Introduction (1/4)
The brilliant white sand dunes and sparse clumps of beach grass along the Florida seashore afford little cover for the beach mice that live there. However, a beach mouse's light, dappled fur acts as camouflage, allowing the mouse to blend into its surroun
Introduction (2/4)
An organism's adaptations to its environment, such as camouflage that helps protect it from predators, are the result of evolution, the process of change that has transformed life from its beginnings to the astounding array of organisms today. Evolution i
Introduction (3/4)
Although biologists know a great deal about life on Earth, many mysteries remain. The question of how the mice's coats have come to match the colors of their habitats is just one example. Posing questions about the living world and seeking answers through
Introduction (4/4)
How do biologists make sense of life's diversity and complexity? This open- ing chapter sets up a framework for answering this question. The first part of the chapter provides a panoramic view of the biological "landscape," organized around a set of unify
List the order of ecological categories from largest to smallest.
Biosphere, ecosystem, community, population, organism, organ system, tissue, cell, organelle, molecule
The Biosphere (Level 1)
Even from space, we can see signs of Earth's life�in the green mosaic of the forests, for example. We can also see the scale of the entire biosphere, which consists of all life on Earth and all the places where life exists: most regions of land, most bodi
Ecosystems (Level 2)
Our first scale change brings us to a North American forest with many deciduous trees (trees that lose their leaves and grow new ones each year). A deciduous forest is an example of an ecosystem, as are grasslands, deserts, and coral reefs. An ecosystem c
Community (Level 3)
The array of organisms inhabiting a particular ecosystem is called a biological community. The community in our forest ecosystem includes many kinds of trees and other plants, various animals, mushrooms and other fungi, and enormous numbers of diverse mic
Populations (Level 4)
A population consists of all the individuals of a species living within the bounds of a specified area. For example, our forest includes a population of sugar maple trees and a population of white-tailed deer. A community is therefore the set of populatio
Organisms (Level 5)
Individual living things are called organisms. Each of the maple trees and other plants in the forest is an organism, and so is each deer, frog, beetle, and other forest animals. The soil teems with microorganisms such as bacteria.
Organs and Organ Systems (Level 6)
The structural hierarchy of life continues to unfold as we explore the architecture of more complex organisms. A maple leaf is an example of an organ, a body part that carries out a particular function in the body. Stems and roots are the other major orga
Tissues (Level 7)
To see the tissues of a leaf requires a microscope. Each tissue is a group of cells that work together, performing a specialized function. The leaf shown here has been cut on an angle. The honeycombed tissue in the interior of the leaf (left side of photo
Cells (Level 8)
The cell is life's fundamental unit of structure and function. Some organisms are single cells, while others are multicellular. A single cell performs all the functions of life, while a multicellular organism has a division of labor among specialized cell
Organelles (Level 9)
Chloroplasts are examples of organelles, the various functional components present in cells. This image, taken by a powerful microscope, shows a single chloroplast.
Molecules (Level 10)
Our last scale change drops us into a chloroplast for a view of life at the molecular level. A molecule is a chemical structure consisting of two or more units called atoms, represented as balls in this computer graphic of a chlorophyll molecule. Chloroph
Theme: New Properties Emerge at Successive Levels of Biological Organization (1/2)
The study of life extends from the microscopic scale of the molecules and cells that make up organisms to the global scale of the entire living planet. As biologists, we can divide this enormous range into different levels of biologi- cal organization. Im
Theme: New Properties Emerge at Successive Levels of Biological Organization (2/2)
Zooming in at ever-finer resolution illustrates the principle of reductionism�the approach of reducing complex systems to simpler components that are more manageable to study. Reductionism is a powerful strategy in biology. For example, by studying the mo
Emergent Properties (1/2)
Let's reexamine Figure 1.3, beginning this time at the molecu- lar level and then zooming out. Viewed this way, we see that at each level, novel properties emerge that are absent from the preceding one. These emergent properties are due to the ar- rangeme
Emergent Properties (2/2)
Compared to such nonliving examples, however, the unrivaled complexity of biological systems makes the emergent proper- ties of life especially challenging to study. To fully explore emergent properties, biologists today complement reductionism with syste
Structure and Function (1/2)
At each level of the biological hierarchy, we find a correlation of structure and function. Consider the leaf in Figure 1.3: Its thin, flat shape maximizes the capture of sunlight by chloroplasts. More generally, analyzing a biological structure gives us
Structure and Function (2/2)
The hummingbird's anatomy allows the wings to rotate at the shoulder, so hummingbirds have the ability, unique among birds, to fly backward or hover in place. Hovering, the birds can extend their long slender beaks into flowers and feed on nectar. The ? F
The Cell: An Organism's Basic Unit of Structure and Function (1/2)
In life's structural hierarchy, the cell is the smallest unit of organization that can perform all required activities. In fact, the activities of organisms are all based on the activities of cells. For instance, the movement of your eyes as you read this
