Basic Science

 What is Science?

How does the Science work?

    Where do the fleas on your dog come from? Have you ever tried to figure out how to get rid of them? Why do some trees lose their leaves in the fall and others in spring? If you have questions about the world in which you live, you think like a scientist. Scientists observe what goes on around them. They ask questions about their observations and may try to find answers to their questions by using tests called experiments.

    Life scientists study living things. In this textbook, you'll be exposed to many branches of science as they touch on life science. For instance, you'll learn some basic chemistry, which is the study of the matter of which things are made. In the study of physics, you will learn that matter and energy are related. Earth science, the study of planet Earth, and life science use both chemistry and physics. 

   With millions of different kinds of organisms on Earth, it would be difficult to study every one. Many life scientists work with only one group of living organisms. Some life scientists are botanists who study plants. Others are zoologists who work with animals. More and more, scientists are seeing that none of these organisms exists alone. Ecologists are scientists who study how living things interact with each other and their environment on Earth. Genetics explains how traits of organisms are passed from generation to generation. 

What is the nature of science?

 Biology is a fascinating and important subject because it dramatically affects our daily lives and our futures. Many biologists are working on problems that critically affect our lives, such as the world's rapidly expanding population and diseases like cancer and AIDS. The knowledge these biologists gain will be fundamental to our ability to manage the world's resources in a suitable manner, to prevent or cure diseases, and to improve the quality of our lives and those of our children and grandchildren.

 Biology is one of the most successful of the "natural sciences," those devoted to explaining what our world is like. To understand biology, you must first understand the nature of science. Because the basic tool a scientist uses is thought, to understand the nature of science, it is useful to focus for a moment on how scientists think. They reason in two ways: deductively and inductively.

Deductive Reasoning 

Deductive reasoning applies general principles to predict specific results. The logic flows from the general to the specific. Over 2200 years ago, the Greek Eratosthenes used Euclidean geometry and deductive reasoning to accurately estimate the circumference of the earth. This sort of analysis of specific cases using general principles is an example of deductive reasoning. It is the reasoning of mathematics and philosophy and is used to test the validity of general ideas in all branches of knowledge. A biologist uses deductive reasoning to infer the species of a specimen from its characteristics.

Inductive Reasoning

In inductive reasoning, the logic flows in the opposite direction, from the specific to the general. Inductive reasoning uses specific observations to construct general scientific principles. If cats possess hair, and dogs possess hair, and every other mammal you observe has hair, then you may infer that perhaps all mammals have hair. Inductive reasoning leads to generalizations that can then be tested. Webster's Dictionary defines science as systematized knowledge derived from observation and experiment carried on to determine the principles underlying what is being studied. In other words, a scientist determines principles from observations, discovering general principles by carefully examining specific cases. Inductive reasoning first became important to science in the 1600s in Europe, when Francis Bacon, Isaac Newton, and others began to use the results of particular experiments to infer general principles about how the world operates. If you release an apple from your hand, what happens? The apple falls to the ground. From a host of simple, specific observations like this, New-ton inferred a general principle: All objects fall toward the center of the earth. What Newton did was construct a mental model of how the world works, a family of general principles consistent with what he could see and learn. Scientists do the same today. They use specific observations to build general models, and then test the models to see how well they work.

How Science Is Done?

How do scientists establish which general principles are true from among the many that might be true? They do this by systematically testing alternative proposals. If these proposals prove inconsistent with experimental observations, they are rejected as untrue. After making careful observations concerning a particular area of science, scientists construct a hypothesis, which is a suggested explanation that ac-counts for those observations. A hypothesis is a proposition that might be true. Those hypotheses that have not yet been disproved are retained. They are useful because they fit the known facts, but they are always subject to future rejection if, in the light of new information, they are found to be incorrect. .

