Plant APBio

Chapter 21Chapter 21

TheThePlant KingdomPlant Kingdom

Chapter 21 2 Key Features of PlantsKey Features of Plants

Multicellularity Multicellularity Ability to photosynthesize (most)Ability to photosynthesize (most)Exhibit Exhibit alternation of generationsalternation of generations (a (a multicellular diploid generation multicellular diploid generation alternates with a multicellular haploid alternates with a multicellular haploid generation)generation)

Chapter 21 3 Alternation of GenerationsAlternation of Generations

Diploid Diploid sporophytesporophyte plant produces plant produces haploid spores through meiosishaploid spores through meiosis

Spores divide by mitosis and develop Spores divide by mitosis and develop into haploid gametophyte plantsinto haploid gametophyte plants

Haploid Haploid gametophyte gametophyte plant produces plant produces haploid gametes through mitosishaploid gametes through mitosis

Gametes fuse to form diploid Gametes fuse to form diploid zygoteszygotes, , which divide by mitosis and develop which divide by mitosis and develop into diploid sporophytesinto diploid sporophytes

Chapter 21 4

HaploidHaploidDiploidDiploid

GametophytesGametophytesform by meiosisform by meiosis

Spores formSpores formby meiosisby meiosis

nnnnnn

Alternation of GenerationsAlternation of Generationsin Plantsin Plants

SporeSporeMotherMother

CellCell

EggEgg

SpermSpermGametes meetGametes meet& fuse to form& fuse to formzygotezygote

ZygoteZygote

EmbryoEmbryoSporo-Sporo-phytephyte

22nn

SporesSporesnn

Gameto-Gameto-phytephyte

22nn

nnnn

22nn

22nn

22nn

Chapter 21 5

Evolution of PlantsEvolution of Plants

The evolutionary origin of plantsThe evolutionary origin of plants• Division Rhodophyta—red algaeDivision Rhodophyta—red algae

• Division Phaeophyta—brown algaeDivision Phaeophyta—brown algae

• Division Chlorophyta—green algae and the Division Chlorophyta—green algae and the origin of land plantsorigin of land plants

Chapter 21 6 Green AlgaeGreen Algae

Several lines of evidence support the Several lines of evidence support the hypothesis that green algae gave rise to hypothesis that green algae gave rise to plantsplants

DNA comparisons show that green algae DNA comparisons show that green algae are plants’ closest living relativesare plants’ closest living relatives

Both use the same type of chlorophyll and Both use the same type of chlorophyll and accessory pigments in photosynthesisaccessory pigments in photosynthesis

Both store food as starchBoth store food as starchBoth have cell walls made of celluloseBoth have cell walls made of cellulose

Chapter 21 7 Fresh Water AncestorsFresh Water Ancestors

Most green algae live in fresh water, Most green algae live in fresh water, suggesting that early plants evolved in suggesting that early plants evolved in freshwater habitatsfreshwater habitats

Early green algae must have evolved Early green algae must have evolved characteristics to withstand the challenges characteristics to withstand the challenges of fresh water habitats, e.g. temperature of fresh water habitats, e.g. temperature extremes, periods of drynessextremes, periods of dryness

These adaptations provided a foundation for These adaptations provided a foundation for descendants to evolve traits for life on landdescendants to evolve traits for life on land

Chapter 21 8

The Evolution of Land PlantsThe Evolution of Land PlantsRoots and rootlike structures (anchor & absorb)Roots and rootlike structures (anchor & absorb)Vascular tissue for transport of water & nutrientsVascular tissue for transport of water & nutrientsStiffening substance (lignin) for supportStiffening substance (lignin) for supportWaxy covering (cuticle) limits evaporationWaxy covering (cuticle) limits evaporationStomatal poresStomatal pores• Mediate gas exchangeMediate gas exchange• Regulate water vapor lossRegulate water vapor loss

Evolutionary adaptations in plant reproductionEvolutionary adaptations in plant reproduction• Early algae relied on water currents for fertilizationEarly algae relied on water currents for fertilization• Dry land adaptation include the generation of Dry land adaptation include the generation of

pollen, seeds, flowers, and fruit…pollen, seeds, flowers, and fruit…• Adaptations in the alternation of generations…Adaptations in the alternation of generations…

Chapter 21 9 Reproduction Without WaterReproduction Without Water

PollenPollen• A reduced male gametophyte that allows wind A reduced male gametophyte that allows wind

