Transcript You Light Up My Life

Plants
Chapter 22
Setting the Stage for
Plants
• Earth’s atmosphere was originally
oxygen free
• Ultraviolet radiation bombarded the
surface
• Photosynthetic cells produced
oxygen and allowed formation of a
protective ozone layer
Invading the Land
• Cyanobacteria were probably the
first to spread into and up
freshwater streams
• Later, green algae and fungi made
the journey together
• Every plant is descended from
species of green algae
The Plant Kingdom
• Nearly all are multicelled
• Vast majority are
photoautotrophs
– Energy from sun
– Carbon dioxide from air
– Minerals dissolved in water
22.1 Evolutionary Trends
• 295,00 species of plants
• Most plants are vascular-internal
tissue conducts water and solutes
through roots, stems, and leaves
• 19,000 species are nonvascularcalled bryophytes-liverworts,
hornworts mosses
22.1 Evolutionary Trends
• Seedless vascular plants-wisk ferns,
lycophytes, horsetails and ferns
• Gymnosperms- cycads, ginkgos,
gnetophytes and conifers (seedbearing vascular plants)
• Angiosperms-Dicots and monocotstwo classes of flowering plants
22.1 Evolutionary Trends
• Simple roots began to form when
plants colonized the land. Later
became more specialized roots.
• Most root systems have many
underground absorptive structures
with increased surface area.
22.1 Evolutionary Trends
• Above grounds shoots evolvedstems, leaves that absorb energy
from the sun and carbon dioxide
from the air.
• Plants changed as they began to
move into higher and drier places.
22.1 Evolutionary Trends
• Diploid zygote forms at fertilization,
mitotic cells divide and cell
enlargements convert it into a
sporophyte.
• After some of its cells undergo
meiosis, haploid resting cells
(spores) form.
22.1 Evolutionary Trends
• Seed-bearing plants produce two types of
spores. This condition is known as
heterospory.
• One type of spore is known as homospory.
• In gymnospers and angiosperms,
macrospores tive rise to female
gametophytes in which eggs form and get
fertilized.
22.1 Evolutionary Trends
• Smaller microspores are the start of pollen grainscellular structures that become mature, spermbearing male gametophytes.
• Pollen grains travel with the help of wind, birds,
insects, and other animals.
• In drier habitats, seed production also adapted.
Female gametophytes of seed-bearing plants form
within sporophyte tissue.
22.1 Evolutionary Trends
• In most lineages, structural adaption ot
life on land included a root system, shoot
system, waxy cuticle, stomata, vascular
tissues and lignin-reinforced tissue.
• Lignin- found in cell walls; an organic
compound that helps give plant cell its
structure.
Milestones in Plant Evolution
Pg. 343.
?
FLOWERING PLANTS
CONIFERS
CYCADS
PROGYMNOSPERMS
GINKGOS
FERNS
HORSETAILS
ancestral
green
algae
LYCOPHYTES
RHYNIOPHYTES
BRYOPHYTES
PALEOZOIC
Silurian
Ordovician
Devonian
505
435
410
360
MESOZOIC
Permian
Carboniferous
290
Cretaceous
Triassic
Jurassic
240
205
138
65
Time (millions of years ago)
CENOZOIC
Present
22.3 BryophytesNonvascular Plants
• Bryophytes
• Fewer than 19,000
species
• Three groups
Liverworts
Hornworts
Mosses
Nonvascular Plants
• Adapted to grow well in
fully or seasonally moist
habitats. (Mosses are
sensitive to pollution, but
will grow in almost all
other environmentsincluding deserts and
Antarctica.)
