Download PLANT EVOLUTION AND DIVERSITY

Introduction
ƒ The Venus flytrap (捕蠅草) has adaptations to
– capture and
– digest insects.
ƒ More than 600 species of plants
– are carnivores and
– typically live where soil nutrients, including nitrogen levels,
are poor.
ƒ Carnivorous plants absorb and use nutrients,
including nitrogen, from animals.
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Big Ideas
PLANT EVOLUTION
AND DIVERSITY
Plant Evolution
and Diversity
Alternation of
Generations and Plant
Life Cycles
Diversity of Fungi
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Plants have adaptations for life on land
ƒ More than 500 million years ago, the algal
ancestors of plants may have carpeted moist
fringes of lakes and coastal salt marshes.
ƒ Plants and green algae called charophytes
– are thought to have evolved from a common ancestor,
– have complex multicellular bodies, and
– are photosynthetic eukaryotes.
Chara (輪藻), an elaborate charophyte
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Plants have adaptations for life on land
ƒ Life on land offered many opportunities for plant
adaptations that took advantage of
– unlimited sunlight,
– abundant CO2, and
– initially, few pathogens or herbivores.
Coleochaete (鞘毛藻屬), a simple charophyte
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Plants have adaptations for life on land
Plants have adaptations for life on land
ƒ But life on land had disadvantages too. On land,
plants must
ƒ Unlike land plants, algae
– generally have no rigid tissues,
– maintain moisture inside their cells, to keep from drying
out,
– are supported by surrounding water,
– support their body in a nonbuoyant medium,
– obtain CO2 and minerals directly from the water
surrounding the entire algal body,
– reproduce and disperse offspring without water, and
– receive light and perform photosynthesis over most of
their body,
– obtain resources from soil and air.
– use flagellated sperm that swim to fertilize an egg, and
– disperse offspring by water.
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Plants have adaptations for life on land
ƒ Land plants maintain moisture in their cells using
Key
Vascular
tissue
Pollen
Spores
– a waxy cuticle (表皮) and
Leaf
Spores
Flagellated
sperm
Alga
Surrounding
water supports
alga. Whole alga
Leaf
performs photosynthesis; absorbs Stem
water, CO2, and
minerals from
the water.
Roots
Flagellated
sperm
Holdfast
(anchors alga)
Seed
– cells that regulate the opening and closing of stomata.
Flagellated
sperm
Stem
ƒ Land plants obtain
Leaf
Roots
Moss
Stomata only on sporophytes;
primitive roots anchor plants;
no lignin; no vascular tissue;
fertilization requires moisture
Fern
Stomata; roots anchor
plants, absorb water;
lignified cell walls;
vascular tissue;
fertilization requires
moisture
Stem
– water and minerals from roots in the soil and
Roots
Pine tree
Stomata;
roots anchor plants, absorb water;
lignified cell walls; vascular tissue;
fertilization does not require moisture
– CO2 from the air and sunlight through leaves.
ƒ Growth-producing regions of cell division, called
apical meristems (尖端分生組織), are found near
the tips of stems and roots.
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Plants have adaptations for life on land
ƒ In many land plants, water and minerals move up
from roots to stems and leaves using vascular
tissues.
– Xylem (木質部)
– consists of dead cells and
– conveys water and minerals.
– Phloem (韌皮部)
The network of veins in a leaf
– consists of living cells and
– conveys sugars.
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Plants have adaptations for life on land
Leaves carry out photosynthesis.
Reproductive structures, as in flowers,
contain spores and gametes.
ƒ Many land plants support their body against the pull
of gravity using lignin (木質素).
Cuticle covering leaves and stems
reduces water loss.
Stomata in leaves allow gas exchange
between plant and atmosphere.
ƒ The absence of lignified cell walls in mosses and
other plants that lack vascular tissue limits their
height.
Lignin hardens cell walls of some
plant tissues.
Stem supports plant; may perform
photosynthesis.
Vascular tissues in shoots and roots
transport water, minerals, and sugars;
provide support.
Roots anchor plant; mycorrhizae (rootfungus associations) help absorb water
and minerals from the soil.
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Plants have adaptations for life on land
Plant diversity reflects the evolutionary history of
the plant kingdom
ƒ In all plants, the
ƒ Four key adaptations for life on land distinguish the
main lineages of the plant kingdom.
