Transcript Aquatic Plants

Aquatic Plants:
Non-Vascular Plants and
Ferns
Evolution of Plants
• Plants are thought to
have evolved from
green algae
• The green algae called
charophyceans are the
closest relatives of land
plants
• Comparisons of both
nuclear and chloroplast
genes
– Point to charophyceans as
the closest living
relatives of land plants
(a) Chara,
a pond
organism
10 mm
(b) Coleochaete orbicularis, a diskshaped charophycean (LM)
40 µm
Origin and Diversification of
Plants
• Fossil evidence
indicates that plants
were on land at least
475 million years ago
• Whatever the age of
the first land plants
those ancestral
species gave rise to a
vast diversity of
modern plants
Plant Evolution
Land plants
Vascular plants
Origin of vascular
plants (about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga
Origin of seed plants
(about 360 mya)
Angiosperms
Seed plants
Gymnosperms
Pterophyte (ferns,
horsetails, whisk fern)
Lycophytes(club mosses,
spike mosses, quillworts)
Seedless vascular plants
Mosses
Hornworts
Liverworts
Charophyceans
Bryophytes
(nonvascular plants)
Alternation of Generations
• The seed plant life cycle contains both
haploid and diploid stages
– Diploid individuals are called sporophytes
– Haploid individuals are called
gametophytes
• Does not happen in algae
• May have evolved as an adaptation to
harsh environments
Alternation of Generations
Gametophytes
(male and female)
n
Spores
n
Meiosis
Gametes
(sperm and eggs)
n
HAPLOID
Fertilization
DIPLOID
Zygote
2n
Sporophyte
2n
Dominant Gametophyte
• Mosses have a dominant gametophyte stage
5 Mitosis and
Sperm (n) (released from
their gametangium)
development
Spores
(n)
1
Gametangium
containing the egg (n)
(remains within
gametophyte)
Gametophytes
(n)
Egg
HAPLOID
DIPLOID
Meiosis
Sporangium
Fertilization
Stalk
2
4
Zygote
(2n)
Gametophyte
(n)
3 Mitosis and
development
Sporophytes (growing from gametophytes)
Dominant Sporophyte
• Most plants have a dominant sporophyte
stage
5
Sperm (n)
Mitosis and
development
Spores
(n)
1
Gametophyte (n)
(underside)
Egg (n)
Meiosis
Sporangia
HAPLOID
DIPLOID
Fertilization
2
4
Zygote
(2n)
3 Mitosis and
development
Sporophyte (2n)
New sporophyte growing
out of gametophyte
Non Vascular Plants:
Bryophytes
• Life cycles of mosses and other
bryophytes are dominated by the
gametophyte stage
• Bryophytes are represented today by
three phyla of small herbaceous
(nonwoody) plants
– Liverworts, phylum Hepatophyta
– Hornworts, phylum Anthocerophyta
– Mosses, phylum Bryophyta
Bryophytes
Gametophore of
female gametophyte
LIVERWORTS (PHYLUM HEPATOPHYTA)
Plagiochila
deltoidea,
a “leafy”
liverwort
Foot
Seta
Marchantia sporophyte (LM)
HORNWORTS (PHYLUM ANTHOCEROPHYTA)
An Anthoceros
hornwort species
Sporophyte
Sporangium
500 µm
Marchantia polymorpha,
a “thalloid” liverwort
MOSSES (PHYLUM BRYOPHYTA)
Polytrichum commune,
hairy-cap moss
Sporophyte
Gametophyte
Gametophyte
Liverworts
• Have no true roots or
shoots
• Non- vascular
• Require water to
reproduce
• Have no or very little
leaf structure
• Cannot live in
sporophyte form
Hornworts
• Free-floating aquatic
plant, or land plant
• No vascular tissue
• No true leaves or
roots
• Can live in both
gametophyte and
sporophyte forms
Mosses
• Land plant
• Most have no vascular
tissue
• Majority to life spent in
gametophyte
• Need water to breed
• No leaves or roots
• Sporophytes are
capsules on stalks
Vascular Plants
• Vascular plants have two types of
vascular tissue
– Xylem and phloem
• Xylem
– Conducts most of the water and minerals
– Includes dead cells called tracheids
• Phloem
– Distributes sugars, amino acids, and other
organic products
– Consists of living cells
Vascular Plants
• Vascular plants have roots
– Are organs that anchor vascular plants
– Enable vascular plants to absorb water and
nutrients from the soil
– May have evolved from subterranean stems
• Vascular plants have leaves
– Leaves are organs that increase the surface
area of vascular plants, thereby capturing
more solar energy for photosynthesis
Vascular Plants
• Two types of vascular plants: seedless and
seeded
• Seedless vascular plants form two phyla
– Lycophyta, including club mosses, spike mosses,
and quillworts
– Pterophyta, including ferns, horsetails, and whisk
ferns and their relatives
• Modern species of lycophytes are really ancient
– Are small herbaceous plants
• Ferns
– Are the most diverse seedless vascular plants
Seedless Vascular Plants
LYCOPHYTES (PHYLUM LYCOPHYTA)
Strobili
(clusters of
sporophylls)
Isoetes
gunnii,
a quillwort
Selaginella apoda,
a spike moss
Diphasiastrum tristachyum, a club moss
PTEROPHYTES (PHYLUM PTEROPHYTA)
Psilotum
nudum,
a whisk
fern
Equisetum
arvense,
field
horsetail
Athyrium
filix-femina,
lady fern
Vegetative stem
Strobilus on
fertile stem
WHISK FERNS AND RELATIVES
HORSETAILS
FERNS
Ferns
• Vascular plants but
do not have seeds
– Common in shady
areas, diverse in the
tropics
– Have flagellated
sperm that require
water to reach the
eggs
Land plants:
Seeded Vascular Plants
• Gymnospermsconifers, cycads,
and ginkgo
• Angiospermsflowering plants