(instead of water) to carry sperm to eggs(instead of water) to carry sperm to eggs

SeedsSeeds• Nourish, protect, and help disperse developing Nourish, protect, and help disperse developing

embryosembryos

FlowersFlowers• Attract pollinators Attract pollinators

FruitsFruits• Attract animals to disperse seedsAttract animals to disperse seeds

Chapter 21 10 Major Groups of PlantsMajor Groups of Plants

BryophytesBryophytes ( (nonvascular plantsnonvascular plants))• Lack well-developed structures for Lack well-developed structures for

conducting water and nutrientsconducting water and nutrients

Tracheophytes Tracheophytes ((Vascular plantsVascular plants ) )• Have a complex vascular systemHave a complex vascular system

Chapter 21 11

Evolutionary Evolutionary TreeTreeof Major of Major Plant Plant GroupsGroups

AncestralAncestralAlgaeAlgae

AncestralAncestralAlgaeAlgae

Liver-Liver-wortsworts MossesMosses

BryophytesBryophytes

True vascular tissueTrue vascular tissue& lignin appear& lignin appear

FernsFerns Gymno-Gymno-spermssperms

Seeds andSeeds andpollen appearpollen appear

Flowers &Flowers &Fruits appearFruits appear

Seed PlantsSeed Plants

Angio-Angio-spermssperms

TracheophytesTracheophytes

Chapter 21 12

The BryophytesThe Bryophytes

Nonvascular plantsNonvascular plants

No true roots, leaves, and stemsNo true roots, leaves, and stems

Still require a moist environmentStill require a moist environment

Anchoring rhizoids absorb water & nutrientsAnchoring rhizoids absorb water & nutrients

Reproductive structures protect gametesReproductive structures protect gametes

Still depend on water for fertilizationStill depend on water for fertilization

Dominant gametophyte generationDominant gametophyte generation

Chapter 21 13

Liverworts & MossesLiverworts & MossesLiverwortsLiverwortsFemaleFemale

GametophyteGametophyteArchegoniumArchegonium

(a)(a)(a)(a) (b)(b)(b)(b)

MossesMosses

FemaleFemaleGametophytesGametophytes

SporophytesSporophytes

Chapter 21 14 The Bryophytes: ReproductionThe Bryophytes: Reproduction

Gametes develop within protected Gametes develop within protected structures on gametophytestructures on gametophyte• ArchegoniaArchegonia (singular, archegonium) (singular, archegonium)

produce eggsproduce eggs• AntheridiaAntheridia (singular, antheridium) (singular, antheridium)

produce spermproduce sperm• Archegonia and antheridia may be Archegonia and antheridia may be

located on the same plant or on different located on the same plant or on different plantsplants

Chapter 21 15

Life Life Cycle Cycle

of a of a Moss Moss

(a)(a)

Zygote develops intoZygote develops intosporophyte withinsporophyte withingametophytegametophyte

SporophyteSporophyteCapsule Capsule

Fertilization Fertilization

Mei

osis

M

eios

is

Haploid spores liberatedHaploid spores liberatedfrom sporophyte capsulefrom sporophyte capsule

OldOldGametophyteGametophyte

Spores disperseSpores disperseand germinateand germinate

HaploidHaploid11nn

DiploidDiploid22nn

Chapter 21 16

Life Life Cycle Cycle

of a of a Moss Moss

(b)(b)HaploidHaploid

11nn

DiploidDiploid22nn

Spore germinatesSpore germinatesinto gametophyteinto gametophyte

LeafyLeafyGametophyteGametophyte

ArchegoniumArchegoniumproduces eggproduces egg

AntheridiumAntheridiumproduces spermproduces sperm

Sperm swimSperm swimto eggto egg

FertilizationFertilization

Chapter 21 17 The Vascular PlantsThe Vascular Plants

Have roots, stems, and leavesHave roots, stems, and leavesHave Have vesselsvessels impregnated with the impregnated with the stiffening agent ligninstiffening agent lignin

Sporophyte generation is dominantSporophyte generation is dominantInclude the seedless vascular plants Include the seedless vascular plants and the seed plantsand the seed plants

Chapter 21 18

Division Tracheophyta:Division Tracheophyta:Vascular PlantsVascular Plants

Adapted to life in drier conditionsAdapted to life in drier conditions• Had to generate body supportHad to generate body support

