Table of contents for Biology / Peter H. Raven ... [et al.].

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Chemical Biology
Part I The Origin of Living Things
The Science of Biology 
Science is the process of testing ideas against observation. Darwin 
developed his ideas about evolution by testing them against a wealth of 
observation. In this text science will provide the framework for your 
exploration of life.
	1.1	Biology is the science of life.
	1.2	Scientists form generalizations from observations.
	1.3	Darwin's theory of evolution illustrates how science works.
	1.4	This book is organized to help you learn biology.
The Nature of Molecules 
Organisms are chemical machines, and to understand them we must first 
learn a little chemistry. We first explore how atoms are linked together 
into molecules. The character of the water molecule in large measure 
determines what organisms are like.
	2.1	Atoms are nature's building material.
	2.2	The atoms of living things are among the smallest.
	2.3	Chemical bonds hold molecules together.
	2.4	Water is the cradle of life.
The Chemical Building Blocks of Life 
The four kinds of large macromolecules that are the building blocks of 
organisms are each built up of long chains of carbon atoms. In each, the 
macromolecule is assembled as a long chain of subunits, like pearls in a 
necklace or cars of a railway train.
	3.1	Molecules are the building blocks of life.
	3.2	Proteins perform the chemistry of the cell.
	3.3	Nucleic acids store and transfer genetic information.
	3.4	Lipids make membranes and store energy.
	3.5	Carbohydrates store energy and provide building materials.
The Origin and Early History of Life 
Little is known about how life originated on earth. If it originated 
spontaneously, as most biologists surmise, then it must have evolved 
very quickly, as microfossils of bacteria are found in rocks formed soon 
after earth's surface cooled.
	4.1	All living things share key characteristics.
	4.2	There are many ideas about the origin of life.
	4.3	The first cells had little internal structure.
	4.4	The first eukaryotic cells were larger and more complex than 
Cell Biology
Part II Biology of the Cell
Cell Structure 
Bacterial cells have little internal organization, while the cells of 
eukaryotes are subdivided by internal membranes into numerous 
compartments with different functions. Compartmentalization is the 
hallmark of the eukaryotic cell.
	5.1	All organisms are composed of cells.
	5.2	Eukaryotic cells are far more complex than bacterial cells.
	5.3	Take a tour of a eukaryotic cell.
	5.4	Symbiosis played a key role in the origin of some eukaryotic 
Every cell is encased within a thin membrane that separates it from its 
environment. The membrane is a mosaic of proteins floating on a sheet of 
lipid that provide channels into the cell for both molecules and 
	6.1	Biological membranes are fluid layers of lipid.
	6.2	Proteins embedded within the plasma membrane determine its 
	6.3	Passive transport across membranes moves down the 
concentration gradient.
	6.4	Bulk transport utilizes endocytosis.
	6.5	Active transport across membranes is powered by energy from 
Cell-Cell Interactions 
Cells receive molecular signals with protein receptors on or within the 
plasma membrane. The information passes into the cell interior as a 
cascade of interactions that greatly amplify the strength of the 
original signal.
	7.1	Cells signal one another with chemicals.
	7.2	Proteins in the cell and on its surface receive signals from 
other cells.
	7.3	Follow the journey of information into the cell.
	7.4	Cell surface proteins mediate cell-cell interactions.
Cell Biology
Part III Energetics
Energy and Metabolism 
Organisms use proteins called enzymes to facilitate chemical reactions. 
When the products of a reaction contain more energy than the starting 
materials, the extra amount is supplied by ATP, the energy currency of 
the cell.
	8.1	The laws of thermodynamics describe how energy changes.
	8.2	Enzymes are biological catalysts.
	8.3	ATP is the energy currency of life.
	8.4	Metabolism is the chemical life of a cell.
How Cells Harvest Energy 
Cells harvest chemical energy from the C-H chemical bonds of food 
molecules. Some of this energy is captured by rearranging chemical 
bonds, but most of it is harvested by oxidation, in reactions where the 
electrons of C-H bonds are used to reduce atmospheric oxygen to water.
