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1.1 Science and the Natural World
A FEW NOTES BEFORE YOU READ THIS BOOK:
Please read through these few helps that will assist you and make your studies easier.
If you are doing the workbook pages that accompany this curriculum and need to find an answer quickly, you can use the “find” feature of your browser. Just hold down “control” (Ctrl) on your keyboard and hit the f key. Now you can quickly search for a term to help you complete your worksheets faster. You can also use the search box on the right-hand side of the page.
Also, don’t skip over reading the lesson objectives and vocabulary at the beginning of the chapters, no matter how tempting it might be. The more your brain comes in contact with the material, the easier it will be to learn.
Don’t skip the videos & activities unless I’ve marked them optional! They are there to give you a chance to fire up different sets of brain cells / pathways. The more ways you can learn (seeing, hearing, saying, doing), the better you will retain what you are studying. If you are really struggling with a chapter or just want to remember it even better, try reading it out loud to yourself.
Remember that short-cuts won’t help you and will only hurt you in the long run. If you learn this material as best as you can NOW, you will have a much easier time when you are sitting in a college biology class someday. Even if you never take another biology class ever again, you’ll at least have learned a few good habits that will serve you well in other areas.
I wish you every success, and my prayer is for you to have a good year with ALL of your subjects. I hope that someday you will be able to look back at some of the things you learned this course and realize how it contributed to a better understanding of the world around you.
Realize that we can know God through the study of His creation
variable in a scientific experiment that is affected by another variable, called the independent variable
possible answer to a scientific question; must be falsifiable
variable in a scientific experiment that is manipulated by the researcher to investigate its affect on another variable, called the dependent variable
anything that is detected with the senses
statement describing what always happens under certain conditions in nature
the process of a scientific investigation
broad explanation that is widely accepted as true because it is supported by a great deal of evidence
Did you ever wonder why some dogs turn in a circle before they go to sleep or how birds learn to sing their special songs? If you ever asked questions such as these about the natural world, then you were thinking like a scientist. The word sciencecomes from a Latin word that means “knowledge.”Scienceis a distinctive way of gaining knowledge about the natural world that starts with a question and then tries to answer the question with evidence and logic. Science is an exciting exploration of all the whys and hows that any curious person might have about the world. You can be part of that exploration. Besides your curiosity, all you need is a basic understanding of how scientists think and how science is done, starting with the goal of science.
Now, before we continue, I want to acknowledge that sometimes you might feel like this while reading through this text:
Hang in there though! By the end of this course you will have learned a lot about the world and how it works. Not to mention you can sound really smart by saying (and even understanding) words like: allopatric speciation, notochord and terrestrial biome. If that doesn’t excite you, maybe all the gross dissections and cool & interesting labs will. At any rate, I LOVE biology and I’m going to make you read and do so much biology stuff that you’ll love it too!
O.K. well, you still might not looooooove it. I do hope, however, that you’ll find at least some of the topics this year interesting and fun and perhaps my rampant enthusiasm will rub off a little. For the topics you find absolutely boring, I at least hope they help you understand more about our amazing world God created. Paul says in Romans 1:20,
“For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:”
Biology is the study of the things God made. Studying these things shows us what an amazing God we have and helps us know more about Him. The order, beauty, design and complexity of creation shows us God’s divine nature.
Read the following about how we can know God through His creation:
Psalm 19:1-6: The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they display knowledge. There is no speech or language where their voice is not heard. Their voice goes out into all the earth, their words to the ends of the world.
In the heavens he has pitched a tent for the sun, which is like a bridegroom coming forth from his pavilion, like a champion rejoicing to run his course. It rises at one end of the heavens and makes its circuit to the other; nothing is hidden from its heat. (NIV)
Have you ever felt close to God through nature? Most of us have experienced this sense of God’s presence through nature at one time or another, perhaps while viewing the mountains or walking through the woods or breathing in the salt spray of the ocean. There is a revelation of God in creation, and that is what we want to talk about this morning.
