Download 17. Plants, Fungi, and the Colonization of Land

Chapter 17
Plants, Fungi, and the
Colonization of Land
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plants and Fungi-A Beneficial Partnership
•
Mycorrhizae are mutually beneficial associations of
plant roots and fungi
– The fungi help plants obtain nutrients and water
and protect plant roots from parasites
– Sugars produced by the plant nourish the fungi
•
Modern agricultural practices often disrupt mycorrhizal
fungi, making fertilizers necessary
•
Beneficial relationships with fungi may have been
important as plants adapted to life on land
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PLANT EVOLUTION AND DIVERSITY
17.1 Plants evolved from green algae
• Plants and present-day green algae called
charophyceans probably evolved from a
common ancestor
– Morphological, biochemical, and genetic
similarities
• Adaptations enabling permanent life on land
appeared in ancestral green algae about 475
million years ago
– Early environment suitable for plant life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.2 Plants have adaptations for life on land
• Plants and algae are both multicellular
photosynthetic eukaryotes
• A set of derived characteristics distinguishes
plants as a clade
• Plants and algae interact differently with their
environments
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Key adaptations of plants to four challenges of
terrestrial life
– Obtaining resources from both soil and air
• Roots provide anchorage and absorb water
and minerals from soil
• Leaves absorb CO2 from the air
• Elongation of apical meristems maximizes
exposure to resources
• Vascular tissue (xylem and phloem)
connects subterranean and aerial parts
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• Supporting the plant body
– Lignin thickens and strengthens cell walls
• Maintaining moisture
– Waxy cuticle covering aerial parts prevents
direct gas exchange
– Stomata control gas exchange and prevent
water loss
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Reproducing on land
– Male and female gametangia (protective
jackets) surround gamete-producing cells
– Plants are embryophytes
• Fertilized egg develops into an embryo
while attached to and nourished by the
parent plant
– All plant life cycles have alternation of
generations
• Haploid spores are produced in protective
sporangia
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-2a
Plant
Reproductive structures (flowers)
contain spores and gametes
Leaf performs photosynthesis
Cuticle reduces water loss;
stomata allow gas exchange
Stem supports plant and may
perform photosynthesis
Surrounding water
supports alga
Roots
anchor plant;
absorb water and
minerals from
the soil
Whole alga
performs
photosynthesis;
absorbs water,
CO2, and
minerals from
the water
Holdfast
anchors alga
Alga
17.3 Plant diversity reflects the evolutionary
history of the plant kingdom
• Diversification of plants about 475 million years
ago gave rise to bryophytes
– Mosses, hornworts, and liverworts
– Lack vascular tissue
– Need to be covered with a film of water for
sperm to swim to egg
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Vascular plants originated about 420 million
years ago
– Have supportive vascular tissues
– Seedless vascular plants
• Lycophytes: club mosses
• Pterophytes: ferns and their relatives
– Well-developed roots and rigid stems
– Flagellated sperm that swim to eggs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Vascular plants with seeds evolved about 360
million years ago
– Seed: embryo packaged with food supply
within a protective covering
– Seed plant lineage accounts for over 90%
of plants living today
– Key adaptations of seed plants
• Seeds allow embryos to spread to diverse
habitats
• Pollen allows for passive transfer of sperm
to egg
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– Gymnosperms are among the earliest seed
plants
• Seeds not protected in specialized
chambers
• Largest clade comprises cone-bearing
confers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– Angiosperms (flowering plants) evolved
about 140 million years ago
• Flowers are complex reproductive structures
that develop seeds within protective ovaries
• The great majority of living plants are
angiosperms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Summary: Four key adaptations for life on land
distinguish the main lineages of the plant
kingdom
– Dependent embryos: all plants
– Lignified vascular tissues: all vascular
