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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 29
Plant Diversity I: How Plants
Colonized Land
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Overview: The Greening of Earth
• Around 500 million years ago, small plants,
fungi, and animals emerged on land
• Now approximately 290,000 species
• Have terrestrial ancestors
• Do not include protists
• Supply oxygen
• Ultimate source of food for land animals
© 2011 Pearson Education, Inc.
Figure 29.1
1 m
Concept 29.1: Land plants evolved from
green algae
• called charophytes
• share four key traits with only charophytes
– Rings of cellulose-synthesizing complexes
– Peroxisome enzymes – minimize loss of organic
products during photorespiration
– Structure of flagellated sperm
– Formation of a phragmoplast – precusor to cell
plate
– Comparison of nuclear and chloroplast genes
© 2011 Pearson Education, Inc.
Figure 29.3
5 mm
Chara species, a pond organism
Coleochaete orbicularis, a
disk-shaped charophyte
that also lives in ponds (LM)
40 m
1 m
Adaptations Enabling the Move to Land
• sporopollenin prevents exposed zygotes
from drying out; also found in plant spore
walls
• provided unfiltered sun,
• more plentiful CO2,
• nutrient-rich soil, and
• few herbivores or pathogens
• Land presented challenges: a scarcity of
water and lack of structural support
© 2011 Pearson Education, Inc.
Derived Traits of Plants
• Four key traits appear in nearly all land plants but
are absent in the charophytes
– 1. Alternation of generations and multicellular,
dependent embryos
– 2. Walled spores produced in sporangia
– 3. Multicellular gametangia
– 4. Apical meristems
© 2011 Pearson Education, Inc.
Alternation of Generations and Multicellular,
Dependent Embryos
• gametophyte - haploid and produces haploid
gametes by mitosis
• Fusion of the gametes gives rise to the diploid
sporophyte, which produces haploid spores by
meiosis
© 2011 Pearson Education, Inc.
Figure 29.5a
Gametophyte
(n)
Mitosis
n
Gamete from
another plant
Mitosis
n
FERTILIZATION
2n
Sporophyte
(2n)
Haploid (n)
Diploid (2n)
n Spore Gamete n
MEIOSIS
Key
Zygote
Mitosis
Alternation of generations
1 m
The Flow
• Sporophyte (meiosis)spores (mitosis)
to produce gametophytereleases
gametes produced by
mitosisfertiliztion produces
zygotemitosis develops a sporophyte
Walled Spores Produced in Sporangia
• The sporophyte produces spores in organs called
sporangia
• Diploid cells called sporocytes undergo meiosis
to generate haploid spores
• Spore walls contain sporopollenin, which makes
them resistant to harsh environments
© 2011 Pearson Education, Inc.
Figure 29.5c
Spores
Sporangium
Longitudinal section of
Sphagnum sporangium (LM)
Sporophyte
Gametophyte
1 m
Sporophytes and sporangia of Sphagnum (a moss)
Multicellular Gametangia
• Gametes are produced within
organs called gametangia
• Female gametangia, - archegonia,
produce eggs and are the site of
fertilization
• Male gametangia - antheridia,
produce and release sperm
© 2011 Pearson Education, Inc.
Figure 29.5d
Female
gametophyte
Archegonia,
each with an
egg (yellow)
Antheridia
(brown),
containing
sperm
Male
gametophyte
Archegonia and antheridia of Marchantia (a liverwort)
1 m
Apical Meristems
• Plant growth occurs at this
structural site
• Cells from the apical meristems
differentiate into various tissues
© 2011 Pearson Education, Inc.
Figure 29.5e
Apical meristem
of shoot
Developing
leaves
Apical meristems of plant
roots and shoots
Apical
meristem
of root
Root
100 m
Shoot
1 m
100 m
• Additional derived traits include
a. Cuticle, a waxy covering of the
epidermis
b. Mycorrhizae, symbiotic associations
between fungi and land plants that may
have helped plants without true roots to
obtain nutrients
c. Secondary compounds that deter
herbivores and parasites
© 2011 Pearson Education, Inc.
The Origin and Diversification of Plants
• Fossil evidence indicates that plants
were on land at least 475 million years
ago
• Fossilized spores and tissues have
been extracted from 475-million-yearold rocks
© 2011 Pearson Education, Inc.
