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BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 17
Plants, Fungi, and the
Colonization of Land
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Plants and Fungi—A Beneficial Partnership
• Mutually beneficial associations of plant roots
and fungi are common
– These associations are called mycorrhizae
– They may have enabled plants to colonize land
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• Citrus growers face a dilemma
– They use chemicals to control disease-causing
fungi
– But these also kill beneficial mycorrhizae
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17.1 What is a plant?
• Plants are multicellular photosynthetic
eukaryotes
– They share many characteristics with green
algae
– However, plants evolved unique features as they
colonized land
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PLANT
LEAF
performs
photosynthesis
CUTICLE
reduces water
loss; STOMATA
allow gas exchange
STEM
supports plant
(and may perform
photosynthesis)
Surrounding water
supports the alga
ROOTS
anchor plant;
absorb water and
minerals from
the soil (aided
by mycorrhizal
fungi)
ALGA
WHOLE ALGA
performs
photosynthesis;
absorbs water,
CO2, and
minerals from
the water
HOLDFAST
anchors the alga
Figure 17.1A
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• Unlike algae, plants have vascular tissue
– It transports water and nutrients throughout the
plant body
– It provides internal support
Figure 17.1B
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PLANT EVOLUTION AND DIVERSITY
17.2 Plants evolved from green algae called
charophyceans
• Molecular studies indicate that green algae
called charophyceans are the closest relatives of
plants
Figure 17.2A, B
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• Cooksonia was one of the earliest vascular land
plants
Sporangia
Figure 17.2C
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17.3 Plant diversity provides clues to the
evolutionary history of the plant kingdom
• Two main lineages arose early from ancestral
plants
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Gymnosperms
(e.g., conifers)
Seedless vascular plants
(e.g., ferns, horsetails)
Bryophytes (e.g., mosses)
Charophyceans (a group of green algae)
CENOZOIC
MESOZOIC
PALEOZOIC
Radiation of
flowering plants
First seed plants
Early vascular plants
Origin of plants
Figure 17.3A
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• One lineage gave rise to bryophytes
– These are plants that lack vascular tissue
– Bryophytes include mosses, which grow in a low,
spongy mat
Figure 17.3B
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• Vascular plants are the other ancient lineage
• Ferns and seed plants were derived from early
vascular plants and contain
– xylem and phloem
– well-developed roots
– rigid stems
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• Ferns are seedless plants whose flagellated
sperm require moisture to reach the egg
Figure 17.3C
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• A major step in plant evolution was the
appearance of seed plants
– Gymnosperms
– Angiosperms
• These vascular plants have pollen grains for
transporting sperm
• They also protect their embryos in seeds
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• Gymnosperms, such as pines, are called naked
seed plants
– This is because their seeds do not develop inside
a protective chamber
• The seeds of angiosperms, flowering plants,
develop in ovaries within fruits
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ALTERNATION OF GENERATIONS AND
PLANT LIFE CYCLES
17.4 Haploid and diploid generations alternate in
plant life cycles
• The haploid gametophyte produces eggs and
sperm by mitosis
– The eggs and sperm unite, and the zygote
develops into the diploid sporophyte
– Meiosis in the sporophyte produces haploid
spores, which grow into gametophytes
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Gametophytes
(male and female)
n
Spores
n
Meiosis
Gametes
(sperm and eggs)
n
HAPLOID
Fertilization
DIPLOID
Zygote
2n
Sporophyte
2n
Figure 17.4
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17.5 Mosses have a dominant gametophyte
• Most of a mat of moss consists of gametophytes
– These produce eggs and swimming sperm
– The zygote stays on the gametophyte and
develops into the less conspicuous sporophyte
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5 Mitosis and
Sperm (n) (released from
their gametangium)
development
Spores
(n)
1
Gametangium
containing the egg (n)
(remains within
gametophyte)
Gametophytes
(n)
Egg
HAPLOID
Meiosis
Fertilization
DIPLOID
Sporangium
Stalk
2
4
Zygote
(2n)
Gametophyte
(n)
3 Mitosis and
development
Sporophytes (growing from gametophytes)
Figure 17.5
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17.6 Ferns, like most plants, have a dominant
sporophyte
• Ferns, like mosses, have swimming sperm
• The fern zygote remains on the small,
inconspicuous gametophyte
– Here it develops into the sporophyte
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5
Sperm (n)
Mitosis and
development
Spores
(n)
1
Gametophyte (n)
(underside)
Egg (n)
HAPLOID
Meiosis
Sporangia
Fertilization
DIPLOID
2
4
Zygote
(2n)
3 Mitosis and
development
Sporophyte (2n)
New sporophyte growing
out of gametophyte
Figure 17.6
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17.7 Seedless plants formed vast “coal forests”
• Ferns and other seedless plants once dominated
ancient forests
– Their remains formed coal
Figure 17.7
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• Gymnosperms that produce cones, the conifers,
largely replaced the ancient forests of seedless
plants
– These plants remain the dominant
gymnosperms today
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17.8 A pine tree is a sporophyte with tiny
gametophytes in its cones
• Sporangia in male cones make spores that
develop into male gametophytes
– These are the pollen grains
• Sporangia in female cones produce female
gametophytes
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4
Female gametophyte (n)
Haploid spore cells in
ovule develop into
female gametophyte,
which makes egg.
5 Male gametophyte (pollen)
Egg (n)
grows tube to egg and
makes and releases sperm.