• Vessels to conduct water and nutrientsVessels to conduct water and nutrients

• A stiffening substance called ligninA stiffening substance called lignin

Seedless plants: club mosses, horsetails, Seedless plants: club mosses, horsetails, and fernsand ferns• Sporophyte generation more dominantSporophyte generation more dominant

• Fertilization still relies on waterFertilization still relies on water

Chapter 21 19

Life Cycle Life Cycle of Ferns (a)of Ferns (a)

HaploidHaploid11nn

DiploidDiploid22nn

GametophyteGametophyte

Sporophyte developsSporophyte developsfrom gametophytefrom gametophyte

RootRoot

StemStem

SporophyteSporophyte

Masses ofMasses ofSporangiaSporangia

MeiosisMeiosis

Haploid spores liberatedHaploid spores liberatedfrom sporangiumfrom sporangium

SporangiumSporangium

Chapter 21 20

Life Cycle of Ferns (b)Life Cycle of Ferns (b)

HaploidHaploid11nn

DiploidDiploid22nn

Haploid spores liberatedHaploid spores liberatedfrom sporangiumfrom sporangium

Spores disperseSpores disperse& germinate& germinate

GametophyteGametophyte

ArchegoniumArchegoniumproduces eggproduces egg

AntheridiumAntheridiumproduces spermproduces sperm

Sperm swimSperm swimto eggto egg

FertilizationFertilization

Chapter 21 21

Seedless PlantsSeedless Plants

Club MossesClub MossesClub MossesClub Mosses

HorsetailsHorsetailsHorsetailsHorsetails

FernsFernsFernsFerns

Chapter 21 22

Seed Plants:Seed Plants:GeneralGeneral

Dominance of the sporophyte generationDominance of the sporophyte generation

Reproductive adaptationsReproductive adaptations• Pollen Pollen

– Wind and pollinators for fertilizationWind and pollinators for fertilization– Water not required for fertilizationWater not required for fertilization

• SeedsSeeds– Stores food for embryoStores food for embryo– Embryo protection for unfavorable environmentsEmbryo protection for unfavorable environments

Chapter 21 23

SeedsSeeds

(a) Gymnosperm(a) Gymnosperm (d) Water Dispersal(d) Water Dispersal

(c) Wind Dispersal(c) Wind Dispersal

Stored FoodStored FoodStored FoodStored Food

EmbryoEmbryoEmbryoEmbryo

Seed CoatSeed CoatSeed CoatSeed Coat (b) Angiosperm(b) Angiosperm

Chapter 21 24

Seed Plants:Seed Plants:GymnospermsGymnosperms

Nonflowering seed plantsNonflowering seed plantsProduce "naked seeds"Produce "naked seeds"Three divisions:Three divisions:• ConiferophytaConiferophyta• CycadophytaCycadophyta• GinkgophytaGinkgophyta

Conifers are adapted to dry, cold conditionsConifers are adapted to dry, cold conditions• Thin, waterproof needles to decrease evaporationThin, waterproof needles to decrease evaporation• Evergreen; year-round photosynthesisEvergreen; year-round photosynthesis• Produce an "antifreeze" substance in sapProduce an "antifreeze" substance in sap

Chapter 21 25

Two UncommonTwo UncommonGymnospermsGymnosperms

(a) Gingko(a) Gingko

(b) A Cycad – either (b) A Cycad – either male or femalemale or female

Chapter 21 26 Gymnosperms: ConifersGymnosperms: Conifers

Adapted to dry, cold conditions:Adapted to dry, cold conditions:• Retain green leaves throughout the year Retain green leaves throughout the year

(evergreen)(evergreen)• Thin, needle-like leaves covered with Thin, needle-like leaves covered with

waterproofing material to reduce waterproofing material to reduce evaporationevaporation• Produce an Produce an ““antifreeze” in sapantifreeze” in sap

Chapter 21 27

Life Life Cycle of Cycle of the Pine the Pine (a) (a)

HaploidHaploid11nn

DiploidDiploid22nn

MatureMatureSporophyteSporophyte

MatureMatureSporophyteSporophyte

SeedlingsSeedlings(Sporophyte)(Sporophyte)SeedlingsSeedlings

(Sporophyte)(Sporophyte)

