All green algae and the land plants shared a common ancestor a little over 1 BYA Kingdom Viridiplantae Not all photoautotrophs are plants Red and brown

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


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


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


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


© Edward S. Ross

Sporophyte

Gametophyte


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


© 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

17

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


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


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


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


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


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


Fern reproductionProduce distinctive sporangia in clusters

called sori on the back of the frondsDiploid spore mother cells in sporangia

produce haploid spores by meiosisSpores germinate into gametophyte

Rhizoids but not true roots – no vascular tissueFlagellated sperm

29

Documents

All green algae and the land plants shared a common ancestor a little over 1 BYA Kingdom Viridiplantae Not all photoautotrophs are plants Red and brown