Bio 100 Chapter 18

Chapter 18Evolution of

Plants and FungiLecture Outline

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18.1 Plants have a green algal ancestor

Multicellular, photosynthetic eukaryotes Evolved from freshwater green algae some 500

million years ago Evidence – Both green algae and plants

1. Contain chlorophylls a and b and various accessory pigments

2. Store excess carbohydrates as starch

3. Have cellulose in their cell wall

18-2

18-3

Figure 18.1A The evolution of plants


common ancestor

megaphylls

microphylls

seeds

flowers, double fertilization, endosperm, fruit

Flowering plants

Gymnosperms

Ferns and allies

Mosses

Lycophytes

Hornworts

Vas

cula

rN

on

vasc

ula

r

See

dle

ssB

ryo

ph

ytes

See

d

Liverworts

Charophytes

550 400450500 350 300 250PRESENT

commongreenalgalancestor

embryoprotection

apicalgrowth

vasculartissue

Million Years Ago (MYA)

18.2 Alternation of generations life cycle

2 multicellular stages alternate

Sporophyte represents the diploid generation (2n) Produces spores by meiosis A spore undergoes mitosis to become a gametophyte

Gametophyte represents the haploid generation (n) Produces gametes In plants, eggs and sperm are produced by mitosis A sperm and egg fuse, forming a diploid zygote that

undergoes mitosis and becomes the sporophyte

18-4

18-5

Figure 18.2 Alternation of generations


zygote (2n)

sporophyte (2n)

spore (n)

gametophyte (n)

(n)(n)

gametes

Mito

sis

Mitosis

Mitosis

sporangium (2n)

diploid (2n)

haploid (n)MEIOSISFERTILIZATION

18.3 Sporophyte dominance was adaptive to a dry land environment

Plants differ as to which generation is dominant

Only the sporophyte has vascular tissue for transporting water and nutrients

Only plants with a dominant sporophyte generation attain significant height

18-6

Figure 18.3A The size of the gametophyte is progressively reduced as the sporophyte becomes more dominant

18-7


Moss Fern Gymnosperm Angiosperm

roots

roots

roots

rhizoids

Gametophyte

(n)

Sporophyte

(2n)

seed seedspores spores

rhizoids

Reproductive Adaptation to Land Environment Ferns are seedless vascular plants with a dominant

sporophyte Water-dependent gametophyte makes it more difficult for

ferns and related plants to spread to and live in dry environments

Flowering plants are seed plants with a dominant sporophyte All reproductive structures are protected from drying out in

the terrestrial environment

18-8

Figure 18.3B a. Archegonium in seedless plants

18-9© Ed Reschke

surface ofgametophyte

egg becomessporophyte embryo

a. Archegonium in seedless plants


18-10

Figure 18.3B b. Ovule in seed plants.

b. Ovule in seed plants

tissue ofsporophyte

ovule becomesseed

egg becomessporophyteembryo


© Ed Reschke

Other Adaptations to the Land Environment

Spophytes have a cuticle Covering that provides an effective barrier to water

loss, but it also limits gas exchange

Leaves have little openings called stomata (sing., stoma) that let carbon dioxide enter while allowing oxygen and water to exit

18-11

18-12

Figure 18.3C Leaf structures of vascular plants


Falsely colored scanningElectron micrographOf leaf surface

Stained photomicrographOf a leaf cross section

stomata

Vascular plant leavesHave a cuticle and stomata.

cuticle

(left): © Kingsley Stern; (right): © Andrew Syred/SPL/Photo Researchers, Inc.

Bryophytes: Non-Vascular Plants

Exs: hornworts, liverworts, and mosses

First plants to colonize land

Successfully reproduce on land because they protect the embryo & produce wind-blown spores

No true roots, stems, or leaves – no vascular tissue “Non-vascular” plants

18-13

Figure 18.4A Representative bryophytes

18-14


Hornwort Liverwort female gametophyte Moss gametophyte

sporophyte

gametophyte

archegonium

gemma cup

(hornwort): © Steven P. Lynch; (liverwort): © Harold Taylor/Getty Images; (moss): © Nigel Cattlin/Photo Researchers, Inc.

