Plant Diversity I: How Plants Colonized Land

Plant Diversity I: How Plants Colonized Land
Chapter 29 Plant Diversity I: How Plants Colonized Land

Figure 29.1 Figure 29.1 How did plants change the world? 1 m

1 m Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes
Figure 29.4 Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes Figure 29.4 Three possible “plant” kingdoms. Streptophyta Embryophytes Plantae 1 m

Derived Traits of Plants
Four key traits appear in nearly all land plants but are absent in the charophytes Walled spores produced in sporangia Apical meristems Embryophytes Alternation of generations and multicellular, dependent embryos © 2011 Pearson Education, Inc.

1 m Key Gamete from another plant Haploid (n) Gametophyte (n)
Figure 29.5a Key Gamete from another plant Gametophyte (n) Haploid (n) Diploid (2n) Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION 2n Zygote Figure 29.5 Exploring: Derived Traits of Land Plants Mitosis Sporophyte (2n) Alternation of generations 1 m

1 m Embryo Maternal tissue 10 m Figure 29.5ba
Figure 29.5 Exploring: Derived Traits of Land Plants 10 m 1 m

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 © 2011 Pearson Education, Inc.

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 Apical meristem of shoot Developing leaves
Figure 29.5e Apical meristem of shoot Developing leaves Apical meristems of plant roots and shoots Figure 29.5 Exploring: Derived Traits of Land Plants Apical meristem of root Root Shoot 100 m 1 m 100 m

1 m Apical meristem of root Root 100 m Figure 29.5ea
Figure 29.5 Exploring: Derived Traits of Land Plants Root 100 m 1 m

1 m Apical meristem of shoot Developing leaves Shoot 100 m
Figure 29.5eb Apical meristem of shoot Developing leaves Figure 29.5 Exploring: Derived Traits of Land Plants 1 m Shoot 100 m

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 © 2011 Pearson Education, Inc.

The Origin and Diversification of Plants
Fossil evidence indicates that plants were on land at least 475 million years ago Fossilized spores and tissues have been extracted from 475-million-year-old rocks © 2011 Pearson Education, Inc.

1 m (a) Fossilized spores Fossilized sporophyte tissue (b)
Figure 29.6 (a) Fossilized spores Figure 29.6 Ancient plant spores and tissue (colorized SEMs). Fossilized sporophyte tissue (b) 1 m

(a) Fossilized spores Figure 29.6a
Figure 29.6 Ancient plant spores and tissue (colorized SEMs).

Fossilized sporophyte tissue (b)
Figure 29.6b Fossilized sporophyte tissue (b) Figure 29.6 Ancient plant spores and tissue (colorized SEMs).

Those ancestral species gave rise to a vast diversity of modern plants
© 2011 Pearson Education, Inc.

1 m Figure 29.7 1 Origin of land plants (about 475 mya) 2
Origin of vascular plants (about 425 mya) 3 Origin of extant seed plants (about 305 mya) Liverworts Nonvascular plants (bryophytes) ANCESTRAL GREEN ALGA Land plants 1 Mosses Hornworts Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants 2 Pterophytes (ferns, horsetails, whisk ferns) Vascular plants Figure 29.7 Highlights of plant evolution. Gymnosperms 3 Seed plants Angiosperms 500 450 400 350 300 50 Millions of years ago (mya) 1 m

1 m 1 Origin of land plants (about 475 mya) 2
Figure 29.7a 1 Origin of land plants (about 475 mya) 2 Origin of vascular plants (about 425 mya) 3 Origin of extant seed plants (about 305 mya) Liverworts ANCESTRAL GREEN ALGA 1 Mosses Hornworts Lycophytes (club mosses, spike mosses, quillworts) 2 Pterophytes (ferns, horsetails, whisk ferns) Figure 29.7 Highlights of plant evolution. Gymnosperms 3 Angiosperms 1 m 500 450 400 350 300 50 Millions of years ago (mya)

1 m Liverworts Nonvascular plants (bryophytes) Land plants Mosses
Figure 29.7b Liverworts Nonvascular plants (bryophytes) Land plants Mosses Hornworts Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants Vascular plants Pterophytes (ferns, horsetails, whisk ferns) Figure 29.7 Highlights of plant evolution. Gymnosperms Seed plants Angiosperms 1 m

Most plants have vascular tissue; these constitute the vascular plants
Land plants can be informally grouped based on the presence or absence of vascular tissue Most plants have vascular tissue; these constitute the vascular plants Nonvascular plants are commonly called bryophytes Bryophytes are not a monophyletic group; their relationships to each other and to vascular plants are unresolved © 2011 Pearson Education, Inc.