Figure 29.6
(a) Fossilized
spores
(b) Fossilized
sporophyte
tissue
1 m
Figure 29.7
1 Origin of land plants (about 475 mya)
2 Origin of vascular plants (about 425 mya)
3 Origin of extant seed plants (about 305 mya)
Mosses
Land plants
ANCESTRAL
1
GREEN
ALGA
Nonvascular
plants
(bryophytes)
Liverworts
Hornworts
Pterophytes (ferns,
horsetails, whisk ferns)
3
Angiosperms
500
450
400
350
300
Millions of years ago (mya)
50
0
1 m
Seed plants
Gymnosperms
Vascular plants
2
Seedless
vascular
plants
Lycophytes (club
mosses, spike
mosses, quillworts)
• Land plants can be informally grouped
based on the presence or absence of
vascular tissue
• Most plants have vascular tissue; these
constitute the vascular plants
• Nonvascular plants are commonly
called bryophytes
© 2011 Pearson Education, Inc.
• A seed - an embryo and nutrients
surrounded by a protective coat
• Seed plants:
– Gymnosperms, the “naked seed”
plants, including the conifers
– Angiosperms, the flowering plants
© 2011 Pearson Education, Inc.
Table 29. 1
1 m
Concept 29.2:Dominant gametophyte stage
• Bryophytes are represented today by
three phyla of small herbaceous
(nonwoody) plants
– Liverworts
– Hornworts
– Mosses
© 2011 Pearson Education, Inc.
Figure 29.8-1
“Bud”
Key
Haploid (n)
Diploid (2n)
Protonemata
(n)
“Bud”
Spores
Male
gametophyte
(n)
Gametophore
Spore
dispersal
Female
gametophyte
(n)
Peristome
Sporangium
MEIOSIS
Mature sporophytes
Rhizoid
Seta
Capsule
(sporangium)
2 mm
Foot
Capsule with
peristome (LM)
1 m
Female
gametophytes
Figure 29.8-2
“Bud”
Key
Haploid (n)
Diploid (2n)
Protonemata
(n)
“Bud”
Sperm
Antheridia
Male
gametophyte
(n)
Egg
Spores
Gametophore
Spore
dispersal
Female
gametophyte
(n)
Peristome
Sporangium
MEIOSIS
Mature sporophytes
Archegonia
Rhizoid
FERTILIZATION
(within archegonium)
Seta
Capsule
(sporangium)
2 mm
Foot
Capsule with
peristome (LM)
1 m
Female
gametophytes
Figure 29.8-3
“Bud”
Key
Haploid (n)
Diploid (2n)
Protonemata
(n)
“Bud”
Antheridia
Male
gametophyte
(n)
Sperm
Egg
Spores
Gametophore
Spore
dispersal
Female
gametophyte
(n)
Peristome
Sporangium
MEIOSIS
Mature sporophytes
Archegonia
Rhizoid
FERTILIZATION
Zygote (within archegonium)
(2n)
Seta
Capsule
(sporangium)
Foot
Embryo
2 mm
Archegonium
Capsule with
peristome (LM)
Young
sporophyte
(2n)
Female
gametophytes
1 m
2 mm
Figure 29.8a
1 m
Capsule with peristome (LM)
Animation: Moss Life Cycle
© 2011 Pearson Education, Inc.
Figure 29.9a
Thallus
Gametophore of
female gametophyte
Sporophyte
Foot
Seta
Marchantia polymorpha,
a “thalloid” liverwort
Marchantia
sporophyte (LM)
500 m
Capsule
(sporangium)
Plagiochila deltoidea, a
“leafy” liverwort
1 m
Figure 29.9b
An Anthoceros
hornwort species
Sporophyte
Gametophyte
1 m
Figure 29.9c
Polytrichum commune,
hairy-cap moss
Capsule
Seta
Sporophyte
(a sturdy
plant that
takes months
to grow)
Gametophyte
1 m
The Ecological and Economic Importance
of Mosses
• Mosses are capable of inhabiting
diverse and sometimes extreme
environments, but are especially
common in moist forests and wetlands
• Some mosses might help retain
nitrogen in the soil
© 2011 Pearson Education, Inc.
