Biol 1202 Exam 3

Front 1

Derive their name from vertebrae, the series of bones that make up the vertebral column, or backbone.

Back 1

Vertbrates

Front 2

Concept 34.1:

Back 2

Chordates have a notochord and a dorsal, hollow nerve cord

Front 3

Subphylum of Chordata

Back 3

Vertebrates

Front 4

Are bilaterian (bilaterally symmetrical) animals, and within Bilateria, they belong to the clade of animals known as Deuterostomia.

Back 4

Chordates

Front 5

Derived Characters of Chordates:

Back 5

A notochord,
a dorsal, hollow nerve cord, pharyngeal slits or clefts,
and a muscular, post-anal tail.

Front 6

Chordates are named for this skeletal structure present in all chordate embryos as well as in some adult chordates.

Back 6

Notochord

Front 7

A longitudinal, flexible rod located between the digestive tube and the nerve cord. It is composed of large, fluid-filled cells encased in fairly stiff, fibrous tissue. It provides skeletal support throughout most of the length of a chordate, and in larvae or adults that retain it, it also provides a firm but flexible structure against which muscles can work during swimming.

Back 7

Notochord

Front 8

The nerve cord of a chordate embryo develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord. The resulting ____________ is unique to chordates.

Back 8

Dorsal, hollow nerve cord

Front 9

The nerve cord of a chordate embryo develops into the _______: the brain and spinal cord.

Back 9

Central nervous system

Front 10

The region just posterior to the mouth is the _________.

Back 10

Pharynx

Front 11

In all chordate embryos, a series of pouches separated by grooves forms along th sides of the pharynx. In most chordates, these grooves are known as __________ and develop into slits that open to the outside of the body.

Back 11

Pharyngeal clefts

Front 12

These allow water entering the mouth to exit the body without passing suspension-feeding device.

Back 12

Pharyngeal slits

Front 13

Pharyngeal slits function as __________ devices in many invertebrate chordates.

Back 13

Suspension-feeding

Front 14

Chordates also have a _________ extending posterior to the anus, although in many species it is lost during embryonic development.

Back 14

Tail

Front 15

The chordate tail contains skeletal elements and muscles, and it provides much of the _________ force in many aquatic species.

Back 15

Propelling

Front 16

Subphylum ___________ are tunicates that resemble other chordates during their larval stage, which may be as brief as a few minutes.

Back 16

Urochordata

Front 17

Tunicates belong in the subphylum ________.

Back 17

Urochordata

Front 18

The tunicates most resemble other chordates during their _____ stage, which may be as brief as a few minutes.

Back 18

Larval

Front 19

As an adult, tunicate draws in water through an incurrent _______; the water then passes through the pharyngeal slits into a chamber called the ______ and exist through the excurrent _______.

Back 19

Siphon; atrium; siphon

Front 20

___________ are filtered from the water by a mucous net and transported by cilia to the esophagus. The anus empties into the excurrent siphon.

Back 20

Food particles

Front 21

Some tunicate species shoot a jet of water through their excurrent sophon when attacked, earning them the name:

Back 21

Sea squirts

Front 22

Lancelets are from the subphylum __________.

Back 22

Cephalochordata

Front 23

They get their name from their blade-like shape.

Back 23

Lancelets

Front 24

Coordinated contraction of muscles serially arranged like rows of _______ along the sides of the notochord flexes the notochord, producing side-to-side undulations that thrust the body forward.

Back 24

Chevrons

Front 25

The lancelet's muscle segments develop from blocks of mesoderm called ________, which are found along each side of the notochord in all chordate embryos.

Back 25

Somites

Front 26

An adult lancelet looks much more like a _____ tunicate then an adult tunicate.

Back 26

Larval

Front 27

Garstang suggested that ancestral tunicate-like chordates accelerated their sexual maturity, becoming mature while still in their larval stage. Thus, they and teh chordates that evolved form them retained the notochord and other features as adults. This process, which has been documented in a number of evolutionary transitions, is known as _______,

Back 27

Paedomorphosis

Front 28

Studies of the ________ gene express suggest that the tunicate larva does not develop the posterior regions of its body axis. Rather, the anterior region is elongated and contains a heart and digestive system.

Back 28

Hox

Front 29

Rather than a full-fledged brain, _____ have only a slightly swollen tip on the anterior end of their dorsal, nerve cord. But the same Hox genes that organize major regions of the forebrain, midbrain, and hindbrain of vertebrates express themselves in a corresponding pattern in this small cluster of cells in the lancelet's nerve cord.

Back 29

Lancelets

Front 30

Humans are chordates, yet they lack most of the main derived characters of chordates. Explain.

Back 30

In humans, these characters are present only in the embryo. The notochord becomes disks between the vertebrae, the tail is almost completely lost, and the pharyngeal clefts develop into various adult structures.

Front 31

How do pharyngeal slits function in feeding in tunicates and lancelets?

Back 31

As water passes through the slits, food particles are filtered from the water and transported to the digestive system.

Front 32

Concept 34.2:

Back 32

Craniates are chordates that have a head

Front 33

Chordates with a head are known as this.

Back 33

Craniates

Front 34

The origin of a head -- consisting of a brain at the anterior end of the dorsal nerve cord, eyes and other sensory organs, and a skull -- opened up a completely new way of feeding for chordates: __________.

Back 34

Active predation

Front 35

On a genetic level, craniates possess ______ clusters of Hox genes (lancelets and tunicates have only one).

Back 35

Two

Front 36

One feature unique to craniates is this.

Back 36

Neural crest

Front 37

A collection of cells that appears near the dorsal margins of the closing neural tube in an embryo.

Back 37

Neural crest

Front 38

Neural crest cells disperse throughout the body, where they give rise to a variety of structures:

Back 38

Including teeth, some of the bones and cartilage of the skull, the inner layer of skin (dermis) of the facial regions, several types of neurons, and the sensory capsules in which eyes and other sense organs develop.

Front 39

The most primitive of the craniate fossils are those of the __________.

Back 39

3-cm long Haikouella, it resembles a lancelet. Its mouth structure indicates that lancelets, it probable was a suspension feeder. Had a small, but well-formed brain, eyes, and muscular segments that resemble those of vertebrates.

Front 40

An example of craniates:

Back 40

Hagfish from Myxini; have a skull made of cartilage, but lack jaws and vertebrate.

Front 41

Which extinct chordate is more closely related to human, Haikouichthys or Haikouella? Explain.

Back 41

Haikouichthys, it had a skull and thus was a craniate, as are humans. Haikouella did not have a skull.

Front 42

What characteristics do hagfishes have that tunicates and lancelets lack?

Back 42

Hagfishes have a head and a skull made of cartilage, plus a small brain, sensory organs, and tooth-like structures. They have a neural crest, gill slits, and more extensive organ systems. In addition, hagfishes have slime glands that ward off predators and may repel competing scavengers.

Front 43

Concept 34.3:

Back 43

Vertebrates are craniates that have a backbone

Front 44

After vertebrates branched off from other craniates, they underwent another duplication, this one involving a group of transcription factor genes called the ________ family.

Back 44

Dlx

Front 45

Lampreys are from the class _________, representing the oldest living lineage of vertebrates.

Back 45

Cephalaspidomorphi

Front 46

Most lampreys are _______ that feed by claiming their round, jawless mouth onto the flank of a live fish.

Back 46

Parasites

Front 47

As larvae, lampreys live in freshwater streams. The larva is a ________________ that resembles a lancelet and spends much of its times buried in sediment.

Back 47

Suspension feeder

Front 48

Lamprey cartilage contains no _______. It is, instead, a stiff protein matrix.

Back 48

Collagen

Front 49

Lampreys also have a cartilaginous pipe around their rodlike _______.

Back 49

Notochord

Front 50

Slender, soft-bodied vertebrates with prominent eyes controlled by numerous muscles. At the anterior end of their mouth, they had a set of barbed hooks made or mineralized dental tissues.

Back 50

Conodonts

Front 51

For conodonts, the food then passed back to the _______, where a different set of dental elements sliced and crushed the food.

Back 51

Pharynx

Front 52

Elements that gave conodonts its name.

Back 52

Coned teeth

Front 53

Vertebrates with additional innovations emerged, had:

Back 53

Paired fins and an inner ear with two semicircular canals that provided a sense of balance. Although they, too, lacked jaws, they had a muscular pharynx, which they may have used in bottom-dwelling organisms or ditritus. Also armored with mineralized bone, which covered varying amount of their body.

Front 54

These armored vertebrates were formed placed in a group called _________.

Back 54

Ostracoderms "shelled skin"

Front 55

The vertebrate skeleton evolved initially as a structure made of ____________.

Back 55

Unmineralized cartilage. Its mineralization began only after lampreys diverged from other vertebrates.

Front 56

What initiated the process of mineralization in vertebrates?

Back 56

Donoghue, from Uni of Birmingham, believe that mineralization was associated with a transition in feeding mechanisms. Early chordates probably were suspension feeders, like lancelets, but over time, they became larger and were therefore able to ingest larger particles, including some small animals.

Front 57

The armor seen in later jawless vertebrates was derived from ________________.

Back 57

Dental mineralization; thus, mineralization of the vertebrate body began in the mouth.

Front 58

How are differences in lamprey and conodont anatomy reflected in each animal's feeding method?

Back 58

Lampreys have a round, rasping mouth, which they use to attach to fish. Conodonts had two sets of mineralized dental elements, which may have been used to impale prey and cut into small pieces.

Front 59

What key roles did mineralized bone play in the first vertebrates?

Back 59

Mineralized dental elements allowed vertebrates to become scavengers and predators. In armored jawless vertebrates, bone served as external defensive armor.

Front 60

Concept 34.4:

Back 60

Gnathostomes are vertebrates that have jaws

Front 61

Named for their jaws, hinged structures that, especially with the help of teeth, enable them to grip food items firmly and slice them up.

Back 61

Gnathostomes "jaw mouth"

Front 62

Gnathostome jaws evolved by modification of the ____________ that had previously supported the anterior pharyngeal slits. The remaining gill slit, no longer required for suspension feeding, remained as the major sites of respiratory gas exchange with the external environment.