Seedless vascular plants can be divided into clades
Lycophytes (club mosses and their relatives) Pterophytes (ferns and their relatives) Seedless vascular plants are paraphyletic, and are of the same level of biological organization, or grade © 2011 Pearson Education, Inc.

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 © 2011 Pearson Education, Inc.

Table 29. 1 Table 29.1 Ten Phyla of Extant Plants 1 m

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.

Nonvascular plants (bryophytes)
Figure 29.UN01 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Figure 29.UN01 In-text figure, p. 606 1 m

Bryophyte Gametophytes
In all three bryophyte phyla, gametophytes are larger and longer-living than sporophytes Sporophytes are typically present only part of the time © 2011 Pearson Education, Inc.

1 m “Bud” Male gametophyte (n) Key Haploid (n) Protonemata (n)
Figure “Bud” Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) “Bud” Spores Gametophore Spore dispersal Female gametophyte (n) Rhizoid Peristome Sporangium Seta Figure 29.8 The life cycle of a moss. MEIOSIS Capsule (sporangium) Mature sporophytes Foot 2 mm 1 m Capsule with peristome (LM) Female gametophytes

1 m Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n)
Figure Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) “Bud” Egg Spores Gametophore Spore dispersal Archegonia Female gametophyte (n) Rhizoid Peristome FERTILIZATION Sporangium Seta Figure 29.8 The life cycle of a moss. (within archegonium) MEIOSIS Capsule (sporangium) Mature sporophytes Foot 2 mm 1 m Capsule with peristome (LM) Female gametophytes

1 m Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n)
Figure Sperm “Bud” Antheridia Male gametophyte (n) Key Haploid (n) Protonemata (n) Diploid (2n) “Bud” Egg Spores Gametophore Spore dispersal Archegonia Female gametophyte (n) Rhizoid Peristome FERTILIZATION Sporangium Seta Figure 29.8 The life cycle of a moss. Zygote (2n) (within archegonium) MEIOSIS Capsule (sporangium) Mature sporophytes Foot Embryo Archegonium Young sporophyte (2n) 2 mm 1 m Capsule with peristome (LM) Female gametophytes

Capsule with peristome (LM)
Figure 29.8a Figure 29.8 The life cycle of a moss. 2 mm 1 m Capsule with peristome (LM)

The height of gametophytes is constrained by lack of vascular tissues
A spore germinates into a gametophyte composed of a protonema and gamete-producing gametophore The height of gametophytes is constrained by lack of vascular tissues Rhizoids anchor gametophytes to substrate Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium Sperm swim through a film of water to reach and fertilize the egg © 2011 Pearson Education, Inc.

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 Gametophore of female gametophyte Thallus Sporophyte Foot Seta
Figure 29.9a Gametophore of female gametophyte Thallus Sporophyte Foot Seta Capsule (sporangium) Marchantia polymorpha, a “thalloid” liverwort Figure 29.9 Exploring: Bryophyte Diversity 500 m Marchantia sporophyte (LM) Plagiochila deltoidea, a “leafy” liverwort 1 m

1 m Gametophore of female gametophyte Thallus
Figure 29.9aa Gametophore of female gametophyte Thallus Figure 29.9 Exploring: Bryophyte Diversity 1 m Marchantia polymorpha, a “thalloid” liverwort

Marchantia sporophyte (LM)
Figure 29.9ab Foot Seta Capsule (sporangium) Figure 29.9 Exploring: Bryophyte Diversity 500 m Marchantia sporophyte (LM) 1 m

Plagiochila deltoidea, a “leafy” liverwort
Figure 29.9ac Plagiochila deltoidea, a “leafy” liverwort Figure 29.9 Exploring: Bryophyte Diversity 1 m