In Bryophytes, the Gametophyte is Dominant

Bryophyte reproduction Gametophyte is the dominant generation Female gametophyte produces eggs in archegonia,

and the male gametophyte produces flagellated sperm in antheridia

Following fertilization, the zygote becomes a sporophyte

Sporophyte attached to, and derives its nourishment from, the photosynthetic gametophyte

18-15

Figure 18.4B Moss life cycle, Polytrichum sp.

18-16


(top): © Peter Lilja/Getty Images; (bottom): © Steven P. Lynch

zygote

spermegg

Archegonia

Antheridia

Spores

Sporangium

Gametophytes

buds

Mitosis

Mitosis

haploid (n)

diploid (2n)

1

2

5

6

Developing sporophyte: The sporophyte embryo is retained within the archegonium, where it develops, becoming a mature sporophyte.

developingsporophyte

Fertilization: Flagellated sperm produced in antheridia swim in external water to archegonia, each bearing a single egg.

The maturegametophytes:In mosses, thedominantgametophyte shootsbear either antheridiaor archegonia, wheregametes areproduced by mitosis.

Spore dispersal: Spores are released when they are most likely to be

dispersed by air currents.

The immature gametophyte: A spore germinates into the first stage of the male and the female gametophytes.

3

archegonium

antheridium

The sporophyte: The dependent sporophyte has a foot buried in female gametophyte tissue, a stalk, and an upper capsule (the sporangium), where meiosis occurs and windblown spores are produced.

4

MEIOSISFERTILIZATION

Sporophyte

stalk

foot (n)

Plant Vascular Tissue

Vascular tissue in plants: Xylem transports water & minerals UP in the plant. Phloem transports nutrients DOWN in the plant.

18-17

Ferns: Seedless vascular plants

Ferns, horsetails, and whisk ferns are seedless vascular plants

Have megaphylls Broad leaves with several strands of

vascular tissue

18-18

18.6 Ferns have large leaves called megaphylls

Horsetails One genus,

Equisetum, and approximately 25 species

About 300 MYA, horsetails were dominant plants and grew as large as modern trees

18-19

Figure 18.6B Horsetail (Equisetum)


strobilus

branches

leaves

© Gerald & Buff Corsi/Visuals Unlimited


Whisk ferns Psilotum and

Tmesipteris Epiphytes

Plants that live on/in trees

No leaves

18-20

Figure 18.6C Whisk fern (Psilotum)


rhizome

sporangium

aerial stem

scale

root

(Left): © CABISCO/Phototake


Ferns 11,00 species Megaphylls

called fronds Leaves first

appear as fiddleheads

2 generations separate and independent

18-21Figure 18.6D Diversity of fern fronds


Cinnamon fern, Osmunda cinamomea

frond(undivided)

Hart’s tongue fernCampyloneurum scolopendrium

Maidenhair fern,Adiantum pedatum

spores onfertile frond

axis

leaflet

(cinnamon fern): © James Randklev/Getty Images; (hart's tongue): © Walter H. Hodge/Peter Arnold/Photolibrary; (maidenhair): © Jeff Foott/Getty Images

frond(divided)

Figure 18.6E Fern life cycle

18-22


Sporophyte

fiddlehead roots

frond

Sporangium

sperm

Antheridium

egg

Archegonium

Gametophyte

Spores

zygote

leaflet

Sorus

sporangium

MEIOSIS

Dryopterus

Mitosis

Mitosis

haploid (n)

diploid (2n)

5

6

4

3

2

1 The sporophyte: The sporophyte is dominant in ferns.

Young sporophyte:The sporophyteembryo developsinside anarchegonium. As the distinctivefirst leaf appearsabove thegametophyte, and as the roots develop below it,the young sporophyte becomes visible.

young sporophyteon gametophyte

FERTILIZATION

The sporangia:In this fern, thesporangia arelocated within sori(sing., sorus) onthe underside of the leaflets.