Sperm (n)
Male gametophyte
(pollen grain)
HAPLOID
DIPLOID
MEIOSIS
Ovule
Fertilization
Scale
Sporangium
(2n)
Seed
coat
3 Pollination
HAPLOID
Pollen grains
(male
gametophytes)
(n)
Embryo
(2n)
Integument
1 Female cone
bears ovules.
6 Zygote develops
MEIOSIS
into embryo, and
ovule becomes
seed.
2 Male cone produces
spores by meiosis;
spores develop into
pollen grains
Zygote
(2n)
7
Sporophyte
Seed
Seed falls to
ground and germinates,
and embryo grows into tree.
Figure 17.8
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17.9 The flower is the centerpiece of angiosperm
reproduction
• Most plants are angiosperms
– The hallmarks of these plants are flowers
Pollen grains
Anther
Stigma
CARPEL
Ovary
STAMEN
PETAL
Ovule
SEPAL
Figure 17.9A, B
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17.10 The angiosperm plant is a sporophyte with
gametophytes in its flowers
• The angiosperm life cycle is similar to that of
conifers
– But it is much more rapid
– In addition, angiosperm seeds are protected and
dispersed in fruits, which develop from ovaries
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2 Haploid spore in each
Stigma
Egg (n)
ovule develops into
female gametophyte,
which produces egg.
3 Pollination
Pollen
grain
and
growth
of pollen
tube
Ovule
Pollen
tube
1 Haploid spores
in anthers develop
into pollen grains:
male gametophytes.
Sperm
Pollen (n)
HAPLOID
Meiosis
Fertilization
DIPLOID
4
Zygote
(2n)
Food supply
Seed
coat
Seeds
7 Seed
Ovary
germinates,
and embryo
grows into plant.
Ovule
Sporophyte
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6 Fruit
5 Seed
Embryo
(2n)
Figure 17.10
17.11 The structure of a fruit reflects its function in
seed dispersal
• Fruits are adaptations that disperse seeds
Figure 17.11A-C
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17.12 Connection: Agriculture is based almost
entirely on angiosperms
• Gymnosperms supply most of our lumber and
paper
• Angiosperms provide most of our food
– Fruits, vegetables, and grains
• Angiosperms also provide other important
products
– Medications, fiber, perfumes
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17.13 Interactions with animals have profoundly
influenced angiosperm evolution
• Angiosperms are a major source of food for
animals
– Animals also aid plants in pollination and seed
dispersal
Figure 17.13A-C
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17.14 Connection: Plant diversity is a
nonrenewable resource
• 20% of the tropical forests worldwide were
destroyed in the last third of the 20th century
• The forests of North America have shrunk by
almost 40% in the last 200 years
Figure 17.14
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• Some plants in these forests can be used in
medicinal ways
– More than
25% of
prescription
drugs are
extracted
from plants
Table 17.14
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FUNGI
17.15 Fungi and plants moved onto land together
• Plants probably moved onto land along with
mycorrhizal fungi
– These fungi help plants absorb water and
nutrients
– They are mutualistic organisms
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• Other fungi are
– parasites
– predators
– decomposers of
dead organisms
Figure 17.15A-C
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17.16 Fungi absorb food after digesting it outside
their bodies
• Fungi are heterotrophic eukaryotes
– They digest their food externally and absorb the
nutrients
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• A fungus usually consists of a mass of
threadlike hyphae
– This forms a network called a mycelium
Hypha
Mycelium
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Figure 17.16A-B
• Most fungi cannot move
– But they grow around and through their food
very rapidly
Figure 17.16C, D
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17.17 Many fungi have three distinct phases in
their life cycle
• Fungal spores germinate to form haploid
hyphae
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• In some fungi such as mushrooms, the fusion
of hyphae results in a unique dikaryotic phase
of their life cycle
– Each cell contains two haploid nuclei from
different parents
• The dikaryotic mycelium forms a fruiting body,
the mushroom
– This structure contains specialized cells in
which the nuclei fuse
– These diploid cells then undergo meiosis,
producing a new generation of spores
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3 Spores
2 Diploid nuclei
released
1 Fruiting body
(mushroom)
Haploid
nucleus
DIPLOID
Spore
HAPLOID
DIKARYOTIC
4
Germination of spores
and growth of mycelia
6 Growth of
dikaryotic mycelium
5 Fusion of two hyphae
of compatible mating types
Figure 17.17
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17.18 Lichens consist of fungi living mutualistically
with photosynthetic organisms
• Lichens are associations of algae or
cyanobacteria with a network of fungal hyphae
– The fungus receives food in exchange for
housing, water, and minerals
Algal
cell
Fungal
hyphae
Figure 17.18A, B
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• Lichens survive in hostile environments
– They cover rocks and frozen tundra soil
Figure 17.18C
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17.19 Connection: Parasitic fungi harm plants and
animals
• Parasitic fungi cause disease
– Dutch elm disease
– Corn smut
– Athlete’s foot
Figure 17.19A-C
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17.20 Connection: Fungi have an enormous
ecological and practical impact
• Numerous fungi are beneficial
• Many are important in the decomposition of
organic material and nutrient recycling
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• Fungi are also important as food
– Mushrooms are the fruiting bodies of
subterranean fungi
– Yeasts (unicellular fungi) are essential for baking
and beer and wine production
– Fungi are used to ripen
certain cheeses
Figure 17.20A
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• Some fungi produce antibiotics
– Penicillin was the first antibiotic to be
discovered
Staphylococcus
aureus
Penicillium
Zone of
inhibited
growth
Figure 17.20B
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