Biology / Peter H. Raven ... [et al.] ; illustration authors, William C. Ober and Claire W. Garrison.

Rev. ed. of: Biology / Peter H. Raven and George B. Johnson. 6th ed. c2002.

Contents
Chemical Biology
Part I The Origin of Living Things
1
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.
2
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.
3
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.
4
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
bacteria.
Cell Biology
Part II Biology of the Cell
5
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
organelles.
6
Membranes
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
information.
6.1 Biological membranes are fluid layers of lipid.
6.2 Proteins embedded within the plasma membrane determine its
character.
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
ATP.
7
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
8
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.
9
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
energy.
9.4 Cells can metabolize food without oxygen.
10
Photosynthesis
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.
Genetics
Part IV Reproduction and Heredity
11
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.
12
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
divisions.
12.4 The evolutionary origin of sex is a puzzle.
13
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.
Genetics
Part V Molecular Genetics
14
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?
15
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
information.
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.
16
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
distance.
17
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
development.
17.3 Four model developmental systems have been extensively
researched.
17.4 Aging can be considered a developmental process.
18
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.
19
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
20
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.
21
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
biology.
21.4 The theory of evolution has proven controversial.
22
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.
23
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
primates.
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
24
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
together.
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
centuries.
25
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
niches.
25.2 Predators and their prey coevolve.
25.3 Evolution sometimes fosters cooperation.
25.4 Ecological succession may increase species richness.
26
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
behavior.
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.
27
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
selection.
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
28
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.
29
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.
30
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
world.
30.3 Human activity is placing the environment under increasing
stress.
30.4 Solving environmental problems requires individual
involvement.
31
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
32
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
categories.
33
Viruses
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
coat.
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
diseases.
34
Bacteria
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
supposed.
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.
35
Protists
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
kingdom.
35.2 Protists can be categorized into five groups.
36
Fungi
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.
Plants
Part X Plant Form and Function
37
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.
38
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.
39
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
40
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.
41
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
growth.
42
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?
43
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
animals.
43.2 Advances in plant tissue culture are revolutionizing
agriculture.
43.3 Plant biotechnology now affects every aspect of agriculture.
Animals
Part XII Animal Diversity
44
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.
45
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
species!
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.
46
Arthropods
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
successful.
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.
47
Echinoderms
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.
48
Vertebrates
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
movement.
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
49
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
systems.
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.
50
Locomotion
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.
51
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
functions.
51.4 Accessory organs, neural stimulation, and endocrine
secretions assist in digestion.
51.5 All animals require food energy and essential nutrients.
52
Circulation
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
change.
52.4 The cardiac cycle drives the cardiovascular system.
53
Respiration
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.
Animals
Part XIV Regulating the Animal Body
54
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
cord.
54.5 The peripheral nervous system consists of sensory and motor
neurons.
55
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
employ.
55.1 Animals employ a wide variety of sensory receptors.
55.2 Mechanical and chemical receptors sense the body's
condition.
55.3 Auditory receptors detect pressure waves in the air.
55.4 Optic receptors detect light over a broad range of
wavelengths.
55.5 Some vertebrates use heat, electricity, or magnetism for
orientation.
56
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
gland.
56.4 Endocrine glands secrete hormones that regulate many body
functions.
57
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
antigens.
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.
58
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
vertebrates.
58.3 The functions of the vertebrate kidney are performed by
nephrons.
58.4 The kidney is regulated by hormones.
59
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
strategies.
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.
60
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.