David wrote about this revelation of God in Psalm 19. C. S. Lewis called Psalm 19 “the greatest poem in the Psalter and one of the greatest lyrics in the world.” Psalm 19 has three major sections. The first section is verses 1-6, which focuses on God’s creation. The theme of verses 1-6 is that God’s creation shows his glory. The second section is verses 7-11, which focuses on God’s word. The theme of this section is that God’s word reveals his grace. The last section is verses 12-14, which focuses on our response. The theme of this section is that God requires a humble and repentant response from those who receive his revelation.
1) God’s creation shows his glory (1-6)
2) God’s word reveals his grace (7-11)
3) God’s revelation requires a humble and repentant response (12-14)
We will just be looking at verses 1-6 this morning, which focus on God’s creation and how God’s creation shows his glory. My hope is that through the study of these verses, you will be encouraged to look for God in his creation in new ways and seek to know more of him through his works.
So, how is it that we can know God through his creation?
I. God’s creation declares his glory. (1-2)
Well first of all, God’s creation declares his glory. God has always been glorious. As we saw in the first message of this series, God is the eternal one. God has always been and always will be. God existed as Father, Son and Holy Spirit prior to creation in all of his majesty. He is and always has been perfect in love, perfect in power, perfect in wisdom, perfect in holiness. God has always been glorious. But when God created the heavens and the earth, there was suddenly a new vehicle declaring the eternal glory of God. So how does the creation declare God’s glory?
A. The heavens speak forth the praises of God.
First of all, Psalm 19 says that the heavens speak forth the praises of God. Look at verse one of Psalm 19: “The heavens declare the glory of God; the skies proclaim the work of his hands.” (Psalm 19:1) Although all of creation declares God’s glory, David focuses on the heavens here, because the heavens are the most universally seen of all God’s works. You can also see God’s glory reflected in the mountains and the oceans and the forests and in flowers and wildlife, but not everyone who lives on earth will ever see the ocean or a mountain or certain types of animals. But everyone can see the sky. And so the heavens speak forth the praises of God to everyone on earth.
David describes the skies as “the work of God’s hands.” When we speak about creation, it is not just anyone’s creation. It is God’s creation. It is the work of his hands. Just as you can always see something of the artist in his or her creative works, so you can see something of God in his creative works. The heavens speak forth the praises of God through their beauty, through their complexity, through their incredible balance and order, even through their sheer size as we saw last week. All of these things speak forth the praises of the God who created them.
B. The heavens reveal knowledge of God to man.
The heavens not only speak forth God’s praises. They also reveal knowledge of God to man. Look at verse two of Psalm 19: “Day after day they pour forth speech; night after night they display knowledge.”
The creation does not tell you everything you can know about God, but it does tell you some key things. Paul says in Romans 1:20, “For since the creation of the world God’s invisible qualities — his eternal power and divine nature — have been clearly seen, being understood from what has been made, so that men are without excuse.” God may be a spirit, he may be invisible to our eyes, but the creation reveals some of God’s invisible qualities to us. The size and complexity of creation, especially as seen in the heavens containing the sun, the moon and the stars, show us God’s eternal power. The beauty and order and design of creation show us God’s divine nature.
Albert Einstein was not a Christian believer, and yet as he looked at the wonders of the universe, he knew that there must be a God. When asked by an interviewer if he was an atheist, he replied, no, and explained his answer in this way.
“I’m not an atheist. The problem involved is too vast for our limited minds. We are in the position of a little child entering a huge library filled with books in many languages. The child knows someone must have written those books. It does not know how. It does not understand the languages in which they are written. The child dimly suspects a mysterious order in the arrangement of the books but doesn’t know what it is. That, it seems to me, is the attitude of even the most intelligent human being toward God. We see the universe marvelously arranged and obeying certain laws but only dimly understand these laws.” (First published as “What Life Means to Einstein,” Saturday Evening Post, October 26, 1929. Quoted in Walter Isaacson, Einstein: His Life and Universe; New York: Simon & Schuster, 2007, p. 386.)
Albert Einstein understood the eternal power and divine nature of God from what had been made. Why? Because the creation, and especially the heavens, reveal knowledge of God to man.