Testing Hypotheses

We call the test of a hypothesis an experiment. Suppose that a room appears dark to you. To understand why it appears dark, you propose several hypotheses. The first might be, "There is no light in the room because the light switch is turned off." An alternative hypothesis might be, "There is no light in the room because the light bulb is burned out." And yet another alternative hypothesis might be, "I am going blind." To evaluate these hypotheses, you would conduct an experiment designed to eliminate one or more of the hypotheses. For example, you might test your hypotheses by reversing the position of the light switch. If you do so and the light does not come on, you have dis-proved the first hypothesis. Something other than the set-ting of the light switch must be the reason for the darkness. Note that a test such as this does not prove that any of the other hypotheses are true; it merely demonstrates that one of them is not. A successful experiment is one in which one or more of the alternative hypotheses is demonstrated to be inconsistent with the results and is thus rejected. As you proceed through this text, you will encounter many hypotheses that have withstood the test of experiment. Many will continue to do so; others will be revised as new observations are made by biologists. Biology, like all science, is in a constant state of change, with new ideas appearing and replacing old ones.

How are we measuring in science?

Think about how many things you use every day that measure or are measured. The thermostat keeps the air in your home at a certain temperature. Meters in your house measure water, electricity, and gas usage. Your food comes in pounds, ounces, and liters, and you step on a scale to check your weight.

Scientists use a system of measurement to make observations. Scientists around the world have agreed to use the International System of Units, or SI. SI is based on certain metric units. Using the same system gives scientists a common language. They can understand each others research and compare results.Because you are used to using the English system of pounds, ounces, and inches, a chart has been included on page  to help you convert these units to SI.

SI is based on units of ten. It is easy to use because calculations are made by multiplying or dividing by ten. Prefixes are used with units to change them to larger or smaller units. The SI unit of length is the meter. A metric ruler or a meter stick is used to measure length. If you look at the table, you see that 1000 meters equal one kilometer. Large distances are measured in kilometers.

Mass is the amount of matter in an object. Mass is measured with a balance. The SI unit of mass is the kilogram. Smaller masses are measured in grams and milligrams.

The amount of space occupied by an object is its volume. Units of volume are based on units of length. Volume is found by multiplying the length times the width times the height. The SI unit of volume is the cubic meter. Cubic meters are too large to be of any use in the laboratory. Because of this, the cubic centimeter (cm3) is used to measure volume. Liquid volumes are measured in liters (L). One liter has the same volume as 1000 cm3. Milliliters are used to measure smaller volumes.

The degree is the unit for measuring temperature. The kelvin scale is the SI standard for measuring temperature. Scientists also often use the Celsius scale. On the Celsius scale, water freezes at 0°C and boils at 100°C at sea level.

You will use these measurements to work in the laboratory this year. Working in the laboratory will help you understand the life science concepts in your textbook. You will observe and conduct experiments. Some of the observations you will make will be the same ones made by students and researchers for years and years. The important thing is that you will have seen these things yourself.

How to Establishing Controls?

Often we are interested in learning about processes that are influenced by many Factors, or variables. To evaluate alter-native hypotheses about one variable, all other variables must be kept constant. This is done by carrying out two experiments in parallel: In the first experiment, one variable is altered in a specific way to test a particular hypothesis; in the second experiment, called the control experiment, that variable is left unaltered. In all other respects the two experiments are identical, so any difference in the out-comes of the two experiments must result from the influence of the variable that was changed. Much of the challenge of experimental science lies in designing control experiments that isolate a particular variable from other factors that might influence a process.

Using Predictions

A successful scientific hypothesis needs to be not only valid but useful—it needs to tell you something you want to know. A hypothesis is most useful when it makes predictions, be-cause those predictions provide a way to test the validity of the hypothesis. If an experiment produces results inconsistent with the predictions, the hypothesis must be rejected. On the other hand, if the predictions are supported by experimental testing, the hypothesis is supported. The more experimentally supported predictions a hypothesis makes, the more valid the hypothesis is. For example, Einstein's hypothesis of relativity was at first provisionally accepted because no one could devise an experiment that invalidated it. The hypothesis made a dear prediction: that the sun would bend the path of light passing by it. When this prediction was tested in a total eclipse, the light from background stars was indeed bent. Because this result was unknown when the hypothesis was being formulated, it provided strong support for the hypothesis, which was then accepted with more confidence.