	9.1	Cells harvest the energy in chemical bonds.
	9.2	Cellular respiration oxidizes food molecules.
	9.3	Catabolism of proteins and fats can yield considerable 
	9.4	Cells can metabolize food without oxygen.
Photosynthesis is the reverse of respiration, the energy of sunlight 
being harnessed to reduce carbon dioxide with electrons obtained from 
water, leaving oxygen gas as the by-product. All organic molecules are 
the direct or indirect products of photosynthetic carbon fixation.
	10.1	What is photosynthesis?
	10.2	Learning about photosynthesis: An experimental journey.
	10.3	Pigments capture energy from sunlight.
	10.4	Cells use the energy and reducing power captured by the 
light reactions to make organic molecules. 
	Part IV Reproduction and Heredity
How Cells Divide 
The division of a eukaryotic cell involves a complex and carefully 
orchestrated division of chromosome copies to the daughter cells. The 
genes which control cell division are among the most crucial in the 
genome. Damage to them often results in cancer. 
	11.1	Bacteria divide far more simply than do eukaryotes.
	11.2	Chromosomes are highly ordered structures.
	11.3	Mitosis is a key phase of the cell cycle.
	11.4	The cell cycle is carefully controlled.
Sexual Reproduction and Meiosis 
Sexual reproduction is only possible because of a special form of cell 
division called meiosis that reduces the diploid number of chromosomes 
in half; fertilization then restores the diploid number. Sexual 
reproduction may have evolved as a way to repair damaged DNA, although 
other explanations are also being actively considered.
	12.1	Meiosis produces haploid cells from diploid cells.
	12.2	Meiosis has three unique features.
	12.3	The sequence of events during meiosis involves two nuclear 
	12.4	The evolutionary origin of sex is a puzzle.
Patterns of Inheritance 
Mendel's theory of heredity rests squarely on the assumption that what 
is inherited is information rather than the traits themselves. Once 
researchers understood that the information resided on chromosomes, the 
reason for Mendelian segregation became clear.
	13.1	Mendel solved the mystery of heredity.
	13.2	Human genetics follows Mendelian principles.
	13.3	Genes are on chromosomes.
Part V Molecular Genetics
DNA: The Genetic Material 
The experiments demonstrating that DNA is the hereditary material are 
among the most elegant in biology. Its double helical structure leads 
directly to a mechanism for replicating the molecule that is simple and 
relatively free of errors.
	14.1	What is the genetic material?
	14.2	What is the structure of DNA?
	14.3	How does DNA replicate?
	14.4	What is a gene?
Genes and How They Work 
Gene expression is the mechanism translating the genetic information 
into the practical reality of what organisms are like. It involves first 
transcribing a working copy of a gene, then using that copy to direct 
the assembly of a specific protein.
	15.1	The Central Dogma traces the flow of gene-encoded 
	15.2	Genes encode information in three-nucleotide code words.
	15.3	Genes are first transcribed, then translated.
	15.4	Eukaryotic gene transcripts are spliced.
Control of Gene Expression 
The key to controlling development is to control when particular genes 
are transcribed. This is done by proteins that can read the DNA double 
helix without unwinding it, slipping protein segments called "motifs" 
into the major groove of the double helix.
	16.1	Gene expression is controlled by regulating transcription.
	16.2	Regulatory proteins read DNA without unwinding it.
	16.3	Bacteria limit transcription by blocking RNA polymerase.
	16.4	Transcriptional control in eukaryotes operates at a 
Cellular Mechanisms of Development 
Vertebrate development is quite different from that of solid worms, 
insects, or plants, although it shares with these other approaches a 
common set of basic mechanisms. Detailed study of a few "model systems" 
has told us a great deal about how development occurs.
	17.1	Development is a regulated process.
	17.2	Multicellular organisms employ the same basic mechanisms of 
	17.3	Four model developmental systems have been extensively 
	17.4	Aging can be considered a developmental process.
Altering the Genetic Message 
The genetic message can be altered by mutation, which changes or 
destroys its content, and by recombination, which alters gene location. 
Cancer results from mutation of growth-regulating genes, often as the 
result of cigarette smoking or diet.
