All green algae and the land plants shared a common ancestor a little over 1 BYAKingdom Viridiplantae Not all photoautotrophs are plants
Red and brown algae excluded
A single species of freshwater green algae gave rise to the entire terrestrial plant lineage
2
Origin of Land PlantsThe green algae split into two major clades
Chlorophytes – Never made it to landCharophytes – Sister to all land plants
Land plants …Have multicellular haploid and diploid stagesTrend toward more diploid embryo protectionTrend toward smaller haploid stage
3
4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ancestral alga
Chlorophytes Charophytes Liverworts HornwortsMosses Lycophytes Gymnosperms Angiosperms
Seed plantsEuphyllophytes
Bryophytes
Land plantsStreptophyta
Green plants
Green algaeGreen algae
Red Algae
Tracheophytes
Ferns + Allies
Adaptations to terrestrial life 1. Protection from desiccation
Waxy cuticle and stomata
2. Moving water using tracheids – specialize cell Tracheophytes have tracheids
Xylem and phloem to conduct water and food
3. Dealing with UV radiation caused mutations Shift to a dominant diploid generation
4. Haplodiplontic life cycle Mulitcellular haploid and diploid life stages Humans are diplontic
5
Haplodiplontic Life CycleMulticellular diploid stage –
sporophyteProduces haploid spores by
meiosisDiploid spore mother cells
(sporocytes) undergo meiosis in sporangia Produce 4 haploid spores First cells of gametophyte
generation
Multicellular haploid stage – gametophyteSpores divide by mitosisProduces gametes by mitosisGametes fuse to form diploid
zygote First cell of next sporophyte
generation 6
7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Spore
Spore
n
n
nn
Spore mother cell
2n
Sporangia
Sporophyte(2n)
2n
2n Zygote
Embryo
Egg
Sperm
MEIOSIS
MITOSIS
FERTILIZATION
n
2n
Gametophyte(n)
All land plants are haplodiplonticRelative sizes of generations varyMoss
Large gametophyteSmall, dependent sporophyte
AngiospermSmall, dependent gametophyteLarge sporophyte
8
BryophytesClosest living descendants of the
first land plantsCalled nontracheophytes because
they lack tracheidsDo have other conducting cells
9
• Mycorrhizal associations important in enhancing water uptake– Symbiotic relationship between fungi and
plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ch
aro
ph
yte
s
Liv
erw
ort
s
Mo
ss
es
Ho
rnw
ort
s
Tra
ch
eo
ph
yte
s
Ex 1: Liverworts (phylum Hepaticophyta)Have flattened
gametophytes with liverlike lobes80% look like mosses
Form gametangia in umbrella-shaped structures
Also undergo asexual reproduction
10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Femalegametophyte
© David Sieren/Visuals Unlimited
Ex2: Mosses (phylum Bryophyta)Gametophytes consist of small, leaflike
structures around a stemlike axisNot true leaves – no vascular tissue
Anchored to substrate by rhizoidsMulticellular gametangia form at the tips of
gametophytesArchegonia – Female gametangiaAntheridia – Male gametangia
Flagellated sperm must swim in water
11
12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Edward S. Ross
Sporophyte
Gametophyte
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
n
2n
2n
2n
1n
1n
Sperm
Sporangium
Antheridia
Egg
Archegonia
Gametophytes
Spores
Rhizoids
Female
Male
Zygote
MITOSIS
FERTILIZATION
Maturesporophyte
Developingsporophyte inarchegonium
Parentgametophyte
MITOSIS
MIE
IOSIS
Germinatingspores
Ex: Mosses (phylum Bryophyta)
Ex 3: Hornworts (phylum Anthocerotophyta)
Origin is puzzling – no fossils until Cretaceous
Sporophyte is photosyntheticSporophyte embedded in gametophyte
tissueCells have a single large chloroplast
13
Photosyntheticsporophyte
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Lee W. Wilcox
Tracheophyte PlantsKnown as vascular plantsCooksonia, the first vascular
land plantAppeared about 420 MYAPhylum Rhyniophyta
Only a few centimeters tallNo roots or leavesHomosporous – only 1 type of
spore
14
SporangiaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Vascular tissuesXylem
Conducts water and dissolved minerals upward from the roots