Developing Theories

Scientists use the word theory in two main ways. A "theory" is a proposed explanation for some natural phenomenon, often based on some general principle. Thus we speak of the principle first proposed by Newton as the "theory of gravity." Such theories often bring together concepts that were previously thought to be unrelated, and offer unified explanations of different phenomena. Newton's theory of gravity provided a single explanation for objects falling to the ground and the orbits of planets around the sun. "Theory" is also used to mean the body of interconnected concepts, supported by scientific reasoning and experimental evidence, that explains the facts in some area of study. Such a theory provides an indispensable framework for organizing a body of knowledge. For example, quantum theory in physics brings together a set of ideas about the nature of the universe, explains experimental facts, and serves as a guide to further questions and experiments. To a scientist, theories are the solid ground of science, that of which we are most certain. In contrast, to the general public, "theory" implies just the opposite—a lack of knowledge, or a guess. Not surprisingly, this difference often results in confusion. In this text, theory will always be used in its scientific sense, in reference to an accepted general principle or body of knowledge. To suggest, as many critics outside of science do, that evolution is "just a theory" is misleading. The hypothesis that evolution has occurred is an accepted scientific fact; it is supported by overwhelming evidence. Modern evolutionary theory is a complex body of ideas whose importance spreads far beyond explaining evolution; its ramifications permeate all areas of biology, and it provides the conceptual framework that unifies biology as a science.

Research and the Scientific Method

It used to be fashionable to speak of the "scientific method" as consisting of an orderly sequence of logical, either/or steps. Each step would reject one of two mutually incompatible alternatives, as if trial-and-error testing would inevitably lead a researcher through the maze of uncertainty that always impedes scientific progress. If this were indeed so, a computer would make a good scientist. But science is not done this way. As the British philosopher Karl Popper has pointed out, successful scientists without exception design their experiments with a pretty fair idea of how the results are going to come out. They have what Popper calls an "imaginative preconception" of what the truth might be. A hypothesis that a successful scientist tests is not just any hypothesis; rather, it is an educated guess or a hunch, in which the scientist integrates all that he or she knows and allows his or her imagination full play, in an attempt to get a sense of what might be true (see Box: How Biologists Do Their Work). It is because insight and imagination play such a large role in scientific progress that some scientists are so much better at science than others, just as Beethoven and Mozart stand out among most other composers.

 Some scientists perform what is called basic research, which is intended to extend the boundaries of what we know. These individuals typically work at universities, and their research is usually financially supported by their institutions and by external sources, such as the government, industry, and private foundations. Basic research is as diverse as its name implies. Some basic scientists at-tempt to find out how certain cells take up specific chemicals, while others count the number of dents in tiger teeth. The information generated by basic research con-tributes to the growing body of scientific knowledge, and it provides the scientific foundation utilized by applied research. Scientists who conduct applied research are often employed in some kind of industry. Their work may    involve the manufacture of food additives, the creation of new drugs, or the testing of environmental quality.

After developing a hypothesis and performing a series of experiments, a scientist writes a paper carefully describing the experiment and its results. He or she then submits the paper for publication in "a scientific journal, but before it is published, it must be reviewed and accepted by other scientists who are familiar with that particular field of research. This process of careful evaluation, called peer review, lies at the heart of modern science, fostering careful work, precise description, and thoughtful analysis. When an important discovery is announced in a paper, other scientists attempt to reproduce the result, providing a check on accuracy and honesty. Non reproducible results are not taken seriously for long.