	18.1	Mutations are changes in the genetic message.
	18.2	Cancer results from mutation of growth-regulating genes.
	18.3	Recombination alters gene location.
	18.4	Genomes are continually evolving.
Gene Technology 
Enzymes that cleave DNA at particular sites have allowed scientists to 
manipulate the genetic message, creating new combinations of genes that 
are revolutionizing medicine and agriculture. Every one of us will be 
affected by gene technology.
	19.1	The ability to manipulate DNA has led to a new genetics.
	19.2	Genetic engineering involves easily understood procedures.
	19.3	Biotechnology is producing a scientific revolution.
Evolution and Ecology 
Part VI Evolution
Genes within Populations 
Evolution occurs within populations when one allele becomes more 
frequent than another. The study of why allele frequencies change within 
populations has occupied geneticists for over a century, and a clear 
picture is now beginning to emerge.
	20.1	Genes vary in natural populations.
	20.2	Why do allele frequencies change in populations?
	20.3	Selection can act on traits affected by many genes.
The Evidence for Evolution 
Adaptive allele changes within populations have been demonstrated many 
times, and a variety of evidence, much of it compelling, argues that 
these changes lead to the macroevolutionary changes familiar to us as 
the fossil record.
	21.1	Fossil evidence indicates that evolution has occurred.
	21.2	Natural selection can produce evolutionary change.
	21.3	Evidence for evolution can be found in other fields of 
	21.4	The theory of evolution has proven controversial.
The Origin of Species 
Species, the basic units of evolution, originate when two populations of 
a species adapt to different environments. Selection will tend to favor 
changes that inhibit gene flow between them, eventually creating a 
genetic barrier that isolates the populations.
	22.1	Species are the basic units of evolution.
	22.2	Species maintain their genetic distinctiveness through 
barriers to reproduction.
	22.3	We have learned a great deal about how species form.
	22.4	Clusters of species reflect rapid evolution.
How Humans Evolved 
Humans evolved in Africa from a bipedal kind of ape called an 
australopithecine some two million years ago. The first humans to leave 
Africa, H. erectus, spread across the earth over a million years ago. 
How modern humans replaced them is a matter of some controversy.
	23.1	The evolutionary path to humans starts with the advent of 
	23.2	The first hominids to evolve were australopithecines.
	23.3	The genus Homo evolved in Africa.
	23.4	Modern humans evolved quite recently.
	Part VII Ecology and Behavior
Population Ecology 
The way in which a population grows depends importantly upon how many 
young individuals it contains. The way in which a species reproduces 
represents an evolutionary trade-off between reproductive cost and 
investment in survival.
	24.1	Populations are individuals of the same species that live 
	24.2	Population dynamics depend critically upon age distribution.
	24.3	Life histories often reflect trade-offs between reproduction 
and survival.
	24.4	Population growth is limited by the environment.
	24.5	The human population has grown explosively in the last three 
Community Ecology 
Organisms make complex evolutionary adjustments to living together 
within communities. Some adjustments involve cooperation, others 
capturing prey or avoiding being captured. 
	25.1	Interactions among competing species shape ecological 
	25.2	Predators and their prey coevolve.
	25.3	Evolution sometimes fosters cooperation.
	25.4	Ecological succession may increase species richness.
Animal Behavior 
The study of animal behavior has historically been carried out in two 
quite different ways, which are only now merging into a unified view. 
One stressed fixed behaviors constrained by neural organization, the 
other flexible behaviors influenced by learning.
	26.1	Ethology focuses on the natural history of behavior.
	26.2	Comparative psychology focuses on how learning influences 
	26.3	Communication is a key element of many animal behaviors.
	26.4	Migratory behavior presents many puzzles.
	26.5	To what degree animals "think" is a subject of lively dispute.
Behavioral Ecology 
Much of the excitement in behavioral science today comes from analysis 
of how evolution has shaped, and is shaping, the behavior of animal 
species in natural populations. Often quite controversial, these studies 
combine theory and careful field observation.
	27.1	Evolutionary forces shape behavior.
	27.2	Reproductive behavior involves many choices influenced by natural 
	27.3	There is considerable controversy about the evolution of 
social behavior.
