Download Chapter 18 Land environment: plant and fungi

Chapter 18
Land environment: plant and fungi
生醫系 劉秉慧老師 分機11815 2010/03
♣ Alteration of generation
- sporophyte and gametophyte
- the dominant generation
♣ Diversity of plant
- nonvascular plant : moss and its life cycle
- vascular plant
– seedless vascular plants: Ferns
- seed plants - gymnosperm
- angiosperm
♣ Flowering plant life cycle
♣ The Fungi
- general biology
- black bread mold
- mushroom
- mutualistic relationship
- plant and human disease
18.1 Onto Land
• Plants are a diverse group of eukaryotic
organisms.
• Plants, unlike algae, are adapted for living on
land. Plants are related, through evolution, to
green algae
• Plants are classified into four groups.
–
–
–
–
Mosses (苔蘚,地衣)
Ferns (蕨類)
Gymnosperms (裸子植物) (eg. conifers針葉松柏科)
Angiosperms (被子植物) (eg. flowering plants)
conifers
Alternation of Generation
• The plant life cycle differs from the life cycle of
animals.
• There are two forms of a plant
– The spore-bearing sporophyte is diploid (2n).
– The gamete-producing gametophyte is haploid (1n).
• Sporophyte (2 n) produces haploid spores (n) by
meiosis.
• Spores (n) undergo mitosis to produce the plant
gametophyte (n).
• The gametophyte produces gametes (sperm and egg)
through mitosis
• Fertilization of gametes forms a zygote (2 n) that
undergo mitosis and become the sporophyte (2 n)
孢子體
孢子囊
減數分裂
配子
配子體
細胞分裂
細胞分裂
The Dominant Generation
• The dominant generation of a plant is the form that
we recognize as the plant.
– For non-vascular plants, the gametophyte (1n) is
the dominant generation.
– For vascular plants, the sporophyte (2n) is the
dominant generation.
• During the evolution of land plants, the sporophyte
developed vascular tissue and became the larger,
dominant generation of plants.
• In the life cycle of seed plants, the spores, the
gametes, and zygote are protected from drying out in
the land environment.
This trends occurred as plants became adapted for life on land.
18.2 Diversity of Plants
• Non-vascular plants
(those lacking
vascular tissue) were
the first land plants to
evolve.
• Vascular plants
evolved from nonvascular plants.
Nonvascular Plants
• The nonvascular plants include the bryophytes
(liverworts and mosses).
• Bryophytes lack true roots, stems, leaves, and
have a dominant gametophyte generation.
• Gametophyte(1 n)  gametes (sperms and egg,
1n) fertilization : flagellated sperm swim in a
film of water to reach egg  zygotes (2 n) 
embryo (2n) sporophyte (2n) attached to
gmetophyte (1n)  produce spores (1n)
Nonvascular Plants (cont.)
2n
(1n)
(1n)
(1n)
Moss
Vascular Plants
• Vascular plants
generally have true
roots, stems, leaves.
• Vascular plants have
vascular tissue
consisting of the
xylem (木質部) and
phloem (韌皮部).
Vascular Plants (cont.)
Xylem transports water and
minerals up from the roots
Phloem transports organic
nutrients
Seedless Vascular Plants
• Seedless vascular plants include the club
mosses, horsetails, and ferns.
– Club mosses are found in temperate forests.
– Horsetails are taller stems with whorls of slender
green branches.
• During the Carboniferous period, these
plants dominated the swamp forests and
were as tall as trees.
• The compressed remains of these seedless
vascular plants are what formed coal. ( Oil is
most likely formed in marine sedimentary
rocks and included animal remains)
Ferns
• Ferns are a widespread group of seedless
vascular plants.
- sporophyte (dominant form) with vascular
tissue
- gametophyte lacks vascular tissue
• The fern gametophyte is dependent upon
water to achieve fertilization, so ferns are
found in moist environments.
• Some ferns produce rhizomes (根莖) which
allow them to survive in drier areas and grow
horizontally in the soil for producing new
plants.
Maidenhair ferm
Fern life cycle
孢子囊
Water is needed
Seed Plants
• Seed plants are the most
common plants.
• Seeds have three major
parts.
– The embryo
– The stored food supply
– The seed coat
• Seed plants have two
types of spores and two
types of gametophytes.
– Male
– Female
Seed plants:Gymnosperms
• The ovules (胚珠)and seeds of
gymnosperms are exposed on a
modified leaf called the scale.
“Gymnosperm” means “naked
seed”.
♦ Cycads (蘇鐵) and conifers are
gymnosperms.
♦ Conifers are the dominant plants
today that produce cones.
• The needles of conifers have
adaptations that resist water loss,
allowing these plants to grow in
frozen soils where water may be
limiting.
• In seed plants the gametophytes are
microscopic in size.
• Pollen grains are the male, sperm-producing
gametophyte.
• Pollination occurs when the pollen grain
fertilizes the female gametophyte.
