And this copying of the molecule before anything is The building blocks of matter, called atoms, lie at the base of life s organizational structure see Chapter 2 for more about them. Atoms come together to form molecules, which are entities consisting of a de ned number of atoms that exist in a de ned spatial relationship to one another.
A molecule of water is one atom of oxygen bonded to two atoms of hydrogen, with these atoms arranged in a precise way. Molecules in turn form organelles, meaning tiny organs, in a cell. Each of your cells has, for example, a structure called a nucleus that contains the cell s primary complement of DNA. Such an organelle is not just a collection of molecules that exist close to one another. It is a highly organized structure, as you can tell just from looking at the rendering of it in the sea lion in Figure 1.
Atoms, molecules, and organelles are all component parts of life, but they are not themselves living things. At the next step up the organizational chain, however, we reach the entities that are living. These are cells, the fundamental units of life; the simplest, smallest entities that carry out all of life s basic processes. Indeed, if we ask where life exists outside cells, the answer most experts would give is: nowhere at all.
Every product of life the material that makes up our bones, the wood that helps make up a tree comes from cells, and every process that enables life is initiated by cells. Large organisms such as the sea lion in Figure 1. The sea lion has, for example, collections of the nerve cells called neurons, 1. Each collection of these cells is referred to as neural tissue. Several kinds of tissues can then come together to form a functioning unit known as an organ.
The sea lion s brain, for example, is made up not only of neurons but of cells called glia that help support neurons. Several organs and related tissues then can be integrated into an organ system. The sea lion s brain, its spinal cord, and all the nerves that extend from these organs constitute the sea lion s nervous system. An assemblage of cells, tissues, organs, and organ systems can then form a multicelled organism such as the sea lion. However, back down at the cell level, a one-celled bacterium is also an organism; it s just not one that has organs, tissues, and so forth.
From this point out, life s levels of organization all involve many organisms living together. Members of a single type of living thing a species , living together in a de ned area, make up what is known as a population. When you look at all the kinds of living things in a given area, you are looking at a community. When you consider the members of a community and the non-living elements with which they interact such as climate and water , the result is an ecosystem. Finally, all the communities of Earth and the physical environment with which they interact make up the biosphere.
Life s Spectacular Diversity Life at the level of populations, communities, and ecosystems is tremendously complex for the simple reason that life at these levels is tremendously diverse. We can get an intuitive sense of this diversity by just thinking about the stunning forms that life comes in: whales, bats, trees, toadstools, algae. But life s diversity also exists in forms that are less visible to us.
A single gram of fertile midwestern soil an amount of soil community giant kelp forest Special Qualities of Biology ecosystem Southern California coast about the size of a quarter of a teaspoon is likely to contain 10, different species of bacteria, along with an assortment of roundworms, fungi, insects, and perhaps plant root fragments.
When we look at the living world as a whole, we nd that the lowest estimate for the total number of species in it is about 4 million, while higher-end estimates come in at 10 to 15 million, and the highest of them all is million. We really have no idea which of these estimates best approximates the truth, however.
In all the time that scientists have been looking at the living world, they simply have been unable to catalogue its vast diversity. In the work of such Greeks as Hippocrates and Galen, we can nd the origins of modern medical science. In the work of Aristotle and others, we can nd the origins of natural history, which led to what we think of today as mainstream biology and the larger category of the life sciences: a set of disciplines that focus on varying aspects of the living world.
Apart from biology, the life sciences include such areas of study as veterinary medicine and forestry. Despite its ancient origins, biology is, in a sense, a much younger science than, say, physics, which is one of the physical sciences, meaning the natural sciences not concerned with life. Western Europe s revolution in the physical sciences probably can be dated from the sixteenth century, when Nicholas Copernicus published his work On the Revolution of Heavenly Spheres, which demonstrated that Earth moves around the sun.
Meanwhile, biology did not come into its own as a science until the nineteenth century. On average, three to ve years elapsed between the date patients were diagnosed with CML and the date they died from it. Today, however, 85 to 90 percent of CML patients are alive ve years after diagnosis, and it seems likely that the vast majority of these patients will be alive a great deal longer.
The reason their future looks bright is that CML has been transformed. Whereas once it was a deadly disease, it now has taken on the qualities of a chronic, manageable disorder a condition that can be controlled in the manner of, say, diabetes or asthma. What has made the difference with CML is a single drug, called Gleevec, that was approved for medical use by the U. Food and Drug Administration in But for most of the 5, Americans diagnosed with CML each year, it has meant the difference between life and death.