The Cell: An Organism's Basic Unit of Structure and Function (2/2)
All cells share certain characteristics. For instance, every cell is enclosed by a membrane that regulates the passage of materials between the cell and its surroundings. Nevertheless, we recognize two main forms of cells: prokaryotic and eukaryotic. The
theme: Life's processes Involve the expression and transmission of Genetic
Within cells, structures called chromosomes contain genetic material in the form of DNA (deoxyribonu- cleic acid). In cells that are preparing to divide, the chromo- somes may be made visible using a dye that appears blue when bound to the DNA (Figure 1.6
DNA Structure and Function (1/6)
Each time a cell divides, the DNA is first replicated, or copied, and each of the two cellular offspring inherits a complete set of chromosomes, identical to that of the parent cell. Each chromosome contains one very long DNA molecule with hundreds or tho
DNA Structure and Function (2/6)
The molecular structure of DNA accounts for its ability to store information. A DNA molecule is made up of two long chains, called strands, arranged in a double helix. Each chain is made up of four kinds of chemical building blocks called nucleotides, abb
DNA Structure and Function (3/6)
DNA provides the blueprints for making proteins, which are the major players in building and maintaining the cell and carrying out its activities. For instance, a particular bacterial gene may specify a certain enzyme protein required to assemble the cell
DNA Structure and Function (4/6)
Genes control protein production indirectly, using a re- lated molecule called RNA as an intermediary. The sequence of nucleotides along a gene is transcribed into RNA, which is then translated into a specific protein with a unique shape and function. Thi
DNA Structure and Function (5/6)
In translating genes into proteins, all forms of life employ essentially the same genetic code: A particular sequence of nucleotides says the same thing in one organism as it does in another. Differences between organisms reflect differences between their
DNA Structure and Function (6/6)
Not all RNA molecules in the cell are translated into protein; some RNAs carry out other important tasks. For example, we have known for decades that some types of RNA are actually components of the cellular machinery that manufactures proteins. Recently,
Genomics: Large-Scale Analysis of DNA Sequences (1/3)
The entire "library" of genetic instructions that an organism inherits is called its genome. A typical human cell has two similar sets of chromosomes, and each set has approximately 3 billion nucleotide pairs of DNA. If the one-letter abbreviations for th
Genomics: Large-Scale Analysis of DNA Sequences (2/3)
Since the early 1990s, the pace at which researchers can determine the sequence of a genome has accelerated at an almost unbelievable rate, enabled by a revolution in technology. The entire sequence of nucleotides in the human genome is now known, along w
Genomics: Large-Scale Analysis of DNA Sequences (3/3)
Three important research developments have made the genomic approach possible. One is "high-throughput" technology, tools that can analyze biological materials very rapidly. The second major development is bioinformatics, the use of computational tools to
Theme: Life Requires the Transfer and Transformation of Energy and Matter (1/2)
Moving, growing, reproducing, and the various cellular activities of life are work, and work requires energy. Input of energy, primarily from the sun, and transformation of energy from one form to another make life possible (Figure 1.9). Chlorophyll molec
Theme: Life Requires the Transfer and Transformation of Energy and Matter (2/2)
When an organism uses chemical energy to perform work, some of that energy is converted to thermal energy and is dissipated to the surroundings as heat. As a result, energy flows through an ecosystem, usually entering as light and exiting as heat. In cont
Theme: Organisms Interact with Other Organisms and the Physical Environment (1/2)
Turn again to Figure 1.3, this time focusing on the ecosystem, including the forest and its surroundings. Each organism interacts continuously with physical factors in its environment. Th e leaves of a tree, for example, absorb light from the sun, take in
Theme: Organisms Interact with Other Organisms and the Physical Environment (2/2)
A tree also interacts with other organisms, such as soil microorganisms associated with its roots, insects that live in the tree, and animals that eat its leaves and fruit. Such interactions between organisms include those that are mutually beneficial (Fi
Evolution, the Core Theme of Biology
Having considered four of the unifying themes that run through this text, let's now turn to biology's core theme� evolution. Evolution makes sense of everything we know about living organisms. Life has been evolving on Earth for billions of years, resulti
The Core Theme: Evolution accounts for the unity and diversity of life
Diversity is a hallmark of life. To date, biologists have identified and named about 1.8 million species of organ- isms, and estimates of the number of living species range from about 10million to over 100 million. The remarkably diverse forms of life on
Classifying the Diversity of Life: The Three Domains of Life (1/3)
Humans have a tendency to group diverse items according to their similarities and relationships to each other. Following this inclination, biologists have long used careful comparisons of form and function to classify life-forms into a hierarchy of increa
Classifying the Diversity of Life: The Three Domains of Life (2/3)
In the last few decades, new methods of assessing species relationships, especially comparisons of DNA sequences, have led to a reevaluation of the larger groupings. Although the re- evaluation is ongoing, there is consensus among biologists that the king
The three domains of living organisms are?