• Sphagnum, or “peat moss,” forms extensive
deposits of partially decayed organic material
known as peat
• Peat can be used as a source of fuel
• Sphagnum is an important global reservoir of
organic carbon
• Overharvesting of Sphagnum and/or a drop in
water level in peatlands could release stored CO2
to the atmosphere
© 2011 Pearson Education, Inc.
Figure 29.11
(a) Peat being harvested from a
peatland
(b) “Tollund Man,” a bog mummy
dating from 405–100 B.C.E.
1 m
Concept 29.3: Ferns and other seedless
vascular plants were the first plants to
grow tall
• Vascular plants began to diversify during the
Devonian and Carboniferous periods
• Vascular tissue allowed these plants to grow
tall
• Seedless vascular plants have flagellated
sperm and are usually restricted to moist
environments
© 2011 Pearson Education, Inc.
Life Cycles with Dominant Sporophytes
• In contrast with bryophytes,
sporophytes of seedless vascular
plants are the larger generation, as
in familiar ferns
• The gametophytes are tiny plants
that grow on or below the soil
surface
Animation: Fern Life Cycle
© 2011 Pearson Education, Inc.
Figure 29.13-1
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Sporangium
Sporangium
Mature
sporophyte
(2n)
Sorus
Fiddlehead (young leaf)
1 m
Figure 29.13-2
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Spore
(n)
Rhizoid
Underside
of mature
gametophyte
(n)
Sporangium
Sporangium
Antheridium
Young
gametophyte
Archegonium
Egg
Mature
sporophyte
(2n)
FERTILIZATION
Sorus
Fiddlehead (young leaf)
Sperm
1 m
Figure 29.13-3
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Spore
dispersal
Spore
(n)
Rhizoid
Underside
of mature
gametophyte
(n)
Sporangium
Sporangium
Antheridium
Young
gametophyte
Mature
sporophyte
(2n)
Sorus
New
sporophyte
Sperm
Archegonium
Egg
Zygote
(2n)
Gametophyte
Fiddlehead (young leaf)
1 m
FERTILIZATION
Vascular Plants
• 1. Xylem conducts most of the water and minerals
and includes dead cells called tracheids
• Water-conducting cells are strengthened by lignin
and provide structural support
• 2. Phloem consists of living cells and distributes
sugars, amino acids, and other organic products
• Vascular tissue allowed for increased
height, which provided an evolutionary
advantage
© 2011 Pearson Education, Inc.
Evolution of Roots
• Roots are organs that anchor
vascular plants
• They enable vascular plants to
absorb water and nutrients from
the soil
–Roots may have evolved from
subterranean stems
© 2011 Pearson Education, Inc.
Evolution of Leaves
• Leaves are organs that increase
the surface area of vascular plants,
thereby capturing more solar
energy that is used for
photosynthesis
© 2011 Pearson Education, Inc.
• Most seedless vascular plants are homosporous,
producing one type of spore that develops into a
bisexual gametophyte
• All seed plants and some seedless vascular plants
are heterosporous
• Heterosporous species produce megaspores,
which give rise to female gametophytes, and
microspores, which give rise to male
gametophytes
© 2011 Pearson Education, Inc.
Figure 29.15a
2.5 cm
1 cm
Selaginella
moellendorffii,
a spike moss
Isoetes
gunnii,
a quillwort
Strobili
(clusters of
sporophylls)
Diphasiastrum
1 m tristachyum,
a club moss
Figure 29.15b
Equisetum arvense,
field horsetail
Athyrium
filix-femina,
lady fern
Vegetative stem
1.5 cm
25 cm
Strobilus on
fertile stem
4 cm
Psilotum
nudum,
a whisk
fern
1 m
The Significance of Seedless Vascular Plants
• The ancestors of modern lycophytes, horsetails,
and ferns grew to great heights during the
Devonian and Carboniferous, forming the first
forests
• Increased growth and photosynthesis removed
CO2 from the atmosphere and may have
contributed to global cooling at the end of the
Carboniferous period
• The decaying plants of these Carboniferous
forests eventually became coal
© 2011 Pearson Education, Inc.
Figure 29.16
Fern
Lycophyte trees
Horsetail
Tree trunk
covered with
small leaves
1 m
Lycophyte tree
reproductive
structures