Back 62

Skeletal rods

Front 63

The common ancestors of all gnathostomes underwent an additional duplication of _____ genes, such that the single cluster present in early chordates became four.

Back 63

Hox

Front 64

The gnathostome _______ is enlarged compared to that of other craniates, mainly in association with enhanced senses of smell and vision.

Back 64

Forebrain

Front 65

Running the length of each side of the body in aquatic gnathostomes is the ________, a row of microscopic organs sensitive to vibrations in the surrounding water.

Back 65

Lateral line system

Front 66

In the common ancestor of living gnathostomes, the axial skeleton, shoulder girdle, and paired appendages were _______.

Back 66

Mineralized

Front 67

Gnathostome's success probably lies in two features of their anatomy:

Back 67

Their paired fins and tail allowed them to swim efficiently after prey, and their jaws enabled them to grab prey or simply bit off chunks of flesh.

Front 68

Earliest gnathostomes in the fossil record are an extinct linage of armored vertebrates called __________, or plate-skinned.

Back 68

Placoderm

Front 69

Sharks, rays, and their relatives included some of the biggest and most successful vertebrate predators in the oceans. They belong to the class ___________ which means "cartilage fish".

Back 69

Chondrichthyes

Front 70

Chondrichthyans have a skeleton that is composed predominantly of _________, often impregnated with calcium.

Back 70

Cartilage

Front 71

Most sharks have a streamlined body and are swift swimmers, but they do not maneuver very well. Powerful movements of the trunk and the caudal (tail) fin propel them forward. The dorsal fins function mainly as ________, and the paired pectoral (fore) and pelvic (hind) provide lift when a shark swims.

Back 71

Stabilizers

Front 72

Largest sharks and rays are __________ that consume plankton.

Back 72

Suspension feeders

Front 73

A corkscrew-shaped ridge that increases surface area and prolongs the passage of food through the digestive tract.

Back 73

Spiral valve

Front 74

Shark eggs are fertilized _______.

Back 74

Internally

Front 75

Species that lay eggs that hatch outside the mother's body.

Back 75

Oviparous

Front 76

Species that retain the fertilized eggs in the oviduct.

Back 76

Ovoviviparous

Front 77

The young develop within the uterus and obtain nourishment prior to birth by receiving nutrients from the mother's blood through a yolk sac placenta, by absorbing a nutritious fluid produced by the uterus, or by eating other eggs.

Back 77

Viviparous

Front 78

The reproductive tract of the shark empties along with the excretory system and digestive tract into the _______, a common chamber that has a single opening to the outside.

Back 78

Cloaca

Front 79

Most rays are flatted ___________ that feed by using their jaws to crush molluscs and crustaceans.

Back 79

Bottom-dwellers

Front 80

The vast majority of vertebrates belong to a clade of gnathostomes called ________.

Back 80

Osteichthyes "bony fish"

Front 81

Have an ossified (bony) endoskeleton with a hard matrix of calcium phosphate.

Back 81

Osteichthyes

Front 82

Aquatic osteichthyans are the vertebrates we informally call _______.

Back 82

Fishes

Front 83

They breathe by drawing water over four or five pairs of gills located in chambers covered by __________________.

Back 83

Operculum, a protective bony flap

Front 84

Most aquatic osteichthyans can control their buoyancy with an air sac known as __________.

Back 84

Swim bladder

Front 85

The skin of aquatic osteichthyans is often covered by ____________ that differ in structure form the toothlike-scales of sharks.

Back 85

Flattened, bony scales

Front 86

An osteichthyan. Class _________ , ray-finned fishes.

Back 86

Actinopterygii

Front 87

An osteichthyan. Class _________ , lobe-finned fishes.

Back 87

Sarcopteygii

Front 88

Key derived feature of lobe-fins is:

Back 88

The presence of rod-shaped bones surrounded by a thick layer of muscle in their pectoral and pelvic fins.

Front 89

Lineage of lobe-fin that shifted to the ocean.

Back 89

Actinistia

Front 90

Second lineage of lobe-fins represented today by three genera of lungfishes, class ____________, all of which are found in the Southern hemisphere.

Back 90

Dipnoi

Front 91

What derived characteristics do sharks and tuna share? What are some characteristics that distinguish tuna from sharks?

Back 91

Both are gnathostomes and have jaws, four clusters of Hox genes, enlarged forebrains, and lateral line systems. Sharks secondarily lost much mineralization in their skeletons, which consist mainly of cartilage, whereas tuna has bony skeletons. Sharks also have a spiral valve. Tuna have an operculum and a swim bladder, as well as flexible rays supporting their fins.

Front 92

Contrast the habitats of the three surviving lineages of lobe-fins.

Back 92

Coelacanths live in deep marine waters, lungfishes live in ponds and swamps, and terrestrial vertebrates live on land.

Front 93

Concept 34.5:

Back 93

Tetrapods are gnathostomes that have limbs and feet.

Front 94

The fins of some lobe-fins evolved into the limbs and feet of _______.

Back 94

Tetrapods

Front 95

The most significant character of tetrapods:

Back 95

Gives the group its name, which means "four feet" in Greek. In place of pectoral and pelvic fins, tetrapods have limbs that can support their weight on land and feet with digits that allow them to transmit muscle-generated forces to the ground when they walk.

Front 96

Living tetrapods do not have ________; during embryonic development, the pharyngeal clefts instead give rise to parts of the ears, glands, and other structures.

Back 96

Gill slits

Front 97

The tetrapod body plan did not evolve "out of nowhere' but was simply a modification of a _________ body plan.

Back 97

Pre-existing

Front 98

Class ___________ are represented today by about 4,800 species of salamanders, frogs, and caecilians.

Back 98

Amphibians, class Amphibia

Front 99

Class Amphibia, Salamanders are:

Back 99

order Urodela, tailed ones

Front 100

Class Amphibia, Frogs are:

Back 100

order Anura, tail-less ones

Front 101

Class Amphibia, Caechilians are:

Back 101

order Apoda, legless ones

Front 102

_______, the caecilians are legless and nearly blind, and superficially they resemble earthworms. Their absence of legs is a secondary adaptation, as they evolved from a legged ancestor.

Back 102

Apodans

Front 103

Means "two lives" a feference to the metamorphosis of many frog species.

Back 103

Amphibian

Front 104

The larval stage of the frog, _________, is usually an aquatic herbivore with gills, a lateral system resembling that of aquatic vertebrates, and a long, finned tail.

Back 104

Tadpole

Front 105

Fertilization is _______ in most amphibians.

Back 105

External

Front 106

Was Acanthostega a terrestrial tetrapod? Explain.

Back 106

No, though it had four limb-like appendages with fully formed legs, ankles, and digits, its pectoral and pelvic girdles could not carry its body on land. It had gills and a tail fin that propelled it in water.

Front 107

Some amphibians never leave the water, whereas others can survive in relatively dry terrestrial environments. Contrast the adaptations that faciliate these two lifestyles.

Back 107

Some fully aquatic species are paedomorphic, retaining larval features as adults. Species that live in dry environments may avoid dehydration by burrowing or living under moist leaves, and they protect their eggs with foam nests, vivparity, or other adaptations.

Front 108

Concept 34.6:

Back 108

Amniotes are tetrapods that have terrestrially adapted egg.

Front 109

Are a group of tetrapods whose living members are the reptiles, including birds, and the mammals.

Back 109

Aminotes

Front 110

Amniotes are named for the major derived character of the clade, the ____________.

Back 110

Amniotic egg, which contains specialized membranes that protect the embryo, called the extraembryonic membranes

Front 111

Amniotic egg: a disposal sac for certain metabolic wastes produced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ.

Back 111

Allantois

Front 112

Amniotic egg: protects the embryo in a fluid-filled cavity that cushions against mechanical shock.

Back 112

Amnion

Front 113

Amniotic egg: the ______ and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell.

Back 113

Chorion

Front 114

Amniotic egg: Contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored int eh albumen "egg white"

Back 114

Yolk Sac

Front 115

Amniotic eggs of most reptiles and most mammals:

Back 115

Have a shell; the shells of bird eggs are calcareous (made of calcium carbonate) and inflexible, while the shells of many nonbird, reptile eggs are leathery and flexible.

Front 116

The _______ clade includes the tuatara, lizards, snakes, turtles, crocodilians, and birds, along with a number of extinct groups such as the large nonflying dinosaurs.

Back 116

Reptile

Front 117

Unlike amphibians, reptiles have scales that contain _______.

Back 117

Keratin

Front 118

In crocodiles, which have adapted to water, more permeable scaled, called this, have evolved.

Back 118

Scutes

Front 119

Most reptiles rely on their _____ lungs alone for gas exchange.

Back 119

Lungs

Front 120

Many reptiles are sometimes said to be __________ because they do not use their metabolism extensively to control their body structure.

Back 120

Cold-blooded

Front 121

Refers to the absorption of external heat as the main source of body heat.

Back 121

Ectothermic

Front 122

Birds are _______, capable of keeping the body warm through metabolism.

Back 122

Endothermic

Front 123

One of the most obvious derived character of diapsids is:

Back 123

A pair of holes on each side of the skull, behind the eye socket.

Front 124

The diapsids are composed of two main lineages. One lineage gave rise to _________, which include tuatara, lizards, and snakes.

Back 124

Lepidosaurs

Front 125

The other diapsid lineage, the _______, produced the crocodilians, pterosaurs, and dinosaurs.

Back 125

Archosaurs

Front 126

________, originated in the late Triassic period, were the first tetrapods to take to the air.

Back 126

Pterosaurs

Front 127

On land, the _______ diversified into a vast range of shapes and sizes, from bipeds the size of a pigeon to 45-m-long quadrupeds with a neck long enough to let them browse the tops of trees.

Back 127

Dinosaurs

Front 128

One branch of dinosaurs, the ________ were herbivores, they included many species with elaborate defenses against predators, such as tail clubs and horned crests.

Back 128

Ornithischians

Front 129

The other main branch of dinosaurs, the ______ included the long-necked giants and a group called the __________, which were bipedial carnivores.

