow exponentially if there were unlimited resources
  • Environmental factors limit reproductive capacity
  • Organisms compete for resources
  • There is variation within populations and those with useful adaptations survive
  • The survivors reproduce and pass on their genes
  • The new generation will have a greater frequency of the adaptive traits
  • Over a long period of time, the differences are so great that the result could be a new species

What is the evidence that supports evolution by natural selection?

Evidence from fossils
By studying fossil remains of organisms, scientists have made predictions about what intermediate forms would look like and in fact, have many times found samples of those intermediate forms. For example, the hypothesis that birds evolved from reptiles rather than flying insects has been supported by finding fossil birds that have the features of both reptiles and modern birds.

Evidence from genetics
Research has shown that the genomes of all organisms share the same basic mechanism of heredity involving DNA and RNA and protein synthesis based upon the same code and template. For example, mitochondrial DNA evidence has been used to quantify relatedness in human evolution that implies a branching tree radiating from a common ancestor. This evidence supports and enhances that from fossil remains.

Evolution in action
Many bacterial pathogens have evolved resistance to antibiotics. In the case of HIV, which causes AIDS, significant viral evolution occurs within the course of infection of a single patient. Many agricultural pests have evolved resistance to chemicals that farmers have used for only a few decades. In addition, scientists can perform experiments to study evolution in real time using bacteria and fruit flies that reproduce quickly.

So what is the “theory” of Intelligent Design?

The primary arguments against evolution are proposed by Michael Behe at Lehigh University. He states that some mechanisms found in organisms are of such “irreducible complexity” that they could only be explained if there was a creator.

An irreducibly complex system cannot be produced directly by numerous, successive, slight modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. .... Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.

(Behe 1996)

There are other arguments but they all involve the idea that organisms are so specific and complex that they could not have arisen through multiple random events.

What is one response to Michael Behe’s argument about irreducible complexity?

One example of irreducible complexity that Behe proposes is the bacterial flagellum. The movement and function of the flagellum, which rotates at speeds up to 100,000 rpm, is determined by a multitude of proteins that have to work together like a fine engine in order for the flagellum to move. Behe argues that if evolution is step-by-step then each step has to have reproductive advantage for the flagellum to have evolved by natural selection. He claims this is impossible.

Ken Miller of Harvard University, says that the best response to Behe has come through steady scientific work on genes and proteins. These studies have shown that the bacterial flagellum is NOT irreducibly complex. In fact a special secretion method used by bacteria to deliver molecules to their host (involved in disease) uses some proteins that are homologous to a portion of the proteins involved in the bacterial flagellum mechanism. Studies such as these begin to “chip” away at the irreducibly complex argument.

There are many other examples that the reader can research if interested. One of these involves the blood clotting mechanism of vertebrates.

It is important to note that the arguments against evolution rarely propose alternate ideas or explanations other than to say that “there must have been an intelligent designer.” This is certainly not the way of science but rather the way of faith.

In conclusion, I like to share with my students a quote from Ken Miller, the author of their textbook.

As Darwin wrote, there is grandeur in an evolutionary view of life, a grandeur that is there for all to see, regardless of their philosophical views on the meaning and purpose of life. I do not believe, even for an instant, that Darwin's vision has weakened or diminished the sense of wonder and awe that one should feel in confronting the magnificence and diversity of the living world. Rather, to a person of faith it should enhance their sense of the Creator's majesty and wisdom (Miller 1999). Against such a backdrop, the struggles of the intelligent design movement are best understood as clamorous and disappointing double failures – rejected by science because they do not fit the facts, and having failed religion because they think too little of God.

Please contact me if you have questions or comments about this article.

 

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