The spores:Within asporangium,meiosis occursand spores areproduced. When asporangium opens,the spores arereleased.

germinatingspore

The gametophyte:A spore germinates into aheart-shaped gametophyte,which typically bears archegoniaat the notch and antheridia at thetip between the rhizoids.

Fertilization: Fertilization takes place when moisture is present, because the flagellated sperm must swim in a film of water from the antheridia to eggs within archegonia.

(Top right): © Matt Meadows/Peter Arnold/Photolibrary

Sori

Gymnosperms & Angiosperms

Gymnosperms and angiosperms are seed plants

Seed contains a sporophyte generation, along with stored food, within a protective seed coat

Ability of seeds to survive harsh conditions until the environment is again favorable for growth largely accounts for the dominance of seed plants today

18-23

18.7 Most gymnosperms bear cones on which the seeds are “naked”

Diversity of Gymnosperms Four groups of living gymnosperms: cycads,

ginkgoes, gnetophytes, and conifers All have ovules and develop seeds that are exposed

on the surface of cone scales or analogous structures

Conifers Consist of about 575 species of trees

Many are evergreens such as pines, spruces, firs, cedars and hemlocks

Economic Value of Conifers Wood of conifers is used extensively in construction

18-24

Figure 18.7A Gymnosperm diversity

18-25

Figure 18.7A Gymnosperm diversity (Cont.)

18-26

Figure 18.7A Gymnosperm diversity (Cont.)

18-27

18-28

Figure 18.7B Pine life cycleCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Pollen sac

Seedstored food

seed coat

zygote

seed wing

Sporophyte

pollen cone scale

Seed cones

seed cone scale

Pollen cones

sperm

pollen tube

egg

Mature female gametophyte

Pollen grain

Pollination

Megaspores

Microspores

pollen grain

Megaspores:Megaspore mother cellin ovule undergoesmeiosis to producemegaspores.Onemegaspore willbecome theegg-producing

The pollen grain:The pollen grain has two wings and is carried by thewind to the seed cone during pollination

Mature male gametophyte

200 µm

MEIOSIS MEIOSIS

Ovule

Ovule

Mitosis

Mitosis

Mitosis

haploid (n)

diploid (2n)

3

4

5

1

2

FERTILIZATION

The sporophyteembryo:Afterfertilization, theovule matures andbecomes the seedcomposed of theembryo, reservefood, and a seedcoat. Finally, in thefall of the secondseason, the seedcone, bynow woody andhard, opens torelease wingedseeds. Whena seed germinates,the sporophyte

sporophyteembryo

Fertilization:Once a pollen grainreaches a seed cone,it becomes a maturemale gametophyte.A pollen tube digestsits way slowlytoward a femalegametophyte anddischargesnonflagellated sperm. The fertilizedegg isa zygote.

ovulewall

megasporemother cell

microsporemother cell

The pollen cones:Typically, the pollencones are quite smalland develop near thetips of lowerbranches.

The seed cones: The seed cones arelarger than the pollencones and are locatednear the tips of higherbranches.

Microspores:Microspore mothercells undergo meiosisto producemicrospores. Eachmicrospore becomes apollen grain.

(Bottom right): © Phototake

HOW LIFE CHANGES

18A Carboniferous Forests Became the Coal We Use Today

Our industrial society runs on fossil fuels, such as coal

During Carboniferous period (>300 MYA) a great swamp forest encompassed what is now northern Europe, the Ukraine, and the Appalachian Mountains in the United States. Enormous amount of biomass Remains became covered by sediment that changed

to sedimentary rock With pressure, the organic material became coal

18-29

Figure 18A Swamp forest of the Carboniferous period

18-30


Fossil seed fern

(fossil fern): © Sinclair Stammers/SPL/Photo Researchers, Inc.

Figure 18A Swamp forest of the Carboniferous period (Cont.)

