CK-12 Biology I - Honors Read online

  Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution/Non-Commercial/Share Alike 3.0 Unported (CC-by-NC-SA) License (http://creativecommons.org/licenses/by-nc-sa/3.0/), as amended and updated by Creative Commons from time to time (the "CC License"), which is incorporated herein by this reference. Specific details can be found from http://www.ck12.org/terms. ISBN :9781935983040

  Chapter 1: Foundations of Life Science

  Nature of Science

  Lesson Objectives

  List the principles that should guide scientific research.

  Examine a scientist’s view of the world.

  Outline a set of steps that might be used in the scientific method of investigating a problem.

  Explain why a control group is used in an experiment.

  Outline the role that reasoning plays in examining hypotheses.

  Examine the function of the independent variable in an experiment.

  Define what is meant by a theory and compare this to the meaning of hypothesis.

  Introduction

  The goal of science is to learn how nature works by observing the physical world, and to understand it through research and experimentation. Science is a distinctive way of learning about the natural world through observation, inquiry, formulating and testing hypotheses, gathering and analyzing data, and reporting and evaluating findings. We are all part of an amazing and mysterious phenomenon called "Life" that thousands of scientists everyday are trying to better explain. And it's surprisingly easy to become part of this great discovery! All you need is your natural curiosity and an understanding of how people use the process of science to learn about the world.

  Goals of Science

  Science involves objective, logical, and repeatable attempts to understand the principles and forces working in the natural universe. Science is from the Latin word, scientia, which means “knowledge.” Good science is an ongoing process of testing and evaluation. One of the intended benefits for students taking a biology course is that they will become more familiar with the scientific process.

  Humans are naturally interested in the world we live in. Young children constantly ask "why" questions. Science is a way to get some of those “whys” answered. When we shop for groceries, we are carrying out a kind of scientific experiment (Figure below). If you like Brand X of salad dressing, and Brand Y is on sale, perhaps you try Brand Y. If you like Y you may buy it again even when it is not on sale. If you did not like Brand Y, then no sale will get you to try it again. To find out why a person makes a particular purchasing choice, you might examine the cost, ingredient list, or packaging of the two salad dressings.

  Figure 1.1

  Shopping sometimes involves a little scientific experimentation. You are interested in inventing a new type of salad that you can pack for lunch. You might buy a vegetable or salad dressing that you have not eaten before, to discover if you like it. If you like it, you will probably buy it again. That is a type of experiment.

  There are many different areas of science, or scientific disciplines, but all scientific study involves:

  asking questions

  making observations

  relying on evidence to form conclusions

  being skeptical about ideas or results

  Skepticism is an attitude of doubt about the truthfulness of claims that lack empirical evidence. Scientific skepticism, also referred to as skeptical inquiry, questions claims based on their scientific verifiability rather than accepting claims based on faith or anecdotes. Scientific skepticism uses critical thinking to analyze such claims and opposes claims which lack scientific evidence.

  A Scientific View of the World

  Science is based on the analysis of things that humans can observe either by themselves through their senses, or by using special equipment. Science therefore cannot explain anything about the natural world that is beyond what is observable by current means. The term supernatural refers to entities, events, or powers regarded as being beyond nature, in that such things cannot be explained by scientific means. They are not measurable or observable in the same way the natural world is, and so considered to be outside the realm of scientific examination.

  When a natural occurrence which was once considered supernatural is understood in the terms of natural causes and consequences, it has a scientific explanation. For example, the flickering lights sometimes seen hovering over damp ground on still evenings or nights are commonly called Will-o'-the-wisp. This phenomena looks like a lamp or flame, and is sometimes said to move away if approached. A great deal of folklore surrounds the legend, such as the belief that the lights are lost souls or fairies attempting to lead travelers astray. However, science has offered several potential explanations for Will-o'-the-wisp from burning marsh gases to glowing fungi or animals that glow in a similar way to lightning bugs.

  There is no fixed set of steps that scientists always follow and there is no single path that leads to scientific knowledge. There are, however, certain features of science that give it a very specific way of investigating something. You do not have to be a professional scientist to think like a scientist. Everyone, including you, can use certain features of scientific thinking to think critically about issues and situations in everyday life.

  Science assumes that the universe is a vast single system in which the basic rules are the same, and thus nature, and what happens in nature, can be understood. Things that are learned from studying one part of the universe can be applied to other parts of the universe. For example, the same principles of motion and gravitation that explain the motion of falling objects on Earth also explain the orbit of the planets around the sun, and galaxies, as shown in Figure below. As discussed below, as more and more information and knowledge is collected and understood, scientific ideas can change, still scientific knowledge usually stands the test of time. Science, however, cannot answer all questions.

