Download CHARACTERISTICS OF PLANTS

CHARACTERISTICS OF PLANTS:
Eukaryotic Cells
Autotrophic and Multicellular
Cell Walls Contain Cellulose
Alternation of Generation
Embryonic Development
• More than 280,000 species of
plants inhabit Earth today.
Land plants (including the sea
grasses) evolved from a certain
green algae, called charophytes
Spirogyra, a
model
chlorophyte
CHALLENGES FACED BY PLANTS
FOR LIFE ON LAND
•Obtaining enough water
•Transporting water and dissolved
substances to other parts of the
plant body and transporting the
products of photosynthesis to
other parts of the plant that don't
conduct photosynthesis
•Preventing excessive loss of water
by evaporation
•Maintaining an extensive moist
surface for gas exchange
•Supporting a large plant body against
gravity
•Carrying out reproduction when there
is little water
•Lastly, withstanding the extreme
fluctuations in temperature,
humidity, wind, and light which
are moderated in water due to
its high heat capacity
Land Plants Evolved from Green
Algae.
Common Characteristics:
•Rose-shaped complexes for cellu
lose synthesis
•Peroxisome enzymes
•Structure of flagellated sperm
•Formation of a phragmoplast
Charophyceans:
Chara (top),
Coleochaete
orbicularis
(bottom)
Several Features of Land Plants
Differ From Those of Green Algae
Multicellular sex organs with
an outer layer of jacket cells
Cuticles on leaves
Derived Traits of Land Plants
(These traits are absent in the
charophyceans – next four
slides)
Apical Meristems of Plant Shoots and
Roots
Alternation of Generations: a Generalized Scheme
Multicelllular Gametangia:
Archegonium of Marchantia (left),
Antheridium of a hornwort (right)
Multicellular Dependent Embryos:
Marchantia (left), Shepherd's purse (right)
Walled Spores Produced In Sporangia
Cooksonia, a Vascular Plant of the
Silurian Period
Leaves of Vascular Plants
• There are four main groups
of land plants:
• Bryophytes
• Pteridophytes
• Gymnosperms
• Angiosperms – 90% of all
plants
Representatives of the
Four Major Groups of Plants
• There are four great episodes in
the evolution of land plants:
–the origin of bryophytes from
algal ancestors
–the origin and diversification of
vascular plants
–the origin of seeds
–the evolution of flowers
p. 578
Some Highlights of Plant Evolution
140
mya
360 mya
420 mya
475 mya
Reduction in the Size of the Gametophyte
Bryophytes
Liverwort
Hornwort
Liverwort
Moss
Moss with Sporophytes
Gametophytes
Liverwort, Marchantia
Antheridia
Archegonia
Hornwort – a Characteristic Bryophyte
Moss (Polytrichum) Life Cycle
The life cycle of Polytrichum, a moss
Pteridophytes
Club
Moss
Whisk Fern
Horsetail
Fern
Whisk Fern, Psilotum
Club
Moss
Club Moss in Olympic National
Forest – WA State
Club Moss in Olympic National
Forest
Club mosses (Lycopodium)
have microphylls, with single
veins
Horsetail
Horsetails and
the other
seedless
vascular plants
have highly
branched
vascular
systems called
megaphylls.
Fern sporophyll, a leaf specialized for spore
production
Fern Sori
(clusters of
sporangia)
• Sporophylls
–modified leaves with sporangia
• Most seedless vascular plants
–Are homosporous, producing one
type of spore that develops into a
bisexual gametophyte
sporangium > single > bisexual > eggs and sperm
type of gametophyte
spore
• All seed plants and some
seedless vascular plants
–Are heterosporous, having two
types of spores that give rise to
male and female gametophytes
megaspore > female gametophyte > eggs
microspore > male gametophyte > sperm
Fern Life Cycle
The Life Cycle of a Fern
• The first seed plants evolved
about 360 million years ago,
near the end of the Devonian
Period.
• A seed consists of a plant
embryo packaged along with
a food supply within a
protective coat.
The Reduced Gametophyte of Seed Plants
are Protected in Ovules and Pollen Grains
From Ovule to Seed
Phylum Ginkgophyta
The Gingko
(biloba) tree
is a “living fossil”
and has been on
the earth virtually
unchanged for
at least 150
million years. It
produces “naked”
seeds, as do all
other
gymnospernms.
Seeds
Female Gingko
The Ginkgo Tree
Male
Female
Sago Palm
or
Cycad,
a
gymnosperm
Sago Palm or Cycad Cones
Figure 24.19
Phylum Gnetophyta: Welwitschia
Phylum Gnetophyta:
Ephedra
Ephedra
Figure 24.21
Phylum
Coniferophyta:
Douglas
Fir
These are
male cones
on a pine
tree.
Female Pine Cone
Male Pine
Cones
This picture was
taken in Sequoia
National Park in
Central California.
One sequoia tree,
nicknamed the
“General
Sherman Tree” is
the
heaviest/largest
tree in the world. It
is over 2300 years
old and weighs
over 1300 tons.
This picture is of
“The Lone
Cypress”
taken on the 17
mile drive on the
Monterey
Peninsula.
It is one of the
most commonly
photographed
trees in the
world.
This picture is of
the Bristlecone
Pine Tree which is
the oldest tree in
the world – over
4700 years old.
“Methusaleh” as
the oldest tree is
called is located in
the White
Mountains of
California.
Pine Life Cycle
The Life Cycle of a Pine
• The great majority (90%) of
modern-day plant species are
flowering plants, or
angiosperms.
–Flowers evolved in the early
Cretaceous period, about 140
million years ago.
–A flower is a complex
reproductive structure that bears
seeds within protective
chambers called ovaries.
Representatives of Major Angiosperm
Clades
Figure 30.18 Flower-pollinator relationships: Scottish broom flower and honeybee
(left), hummingbird (top right), baobab tree and bat (bottom right)
Generalized Flower Structure
Angiosperm Life Cycle
The Life Cycle of an Angiosperm