For a single drug to have made this kind of difference in the treatment of a particular cancer is almost without precedent in cancer therapy. But Gleevec is remarkable in several other respects as well. To an unusual degree, it resulted from the vision and persistence of a single researcher, Brian Druker, who since has been at the Oregon Health and Science University in Portland, Oregon Figure 1.
Apart from this, Gleevec is now seen as the drug that pointed the way toward the future in can- cer research, in that it was the rst drug to target what might be called the circuitry of a particular cancer the chemical pathway by which a given form of cancer gets started.
Despite all this, however, there are elements of Gleevec s history that could be found in connection with any cancer drug. In some ways, its development is a textbook example of how science and big business work together in tackling the daunting challenge of cancer. Gleevec s story began in the s, when Druker, then fresh out of medical school at the University of California, San Diego, was carrying out a type of research that underlies the development of any cancer treatment.
This is so-called basic research, which is aimed at coming to a better understanding of either cancer in general or of a particular cancer how does it get started, how does it change over time, what might its weak points be? Such research can be funded by private foundations, but in the United States today, the largest single funder of this research by far is the federal government speci cally a branch of the federal government known as the National Institutes of Health NIH , which is made up of 27 separate institutes and centers.
This large federal investment in cancer research, however, does not extend to developing the cancer drugs that end up being administered by physicians.
Gleevec was a product of an intertwining of both this applied, pharmaceutical research and basic, NIH-funded research. In the s, Druker was carrying out basic research on a family of proteins, called the tyrosine kinases, that promote the process by which human cells divide one cell becoming two, two becoming four, and so on.
At the same time, the Swiss pharmaceutical giant Ciba-Geigy which later became Novartis was likewise working with tyrosine kinases and came to Druker s lab, beginning in , to seek out expertise on the effectiveness of a set of drugs that were aimed at inhibiting the activity of tyrosine kinases.
The idea was that drugs that could disrupt the activity of these kinases could be used to stop the uncontrolled division of cells that is a hallmark of all forms of cancer. The challenge was to nd a compound that could carry out this disabling task. When, in , Druker began to search for such a compound, he contacted Ciba-Geigy biochemist Nicholas Lydon, who sent him several tyrosine kinase inhibitors developed in his lab, one of which went on to show promise in laboratory that serve as the make-or-break test for all human medicines: clinical trials.
No drug can be prescribed for use in the United States without having rst been approved by the U. Food and Drug Administration. And to gain FDA approval, every drug must be put through a series of rigorous tests on human beings that demonstrate, rst, that the drug is safe and, second, that it has a positive effect on the condition it is intended to combat. The gold standard for demonstrating both things to the FDA is the Gleevec is now seen as the drug that pointed the way toward the future in cancer research.
This was the compound that became Gleevec. The problem was that Ciba-Geigy s successor, Novartis, had little interest in proceeding with human tests of this substance that is, with tests of it in CML patients. One of the problems with such testing was that no one had ever given a tyrosine kinase inhibitor to a human being before, and the assumption of many experts was that doing so could be dangerous.
Apart from this, however, proceeding with the development of Gleevec seemed to make little sense to Novartis as a business proposition. The 5, Americans who are diagnosed with CML each year represent a small number of cancer patients compared to, say, the 46, Americans who are diagnosed with kidney cancer or the , who are diagnosed with lung cancer.
Thus, even if Gleevec worked which was far from certain following the lab tests of it demand for it was bound to be small, while the costs of developing it were bound to be large. As a simple matter of economics, then, Novartis had little incentive to nd out whether it would be effective as a cancer treatment.
Eventually, however, Druker convinced the company to see it through the expensive set of evaluations clinical trial, which is a set of tests that typically operate in three stages: a Phase I trial that seeks to demonstrate nothing more than the safety of the drug, as measured by its effect among a few dozen patients; a Phase II trial that expands the patient-base to several hundred volunteers and that is looking for both safety and effectiveness; and a Phase III trial that often enrolls thousands of patients at dozens of clinical settings that may be located around the world.
These trials are models of the scienti c method in that they must adhere to two watchwords: they must be controlled and they must be randomized.