Nonvascular Plants
Bryophytes
Mosses
radially symmetrical
rhizoids multicellular
leaves usually with midrib
Thallose liverwort bilaterally
symmetrical
rhizoids unicellular
Bryophytes
• Small, nonvascular,
nonwooody
• Gametophyte dominates life
cycle; has leaflike, stemlike,
and rootlike parts
• Usually live in wet habitats
• Flagellated sperm require
water to reach eggs
Types of Bryophytes
Liverworts (simplest)
Hornworts
Mosses (most common)
Marchantia: A Liverwort
• Reproduces asexually by way of
gemmae cups
• Sexual reproduction
•Gametophytes are male or female
•Gametes are produced on elevated
structures
Moss Life Cycle
Development of
mature
sporophyte (still
attached to
gametophyte)
Zygote
Fertilization
Diploid Stage
Meiosis
Haploid Stage
Spores
released
male
gametophyte
tip
Sperm
Egg
Male gametophyte
female
gametophyte
tip
Female gametophyte
Peat Mosses
• 350 species
• Sphagnum is an example
• Grow in acidic bogs; important
ecosystems of cold and temperate
regions
• Peat can be harvested and burned as
fuel
Seedless Vascular Plants
• Like bryophytes
– Live in wet, humid places
– Require water for
fertilization
• Unlike bryophytes
– Sporophyte is free-living
and has vascular tissues
Types of
Seedless Vascular Plants
Whisk ferns
(Psilophyta)
Lycophytes (Lycophyta)
Horsetails
(Sphenophyta)
Ferns (Pterophyta)
Corksonia
Ferns (Pterophyta)
• 12,000 species, mostly tropical
• Most common sporophyte structure
– Perennial underground stem (rhizome)
– Roots and fronds arise from rhizome
– Young fronds are coiled “fiddleheads”
– Mature fronds divided into leaflets
– Spores form on lower surface of some
fronds
Fern Life Cycle
The sporophyte
(still attached to
the gametophyte)
grows, develops.
Sori
rhizome
zygote
Diploid Stage
Haploid Stage
fertilization
meiosis
Spores develop.
egg
sperm
eggproducing
structure
Spores are
released
mature
gametophyte
(underside)
spermproducing
structure
gametophyte
Spore
germinates
Nonvascular Plants
Bryophytes
Thallose liverwort bilaterally
symmetrical
rhizoids unicellular
Liverwort
Nonvascular Plants
Bryophytes are nonvascular plants with
flagellated sperm that require liquid water to
reach and fertilize the eggs.
A sporophyte of these plants develops within
gametophyte tissues. It remains attached to the
gametophyte and receives some nutritional
support from it.
22.4
Vascular Plants
• Majority of plants
• Have internal tissues that carry
water and solutes
• Two groups
– Seedless vascular plants
– Seed-bearing vascular plants
Seedless Vascular Plants
• Arose during the Devonian period
• Produce spores but no seeds
• Four main groups
Whisk ferns
Lycophytes
Horsetails
Ferns
Seedless Vascular Plants
• Most seedless vascular plants live in
wet, humid places. Their
gametophytes lace vascular tissues.
Water clinging to these plants are
the only means for flagellated sperm
to reach the eggs.
Geologic Time Table
http://www.plantapalm.com/
vce/evolution/timetable.htm
Evolutionary Trend
zygote
GREEN ALGA
BRYOPHYTE
FERN
GYMNOSPERM
ANGIOSPERM
Seedless Vascular Plants
• Psilotum grows
wild in Florida
woodlands and all
members of the
division,
Psilophyta, today
are tropical plants
Seedless Vascular Plants
• Psilotum grows
wild in Florida
woodlands and all
members of the
division,
Psilophyta, today
are tropical plants
Seedless Vascular Plants
• Running pine or
Lycopodium
complanatum, an
Ohio native
Seedless Vascular Plants
Equisetum
palustre
Horsetails
Strobili
Seedless Vascular Plants
22.5 Seed-Bearing
Vascular Plants
• Gymnosperms arose
first
– Cycads
– Ginkgos
– Gnetophytes
– Conifers
• Angiosperms arose later
– Monocots
– Dicots
Gymnosperms
• Plants with “naked seeds”
• Seeds don’t form inside an
ovary
• Four groups
Conifers
Ginkgos
Cycads
Gnetophytes
Conifer Characteristics
• Widest known, largest
number of living
species
• Woody trees or shrubs
• Most are evergreen
• Bear seeds on exposed
cone scales
• Most produce woody
cones
Cycads
• Most diverse during age of dinosaurs
• Only 100 living species
• Two species of Zamia are native to
U.S.