MaleMaleConeConeMaleMale

ConeCone

MaleMaleScaleScale

MaleMaleScaleScale

MEIOSISMEIOSIS

MEIOSISMEIOSIS

Male gametophytesMale gametophytes(pollen) liberated(pollen) liberated

FemaleFemaleConeCone

FemaleFemaleConeCone

FemaleFemaleScaleScale

FemaleFemaleScaleScale

OvuleOvuleOvuleOvule

Spore-formingSpore-formingCellCell


MEIOSISMEIOSIS

MEIOSISMEIOSIS

Chapter 21 28

Life Cycle of the Pine (b)Life Cycle of the Pine (b)

HaploidHaploid11nn

DiploidDiploid22nn

MEIOSISMEIOSIS

MEIOSISMEIOSIS

Pollen liberated;Pollen liberated;Dispersed by windDispersed by wind

MEIOSISMEIOSIS

MEIOSISMEIOSIS

SeedlingsSeedlings(Sporophyte)(Sporophyte)SeedlingsSeedlings

(Sporophyte)(Sporophyte)

Egg CellEgg CellEgg CellEgg Cell

FemaleFemaleGametophyteGametophyte


Pollen lands onPollen lands onfemale scalefemale scale

PollenPollenTubeTube


FERTILIZATIONFERTILIZATIONFERTILIZATIONFERTILIZATION

SeedSeedSeedSeed

EmbryoEmbryoEmbryoEmbryo

Chapter 21 29

Seed Plants:Seed Plants:AngiospermsAngiosperms

Flowering seed plantsFlowering seed plantsThe dominant plant form on EarthThe dominant plant form on EarthMajor evolutionary adaptationsMajor evolutionary adaptations• Flowers to attract pollinatorsFlowers to attract pollinators• Fruit to protect seeds and developing Fruit to protect seeds and developing

embryoembryo• Broad leavesBroad leaves

– Increase photosynthesis during the growing Increase photosynthesis during the growing seasonseason

– Shed during periods of cold and droughtShed during periods of cold and drought

Chapter 21 30

Monocot vs DicotMonocot vs Dicot

Class Monocotyledoneae (monocots): Class Monocotyledoneae (monocots): grasses, grains, corngrasses, grains, corn

1 cotyledon1 cotyledonleave veins in parallel linesleave veins in parallel linesFlower parts, in multiple of 3Flower parts, in multiple of 3scattered vascular bundlesscattered vascular bundles

Class Dicotyledoneae (dicots): hardwood Class Dicotyledoneae (dicots): hardwood trees, shrubs, and herbstrees, shrubs, and herbs

2 cotyledons, web-like veins, flower 2 cotyledons, web-like veins, flower petals in 4/5s, ringed vascular bundlespetals in 4/5s, ringed vascular bundles

Chapter 21 31

Chapter 21 32 FlowersFlowers

FlowersFlowers are reproductive structures in which are reproductive structures in which both male and female gametophytes are both male and female gametophytes are formedformed

Believed to have evolved when gymnosperm Believed to have evolved when gymnosperm ancestors formed an association with animalsancestors formed an association with animals• Animals benefited by eating some of the protein-Animals benefited by eating some of the protein-

rich pollenrich pollen• Plants benefited by using animals as pollinatorsPlants benefited by using animals as pollinators

Most flowers are showy and attract animal Most flowers are showy and attract animal pollinators (e.g. insects)pollinators (e.g. insects)

Chapter 21 33

Life Cycle of aLife Cycle of aFlowering Plant (a)Flowering Plant (a)

FruitFruitFruitFruit

SeedSeedSeedSeed

FoodFoodFoodFoodEmbryoEmbryoEmbryoEmbryo

Seed CoatSeed CoatSeed CoatSeed Coat

SeedlingSeedlingSeedlingSeedling FlowerFlowerFlowerFlowerAntherAntherAntherAnther

MEIOSISMEIOSISMEIOSISMEIOSIS

OvaryOvaryOvaryOvary

OvuleOvuleOvuleOvule



HaploidHaploid11nn

DiploidDiploid22nn

Chapter 21 34

Life Cycle of a Flowering Plant (b)Life Cycle of a Flowering Plant (b)

FruitFruitFruitFruit

MEIOSISMEIOSISMEIOSISMEIOSIS

MEIOSISMEIOSIS

MEIOSISMEIOSIS

SporeSporeSporeSpore



Egg CellEgg CellEgg CellEgg Cell

Pollen (malePollen (malegametophyte)gametophyte)Pollen (malePollen (male

gametophyte)gametophyte)