C. God’s testimony to himself in creation is unmistakable.
But in these verses David says even more. Not only is there a revelation of God in creation, but God’s testimony to himself in creation is unmistakable. First of all, it is a continuous testimony. We see this in the tenses of the verbs David uses in verse one. We miss it in our English translations, but in the original Hebrew they are all participles, expressing continuous action: “The heavens are declaring the glory of God; the skies are proclaiming the work of his hands.” (Psalm 19:1) In other words, this is something they are always doing at all times.
Look also at David describes this testimony in verse two. He says this testimony takes place “day after day, night after night.” Whether the sun is shining by day or the moon and the stars by night, whether you are enjoying a beautiful, calm, peaceful day or you are in the midst of heart-pounding thunderstorm, there is never any time of day or night when God’s creation is not declaring his glory. It is a continuous testimony.
Not only that, it is an abundant testimony. It would be one thing if this revelation of God was happening all the time, but it was just a small trickle of testimony to God’s glory. But look at the lavish words David uses to describe this testimony. He says, “The skies pour forth speech.” This word translated “pour forth” is a word that means “to bubble up and overflow,” literally “to gush forth” in an uncontrolled and uncontrollable manner. God was not stingy in creation. God has created colors and sounds and variety and wonders in creation everywhere you look. Whether you look deep into the heavens with a high power telescope or deep into the inner workings of a cell with a high power microscope, whether you look up, down or all around, God’s fingerprints are all over creation. God has provided an abundant testimony to himself in creation.
Not only is it a continuous testimony and an abundant testimony, it is also a universal testimony. It is a testimony that is available to everyone who has ever lived in any place at any time. We will talk more about that when we get to verses 3-4 in just a minute. But for right now, let’s just recap what we have learned. God’s creation declares his glory. How? The heavens speak forth the praises of God. The heavens reveal knowledge of God to man. And God’s testimony to himself in creation is unmistakable. God’s creation declares his glory.
II. God’s creation speaks to all people everywhere. (3-4)
Our next point is that God’s creation speaks to all people everywhere. Look at verses 3-4: “There is no speech or language where their voice is not heard. Their voice goes out into all the earth, their words to the ends of the world.” (Psalm 19:3-4) This is the universal aspect of God’s testimony that we were just talking about. God’s creation speaks to all people everywhere.
A. There is no language barrier – it is understood by all.
Just think about it. First of all, there is no language barrier. This revelation of God is understood by all. One of the biggest barriers missionaries face in bringing the gospel to other peoples is the language barrier. For many missionaries, one of their first stops before actually going to the mission field is language school in order to learn the language of the people to whom they will minister. Some missionaries go to tribes where no one knows the language and spend their first couple years just living with the people and learning how to speak their language. New Tribes Missions and Wycliffe Bible Translators are two missions especially dedicated to learning these new languages and translating the Scriptures for these people into their own languages.
But the knowledge of God that comes from creation transcends individual languages. It is like a giant universal translator from Star Trek It can be understood by all who partake in creation. There is no speech or language where the voice of the heavens cannot break through. There is no language barrier – this testimony is understood by all.
B. There is no volume barrier – it is heard by all.
Secondly, there is no volume barrier – it is heard by all. Imagine if you were broadcasting the gospel into a country in the people’s own language, but none of them had their radios turned on, or the signal was so faint they couldn’t pick it up. You would have broken the language barrier, but you would still have a volume barrier. It doesn’t do any good to speak the language if the people can’t hear you.
David says, “There is no speech or language where their voice is not heard.” (Psalm 19:3) The knowledge of God in creation comes through loud and clear to everyone. You can choose to ignore it, but you cannot escape it. Going back to Romans 1:20: “For since the creation of the world God’s invisible qualities — his eternal power and divine nature — have been clearly seen, being understood from what has been made, so that men are without excuse.” Notice that this testimony to God is clearly seen so that men are without excuse. No one will ever be able to stand before God and say that they did not receive the revelation of God that comes through creation. The voice of creation speaks of God’s glory loud and clear, and no one can miss hearing it. They can only refuse to believe what they hear. There is no volume barrier with this revelation – it is heard by all.
