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Create a timeline with the following events:
Earth is born First life Multicellularity Colonization of land First vascular plants First insects Dinosaurs Flowering plants
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Create a timeline with the following events:
Earth is born 4.6 bya First life 3.8 bya Multicellularity 1 bya Colonization of land 500 mya (or 1.2 bya) First vascular plants 425 mya First insects 400 mya Dinosaurs 300 mya Flowering plants 130 mya
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Plant Diversity I: How Plants Colonized Land
Chapter 29 Plant Diversity I: How Plants Colonized Land
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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)
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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 © 2011 Pearson Education, Inc.
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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.
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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
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Derived Traits of Plants
Four key traits appear in nearly all land plants but are absent in the charophytes Alternation of generations Walled spores produced in sporangia Multicellular gametangia Apical meristems © 2011 Pearson Education, Inc.
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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 © 2011 Pearson Education, Inc.
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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 © 2011 Pearson Education, Inc.
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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
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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 © 2011 Pearson Education, Inc.
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Figure 29.5c Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Figure 29.5 Exploring: Derived Traits of Land Plants Sporophyte Gametophyte 1 m Sporophytes and sporangia of Sphagnum (a moss)
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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.
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1 m Female gametophyte Archegonia, each with an egg (yellow)
Figure 29.5d Female gametophyte Archegonia, each with an egg (yellow) Antheridia (brown), containing sperm Figure 29.5 Exploring: Derived Traits of Land Plants Male gametophyte Archegonia and antheridia of Marchantia (a liverwort) 1 m
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4. Apical Meristems Plants sustain continual growth in their apical meristems Cells from the apical meristems differentiate into various tissues © 2011 Pearson Education, Inc.
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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
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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.
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Know plant types, and key distinguishing elements
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 Know plant types, and key distinguishing elements
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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 © 2011 Pearson Education, Inc.
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Seed plants form a clade and can be divided into further clades
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
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Table 29. 1 Table 29.1 Ten Phyla of Extant Plants 1 m
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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.
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Nonvascular plants (bryophytes)
Figure 29.UN01 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Figure 29.UN01 In-text figure, p. 606 1 m
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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.
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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
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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
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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
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Animation: Moss Life Cycle Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
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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.
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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
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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
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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
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Annual nitrogen loss (kg/ha)
Can bryophytes reduce the rate at which key nutrients are lost from soils? 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
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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
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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.
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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
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Derived Traits of Vascular Plants
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.
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Figure 29.12 Sporangia Figure Sporophytes of Aglaophyton major, an ancient relative of present-day vascular plants. 1 m
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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.
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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
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Animation: Fern Life Cycle Right-click slide / select “Play”
© 2011 Pearson Education, Inc.
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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 © 2011 Pearson Education, Inc.
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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 © 2011 Pearson Education, Inc.
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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
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Seedless plant diversity
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
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Vascular plant diversity
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
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How would the first large plants have affected global climate?
Applying ideas 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. How would the first large plants have affected global climate?
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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?
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Processing the big points
Can you name the derived traits of the colonizing land plants (mosses)? Alternation of generations Walled spores produced in sporangia Multicellular gametangia Apical meristems As 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?
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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)? Life cycles with dominant sporophytes Vascular tissues called xylem and phloem Well-developed roots and leaves What ancestral traits do plants share with the protists from which they split?
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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
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Figure 29: summary of common traits
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
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