Back 129

Saurischians; theropods

Front 130

All dinosaurs, except _________, became extinct at the end of the Cretacous period.

Back 130

Birds

Front 131

One lineage of lepidosaurs is represented by two species of lizard-like reptiles called ________.

Back 131

Tuatara

Front 132

All turtles have:

Back 132

A boxlike shell made of upper and lower shields that are fused to the vertebrae, clavicles (collarbones) and ribs.

Front 133

The side-necked turtles are called this, they fold their neck horizontally.

Back 133

Pleurodires

Front 134

The veritcal-necked turtles called this, they fold their necks vertically.

Back 134

Cryptodires

Front 135

Many of the characters of birds are adaptations that facilitate flight, including weight-saving modifications that make flying more efficient:

Back 135

Birds lack urinary bladder, and the females of most species have only one ovary. The gonads of both females and males are usually small, except during the breeding season, when they increase in size. Birds are also toothless, an adaptation that trims the weight of the head.

Front 136

A bird's most obvious adaptations for flight are:

Back 136

Its wings and feathers; feathers are made of a protein called B-keratin that is also found in the scales of other reptiles.

Front 137

The evolution of flight provides numerous benefits. It enhances:

Back 137

hunting and scavenging, many birds consume flying insects, an abundant, highly nutritious food resource.

Front 138

Birds are _______, they use their own metabolic heat to maintain a high, constant body temperature.

Back 138

Endothermic

Front 139

An efficient _________ system and a ________ system with a four-chambered heart keep tissues well supplied with oxygen and nutrients, supporting a high rate of metabolism.

Back 139

Respiratory; circulatory

Front 140

__________ usually involves contact between the mates' vents, the opening to their cloacas. Eggs are shelled when laid, fertilization must be internal.

Back 140

Copulation

Front 141

Archaeopteryx remains the earliest known _________.

Back 141

Bird

Front 142

order Struthioniformes, which consists of the ostrich, rhea, kiwi, cassowary, and emu, are all slightless.

Back 142

Ratites

Front 143

In ratites, "flat-bottomed", the ________ is absent and the pectoral muscles are not greatly enlarged.

Back 143

Sternal keel

Front 144

Penguins make up the flightless order, _____, but like flying birds, they have powerful pectoral muscles, which they use in swimming.

Back 144

Sphenisciformes

Front 145

Defend or refuse the following statement: The amniotic egg of a reptile is a closed system in which the embryo develops in isolation form the outside environment.

Back 145

The amniotic egg is not an entirely closed system. Nutrients used by the embryo are stored within the egg (in the yolk sac and albumen) as are some metabolic wastes produced by the embryo (in the allantois). However, the embryo exchanges oxygen and carbon dioxide with the outside environment via the chorion, allantois, and egg shell.

Front 146

Identify four avian adaptations for flight.

Back 146

Birds have weight-saving modifications, including having no teeth or urinary bladder and only one ovary in females. The wings and feathers are adaptations that facilitate flight, as are efficient respiratory and circulatory systems, which support a high metabolic rate.

Front 147

Concept 34.7:

Back 147

Mammals are amniotes that have hair and produce milk.

Front 148

Derived Characters of Mammals:

Back 148

All mammalian mothers nourish their young with milk, a balanced diet rich in fats, sugars, proteins, minerals, and vitamins. Hair, another mammalian characteristic, and a fat layer under the skin help the body retain heat. Mammals are endothermic and have a high metabolic rate. A sheet of muscle called the diaphragm helps ventilate the lungs.

Front 149

The lining of the uterus and the extraembryonic membranes that arise from the embryo form this:

Back 149

Placenta

Front 150

Found only in Australia and New Guinea, are represented by one species of platypus and two species of echidnas (spiny anteaters). Have hair and produce milk, but they lack nipples. Milk is secreted by glands on the belly of the mother, after hatching, the baby sucks the milk from the mother's fur.

Back 150

Monotremes

Front 151

They have a higher metabolic rate and nipples that provide milk and they give birth to live young. The embryo develops inside the uterus of the female's reproductive tract.

Back 151

Marsupials

Front 152

Commonly called placental mammals because their placentas are more complex than those of marsupials - complete their embryonic development within the uterus, joined to their mother by the placenta.

Back 152

Eutherians

Front 153

Contrast monotremes, marsupials, and eutherians in terms of how they bear young.

Back 153

Monotremes lay eggs. Marsupials give birth to very small live young that remain attached to the mother in a pouch. Eutherians give birth to more developed live young.

Front 154

Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord.

Back 154

Derived characters of chordates: Chordate characters include a notochord, a dorsal hollow nerve chord, pharyngeal slits or clefts, and a muscular, post-anal tail

Front 155

Tunicates: Tunicates are marine suspension feeders commonly called sea squirts. They lose some of the derived characters of chordates as adults.

Back 155

Lancelets: Lancelets are marine suspension feeders that retain the hallmarks of the chordate body plan as adults.

Front 156

Early Chordate Evolution: The current life history of tunicates probably does not reflect that of the ancestral chordate. Gene expression in lancelets holds clues to the evolution of the vertebrate brain.

Back 156

Concept 34.2: Craniates are chordates that have a head.

Front 157

Derived characters of Craniates: Craniates have a head, including a skull, a brain, eyes, an dother sensory organs. Many structures in craniates develop partly from a novel population of cells, the neural crest.

Back 157

The origin of Craniates: Craniates evolved at least 530 MYA, during the Cambrian explosion.

Front 158

Hagfishes: hagfishes are jawless marine craniates that have a cartilaginous skull and an axial rod of cartilage derived from the notochord. They lack vertebrate.

Back 158

Concept 34.3: Vertebrates are craniates that have a backbone.

Front 159

Derived Characters of Vertebrates: Vertebrates have vertebrate, an elaborate skull, and, in aquatic forms, fin rays.

Back 159

Lampreys: Lampreys are jawless vertebrates that have cartilaginous segments surrounding the notochord and arching partly over the nerve cord.

Front 160

Fossils of Early Vertebrates: Conodonts were the first vertebrates with mineralized skeletal elements in their mouth and pharynx. Armored jawless vertebrates "ostracoderms" had defensive plates of bone on their skin.

Back 160

Origins of Bone and Teeth: Mineralization appears to have orginated with vertebrate mouthparts; the vertebrate endoskeleton became fully mineralized much later.

Front 161

Concept 34.4: Gnathostomes are vertebrates that have jaws.

Back 161

Derived Characters of Gnathostomes: Gnathostomes have jaws, which evolved form skeletal supports of the pharyngeal slits; enhanced sensory systems, including the lateral line system; an extenstively mineralized endoskeleton, and paired appendages.

Front 162

Fossil Gnathostomes: Placoderms were close relatives of living gnathostomes. Acanthodians were closely related to osteichthyans.

Back 162

Chondrichthyans (sharks, rays, and their relatives): Chondrichthyans, which includes sharks and rays, have a cartilaginous skeleton that evolved secondarily from an ancestral mineralized skeleton.

Front 163

Ray-Finned Fishes and Lobe-fins: Osteichthyans have a skeleton reinforced by calcium phosphate. Aquatic forms have bony gill covers and a swim bldder; some also have lungs. Ray-finned fishes have maneuverable fins supported by long rays. Lobe-fins include coelacanths, lungfishes, and tetrapods. Aquatic lobe-fins have muscular pectoral and pelvic fins.

Back 163

Concept 34.5: Tetrapods are gnathostomes that have limbs and feet.

Front 164

Derived Characters of Tetrapods: Tetrapods have four limbs and feet with digits. They also have other adaptations for life on land, such as ears.

Back 164

The Origin of tetrapods: Fossil evidence suggests that tetrapod limbs, now mainly used for walking on land, were originally used for paddling in water.

Front 165

Amphibians: Amphibians include salamanders, frogs, and caecilians. Most have moist skin that complements the lungs in gas exchange. Most frogs and some salamanders undergo metamorphosis of an aquatic larva into a terrestrial adult.

Back 165

Concept 34.6: Amniotes are tetrapods that have a terrestrially adapted egg.

Front 166

Derived Characters of Amniotes: The amniotic egg contains extraembryonic membranes that carry out a variety of functions, including gas exchange and protection. Amniotes also have other terrestrial adaptations, such as relatively impermeable skin.

Back 166

Early Amniotes: Early amniotes appeared in the Carboniferous period. They included large herbivores and predators.

Front 167

Reptiles: Reptiles include tuatara, lizards, snakes, turtles, crocodilians, and birds. Extinct forms include parareptiles, most dinosaurs, pterosaurs, and marine reptiles. Most reptles are ectothermic, althought birds are endothermic.

Back 167

Birds: Birds probably descended form a group of small, carnivorous dinosaurs known as theropods. They have a variety of adaptations well suited to a lifestyle involving flight.

Front 168

Concept 34.7: Mammals are amniotes that have hair and produce milk.

Back 168

Derived Characters of Mammals: Hair and mammary glands are two derived characteristics.

Front 169

Monotremes: small group of egg-laying mammals consisting of echidnas and the platypus.

Back 169

Marsupials: Include opossums, kangaroos, and koalas. Marsupial young begin their embryonic development attached to a placenta in the mother's uterus but complete development inside a maternal pouch.

Front 170

Eutherians (Placental mammals): Eutherians have young that complete their embryonic development attached to a placenta.

Back 170

Early evolution of Mammals: Mammals evolved from synapsids in the late Triassic period. Living lineages of mammals originated in the Jurassic but did not undergo a significant adaptive radiation until the beginning of the Paleogene.

Front 171

Concept 35.1:

Back 171

The plant body has a hierarchy of organs, tissues, and cells

Front 172

An organism's ability to alter or "mold" itself in response to local environmental conditions.

Back 172

Plasticity

Front 173

External form

Back 173

Morphology

Front 174

A group of cells with a common function, structure, or both.

Back 174

Tissue

Front 175

Consists of several types of tissues that together carry out particular functions.

Back 175

Organ

Front 176

Pants must absorb water and minerals form below the ground and CO2 and light ______ above the ground.

Back 176

Above

Front 177

The evolutionary solution to this separation of resources was the development of three basic organs:

Back 177

Roots, stems, and leaves

Front 178

They are organized into a ____ system and a ______ system, the latter consisting of stems and leaves.