  Figure 1.2

  With some changes over the years, similar principles of motion have applied to different situations. The same scientific principles that help explain planetary orbits can be applied to the movement of a Ferris wheel.

  Nature Can Be Understood

  Science presumes that events in the universe happen in patterns that can be understood by careful study. Scientists believe that through the use of the mind, and with the help of instruments that extend the human senses, people can discover patterns in all of nature that can help us understand the world and the universe.

  Scientific Ideas Can Change

  Science is a process for developing knowledge. Change in knowledge about the natural world is expected because new observations may challenge the existing understanding of nature. No matter how well one theory explains a set of observations, it is possible that another theory may fit just as well or better, or may fit a still wider range of observations. In science, the testing and improving of theories goes on all the time. Scientists know that even if there is no way to gain complete knowledge about something, an increasingly accurate understanding of nature will develop over time.

  The ability of scientists to make more accurate predictions about the natural world, from determining how a cancerous tumor develops a blood supply, to calculating the orbit of an asteroid, provides evidence that scientists are gaining an understanding of how the world works.

  Scientific Knowledge Can Stand the Test of Time

  Continuity and stability are as much characteristics of science as change is. Although scientists accept some uncertainty as part of nature, most scientific knowledge stands the test of time. A changing of ideas, rather than a complete rejection of the ideas, is the usual pra
ctice in science. Powerful ideas about nature tend to survive, grow more accurate and become more widely accepted.

  For example, in developing the theory of relativity, Albert Einstein did not throw out Issac Newton’s laws of motion but rather, he showed them to be only a small part of the bigger, cosmic picture. That is, the Newtonian laws of motion have limited use within our more general concept of the universe. For example, the National Aeronautics and Space Administration (NASA) uses the Newtonian laws of motion to calculate the flight paths of satellites and space vehicles.

  Science Cannot Offer Answers to All Questions

  There are many things that cannot be examined in a scientific way. There are, for instance, beliefs that cannot be proved or disproved, such as the existence of supernatural powers, supernatural beings, or the meaning of life. In other cases, a scientific approach to a question and a scientific answer may be rejected by people who hold to certain beliefs.

  Scientists do not have the means to settle moral questions surrounding good and evil, or love and hate, although they can sometimes contribute to the discussion of such issues by identifying the likely reasons for certain actions by humans and the possible consequences of these actions.

  Scientific Methods

  It can be difficult sometimes to define research methods in a way that will clearly distinguish science from non-science. However, there is a set of core principles that make up the “bones” of scientific research. These principles are widely accepted within the scientific community and in academia.

  We learned earlier in this lesson that there is no fixed set of steps that scientists always follow during an investigation. Similarly, there is no single path that leads scientists to knowledge. There are, however, certain features of science that give it a very specific way of investigating things.

  Scientific investigations examine, gain new knowledge, or build on previous knowledge about phenomena. A phenomenon, is any occurrence that is observable, such as the burning match shown in Figure below. A phenomenon may be a feature of matter, energy, or time. For example, Isaac Newton made observations of the phenomenon of the moon's orbit. Galileo Galilei made observations of phenomena related to swinging pendulums. Although procedures vary from one field of scientific inquiry to another, certain features distinguish scientific inquiry from other types of knowledge. Scientific methods are based on gathering observable, empirical (produced by experiment or observation), and measurable evidence that is critically evaluated.

  Figure 1.3

  The combustion of this match is an observable event and therefore a phenomenon.

  A hypothesis is a suggested explanation based on evidence that can be tested by observation or experimentation. Experimenters may test and reject several hypotheses before solving a problem. A hypothesis must be testable; it gains credibility by being tested over and over again, and by surviving several attempts to prove it wrong.

  Scientific Investigations

  The scientific method is not a step by step, linear process. It is a way of learning about the world through the application of knowledge. Scientists must be able to have an idea of what the answer to an investigation is. Scientists will often make an observation and then form a hypothesis to explain why a phenomenon occurred. They use all of their knowledge and a bit of imagination in their journey of discovery.

  Scientific investigations involve the collection of data through observation, the formation and testing of hypotheses by experimentation, and analysis of the results that involves reasoning.

  Scientific investigations begin with observations that lead to questions. We will use an everyday example to show what makes up a scientific investigation. Imagine that you walk into a room, and the room is dark.