C. There is no distance barrier – it is given to all.
Finally, there is no distance barrier – it is given to all. Psalm 19:4: “Their voice goes out into all the earth, their words to the ends of the world.” Going back to the radio analogy, imagine you are broadcasting the gospel using special universal translator technology. Everyone who hears your transmission can understand it. Not only that, everywhere you broadcast, people have their radios on and turned up. They can hear what you are saying. That would be awesome. But how far does your transmission go? What if your transmitter only broadcast to a fifty-mile range, or a hundred-mile range? There would still be a lot of people missing out.
The testimony of creation has no distance barrier. It is given to all. The voice of creation goes out into all the earth, their words to the ends of the world. There is not a place you can go in all the earth where you are not confronted with God’s testimony of himself in creation. There is no distance barrier. This testimony is given to all.
David will use the example of the sun to emphasize this point in the next section, but for right now I want to focus on a different question. You might wonder, “If God’s creation speaks to all people everywhere, then why do we need missionaries? If there are no language, volume or distance barriers with creation, then isn’t that a superior way to tell people about God than sending missionaries? If God’s creation speaks to all people everywhere, isn’t that enough?” And the answer is, no, it is not enough, because although creation provides us with some knowledge of God, it does not provide us with saving knowledge of God.
For example, a person can look at creation and understand that God exists, but knowing that God exists does not save a person. A person can understand from creation that God is all-powerful, holy and wise, but knowing God’s attributes does not save either. A person may even understand through his own conscience that he is a sinner and under God’s judgment, but even knowing that you are a sinner is not enough to save. For that you need Christ.
Let me share three C’s with you:
God gave us the testimony of creation to show that he exists and what he is like.
He gave us the testimony of conscience to show that we are sinners and in need of a savior.
But we need the testimony of Christ in order to believe in God’s Son and be saved.
I like the way the Westminster Confession of Faith puts this:
“Our natural understanding and the works of creation and providence so clearly show God’s goodness, wisdom, and power that human beings have no excuse for not believing in Him. However, these means alone cannot provide that knowledge of God and of His will which is necessary for salvation.” (Westminster Confession of Faith, 1.1)
And so the testimony of creation is not enough by itself. We need to send missionaries with the gospel to share about Christ so that people can come to this great and wonderful God who has revealed himself so clearly in creation.
III. The sun is an example of God’s revelation in creation. (5-6)
Finally, in verses 5-6, David uses the sun in the sky as an example of God’s revelation in creation. “In the heavens he has pitched a tent for the sun, which is like a bridegroom coming forth from his pavilion, like a champion rejoicing to run his course. It rises at one end of the heavens and makes its circuit to the other; nothing is hidden from its heat.” (Psalm 19:5-6)
A. The sun is seen by all on earth.
The sun is a great example first of all because it is seen by all who live on the earth. David uses two different similes here to describe the sun. First he compares it to a groom coming out of his chamber. He imagines God pitching a tent in the heavens for the sun as the sun goes down for the night. Then as morning comes, the sun bursts forth like a bridegroom emerging from his wedding chamber, shining with joy and with love for his new bride.
Then David switches the image to that of a champion running a race. The champion rejoices in his power and strength as he runs his course. In the same way the sun rises each day and makes its way across the heavens. Never faltering, never tiring, it rises at one end of the heavens and makes its circuit to the other. It is seen by all who live on earth, every morning, every day, without fail.
B. The sun serves all who live on earth.
The sun also serves all who live on the earth. “Nothing is hidden from its heat.” Even on the cloudiest, darkest day, the light of the sun illumines and warms the surface of the earth. God gave the sun to provide light and heat for everyone. It is part of his common grace to all mankind. You can hate God, you can rebel against God, you can curse God to his face; but he still “causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.” (Matthew 5:45) No matter where you live, you cannot escape the testimony of the sun, which testifies every day to a good and powerful and gracious God.
