Create a timeline with the following events:

a. Earth is born

b. First life

c. Multicellularity

d. Colonization of land

e. First vascular plants

f. First insects

g. Dinosaurs

h. Flowering plants

Create a timeline with the following events:

a. Earth is born 4.6 bya

b. First life 3.8 bya

c. Multicellularity 1 byad. Colonization of land 500 mya (or 1.2 bya)

e. First vascular plants 425 mya

f. First insects 400 mya

g. Dinosaurs 300 mya

h. Flowering plants 130 mya

LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures byErin Barley

Kathleen Fitzpatrick

Plant Diversity I: How Plants Colonized Land

Chapter 29

Guiding questions:• Why did land plants come to be?• What challenges did it pose?• Name the 4 primary clades of all plants.

– Derived traits of them collectively• Especially alternation of generations

– Ancestral traits of them collectively

• What are the derived characters unique to seedless plants?– Non-vascular (mosses)– Vascular (ferns)

Concept 29.1: Land plants evolved from green algae

• Green algae called charophytes are the closest relatives of land plants– Note that land plants are not descended from modern charophytes, but share a

common ancestor with modern charophytes

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Adaptations Enabling the Move to Land

• In charophytes a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out– Sporopollenin is also found in plant spore walls

• Why move to land?• What challenges did the move pose?

© 2011 Pearson Education, Inc.

1 m

Figure 29.4

Red algae

Chlorophytes

Charophytes

Embryophytes

ANCESTRALALGA

Virid

iplan

taeStrep

top

hyta

Plan

tae

Derived Traits of Plants

• Four key traits appear in nearly all land plants but are absent in the charophytes

1. Alternation of generations

2. Walled spores produced in sporangia

3. Multicellular gametangia

4. Apical meristems

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1. Alternation of Generations and Multicellular, Dependent Embryos

• Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations

• The gametophyte is haploid and produces haploid gametes by mitosis

• Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis

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• The diploid embryo is retained within the tissue of the female gametophyte

• Nutrients are transferred from parent to embryo through placental transfer cells

• Land plants are called embryophytes because of the dependency of the embryo on the parent

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1 m

Figure 29.5a

Gamete fromanother plant

Key

Haploid (n)

Diploid (2n)Gametophyte(n)

Mitosis Mitosis

Spore Gamete

MEIOSIS FERTILIZATION

Zygote

MitosisSporophyte(2n)

Alternation of generations

2n

n

n n

n

2. Walled Spores Produced in Sporangia• The sporophyte produces spores in organs called

sporangia• Diploid cells called sporocytes undergo meiosis

to generate haploid spores• Spore walls contain sporopollenin, which makes

them resistant to harsh environments

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1 m

Figure 29.5c

SporesSporangium

Longitudinal section ofSphagnum sporangium (LM)

Sporophyte

Gametophyte

Sporophytes and sporangia of Sphagnum (a moss)

3. Multicellular Gametangia• Gametes are produced within organs called

gametangia• Female gametangia, called archegonia, produce

eggs and are the site of fertilization• Male gametangia, called antheridia, produce and

release sperm

© 2011 Pearson Education, Inc.

1 m

Figure 29.5d

Femalegametophyte

Malegametophyte

Archegonia,each with anegg (yellow)

Antheridia(brown),containing sperm

Archegonia and antheridia of Marchantia (a liverwort)

4. Apical Meristems• Plants sustain continual growth in their apical

meristems• Cells from the apical meristems differentiate into

various tissues

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1 m

Figure 29.5e

Apical meristemof shoot

Developingleaves

Shoot100 m100 mRoot

Apicalmeristemof root

Apical meristems of plantroots and shoots

• Additional derived traits include– Cuticle, a waxy covering of the epidermis– Mycorrhizae, symbiotic associations between

fungi and land plants that may have helped plants without true roots to obtain nutrients

– Secondary compounds that deter herbivores and parasites– Very useful to humans, too

© 2011 Pearson Education, Inc.

