CK-12 Life Science Read online

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  Chapter 1: Studying Life

  Lesson 1.1: The Nature of Science

  Lesson Objectives

  Understand that science is a system based on evidence, testing, and reasoning.

  Describe what the life sciences are and some of the many life science specialties.

  Describe the scientific method and why it is important.

  Define the words "fact," "theory," and "hypothesis."

  Describe some of the tools of life science.

  Know that scientists are required to follow strict guidelines.

  Check Your Understanding

  What do you expect to learn from this class?

  Introduction

  Before proceeding through this class, you need to realize a number of fundamental concepts of science. You need to:

  Know that science is a way of knowing about the physical world, based on observable evidence, testing predictions, and reasoning

  Understand that, in science, theories and knowledge are constantly tested and questioned.

  Know that, when new information conflicts with existing explanations, scientists modify their explanations to be consistent with all evidence.

  Understand that principles of philosophy and religion usually cannot be tested scientifically, because they are not based on observable evidence.

  Identify what the life sciences are and some of the many specialties

  Know the difference between scientific theory and fact.

  These raise several interesting questions:

  Why is modern science producing many more improvements in our lives than it did a hundred years ago? Modern science is based on evidence, inquiry and testing which have replaced personal beliefs, mythology and other biased sources of information.

  Is there anything that science cannot explain? Yes there is. Questions about ethics (right and wrong) and belief in supernatural forces can not be explained through science.

  How can we "think like scientists?" To think like a scientist, you would need to: ask questions about the world around you and seek new evidence that will help answer questions,

  base your understanding of the world on evidence, testing and reasoning instead of biased belief systems,

  continuously question and test the accuracy of your knowledge and assumptions (including so-called "common sense").

  Goals of Science

  Science, religion, mythology, and magic share the goal of knowing about and explaining the world, such as the physical world, but their approaches are vastly different. The difference between them is their approach to “knowing.” The vastness of the living, physical world includes all organisms (Figure below), on land (Figure below) and in the sea (Figure below). As humans, some of the things we want to know and understand are what makes us healthy, what makes us sick, and how we can protect ourselves from floods, famine and drought.

  Figure 1.1

  bacteria

  Figure 1.2

  A male lion.

  Figure 1.3

  A Humpback whale.

  Throughout history, humans have looked for ways to understand and explain the physical world. Try to imagine what humans thought about themselves and the world around them 1,000 years ago, or 5,000 years ago, or more. If you were born then, how would you have explained why the sun moved across the sky, then disappeared? How would you explain why your body changes as you grow, or birth and death? What explanation would you have for lightning, thunder, and storms?

  Throughout time, different cultures have created hundreds of different myths and stories and even gods to explain what they saw. Ancient Greeks explained that lightning was a show of their god Zeus’ anger. Scandinavians claimed that their god of thunder, Thor, was responsible for the rumbling and bolts of lightning. Without any formal science, many cultures have also blamed diseases, such as epilepsy, on evil spirits and other imaginary entities. For example, there is evidence that many different cultures drilled holes in the skulls of patients who had seizures or other maladies, thinking that they were releasing evil spirits.

  Science as a Way of Knowing

  During your own and your parents’ lifetimes, advances in medicine (Figure below), technology, and other fields have progressed faster than any other time in history. This explosion of advances in our lives is largely due to human use of modern science as a way of understanding. Today’s scientists are trained to base their comprehension of the world on evidence and reasoning rather than belief and assumptions.

  Figure 1.4

  The anatomy lesson of Dr. Nicolaes Tulp.

  Modern science is:

  A way of understanding about the physical world, based on observable evidence, reasoning, and repeated testing.

  A body of knowledge that is based on observable evidence, experimentation, reasoning, and repeated testing.

  As we learn more, new information occasionally conflicts with our current understanding. When this happens scientific explanations are revised. The Figure below demonstrates this. However, science cannot scrutinize what is good versus what is bad (morality), because these are values, ideas that lack measurable evidence. Science is not used to examine philosophy or supernatural entities, such as the existence or nonexistence of a god. However, science can be used to examine the effects of these experiences.

  Figure 1.5

  In 1847, a doctor, Ignaz Semmelweis, demonstrated that when he washed his hands before delivering babies fewer women died from infection. Before this, doctors held untested beliefs about the causes of disease, such as a persons behavior, or the air they breathed.