– gametes and embryos must be kept moist,
– fertilized egg (zygote) develops into an embryo while
attached to and nourished by the parent plant, and
– life cycle involves an alternation of a
– haploid generation, which produces eggs and sperm, and
– diploid generation, which produces spores within protective
structures called sporangia (孢子囊).
– Dependent embryos are present in all plants.
– Lignified vascular tissues mark a lineage (族系) that gave
rise to most living plants.
– Seeds are found in a lineage that includes all living
gymnosperms (裸子植物) and angiosperms (被子植物).
– Flowers mark the angiosperm lineage.
ƒ Pines and flowering plants have pollen grains,
structures that contain the sperm-producing cells.
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Liverworts (地錢)
Origin of land plants
(about 475 mya)
Hornworts (角蘚)
1
Land plants
Nonvascular
plants
(bryophytes)
Ancestral
green
alga
Mosses (苔蘚)
Pterophytes 蕨 (ferns,
horsetails, whisk ferns)
Seed
plants
Gymnosperms
3
Vascular plants
Lycophytes 石松 (club mosses,
spike mosses, quillworts)
Origin of vascular plants
(about 425 mya)
Seedless
vascular
plants
2
Origin of seed plants
(about 360 mya)
Angiosperms
500
450
400
350
300
0
Millions of years ago (mya)
Ancestral
green
alga
Plant diversity reflects the evolutionary history of
the plant kingdom
Origin of land plants
(about 475 mya)
ƒ Early diversification of plants gave rise to seedless,
nonvascular plants called bryophytes (苔蘚植物),
including
1
– mosses,
2
Origin of vascular plants
(about 425 mya)
– liverworts, and
– hornworts.
3
500
Origin of seed plants
(about 360 mya)
450
400
350
Millions of years ago (mya)
300
0
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Bryophytes
(seedless, nonvascular plants)
Plant diversity reflects the evolutionary history of
the plant kingdom
ƒ These plants resemble (類似) other plants in having
apical meristems and embryos retained (保有) on the
parent plant, but they lack
– true roots,
– leaves, and
– lignified cell walls.
Moss
Liverwort
Hornwort
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Plant diversity reflects the evolutionary history of
the plant kingdom
Seedless vascular plants
ƒ About 425 million years ago, vascular plants evolved
with lignin-hardened vascular tissues.
ƒ The seedless vascular plants include
– lycophytes (石松) (including club mosses 石松) and
– pterophytes (蕨) (ferns and their relatives).
Fern (a pterophyte)
Club moss (a lycophyte).
Spores are produced in the
upright tan-colored (黃褐色) structures.
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Plant diversity reflects the evolutionary history of
the plant kingdom
Plant diversity reflects the evolutionary history of
the plant kingdom
ƒ The first vascular plants with seeds evolved about
360 million years ago.
ƒ Vascular plants with seeds include
ƒ A seed consists of an embryo packaged with a food
supply within a protective covering.
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– gymnosperms (including ginkgo, cycad 蘇鐵, and conifer
species) and
– angiosperms (such as flowering trees and grasses).
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Angiosperms
Gymnosperms
Cycad
Ginkgo
Ephedra (麻黃)
(Mormon tea)
A conifer
A jacaranda (藍花楹) tree
Barley (大麥), a grass
5
Haploid and diploid generations alternate in
plant life cycles
ALTERNATION
OF GENERATIONS
AND PLANT LIFE CYCLES
ƒ Plants have an alternation of generations in
which the haploid and diploid stages are distinct,
multicellular bodies.
– The haploid gametophyte produces gametes (eggs or
sperm) by mitosis.
– Fertilization results in a diploid zygote.
– The zygote develops into the diploid sporophyte, which
produces haploid spores by meiosis.
– Spores grow into gametophytes.
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Gametophyte
plant (n)
Gametophyte
plant (n)
Sperm
Sperm
Gametes (n)
Gametes (n)
Egg
Egg
Fertilization
Zygote (2n)
Key
Haploid (n)
Diploid (2n)
Key
Haploid (n)
Diploid (2n)
Gametophyte
plant (n)
Gametophyte
plant (n)
Sperm
Sperm
Gametes (n)
Egg
Fertilization
Gametes (n)
Egg
Fertilization
Meiosis
Zygote (2n)
Zygote (2n)
Sporophyte
plant (2n)
Spores
(n)
Key
Haploid (n)
Diploid (2n)
Sporophyte
plant (2n)
Key
Haploid (n)
Diploid (2n)
6
The life cycle of a moss is dominated by the
gametophyte
Gametophyte
plant (n)
ƒ Gametophytes make up a bed of moss.