CONCLUSION: So, what should our response to all this be? Let me leave you with two warnings, one reminder and then one main action point.
1. First of all, do not mistake nature for God. Some people feel that sense of God’s presence in nature and mistake it for God himself. But God is not his creation. The creation should cause you to worship God the creator, not his creation.
2. Secondly, do not mistake nature for Christ. Some people feel that nature brings them closer to God. They speak of communing with God through nature. But only Christ can bring you closer to God. There is only one mediator between God and man, and that is not nature, but Jesus Christ.
3. Thirdly, remember that the present creation is distorted by sin. God created all things good, but man’s sin has affected God’s good creation. So not everything you see in creation will be a true reflection of God. For example, disease is a part of creation that afflicts man because of sin. If you did not know that, you might look at certain viruses or diseases and conclude that God was evil or cruel. We need to remember that the present creation is distorted by sin.
4. And then finally, the main action point, learn to know and enjoy God through his creation. As we said before, David especially focused on the heavens in these verses, because the heavens are the most universally seen of all God’s works. But you can see God in all that he has created. John Calvin wrote about these verses:
When a man, from beholding and contemplating the heavens, has been brought to acknowledge God, he will learn also to reflect upon and to admire his wisdom and power as displayed on the face of the earth, not only in general, but even in the minutest of plants.” (Institutes I:308-309)
There is so much we can learn about God from the book of creation. And so it is important that we spend time with God in his creation: watching the sun rise or set and the seasons turn, staring up in awe at the stars in the heavens, walking in nature away from the hustle and bustle of human activity, resting in the fields and the streams, delighting in God’s animals and creatures. All of these things teach us more about God and draw us to praise and to worship him in deeper and better ways.
Yes, we need to read this book (the Bible) in order to know God’s dealings with man, his will for us, his provision for our salvation, his revelation in Christ. In fact, it is only as we learn of God from this book (the Bible), that we can truly begin to read the book of creation as God intended. So let’s make sure we spend sufficient time in this book (the Bible). But we must also take time to read and enjoy the book of creation. For we can also know and love and worship our great God through his amazing and beautiful creation that speaks forth his praises to everyone, everywhere, every day.
The goal of science is to understand the natural world. To achieve this goal, scientists make certain assumptions. They assume that:
Nature can be understood through systematic study.
Scientific ideas are open to revision.
Sound scientific ideas withstand the test of time.
Science cannot provide answers to all questions.
Nature Can Be Understood
Scientists think of nature as a single system controlled by natural laws. By discovering natural laws, scientists strive to increase their understanding of the natural world. Laws of nature are expressed as scientific laws. Ascientific lawis a statement that describes what always happens under certain conditions in nature.
An example of a scientific law is the law of gravity, which was discovered by Sir Isaac Newton (seeFigurebelow). The law of gravity states that objects always fall towards Earth because of the pull of gravity. Based on this law, Newton could explain many natural events. He could explain not only why objects such as apples always fall to the ground, but he could also explain why the moon orbits Earth. Isaac Newton discovered laws of motion as well as the law of gravity. His laws of motion allowed him to explain why objects move as they do.
Did Newton discover the law of gravity when an apple fell from a tree and hit him on the head? Probably not, but observations of nature are often the starting point for new ideas about the natural world.
Scientific Ideas Can Change
Science is more of a process than a set body of knowledge. In other words, what we think we know can change based on new evidence. Scientists are always testing and revising their ideas, and as new observations are made, existing ideas may be challenged. Ideas may be replaced with new ideas that better fit the facts, but more often existing ideas are simply revised.
For example, when Albert Einstein developed his theory of relativity, he didn’t throw out Newton’s laws of motion. Instead, he showed that Newton’s laws are a small piece of a bigger picture. In this way, scientists gradually build an increasingly accurate and detailed understanding of the natural world.