Bacteria, Archaea, Eukarya
Classifying the Diversity of Life: The Three Domains of Life (3/3)
As you read earlier, the organisms making up two of the three domains�Bacteria and Archaea�are prokaryotic. All the eukaryotes (organisms with eukaryotic cells) are grouped in domain Eukarya. This domain includes three kingdoms of multicellular eukaryotes
Unity in the Diversity of Life
As diverse as life is, it also displays remarkable unity. Earlier we mentioned both the similar skeletons of different vertebrate animals and the universal genetic language of DNA (the genetic code). In fact, similarities between organisms are evident at
Charles Darwin and the Theory of Natural Selection (1/4)
The history of life, as documented by fossils and other evidence, is the saga of a changing Earth billions of years old, in- habited by an evolving cast of living forms (Figure 1.12). This view of life came into sharp focus in November 1859, when Charles
Charles Darwin and the Theory of Natural Selection (2/4)
On the Origin of Species articulated two main points. The first was that species have arisen from a succession of ancestors that differed from them. Darwin called this process "descent with modification." It was an insightful phrase, as it captured the du
Charles Darwin and the Theory of Natural Selection (3/4)
Darwin developed his theory of natural selection from observations that by themselves were not revolutionary. Others had described the pieces of the puzzle, but Darwin saw how they fit together. He started with the following three observations from nature
Charles Darwin and the Theory of Natural Selection (4/4)
Darwin inferred that individuals with inherited traits that are better suited to the local environment are more likely to survive and reproduce than are less well-suited individuals. As a result, over many generations, a higher and higher pro- portion of
The Tree of Life (1/4)
For another example of unity and diversity, consider the human arm. Your forelimb has the same bones, joints, nerves, and blood vessels found in other limbs as diverse as the foreleg of a horse, the flipper of a whale, and the wing of a bat. Indeed, all m
The Tree of Life (2/4)
Darwin proposed that natural selection, by its cumulative effects over time, could cause an ancestral species to give rise to two or more descendant species. This could occur, for example, if one population of organisms fragmented into several subpopulati
The Tree of Life (3/4)
The "family tree" of six finch species in Figure 1.16 illustrates a famous example of this process of radiation. Darwin collected specimens of these birds during his 1835 visit to the remote Gala?pagos Islands, 900 kilometers (km) off the Pacific coast of
The Tree of Life (4/4)
Biologists' diagrams of such evolutionary relationships generally take treelike forms, though the trees are often turned sideways as in Figure 1.16. Tree diagrams make sense: Just as an individual has a genealogy that can be diagrammed as a family tree, e
Biological inquiry entails forming and testing hypotheses based on observations of nature (1/3)
The word science is derived from a Latin verb meaning "to know." Science is a way of knowing�an approach to under- standing the natural world. It developed out of our human curiosity about ourselves, other life-forms, our planet, and the universe. Strivin
Biological inquiry entails forming and testing hypotheses based on observations of nature (2/3)
At the heart of science is inquiry, a search for information and explanations of natural phenomena. There is no formula for successful scientific inquiry, no single scientific method that researchers must rigidly follow. As in all quests, science includes
Biological inquiry entails forming and testing hypotheses based on observations of nature (3/3)
Scientists use a process of inquiry that includes making ob- servations, forming logical hypotheses, and testing them. The process is necessarily repetitive: In testing a hypothesis, our observations may lead to conclusions that inspire revision of the or
Making Observations (1/3)
In the course of their work, scientists describe natural structures and processes as accurately as possible through careful observa- tion and analysis of data. Observation is the use of the senses to gather information either directly or indirectly, such
Making Observations (2/3)
The term data implies numbers to many people. But some data are qualitative, often in the form of recorded descriptions. For example, British primate researcher Jane Goodall spent decades recording her observations of chimpanzee behavior during field rese
Making Observations (3/3)
Collecting and analyzing observations can lead to impor- tant conclusions based on a type of logic called inductive reasoning. Through induction, we derive generalizations from a large number of specific observations. The generalization "All organisms are
Forming and Testing Hypotheses (1/3)
Our innate curiosity often stimulates us to pose questions about the natural basis for the phenomena we observe in the world. What caused the diversification of finches on the Gala?pagos Islands? What explains the variation in coat color among mice of a s
Forming and Testing Hypotheses (2/3)
In science, answering such questions usually involves proposing and testing hypothetical explanations�that is, hypotheses. In science, a hypothesis is a tentative answer to a well- framed question; it is an explanation on trial. The hypothesis is usually
Forming and Testing Hypotheses (3/3)
We all use hypotheses in solving everyday problems. Let's say, for example, that your flashlight fails during a camp-out. That's an observation. The question is obvious: Why doesn't the flashlight work? Two reasonable hypotheses based on your experience a
Deductive Reasoning
A type of logic called deduction is also built into the use of hypotheses in science. While induction entails reasoning from a set of specific observations to reach a general conclusion, deductive reasoning involves logic that flows in the opposite direct
Questions That Can and Cannot Be Addressed by Science
Scientific inquiry is a powerful way to learn about nature, but there are limitations to the kinds of questions it can answer. A scientific hypothesis must be falsifiable; there must be some observation or experiment that could reveal if such an idea is a
A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations
Now that we have highlighted the key features of scientific inquiry�making observations and forming and testing hypotheses�you should be able to recognize these features in a case study of actual scientific research.