1 m

Figure 29.7

Origin of land plants (about 475 mya)

Origin of vascular plants (about 425 mya)

Origin of extant seed plants (about 305 mya)

2

1

3

2

1ANCESTRALGREENALGA

500 450 400 350 300 50 0

Millions of years ago (mya)

Liverworts

Mosses

Hornworts

Lycophytes (clubmosses, spikemosses, quillworts)

Pterophytes (ferns,horsetails, whisk ferns)

Gymnosperms

Angiosperms

La

nd

pla

nts

Va

sc

ula

r pla

nts

No

nv

as

cu

lar

pla

nts

(bry

op

hy

tes

)

Se

ed

les

sv

as

cu

lar

pla

nts

Se

ed

pla

nts

3

Know plant types, and key distinguishing elements

• Seedless plants can be divided into clades

– Bryophytes (non-vascular, e.g. mosses and their relatives)

– Lycophytes and Pterophytes (vascular, e.g. club mossess, ferns and their relatives)– Seedless vascular plants are paraphyletic, and are

of the same level of biological organization, or grade

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• A seed is an embryo and nutrients surrounded by a protective coat

• Seed plants form a clade and can be divided into further clades

– Gymnosperms, the “naked seed” plants, including the conifers

– Angiosperms, the flowering plants

1 m

Table 29. 1

Concept 29.2: Mosses and other nonvascular plants have life cycles dominated by gametophytes

• Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants

– Liverworts, phylum Hepatophyta– Hornworts, phylum Anthocerophyta– Mosses, phylum Bryophyta

• Bryophyte refers to all nonvascular plants, whereas Bryophyta refers only to the phylum of mosses

© 2011 Pearson Education, Inc.

1 m

Figure 29.UN01

Nonvascular plants (bryophytes)

Seedless vascular plantsGymnosperms

Angiosperms

Bryophyte Gametophytes

• In all three bryophyte phyla, gametophytes are larger and longer-living than sporophytes

• Sporophytes are typically present only part of the time

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Protonemata(n)

Key

Haploid (n)Diploid (2n)

“Bud”

“Bud”

Malegametophyte(n)

GametophoreSporesSporedispersal

Peristome

Femalegametophyte(n) Rhizoid

Sporangium Seta

Capsule(sporangium)

Foot

MEIOSIS

Mature sporophytes

2 m

m

Capsule withperistome (LM) Female

gametophytes

1 m

Figure 29.8-1

Protonemata(n)

Key

Haploid (n)Diploid (2n)

“Bud”

“Bud”

Malegametophyte(n)

AntheridiaSperm

Egg

ArchegoniaGametophoreSpores

Sporedispersal

Peristome

Femalegametophyte(n) Rhizoid

FERTILIZATION(within archegonium)

Sporangium Seta

Capsule(sporangium)

Foot

MEIOSIS

Mature sporophytes

2 m

m

Capsule withperistome (LM) Female

gametophytes

1 m

Figure 29.8-2

Protonemata(n)

Key

Haploid (n)Diploid (2n)

“Bud”

“Bud”

Malegametophyte(n)

AntheridiaSperm

Egg

ArchegoniaGametophoreSpores

Sporedispersal

Peristome

Sporangium

Femalegametophyte(n) Rhizoid

FERTILIZATION(within archegonium)Zygote

(2n)

Archegonium

Embryo

Seta

Capsule(sporangium)

Foot

Youngsporophyte(2n)

MEIOSIS

Mature sporophytes

2 m

m

Capsule withperistome (LM) Female

gametophytes

1 m

Figure 29.8-3

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Animation: Moss Life Cycle Right-click slide / select “Play”

Bryophyte Sporophytes

• Bryophyte sporophytes grow out of archegonia, and are the smallest and simplest sporophytes of all extant plant groups

• A sporophyte consists of a foot, a seta (stalk), and a sporangium, also called a capsule, which discharges spores through a peristome

• Hornwort and moss sporophytes have stomata for gas exchange; liverworts do not

© 2011 Pearson Education, Inc.

1 m

Figure 29.9a

Sporophyte

ThallusGametophore offemale gametophyte

Marchantia polymorpha,a “thalloid” liverwort

Marchantia sporophyte (LM)

FootSeta

Capsule(sporangium)

500

mPlagiochila deltoidea, a “leafy” liverwort

1 m

Figure 29.9b

An Anthoceroshornwort species

Sporophyte

Gametophyte

1 m

Figure 29.9c

Polytrichum commune,hairy-cap moss

Capsule

Seta

Sporophyte(a sturdyplant thattakes monthsto grow)

Gametophyte

1 m

Can bryophytes reduce the rate at which key nutrients are lost from soils?

With moss Without moss

RESULTS

An

nu

al n

itro

gen

lo

ss(k

g/h

a)6

5

4

3

2

1

0

1 m

Figure 29.11

Peat being harvested from apeatland

(a) “Tollund Man,” a bog mummydating from 405–100 B.C.E.

(b)

Concept 29.3: Ferns and other seedless vascular plants were the first plants to grow tall

• Why bother striving for being tall?• What new feature allowed for height?

© 2011 Pearson Education, Inc.