1 m An Anthoceros hornwort species Sporophyte Gametophyte
Figure 29.9b An Anthoceros hornwort species Sporophyte Figure 29.9 Exploring: Bryophyte Diversity Gametophyte 1 m

1 m Polytrichum commune, hairy-cap moss
Figure 29.9c Polytrichum commune, hairy-cap moss Sporophyte (a sturdy plant that takes months to grow) Capsule Seta Figure 29.9 Exploring: Bryophyte Diversity Gametophyte 1 m

The Ecological and Economic Importance of Mosses
Mosses are capable of inhabiting diverse and sometimes extreme environments, but are especially common in moist forests and wetlands Some mosses might help retain nitrogen in the soil © 2011 Pearson Education, Inc.

Annual nitrogen loss (kg/ha)
Figure 29.10 RESULTS 6 5 4 Annual nitrogen loss (kg/ha) 3 2 Figure Inquiry: Can bryophytes reduce the rate at which key nutrients are lost from soils? 1 With moss Without moss 1 m

Peat can be used as a source of fuel
Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat Peat can be used as a source of fuel Sphagnum is an important global reservoir of organic carbon Overharvesting of Sphagnum and/or a drop in water level in peatlands could release stored CO2 to the atmosphere © 2011 Pearson Education, Inc.

1 m Peat being harvested from a peatland (a)
Figure 29.11 Figure Sphagnum, or peat moss: a bryophyte with economic, ecological, and archaeological significance. Peat being harvested from a peatland (a) “Tollund Man,” a bog mummy dating from 405–100 B.C.E. (b) 1 m

(a) Peat being harvested from a peatland 1 m
Figure 29.11a Figure Sphagnum, or peat moss: a bryophyte with economic, ecological, and archaeological significance. (a) Peat being harvested from a peatland 1 m

“Tollund Man,” a bog mummy dating from 405–100 B.C.E. (b)
Figure 29.11b Figure Sphagnum, or peat moss: a bryophyte with economic, ecological, and archaeological significance. “Tollund Man,” a bog mummy dating from 405–100 B.C.E. (b) 1 m

Concept 29.3: Ferns and other seedless vascular plants were the first plants to grow tall
Bryophytes and bryophyte-like plants were the prevalent vegetation during the first 100 million years of plant evolution Vascular plants began to diversify during the Devonian and Carboniferous periods Vascular tissue allowed these plants to grow tall Seedless vascular plants have flagellated sperm and are usually restricted to moist environments © 2011 Pearson Education, Inc.

1 m Nonvascular plants (bryophytes) Seedless vascular plants
Figure 29.UN03 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Figure 29.UN03 In-text figure, p. 610 1 m

Origins and Traits of Vascular Plants
Fossils of the forerunners of vascular plants date back about 425 million years These early tiny plants had independent, branching sporophytes Living vascular plants are characterized by Life cycles with dominant sporophytes Vascular tissues called xylem and phloem Well-developed roots and leaves © 2011 Pearson Education, Inc.

Figure 29.12 Sporangia Figure Sporophytes of Aglaophyton major, an ancient relative of present-day vascular plants. 1 m

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 © 2011 Pearson Education, Inc.

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

1 m Key Haploid (n) Diploid (2n) Spore dispersal MEIOSIS Sporangium
Figure Key Haploid (n) Diploid (2n) Spore dispersal MEIOSIS Sporangium Mature sporophyte (2n) Sporangium Sorus Figure The life cycle of a fern. Fiddlehead (young leaf) 1 m

1 m Key Haploid (n) Diploid (2n) Spore (n) Antheridium
Figure Key Haploid (n) Diploid (2n) Spore (n) Antheridium Young gametophyte Spore dispersal MEIOSIS Rhizoid Underside of mature gametophyte (n) Sporangium Sperm Archegonium Mature sporophyte (2n) Egg Sporangium FERTILIZATION Sorus Figure The life cycle of a fern. Fiddlehead (young leaf) 1 m

1 m Key Haploid (n) Diploid (2n) Spore (n) Antheridium
Figure Key Haploid (n) Diploid (2n) Spore (n) Antheridium Young gametophyte Spore dispersal MEIOSIS Rhizoid Underside of mature gametophyte (n) Sporangium Sperm Archegonium Mature sporophyte (2n) Egg New sporophyte Sporangium Zygote (2n) FERTILIZATION Sorus Figure The life cycle of a fern. Gametophyte Fiddlehead (young leaf) 1 m

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 Vascular tissue allowed for increased height, which provided an evolutionary advantage © 2011 Pearson Education, Inc.