Back 178

Root; shoots

Front 179

_______ are typically nonphotosynthetic and would starve without the organic nutrients imported from the shoot system. Conversely, the shoot system depends on the water and minerals that roots absorb from the soil.

Back 179

Roots

Front 180

An organ that anchors a vascular plant (usually in the soil), absorbs minerals and water, and often stores organic nutrients.

Back 180

Root

Front 181

Consisting of one main vertical root (the taproot) that develops from an embryonic root.

Back 181

Taproot

Front 182

Taproot gives rise to _______, also called branch roots.

Back 182

Lateral roots

Front 183

A mat of generally thin roots spreading out below the soil surface, with no root standing out as the main one.

Back 183

Fibrous root system

Front 184

Term describing any plant part that grows in an unusual location.

Back 184

Adventitious

Front 185

An extension of a root epidermal cell (protective cell on a plant surface)

Back 185

Root hair

Front 186

Modified roots: The aerial roots shown in maize are examples of this, so named because they support tall, top-heavy plants. All roots of a mature maize plant are adventitious after the original roots die. The emerging roots shown will eventually penetrate soil.

Back 186

Prop roots

Front 187

Modified roots: Many plants, such as sweet potatoes, store water and food in their roots.

Back 187

Storage roots

Front 188

Modified roots: The seeds of a strangler fig germinate in the branches of tall trees and send numerous aerial roots to the ground. These snake-like roots gradually wrap around the hosts and objects. Eventually, the host tree dies of strangulation and shading.

Back 188

Strangling, aerial roots

Front 189

Modified roots: Aerial roots that look like buttresses support the tall trunks of some tropical trees, such as a ceiba tree in Central America.

Back 189

Buttress roots

Front 190

Modified roots: Also known as air roots, this is produced by trees such as mangrove that inhabit tidal swamps. By projecting above the surface, they enable the root system to obtain oxygen, which is lacking in the thick, waterlogged mud.

Back 190

Pneumatophores

Front 191

An organ consisting of an alternating system of nodes and internodes.

Back 191

Stem

Front 192

Point at which leaves are attached to stem.

Back 192

Node

Front 193

The stem segments between nodes.

Back 193

Internodes

Front 194

A structure that has the potential to form a lateral shoot, commonly called a branch.

Back 194

Auxillary bud

Front 195

Concentrated near the shoot apex (tip), consists of this with developing leaves and compact series of nodes and internodes.

Back 195

Terminal bud

Front 196

The proximity of the terminal bud is partly responsible for inhibiting the growth of axillary buds, a phenomenon called this.

Back 196

Apical dominance

Front 197

The main photosynthetic organ of most vascular plants, although green stems also perform photosynthesis.

Back 197

Leaf

Front 198

Leavs consists of this flattened _________ and a stalk, the __________, which joins the leaf to a node of the stem.

Back 198

Blade; petiole

Front 199

Monocots and eudicots differ in the arrangement of ____, the vascular tissue of leaves. Most monocots have major these that run the length of the leaf blade, while eudicots have a multibranched network.

Back 199

Veins

Front 200

Leaves: A single, undivided blade. Some are deeply lobed, as in an oak leaf.

Back 200

Simple leaf

Front 201

Leaves: The blade consists of multiple leaflets. Notice that a leaflet has no axillary bud at its base.

Back 201

Compound leaf

Front 202

Leaves: Each leaflet is divided into smaller leaflets.

Back 202

Double compound leaf

Front 203

Modified leaves: This is by which the pea plant clings to a support. After it's "lassoed" a support, this forms a coil that brings the plant closer to the support. Typically modified leaves, but some are modified stems, as in grapevines.

Back 203

Tendrils

Front 204

Modified leaves: This of cacti, such as the prickly pear, are actually leaves, and photosynthesis is carried mainly by the fleshy green stems.

Back 204

Spines

Front 205

Modified leaves: Most succulents, such as this ice plant, have leaves modified for storing water.

Back 205

Storage leaves

Front 206

Modified leaves: Red parts of the poinsettia are often mistaken for petals but are actually modified leaves called bracts that surround a group of flowers.

Back 206

Bracts

Front 207

Modified leaves: the leaves of some succulents such as the kalanchoe daigremontiana produce adventitious plantlets, which fall off leaf and take root in the soil.

Back 207

Reproductive leaves

Front 208

Consists of one of more tissues organized into a functional unit connective the organs of a plant.

Back 208

Tissue system

Front 209

Outer, protective covering.

Back 209

Dermal tissue system

Front 210

In nonwoody plants, the dermal tissue usually consists of a single layer of tightly packed cells called this _____.

Back 210

Epidermis

Front 211

In wood plants, protective tissues known as this replace the epidermis in older regions of stems and roots by a certain process.

Back 211

Periderm

Front 212

In the epidermis of leaves and most stems, a waxy coating called this helps prevent water loss - an important adaptation to living on land.

Back 212

Cuticle

Front 213

Outgrowths of the epidermis, are yet another example of specialization.

Back 213

Leaf trichomes

Front 214

Carries out long-distance transport of materials between roots and shoots.

Back 214

Vascular tissue system

Front 215

Conveys water and dissolved minerals upward from roots into the shoots.

Back 215

Xylem

Front 216

Transports organic nutrients such as sugars form where they are made (usually leaves) to where they are needed (usually roots and sites of growth).

Back 216

Phloem

Front 217

The vascular tissue of a root or stem is collectively called the _________.

Back 217

Stele

Front 218

In angiosperms, the stele of the root in in the form of a solid, central:

Back 218

Vascular cylinder

Front 219

The stele of stems and leaves is divided into ____________, strands consisting of xylem and phloem.

Back 219

Vascular bundles

Front 220

Tissues that are neither dermal nor vascular are part of this system.

Back 220

Ground tissue

Front 221

Ground tissue that is internal to the vascular tissue is called:

Back 221

Pith

Front 222

Ground tissue that is external to the vascular tissue is called:

Back 222

Cortex

Front 223

The cell contents exclusive of the cell wall.

Back 223

Protoplast

Front 224

How does the vascular tissue system enable leaves and roots to combine functions to support growth and development of the whole plant?

Back 224

The vascular tissue system connects leaves and roots, allowing sugars to move from leaves to roots in the phloem, and allowing water and minerals to move to the leaves in the xylem.

Front 225

Describe at least three specializations in plant organs and plant cells that are adaptations to life on land.

Back 225

Here are a few examples: The tubular, hollow structures of the tracheids and vessel elements of the xylem and the sieve plates in the sieve-tube members of the phloem facilitate transport. Root hairs aid in absorption of water and nutrients. The cuticle in leaves and stems protects from dessiccation and pathogens. Leaf trichomes protect from herbivores and pathogens. Collenchyma and schlerenchyma cells have thick walls that provide support for plants.

Front 226

Describe the role of each tissue system in a leaf.

Back 226

The dermal tissue system is the leaf's protective covering. The vascular tissue system consists of the transport tissues xylem and phloem. The ground tissue system performs metabolic functions such as photosynthesis.

Front 227

Have primary walls that are relatively thin and flexible, and most lack secondary walls. Often depicted as "typical" plant cells because they appear to be the least specialized structurally. Perform most of the metabolic functions of the plant, synthesizing and storing various organic products. Most retain the ability to divide and differentiate into other types of plant cells under special conditions.

Back 227

Parenchyma cells

Front 228

Grouped in strands or cylinders, help support young parts of the plant shoot. Have thicker primary walls than parenchyma cells, though the wall are unevenly thickened. Lack secondary walls, and the hardening agent lignin is absent in their primary walls, therefore provide flexible support without restraining growth.

Back 228

Collenchyma cells

Front 229

Also functioning as support, but with thick secondary walls usually strengthened by lignin. Two types of this called schlereids and fibers. Sclereids are shorter than fibers and irregular shaped, have very thick lignified secondary walls. Fibers are long, slendered, and tapered.

Back 229

Sclerenchyma cells

Front 230

Two types of this, tracheids and vessel elements. Are tubular, elongated cells that are dead at functional maturity. Tracheids found in xylem of all vascular plants. Trachieds are long, thin cells with tapered ends. Water moved form cell to cell mainly through the pits, where it does not have to cross thick secondary walls. Vessel elements are generally wider, shorter, thinner walled, and less tapered than tracheids. Are aligned end to end, forming long micropipes known as vessels.

Back 230

Water-conducting cells of the xylem

Front 231

This of the phloem are alive at functional maturity. In the phloem of angiosperms, these nutrients are transported through sieve tubes, which consists of chains of cells called sieve-tube members.

The end walls between sieve-tube members, called sieve plates, have pores that facilitate the flow of fluid from cell to cell along the tube. Alongside each sieve-tube member is a nonconducting cell called the companion cell, which is connected tot eh member by numerous channels, the plasmodesmata.

Back 231

Sugar-conducting cells of the phloem

Front 232

Concept 35.2:

Back 232

Meristems generate cells for new organs

Front 233

Growth occurs throughout a plant's life, condition called:

Back 233

Indeterminate growth

Front 234

Most animal and some plant organs, such as most leaves, under go this, that is, they cease growing after reaching a certain size.

Back 234

Determinate growth

Front 235

Complete their lifecycle - from germination to flowering to seed production to death - in a single year or less.

Back 235

Annuals

Front 236

Generally live two years, often including an intervening cold period (winter) between vegetative growth (first spring/summer) and flowering (second spring/summer)

Back 236

Biennials

Front 237

Live many years and include trees, shrubs, and some grasses.

Back 237

Perrennials

Front 238

Plants are capable of interdeterminate growth becase they have perpetually embryonic tissues called:

Back 238

Meristems

Front 239

Apical meristems, located at the tips of roots and in the buds of shoots, provide additional cells that enable the plant to grow length, a process called:

Back 239

Primary growth

Front 240

In ________ (nonwoody) plants, primary growth produces all, or almost all, of the plant body.

Back 240

Herbaceous

Front 241

This growth in thickness, called this: is caused by the activity of lateral meristems called the vascular cambium and cork cambium.