• The female gametophyte develops within an
ovule (胚珠), which develops into the seed.
• In gymnosperms, the ovule is not completely
enclosed by sporophyte tissue at pollination.
• In angiosperms, the ovule is completely
enclosed by sporophyte tissue (the ovary子房)
at pollination.
Seed plant: Angiosperms
• The angiosperms
(“covered seeds”) are
the flowering plants. The
ovule is completely
enclosed by sporophyte
tissue (the ovary) at
pollination.
• Angiosperms are also
found in nearly all
climates and can vary
greatly in size from
species to species.
The Flower
• Flowers have several
common structures.
• The sepals (萼片), which
form the calyx(花萼),
protect the flower bud
before it opens.
• The petals(花瓣), which
form the corolla (花冠),
help to attract pollinators.
• The stamen (雄蕊 male
reproductive structure)
consists of the filament
and a pollen-producing
anther (花藥).
The Flower (cont.)
• The carpels (心皮) have three
major regions.
– The ovary (female reproductive
structure) contains the ovules.
– The style elevates the stigma.
– The stigma collects pollen.
• The ovary also produces
nectar in some flowers to
attract pollinators.
Flowering Plant Life Cycle
• The anther produces male microspores, which
undergo mitosis to produce pollens.
• Within the ovule, female megaspores undergo
mitosis to produce the egg.
• During pollination, a pollen grain is transported
to the stigma.
• The pollen tube germinates and extends a
pollen tube to the ovule.
• The pollen tube delivers two sperm to the egg to
carry out double fertilization.
Flowering Plant Life Cycle (cont.)
Flowering Plant Life Cycle (cont.)
• The sperms are involved in two fusion events.
– One sperm fuses with an egg to form a
diploid zygote (2 n).
– One sperm fuses with two other ovule cells
to form the triploid endosperm (胚乳 3 n).
• Endosperm (胚乳)
- the embryo uses the seed endosperm
as nourishment during germination.
- the endosperm is absorbed into the
cotyledon (子葉seed leaves).
Flowering Plant Life Cycle
18.3 The Fungi (真菌)
• Like plants and animals, fungi are generally
multicellular eukaryotes.
• DNA sequence data has indicated that fungi
are more closely related to animals than
plants.
General Biology of a Fungus
• Fungi produce windblown spores during both an
asexual and a sexual life cycle
• Fungi are composed of thin filaments of cells called
hyphae.
• The hyphae are typically organized into a mass
called a mycelium.
• The mycelium penetrates soil, wood, or other media
to acquire nutrients.
mycelium
hyphae
The fungi: Black Bread Mold
• The hyphae (菌絲) of some fungi
- grow horizontally and vertically to anchor the fungi
and acquire nutrients.
- involved in fungal reproduction.
• A sporangium - is a structure that produces spores.
• asexual reproduction
- the fungal spores (1 n) divide mitotically to produce
new hyphae (1 n).
• sexual reproduction
- the conjugation of mycelia to form zygospore
- One is the positive (+) mycelium.
- The other is the negative (-) mycelium
2n
減數分裂
Hyphae 1 n
1n
1n
Spore 1 n
The fungi: Mushroom
• Mushroom forms through sexual production
- a positive and negative hyphae fuse (the nuclei do
not fuse) together
- The dinucleic cells form a stalk and a cap
- A mushroom is the fruiting body of a fungi.
- basidium(孢子臺), within the gills of the cap, are
spore-producing structures
1n
減數分裂
孢子臺
子實體
Hyphae 1n
Mutualistic Relationships
• Two different species contribute positively to each
other’s growth.
• Lichens produce organic matter and create new soil,
allowing plants to invade the area
• Lichens (地衣) are a mutualistic relationship
- fungi and cyanobacteria
- fungi and algae.
• Lichens have three cell layers.
– An upper and lower fungal cell layer
– A middle algal or cyanobacteria layer
( photosynthetic cells)
♦ The fungus provide mineral and water to the
photosynthetic cells
Mutualistic Relationships (cont.)
Fungi and Plant Diseases
• Certain fungi can cause disease in plants and
animals, acting as pathogens.
• Fungal pathogens of plants usually enter through
wounds or the stomata.
• Some fungal diseases impact agricultural production.
– Rice blast disease
– Corn smut (黑穗病)
– Rusts
– Leaf curl
Fungi and Human Diseases
• Mycoses are diseases caused by fungi.
• Mycoses have three levels of infection.
– Cutaneous mycoses only affect the epidermal
layers.
– Subcutaneous mycoses affect deeper skin
layers.
– Systemic mycoses
spread throughout
the body.
Fungi and Human Diseases
• The widest array of fungal
diseases are caused by Candida
albicans.
– Yeast infections in women
– Oral thrush in new born and
AIDS patient
– can cause a systemic
infection that can damage the
heart, brain, and other organ
• Fungi from the genus Tinea
contribute to the ringworm
and athlete’s foot.
- cutaneous infection only