They are controlled in that the drug must demonstrate its effectiveness compared to another therapy generally the therapy that is standard for the disease in question at the time. And they are randomized in that patients will randomly be assigned to get either the new drug or the standard therapy. Novartis began its Phase I trial of Gleevec in June with a small group Special Qualities of Biology of CML patients who had not responded to the standard therapy of the time, which was a form of the drug interferon.
This trial, which went on for a little less than a year, was intended only to measure the safety of Gleevec, but a strange thing happened during this test: Gleevec demonstrated an astounding effectiveness among the patients. White blood cell counts returned to normal in 53 of 54 patients who received high doses of Gleevec a 98 percent response rate in a type of trial that would have been counted as a success had it achieved a 10 percent response rate.
Three years elapsed from the time a volunteer first took a dose of Gleevec to the time it was approved for use in CML patients. By way of comparison, the FDA normally takes between five and eight years to approve a drug. Today, Gleevec is used not just for CML, but for nine other forms of cancer as well; as a result, it is now administered to some , cancer patients worldwide.
Druker receives no income from any sales of Gleevec, as he began his work with it only after it had been patented as a potential medicine. His achievements in connection with it have, however, been widely recognized by both cancer patients and cancer researchers. The two shared the award with Charles Sawyers of Memorial SloanKettering Cancer Center in New York, who was instrumental in developing compounds that are effective in treating CML patients whose cancers have become resistant to Gleevec.
Beginning in about the s, however, biologists began to formulate biological theories as that term was de ned earlier. They began to postulate that all life exists within cells, that life comes only from life, that life is passed on through small packets of information that we now call genes, and so on.
To put this another way, biologists in the nineteenth century began describing the rules of the living world, whereas before they were largely describing forms in the living world. This change moved biology closer to the same scienti c footing as physics, but biology was then, and remains now, a very different kind of science from any of the physical sciences, with physics a clear case in point.
One reason for this difference is that the component parts of physics are uniform and far fewer than is the case in biology. Physics deals with only 92 stable elements, such as hydrogen and gold, and to a rst approximation, if you ve seen one electron, you ve seen them all. Meanwhile, in biology, if you ve seen one species, you ve seen just that one species. Each species is at least marginally different from another, and many are greatly dissimilar. Moreover, each species has all the organizational levels of elements in physics and more.
They not only have electrons and atoms, but organelles, cells, tissues, and so on. Biology is concerned with the rules that govern all species, and a A peacock displaying his plumage Figure 1. However, when cancer researchers are looking for the principles that underlie cell division, they are likely to be looking at only one of two main kinds of cells; when ecologists are looking at what causes dry grassland to turn into desert, their ndings are likely to have little relevance to the rain forest.
Put simply, the living world is tremendously diverse compared to the non-living world, and such diversity means that biology is concerned less with universal rules than is the case in the physical sciences. Evolution: Biology s Chief Unifying Principle Almost all biologists would agree that the most important thread that runs through biology is evolution: the gradual modi cation of populations of living things over time, with this modi cation sometimes resulting in the development of new species.
Evolution is central to biology because every living thing has been shaped by it. There are no known exceptions to this universal. Given this, the explanatory power of evolution is immense. Why do peacocks have their nery, or frogs their coloration, or trees their height Figure 1.
All these things stand as wonders of nature s diversity, but with knowledge of evolution they are wonders of diversity that make sense. For example, why do so many unrelated stinging insects look alike?
Evolutionary principles suggest that they evolved to look alike because of the general protection this provides from predators. Think of yourself for a moment as a bee predator. Having once gotten stung, would you annoy any roundish insect that had a black-and-yellow striped coloration?
You probably learned your lesson about this in connection with one species, but many species of insects are now protected from you simply by virtue of the coloration they share Figure 1. Thus, there were reproductive bene ts to individual insects that, through genetic chance, happened to get a slightly more striped coloration: They left more offspring because they were bothered less by predators.
Over time, entire populations moved in this direction. They evolved, in other words. The means by which living things can evolve is a topic this book takes up beginning in Chapter For now, just keep in mind that a consideration of evolution is never far from most biological observations.
So strong is evolution s explanatory power that in uncovering something new about, say, a sequence of DNA or the life cycle of a given organism, one of the rst things a biologist will ask is: What evolutionary advantage can this have provided? On to Chemistry How do you get a handle on something as diverse and complex as life? One way is to start small, with life s building blocks, and then see how these units come together to make up complete organisms. We ll be taking this approach over the next several chapters starting small and working our way up, you might say.