Sperm
Spores
(n)
Gametes (n)
– Gametes develop in male and female gametangia (配子
囊).
Egg
Fertilization
Meiosis
– Sperm swim through water to the egg in the female
gametangium.
Zygote (2n)
Key
Haploid (n)
Diploid (2n)
Sporophyte
plant (2n)
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The life cycle of a moss is dominated by the
gametophyte
Gametophytes (n)
Male
ƒ The zygote
Sperm (n)
1
– develops within the gametangium into a mature
sporophyte,
– which remains attached to the gametophyte.
Female
1
Female
gametangium
Egg (n)
Fertilization
ƒ Meiosis occurs in sporangia at the tips of the
sporophyte stalks.
ƒ Haploid spores are released from the sporangium
and develop into gametophyte plants.
Key
Haploid (n)
Diploid (2n)
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Gametophytes (n)
Gametophytes (n)
Male
Male
Sperm (n)
Sperm (n)
1
Female
1
1
Female
gametangium
Egg (n)
Fertilization
Female
1
Female
gametangium
Egg (n)
Sporangium
Fertilization
Stalk
2
2
Zygote (2n)
Key
Haploid (n)
Diploid (2n)
Zygote (2n)
Sporophyte (2n)
3
Mitosis and
development
Key
Haploid (n)
Diploid (2n)
7
Gametophytes (n)
Gametophytes (n)
Male
5
Sperm (n)
Mitosis and
development
Male
Sperm (n)
1
Spores (n)
1
Female
1
Female
gametangium
Egg (n)
Sporangium
Spores (n)
Female
Sporangium
Fertilization
Stalk
Female
gametangium
Egg (n)
1
Fertilization
Stalk
2
2
Zygote (2n)
Sporophyte (2n)
Zygote (2n)
Sporophyte (2n)
Meiosis
Meiosis
4
3
Mitosis and
development
Key
Haploid (n)
Diploid (2n)
Figure 17.4_6
Key
Haploid (n)
Diploid (2n)
4
3
Mitosis and
development
Ferns, like most plants, have a life cycle
dominated by the sporophyte
ƒ Fern gametophytes are small and inconspicuous (不
起眼).
ƒ Gametophytes produce flagellated sperm that swim
to the egg and fertilize it to produce a zygote.
ƒ The zygote initially develops within the female
gametangia but eventually (最終) develops into an
Moss sporangia
independent sporophyte.
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Ferns, like most plants, have a life cycle
dominated by the sporophyte
1
2
ƒ Sporangia develop on the underside of the leaves
of the sporophyte.
ƒ Within the sporangia, cells undergo meiosis to
produce haploid spores.
Sperm (n)
Gametophyte (n)
Female
gametangium (n)
Egg (n)
Fertilization
ƒ Spores are released and develop into
gametophytes.
Key
Haploid (n)
Diploid (2n)
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8
1
1
2
2
Sperm (n)
Gametophyte (n)
Sperm (n)
Gametophyte (n)
Female
gametangium (n)
Female
gametangium (n)
Egg (n)
Egg (n)
Fertilization
Fertilization
Clusters of
sporangia
5
Zygote (2n)
Zygote (2n)
4
Key
Haploid (n)
Diploid (2n)
Mature sporophyte
3 Mitosis and
development
New sporophyte (2n) Key
Haploid (n)
Diploid (2n)
Gametophyte (n)
1
2
6
Mitosis and
development
Sperm (n)
Gametophyte (n)
Female
gametangium (n)
Spores (n)
Egg (n)
Fertilization
Meiosis
Clusters of
sporangia
5
Zygote (2n)
4
Mature sporophyte
3 Mitosis and
development
New sporophyte (2n) Key
Haploid (n)
Gametophyte (n)
Diploid (2n)
Fern sporangia
Seedless vascular plants dominated vast (廣闊)
“coal forests”
Seedless vascular plants dominated vast (廣闊)
“coal forests”
ƒ Two groups of seedless plants formed vast ancient
forests in low-lying wetlands during the
Carboniferous (石炭紀) period (360–299 million
years ago):
ƒ Coal, oil, and natural gas are fossil fuels.