Back 241

Secondary growth

Front 242

This adds layers of vascular tissue called secondary xylem (wood) and secondary phloem.

Back 242

Vascular cambium

Front 243

This replaces the epidermis with periderm, which is thicker and tougher.

Back 243

Cork cambium

Front 244

Cells that remain as sources of new cells are called:

Back 244

Initials

Front 245

The new cells displaced from the meristem called ________, continue to divide until the cells they produce become specialized within developing tissues.

Back 245

Derivatives

Front 246

Primary growth in stems: layers.

Back 246

Pith
Primary Xylem
Primary Phloem
Cortex
Epidermis

Front 247

Secondary growth in stems: layers.

Back 247

Pith
Primary Xylem
Secondary Xylem
Vascular Cambium
Secondary Phloem
Primary Phloem
Cortex
Cork Cambium
Periderm

Front 248

This adds secondary dermal tissue.

Back 248

Cork Cambium

Front 249

This adds secondary xylem and phloem.

Back 249

Vascular Cambium

Front 250

Cells in lower layers of your skin divide and replace dead cells sloughed from the surface. Why is it inaccurate to compare such regions of cell division to a plant meristem?

Back 250

Your dividing cells are normally limited in the types of cells that can form. In contrast, the products of cell division in a plant meristem differentiate into all the diverse types of plant cells.

Front 251

Contrast the types of growth arising from apical and lateral meristems.

Back 251

Primary growth arises from apical meristems and involves the production and elongation of organs. Secondary growth arises form lateral meristems and adds to the girth of roots and stems.

Front 252

Concept 35.3:

Back 252

Primary growth lengthens roots and shoots

Front 253

Primary growth produces this, the parts of the root and shoot systems produced by apical meristems.

Back 253

Primary plant body

Front 254

The root tip is covered by a thimble-like _______, which protects the delicate apical meristem as the root pushes through the abrasive soil during primary growth. It also secretes a polysaccharide slime that lubricates the soil around the root up.

Back 254

Root cap

Front 255

This zone includes the root apical meristem and its derivatives.

Back 255

Zone of cell division

Front 256

This zone, root cells elongate, sometimes to more than ten times their original length.

Back 256

Zone of elongation

Front 257

This zone, cells complete their differeniation and become functionally mature.

Back 257

Zone of maturation

Front 258

The innermost layer of the cortex is called __________, a cylinder one cell thick that forms the boundary with the vascular cylinder.

Back 258

Endodermis

Front 259

Lateral roots arise from this, the outermost cell layer in the vascular cylinder.

Back 259

Pericycle

Front 260

A shoot apical meristem is a dome-shaped mass of dividing cells at the tip of the terminal bud. Leaves arise as ___________, finger like projections along the flanks of the apical meristem.

Back 260

Leaf primordia

Front 261

Lateral roots arise from:

Back 261

Vascular tissue within a root

Front 262

Lateral shoots arise from:

Back 262

Preexisting axillary buds on the surface of a stem

Front 263

The epidermal barrier interrupted by the _______, which allows CO2 exchange between the surrounding air and the photosynthetic cells inside the leaf.

Back 263

Stomata

Front 264

The stomama refers to the stomatal pore or to the entire stomatal complex consisting of a pore flanked by two ___________, which regulate the opening and closing of the pore.

Back 264

Guard cells

Front 265

The ground tissue is sandwiched between the upper and lower epidermis, a region called:

Back 265

Mesophyll

Front 266

Palisade parenchyma, consists of one or more layers of elongated cells on the upper part of the leaf.

Back 266

Palisade mesophyll

Front 267

Also called spongy parenchyma is below the palisade mesophyll.

Back 267

Spongy mesophyll

Front 268

Connections from vascular bundles in the stem, pass through petioles and into leaves. Veins are the leaf's vascular bundles, which subdivide repeatedly and branch throughout the mesophyll.

Back 268

Leaf traces

Front 269

Each vein is enclosed by a protective ________________, consisting of one or more layers of cells, usually parenchyma cells.

Back 269

Bundle sheath

Front 270

Describe how roots and shoots differ in their branching.

Back 270

Lateral roots emergy from the root's interior (from the pericycle), pushing through cortical and epidermal cells. In contrast, shoot branches arise on the exterior of a shoot (from auxillary buds).

Front 271

Contrast primary growth in roots and shoots.

Back 271

In roots, primary growth occurs in three successive stages, moving away from the root tip: the zones of cell division, elongation, and maturation. In shoots, it occurs at the tip of terminal buds, with leaf primordia arising along the sides of apical meristems. Most growth in length occurs in older internodes belong the shoot apex.

Front 272

Describe the functions of the leaf veins.

Back 272

Veins are a network of vascular tissue that provides water and minerals to leaf cells and carries organic products of photosynthesis to other parts of the plant.

Front 273

Concept 35.4:

Back 273

Secondary growth adds girth to stems and roots in woody plants

Front 274

The growth in thickness produced by lateral meristems, occurs in stems and roots of woody plants, but rarely in leaves.

Back 274

Secondary growth

Front 275

Consists of the tissues produced by the vascular cambium and cork cambium.

Back 275

Secondary plant body

Front 276

Cylinder of meristematic cells one cell thick. It increases and also lays down succesive layers of secondary xylem to its interior and secondary phloem to its exterior, each layer with a larger diameter than the previous layer.

Back 276

Vascular cambium

Front 277

Layers of leaves.

Back 277

Upper epidermis
Palisade mesophyll
Spongy mesophyll
Lower epidermis

Front 278

Primary and secondary growth of a stem. Layers.

Back 278

Epidermis
Cortex
Primary phloem
Vascular cambium
Primary xylem
Pith


Periderm (mainly cork cambia and cork)
Primary phloem
Secondary phloem
Vascular cambium
Secondary xylem
Primary xylem
Pith

Front 279

Primary and secondary growth of stem. Steps.

Back 279

1. In the youngest part of the stem, you can see the primary plant body, as formed by the apical meristem during primary growth. The vascular cambium is beginning to develop.

2. As primary growth continues to elongate the stem, the portion of the stem formed earlier in the same year has already started its secondary growth. This portion increases in girth as fusiform initials of the vascular cambium form secondary xylem to the inside and secondary phloem to the outside.

3. The ray initials of the vascular cambium give rise to the xylem and phloem rays.

4. As the diameter of the vascular cam. increases, the second phloem and other tissues external to the cam. cannot keep pace with the expansion b/c the cells no longer divide. As a result, these tissues, including the epidermis, rupture. A second lateral meristem, the cork cam., develops from parenchyma cells in the cortex. The cork cam. produces cork cells, which replace the epidermis.

5. In year 2 of sec. growth, the vascular cambium adds to the sec. xylem and phloem, and the cork cambium produces cork.

6. As the diameter of the stem continues to increase, the outermost tissues exterior to the cork cam rupture and slough off the stem.

7. Cork cam reforms in progressively deeper layers of the cortex. When none of the original cortex is left, the cork cambium develops from parenchyma cells in the sec. phloem.

8. Each cork cambium and the tissues it produces form a layer of periderm.

9. Bark consists of all tissues exterior to the vas. cam.

Front 280

Produce elongated cells such as the tracheids, vessel elements, and fibers of the xylem, as well as the sieve-tube members, companion cells, parenchyma, and fibers of the phloem.

Back 280

Fusiform initials

Front 281

Shorter and oriented perpendicular to the stem or root axis, produce vascular rays - radial files consisting mainly of parenchyma cells.

Back 281

Ray initials

Front 282

The portion of vascular ray located in the sec. xylem is:

Back 282

Xylem ray

Front 283

The portion located in the sec. phloem is:

Back 283

Phloem ray

Front 284

As tree or woody shrub ages, the older layers of sec. xylem no longer transport water and minerals (xylem sap), these layers are called ___________, b/c they are closer to the center of the stem or root.

Back 284

Heartwood

Front 285

The outer layers still transport zylem sap and there are:

Back 285

Sapwood

Front 286

Generally darker than sapwood b/c of resins and other compounds that clog the cell cavities and help protect the core of the tree from fungi and wood-boring insects.

Back 286

Heartwood

Front 287

Only the ________ sec. phloem, closest to the vas. cam., functions in sugar transport.

Back 287

Youngest

Front 288

Anatomy of a tree trunk:

Back 288

From center to exterior:

Sec. xylem:
Heartwood
Sapwood

Growth ring
Vascular ray

Vascular cambium

Bark:
Secondary phloem
Layers of periderm

Front 289

Dotting the periderm are small raise areas called this, in which there is more space between the cork cells, enabling living cells within a woody stem or root to exchange gases with the outside air.

Back 289

Lenticels

Front 290

Includes all tissues external to the vascular cambium.

Back 290

Bark

Front 291

A sign is hammered into a tree 2 m from the tree's base. If the tree is 10 m tall and elongates 1 m each year, how high will the sign be after 10 years?

Back 291

The sign will still be 2 m above the ground because only secondary growth occurs in this part of the tree.

Front 292

A tree can survive even if a tunnel is cut through its center. However, removing a complete ring of bark around the tree (a process called girdling) will kill the tree. Explain why.

Back 292

A hollow tree can survive because water, minerals, and organic nutrients are conducted by the younger secondary vascular tissues, some of which remain intact: the outer secondary xylem (sapwood) and youngest secondary phloem. However, girdling removes an entire ring of secondary phloem (part of the bark), completely preventing transport of organic nutrients from the shoots to the roots.

Front 293

Concept 35.1: The plant body has a hierarchy of organs, tissues, and cells.

Back 293

The three basic plant organs: Roots, stems, and leaves.

Roots anchor the plant, absorb and conduct water and minerals, and store food. The shoot system consists of stems, leaves, and (in angiosperms) flowers. Leaves are attached by their petioles to the nodes of the stem, with internodes of the stem separating the nodes. Axillary buds, located in the axils of petioles and stems, have the potential to extend as vegetative or floral shoots. The two main groups of angiosperms, monocots, and eudicots, differ in anatomical details.

Front 294

The three tissue systems: dermal, vascular, and ground.

