1. Chapter 18
Evolution of
Plants and Fungi
Lecture Outline
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 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

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
flowers, double fertilization, endosperm, fruit
common ancestor
seeds Flowering plants
Seed
megaphylls
Gymnosperms
Vascular
vascular
tissue
Ferns and allies
Seedless
apical
growth microphylls
Lycophytes
embryo
protection Mosses
Nonvascular
Bryophytes
Hornworts
common
green Liverworts
algal
ancestor
Charophytes
550 500 450 400 350 300 250
Million Years Ago (MYA) PRESENT
18-3
Figure 18.1A The evolution of plants

4. 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

5. Figure 18.2 Alternation of generations
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
sporophyte (2n)
Mi
to
sis
zygote (2n) sporangium (2n)
diploid (2n)
FERTILIZATION MEIOSIS
haploid (n)
spore (n)
(n)
(n)
Mi
is
to
tos
gametes sis
Mi
gametophyte (n)
18-5

6. 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

7. Figure 18.3A The size of the gametophyte is progressively reduced as
the sporophyte becomes more dominant
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
spores seed seed
spores
G
a S
m p
e o
t roots
r
o o
p roots
p
h h
y rhizoids roots y
t t
e e
(n) rhizoids (2n)
Moss Fern Gymnosperm Angiosperm
18-7

8.  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

9. Figure 18.3B a. Archegonium in seedless plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
surface of
gametophyte
egg becomes
sporophyte embryo
a. Archegonium in seedless plants
© Ed Reschke 18-9

10. Figure 18.3B b. Ovule in seed plants.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
tissue of
sporophyte
ovule becomes
seed
egg becomes
sporophyte
embryo
b. Ovule in seed plants 18-10
© Ed Reschke

11.  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

12. Figure 18.3C Leaf structures of vascular plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
cuticle
stomata
Vascular plant leaves
Have a cuticle and stomata.
Stained photomicrograph
Of a leaf cross section Falsely colored scanning
Electron micrograph
Of leaf surface
(left): © Kingsley Stern; (right): © Andrew Syred/SPL/Photo Researchers, Inc.
18-12

13. 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

14. Figure 18.4A Representative bryophytes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
sporophyte
archegonium
gametophyte gemma cup
Hornwort Liverwort female gametophyte Moss gametophyte
(hornwort): © Steven P. Lynch; (liverwort): © Harold Taylor/Getty Images; (moss): © Nigel Cattlin/Photo Researchers, Inc.
18-14

15. 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

16. Figure 18.4B Moss life cycle, Polytrichum sp.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Developing sporophyte: developing
3 4
sporophyte The sporophyte:
The sporophyte embryo
The dependent sporophyte has a foot buried in female
is retained within the
gametophyte tissue, a stalk, and an upper capsule (the
archegonium, where
sporangium), where meiosis occurs and windblown spores
it develops, becoming a
are produced.
mature sporophyte.
Sporangium
Mitosis
Sporophyte
stalk
zygote
diploid (2n)
FERTILIZATION MEIOSIS
haploid (n)
2 Fertilization:
egg Spores
Flagellated sperm
sperm Spore dispersal:
produced in Mitosis 5
antheridia swim in foot (n) Spores are released
external water to when they are most
archegonia, each Archegonia likely to be
bearing a single egg. archegonium dispersed
buds
by air currents.
Antheridia
1 The mature
gametophytes: The immature
In mosses, the 6
gametophyte:
dominant A spore germinates
gametophyte shoots into the first
bear either antheridia stage of the male
or archegonia, where and the female
gametes are antheridium gametophytes.
produced by mitosis.
Gametophytes
18-16
(top): © Peter Lilja/Getty Images; (bottom): © Steven P. Lynch

17. Plant Vascular Tissue
 Vascular tissue in plants:
 Xylem transports water & minerals UP in the plant.
 Phloem transports nutrients DOWN in the plant.
18-17

18. 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

19. 18.6 Ferns have large leaves
called megaphylls
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Horsetails
 One genus, strobilus
Equisetum, and
approximately 25
species
 About 300 MYA,
horsetails were leaves
dominant plants and
grew as large as
branches
modern trees
© Gerald & Buff Corsi/Visuals Unlimited
18-19
Figure 18.6B Horsetail (Equisetum)

20. 18.6 Ferns have large leaves
called megaphylls
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Whisk ferns
 Psilotum and
Tmesipteris
 Epiphytes sporangium
 Plants that live scale
on/in trees aerial stem
 No leaves root
rhizome
(Left): © CABISCO/Phototake
18-20
Figure 18.6C Whisk fern (Psilotum)

21. 18.6 Ferns have large leaves
called megaphylls
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Ferns
 11,00 species
 Megaphylls spores on
fertile frond
called fronds
 Leaves first Cinnamon fern, Osmunda cinamomea
appear as
frond
(undivided)
fiddleheads frond
(divided)
 2 generations
separate and axis
independent leaflet
Hart’s tongue fern Maidenhair fern,
Campyloneurum scolopendrium Adiantum pedatum
(cinnamon fern): © James Randklev/Getty Images; (hart's tongue): © Walter H. Hodge/Peter
Arnold/Photolibrary; (maidenhair): © Jeff Foott/Getty Images
18-21
Figure 18.6D Diversity of fern fronds