	27.4	Vertebrates exhibit a broad range of social behaviors.
Evolution and Ecology 
Part VIII The Global Environment
Dynamics of Ecosystems 
Ecological systems are dynamic "machines" in which chemicals cycle 
between organisms and the environment and energy is used as it passes 
through the system. Much energy is lost to heat at each step of its 
journey through living things. In general, communities with more species 
interacting with one another are more stable.
	28.1	Chemicals cycle within ecosystems.
	28.2	Ecosystems are structured by who eats whom.
	28.3	Energy flows through ecosystems.
	28.4	Biodiversity promotes ecosystem stability.
The Biosphere 
The sun powers major movements of the atmosphere that circulate heat and 
moisture over the surface of the globe, creating different climates in 
different locales. Each characteristic climate favors a particular 
community of organisms adapted to living there.
	29.1	Organisms must cope with a varied environment.
	29.2	Climate shapes the character of ecosystems.
	29.3	Biomes are widespread terrestrial ecosystems.
	29.4	Aquatic ecosystems cover much of the earth.
The Future of the Biosphere 
The world's human population is growing at an explosive rate, placing a 
severe strain on the world's ecosystems. No one knows if the world can 
sustain the 6 billion people it now contains-and the population will 
soon grow much larger.
	30.1	The world's human population is growing explosively.
	30.2	Improvements in agriculture are needed to feed a hungry 
	30.3	Human activity is placing the environment under increasing 
	30.4	Solving environmental problems requires individual 
Conservation Biology 
The successive efforts to halt the world's alarming loss of biodiversity 
will depend critically on our gaining a better understanding of what 
forces threaten species survival, and how they can be counteracted.
	31.1	The new science of conservation biology is focused on 
conserving biodiversity.
	31.2	Vulnerable species are more likely to become extinct.
	31.3	Causes of endangerment usually reflect human activities.
	31.4	Successful recovery plans will need to be multidimensional.
	Simple Organisms
	Part IX Viruses and Simple Organisms
How We Classify Organisms 
The living world is a rich tapestry of diversity, teeming with different 
kinds of organisms. One of the great challenges of biology is to find 
sensible ways to name and classify kinds of organisms, ways that tell us 
about them and how they relate to each other.
	32.1	Biologists name organisms in a systematic way.
	32.2	Scientists construct phylogenies to understand the 
evolutionary relationships among organisms.
	32.3	All living organisms are grouped into one of a few major 
Viruses are not considered organisms because they lack cellular 
structure. However, because they can replicate themselves within the 
cells of organisms, viruses are able to evolve, and are responsible for 
a broad array of serious diseases.
	33.1	Viruses are strands of nucleic acid encased within a protein 
	33.2	Bacterial viruses exhibit two sorts of reproductive cycles.
	33.3	HIV is a complex animal virus.
	33.4	Non-living infectious agents are responsible for many human 
Bacteria are the simplest organisms, composed of single cells that lack 
the complex internal organization seen in all other cells. Biologists 
believe bacteria were the first organisms to evolve on earth, and they 
are easily the most numerous and successful.
	34.1	Bacteria are the smallest and most numerous organisms.
	34.2	Bacterial cell structure is more complex than commonly 
	34.3	Bacteria exhibit considerable diversity in both structure 
and metabolism.
	34.4	Bacteria are responsible for many diseases but also make 
important contributions to ecosystems.
All eukaryotic organisms that are not fungi, plants, or animals are 
lumped together in a catch-all category called protists. Except for the 
marine algae, all protists are unicellular, but the diversity among 
protists is so great that it is difficult to compare them.
	35.1	Eukaryotes probably arose by endosymbiosis.
	35.1	The kingdom Protista is by far the most diverse of any 
	35.2	Protists can be categorized into five groups.
Fungi are extraordinarily strange multicellular organisms whose cells 
share cytoplasm and nuclei. Fungi absorb their food from their 
surroundings, first excreting digestive enzymes, then soaking up the 
resulting soup of molecular fragments. 
	36.1	Fungi are unlike any other kind of organism.
	36.2	Fungi are classified by their reproductive structures.
	36.3	Fungi form two key mutualistic symbiotic associations.
Part X Plant Form and Function
Evolutionary History of Plants 
Plants are responsible for much of the photosynthesis that supports life 
on earth. Early plants resembled nonvascular mosses in having no 
internal structures to move water up and down the stem. Their vascular 
descendants added seeds and then flowers.