Dermal tissue (epidermis and periderm), vascular tissue (xylem and phloem), and ground tissue are continuous throughout the plant, although in the various plant organs the three tissues differ in arrangement and in some specialized functions. Vascular tissues integrate the parts of the plant. Water and minerals move up from roots in the xylem. Sugar is exported from leaves or storage organs in the phloem.

Back 294

Common Types of Plant cells.

Parenchyma cells, relatively unspecialized cells that retain the ability to divide, perform most of the plant's metabolic functions of synthesis and storage.

Collenchyma cells, which have unevenly thickened walls, support young, growing parts of the plant.

Schlerenchyma cells - fibers and sclereids - have thick, lignified walls that help support mature nongrowing parts of the palnt. Tracheids and vessel elements, the water-conducting cells of xylem, have thick walls and are dead at functional maturity. Sieve-tube members are the sugar-transporting cells of phloem in angiosperms. Though alive at functional maturity, sieve-tube members depend on the services of neighboring companion cells.

Front 295

Concept 35.2: Meristems generate cells for new organs.

Back 295

Apical meristems elongate shoots and roots through primary growth. Lateral meristems add girth to woody plants through secondary growth.

Front 296

Concept 35.3: Primary growth lengthens roots and shoots.

Back 296

Primary growth of roots: Apical meristems produce cells that continue to divide as meristematic cells. In roots, the apical meristem is located near the tip, where it generates the root cap.

Front 297

Primary growth of shoots: The apical meristem of a shoot is located in the terminal bud, where it gives rise to a repetition of internodes and leaf-bearing nodes.

Back 297

Concept 35.4: Secondary growth adds girth to stems and roots in woody plants.

Front 298

The Vascular Cambium and Secondary Vascular Tissue:

The vascular cambium develops form parencyma cells into a meristematic cylinder that produces secondary xylem and secondary phloem. Older layers of secondary xylem (heartwood) become inactive, while younger secondary phloem is active in conducting organic nutrients.

Back 298

Cork Cambia and the Production of Periderm:

The cork cambium gives rise to the secondary plant body's protective covering, or periderm, which consists of the cork cambium plus the layers of cork cells it produces. Bark consists of all the tissues external to the vascular cambium: secondary phloem and periderm.

Front 299

Concept 36.1:

Back 299

Physical forces drive the transport of materials in plants over a range of distances.

Front 300

________ transports water and minerals from roots to shoots. _______ transports sugars from where they are produced or stored to where they are needed for growth an metabolism.

Back 300

Xylem; phloem

Front 301

Transport in vascular plants occurs in three scales:

Back 301

1. Transport of water and solutes by individual cells, such as hairs

2. Short-distance transport of substances from cell to cell at the levels of tissues and organs, such as the loading of sugar from photosynthetic leaf cells into the sieve tubes of the phloem.

3. Long-distance transport within xylem and phloem at the level of the whole plant.

Front 302

Solutes tend to diffuse down their gradients and that diffusion across a membrane is called:

Back 302

Passive transport

Front 303

The pumping of solutes across membranes against their electrochemical gradients, the combined effects of the concentration gradient of the solute and the voltage (charge difference) across the membrane.

Back 303

Active transport

Front 304

Most solutes cannot cross the lipid bilayer of the membrane; they must pass through this embedded in the membrane.

Back 304

Transport proteins

Front 305

The most important active transport protein in the plasma membranes of plant cells is this, which uses energy from ATP to pump hydrogen ion (H+) out of the cell.

Back 305

Proton pump

Front 306

An overview of transport in a vascular plant:

Back 306

1. Roots absorb water and dissolved minerals from the soil

2. Water and minerals are transported upward from roots to shoots as xylem sap

3. Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward

4. Through stomata, leaves take CO2 and expel O2. The CO2 provides carbon for photosynthesis. Some O2 produced by photosynthesis is used in cellular respiration.

5. Sugars are produced by photosynthesis in the leaves.

6. Sugars are transported as phloem sap to roots and other parts of the plant.

7. Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars.

Front 307

Proton pumps provide energy for solute transport.

Back 307

By pumping H+ out of the cell, proton pumps produce an H+ gradient and a charge separation called a membrane potential. These two forms of potential energy can be used to drive the transport of solutes.

Front 308

In this mechanism, a transport protein couples the downhill passage of one solute (H+) to the uphill passage of another (NO3-).

Back 308

Cotransport

Front 309

The combined effects of solute concentration and physical pressure are incorporated into a measurement called:

Back 309

Water potential

Front 310

Plant biologists measure in unit pressure called:

Back 310

Megapascals

Front 311

This of a solute is proportional to the number of dissolved solute molecules. Solute potential is also called this because solutes affect the direction of osmosis.

Back 311

Solute potential; osmotic potential

Front 312

The physical pressure on a solution.

Back 312

Pressure potential

Front 313

The cell contents press the plasma membrane against the cell wall, producing this.

Back 313

Turgor pressure

Front 314

Water moves:

Back 314

in the direction of higher to lower water potential, and of lower to higher solute potential.

Front 315

Three major compartments of vacuolated plant cells:

Back 315

The cell wall, cytosol, and vacuole are the three main.

Front 316

Plasmodesmata connect the cytosolic compartments of neighboring cells, thereby forming a continuous pathway for transport of certain molecules between cells. THis cytoplasmic continuum is called the:

Back 316

Symplast - continuum of cytosol connected by plasmodesmata

Front 317

The continuum of cell walls plus the extracellular spaces is called the:

Back 317

Apoplast - continuum of cell walls and extracellular spaces

Front 318

Long distance transport occurs through _________, the movement of a fluid driven by pressure. In this, water and solutes move through the tracheids and vessels of the xylem and through the sieve tubes of the phloem.

Back 318

Bulk flowe

Front 319

Some farmers throughout the work irrigate crops using groundwater, which has a relatively high content of dissolved salts. How might this practice affect water uptake in crops?

Back 319

The relatively high concentration of salts might cause the soil's water potential to be more negative, thereby reducing water uptake by lowering the water potential gradient from the soil to the roots.

Front 320

If a plant cell immersed in distilled water has a Ws of -0.7MPa and a W of 0Mpa, what is the cell's Wp? If you put the same cell in an open beaker of solution that as a W of -0.4Wpa, what would be the cell's Wp at equilibrium?

Back 320

The cell's Wp is 0.7Mpa. In a solution with a W of -0.4Mpa, the cell's Wp at equilibrium would be 0.3Mpa

Front 321

Concept 36.2:

Back 321

Roots absorb water and minerals from the soil

Front 322

Roots and fungi form this, symbiotic structures consisting of plant roots united with fungal hyphae filaments.

Back 322

Mycorrhizae

Front 323

The innermost layer of cells in the root cortex, surround the vascular cylinder and functions as a last checkpoint for the selective passage of minerals form the cortex into the vascular tissue.

Back 323

Endodermis

Front 324

Lateral transport of minerals and water in roots:

Back 324

1. Uptake of soil solutions by the hydrophilic walls of root hairs provides access to the apoplast. Water and minerals can then soak into the cortex along this matrix of walls.

2. Minerals and water that cross the plasma membranes of root hairs enter the symplast.

3. As soil solution moves along the apoplast, some water and minerals are transported into the protoplasts of cells of the epidermis and cortex and then move inward via the symplast.

4. Within the transverse and radial walls of each endodermal cell is the Casparian strip, a belt of waxy material (purple band) that blocks the passage of water pathway by crossing the plasma membrane of an endodermal cell can detour around the Casparian strip and pass into the vascular cylinder.

5. Endodermal cells and also parenchyma cells within the vascular cylinder discharge water and minerals into their walls (apoplast). The xylem vessels transport the water and minerals upward into the shoot system.

Front 325

Why might a crop develop a severe phosphate deficiency after being sprayed with a fungicide?

Back 325

The fungicide may kill the mycorrhizal fungi that function in phosphate uptake.

Front 326

A scientist adds a water-soluable inhibitor of photosynthesis to the roots of a plant. However, photosynthesis is not affected by addition of the inhibitor in this manner. Why?

Back 326

The endodermis regulate the passage of water-soluable solutes by requiring all such molecules to cross a selectively permeable membrane.

Front 327

Concept 36.3:

Back 327

Water and minerals ascend from roots and shoots through the xylem

Front 328

Plants lose an astonishing amount of water by _________, the loss of water vapor from leaves and other aerial parts of the plant.

Back 328

Transpiration

Front 329

Water flows in from the root cortex, generating this, an upward push of xylem sap.

Back 329

Root pressure

Front 330

The root pressure sometimes causes more water to enter the leaves than is transpired, resulting in this, the exudation of water droplets that can be seek in the morning on tips of grass blades or the leaf margins of some small, herbaceous eudicots.

Back 330

Guttation

Front 331

The generation of transpirational pull in a leaf. The negative pressure at the air-water interface int he leaf is the physical basis of transpirational pull, which draws water out of the xylem.

Back 331

1. In transpiration, water vapor (shown as blue dots) diffuses from the moist air spaces of the leaf to the drier air outside via stomata.

2. At first, the water vapor lost by transpiration is replaced by evaporation from the water film that coats mesophyll cells.

3. Evaporation causes the air-water interface to retreat farther nto the cell wall and become more curved as the rate of transpiration increase. As the interface beocmes more curved, the water film's pressure becomes more negative. This negative pressure, or tension, pulls water from the xylem, where the pressure is greater.

Front 332

Ascent of xylem sap:

Back 332

Hydrogen bonding forms an unbroken chain of water molecules extending from leaves all the way to the soil. The force that drives the ascent of xylem sap is a gradient of water potential. For the bulk flow over long distance, the water potential gradient is due mainly to a gradient of the pressure potential. Transpiration results in the pressure potential at the leaf end of the xylem being lower then the pressure potential at the root end. The water potential values showen at the left at a snapshot. During daylight, these specific values may vary, but the direct of the water potential gradient remains the same.

Outside side water potential:
-100.00Mpa

Leaf water potential (air spaces):
-7.0Mpa

Leaf water potential (cell walls):
-1.0Mpa

Trunk xylem water potential:
-0.8Mpa

Root xylem water potential:
-0.6Mpa

Soil water potential:
-0.3Mpa

Front 333

What would be the effect of fertilizing a plant during a drought?