We ll actually be starting very small in this tour, with the building blocks called atoms. For us, the central question concerning these tiny entities will be: How do they come together to make up life s larger molecules? As you ll see, the short answer to this question is: They obey the laws of chemistry.
Arrange the following levels of organization in living things, going from least inclusive to most inclusive: cell, community, molecule, organ, ecosystem, organism. Science is also a way of learning: a process of coming to understand the natural world through observation and experimentation.
A theory is a general set of principles, supported by evidence, that explains some aspect of nature. Then comes a hypothesis a tentative, testable explanation that most often will be tested through a series of experiments. Life is de ned by a group of characteristics: Living things can assimilate energy, respond to their environment, maintain a relatively constant internal environment, and reproduce. In addition, they possess an inherited information base, encoded in DNA, that allows them to function; they are composed of one or more cells; they are evolved from other living things; and they are highly organized compared to inanimate objects.
Evolution helps explain the forms and processes seen in living things. Which of the following statements best describes the nature of a scienti c hypothesis? A hypothesis is an idea that is widely accepted as a description of objective reality by a majority of scientists.
A hypothesis must stand alone and not be based on prior knowledge. A hypothesis is a tentative explanation that can be tested, usually through experimentation. A hypothesis must deal with an aspect of the natural world never dealt with before.
A hypothesis, when accepted, becomes a scienti c law. A theory, as de ned in scienti c discourse, is: a. Pasteur s experiments on spontaneous generation made correct use of a variable in that Pasteur: a.
Which of the following characteristics are true of all scienti c claims? Select all that apply. They are capable of negation through further scienti c inquiry. They can be negated by expert opinion. They are natural explanations for either natural or supernatural phenomena. Chapter 1 Review d. They stand or fall solely on the basis of evidence.
They are regarded as provisional, pending the addition of new evidence. Evolution is a central, unifying theme in biology because: a. Biologists generally de ne life in terms of a group of characteristics possessed by living things. Which of the following is not a characteristic of living things?
All living things possess an inherited information base, encoded in DNA, that allows them to function. All living things can respond to their environment. All living things can maintain a relatively constant internal environment. All living things evolved from other living things. All living things are composed of more than one cell. Brief Review Answers are in the back of the book. What is science? In what ways is science different from a belief system such as religious faith?
What is a controlled experiment? How did Louis Pasteur cast doubt on the idea of spontaneous generation? Describe the de ning features of life as we know it on Earth.
Living things are organized in a hierarchical manner. List all the levels of the biological hierarchy that you can. Applying Your Knowledge 1. Would you agree that it is valuable for a nation to have a citizenry that is reasonably well versed in science? Give reasons for your answer. Would you say this need has become especially urgent in the last two decades?
If so, why? Although science cannot investigate the supposed workings of the supernatural, the scienti c method can be used to investigate some claims that the supernatural has been at work.
Can an astrologer know something about you just by knowing the place and time of your birth? A scienti c test of this question, carried out in the s, involved providing a group of 30 top-level astrologers with 17 nothing but birth information for a group of people and then seeing whether the astrologers could predict anything about the personalities of these people as measured by a standard personality inventory.
The result was that the astrologers did no better than chance in trying to predict personality. Many of the standard tools of science were at work in this test of astrology for example, controls the test was the same for each astrologer and statistical analysis used to see whether the astrologers did better than chance. Using this test as a case in point, are all claims of supernatural effects open to scienti c investigation?
Can you think of other claims that could be investigated or any that could not? If you were sent on an interplanetary mission to investigate the presence of life on Mars, what would you look for?
Would you explore the land and the atmosphere? Imagine you discover an entity you suspect is a living being. Realizing that life elsewhere in the universe may not be organized by the same rules as on Earth, which of the features of life on Earth, if any, would you insist that the entity display before you would declare it living?
The qualities of water have shaped life. The degree to which substances are acidic or basic has strong effects on living things. Here, a red-eyed tree frog Agalychnis callidryas sits under a plant leaf during a rainstorm. To answer this question, in this chapter we will look at what the material world is made of.
Biology is our subject, but to fully understand it, you need to learn a little about what underlies biology. You need to learn a little about what biology is made of, in a sense. To do this, you need to understand some of the basics in another eld: chemistry. How is chemistry relevant to biology? Well, the average person probably is aware that living things are made up of individual units called cells, but beyond this bit of knowledge, reality fades and a kind of fantasy takes over.