  You observe that the room appears dark, and you question why the room is dark.

  In an attempt to find explanations to this phenomenon, you develop several different hypotheses. One hypothesis might state that the room does not have a light source at all. Another hypothesis might be that the lights are turned off. Still, another might be that the light bulb has burnt out. Worse yet, you could be going blind.

  To discover the answer, you experiment. You feel your way around the room and find a light switch and turn it on. No light. You repeat the experiment, flicking the switch back and forth; still nothing.

  This means your first two hypotheses, that the room is dark because (1) it does not have a light source; and (2) the lights are off, have been rejected.

  You think of more experiments to test your hypotheses, such as switching on a flashlight to prove that you are not blind.

  In order to accept your last remaining hypothesis as the answer, you could predict that changing the light bulb will fix the problem. If your predictions about this hypothesis succeed (changing the light bulb fixes the problem), the original hypothesis is valid and is accepted.

  However, in some cases, your predictions will not succeed (changing the light bulb does not fix the problem), and you will have to start over again with a new hypothesis. Perhaps there is a short circuit somewhere in the house, or the power might be out.

  The general process of a scientific investigation is summed up in Figure below.

  Figure 1.4

  The general process of scientific investigations. A diagram that illustrates how scientific investigation moves from observation of phenomenon to a theory. The progress is not as straightforward as it looks in this diagram. Many times, every hypothesis is falsified which means the investigator will have to start over again.

  Common Terms Used in Scientific Investigations Term Definition

  Scientific Method The process of scientific investigation.

  Observation The act of noting or detecting phenomenon by the senses. For example, taking measurements is a form of observation.

  Hypotheses A suggested explanation based on evidence that can be tested by observation or experimentation.

  Scientific Reasoning The process of looking for scientific reasons for observations.

  Experiment A test that is used to rule out a hypothesis or validate something already known.

  Rejected Hypothesis An explanation that is ruled out by experimentation.

  Confirmed Hypothesis An explanation that is not ruled out by repeated experimentation, and makes predictions that are shown to be true.

  Inference Developing new knowledge based upon old knowledge.

  Theory A widely accepted hypothesis that stands the test of time. Theories are often tested, and usually not rejected.

  Making Observations

  Scientists first make observations that raise questions. An observation is the act of noting or detecting phenomenon through the senses. For example, noting that a room is dark is an observation made through sight.

  Developing Hypotheses

  In order to explain the observed phenomenon, scientists develop a number of possible explanations, or hypotheses. A hypothesis is a suggested explanation for a phenomenon or a suggested explanation for a relationship between many phenomena. Hypotheses are always based on evidence that can be tested by observation or experimentation. Scientific investigations are required to test hypotheses. Scientists mostly base hypotheses on prior observations or on extensions of existing scientific explanations.

  A hypothesis is not really an educated guess. To define a hypothesis as "an educated guess" is like calling a tricycle a "vehicle with three." The definition leaves out the concept's most important and characteristic feature: the purpose of hypotheses. People generate hypotheses as early attempts to explain patterns observed in nature or to predict the outcomes of experiments. For example, in science, one could correctly call the following statement a hypothesis: identical twins can have different personalities because the environment influences personality.

  Evaluating Hypotheses

  Scientific methods require hypotheses that are falsifiable, that is, they must be framed in a way that allows other scientists to prove them false. Proving a hypothesis to be false
is usually done by observation. However, confirming or failing to falsify a hypothesis does not necessarily mean the hypothesis is true.

  For example, a person comes to a new country and observes only white sheep. This person might form the hypothesis: “All sheep in this country are white.” This statement can be called a hypothesis, because it is falsifiable - it can be tested and proved wrong; anyone could falsify the hypothesis by observing a single black sheep, shown in Figure below. If the experimental uncertainties remain small (could the person reliably distinguish the observed black sheep from a goat or a small horse), and if the experimenter has correctly interpreted the hypothesis, finding a black sheep falsifies the "only white sheep" hypothesis. However, you cannot call a failure to find non-white sheep as proof that no non-white sheep exist.

  Figure 1.5

  The statement there are only white sheep in this country is a scientific hypothesis because it is open to being falsified. However, a failure to see a black sheep will not necessarily falsify the hypothesis.

  Scientific Reasoning

  Any useful hypothesis will allow predictions based on reasoning. Reasoning can be broken down into two categories: deduction and induction. Most reasoning in science is done through induction.

  Deductive Reasoning (Deduction)

  Deduction involves determining a single fact from a general statement; it is only as accurate as the statement.