The explosive growth in scientific research during the second half of the twentieth century is reflected in the enormous number of scientific journals now in existence. Although some, such as Science and Nature, are devoted to a wide range of scientific disciplines, most are extremely specialized: Cell Motility and the Cytoskeleton, Glycoconju-gate Journal, Mutation Research, and Synapse are just a few examples.

The scientific process involves rejecting hypotheses that are inconsistent with experimental results or observations. Hypotheses that are consistent with available data are conditionally accepted. The formulation of a hypothesis often involves creative insight.

what you need to know  about neurogenesis

Neurogenesis

We've all heard the warnings: If you (fill in the blank) you'll kill brain cells. And because scientists believed until very recently that you were born with all the brain cells you'd ever have, that was a fairly dire warning. You broke it, and you were stuck with the results.

 Recently we've been able to relax a bit, because we know that our brain makes new cells in at least two sections: the detente Cyrus of the hippocampus, a structure involved in learning and memory, and the olefactory bulbs. And it may in fact create new neurons elsewhere in the brain; we don't know for certain yet.

 Most of this research has been done on animals, but some human studies have confirmed the finding. Studies were done on terminal cancer patients who generously agreed to be injected with a marker for new cell production and to offer their brains for study after their death. The autopsies showed that even in the face of aging and death, their brains continued to produce new neurons to the very end. Chemotherapy could give us an idea of what happens when we don't make new neurons. Chemotherapy impairs the cell division needed for making new cells, and people who have had chemotherapy treatment for cancer and some other serious diseases often complain about a syndrome sometimes referred to as chemobrain. They have trouble with the kinds of learning and remembering that everyone finds challenging, such as juggling multiple projects while trying to process new information. 

Because having a ready supply of new neurons on tap could help to keep your brain intellectually limber, scientists are looking for ways to exploit this to prevent or treat disorders that bring about cognitive decline. Meanwhile, they've found that these new brain cells disappear if you don't use them.

what to need to know about neuroplasticity

neuroplasticity 

 Scientists have long known that the brain can change itself. In fact, your brain is probably changing every microsecond in response to experiences, both external and internal. Those changes come mainly from the growth of new connections and networks among neurons, particularly among newborn neurons.

 We've known that different kinds of experiences lead to changes in brain structure, with more activity in the networks used most. In musicians, for example, the parts of the brain ddclicated to playing their instruments are disproportionately larger than in nonmusicians or in musicians who play a different instrument. A decade-old study of London taxi drivers skilled at navigation in the city center showed the same effect: they had larger hippocampi than nondrivers, reflecting the huge amount of data they needed to have at hand. Moreover, the longer they drove complicated routes around the city, the larger their hippocampi grew.

 Also, brains apparently riddled with blank areas or plaque and other signs of Alzheimer's disease have come from people functioning very well into late old age. Indeed, some brains lacking a hemisphere—the entire half of a brain—can function quite well.

 We also know the brain can sometimes repair itself after devastating injury, bypassing dead areas to create new connections. ABC news correspondent Bob Woodruff, critically injured by a roadside bomb in 2006 while covering the war in Iraq, suffered a brain injury so severe that part of his skull was permanently removed, and he was kept in a medically induced coma for more than a month. Few believed he would walk again, let alone work as a reporter. After more than a year of intensive therapy, which included relearning speech to

what is important or reasons to take care of human brain

 Centenarians—individuals one hundred years or older—are the fastest growing age group in the United States, and experts predict there may be as many as 1 million by 2050.

 If you're sixty years old (or younger) today, you could be in that group. And if you want your mind to be there along with you, take good care of your brain.

 You'll have plenty of company near your age: people aged eighty and older are the fastest-growing portion of the total population in many countries. By 2040, the number of people sixty-five or older worldwide will hit 1.3 billion, according to the National Institute on Aging, which announced the figures. And within ten years, there will be more people aged sixty-five and older than children under five in the world for the first time in human history.