	37.1	Plants have multicellular haploid and diploid stages in 
their life cycles.
	37.2	Nonvascular plants are relatively unspecialized but 
successful in many terrestrial environments.
	37.3	Seedless vascular plants have well-developed conducting 
tissues in their sporophytes.
	37.4	Seeds protect and aid in the dispersal of plant embryos.
The Plant Body 
A plant is basically a tubular stem with roots attached to the bottom 
and leaves to the top. Growth occurs at the tip of the shoot, at the 
ends of the roots, and in a sheath around the plant stem. Roots gather 
in nutrients from the soil, while leaves carry out photosynthesis.
	38.1	Meristems elaborate the plant body plan after germination.
	38.2	Plants have three basic tissues, each composed of several 
cell types.
	38.3	Root cells differentiate as they become distanced from the 
dividing root apical meristem.
	38.4	Stems are the backbone of the shoot, transporting nutrients 
and supporting the aerial plant organs.
	38.5	Leaves are adapted to support basic plant functions.
Nutrition and Transport in Plants 
Plants require a variety of mineral nutrients that they obtain from the 
soil. Nutrients are carried from the roots to the leaves dissolved in 
water, which is sucked up the stem through the xylem by transpiration 
from the leaves. Carbohydrates are carried from the leaves to the roots 
dissolved in water that travels down the phloem. 
	39.1	Plants require a variety of nutrients in addition to the 
direct products of photosynthesis.
	39.2	Some plants have novel strategies for obtaining nutrients.
	39.3	Water and minerals move upward through the xylem.
	39.4	Dissolved sugars and hormones are transported in the phloem.
Part XI Plant Growth and Reproduction
Early Plant Development 
The plant body develops in modules of leaf, shoot, and root. The course 
of the plant body's development is strongly influenced by the 
environment. Many plant structures, including seeds and fruits, have 
evolved to aid dispersal of offspring to new locations.
	40.1	Plant embryo development establishes a basic body plan.
	40.2	The seed protects the dormant embryo from water loss.
	40.3	Fruit formation enhances the dispersal of seeds.
	40.4	Germination initiates post-seed development.
How Plants Grow in Response to Their Environment 
Every plant cell contains a full set of hereditary information. 
Which genes are expressed is controlled by a set of plant hormones, including 
auxin, ethylene, and many others. These hormones interact with each 
other and with the environment to determine the pattern of growth.
	41.1	Plant growth is often guided by environmental cues.
	41.2	The hormones that guide growth are keyed to the environment.
	41.3	The environment influences flowering.
	41.4	Many short-term responses to the environment do not require 
Plant Reproduction 
Many plants can clone themselves by asexual reproduction. Some plants 
use the wind to transport pollen from male to female. A much more 
efficient delivery system is employed by flowering plants, which use 
insects to carry pollen from flower to flower.
	42.1	Angiosperms have been incredibly successful, in part, 
because of their reproductive strategies.
	42.2	Flowering plants use animals or wind to transfer pollen 
between flowers.
	42.3	Many plants can clone themselves by asexual reproduction.
	42.4	How long do plants and plant organs live?
Plant Genomics 
Plants organize their hereditary material in a more complex way than 
animals, with extensive regions of repetitive DNA and often many copies 
of chromosomes. Cloning plants in tissue culture and altering their 
genes have led to major agricultural advances.
	43.1	Genomic organization is much more varied in plants than in 
	43.2	Advances in plant tissue culture are revolutionizing 
	43.3	Plant biotechnology now affects every aspect of agriculture.
Part XII Animal Diversity
The Noncoelomate Animals 
The simplest animals lack a coelomic body cavity. The most ancient are 
the sponges, which lack tissues. Many of these evolutionarily old 
noncoelomate animals are called "worms," but this simple designation 
hides a great diversity of form and function.