– lycophytes (such as club mosses) and
– pterophytes (such as ferns).
– Oil and natural gas formed from marine organisms.
– Coal formed from seedless plants.
ƒ Burning fossil fuels releases CO2 and other
greenhouse gases into the atmosphere, which are
now causing a warming climate.
ƒ When these plants died, they formed peat (泥炭)
deposits that eventually formed coal.
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9
Seedless vascular plants dominated vast (廣闊)
“coal forests”
ƒ As temperatures dropped during the late
Carboniferous,
– glaciers formed,
– the climate turned drier,
– the vast swamps and forests began to disappear, and
– wind-dispersed pollen and protective seeds gave seed
plants a competitive advantage.
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A pine tree is a sporophyte with gametophytes in
its cones
A pine tree is a sporophyte with gametophytes in
its cones
ƒ A pine tree is a sporophyte.
ƒ Tiny gametophytes grow in sporophyte cones.
ƒ The ovule (胚珠) is a key adaptation, a protective
device for all the female stages in the life cycle, as
well as the site of
ƒ A sperm from a pollen grain fertilizes an egg in the
female gametophyte.
ƒ The zygote develops into a sporophyte embryo.
ƒ The ovule becomes the seed with
– pollination,
– stored food and
– fertilization, and
– a protective seed coat.
– embryonic development.
ƒ The seed is a key adaptation for life on land and a
major factor in the success of seed plants.
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Spore
mother
cell (2n)
Ovulate cone
Spore
mother
cell (2n)
Ovulate cone
Scale
Scale
4
3
2
Longitudinal
section
4
Ovule
Pollination
3
2
Sporangium (2n)
Longitudinal
section
Meiosis
Integument
Ovule
Pollination
Sporangium (2n)
Meiosis
Integument
Pollen
cone
Pollen
cone
Meiosis
Female gametophyte (n)
Meiosis
Male gametophyte
(pollen grain)
5
Sperm (n)
Male gametophyte
(pollen grain)
1
1
Longitudinal section
Longitudinal section
A mature sporophyte
Eggs (n)
A mature sporophyte
Key
Haploid (n)
Diploid (2n)
Key
Haploid (n)
Diploid (2n)
10
Spore
mother
cell (2n)
Ovulate cone
Spore
mother
cell (2n)
Ovulate cone
Scale
Scale
4
4
3
2
Ovule
Pollination
3
2
Longitudinal
section
Sporangium (2n)
Longitudinal
section
Sporangium (2n)
Meiosis
Integument
Pollen
cone
Meiosis
5
Sperm (n)
Female gametophyte (n)
5
Sperm (n)
Male gametophyte
(pollen grain)
Male gametophyte
(pollen grain)
Eggs (n)
1
Meiosis
Integument
Pollen
cone
Female gametophyte (n)
Meiosis
Ovule
Pollination
Eggs (n)
1
Longitudinal section
Longitudinal section
A mature sporophyte
A mature sporophyte
Seed coat
Seed
Seed coat
Embryo (2n)
Food supply
6
7
Seed
Zygote
(2n)
Embryo (2n)
Food supply
6
8
Key
Haploid (n)
Diploid (2n)
7
Key
Haploid (n)
Diploid (2n)
The flower is the centerpiece of angiosperm
reproduction
The flower is the centerpiece of angiosperm
reproduction
ƒ Flowers house separate male and female sporangia
and gametophytes.
ƒ Flowers usually consist of
ƒ Flowers are the sites of
– pollination and
– fertilization.
Zygote
(2n)
– sepals (萼片), which enclose the flower before it opens,
– petals, which attract animal pollinators,
– stamens (花蕊), which include a filament and anther (花
藥), a sac at the top of each filament that contains male
sporangia and releases pollen, and
– carpels, the female reproductive structure, which
produce eggs.
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The flower is the centerpiece (核心) of angiosperm
reproduction
ƒ Ovules develop into seeds.
ƒ Ovaries mature into fruit.
