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

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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

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Ang

iosp

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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