  The most important message from this chapter is that science is not only a way of knowing it is also a way of thinking and reasoning. Scientists try to look at the world objectively - without bias or making assumptions. How? Scientists learn to be skeptical, to question the accuracy of our ideas. They learn to base their understanding of the physical world on evidence, reasoning and repeated testing of ideas.

  To Think Like a Scientist

  To think like a scientist, you need to be skeptical about and question your assumptions, including what often seems like common sense. Questioning ideas can often lead to surprising results. For example, if you ask people whether it's easier to keep a plastic cutting board clean or a wooden one clean, most people will think that the plastic board is easier to keep clean and has fewer germs (Figure below ).

  Figure 1.6

  Which is safer, a plastic or wood cutting board?

  Why do most people believe that plastic is safer? Probably because we assume that it is easier to wash germs off plastic than off wood. This assumption is promoted by the makers of plastic cutting boards and it sounds reasonable. After all, wood stains and looks unhygienic; plastic cutting boards come out of the dishwasher shiny and clean looking. But is plastic actually better?

  When scientists tested this idea, the answer turned out to be no. The researchers treated used cutting boards with different kinds of germs and then washed the boards. They found, much to their surprise, that gouged and sliced wooden cutting boards had far fewer germs than gouged and sliced plastic boards. The researchers discovered that germs that cause food poisoning, such as E. coli and Salmonella, are absorbed into the wood and seemed to vanish. On plastic, the germs sit on the surface in cuts in the plastic wh
ere they are difficult to clean out but can contaminate food. Furthermore, in a different study of food poisoning, people who used wooden cutting boards were less than half as likely to get sick as people using plastic ones.

  "Common sense" may seem to have all the answers, but science is all about following the evidence. So what is good evidence? Evidence is information that can be used to confirm or refute an idea or to explain something. Both scientists and lawyers use evidence to support an idea or to show that an idea is probably wrong. Scientific evidence has certain features, which may be different from legal evidence.

  Evidence is:

  a direct, physical observation of a thing, a group of things, or of a process over time.

  usually something measurable or "quantifiable."

  the result of something.

  For example, a book falling to the ground is evidence in support of the theory of gravity. A bear skeleton in the woods would be supporting evidence for the presence of bears.

  What Are the Life Sciences?

  The life sciences are the study of living organisms and how they interact with each other and their environment. These include all the biological sciences. Life sciences deal with every aspect of living organisms. The life sciences are so complex that most scientists focus on just one or two subspecialties — see tables "Subspecialties that focus on one type of organism", "Fields of life sciences that examine the structure, function, growth, development and/or evolution of living things", and "Fields of biology that examine the distribution and interactions between organisms and their environments". Also, some focus on the relationship between living organisms, which is depicted in a phylogenetic “Tree of Life” (Figure below the tables).

  Subspecialties that focus on one type of organism Subspecialty Studies Subspecialty Studies

  Botany plants Zoology animals

  Marine biology organisms living in and around oceans, and seas Fresh water biology organisms living in and around freshwater lakes, streams, rivers, ponds, etc.

  Microbiology microorganisms Bacteriology bacteria

  Virology viruses Entomology insects

  Taxonomy the classification of organisms

  Fields of life sciences that examine the structure, function, growth, development and/or evolution of living things Life Science What it Examines Life Science What it Examines

  Cell biology cells and their structures Anatomy the structures of animals

  Morphology the form and structure of living organisms Physiology the physical and chemical functions of tissues and organs

  Immunology the mechanisms inside organisms that protect them from disease and infection Neuroscience the nervous system

  Developmental biology and embryology the growth and development of plants and animals Genetics the genetic make up of all living organisms (heredity)

  Biochemistry the chemistry of living organisms Molecular biology biology at the molecular level

  Epidemiology how diseases arise and spread (Figure below)

  Fields of biology that examine the distribution and interactions between organisms and their environments Life Science What it Examines Life Science What it Examines

  Ecology how various organisms interact with their environments Biogeography the distribution of living organisms (Figure below)

  Population biology the biodiversity, evolution, and environmental biology of populations of organisms

  Figure 1.7

  shows the relationship between living organisms. Humans and other mammals (eukaryotes) appear on the right side of the tree. The base of the tree represents the ancestor of all living organisms.

  Figure 1.8

  Epidemiologists study how diseases spread. The above map shows where humans contracted West Nile Virus between 2000 and 2006. It is believed the virus entered the United States in New York City in 1999. Notice how rapidly the virus spread across the U.S.