Some examples of floral diversity
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11
The angiosperm plant is a sporophyte with
gametophytes in its flowers
Stigma (柱頭)
Style (花柱)
Carpel (心皮)
Ovary
ƒ Key events in a typical angiosperm life cycle
1. Meiosis in the anthers produces haploid spores that form
the male gametophyte (pollen grains).
Anther
Stamen
Filament
Petal
2. Meiosis in the ovule produces a haploid spore that forms
the few cells of the female gametophyte, one of which
becomes the egg.
3. Pollination occurs when a pollen grain lands on the
stigma. A pollen tube grows from the pollen grain to the
ovule.
Sepal
Ovule
Receptacle
(花托)
4. The tube carries a sperm that fertilizes the egg to form a
zygote.
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The angiosperm plant is a sporophyte with
gametophytes in its flowers
1
Pollen grains (n)
(male gametophytes)
Meiosis
ƒ Key events in a typical angiosperm life cycle,
continued
Egg within
a female
gametophyte (n)
2
Meiosis
5. Each ovule develops into a seed, consisting of
– an embryo (a new sporophyte) surrounded by a food supply and
Ovule
– a seed coat derived from the integuments (珠被; 外種皮).
6. While the seeds develop, the ovary’s wall thickens,
forming the fruit that encloses the seeds.
7. When conditions are favorable, a seed germinates (發芽).
Key
Haploid (n)
Diploid (2n)
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1
Pollen grains (n)
(male gametophytes)
Meiosis
2
1
3
Egg within
a female
gametophyte (n)
Pollen grains (n)
(male gametophytes)
Meiosis
Stigma
Pollen grain
Pollen tube
Meiosis
2
3
Egg within
a female
gametophyte (n)
Stigma
Pollen grain
Pollen tube
Meiosis
Ovule
Ovule
Sperm
Sperm
Fertilization
Fertilization
4
Key
Haploid (n)
Diploid (2n)
Zygote
(2n)
Key
Haploid (n)
Diploid (2n)
12
1
Pollen grains (n)
(male gametophytes)
Meiosis
2
Anther
1
Pollen grains (n)
(male gametophytes)
Meiosis
3
Stigma
Egg within
a female
gametophyte (n)
Pollen grain
Pollen tube
2
Meiosis
3
Egg within
a female
gametophyte (n)
Stigma
Pollen grain
Pollen tube
Meiosis
Ovary
Ovule
Sporophyte
(2n)
Sperm
Ovule
Ovule
containing
female sporangium
(2n)
Sperm
7
Seeds
Seeds
Food
supply
6
Fruit
(mature
ovary)
Seed
coat
5
Seed
Embryo (2n)
Food
supply
6
Fertilization
Fruit
(mature
ovary)
4
Zygote
(2n)
Key
Haploid (n)
Diploid (2n)
Seed
coat
5
Seed
Embryo (2n)
Fertilization
4
Zygote
(2n)
Key
Haploid (n)
Diploid (2n)
The structure of a fruit reflects its function in
seed dispersal
ƒ Fruits are
– ripened ovaries of flowers and
– adaptations that disperse seeds.
Fruit
ƒ Seed dispersal mechanisms include relying on
– wind,
– hitching a ride on animals, or
Seed
dispersal
– fleshy, edible (可食用) fruits that attract animals, which
then deposit the seed in a supply of natural fertilizer at
some distance from the parent plant.
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Angiosperms sustain us—and add spice to our
diets
ƒ Most human food is provided by the fruits and
seeds of angiosperms.
– Corn, rice, wheat, and other grains are dry fruits.
– Apples, cherries, tomatoes, and squash (葫蘆瓜) are
fleshy fruits.
– Spices such as nutmeg (肉荳蔻), cinnamon, cumin (小茴
香), cloves (丁香), ginger, and licorice are also
angiosperm fruits.
Berries (fruits) on Piper nigrum
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13
Pollination by animals has influenced angiosperm
evolution
ƒ About 90% of angiosperms use animals to transfer
their pollen.
– Birds are usually attracted by colorful flowers, but not
scent.
– Most beetles are attracted by fruity odors, but are
indifferent to color.
– Night-flying bats and moths are usually attracted by
large, highly scented flowers.
– Wind-pollinated flowers typically produce large amounts
of pollen.