In it, the cells that populate people, plants, or birds carry on their activities under the direction of their own low-level consciousness. A cell decides to move, it decides to divide, and so on. Not so. By the time our story is finished, many chapters from now, it will be clear that the cells that make up complex living things do what they do as the result of a chain of chemical reactions. Repulsion and bonding, latching on and re-forming, depositing and breaking down what makes people, plants, and birds function at this cellular level is chemistry.
Given this, the basic principles of chemistry are important to biology important enough that we ll spend most of this chapter reviewing them.
Once this is done, we ll touch on one of life s most important substances, water. Then we ll finish the chapter with a look at pH, a chemistry-related concept that has to do with how acidic or basic watery solutions are. Look around you. Do you see a table, light from a lamp, a patch of night or daytime sky?
Everything that exists can be viewed as falling into one of two categories: matter or energy. You will learn something about energy in this chapter, but we are most concerned here with matter and its transformations, which is the subject of chemistry. Matter can be de ned as anything that takes up space and has mass. This latter term is a measure of the quantity of matter in any given object. How much space does an object occupy how much volume, to put it another way and how dense is the matter within that space?
These are the things that de ne mass. For our purposes, we may think of mass as equivalent to weight, although physics makes a distinction between these two things. As we behold matter all around us, it is natural to ask, What is its nature? A child sees a grain of sand, pounds it with a rock, sees the smaller bits that result, and wonders: What is this stuff like at the end of these divisions?
Not surprisingly, adults also have wondered about this question for centuries. About 2, years ago, the Greek philosopher Plato accepted the notion that all matter is made up of four primary substances: earth, air, re, and water. A nearcontemporary of his, Democritus, believed that these substances were in turn made up of smaller units that were both invisible and indivisible they could not be broken down further.
He called these units atoms Figure 2. Well, let s give at least one cheer for Democritus because he had it partly right. Centuries of painstaking work between his time and ours has con rmed that matter is indeed composed of tiny pieces of matter, which we still call atoms, but these atoms are not indivisible, as Democritus thought.
Rather, they are themselves composed of constituent parts. A super cial account of all the parts scientists have discovered to date would go on for pages and still be incomplete.
Physicists are continually slamming together parts of atoms with ever-greater force in an effort to determine what else there may be at the heart of matter. This is what the machines called atom smashers do. The physicists who run them could be compared to people who, in trying to nd out what parts a watch has, throw it on the ground and record the way its 19 20 Chapter 2 Fundamental Building Blocks: Chemistry, Water, and pH electron proton organism sea lion organ brain cell neuron molecule water atom hydrogen Figure 2.
The atom selected here, from among a multitude that make up the sea lion, is a single hydrogen atom, composed of one proton and one electron.
This is interesting stuff, but it is purely the business of physics, with little relation to biology. We are not concerned here with what s at the very end of matter s divisions. We do care a good deal, however, about what s nearly at the end of them.
Protons, Neutrons, and Electrons For our purposes, there are three important constituent parts of an atom: protons, neutrons, and electrons. These three parts exist in a spatial arrangement that is always the same, regardless of what atom we re dealing with. Protons and neutrons are packed tightly together in a core the atom s nucleus , and electrons move around this core some distance away Figure 2.
The one variation on this theme is the substance hydrogen, the lightest of all the kinds of matter we will run into. Hydrogen has no neutrons but rather only one proton in its nucleus and one electron in motion around it. These three subatomic particles have mindbending sizes and proportions. As the chemist P. The model is not drawn to scale; if it were, the electrons would be perhaps a third of a mile away from the nuclei.
The model also is simpli ed, giving the appearance that electrons exist in track-like orbits around an atom s nucleus. In fact, electrons spend time in volumes of space that have several different shapes. Things are just as disorienting when we consider the size of an atom as a whole relative to the nucleus. The whole atom, with electrons at its edge, is , times bigger than the nucleus.
So, if you were to draw a model of an atom to scale and began by sketching a nucleus of, say, half an inch, you d have to draw some of its electrons more than three-quarters of a mile away.
Although the nucleus accounts for little of the space an atom takes up, it accounts for almost all of the mass an atom has. So negligible are electrons in this regard, in fact, that all of the mass or weight of an atom is considered to reside with the protons and neutrons of the nucleus. The components of atoms have another quality that interests us: electrical charge.