1 m

Figure 29.UN03

Nonvascular plants (bryophytes)

Seedless vascular plants

Gymnosperms

Angiosperms

Derived Traits of Vascular Plants

• Living vascular plants are characterized by 1. Life cycles with dominant sporophytes

2. Vascular tissues called xylem and phloem

3. Well-developed roots and leaves

© 2011 Pearson Education, Inc.

1 m

Figure 29.12

Sporangia

Life Cycles with Dominant Sporophytes

• In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in familiar ferns

• The gametophytes are tiny plants that grow on or below the soil surface

• Seedless vascular plants have flagellated sperm and are usually restricted to moist environments

© 2011 Pearson Education, Inc.

1 m

Figure 29.13-3

Key

Haploid (n)Diploid (2n)

MEIOSISSporedispersal

Spore(n)

Younggametophyte

Rhizoid

Undersideof maturegametophyte(n)

Antheridium

Sperm

Archegonium

Egg

FERTILIZATIONZygote(2n)

Gametophyte

Newsporophyte

Maturesporophyte(2n)

Fiddlehead (young leaf)

Sporangium

Sorus

Sporangium

© 2011 Pearson Education, Inc.

Animation: Fern Life Cycle Right-click slide / select “Play”

Transport in Xylem and Phloem

• Vascular plants have two types of vascular tissue: xylem and phloem– Xylem conducts most of the water and minerals and

includes dead cells called tracheids– Water-conducting cells are strengthened by lignin and

provide structural support– Phloem consists of living cells and distributes sugars,

amino acids, and other organic products

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Evolution of Roots and Leaves

• Roots were originally underground stems• Leaves are organs that increase the surface area of

vascular plants, thereby capturing more solar energy that is used for photosynthesis

• Leaves are categorized by two types Microphylls, leaves with a single vein Megaphylls, leaves with a highly branched vascular system

• According to one model of evolution, microphylls evolved as outgrowths of stems

• Megaphylls may have evolved as webbing between flattened branches

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1 m

Figure 29.14

Vascular tissue Sporangia Microphyll

(a) Microphylls (b) Megaphylls

Overtoppinggrowth

Megaphyll

Otherstemsbecomereducedandflattened.

Webbingdevelops.

1 m

Seedless plant diversity

Selaginellamoellendorffii,a spike moss

Isoetesgunnii,a quillwort

Diphasiastrum tristachyum,a club moss

Strobili(clusters ofsporophylls)

2.5 cm

1 cm

1 m

Vascular plant diversity

Athyriumfilix-femina,lady fern

Equisetum arvense,field horsetail

Vegetative stem

Strobilus onfertile stem

Psilotumnudum,a whiskfern

4 cm

25 c

m

1.5

cm

Fern Lycophyte trees Horsetail

Tree trunkcovered withsmall leaves

Lycophyte treereproductivestructures

Applying ideas

How would the first large plants have affected global climate?

Processing the big points (flip your paper over)

• Can you name the derived traits of the colonizing land plants (mosses)?

• Can you name the derived traits of vascular, seedless plants (ferns)?

• What ancestral traits do plants share with the protists from which they split?

Processing the big points• Can you name the derived traits of the colonizing

land plants (mosses)?1. Alternation of generations

2. Walled spores produced in sporangia

3. Multicellular gametangia

4. Apical meristemsAs well as: cuticles, secondary compounds, symbioses

• Can you name the derived traits of vascular, seedless plants (ferns)?

• What ancestral traits do plants share with the protists from which they split?

Processing the big points

• Can you name the derived traits of the colonizing land plants (mosses)?

• Can you name the derived traits of vascular, seedless plants (ferns)?

1. Life cycles with dominant sporophytes

2. Vascular tissues called xylem and phloem

3. Well-developed roots and leaves

• What ancestral traits do plants share with the protists from which they split?

Processing the big points

• Can you name the derived traits of the colonizing land plants (mosses)?

• Can you name the derived traits of vascular, seedless plants (ferns)?

• What ancestral traits do plants share with the protists from which they split?– Chloroplasts– All eukaryotic cell functions and organelles

Gametophyte

Mitosis Mitosis

Spore Gamete

MEIOSIS FERTILIZATION

Zygote

Mitosis

Sporophyte

Haploid

Diploid

Alternation of generations

4

21

3

Apical meristemof shoot

Developingleaves

Apical meristems

Archegoniumwith egg

Antheridiumwith sperm

Sporangium Spores

Multicellular gametangia Walled spores in sporangia

n

n n

n

2n

1 m

Figure 29: summary of common traits