StigmaStigmaStigmaStigma



SpermSpermNucleiNuclei

SpermSpermNucleiNuclei

FERTILIZATION

FERTILIZATION

FERTILIZATION

FERTILIZATION

HaploidHaploid11nn

DiploidDiploid22nn

Chapter 21 35 Fruits Encourage Seed DispersalFruits Encourage Seed Dispersal

FruitsFruits are mature ovaries that contain are mature ovaries that contain developing seedsdeveloping seeds

Various fruit adaptations help disperse Various fruit adaptations help disperse seedsseeds• Edible fruits entice animals to eat them Edible fruits entice animals to eat them

(seeds pass through digestive tract (seeds pass through digestive tract unharmed)unharmed)• Burrs cling to animal furBurrs cling to animal fur•Winged fruits are carried through the airWinged fruits are carried through the air

Chapter 21 36 Broad LeavesBroad Leaves

Broad leaves of angiosperms collect more Broad leaves of angiosperms collect more sunlight for photosynthesis than narrow sunlight for photosynthesis than narrow leaves of gymnospermsleaves of gymnosperms

Temperate angiosperms drop leaves to Temperate angiosperms drop leaves to conserve water when it is in short supply conserve water when it is in short supply (fall, winter)(fall, winter)

Tropical and subtropical angiosperms are Tropical and subtropical angiosperms are evergreenevergreen•May shed leaves during dry seasonMay shed leaves during dry season

Chapter 21 37 Broad LeavesBroad Leaves

Photosynthetic advantage is offset by Photosynthetic advantage is offset by fact that broad, tender leaves are more fact that broad, tender leaves are more appealing to herbivores than tough, appealing to herbivores than tough, waxy needles of coniferswaxy needles of conifers

Angiosperm defenses includeAngiosperm defenses include• Physical defenses (thorns, spines, resins)Physical defenses (thorns, spines, resins)• Chemical defenses (make plant tissue Chemical defenses (make plant tissue

poisonous or distasteful)poisonous or distasteful)

Chapter 21 38 Crucial Ecological RoleCrucial Ecological Role

Through photosynthesis, plants provide Through photosynthesis, plants provide food, directly or indirectly, for all of the food, directly or indirectly, for all of the animals, fungi, and non-photosynthetic animals, fungi, and non-photosynthetic microbes on landmicrobes on land

Plants produce oxygen gas as a Plants produce oxygen gas as a byproduct of photosynthesis, byproduct of photosynthesis, continually replenishing oxygen in the continually replenishing oxygen in the atmosphere atmosphere

Chapter 21 39 Crucial Ecological RoleCrucial Ecological Role

Plants help create and maintain soilPlants help create and maintain soil• Dead plant material is decomposed by Dead plant material is decomposed by

fungi, prokaryotes, and other fungi, prokaryotes, and other decomposersdecomposers• Decomposed plant tissue becomes part Decomposed plant tissue becomes part

of the soil, making it more fertileof the soil, making it more fertile• Roots of living plants help hold soil Roots of living plants help hold soil

together, preventing erosion by wind and together, preventing erosion by wind and water water

Chapter 21 40 Human Necessities and LuxuriesHuman Necessities and Luxuries

Plants provide shelterPlants provide shelter•Wood is used to construct housing Wood is used to construct housing

Plants provide fuelPlants provide fuel•Wood: important fuel for warming and Wood: important fuel for warming and

cooking in many parts of the worldcooking in many parts of the world• Coal: derived from the remains of Coal: derived from the remains of

ancient plants that have been ancient plants that have been transformed by geological processestransformed by geological processes

Chapter 21 41 Human Necessities and LuxuriesHuman Necessities and Luxuries

Plants provide medicinePlants provide medicine•Many medicines and drugs were Many medicines and drugs were

originally found in and extracted from originally found in and extracted from plants, e.g. aspirin, Taxol, morphineplants, e.g. aspirin, Taxol, morphine

Plants provide pleasurePlants provide pleasure• Flowers, gardens, and lawnsFlowers, gardens, and lawns• Coffee, tea, and wineCoffee, tea, and wine

Chapter 21Chapter 21

The EndThe End

Economy & Finance

Plant APBio