Bio 100 Chapter 18
Transcript of Bio 100 Chapter 18
Chapter 18Evolution of
Plants and FungiLecture Outline
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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
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18-3
Figure 18.1A The evolution of plants
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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
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Figure 18.2 Alternation of generations
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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
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Figure 18.3A The size of the gametophyte is progressively reduced as the sporophyte becomes more dominant
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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
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Figure 18.3B a. Archegonium in seedless plants
18-9© Ed Reschke
surface ofgametophyte
egg becomessporophyte embryo
a. Archegonium in seedless plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Figure 18.3B b. Ovule in seed plants.
b. Ovule in seed plants
tissue ofsporophyte
ovule becomesseed
egg becomessporophyteembryo
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© 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
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Figure 18.3C Leaf structures of vascular plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
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Figure 18.4A Representative bryophytes
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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
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Figure 18.4B Moss life cycle, Polytrichum sp.
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(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.
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Ferns: Seedless vascular plants
Ferns, horsetails, and whisk ferns are seedless vascular plants
Have megaphylls Broad leaves with several strands of
vascular tissue
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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
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Figure 18.6B Horsetail (Equisetum)
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strobilus
branches
leaves
© Gerald & Buff Corsi/Visuals Unlimited
18.6 Ferns have large leaves called megaphylls
Whisk ferns Psilotum and
Tmesipteris Epiphytes
Plants that live on/in trees
No leaves
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Figure 18.6C Whisk fern (Psilotum)
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rhizome
sporangium
aerial stem
scale
root
(Left): © CABISCO/Phototake
18.6 Ferns have large leaves called megaphylls
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
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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
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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
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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
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Figure 18.7A Gymnosperm diversity
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Figure 18.7A Gymnosperm diversity (Cont.)
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Figure 18.7A Gymnosperm diversity (Cont.)
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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
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Figure 18A Swamp forest of the Carboniferous period
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Fossil seed fern
(fossil fern): © Sinclair Stammers/SPL/Photo Researchers, Inc.
Figure 18A Swamp forest of the Carboniferous period (Cont.)
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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
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Figure 18.8A Generalized flower
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petals (corolla) sepals (calyx)
stamens
anther
filament
receptacle
stigma
ovary
ovule
style
pollentube
carpel
Figure 18.8B Flowering plant life cycle
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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
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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
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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
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Figure 18.9A Fungal mycelia and hyphae
18-39
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
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Figure 18.10 Lichen structure and examples
18-41
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(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
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Figure 18.11A Black bread mold, Rhizopus stolonifer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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.
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Figure 18.11B Sexual reproduction in sac fungi
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(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
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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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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.)
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Shelf fungiMushroom
Gaint puffball
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(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
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Figure 18C.1 Plant fungal disease
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Figure 18C.2 Human fungal diseases
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© 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.
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