	44.1	Animals are multicellular heterotrophs without cell walls.
	44.2	The simplest animals are not bilaterally symmetrical.
	44.3	Acoelomates are solid worms that lack a body cavity.
	44.4	Pseudocoelomates have a simple body cavity.
	44.5	The coming revolution in animal taxonomy will likely alter 
traditional phylogenies.
Mollusks and Annelids 
Mollusks and annelid worms, both of which originated in the sea and have 
similar larvae, are also very successful on land. Indeed, there are more 
terrestrial species of mollusks than there are terrestrial vertebrate 
	45.1	Mollusks were among the first coelomates.
	45.2	Annelids were the first segmented animals.
	45.3	Lophophorates appear to be a transitional group.
Arthropods are easily the most successful animal group, particularly the 
insects. Along with the jointed appendages that are the hallmark of 
arthropods, insects evolved wings. There are more species of beetles 
than there are of any nonarthropod animal phylum.
	46.1	The evolution of jointed appendages has made arthropods very 
	46.2	The chelicerates all have fangs or pincers.
	46.3	Crustaceans have branched appendages.
	46.4	Insects are the most diverse of all animal groups.
The vertebrates closest relatives among the animals are echinoderms, 
what most people think of as "starfish." Like vertebrates, they have 
deuterostome development and an endoskeleton. Unlike vertebrates, 
however, echinoderms are radially symmetrical as adults.
	47.1	The embryos of deuterostomes develop quite differently from 
those of protostomes.
	47.2	Echinoderms are deuterostomes with an endoskeleton.
	47.3	The six classes of echinoderms are all radially symmetrical 
as adults.
Vertebrates are members of the phylum Chordata, all of whose members 
have a notochord at some stage in their development. The hallmark of 
vertebrates is an interior skeleton of bone which provides a superb 
framework for muscle attachment.
	48.1	Attaching muscles to an internal framework greatly improves 
	48.2	Nonvertebrate chordates have a notochord but no backbone.
	48.3	The vertebrates have an interior framework of bone.
	48.4	The evolution of vertebrates involves invasions of sea, 
land, and air.
Part XIII Animal Form and Function
Organization of the Animal Body 
Although they at first glance seem quite different from one another, all 
vertebrates are basically similar in body design, using the same array 
of tissues to form a similar array of organs. Vertebrates differ 
principally in the degree of terrestrial adaptation.
	49.1	The bodies of vertebrates are organized into functional 
	49.2	Epithelial tissue forms membranes and glands.
	49.3	Connective tissues contain abundant extracellular material.
	49.4	 Muscle tissue provides for movement, and nerve tissue 
provides for control.
Muscle tissue, because it can contract, allows animals to move about. 
Some animals, like fish and snakes, move their entire bodies, while 
others move limbs such as arms, legs, or wings. The contraction of 
muscle is powered by ATP and controlled by the nervous system.
	50.1	A skeletal system supports movement in animals.
	50.2	Skeletal muscles contract to produce movements at joints.
	50.3	Muscle contraction powers animal locomotion.
Fueling Body Activities: Digestion 
Before the cells of an animal can assimilate fatty acids, sugars, and 
amino acids to use in manufacturing ATP, these "food" molecules must be 
cleaved out of far larger fats, carbohydrates, and proteins. This 
process of digestion takes place in the stomach and small intestine.
	51.1	Animals employ a digestive system to prepare food for 
assimilation by cells.
	51.2	Food is ingested, swallowed, and transported to the stomach.
	51.3	The small and large intestines have very different 
	51.4	Accessory organs, neural stimulation, and endocrine 
secretions assist in digestion.
	51.5	All animals require food energy and essential nutrients.
The highway that carries materials from one place to another in the 
vertebrate body is a network of flexible pipes called arteries and 
veins. A muscular pump called the heart pushes a rich fluid called blood 
through these pipes to every organ in the body.
	52.1	The circulatory systems of animals may be open or closed.
	52.2	A network of vessels transports blood through the body.
	52.3	The vertebrate heart has undergone progressive evolutionary 
	52.4	The cardiac cycle drives the cardiovascular system.
One of the most important cargos carried by blood are two gases, oxygen 
and carbon dioxide. In the lungs, blood picks up oxygen from the air and 
dumps carbon dioxide acquired from the body's tissues as a by-product of 
their respiratory metabolism. 