Here are some scientific ideas that have changed as people gained more knowledge over time:
Spontaneous Generation – People used to believe that life came from things like earth after being exposed to sunlight, mud, or slime. They thought that things could “magically” come from nothing. Aristotle (a famous Greek philosopher) based his ideas of this from observations of maggots appearing on rotten meat and barnacles forming on a boat’s hull. It wasn’t until the 1600 and 1700’s that this idea began to be disproved.Here’s an interesting thought about this…scientists now say that something cannot come from nothing. It’s impossible! Everything comes from something. A plant comes from a seed. Maggots come from eggs deposited from flies. Mold grows from spores that came from other mold plants and so on. Yet, many scientists still say our universe came into existence via the “Big Bang” from nothing. Does that make sense? If scientists have proved that something cannot come from nothing, then why do they insist on contradicting themselves with the origin of our universe? Stephen Hawking (a very famous physicist and cosmologist) says that due to quantum gravity the universe could have created itself out of nothing. Yet, even he points out in his book “The Grand Design” that the nothingness he is referring to is actually space filled with vacuum energy. Hmmm…where did the vacuum energy come from then? It gets a bit complicated and into the realm of metaphysics (a branch of philosophy dealing with explaining “What is there?” and “What is it like?”) but still, in my opinion, Mr. Hawking is contradicting his own statement that the universe came from “nothing”. Gravity isn’t nothing. It might not be composed of matter, but it’s still a thing that exists. Vacuum energy isn’t nothing. Where did the energy come from? It’s still a something. Anyway, what I’m trying to point out is that even a scientist who says we came from nothing, doesn’t really back that up. Something cannot come from nothing. That’s just the way it is! Of course, as Christians, we understand that everything was created by God. The fact that spontaneous generation was disproved is just a small piece of the creation puzzle that fits!
Phlogiston – Scientists used to believe that anything that caught fire had a special element inside it called phlogiston that was released during burning and made the whole process possible. This was eventually proven wrong.
Martian Canals – An astronomer in the 1800’s first saw what he believed to be canals on Mars. Other astronomers and scientists claimed to also see the canals and theories were developed as to what their possible origins and use were. It was even proposed that they were created by an intelligent species for irrigation. Eventually this was discredited! Er, it was, right? Otherwise we’d better prepare for a Martian invasion!
As you can see, just because scientists or people believe something, doesn’t make it true. Scientific ideas can change or even be throw out with new evidence.
THE SCIENTIFIC METHOD
One neat thing about science is that there is so much left to discover and figure out. Discoveries can be made using the scientific method.
Scienctific discoveries don’t have to be made by adults in lab coats. They can be made by anyone through observation, questioning and experimenting. That’s why YOU could be the next person to make a break-through! First, you need to know how to go about it though. That takes knowing how the scientific method works.
The Scientific Method generally follows the steps listed inFigurebelow.
Steps of a Scientific Investigation. A scientific investigation typically has these steps.
A scientific investigation typically begins with observations. You make observations all the time. Let’s say you take a walk in the woods and observe a moth, like the one inFigurebelow, resting on a tree trunk. You notice that the moth has spots on its wings that look like eyes. Yeah, look at those eyes. Think about them when you are going to sleep tonight.
Anyway, you think the eye spots make the moth look like the face of an owl (or maybe one of those Martians that dug the canals on Mars).
Does this moth remind you of an owl?
Asking a Question
Observations often lead to questions. You might ask yourselfwhythe moth has eye spots that make it look like an owl’s face.
Forming a Hypothesis (which is just a fancy word for “guess”)
The next step in a scientific investigation is forming a hypothesis (a guess). A hypothesisis a possible answer to a scientific question, but it isn’t just any answer. A hypothesis must be based on scientific knowledge, and it must be logical. A hypothesis also must be falsifiable. That just means it must be possible to make observations that would disprove the hypothesis if it really is false. Assume you know that some birds eat moths and that owls prey on other birds. From this knowledge, you reason that eye spots scare away birds that might eat the moth. This is your hypothesis.
Testing the Hypothesis
To test a hypothesis, you first need to make a prediction based on the hypothesis. Apredictionis a statement that tells what will happen under certain conditions. It can be expressed in the form: If A occurs, then B will happen (don’t worry, we aren’t getting into math, even if it sounds like it). Based on your hypothesis, you might make this prediction: If a moth has eye spots on its wings, then birds will avoid eating it.