  Figure 1.9

  Alexander von Humboldt mapped the distribution of plants across landscapes and recorded a variety of physical conditions such as pressure and temperature. Today, biogeographers study the diversity and distribution of organisms across Earth.

  Scientific Theories

  Science theories are produced through repeated studies, usually performed and confirmed by many individuals. Scientific theories are well established and tested explanations of observations. These theories produce a body of knowledge about the physical world that is collected and tested through the scientific method (discussed in the Scientific Method lesson).

  The word “theory” has a very different meaning in daily life than it does in science. When someone at school says, “I have a theory,” they sometimes just mean a hunch or a guess. This everyday meaning for “theory” can confuse people when well-tested and widely accepted scientific theories are discussed by nonscientists. For example, the theory of evolution is a well-established scientific theory that some people incorrectly say is just a hunch.

  A scientific theory is based on evidence and testing that supports the explanation. Scientific theories are so well studied and tested that it is extremely unlikely that new data will discredit them. The idea that matter is made up of atoms, evolution, and gravity are all scientific theories about how the world works that scientists accept as fundamental principles of basic science. However, any theory may be altered or revised to make it consistent with new evidence.

  Two Important Life Science Theories

  In the many life sciences, there are possibly hundreds or thousands of theories. Yet there are at least two fundamental theories, which provide a foundation for modern biology. They are:

  The Cell Theory

  The Theory of Evolution

  The Cell Theory

  The Cell Theory states that:

  All organisms are composed of cells (Figure below).

  Cells are the basic units of structure and function in an organism.

  Cells only come from preexisting cells; life comes from life.

  Figure 1.10

  The two types of cells, eukaryotic (left) and prokaryotic (right).

  The development of the microscope in the mid 1600s made it possible to come up with this theory (Figure below).

  Figure 1.11

  A mouse cell viewed through a microscope.

  The Theory of Evolution

  In biology, evolution is the process of change in the inherited traits of a population of organisms over time. Natural selection is the process where organisms that are better suited to the environment are more likely to survive and reproduce than others that are less suited to the environment. This theory basically states that better suited organisms live longer and have an easier time reproducing, passing on their traits that made them better suited to their environment. The theory of evolution by natural selection is often called the “great unifier” of biology, because it applies to every field of biology. It also explains the tremendous diversity and distribution of organisms across Earth. All living organisms (Figure below is a sampling) on Earth are descended from common ancestors.

  Figure 1.12

  Evolution explains the millions of varieties of organisms on Earth.

  Lesson Summary

  Science is a way of understanding (knowing) about the physical world that is based on evidence, reasoning, and testing predictions.

  A body of knowledge that has been thoroughly tested can still undergo further testing, and revisions as new evidence and questioning are raised.

  Science differs from other ways of knowing, because it is entirely based on observable evidence and its explanations are constantly questioned and tested.

  Science produces theories and general knowledge that allow us to better understand the world and to apply this knowledge to solve problems.

  Review Questions

  How is modern science different from other ways of knowing?

  Explain why science cannot be used to examine whether someone is good or bad?

  How is the scientific meaning of the word “the
ory” different from its use in day-to-day conversation?

  What do all fields of life science have in common?

  What are the three characteristics of evidence?

  What is the goal of science?

  What would you study if you were a biogeographer?

  Further Reading / Supplemental Links

  Moore, John, A., Science as a Way of Knowing: The Foundations of Modern Biology. Harvard University Press, 1993.

  Trefil, James, The Nature of Science, An A-Z Guide to the Laws and Principles Guiding the Universe. Houghton Mifflin, Boston, 2003.

  Darwin, Charles, Origin of the Species. Random House 1988.

  Cromer, Alan, Uncommon Sense: The Heretical Nature of Science, Oxford University Press. 1993.

  The Nature of Science the Prentice Hall Science Series 1993.

  American Association for the Advancement of Science. Science for All Americans. 1993.

  Johnson, Rebecca, Genetics (Great Ideas of Science), Twenty-First Century Books, 2006.

  Hedrick, Philip, W., Genetics of Populations (Biological Science (Jones and Bartlett)) Jones and Brothers Publishers, 2005.

  Charles Darwin: And the Evolution Revolution (Oxford Portraits in Science) by Rebecca Stefoff. Oxford Press. New York, 1996.

  Fleisher, Paul, Evolution (Great Ideas of Science). TwentyFirst Century Books, 2006..