	53.1	Respiration involves the diffusion of gases.
	53.2	Gills are used for respiration by aquatic vertebrates.
	53.3	Lungs are used for respiration by terrestrial vertebrates.
	53.4	Mammalian breathing is a dynamic process.
	53.5	Blood transports oxygen and carbon dioxide.
Part XIV Regulating the Animal Body
The Nervous System 
The activities of the many organs of the vertebrate body are coordinated 
by the nervous system, an extensive network of neuron cells connecting 
all organs of the body. At a central coordinating center, the brain, 
information is processed, associations made, and commands given.
	54.1	The nervous system consists of neurons and supporting cells.
	54.2	Nerve impulses are produced on the axon membrane.
	54.3	Neurons form junctions called synapses with other cells.
	54.4	The central nervous system consists of the brain and spinal 
	54.5	The peripheral nervous system consists of sensory and motor 
Sensory Systems 
Information used by the nervous system to coordinate the body's 
activities comes from a system of sensors that collects information 
about the body's condition, its position in space, and what is going on 
around it. Vertebrates differ substantially in which sensors they 
	55.1	Animals employ a wide variety of sensory receptors.
	55.2	Mechanical and chemical receptors sense the body's 
	55.3	Auditory receptors detect pressure waves in the air.
	55.4	Optic receptors detect light over a broad range of 
	55.5	Some vertebrates use heat, electricity, or magnetism for 
The Endocrine System 
The vertebrate nervous system uses long-lasting chemical signals called 
hormones to coordinate many physiological and developmental processes. 
The cells that secrete these hormones are often regulated by a set of 
command hormones released by the brain.
	56.1	Regulation is often accomplished by chemical messengers.
	56.2	Lipophilic and polar hormones regulate their target cells 
by different means.
	56.3	The hypothalamus controls the secretions of the pituitary 
	56.4	Endocrine glands secrete hormones that regulate many body 
The Immune System 
Vertebrates defend themselves from infection by viruses, bacteria, and 
other microbes with an army of circulating cells that seek out and check 
the identity of all cells in the body. When a stranger is identified, 
other "killer" cells are called in to deal with the invader.
	57.1	Many of the body's most effective defenses are nonspecific.
	57.2	Specific immune defenses require the recognition of 
	57.3	T cells organize attacks against invading microbes.
	57.4	B cells label specific cells for destruction.
	57.5	All animals exhibit nonspecific immune response but specific 
ones evolved invertebrates.
	57.6	The immune system can be defeated.
Maintaining the Internal Environment 
Vertebrates maintain internal conditions at constant values, often quite 
different from those of their environment. This is particularly true of 
temperature and salt levels. Vertebrates go to great pains to maintain 
body temperature and avoid water loss or gain.
	58.1	The regulatory systems of the body maintain homeostasis.
	58.2	The extracellular fluid concentration is constant in most 
	58.3	The functions of the vertebrate kidney are performed by 
	58.4	The kidney is regulated by hormones.
Sex and Reproduction 1
Vertebrates usually reproduce sexually, although asexual reproduction is 
not impossible for them. In the sea, females release eggs into the water 
for external fertilization by the males' sperm. On land, evolution has 
favored internal fertilization.
	59.1	Animals employ both sexual and asexual reproductive 
	59.2	The evolution of reproduction among the vertebrates has led 
to internalization of fertilization and development.
	59.3	Male and female reproductive systems are specialized for 
different functions.
	59.4	The physiology of human sexual intercourse is becoming 
better known.
Vertebrate Development 
In vertebrates, the path of development from fertilization to birth is 
well known. The development of the embryo undergoes its key stages early 
on, determining the basic architecture of the body and its tissues. 
Thereafter, much of what occurs is growth.
	60.1	Fertilization is the initial event in development.
	60.2	Cell cleavage and the formation of a blastula set the stage 
for later development.
	60.3	Gastrulation forms the three germ layers of the embryo.
	60.4	Body architecture is determined during the next stages of 
embryonic development.
	60.5	Human development is divided into trimesters.

Library of Congress Subject Headings for this publication: Biology