Protons are positively charged, and electrons are negatively charged. Neutrons as their name implies have no charge; they are electrically neutral. Because all these particles do not exist separately but combine to form an atom, as a whole the atom may be electrically neutral as well. The negative charge of the electrons balances out the positive charge of the protons.
Because in this state the number of protons an atom has is exactly equal to the number of electrons it has although we ll see a different, ionic state later in this chapter. In contrast, the number of neutrons an atom has can vary in relation to the other two particles. With this picture of atoms in mind, we can begin to answer the question that has been handed down to us through history: What is matter?
We certainly have a common sense answer to this question. Matter is any substance that exists in our everyday experience. For example, the iron that goes into cars is matter. But what is it that differentiates this iron from, say, gold? The answer is that an iron atom has 26 protons in its nucleus, while a gold atom has And the thing that defines each element is the number of protons it has in its nucleus.
A solid-gold bar, then, represents a huge collection of identical atoms, each of which has 79 protons in its nucleus Figure 2. In making gold jewelry, an artist may combine gold with another metal such as silver or copper to form an alloy that is stronger than pure gold, but the gold atoms are still present, all retaining their proton nuclei. Given what you ve just read about protons, neutrons, and electrons, you may wonder why gold or any other element cannot be reduced to any simpler set of component substances.
Aren t protons and neutrons components of atoms? Yes, but they are not component substances because they cannot exist by themselves as matter. Rather, protons and neutrons must combine with each other to make up atoms.
Assigning Numbers to the Elements In the same way that buildings can be de ned by a location and thus have a street number assigned to them, elements, which are de ned by protons in their nuclei, have an atomic number assigned to them.
Scientists have constructed the atomic numbering system so that it goes from the smallest number of 21 Figure 2. Each gold bar is made up of a vast collection of identical atoms those with 79 protons in their nuclei.
So, hydrogen, which has only one proton in its nucleus, has the atomic number 1. The next element, helium, has two protons, so it is assigned the atomic number 2. Continuing on this scale all the way through the elements found in nature, we end with uranium, which has an atomic number of You can see all of these elements laid out for you in a periodic table at the back of the book, in Appendix 2, on page AP3.
Given this view of the nature of matter, we are now in a position to answer the question posed at the beginning of the chapter: What is a handful of earth or anything else made of? The answer is: one or more elements. If you look at Figure 2. Figure 2. Recall that atoms also have neutrons in their nuclei; that these neutrons add weight to the atom; and that the number of neutrons can vary independently of the number of protons.
What this means is that, in thinking about an element in terms of its weight, we have to take neutrons into account. Furthermore, because the number of neutrons in an element s nucleus may vary, we can have various forms of elements, called isotopes. Most people have heard of one example of an isotope, whether or not they recognize it as such. The element carbon has six protons, giving it an atomic number of 6. In its most common form, it also has six neutrons.
However, a relatively small amount of carbon exists in a form that has eight neutrons. Well, the element is still carbon, and in this form the number of its protons and neutrons equals 14, so the isotope is carbon which is used in determining the age of objects ranging from pyramids to plants, as you can see in Finding the Iceman s Age in an Isotope on page Most elements have several isotopes.
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Inventory No: Biology: A Guide to the Natural World. This title is out of print. Availability This title is out of print. Accessible writing style acts as a helpful companion that guides non-majors students through the subject of biology by placing unfamiliar biology topics in context with everyday life.
The Process of Science essays present scientific research and discovery with contemporary and historical topics of interest to students. Strong Illustration Program guides students through structures and processes with clear three-dimensional detail; key information from the text is reinforced in the illustrations.
New to This Edition. New Streamlined Chapter Summaries distill the key points from the chapter for quick review in preparation for class or before taking a test. New chapter organization allows more flexibility for assigning full chapters to match course syllabi. Separate Chapters on Plants Ch. Separate Chapters on the Nervous System Ch. Combined Chapter 25 on Angiosperms has reduced the plant unit chapters from two to one. New Coverage of Health and Medical Topics, from the intertwining of science and big business in the development of cancer drugs, to new research that explores endorphin release as a possible motivation for the use of tanning beds, and new information concerning the H1N1 virus.
Updated coverage of key topics such as genetic regulation, cell reprogramming, embryonic stem cells, origin of life theories, global climate change, and environmental issues.
Streamlined approach to Animal Phyla now looks across the phyla in four subject areas: reproduction, egg fertilization and protection, organs and circulation, and skeletons and molting. New design creates a more visually appealing and accessible experience for students. Table of Contents 1.
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