 The most rapid increase will be in developing countries. By 2040, they will be home to more than 1 billion people aged sixty-five and over-76 percent of the projected world total. If you reach one hundred years, you are sure to live in interesting times, an old blessing (or curse) of the Chinese (who, incidentally, will have the world's largest population of elders by 2040). This global aging will change the social and economic nature of the planet and present some difficult challenges. Interesting times, indeed.

overcome aphasia, he made a hard-hitting documentary about the plight of injured soldiers and the deficits in government care. And then he went back to work as a reporter—in Iraq. Certainly Woodruff benefited from the kind of very expensive and intense treatment not available to all of us. Nevertheless, his recovery shows how remarkably able the brain is, especially because his was not a young brain: he was forty-four at the time of his injury. What we did not know for certain until recently is that what you think and feel also physically change your brain, such as intellectual

challenges, deliberate brain training, anxiety, and joy. So it seems there is a biological basis to mind training: you can learn skills aimed at changing your brain just as you learn repeated activities to change your body. Meditation is a brain-changing example. Studies show that regular practice of meditation results in physical as well as mental and emotional changes. In long-time practitioners of meditation, the two hemispheres become more balanced, the trigger-happy amygdala shows less reaction to emotional sounds, and the many brain regions involved in focused attention show greater activity (see "Boosting Your Brain with Meditation,").

How to changes in human brain 

Epigenetics 

Scientists are finding one of the ways your brain changes itself is by actually changing your genes—or more correctly, by the acting out (or not) of certain genes—in the process of epigenesis. We know that your genome is the total deoxyribonucleic acid (DNA) that you inherit from your ancestors and contains the instructions for making your unique body and brain. Another layer of information, called the epigenome, is stored in the proteins and chemicals that surround and stick to the DNA. It's a kind of chemical switch that determines which genes are activated (or not): it tells your genes what to do and where and when.

Researchers have discovered that the epigenome can be affected by many things, from aging and diet to environmental toxins to even what you think and feel. This means that even your experiences can literally change your mind by chemically coating the DNA that con

trols a function. The coating doesn't alter the underlying genetic code; rather, it alters specific gene expression, shutting down or revving up the production of proteins that affect your mental state.

 Epigenetics helps explain the gap between nature and nurture that has long puzzled scientists: why some illnesses and traits pop up in one but not both identical twins who have the same DNA, or why these traits skip a generation. It also helps explain neuroplasticity.

One researcher describes DNA as a computer hard disk, with certain areas that are password protected and others that are open. Epigenetics is the programming that accesses that material, writes Jolt Walter of Saarland, Germany, on the Web site Epigenome. 

Epigenetics can profoundly affect your health and, it seems, your happiness, changing not only your vulnerability to some diseases such as cancer but also your mental health. Scientists have found, for example, that a mother rat's nurturing, through licking and loving behavior that boosts the expression of a gene that eases anxiety and stress, bolsters emotional resilience in her newborn pups. They've also found that distressing events can turn off the expression of genes for brain cell growth protein and thereby trigger depression, and that epigenetic changes may also underlie the pathology of schizophrenia, suicide, depression, and drug addiction. 

The acting-out process of changeable genes—gene expression—is quite complicated and a new area of intense research. Just recently biologists have found that epigenetic changes may be heritable—passed on to your descendants—just as your DNA is. They have also found that altering gene expression with drugs or environments that provide more intellectual stimulation can improve learning and memory in cognitively impaired animals. Future therapies for memory disorders in humans might work in a similar way. It's a promising area with much to be learned. In 2008, the National Institutes of Health invested $190 million in the five-year Roadmap Epigenomics Program to pursue some of these promising fields of research.

How to Choose a Physician

When choosing a physician, plan to obtain answers to the following questions during your initial visit:

 • Obtain a description of the physician's medical back-ground, such as education, residencies, and specialty areas.

 • How does the physician keep up with new developments in the medical profession? Does the physician attend seminars and conferences, take courses, read medical journals, write articles, participate in professional organizations, or teach at a medical school? 