Flowers of red maple, whose pollen is carried by the wind
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Showy (艷麗的) columbine flower (耬斗花)
A bee picking up pollen from a scotch broom flower (金雀
花) as it feeds on nectar
Plant diversity is vital (攸關) to the future of the
world’s food supply
ƒ Early hunter-gatherer (採集者) humans made use of
any edible plant species available at the time.
ƒ Modern agriculture has narrowed the pool of food
plant diversity by creating a select few genotypes.
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14
Plant diversity is vital (攸關) to the future of the
world’s food supply
Plant diversity is vital (攸關) to the future of the
world’s food supply
ƒ Most of the world’s population is now fed by
varieties of
ƒ As plant biodiversity is lost through extinction and
– rice,
habitat destruction, we lose
– potential crop species and
– wheat,
– corn, and
– valuable genes.
– soybeans.
– Agriculture has changed the landscape.
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Sugar plums (left) and safou (right), two wild fruits that may
be ripe for domestication (馴化)
Amazonian rain forest
DIVERSITY OF FUNGI
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15
Fungi absorb food after digesting it outside their
bodies
Fungi absorb food after digesting it outside their
bodies
ƒ Fungi
– are absorptive heterotrophic eukaryotes,
ƒ Most fungi consist of a mass of threadlike hyphae
(菌絲) making up a mycelium (菌絲體).
– secrete powerful enzymes to digest their food externally,
ƒ Hyphal cells
and
– acquire their nutrients by absorption.
– are separated by cross-walls with pores large enough for
ribosomes, mitochondria, and nuclei to cross,
– are sometimes multinucleate without cross-walls, and
– have a huge surface area to secrete digestive enzymes
and absorb food.
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© 2012 Pearson Education, Inc.
Figure 17.14B
Reproductive
structure
Hyphae
Spore-producing
structures (tips of hyphae)
Mycelium
Fungi absorb food after digesting it outside their
bodies
ƒ Fungal hyphae
– are surrounded by a cell wall made of chitin instead of
cellulose (纖維素).
ƒ Some fungi
– are parasites and
– obtain their nutrients at the expense of living plants or
animals.
Animation: Fungal Reproduction and Nutrition
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16
Fungi absorb food after digesting it outside their
bodies
Fungi produce spores in both asexual and sexual
life cycles
ƒ Mycorrhizae (plural)
ƒ Fungi produce huge numbers of asexual spores,
each of which can germinate to form a new fungus.
– represent a symbiotic relationship between fungi and
plant root cells and
– are present in nearly all vascular plants.
ƒ Mycorrhizal fungi absorb phosphorus and other
essential materials from the soil and make them
available to the plant.
ƒ Sugars produced by the plant through
photosynthesis nourish the mycorrhizal fungi.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Fungi produce spores in both asexual and sexual
life cycles
Fungi produce spores in both asexual and sexual
life cycles
ƒ In many fungi, sexual fusion of haploid hyphae
leads to a heterokaryotic stage, in which cells
contain two genetically distinct haploid nuclei.
ƒ In asexual reproduction, spore-producing structures
arise from haploid mycelia that have undergone
neither a heterokaryotic stage or meiosis.
– Hours or centuries may pass before parental nuclei fuse
to form a short-lived diploid phase.
ƒ Many fungi that reproduce sexually can also
produce spores asexually.
– Zygotes undergo meiosis to produce haploid spores.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Fungi produce spores in both asexual and sexual
life cycles
Key
Haploid (n)
Heterokaryotic (n + n)
(unfused nuclei)
Diploid (2n)
Fusion of nuclei
1
Fusion of cytoplasm
Spore-producing
structures
Spores
(n)
2
Sexual
reproduction
Asexual Mycelium
reproduction
4
ƒ Molds (黴) are any rapidly growing fungus that
reproduces asexually by producing spores.
Heterokaryotic
stage
Zygote
(2n)
ƒ Yeasts are single-celled fungi that reproduce
asexually by cell division or budding.
Meiosis
Spore-producing
structures
Germination
3
Germination
Spores (n)
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Fungi are classified into five groups
Fungi are classified into five groups
ƒ There are over 100,000 described fungi species.
ƒ Suspected but as yet undescribed species may
number as many as 1.5 million.
ƒ Sexual reproductive structures are often used to
classify fungi.
ƒ Fungi and animals may have diverged
ƒ Chytrids (壺菌) are the
– from a flagellated unikont ancestor
– only fungi with flagellated spores and
– earliest lineage of fungi.