18-31


early gymnosperm

club mosses

horsetail

seed fern

fern

Fossil seed fern

(fossil fern): © Sinclair Stammers/SPL/Photo Researchers, Inc

Angiosperms: Flowering Plants

Angiosperms are flowering plants Evolved some 200 MYA 240,000 known species Ovules always enclosed within sporophyte tissue

Angiosperm Diversity Monocots – One cotyledon Eudicots – Two cotyledons Cotyledons – seed leaves with nutrients that nourish

the embryo

18-32

Figure 18.8A Generalized flower

18-33


petals (corolla) sepals (calyx)

stamens

anther

filament

receptacle

stigma

ovary

ovule

style

pollentube

carpel

Figure 18.8B Flowering plant life cycle

18-34


ovary

stigma

style

Megaspores

sperm

pollen tube

Microspores

(mature male gametophyte)Pollen grain

Embryo sac

(mature female gametophyte)

Pollination

polar nuclei

ovule wall

egg

Seed

endosperm (3n)

sporophyte embryo

seed coat

SporophyteAnther

egg

polar nuclei

Stamen Carpel

stigmastyleovaryovule

filamentanther

MEIOSIS MEIOSIS

sperm

ovule

The mature male gametophyte:A p[ollen grain that lands on the carpel of the same typeof plant germinates and produces a pollen tube,which delivers two nonflagellated sperm to the femalegametophyte. A fully germinated pollen grain is themature male gametophyte.

Mitosis

Mitosis

Mitosis

Ovule

diploid (2n)

haploid (n)

Carpel

Double Fertilization

receptacle

3

4

5

6

1

2

The stamen:An anther at the top of eachstamen has four pollen sacs.

The carpel:The ovary at the base of acarpel contains one or moreovules. The contents of anovule change during theflowering plant life cycle.

pollensac

microsporemother cell megaspore

mother cell

degeneratingmegaspores

Microspores:Microspore mother cells undergo meiosis to producemicrospores. Each microspore becomes a pollen grain.

Megaspores:Megaspore mother cell inside ovule undergoes meiosis toproduce megaspores. One megaspore will become theegg-producing female gametophyte.

pollentube

FERTILIZATION

The mature female gametophyte:The ovule now contains the mature femalegametophyte (embryo sac), which typically consists of eight haploid nuclei embedded in a mass of cytoplasm. The cytoplasm differentiates into cells, one of which is an egg and another of which contains two polar nuclei.

Double fertilization: On reaching the ovule, thepollen tube discharges thesperm. One of the two spermmigrates to and fertilizes theegg, forming a zygote; theother unites with the twopolar nuclei, producing a 3n(triploid) endosperm nucleus.The endosperm nucleusdivides to form endosperm,food for the developing plant.

The seed:The ovule now develops intothe seed, which contains anembryo and food enclosedby a protective seed coat.The wall of the ovary andsometimes adjacent partsdevelop into a fruit thatsurrounds the seed(s).

The sporophyte embryo:The embryo within a seedis the immature sporophyte.When a seed germinates,growth and differentiationproduce the maturesporophyte of a floweringplant.

fruit(mature ovary)seed(mature ovule)

HOW BIOLOGY IMPACTS OUR LIVES

18B Flowering plants provide many services

Humans derive most of their sustenance from three flowering plants Wheat

First cultivated in the Middle East about 8000 B.C. Thought to be one of the earliest cultivated plants

Corn Maize first cultivated in Central America about 7,000 years

ago

Rice Originated several thousand years ago in southeastern Asia,

where it grew in swamps

About 50% of all pharmaceuticals come from plants18-35

Figure 18B.1 Species of grains important to humans

18-36


Corn plants, Zea Rice plants, Oryza

eargrain head

Wheat plants,Triticum

grain head

(wheat): © Creatas Images RF; (corn plants, rice plant): © Corbis RF; (ear of corn): © Dorling Kindersley/Getty RF; (rice grains): © Dex Image/Getty RF; © Corbis RF

Figure 18B.2 Uses of plants

18-37

Fungi differ from plants & animals

Structurally diverse group of eukaryotes Strict Heterotrophs

Unlike animals, fungi release digestive enzymes into the external environment and digest their food outside the body

Most are saprotrophs – decomposers Body of most fungi made of a mass of filaments

