Non-Vascular Plants and Ferns
Evolution of Land Plants• Land plants 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
Chara, a pond organism
(a)10 mm
Coleochaete orbicularis, a disk-shaped charophycean (LM)
(b) 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 EvolutionBryophytes
(nonvascular plants) Seedless vascular plants Seed plants
Vascular plants
Land plants
Origin of seed plants(about 360 mya)
Origin of vascular plants (about 420 mya)
Origin of land plants(about 475 mya)
Ancestralgreen alga
Cha
roph
ycea
ns
Live
rwor
ts
Hor
nwor
ts
Mos
ses
Lyco
phyt
es(c
lub
mos
ses,
sp
ike
mos
ses,
qui
llwor
ts)
Pter
ophy
te (f
erns
, ho
rset
ails
, whi
sk fe
rn)
Gym
nosp
erm
s
Ang
iosp
erm
s
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
BryophytesLIVERWORTS (PHYLUM HEPATOPHYTA)
HORNWORTS (PHYLUM ANTHOCEROPHYTA) MOSSES (PHYLUM BRYOPHYTA)
Gametophore offemale gametophyte
Marchantia polymorpha,a “thalloid” liverwort
Foot
Sporangium
Seta
500
µmMarchantia sporophyte (LM)
Plagiochiladeltoidea,a “leafy”liverwort
An Anthoceroshornwort species
Sporophyte
Gametophyte
Polytrichum commune,hairy-cap moss
Sporophyte
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 relics from a far more eminent past– Are small herbaceous plants
• Ferns– Are the most diverse seedless vascular plants
Seedless Vascular PlantsLYCOPHYTES (PHYLUM LYCOPHYTA)
PTEROPHYTES (PHYLUM PTEROPHYTA)
WHISK FERNS AND RELATIVES HORSETAILS FERNS
Isoetesgunnii,a quillwort
Selaginella apoda,a spike moss
Diphasiastrum tristachyum, a club moss
Strobili(clusters ofsporophylls)
Psilotumnudum,a whiskfern
Equisetumarvense,fieldhorsetail
Vegetative stem
Strobilus onfertile stem
Athyrium filix-femina, lady fern
Ferns• Seedlsess
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
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– Haploid cells divide into a cluster of
cells before meiosis
Alternation of Generations
HAPLOIDMeiosis
Sporesn
Mitosis
Gametophytes(male and female)
nMitosis
Gametes(sperm and eggs)
n
Fertilization
Zygote2n
Mitosis
DIPLOID
Sporophyte2n
Dominant Gametophyte• Mosses have a dominant gametophyte
stageSperm (n) (released fromtheir gametangium)
1
2
3
4
Gametangiumcontaining the egg (n) (remains within gametophyte)
Egg
Fertilization
Zygote(2n)
Mitosis anddevelopment
Sporophytes (growing from gametophytes)
HAPLOIDDIPLOID
Gametophyte(n)
SporangiumStalk
Meiosis
Spores(n)
5 Mitosis anddevelopment
Gametophytes(n)
Dominant Sporophyte• Most plants have a dominant
sporophyte stage
1
2
3
4
Gametophyte (n) (underside)
Sperm (n)
Egg (n) Fertilization
Zygote(2n)
Mitosis anddevelopment
New sporophyte growingout of gametophyteSporophyte (2n)
MeiosisSporangia
5
Spores(n)
Mitosis anddevelopment
HAPLOIDDIPLOID
Seeded Vascular Plants• Gymnosperms-
conifers, cycads, and ginkgo
• Angiosperms- flowering plants