22. Figure 18.6E Fern life cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 The sporophyte: Sori
The sporophyte is
dominant in ferns.
Sporophyte
frond
6 Young sporophyte: Dryopterus
The sporophyte
embryo develops leaflet
inside an
archegonium. sporangium
As the distinctive
first leaf appears
Sorus
above the 2 The sporangia:
gametophyte, and young sporophyte In this fern, the
as the roots fiddlehead roots
on gametophyte sporangia are
develop below it, located within sori
the young sporophyte (sing., sorus) on
Mitosis
becomes visible. the underside of
the leaflets.
zygote
Sporangium
diploid (2n)
FERTILIZATION MEIOSIS
haploid (n)
3 The spores:
5 Fertilization:
Within a
Fertilization takes sporangium,
place when egg meiosis occurs
Spores
moisture is and spores are
present, because produced. When a
sperm
the flagellated Archegonium sporangium opens,
sperm must swim Mitosis the spores are
in a film of water released.
from the antheridia germinating
to eggs within spore
archegonia.
4 The gametophyte:
Antheridium
A spore germinates into a
heart-shaped gametophyte,
which typically bears archegonia
Gametophyte at the notch and antheridia at the
tip between the rhizoids.
(Top right): © Matt Meadows/Peter Arnold/Photolibrary 18-22

23. 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

24. 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

25. Figure 18.7A Gymnosperm diversity
18-25

26. Figure 18.7A Gymnosperm diversity (Cont.)
18-26

27. Figure 18.7A Gymnosperm diversity (Cont.)
18-27

28. Figure 18.7B Pine life cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 The pollen cones:
Typically, the pollen
The sporophyte cones are quite small
5
embryo:After and develop near the
fertilization, the tips of lower
ovule matures and branches.
becomes the seed
composed of the Sporophyte
embryo, reserve The seed cones:
food, and a seed The seed cones are
seed wing
coat. Finally, in the larger than the pollen
fall of the second Seed cones
cones and are located
season, the seed Pollen cones near the tips of higher
cone, by Ovule branches.
now woody and Pollen sac
hard, opens to sporophyte
release winged embryo
seeds. When
a seed germinates, seed coat seed cone scale 2 Megaspores:
the sporophyte stored food pollen cone scale Megaspore mother cell
Seed in ovule undergoes
Mitosis meiosis to produce
megaspores.One
megaspore will
become the
zygote microspore megaspore egg-producing
4 Fertilization: mother cell mother cell
Once a pollen grain
reaches a seed cone, diploid (2n)
it becomes a mature FERTILIZATION MEIOSIS MEIOSIS Microspores:
haploid (n)
male gametophyte. Microspore mother
A pollen tube digests Pollen grain cells undergo meiosis
its way slowly Microspores to produce
toward a female Mature female gametophyte microspores. Each
Mitosis
gametophyte and egg Megaspores microspore becomes a
discharges pollen grain.
nonflagellated sperm. Pollination
The fertilized ovule
wall Ovule
egg is
a zygote.
Mitosis
Mature male gametophyte
pollen grain
pollen tube
sperm
200 µm
3 The pollen grain:
The pollen grain has two wings and is carried by the
wind to the seed cone during pollination
(Bottom right): © Phototake
18-28

29. 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

30. Figure 18A Swamp forest of the Carboniferous period
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fossil seed fern
(fossil fern): © Sinclair Stammers/SPL/Photo Researchers, Inc.
18-30

31. Figure 18A Swamp forest of the Carboniferous period (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fossil seed fern
club mosses
horsetail
seed fern
early gymnosperm
fern
18-31
(fossil fern): © Sinclair Stammers/SPL/Photo Researchers, Inc

32. 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

33. Figure 18.8A Generalized flower
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
anther stigma
pollen
tube
filament style
stamens ovary
ovule
carpel
receptacle
petals (corolla) sepals (calyx)
18-33