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The story begins with a set of observations and inductive generalizations. Color patterns of animals vary widely in nature, sometimes even between members of the same species. What accounts for such variation? As you may recall, the two mice depicted at t
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As obvious as the camouflage hypothesis may seem, it still required testing. In 2010, biologist Hopi Hoekstra of Harvard University and a group of her students headed to Florida to test the prediction that mice with coloration that did not match their hab
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The researchers built hundreds of models of mice and spray-painted them to resemble either beach or inland mice, so that the models differed only in their color patterns. The researchers placed equal numbers of these model mice randomly in both habitats a
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For each environment, the researchers then calculated the fraction of predation events that targeted camouflaged mice. The results were clear-cut: Camouflaged mice showed much lower predation rates than those lacking camouflage in both the dune habitat (w
Experimental Controls
The mouse camouflage experiment described in Figure 1.19 is an example of a controlled experiment, one that is designed to compare an experimental group (the non-camouflaged mice, in this case) with a control group (the camouflaged mice normally resident
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A common misconception is that the term controlled ex- periment means that scientists control the experimental envi- ronment to keep everything constant except the one variable being tested. But that's impossible in field research and not realistic even i
Theories in Science (1/5)
It's just a theory!" Our everyday use of the term theory often implies an untested speculation. But the term theory has a dif- ferent meaning in science. What is a scientific theory, and how is it different from a hypothesis or from mere speculation?
Theories in Science (2/5)
First, a scientific theory is much broader in scope than a hypothesis. This is a hypothesis: "A match of the coloration of a mouse's coat to its environment is an adaptation that protects mice from predators." But this is a theory: "Evolutionary adap- tat
Theories in Science (3/5)
Second, a theory is general enough to spin off many new, testable hypotheses. For example, the theory of natural selection motivated two researchers at Princeton University, Peter and Rosemary Grant, to test the specific hypothesis that the beaks of Gala?
Theories in Science (4/5)
And third, compared to any one hypothesis, a theory is gen- erally supported by a much greater body of evidence. Those theories that become widely adopted in science (such as the theory of natural selection) explain a great diversity of observa- tions and
Theories in Science (5/5)
In spite of the body of evidence supporting a widely ac- cepted theory, scientists must sometimes modify or even reject theories when new research methods produce results that don't fit. For example, biologists once lumped bacteria and archaea together as
Science as a Social Process: Community and Diversity
The great scientist Sir Isaac Newton once said: "To explain all nature is too difficult a task for any one man or even for any one age. 'Tis much better to do a little with certainty, and leave the rest for others that come after you. . . ." Anyone who be
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Science is rarely perfectly objective, but it is continuously vetted through the expectation that observations and experi- ments be repeatable and hypotheses be falsifiable. Scientists working in the same research field often check one another's claims by
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If experimental results cannot be repeated by scientific col- leagues, this failure may reflect some underlying weakness in the original claim, which will then have to be revised. In this sense, science polices itself. Integrity and adherence to high prof
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Biologists may approach questions from different angles. Some biologists focus on ecosystems, while others study natu- ral phenomena at the level of organisms or cells. This text is Scientific Skills Exercise Interpreting a Pair of Bar Graphs divided into
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The research community is part of society at large. The rela- tionship of science to society becomes clearer when we add tech- nology to the picture. The goal of technology is to apply scientific knowledge for some specific purpose. Because scientists put
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In centuries past, many major technological innovations orig- inated along trade routes, where a rich mix of different cultures ignited new ideas. For example, the printing press was invented by Johannes Gutenberg around 1440, living in what is now Ger- m
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The scientific community reflects the customs and behav- iors of society at large. It is therefore not surprising that until recently, women and certain minorities have faced huge obsta- cles in their pursuit to become professional scientists. Over the pa