• Palmlike appearance
• Pollen-bearing and seed-bearing
cones on different plants
Ginkgos
• Diverse during age of dinosaurs
• Only surviving species, Ginkgo
biloba, is native to China
• Deciduous tree with fan-shaped
leaves
• Trees are male or female
• Female trees produce seeds covered
with a fleshy, foul-smelling coat
3 Genera of Gnetophytes
• Gnetum - Tropical climbing
vines
• Ephedra (joint fir, Mormon
tea)
Pine Cones
• Woody scales of a “pine cone”
are the parts of where
megaspores formed and
developed into female
gametophytes
• Male cones, where microspores
and pollen are produced, are not
woody
Pine
Life
Cycle
Female cone
Sporophyte
ovule
Male cone
Pollen sac
Seed
fertilization
egg
Pollen tube
View inside
ovule
meiosis
microspores
megaspores
Conifer Distribution
• Conifers dominated during Mesozoic
• Reproduce more slowly than
angiosperms; at competitive
disadvantage in many habitats
• Still dominate in far North, at higher
elevations, and in certain parts of
Southern Hemisphere
Rise of Seed-Bearing
Plants
• Seeds appeared about 360
million years ago
• Seed ferns and gymnosperms
were dominant at first
• Angiosperms arose later
Special Traits of
Seed-Bearing Plants
• Pollen grains
– Arise from megaspores
– Develop into male gametophytes
– Can be transported without water
• Seeds
– Embryo sporophyte inside nutritive
tissues and a protective coat
– Can withstand hostile conditions
Vascular Plants
Adaptations to Land
• Root systems
• Shoot systems
• Vascular tissues
• Waxy cuticle for
water conservation
Seed-Bearing Vascular
Plants
Conifers
Bristle-coned pines
The oldest trees
Giant redwoodsthe tallest trees
http://www.mcwdn.org/Plants/Angiosperm.html
Angiosperms
• Flowering plants
• Dominant land plants (260,000
species)
• Defining feature: Ovules and (after
fertilization) seeds are enclosed in
an ovary
• Two classes: Monocots and dicots
Structure of Flower and
Seed
endosperm
embryo
ovule
seed coat
ovary
Flowering
Plant Life
Cycle
Diploid
Double fertilization
Haploid
pollination
Two
sperm
enter
ovule
Meiosis
microspores
Female gametophyte
Meiosis
Mitosis
without
cytoplasmic
division
Seed-Bearing Plants
• Microspores that give
rise to pollen grains
• Megaspores inside
ovules
• More water-conserving
than seedless vascular
plants
Pollen
• Pollen grains are sperm-bearing male
gametophytes that develop from
microspores
• Allows transfer of sperm to egg
without water
• Can drift on air currents, or be
carried by pollinators
Ovules
• Female reproductive structures that
become seeds
• Consist of:
– Female gametophyte with egg cell
– Nutrient-rich tissue
– Jacket of cell layers that will form seed
coat
Double Fertilization
• Distinctive feature of angiosperms
• Male gametocyte delivers two
sperm to an ovule
• One fertilizes egg; other fertilizes a
cell that gives rise to endosperm
that supports embryo
People and Plants
• Plant domestication began about
11,000 years ago
• About 3,000 species have been
used as food
• Now about 200 plants are major
crops
Nonfood Uses of Plants
• Lumber, paper, and fuel from
conifers
• Furniture from hardwoods
• Rope from agave, hemp
• Thatched roofing from grasses,
palms
• Natural insecticides
• Drugs from foxglove, periwinkle
Plants of Abuse
• Tobacco plants are Nicotiana sp.
• Cannabis sativa is source of
marijuana
• Coca leaves are used to produce
cocaine
• Toxic plant alkaloids, such as
henbane and belladona, have been
used as poisons and as medicine
Review
• Chart pg. 354
• Summary and Review Questions, Self
Quiz and end of chapter readings.