plants
– Seeds: gymnosperms and angiosperms
– Flowers: angiosperms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-3a
Land plants
Vascular plants
Bryophytes
(nonvascular plants)
Seedless vascular plants
Seed plants
Origin of seed plants
(about 360 mya)
Origin of vascular plants
(about 420 mya)
Origin of land plants
(about 475 mya)
ALTERNATION OF GENERATIONS AND
PLANT LIFE CYCLES
17.4 Haploid and diploid generations alternate in
plant life cycles
• Haploid gametophyte produces eggs and
sperm by mitosis
• Fertilization results in a diploid zygote
• Zygote develops into the diploid sporophyte,
which produces haploid spores by meiosis
• Spores grow into gametophytes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-4
Key
Haploid (n)
Gametophyte
plant (n)
Diploid (2n)
Sperm
Spores (n)
Gametes (n)
Meiosis
Egg
Fertilization
Zygote (2n)
Sporophyte
plant (2n)
17.5 Mosses have a dominant gametophyte
•
A mat of moss is mostly gametophytes, which
produce eggs and swimming sperm
1. Haploid gametes develop in gametangia
2. After fertilization, diploid zygote remains in
the gametophyte
3. Mitosis produces a smaller sporophyte,
which remains attached to the
gametophyte
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4. Meiosis in sporangia produces haploid
spores, which are released from
sporangium
5. Spores undergo mitosis and develop into
gametophytes
Animation: Moss Life Cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-5
Gametophytes (n)
Key
Haploid (n)
Diploid (2n)
Male
Mitosis and
development
Sperm (n) (released
from gametangium)
Spores (n)
Female
Egg (n)
Fertilization
Sporangium
Stalk
Meiosis
Sporophytes (growing
from gametophytes)
Zygote (2n)
Sporophyte (2n)
Mitosis and
development
17.6 Ferns, like most plants, have a dominant
sporophyte
1. Small haploid gametophyte produces sperm
that swim to the egg
2. Zygote remains on the gametophyte
3. Zygote undergoes mitosis and develops into
independent diploid sporophyte
4. Meiosis in sporangia produces haploid
spores
5. Spores are released and develop into
gametophytes by mitosis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-6
Key
Haploid (n)
Diploid (2n)
Sperm (n)
(released from male
gametangium)
Mitosis and
development
Spores (n)
Female
gametangium (n)
Gametophyte (n)
(underside)
Egg (n)
Fertilization
Meiosis
Clusters of
sporangia
Zygote (2n)
New sporophyte (2n)
growing out of
gametophyte
Mitosis and
development
Mature sporophyte
(independent of gametophyte)
Animation: Fern Life Cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.7 Seedless plants dominated vast "coal forests"
•
Ferns and lycophytes were once the dominant plants
on Earth
•
Tropical swamp forests of the Carboniferous period
generated a lot of organic matter
– Their remains formed the fossil fuels peat and coal
•
After the Carboniferous period, climate change
provided opportunities for seed plants
– Gymnosperms dominated through the Mesozoic
era
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.8 A pine tree is a sporophyte with tiny
gametophytes in its cones
•
Roles of haploid and diploid generations
changed drastically as plants evolved on land
•
All reproductive stages of conifers are on
sporophytes in cones; ovule is the key
adaptation
1. Ovulate cone has scales bearing ovules
2. Smaller pollen cones make haploid
spores that develop into pollen grains
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3. Pollination occurs; meiosis occurs in a
spore mother cell in the ovule
4. One surviving haploid spore develops into
the female gametophyte
5. Tube grows out of each pollen grain and
releases sperm near an egg
6. Zygote develops into sporophyte embryo;
ovules transform into seeds
7. Seeds disperse, germinate; embryo grows
into seedling
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-8
A haploid spore cell in
ovule develops into
female gametophyte,
which makes eggs.
Scale
Ovulate cone
bears ovules.
Ovule
Pollen grains (male
gametophytes) (n)
Female gametophyte (n)
Meiosis
Sporangium (2n)
Spore mother cell (2n)
Integument
Eggs (n)
Pollination
Male gametophyte
(pollen) grows tube
to egg and makes
and releases sperm.
Sperm (n)
Fertilization
Male gametophyte
(pollen grain)
Meiosis
Sporangia in pollen cone
produce spores by meiosis;
spores develop into pollen
grains.
Mature sporophyte
Seed coat
Embryo
(2n)
Zygote
(2n)
Food
supply
Zygote develops
into embryo, and
ovule becomes seed.
Key
Haploid (n)
Diploid (2n)
Seed germinates,
and embryo grows
into seedling.