ƒ Chytrid fungi are
– common in lakes, ponds, and soil and
– linked to the widespread decline of amphibian species.
– more than 1 billion years ago.
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Fungi are classified into five groups
Chytrids
(壺菌)
ƒ Zygomycetes, or zygote fungi (接合菌)
Zygomycetes
(zygote fungi)
(接合菌)
Glomeromycetes
(arbuscular
mycorrhizal fungi)
(球囊菌)
Ascomycetes
(sac fungi)
(原囊菌)
– are characterized by their protective zygosporangium
(接合孢子囊), where zygotes produce haploid spores
by meiosis.
– This diverse group includes fast-growing molds that
attack
– bread
– peaches,
– strawberries,
Basidiomycetes
(club fungi)
(擔子菌)
– sweet potatoes, and
– some animals.
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Fungi are classified into five groups
ƒ Glomeromycetes (球囊菌)
– form a distinct type of mycorrhizae, in which hyphae that
invade plant roots branch into treelike structures known
as arbuscules (叢枝體).
– About 90% of all plants have symbiotic partnerships with
glomeromycetes.
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Figure 17.16C
Fungi are classified into five groups
ƒ Ascomycetes (原囊菌), or sac fungi
– form saclike structures called asci (菌囊), which
produce spores in sexual reproduction,
– live in marine, freshwater, and terrestrial habitats, and
– range in size from unicellular years to elaborate (綿密)
morels (羊肚菌) and cup fungi.
Glomeromycete: an arbuscule in a root cell
– Some ascomycetes live with green algae or
cyanobacteria in symbiotic associations called lichens.
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Ascomycetes
Edible morels
Cup fungus
Fungi are classified into five groups
ƒ Basidiomycetes, or club fungi (擔子菌),
Figure 17.16E
Basidiomycetes
Mushrooms
– include common mushrooms, puffballs (馬勃), and
shelf fungi (托架真菌) and
– are named for their club-shaped, spore-producing
structure called a basidium (擔子).
A puffball
ƒ These fungi include
– important forest decomposers and
– particularly destructive plant parasites called rusts (銹
斑菌) and smuts (黑穗菌).
Shelf fungi
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Fungal groups differ in their life cycles and
reproductive structures
ƒ The life cycle of a black bread mold is typical of
zygomycetes.
ƒ Hyphae reproduce asexually by producing spores
in sporangia at the tips of upright hyphae.
© 2012 Pearson Education, Inc.
Fungal groups differ in their life cycles and
reproductive structures
ƒ When food is depleted (耗盡), the fungus reproduces
sexually.
– Mycelia of different mating types join and produce a
zygosporangium, a cell containing multiple nuclei from
two parents.
Zygosporangium (n + n)
Hyphae of
different
mating types
Cells
fuse
2
3
Fusion of
nuclei
1
Young zygosporangium
(heterokaryotic)
– The zygosporangium develops into a thick-walled
structure that can tolerate dry, harsh conditions.
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
– When conditions are favorable, the parental nuclei fuse
to form diploid zygotes, which undergo meiosis
producing haploid spores.
4
Meiosis
Sporangium
(on stalk arising
from the
zygosporangium)
Spores
(n)
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Fungal groups differ in their life cycles and
reproductive structures
Fungal groups differ in their life cycles and
reproductive structures
ƒ The life cycle of a mushroom is typical of
basidiomycetes.
ƒ In the club-shaped cells called basidia, which line
the gills of the mushroom, the haploid nuclei fuse,
forming diploid nuclei.
ƒ The heterokaryotic stage
– begins when mycelia of two different mating types fuse,
– forming a heterokaryotic mycelium,
– which grows and produces the mushroom.
ƒ Each diploid nucleus produces haploid spores by
meiosis.
ƒ A mushroom can release as many as a billion
spores.
ƒ If spores land on moist matter that can serve as
food, they germinate and grown into haploid
mycelia.
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© 2012 Pearson Education, Inc.