PhloemConducts sucrose and hormones throughout the
plantEnable enhanced height and size in the
tracheophytesDevelops in sporophyte but not gametophyteCuticle and stomata also found in land plants
15
TracheophytesVascular plants include seven extant
phyla grouped in three clades1. Lycophytes (club mosses) 2. Pterophytes (ferns, whisk ferns, and
horsetails)3. Seed plants
Gametophyte has been reduced in size relative to the sporophyte during the evolution of tracheophytes
Similar reduction in multicellular gametangia has occurred as well
16
StemsEarly fossils reveal stems but no roots or leavesLack of roots limited early tracheophytes
RootsProvide transport and supportLycophytes diverged before true roots appeared
LeavesIncrease surface area for photosynthesisEvolved twice
Euphylls (true leaves) found in ferns and seed plants Lycophylls found in seed plants
18
19
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Euphyll Origins
Lycophyll Origins
Stem withvascular tissue
Stem, leafy tissuewithout vascular tissue
Stem, leafy tissuewith vascular tissue
Singlevascular strand
(vein)
Branchedvascular strands
(veins)Photosynthetic tissue
“webs” branchesBranches in
single planesUnequal
branchingBranching stems
with vascular tissue
400 million years between appearance of vascular tissue and true leavesNatural selection favored plants with higher
stomatal densities in low-CO2 atmosphereHigher stomatal densities favored larger leaves
with a photosynthetic advantage that did not overheat
SeedsHighly resistantContain food supply for young plantLycophytes and pterophytes do not have seeds
20
Fruits in the flowering plants (angiosperms) add a layer of protection to seeds and attract animals that assist in seed dispersal, expanding the potential range of the species
21
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ancestral alga
Chlorophytes Charophytes Liverworts HornwortsMosses Lycophytes Gymnosperms Angiosperms
Chlorophyll a and bPlasmodesmata
CuticleAntheridia and archegoniaMulticellular embryo
Stomata
EuphyllsSeeds
FlowersFruits
Dominant sporophyteStems, roots, leaves
Ferns + Allies
Vascular tissue
LycophytesWorldwide
distribution – abundant in tropics
Lack seedsSuperficially
resemble true mosses
Sporophyte dominant
22
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ho
rnw
ort
s
Lyc
op
hyt
es
See
d P
lan
ts
Fer
ns
and
Alli
es
PterophytesPhylogenetic
relationships among ferns and their relatives is still being sorted out
Common ancestor gave rise to 2 clades
All form antheridia and archegonia
All require free water for flagellated sperm
23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lyc
op
hyt
es
Fer
ns
Ho
rset
ail F
ern
s
Fer
ns
Wh
isk
Fer
ns
See
d P
lan
ts
Whisk fernsFound in tropicsSporophyte consists of evenly
forking green stems without true leaves or roots
Some gametophytes develop elements of vascular tissueOnly one known to do so
24
HorsetailsAll 15 living species are
homosporousConstitute a single species, Equisetum
Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes
Silica deposits in cells – scouring rush
25
FernsMost abundant group of
seedless vascular plantsAbout 11,000 species
Coal formed from forests 300 MYA
Conspicuous sporophyte and much smaller gametophyte are both photosynthetic
26
Fern life cycle differs from that of a moss
Much greater development, independence, and dominance of the fern’s sporophyte
Gametophyte lacks vascular tissue
27
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
MEIOSIS
n
2n
Archegonium
Archegonium
Antheridium
Antheridium
Egg
Sperm
Embryo
1n
Gametophyte
Rhizome
Sporangium
Spores
Rhizoids
Gametophyte
MITOSIS
Undersideof leaf frond
Maturesporangium
Sorus (clusterof sporangia)
Adultsporophyte
Maturefrond
Leaf of youngsporophyte
MITOSIS
Zygote2n
FERTILIZATION
Fern morphologySporophytes have rhizomesFronds (leaves) develop at the tip of the
rhizome as tightly rolled-up coils (“fiddleheads”)
28
Tightly Coiled Fern Uncoiling Fern
(left): © Mike Zens/Corbis; (right): © Ed Reschke
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.