Seed
Animation: Pine Life Cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.9 The flower is the centerpiece of angiosperm
reproduction
• Flowers are the site of pollination and
fertilization
– Generate fruits, which contain seeds
• A flower is a short stem with modified leaves
– Sepals enclose flower before it opens
– Petals are important in attracting pollinators
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
– Reproductive structures
• Stamen: a stalk bearing an anther in which
pollen grains develop
• Carpel: a stalk with an ovary and a sticky
stigma that traps pollen
• Ovary: protective chamber containing
ovules in which eggs develop
Video: Flower Blooming Time Lapse
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-9b
Stigma
Anther
Style
Stamen
Ovary
Filament
Petal
Sepal
Ovule
Receptacle
Carpel
17.10 The angiosperm plant is a sporophyte with
gametophytes in its flowers
•
•
The angiosperm life cycle differs in two main
ways from the gymnosperm life cycle
–
Gametophytes develop in flowers
–
Seeds are produced in an ovary and
packaged inside a fruit
Steps of the angiosperm life cycle
1. Meiosis and mitosis in anther result in
male gametophytes (pollen grains)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
2. Meiosis and mitosis in ovule lead to female
gametophytes, one of which becomes an
egg
3. Tube grows from pollen grain, carries
sperm to egg in ovule
4. Zygote forms
5. A seed develops from each ovule
6. Ovary's wall thickens, forming fruit
7. Seed germinates, embryo grows and
develops into mature sporophyte
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-10
Haploid spores in anthers
develop into pollen grains:
male gametophytes.
Pollen grains (n)
Pollination and
growth of
pollen tube
Meiosis
Stigma
Haploid spore in each ovule
develops into female gametophyte,
which produces egg.
Stigma
Anther
Pollen grain
Pollen tube
Meiosis
Egg (n)
Ovule
Ovary
Ovule
Sporophyte (2n)
Sperm
Seed germinates,
and embryo
grows into
plant.
Seeds
Food
supply
Fruit
(mature ovary)
Key
Haploid (n)
Diploid (2n)
Fertilization
Seed
coat
Seed
Embryo
(2n)
Zygote
(2n)
Video: Flowering Plant Life Cycle (time lapse)
Animation: Fruit Development
Animation: Plant Fertilization
Animation: Seed Development
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.11 The structure of a fruit reflects its function
in seed dispersal
• Fruits are adaptations that disperse seeds
– Largely depend on wind and animals for
dispersal
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CONNECTION
17.12 Agriculture is based almost entirely on
angiosperms
• Angiosperms provide most of our food and
other important commercial products
• Humans intervened in plant evolution by
selectively breeding to improve quality
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.13 Interactions with animals have profoundly
influenced angiosperm evolution
• Angiosperms are a major source of food for
land animals
• Most angiosperms depend on animals to aid in
pollination
• Coevolution is the mutual evolutionary
influence between two species
– Various plant and animal adaptations
benefit both species
• Examples: color, shape, timing
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Video: Bee Pollinating
Video: Bat Pollinating Agave Plant
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CONNECTION
17.14 Plant diversity is a nonrenewable resource
•
Plant biodiversity is being reduced at an
unprecedented rate
– The threat is especially noteworthy in forests
– The majority of plant genetic diversity is found in
the world's rain forests
•
What is lost is irreplaceable
– Medicinal plants, food, timber, clean water and air,
animal habitat
•
Efforts are underway to develop sustainable forest
management
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
FUNGI
17.15 Fungi absorb food after digesting it outside
their bodies
• Fungi are heterotrophic eukaryotes that digest
their food externally and absorb the nutrients
– Like animals, must obtain organic
molecules from other organisms
• Fungi are vital as mycorrhizal partners of
plants and as decomposers
• Fungi are found virtually everywhere
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Fungi usually consist of a mass of threadlike
hyphae
– Branch repeatedly into a feeding structure
called a mycelium
– Are surrounded by a cell wall made of chitin
– Grow at a phenomenal rate, extending into
new territory
– Develop a huge surface area for digesting
food
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-15b
Hypha
Mycelium
17.16 Fungi produce spores in both asexual and sexual
life cycles
•
Many fungal species can reproduce sexually or
asexually
•
Many sexually reproducing fungi have a heterokaryotic
phase
– Fusion of haploid hyphae produces cells containing
nuclei from two parents
– After varying lengths of time, parent nuclei fuse and
form short-lived diploid phase
– Haploid spores are produced by meiosis in