Next, you need to get evidence to test your prediction.Evidenceis any type of facts that may either agree or disagree with a prediction, so it may either support or disprove a hypothesis. Assume that you gather evidence by making more observations of moths with eye spots. Perhaps you observe that birds reallydo avoid eating the moths. This evidence agrees with your prediction.
Evidence that agrees with your prediction supports your hypothesis. Does such evidence prove that your hypothesis is true? No; a hypothesis cannot be proven conclusively to be true, which just means you can never totally put a 100% end to any doubt or questions about it. This is because you can never examine all of the possible evidence, and someday evidence might be found that disproves the hypothesis (like how good telescopes proved that there are no canals on Mars). Still, the more evidence that supports a hypothesis, the more likely the hypothesis is to be true.
The last step in a scientific investigation is communicating what you have learned with others. This is a very important step because it allows others to test your hypothesis. If other researchers get the same results as yours, they add support to the hypothesis. However, if they get different results, they may disprove the hypothesis. When scientists share their results, they should describe their methods and point out any possible problems with the investigation. For example, while you were observing moths, perhaps your presence scared birds away. This introduces an error into your investigation. You got the results you predicted (the birds avoided the moths while you were observing them), but not for the reason you hypothesized.
Mentioning the whole canals on Mars issue again, it was discovered that there was an optical illusion that came about because, when a poor-quality telescope views many point-like features, such as craters, they appear to join up to form lines. The original belief in Martian canals was based on an error that other observers were able to point out because the observations were shared. Communicating results can also help scientists to avoid some of the same types of errors in future observations and work.
Figurebelow shows a laboratory experiment involving plants. Anexperimentis a special type of scientific investigation that is performed under controlled conditions, usually in a laboratory. Some experiments can be very simple, but even the simplest contributed important evidence that helped scientists better understand the natural world. An example experiment can be seen here: http://www.youtube.com/watch?v=F10EyGwd57M (How much sugar is in a can of soda?).
A laboratory experiment studying plant growth. What might this experiment involve?
An experiment generally tests how one variable is affected by another. The affected variable is called thedependent variable. In the plant experiment shown above, the dependent variable is plant growth. The variable that affects the dependent variable is called theindependent variable. In the plant experiment, the independent variable is fertilizer—some plants will get fertilizer, others will not. In any experiment, other factors that might affect the dependent variable must be controlled. In the plant experiment, what factors do you think should be controlled? (Hint:What other factors might affect plant growth?) (Think: water, light, etc.)
The next two videos should help you understand variables:
Scientific Variables Video
The Variables Song by Mr. Edwards
Sample Size and Repetition
The sample in an experiment or other investigation consists of the individuals or events that are studied. Typically, the sample is much smaller than all such individuals or events that exist in the world. Whether the results based on the sample are true in general cannot be known for certain. However, the larger the sample is, the more likely it is that the results are generally true. An example of this would be if you studied a set of 3 plants to see if club soda could make them grow better. If 2 of the plants died, you might think club soda was not good for plant growth. Your results would be more reliable if you did the test with 25 plants. If you repeated the test with 25 plants you would probably get more accurate results. Perhaps there was a different factor that caused the plants to die that had nothing to do with the club soda. By the way, club soda supposedly does actually help plant growth!
Similarly, the more times that an experiment is repeated and the same results obtained, the more likely the results are valid. This is why scientific experiments should always be repeated.
OTHER TYPES OF SCIENTIFIC INVESTIGATIONS
Experiments are sometimes hard or even impossible to do. For example, a scientist who is studying an extinct animal cannot experiment with the animal because it no longer exists. The scientist must rely instead on evidence in the natural world, such as fossils that the extinct animal left behind.
When scientists do studies in nature, they usually can’t control factors that might affect the variables they are investigating. This is a drawback, because it may make the observations difficult to interpret. Without controls, it may not be possible to determine which of many factors explain the observations. For example, assume you are studying how plants grow in a forest or field. You can’t control the amount of sunlight or rain water the plants receive, so it will be difficult to determine which factors most influence plant growth. On the other hand, a natural study shows what actually occurs in nature. Therefore, it may provide a truer picture of what happens in the real world than an experiment conducted indoors or in the laboratory does.