Back 333

By lowering the solute potential (and water potential) of the soil, the fertilizer would make it harder for the plant to absorb water.

Front 334

Plants called ephiphytes, including many orchid species, live in the very humid tropics and grow on tree trunks. Epiphytes have no contact with the soil but can absorb water from the air. How is this possible?

Back 334

The humid air has higher water potential than the leaves.

Front 335

A tip for helping cut flowers last longer without wilting is to cut off the ends of the stems underwater and then transfer the flowrs to a vase while water droplets are still present on the cut ends of the stems. Explain why this works.

Back 335

After the flowers are cut, transpiration from any leaves and from the petals (which are modified leaves) will continue to draw water up the xylem. If cut flowers are transferred directly to a vase, air pockets in xylem vessels prevent delivery of water from the vase to the flowers. Cutting stems again underwater, a few cm from the original cut, will sever the xylem above the air pockets. The water droplets prevent other air pockets from forming while the flowers are transferred to a vase.

Front 336

Concept 36.4:

Back 336

Stomata help regulate the rate of transpiration

Front 337

The mechanism of stomatal opening and closing:

Back 337

(a) Changes in guard cell shape and stomatal opening and closing: Guard cells of a typical angiosperm are illustrated in their turgid (stoma open) and flaccid (stoma closed) states. The pair of guard cells buckle outward when turgid. Cellulose microfibrils in the walls resist stretching and compression in the direction parallel to the cells to increase in length more than width when turgor increases. The two guard cells are attached at their tips, so the increase in length causes buckling.

(b) Role of potassium in stomatal opening and closing. The transport of K+ (potassium ions, symbolized here as red dots) across the plasma membrane and vacuolar membrane causes the turgor changes of guard cells

Front 338

Cycles that have intervals of approximately 24 hours.

Back 338

Circadian rhythms

Front 339

Plants adapted to arid climates, called this, have various leaf modification that reduce the rate or transpiration.

Back 339

Xerophytes

Front 340

Stomata are major pathways for:

Back 340

Water loss

Front 341

Some leaf molds, which are fungi that parasitize plants, secret a chemical that causes guard cells to accumulate potassium ions. How does this adapatation enable the leaf mold to infect the plant?

Back 341

Accumulation of potassium by guard cells results in osmotic water uptake, and the turgid condition of the cells keeps the stomata open. This enables the mold to grow into the leaf interior via the stomata.

Front 342

Describe the environmental conditions that would minimize the transpiration-to-photosynthesis ratio for a C3 plant, such as an oak tree.

Back 342

A sunny, warm, but not hot, day; high humidity; low wind speed.

Front 343

Concept 36.5:

Back 343

Organic nutrients are translocated through the phloem.

Front 344

Xylem sap flows from roots to leaves, in a direction _________ to that necessary to transport sugars form leaves to other parts of the plant.

Back 344

Opposite

Front 345

A plant organ that is a net producer of sugar, by photosynthesis or by breakdown of starch.

Back 345

Sugar source

Front 346

An organ that is a net consumer or storer of sugar.

Back 346

Sugar sink

Front 347

Companion cell have many ingrowths of their walls, enhancing transfer of solutes between apoplast and symplast. Such modified cells are called:

Back 347

Transfer cells

Front 348

Loading of sucrose into phloem.

Back 348

(a) Sucrose manufactured in mesophyll cells can travel via the symplast (blue arrows) to sieve-tube members. In some species, sucrose exist the symplast (red arrow) near sieve tubes and is actively accumulated from the apoplast by sieve-tube members and their companion cells.

(b) A chemiosmotic mechanism is responsible for the active transport of sucrose into companion cells and sieve-tube members. Proton pumps generate an H+ gradient, which drives sucrose accumulation with the help of a cotransport protein that couples sucrose transport to the diffusion of H+ back in the cell.

Front 349

Pressure flow:

Back 349

The mechanism of translocation of angiosperm

Front 350

Pressure flow in a sieve tube:

Back 350

1. Loading of sugar (green dots) into the sieve tube at the source reduces water potential inside the sieve-tube members. This causes the tube to take up water by osmosis.

2. This uptake of water generates a positive pressure that forces the sap to flow along the tube.

3. The pressure is relieved by the unloading of sugar and the consequent loss of water from the tube at the sink.

4. In the case of leaf-to-root translocation, xylem recycles water from sink to source.

Front 351

Compare and contrast the forces that move phloem sap and the forces that move xylem sap over long distances.

Back 351

In both cases, the long-distance transport is a bulk flow drive by a pressure difference at opposite ends of tubes. Pressure is generated at the source end of a sieve tube by the loading of sugar and resulting osmotic flow of water into the phloem, and this pressure pushes sap from the source end to the sink end of the tube. In contrast, transpiration generates a negative pressure (tension) as a force that pulls the ascent of xylem sap.

Front 352

Potatoes break down starch into sugar at low temperature. This is a problem for the potato chip industry because the sugar in chilled potatoes turns dark brown during processing. What effect would cooling the soil around an expanding potato tuber have on sugar import into the tuber?

Back 352

At low temperature, the higher sugar content of a growing potato tuber would lower the solute potential (and water potential) of the tuber and reduce the bulk flow of sugar into it.

Front 353

Concept 36.1: Physical forces drive the transport of materials in plants over a range of distances.

Back 353

Selective permeability of membranes: Specific transport proteins enable plant cells to maintain an internal environment different from their surroundings.

Front 354

The central role of proton pumps: The membrane potential and H+ gradient generated by proton pumps are harnessed to drive the transport of a variety of solutes.

Back 354

Effects of Differences in water potential: Solutes decrease water potential, while pressure increases water potential. Water flows by osmosis from a region with higher water potential to a region with a lower potential.

Front 355

Three major compartment of vacuolated plant cells: The plasma membrane regulates transport between the cytosol and cell wall, while the vacuolar membrane regulates transport between the cytosol and vacuole.

Back 355

Functions of the symplast and apoplast in transport: The symplast is the continuum of cytosol linked by plasmodesmata. The apoplast is the continuum of cell walls and extracellular spaces.

Front 356

Bulk flow in long-distance transport: Transport of xylem and phloem sap is due to pressure differences at opposite ends of conduits - xylem vessels and sieve tubes.

Back 356

Concept 36.2: Roots absorb water and minerals form the soil.

Front 357

The roles of root hair, mycorrhizae, and cortical cells: Root hairs are the most important avenues of absorption near root tips, but mycorrhizae, symbiotic association of fungi and root, are responsible for most absorption by the whole root system. Once soil solution enter the root, the extensive surface area of cortical cell membranes enhances uptake of water and selected minerals.

Back 357

The endodermis: a selective sentry: Water can cross the cortex via the symplast or apoplast, but minerals that reach the endodermis via the apoplast must finally cross the selective membranes of endodermal cells. The waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder.

Front 358

Concept 36.3: Water and minerals ascend from roots to shoot.

Back 358

Factors affecting the ascent of xylem: Loss of water vapor (transpiration) lowers water potential in the leaf by producing a negative pressure (tension). This low water potential draws water from the xylem. Cohesion and adhesion of the water transmit the pulling force down to the roots.

Front 359

Xylem sap ascent by bulk flow: The movement of xylem sap against gravity is maintained by transpiration.

Back 359

Concept 36.4: Stomata help regulate rate of transpiration

Front 360

Effect of Transpiration on Wilting and Leaf temperature: Plants lose an astonishing amount of water as a result of transpiration. If this lost water is not replaced by water absorption from the roots, the plant will gradually lose water and wilt.

Back 360

Stomata: Major pathways for water loss: Stomata suport photosynthesis by allowing CO2 and O2 exchange between the leaf and atmosphere. Stomata are also the main avenues for transpirational loss of water from the plant. Turgor changes in guard cells, which depend on K+ and water transport into and out of the cells, regulate the size of the stomatal openings.

Front 361

Xerophytes Adaptations that reduce transpiration: Protection of stomata within leaf indentations and other structural adaptations enable certain plants to survive in arid environments.

Back 361

Concept 36.5: Organic nutrients are translocated through the phloem.

Front 362

Movement of sugar sources to sugar sinks: Mature leaves are the main sugar sources, through storage organs such as bulbs can be sugar sources during certain seasons. Developing roots and shoot tups are some examples of sugar sinks. Phloem loading and unloading depend on the active transport of sucrose. The sucrose is cotransported along with H+, which diffuses down a gradient that is generated by proton pumps.

Back 362

Pressure flow: The Mechanism of Translocation in the Angiosperm: Loading of sugar at the source end of the sieve tube and unloading at the sink end maintain a pressure difference that keep the sap flowing through the tube.

Front 363

Concept 37.1:

Back 363

Plants require certain chemical elements to complete their life cycle.

Front 364

Plants extract this, essential chemical elements, from the soil in the form of inorganic ions.

Back 364

Mineral nutrients

Front 365

The uptake of nutrients by a plant:

Back 365

CO2, the source of carbon for photosynthesis, diffuses into leaves from the air through stomata

Roots absorb H2O and minerals from the soil

Through stomata, leaves expel H2O and O2-

Roots take in O2 and expel Co2. The plant uses O2 for cellular respiration but is a net O2 producer.

Front 366

A chemical element is considered an ______________ if it is required for a plant to complete a life cycle and produce another generation.

Back 366

Essential element

Front 367

To determine which elements are essential elements, researchers use ___________, in which plants are grown in mineral solutions instead of soil.

Back 367

Hydroponic culture

Front 368

Nine of the essential elements are called _____________ because plants require them in relatively large amounts.

Back 368

Macronutrients

Front 369

The remaining eight essential elements are known as _________ because plants need them in very small amounts.

Back 369

Micronutrients

Front 370

Macronutrients:

Back 370

Carbon
Oxygen
Hydrogen
Nitrogen
Potassium
Calcium
Magnesium
Phosphorus
Sulfur

Front 371

Micronutrients:

Back 371

Chlorine
Iron
Manganese
Boron
Zine
Copper
Nickel
Molybdenum

Front 372

Explain how the take of essential elements can be used to support Hales' hypothesis, yet does not refute van Helmont's hypothesis.