specialized structure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-16
Key
Heterokaryotic
stage
Haploid (n)
Heterokaryotic (n + n)
(unfused nuclei)
Diploid (2n)
Fusion of nuclei
Fusion of cytoplasm
Zygote
(2n)
Spore-producing
structures
Spores
(n)
Asexual
reproduction
Sexual
reproduction
Meiosis
Mycelium
Spore-producing
structures
Germination
Germination
Spores (n)
Animation: Fungal Reproduction and Nutrition
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Asexually reproducing fungi
– Molds: fungi that reproduce by producing
spores, often at the tips of specialized
hyphae
– Yeast: single-celled fungi that reproduce by
cell division or budding
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.17 Fungi can be classified into five groups
• Fungi probably evolved from an aquatic,
flagellated ancestor shared with animals
– Animals and fungi diverged about 1.5 billion
years ago
• Fungi classification is often based on sexual
reproductive structures
– Those with no known sexual stage are
called imperfect fungi
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-17a
• Most biologists recognize five groups of fungi
– Chytrids
• Have flagellated spores
• Decomposers and parasites
– Zygomycetes
• Form haploid spores in resistant
zygosporangia
• Fast-growing molds such as black bread
mold; animal parasites
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• Glomeromycetes
– Similar to zygomycetes but genetically
distinct
– Form distinctive mycorrhizae with treelike
arbuscules
• Ascomycetes (sac fungi)
– Have saclike asci that produce spores in
sexual reproduction
– Some devastating plant pathogens; part of
symbiotic lichens
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• Basidiomycetes (club fungi)
– Have a club-shaped spore-producing
basidium
– Mushrooms, puffballs, shelf fungi
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Video: Allomyces Zoospore Release
Video: Phlyctochytrium Zoospore Release
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.18 Fungal groups differ in their life cycles and
reproductive structures
• Much of the success of fungi is due to their
reproductive capacity
• Black bread mold life cycle is typical of
zygomycetes
– As hyphae expand through its food, the
fungus reproduces asexually
– When the food is depleted, the fungus
reproduces sexually
– Ascomycetes are similar
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-18a
Key
Haploid (n)
Heterokaryotic (n + n)
Zygosporangium (n  n)
Diploid (2n)
Mycelia of
different
mating types
Cells fuse
Fusion of
nuclei
Young
zygosporangium
(heterokaryotic)
Meiosis
Sporangium
Spores
(n)
•
The life cycle of a basidiomycete has five
stages
1. A heterokaryotic mycelium forms by fusion
of two different mating types
2. A mushroom develops and grows
3. Specialized cells from the gills contain the
diploid nuclei from nuclei fusion
4. Haploid spores are formed by meiosis and
then released
5. Germination takes place, and a haploid
mycelium grows
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-18b
Key
Diploid nuclei
Haploid (n)
Heterokaryotic (n+n)
Fusion of
nuclei
Meiosis
Diploid (2n)
Basidia
Spores
released
Haploid
nuclei
Spores (n)
Mushroom
Germination of spores
and growth of mycelia
Growth of
heterokaryotic mycelium
Fusion of two hyphae
of different mating types
CONNECTION
17.19 Parasitic fungi harm plants and animals
• Of 100,000 known species of fungi, about 30%
are parasites, mostly of plants
– Fungi have changed landscapes
• Example: Dutch elm disease
– Fungi are serious agricultural pests
• Example: corn smut, ergot
– A mycosis is a fungal infection of animals
• Examples: ringworm, vaginal yeast
infections
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
17.20 Lichens consist of fungi living
mutualistically with photosynthetic organisms
• Lichens consist of algae or cyanobacteria held
in a mass of fungal hyphae
– Fungus receives food from the
photosynthesis of its partner
– Alga or cyanobacterium receives housing,
water, and the minerals trapped by the
hyphal network
• Lichens are able to live in difficult conditions
but cannot withstand air pollution
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-20b
Fungal hyphae
Colorized SEM 1,000
Algal cell
17.21 Fungi also form mutualistic relationships
with animals
• The digestive abilities of fungi benefit some
animals
– Break down plant material in guts of grazing
animals
– Digest plants in ant or termite "farms"
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CONNECTION
17.22 Fungi have enormous ecological benefits
and practical uses
• As mycorrhizae, fungi supply essential
nutrients to plants
• Fungi are essential decomposers in
ecosystems
– Consume almost any carbon-containing
substance
• Fungi also have practical uses for humans
– Provide antibiotics and food
– Are useful in research
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 17-22b
Staphylococcus
aureus
Penicillium
Zone of
inhibited
growth