Evolution of Roots Roots are organs that anchor vascular plants
They enable vascular plants to absorb water and nutrients from the soil Roots may have evolved from subterranean stems © 2011 Pearson Education, Inc.

Evolution of Leaves 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 © 2011 Pearson Education, Inc.

Megaphylls may have evolved as webbing between flattened branches
According to one model of evolution, microphylls evolved as outgrowths of stems Megaphylls may have evolved as webbing between flattened branches © 2011 Pearson Education, Inc.

1 m Overtopping growth Vascular tissue Sporangia Microphyll Megaphyll
Figure 29.14 Overtopping growth Vascular tissue Sporangia Microphyll Megaphyll Other stems become reduced and flattened. Webbing develops. Figure Hypotheses for the evolution of leaves. (a) Microphylls (b) Megaphylls 1 m

1 m Vascular tissue Sporangia Microphyll (a) Microphylls
Figure 29.14a Vascular tissue Sporangia Microphyll Figure Hypotheses for the evolution of leaves. (a) Microphylls 1 m

1 m Overtopping growth Megaphyll Webbing develops.
Figure 29.14b Overtopping growth Megaphyll Other stems become reduced and flattened. Webbing develops. Figure Hypotheses for the evolution of leaves. (b) Megaphylls 1 m

Sporophylls and Spore Variations
Sporophylls are modified leaves with sporangia Sori are clusters of sporangia on the undersides of sporophylls Strobili are cone-like structures formed from groups of sporophylls © 2011 Pearson Education, Inc.

All seed plants and some seedless vascular plants are heterosporous
Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual gametophyte All seed plants and some seedless vascular plants are heterosporous Heterosporous species produce megaspores, which give rise to female gametophytes, and microspores, which give rise to male gametophytes © 2011 Pearson Education, Inc.

Classification of Seedless Vascular Plants
There are two phyla of seedless vascular plants Phylum Lycophyta includes club mosses, spike mosses, and quillworts Phylum Pterophyta includes ferns, horsetails, and whisk ferns and their relatives © 2011 Pearson Education, Inc.

1 m 2.5 cm Isoetes gunnii, a quillwort
Figure 29.15a 2.5 cm Isoetes gunnii, a quillwort Strobili (clusters of sporophylls) Selaginella moellendorffii, a spike moss Figure Exploring: Seedless Vascular Plant Diversity 1 cm 1 m Diphasiastrum tristachyum, a club moss

Selaginella moellendorffii, a spike moss
Figure 29.15aa Selaginella moellendorffii, a spike moss Figure Exploring: Seedless Vascular Plant Diversity 1 m 1 cm

1 m Isoetes gunnii, a quillwort Figure 29.15ab
Figure Exploring: Seedless Vascular Plant Diversity 1 m

1 m 2.5 cm Strobili (clusters of sporophylls)
Figure 29.15ac 2.5 cm Strobili (clusters of sporophylls) Figure Exploring: Seedless Vascular Plant Diversity 1 m Diphasiastrum tristachyum, a club moss

1 m Athyrium filix-femina, lady fern
Figure 29.15b Athyrium filix-femina, lady fern Equisetum arvense, field horsetail Vegetative stem Strobilus on fertile stem 25 cm 1.5 cm Psilotum nudum, a whisk fern Figure Exploring: Seedless Vascular Plant Diversity 1 m 4 cm

Athyrium filix-femina, lady fern
Figure 29.15ba Athyrium filix-femina, lady fern Figure Exploring: Seedless Vascular Plant Diversity 25 cm 1 m

1 m Equisetum arvense, field horsetail Vegetative stem
Figure 29.15bb Equisetum arvense, field horsetail Vegetative stem Strobilus on fertile stem Figure Exploring: Seedless Vascular Plant Diversity 1.5 cm 1 m

1 m Psilotum nudum, a whisk fern 4 cm Figure 29.15bc
Figure Exploring: Seedless Vascular Plant Diversity 4 cm 1 m

Phylum Lycophyta: Club Mosses, Spike Mosses, and Quillworts
Giant lycophytes trees thrived for millions of years in moist swamps Surviving species are small herbaceous plants Club mosses and spike mosses have vascular tissues and are not true mosses © 2011 Pearson Education, Inc.