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Mushroom
Hyphae of two
different mating types
1
Hyphae of two
different mating types
2
Heterokaryotic
mycelium
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
1
3
Fusion of
nuclei
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
3
Fusion of
nuclei
Diploid nuclei
Diploid nuclei
Meiosis
Mushroom
Mushroom
Basidia
Basidia
Haploid
nuclei
4
Spore
(n)
Hyphae of two
different mating types
2
Heterokaryotic
mycelium
1
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
Meiosis
Basidia
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
ƒ Of the 100,000 known species of fungi, about 30%
are either parasites or pathogens in or on plants.
Haploid
nuclei
4
Spore
(n)
Hyphae of two
different mating types
Heterokaryotic
mycelium
1
Diploid nuclei
Mushroom
2
Heterokaryotic
mycelium
Parasitic fungi harm plants and animals
3
Fusion of
nuclei
Hyphae of two
different mating types
2
1
5
Haploid
mycelia
ƒ About 80% of plant diseases are caused by fungi.
– Between 10 and 50% of the world’s fruit harvest is lost
each year to fungal attack.
– A variety of fungi, including smuts and rusts, infect grain
crops.
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
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Figure 17.18A
Order
Corn smut
Stately (挺拔) English elms (榆樹) in Australia,
unaffected by Dutch elm disease
Parasitic fungi harm plants and animals
Ergots
ƒ Only about 50 species of fungi are parasitic on
animals.
ƒ The general term for a fungal infection is mycosis
(真菌病).
ƒ Skin mycoses include
– ringworm (錢癬), named because it appears as
circular red areas on the skin,
– athlete (運動員)’s foot, also caused by the ringworm
fungus,
– vaginal yeast infections, and
Ergots (麥角菌) on rye (黑麥)
– deadly lung diseases.
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Fungi have enormous ecological benefits
ƒ Fungi
– supply essential nutrients to plants through symbiotic
mycorrhyizae and
– are essential decomposers in ecosystems, breaking
down decomposing leaves, logs, and feces (糞便) and
dead animals.
ƒ Fungi may also be used to digest petroleum (石油)
products to clean up oil spills, such as the 2010 BP
(British Petroleum) spill in the Gulf of Mexico.
A fungal mycelium
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Blue cheese
Fungi have many practical uses
ƒ Fungi have many practical uses for humans.
– We eat mushrooms and cheeses modified by fungi.
– Yeasts produce alcohol and cause bread to rise.
– Some fungi provide antibiotics that are used to treat
bacterial disease.
– Fungi figure prominently (突出) in molecular biology and
in biotechnology. Yeasts, for example, are often used to
study molecular genetics of eukaryotes.
– Fungi may play a major role in the future production of
biofuels from plants.
Blue cheese
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Penicillium
(mold)
Staphylococcus
aureus (bacteria)
Zone of
inhibited
growth
White rot fungus (白腐菌)
Lichens are symbiotic associations of fungi and
photosynthetic organisms
Lichens are symbiotic associations of fungi and
photosynthetic organisms
ƒ Lichens consist of algae or cyanobacteria within a
mass of fungal hyphae.
ƒ Lichens are important pioneers on new land, where
they help to form soil.
– Many lichen associations are mutualistic.
– The fungus receives food from its photosynthetic partner.
ƒ Lichens are sensitive to air pollution, because they
obtain minerals from the air.
– The fungal mycelium helps the alga absorb and retain
water and minerals.
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© 2012 Pearson Education, Inc.
23
Algal cell
Fungal hyphae
You should now be able to
1. Describe the key plant adaptations to life on land.
2. Describe the alternation of generations life cycle.
Explain why it appears that this cycle has evolved
independently in algae and land plants.
3. Describe the key events of the moss, fern, and
pine life cycles.
4. Explain how coal was formed; explain why coal,
oil, and natural gas are called fossil fuels.
Reindeer moss, a lichen
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You should now be able to
You should now be able to
5. Describe the parts of a flower and explain their
functions.
10. Describe the positive ecological and practical
roles of fungi.
6. Describe the stages of the angiosperm life cycle.
11. Describe the structure and characteristics of
lichens.
7. Describe angiosperm adaptations that promote
seed dispersal.
8. Explain how flowers are adapted to attract
pollinators.
9. Compare the life cycles and reproductive
structures in the fungal groups.
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© 2012 Pearson Education, Inc.
24
Ancestral
1
green alga
(a)
(b)
2
(c)
3
(d)
(a) Pine tree, a gymnosperm
(b) Puffball,
a club fungus
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