Back 372

It shows that CO2 is the source of 90% of a plant's dry weight, supporting Hales' view that plants are nourished mostly by air. However, van Helmont's hypothesisis correct with respect to a plant's overall increase in size, which is based mainly on accumulation of water in cell vacuoles.

Front 373

Are some essential elements more important than others? Explain.

Back 373

No, because even though macronutrients are required in greater amounts, all essential elements are necessary for the plant to complete its life cycle.

Front 374

Can a single leaf be used to diagnose all of a plant's mineral dificiencies? Explain.

Back 374

No, because deficiencies of nutrients that are more mobile show up first in older leaves, whereas deficiencies in nutrients that are less mobile show up first in younger leaves.

Front 375

Concept 37.2:

Back 375

Soil quality is a major determinant of plant distribution and growth

Front 376

The eventual result of all this activity is __________, a mixture of particles derived from rock, living organisms, and humus, the remains of partially decayed organic material.

Back 376

Topsoil

Front 377

The topsoil and other distinct soil layer, or __________, are often visible in vertical profile where there is a read cut or deep hole.

Back 377

Horizons

Front 378

The most fertile soils are usually _________, made up of roughly equal amounts of sand, silt (particles of intermediate size), and clay.

Back 378

Loams

Front 379

Mineral cations become available for absorption when they enter the soil solution after being displaced from soil particles by cations in the form of H+. This process is called ____________, is stimulated by the roots, which add H+ to the soil solution.

Back 379

Cation exchange

Front 380

The availability of soil water and minerals.

Back 380

A. Soil water - a plant cannot extract all the water in the soil because some of it is tightly held by hydrophilic soil particles. Water bound less tightly to soil particles can be absorbed by the root.

B. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by secreting it from root hairs and also by cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid. Dissociation of this acid adds H+ to the soil solution.

Front 381

The goal of soil management is ______________, a commitment embracing a variety of farming methods that are conservation-minded, environmentall safe, and profitable.

Back 381

Sustainable agriculture

Front 382

A new method known as _________ is a biological, nondestructive technology that seeks to reclaim contaminated areas cheaply by using the remarkable ability of some plants to extract soil pollutants and concentrate them in portions of the plant the can be easily removed for safe disposal.

Back 382

Phytoremediation

Front 383

What are the general characteristics of good soil?

Back 383

The topsoil has a mixture of larger particles (which provide aeration) and smaller particles (which facilitate water and mineral retention), as well as an adequate amount of humus (which supplies mineral nutrients) and a suitable pH.

Front 384

Explain how the phrase "too much of a good thing" can apply to watering and fertilizing plants.

Back 384

Overwatering deprives roots of oxygen and can lead to mold, and overfertilizing can result in waste and pollution of groundwater.

Front 385

The role of soil bacteria in the nitrogent nutrition of plants.

Back 385

Ammonium is made available to plants by two types of soil bacterias: those that fix atmospheric N2 (nitrogen-fixing bacteria) and those that decompose organic material (ammonifying bacteria). Although plants absorb some ammonium from the soil, they absorb mainly nitrate, which is produced from ammonium by nitrifying bacteria. Plants reduce nitrate back to ammonium before incorporating the nitrogen into organic compounds. Xylem transports nitrogen from roots to shoots in the form of nitrate, amino acids, and various other organic compounds, depending on the species.

PAGE 763

Front 386

Concept 37.3:

Back 386

Nitrogen is often the mineral that has the greatest effect on plant growth.

Front 387

Restock nitrogenous minerals in the soil by converting N2 form the atmosphere to NH3 (ammonia) in a metabolic process called nitrogen fixation.

Back 387

Nitrogen-fixing bacteria

Front 388

The enzyme complete _____________ catalyzes the entire reaction sequence, which reduces N2 and NH3 by adding electrons along with H+.

Back 388

Nitrogenase

Front 389

Explain why nitrogen-fixing bacteria are essential to human welfare.

Back 389

Nitrogen-fixing bacteria provide the longterm supply of nitrogenous minerals essential for the survival of plants, which are directly or indirectly the source of food for humans.

Front 390

Concept 37.4:

Back 390

Plant nutritional adaptations often involve relationships with other organisms

Front 391

Along a legume's roots are swellings called __________ composed of plant cells that have been "infected" by nitrogen-fixing Rhizobium (root living) bacteria.

Back 391

Nodule

Front 392

Inside the module, rhizobium bacteria assume from a form called ____________, which are contained within vesicles formed by the root cell.

Back 392

Bacteroids

Front 393

Root nodules on legumes:

Back 393

A. Pea plant root: the bumps on this pea plant root are nodules containing Rhizobium bacteria. The bacteria fix nitrogen and obtain photosynthetic products supplied by the plant.

B. Bacteroids in a soybean root nodule. In this TEM, a cell from a root nodule of soybean is filled with bacteroids in vesicles. The cells on the left are uninfected.

Front 394

Development of a soybean root nodule:

Back 394

1. Roots emit chemical signals that attract Rhizobium bacteria. The bacteria then emit signals that stimulate root hairs to elongate and to form an infection thread by an invagination of the plasma membrane.

2. The bacteria penetrate the cortex within the infection thread. Cells of the cortex and pericycle begin dividing, and vesicles containing the bacteria bud into cortical cells from the branching infection thread. This process results in the formation of bacteroids.

3. Growth continues in the affected regions of the cortex and pericycle, and these two masses of dividing cells fuse, forming the nodule.

4. The nodule develops vascular tissue that supplies nutrients to the nodule and carries nitrogenous compounds into the vascular cylinder for distribution throughout the plant.

Front 395

The agricultural benefits of symbiotic nitrogen fixation underlie ___________________. In this, a non-legume such as maize is planted one year, and the following year alfalfa or some other legume is planted to restore the concentration of fixed nitrogen in the soil.

Back 395

Crop rotation

Front 396

Modified roots consisting of mutualistic associations of fungi and roots.

Back 396

Mycorrhizae

Front 397

In this, the mycelium (mass of branching hyphae) forms a dense sheath, or mantle, over the surface of the root.

Back 397

Ectomycorrhizae

Front 398

In this, there is not a dense mantle ensheathing the root.

Back 398

Endomycorrhizae

Front 399

Compare and contrast root nodules and mycorrhizae.

Back 399

Both involve mutualistic symbiotic relationships in which other organisms interact with plant roots. Root nodules involve nitrogen-fixing bacteria, whereas mycorrhizae involve fungi that facilitate absorption of both water and minerals. In both relationships, the plant provides organic compounds. Unlike root nodules, mycorrhizae occur in most plant species, but both relationships are important agriculturally.

Front 400

Contrast epiphytes with parasitic plants.

Back 400

Epiphytes use another plant as a substrate without obtaining nutrients from the other plant.In contrast, parasitic plants extract nutrients from their host plants.

Front 401

Nourishes itself but grows on another plant, usually anchored to branches or trunks of living trees. Absorb water and minerals from rain, mostly through leaves rather than roots.

Back 401

Epiphyte

Front 402

Epiphytes examples.

Back 402

Staghorn fern

Front 403

Parasitic plants examples.

Back 403

Mistletoe, Dodder, Indian pipe

Front 404

Carnivorous plants examples.

Back 404

Venus flytrap, pitcher plants, sundews.

Front 405

Concept 37.1: Plants require chemical elements to complete their life cycle.

Plants derive most of their organic mass from the CO2 of air, but they also depend on soil nutrients in the form of water and minerals. The branching of root and shoot systems helps plants come into contact with the resources that they need from the environment.

Back 405

Macronutrients and micronutrients: Macronutrients, elements required in relatively large amounts, include carbon, oxygen, hydrogen, nitrogen, and other major ingredients of organic compounds. Micronutrients, elements required in very small amounts, typically have catalytic functions as cofactors of enzymes.

Front 406

Symptoms of mineral deficiency: Deficiency of a mobile nutrient usually affects older organs more than younger ones; the reverse is true for nutrients that are less mobile within a plant. Macronutrient deficiencies are most common, particularly deficiencies of nitrogen, phosphorus, and potassium.

Back 406

Concept 37.2: Soil quality is a major determinant of plant distribution and growth.

Front 407

Texture and Composition of Soils: Various sizes of particles derived from the breakdown of rock are found in soil, along with organic materla (humus) in various stages of decomposition. Acids derived from roots contribute to a plant's uptake of minerals when H+ displaces mineral cations from soil particles.

Back 407

Soil Conservation and Sustainable Agriculture: In contrast to natural ecosystems, agriculture depletes the mineral content of soil, taxes water reserves, and encourages erosion. The goal of soil conservation strategies is to minimize this damage. A major goal of agricultural researchers is to reduce the amount of fertilizer added to soils without sacrificing high crop yields.

Front 408

Concept 37.3: Nitrogen is often the mineral that has the greatest effect on plant growth.

Back 408

Soil Bacteria and Nitrogen Availability: Nitrogen-fixing bacteria convert atmospheric N2 to nitrogenous minerals that plants can absorb as a nitrogen source for organic synthesis.

Front 409

Improving the Protein Yield of Crops: Research devoted to improving the quality and quantity of crop proteins addresses the most widespread form of human malnutrition: protein deficiency.

Back 409

Concept 37.4: Plant nutritional adaptations often involve relationships with other organisms.

Front 410

The role of bacteria in symbiotic nitrogen fixation: The development of nitrogen-fixing root nodules depends on chemical dialogue between Rhizobium bacteria and root cells of their specific plant hosts. The bacteria of a nodule obtain sugar from the plant and supply the plant with fixed nitrogen.

Back 410

Mycorrhizae and plant nutrition: Mycorrhizae are modified roots consisting of mutualistic associations of fungi and roots.

Front 411

The fungal hyphae of both ectomycorrhizae and endomycorrhizae absorb water and minerals, which they supply to their plant hosts.

Back 411

Epiphytes, Parasitic plants, and carnivorous plants: Epiphytes grow on the surfaces of other plants but acquire water and minerals from rain. Parasitic plants absorb nutrients form the host plants. Carnivorous plants supplement their mineral nutrition by digesting animals.