Phylum Pterophyta: Ferns, Horsetails, and Whisk Ferns and Relatives
Ferns are the most diverse seedless vascular plants, with more than 12,000 species They are most diverse in the tropics but also thrive in temperate forests Horsetails were diverse during the Carboniferous period, but are now restricted to the genus Equisetum Whisk ferns resemble ancestral vascular plants but are closely related to modern ferns © 2011 Pearson Education, Inc.

The Significance of Seedless Vascular Plants
The ancestors of modern lycophytes, horsetails, and ferns grew to great heights during the Devonian and Carboniferous, forming the first forests Increased growth and photosynthesis removed CO2 from the atmosphere and may have contributed to global cooling at the end of the Carboniferous period The decaying plants of these Carboniferous forests eventually became coal © 2011 Pearson Education, Inc.

1 m Tree trunk covered with small leaves
Figure 29.16 Tree trunk covered with small leaves Lycophyte tree reproductive structures Fern Lycophyte trees Horsetail Figure Artist’s conception of a Carboniferous forest based on fossil evidence. 1 m

Figure 29.UN02 Figure 29.UN02 In-text figure, p. 609 1 m

Homosporous spore production
Figure 29.UN04 Homosporous spore production Typically a bisexual gametophyte Eggs Sporangium on sporophyll Single type of spore Sperm Heterosporous spore production Megasporangium on megasporophyll Megaspore Female gametophyte Eggs Figure 29.UN04 In-text figure, p. 613 Microsporangium on microsporophyll Microspore Male gametophyte Sperm 1 m

1 m Apical meristem of shoot Developing leaves Gametophyte Mitosis
Figure 29.UN05 Apical meristem of shoot Developing leaves Gametophyte Mitosis Mitosis n n n Spore n Gamete MEIOSIS FERTILIZATION 2n Zygote Haploid Mitosis Diploid Sporophyte 1 Alternation of generations 2 Apical meristems Figure 29.UN05 Summary figure, Concept 29.1 Archegonium with egg Antheridium with sperm Sporangium Spores 1 m 3 Multicellular gametangia 4 Walled spores in sporangia

1 m Gametophyte Mitosis Mitosis n n n Spore n Gamete 2n Zygote
Figure 29.UN05a Gametophyte Mitosis Mitosis n n n Spore n Gamete MEIOSIS FERTILIZATION 2n Zygote Haploid Mitosis Figure 29.UN05a Summary figure, Concept 29.1 (part 1) Diploid Sporophyte 1 Alternation of generations 1 m

1 m Apical meristem of shoot Developing leaves Apical meristems 2
Figure 29.UN05b Apical meristem of shoot Developing leaves Figure 29.UN05b Summary figure, Concept 29.1 (part 2) 2 Apical meristems 1 m

Antheridium with sperm
Figure 29.UN05c Archegonium with egg Antheridium with sperm Figure 29.UN05c Summary figure, Concept 29.1 (part 3) 3 Multicellular gametangia 1 m

Walled spores in sporangia
Figure 29.UN05d Sporangium Spores Figure 29.UN05d Summary figure, Concept 29.1 (part 4) 4 Walled spores in sporangia 1 m

Figure 29.UN06 Figure 29.UN06 Test Your Understanding, question 9 1 m

Figure 29.UN07 Figure 29.UN07 Appendix A: answer to Concept Check 29.2, question 3 1 m

Figure 29.UN08 Figure 29.UN08 Appendix A: answer to Summary of Concept Check 29.1 question 1 m

Figure 29.UN09 Figure 29.UN09 Appendix A: answer to Test Your Understanding, question 8 1 m

Figure 29.UN10 Figure 29.UN10 Appendix A: answer to Test Your Understanding, question 9 1 m

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