Another way to gain scientific knowledge without experiments is by making and manipulating models. Amodelis a representation of part of the real world. Did you ever build a model car? Scientific models are something like model cars; they represent the real world but are simpler than the real world. This is one reason that models are especially useful for investigating complex systems. By using a model, scientists can better understand how the real system works. An example of a scientific model is shown inFigurebelow. Do you know what systems these two models represent?
Food Chains. These two food chains represent complex systems in nature. They make the systems easier to understand. These are simple conceptual models. Models of very complex systems are often based on mathematical equations or computer simulations.
Like a hypothesis, a model must be evaluated. It is assessed by criteria such as how well it represents the real world, what limitations it has, and how useful it is. The usefulness of a model depends on how well its predictions match observations of the real world. Even when a model’s predictions match real-world observations, however, it doesn’t prove that the model is true or that it is the only model that works.
With repeated testing, some hypotheses may eventually become scientific theories. Ascientific theoryis a broad explanation for events that is widely accepted as true. To become a theory, a hypothesis must be tested over and over again, and it must be supported by a great deal of evidence. People commonly use the wordtheoryto describe a guess about how or why something happens. For example, you might say, “I think a woodchuck dug this hole in the ground, but it’s just a theory.” Using the wordtheoryin this way is different from the way it is used in science. A scientific theory is more like a fact than a guess because it is so well-supported. There are several well-known theories in biology, like cell theory and germ theory. Another theory is evolution. Remember though, just because something is a theory, doesn’t mean it’s true. Hundreds of years ago Spontaneous Generation was a theory. New evidence and understanding disproved it.
KQED: BIO-INSPIRATION: NATURE AS MUSE
For hundreds of years, scientists have been using design ideas from structures in nature. Now, biologists and engineers at the University of California, Berkeley are working together to design a broad range of new products, such as life-saving milli-robots modeled on the way cockroaches run and adhesives based on the amazing design of a gecko’s foot. This process starts with making observations of nature, which lead to asking questions and to the additional aspects of the scientific process.
The goal of science is to understand the natural world through systematic study. Scientific knowledge is based on evidence and logic.
Scientists gain knowledge through scientific investigations. A scientific investigation is a plan for asking questions and testing possible answers.
Scientists use experiments to test hypotheses under controlled conditions. Experiments are often done in a lab.
Other types of scientific investigations include natural studies and modeling. They can be used when experiments are difficult to do.
Scientific theories are broad explanations that are widely accepted as true. This is because they are supported by a great deal of evidence.
LESSON REVIEW QUESTIONS
1. What is science? What is the goal of science?
2. Outline the steps of a scientific investigation.
3. What is a scientific hypothesis? What characteristics must a hypothesis have to be useful in science?
4. Give an example of a scientific question that could be investigated with an experiment. Then give an example of scientific question that could not be investigated in this way.
5. What might be an advantage of collecting evidence in a natural setting rather than in a lab?
6. Identify the independent and dependent variables in the following experiment:
A scientist grew bacteria on gel in her lab. She wanted to find out if the bacteria would grow faster on gel A or gel B. She placed a few bacteria on gel A and a few on gel B. After 24 hours, she observed how many bacteria were present on each type of gel.
7. Contrast how the termtheoryis used in science and in everyday language.
8. Explain how a hypothesis could become a theory.
POINTS TO CONSIDER
The Points to Consider at the end of each lesson in this book will help you relate what you just learned to what is coming next. The questions will help guide you to the next lesson or chapter. Before reading the next lesson of this chapter, consider these points:
Remember the opening photo of red blood cells and green viruses? The blood cells are cells of a living thing. Do you think that the viruses are living things? Why or why not?
Lab experiments are the main method of gathering evidence in some branches of science. Why might lab experiments not be the best way to study living things, such as wild animals?