34. Figure 18.8B Flowering plant life cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stamen Carpel 1 The stamen: The carpel:
anther stigma An anther at the top of each The ovary at the base of a
filament style stamen has four pollen sacs. carpel contains one or more
ovules. The contents of an
ovary
ovule change during the
ovule flowering plant life cycle.
6 The sporophyte embryo:
The embryo within a seed
is the immature sporophyte.
When a seed germinates, Mitosis stigma
growth and differentiation receptacle
produce the mature Sporophyte
fruit style
sporophyte of a flowering Anther
(mature ovary)
plant. seed
(mature ovule) Carpel
ovule
5 The seed:
The ovule now develops into ovary
the seed, which contains an seed coat pollen
embryo and food enclosed sporophyte embryo sac
by a protective seed coat.
The wall of the ovary and endosperm (3n)
microspore
sometimes adjacent parts mother cell megaspore
develop into a fruit that Seed
mother cell
surrounds the seed(s).
diploid (2n)
FERTILIZATION MEIOSIS MEIOSIS
haploid (n) Pollen grain
(mature male gametophyte)
4 Double fertilization:
Mi
On reaching the ovule, the ovule wall Pollination
tos
pollen tube discharges the pollen Microspores Megaspores
is
sperm. One of the two sperm polar nuclei tube
migrates to and fertilizes the sperm
sperm
egg, forming a zygote; the
egg
other unites with the two polar nuclei
polar nuclei, producing a 3n pollen tube degenerating
Mi
(triploid) endosperm nucleus. egg
tos
The endosperm nucleus megaspores
Double Fertilization
is
divides to form endosperm,
food for the developing plant. Ovule
Embryo sac 2 Microspores:
(mature female gametophyte) Microspore mother cells undergo meiosis to produce
microspores. Each microspore becomes a pollen grain.
3 The mature male gametophyte: The mature female gametophyte: Megaspores:
A p[ollen grain that lands on the carpel of the same type The ovule now contains the mature female Megaspore mother cell inside ovule undergoes meiosis to
of plant germinates and produces a pollen tube, gametophyte (embryo sac), which typically consists of produce megaspores. One megaspore will become the
which delivers two nonflagellated sperm to the female eight haploid nuclei embedded in a mass of cytoplasm. egg-producing female gametophyte.
gametophyte. A fully germinated pollen grain is the The cytoplasm differentiates into cells, one of which is
mature male gametophyte. an egg and another of which contains two polar nuclei.
18-34

35. 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 plants
18-35

36. Figure 18B.1 Species of grains important to humans
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
grain head
grain head ear
Wheat plants,Triticum Corn plants, Zea Rice plants, Oryza
(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
18-36

37. Figure 18B.2 Uses of plants
18-37

38. 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

39. Figure 18.9A
Fungal mycelia
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. and hyphae
nuclei
septum
cell wall
nonseptate septate
hypha hypha
a. Fungal mycelia on a corn tortilla b. Cell structure of hyphae
(a): © Gary R. Robinson/Visuals Unlimited
18-39

40. 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

41. Figure 18.10 Lichen structure and examples
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
algal reproductive unit fungal
cell hyphae sac fungi
reproductive
cups
Crustose lichen
Foliose lichen, Xanthoparmelia Fruticose lichen, Cladonia
(foliose): © Kerry T. Givens; (fruticose): © Stephen Sharnoff/Visuals Unlimited
18-41

42. 18.11 Land fungi
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
occur in
4
3 zygospore
FERTILIZATION
2n
n
MEIOSIS
three main
Sexual
reproduction 5
groups
sporangium  Zygospore Fungi
 Mainly saprotrophs,
1
but some are
Asexual
reproduction
parasites
–
2
germinating
spores
+
mycelium
Figure 18.11A
Black bread mold,
(top left): © Runk/Schoenberger/Grant Heilman Photography Rhizopus stolonifer 18-42

43. 18.11 Land fungi occur in
three main groups Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
 Sac Fungi
ascocarp
 Nearly 75% of all
described fungal ascocarp
species
Cup fungi
 Ex: Yeast – 1 celled nuclear
fusion zygote Morel
fungi. (2n) meiosis
mature
ascospores
ascus
dikaryotic
hyphae
+ mating type (n) – mating type (n)
spore spore
male organ
female organ
Ascocarp of the cup fungus Sarcoscypha
(cup fungi): © Felix Labhardt/Getty RF; (morel): © Robert Marien/Corbis RF18-43
Figure 18.11B Sexual reproduction in sac fungi

44. Figure 18.11C Asexual reproductive structures in sac fungi
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
budding
conidia yeast cell
a. b.
a: © David Philips/Visuals Unlimited; b: © David Philips/Visuals Unlimited;
18-44

45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
18.11 Land fungi
nuclei in
basidium occur in
three main groups
 Club Fungi
fusion meiosis
spores  Name comes from the
reproductive structure,
the basidium
gill of
mushroom  The basidia are
located within a
basidiocarp
basidiocarp  When you eat a
mushroom, you are
eating a basidiocarp
- +
Sexual reproduction
18-45
Figure 18.11D Sexual reproduction in club fungi

46. Figure 18.11D Sexual
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
reproduction in club fungi
involves a basidiocarp of
which three types are
shown (Cont.)
Mushroom Shelf fungi
Gaint puffball
(mushroom): © Biophoto Assoc./Photo Researchers, Inc.; (shelf fungi): © Inga Spence; (puffball): © L. West/Photo Researchers, Inc
18-46

47. 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 18-47
 Systemic-spread through body via blood

48. Figure 18C.1 Plant fungal disease
18-48

49. Figure 18C.2 Human fungal diseases
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
back of throat
tongue
a. Ringworm b.Athlete’s foot c. Thrush
© John Hadfield/SPL/Photo Researchers, Inc.; © CMSP/Getty Images; Courtesy of the Centers for Diseare Control and Prevention
18-49

50. 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