• What are the normal office hours? What should be done if help is needed outside of normal office hours?

 • What is included in a comprehensive physical examination? 

• How does the physician feel about second and third opinions? • Which hospitals is the physician affiliated with in your area?

 • With which specialists is the physician associated?

 • What is the physician's fee schedule? 

Ask yourself the following questions after your visit:

 • Was I comfortable with the physician's age, gender, race, and national origin?

 • Was I comfortable with the physician's demeanor? 

Did I find communication with the physician to be understandable and reassuring? Were all my questions answered? 

• Did the physician seem interested in having me as a patient?

 • Are the physician's training and practice specialty in an area most closely associated with my present needs and concerns?

 • Does the physician have staff privileges at a hospital of my preference?

 • Does the physician's fee-for-service policy in any way exclude or limit my ability to receive necessary services? 

• Did the physician take a complete medical history as a part of my initial visit? Was prevention, health pro-motion, or wellness addressed by the physician at any point during my visit?

 • Did I at any point during my visit sense that the physician was unusually reluctant or anxious to try new medical procedures or medications?

 • When the physician is unavailable, are any col-leagues on call for 24 hours? Did I feel that telephone calls from me would be welcomed and responded to in a reasonable period?

 If you have answered yes to most of these questions, you have found a physician with whom you should feel comfortable. If you have been using the services of a particular physician but are becoming dissatisfied, how could you resolve this dissatisfaction?  

 Do you know the Structure of DNA?

The structure of DNA was discovered in 1953 by James Watson and Francis Crick. It is considered the most significant biological breakthrough of the twentieth century, since it explained heredity in terms of molecular structure and was the first step toward genetic engineering, which has accomplished amazing feats in the past few decades. James Watson, only twenty-four years old at the time, was an American biologist who once dreamed of be-coming a bird ecologist. Francis Crick, thirty-six years old at the time, was a British physicist who knew little of genetics. This unusual research team just happened to share an office at the University of Cambridge, England. What began as a series of casual discussions led to an intense effort to figure out the structure of DNA. As with all research, considerable work by other scientists guided Wat-son and Crick to the correct hypothesis. By 1953, the following observations had been made:

 • Genetic material makes copies of itself.

 • DNA is genetic material (at least in bacteria).

 • DNA is a long molecule twisted into a helix.

 • DNA contains strands of sugar and phosphate to which nitrogenous bases are attached.

 Of the four bases found in a DNA molecule, the amount of adenine always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine.

 Watson and Crick used these observations to develop alternative hypotheses about the arrangement of sugar, phosphate, and bases within the DNA molecule. They built physical models of the molecule described by each hypothesis. One model, for example, had two sugar-phosphate strands and another had three; one model had the bases projecting out-ward and another had them projecting inward.

 The model that best fit all existing observations was a double helix with paired bases on the inside. The bases join to each other in a specific manner: adenine bonds with thymine and guanine bonds with cytosine. In fact, the model fit everything that was known about the chemistry of DNA. The key to the Watson-Crick model is the arrangement of bases.

The sequence of bases along one strand of the molecule could hold a vast amount of information. And the paired bases between the two strands provided a mechanism for self-replication. The weak bonds (hydrogen bonds) between the bases could easily break and the molecule would come apart lengthwise. Then, if adenine pairs only with thymine and guanine

Subsequent experiments have shown that DNA duplicates itself in precisely this manner: the two strands separate and each strand serves as a template for build

ing another strand. Forty years later, Crick made the following remark about the discovery: "One has to reflect on. really, what a remarkable thing it is in the history at least of life on earth, because nucleic acids, certainly RNA and DNA, almost surely existed on the earth for billions of years. It is the basis of all the life forms we see, but really, it's only been in the last half-century—which is a blink, really, in time—that any form of life on earth has become aware of the structure of DNA."