(hypha) called a mycelium Cell walls contain chitin

18-38

Figure 18.9A Fungal mycelia and hyphae

18-39


a. Fungal mycelia on a corn tortilla b. Cell structure of hyphae

nuclei

septum

cell wall

nonseptatehypha

septatehypha

(a): © Gary R. Robinson/Visuals Unlimited

18.10 Fungi have mutualistic relationships with algae and plants

In a mutualistic relationship, two different species live together and help each other out

Mycorrhizal fungi form mutualistic relationships (mycorrhizae) with the roots of most plants

Lichen – a mutualistic association between a fungus and a green algae

18-40

Figure 18.10 Lichen structure and examples

18-41


(foliose): © Kerry T. Givens; (fruticose): © Stephen Sharnoff/Visuals Unlimited

Fruticose lichen, CladoniaFoliose lichen, Xanthoparmelia

Crustose lichen

reproductive unitalgalcell

fungalhyphae sac fungi

reproductivecups

18.11 Land fungi occur in

three main groups

Zygospore Fungi Mainly saprotrophs,

but some are parasites

18-42

Figure 18.11A Black bread mold, Rhizopus stolonifer


zygospore

sporangium

mycelium

+

MEIOSIS2nn

34

Sexualreproduction

Asexualreproduction

1

2

(top left): © Runk/Schoenberger/Grant Heilman Photography

FERTILIZATION

–germinatingspores

5

1

18.11 Land fungi occur in three main groups

Sac Fungi Nearly 75% of all

described fungal species

Ex: Yeast – 1 celled fungi.

18-43

Figure 18.11B Sexual reproduction in sac fungi


(cup fungi): © Felix Labhardt/Getty RF; (morel): © Robert Marien/Corbis RF

meiosis

Ascocarp of the cup fungus Sarcoscypha

Cup fungi

Morel

ascocarp

ascocarp

ascospores

male organ

female organ

nuclearfusion zygote

(2n)matureascus

dikaryotichyphae

+ mating type (n)spore

– mating type (n)spore

Figure 18.11C Asexual reproductive structures in sac fungi

18-44


a: © David Philips/Visuals Unlimited; b: © David Philips/Visuals Unlimited;

conidia

a. b.

buddingyeast cell

18.11 Land fungi occur in

three main groups

Club Fungi Name comes from the

reproductive structure, the basidium

The basidia are located within a basidiocarp

When you eat a mushroom, you are eating a basidiocarp

18-45Figure 18.11D Sexual reproduction in club fungi


basidiocarp

fusion meiosis

Sexual reproduction

spores

nuclei inbasidium

gill ofmushroom

+-

Figure 18.11D Sexual reproduction in club fungi involves a basidiocarp of which three types are shown (Cont.)

18-46

Shelf fungiMushroom

Gaint puffball


(mushroom): © Biophoto Assoc./Photo Researchers, Inc.; (shelf fungi): © Inga Spence; (puffball): © L. West/Photo Researchers, Inc

HOW BIOLOGY IMPACTS OUR LIVES

18.15 Land Fungi Have Economic and Medical Importance

Economic Importance Help produce medicines and many foods

Mold Penicillium was original source of penicillin

Excellent low-calorie meat substitute containing lots of vitamins Fungal pathogens are a major concern for farmers

Medical Importance Certain mushrooms are poisonous Mycoses are diseases caused by fungi

3 levels of infection Cutaneous-skin Subcutaneous-affects a deeper level Systemic-spread through body via blood

18-47

Figure 18C.1 Plant fungal disease

18-48

Figure 18C.2 Human fungal diseases

18-49


© John Hadfield/SPL/Photo Researchers, Inc.; © CMSP/Getty Images; Courtesy of the Centers for Diseare Control and Prevention

a. Ringworm c. Thrush

tongue

back of throat

b.Athlete’s foot

Connecting the Concepts:Chapter 18

Plants Trend towards gametophyte dependence on a

sporophyte with large leaves and vascular tissue Angiosperms are the most widely dispersed of the

land plants

Fungi Adapted to the land environment because they

produce windblown spores.

18-50

Bio 100 Chapter 18

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