Ch. 29 Diversity BIOL 221

Overview: The Greening of Earth

• First 3 billion years of Earth’s history

• The terrestrial surface was lifeless

• Since colonizing land

• have diversified into roughly 290,000 living species

Land plants evolved from • Green algae called charophytes

• are the closest relaves of land plants • Comparisons of both nuclear and chloroplast genes • point to charophytes as the closest living relaves of land plants

ANCESTRAL • Note ALGA Chlorophytes

• that land plants are not Streptophyta Charophytes descended from modern charophytes Plantae • but share a common ancestor with modern charophytes

1 Morphological and Molecular Evidence • Many characteriscs of land plants • also appear in a variety of algal clades • land plants share four key traits only with charophytes: 1. Rose-shaped complexes for cellulose synthesis 2. Peroxisome enzymes 3. Structure of flagellated sperm 4. Formaon of a phragmoplast

Adaptaons Enabling the Move to Land • Sporopollenin

• In charophytes

• polymer that prevents exposed zygotes from drying out

• Movement onto land

• Provided: unfiltered sun, more

plenful CO2, nutrient-rich soil, and few (any?) herbivores or pathogens

• Challenges: a scarcity of water and lack of structural support

Morphological and Molecular Evidence • The accumulaon of traits that facilitated survival on land

• may have opened way to colonizaon by plants

• Systemasts debang the boundaries of the plant

• Some think the plant kingdom should be expanded

• to include some or all green algae

• Unl resoluon

• we will retain the definion of kingdom Plantae

Red algae

ANCESTRAL Viridiplantae ALGA Chlorophytes Streptophyta Charophytes Plantae Plantae

Embryophytes

2 Derived Traits of Plants

• Four key traits appear in nearly all land plants

• but are absent in the charophytes:

1. Alternaon of generaons

• with mulcellular, dependent embryos

2. Walled spores produced in sporangia

3. Mulcellular gametangia

4. Apical meristems

Derived Traits of Plants

• alternaon of generaons Gametophyte Gamete from (n) another plant Mitosis Mitosis n • Plants alternate between two stages n n n • Gametophyte - haploid Spore Gamete

• produces haploid gametes by mitosis MEIOSIS FERTILIZATION • Sporophyte – diploid 2n Zygote • from fusion of the gametes Mitosis • produces haploid spores by meiosis Sporophyte (2n) • diploid embryo (zygote) Alternation of generations • retained within female gametophyte (haploid) • placental transfer cells

Embryo • Transfer nutrients from parent to embryo 2 µm Maternal tissue • Extra surface area for exchange • Embryophytes Wall ingrowths 10 µm Placental transfer cell • Land plants because of the dependency of the (outlined in blue) Embryo (LM) and placental transfer cell (TEM) embryo on the parent of Marchantia (a liverwort)

Walled Spores Produced in Sporangia

• Sporangia

• Organ on sporophyte that produces spores Spores Sporangium • Sporocytes

• Diploid cells in

sporangia Longitudinal section of Sphagnum sporangium (LM)

• undergo meiosis Sporophyte to generate Gametophyte haploid spores Sporophytes and sporangia of Sphagnum (a )

• contain sporopollenin

3 Mulcellular Gametangia

• Gametangia • Produce gametes

• Archegonia Archegonium Female gametophyte with egg • Female gametangia

• produce eggs and Antheridium are the site of with sperm ferlizaon Male • Antheridia gametophyte Archegonia and antheridia of Marchantia (a liverwort) • Male gametangia • site of sperm producon and release

Apical Meristems • Apical meristems

• Used by plants to sustain connual growth

• Cells differenate into various ssues

Apical Developing Apical meristems meristem leaves of shoot

Apical meristem Shoot 100 µm of root Root 100 µm

The Origin and Diversificaon of Plants • Fossil evidence

• indicates that plants were on land

• at least 475 million years ago

• Fossilized spores and ssues

• have been extracted from 475-million-year-old rocks

(a) Fossilized spores

(b) Fossilized sporophyte tissue

4 The Origin and Diversificaon of Plants

• Land plants can be informally grouped 1 Origin of land plants (about 475 mya) 2 Origin of vascular plants (about 420 mya) 3 Origin of extant seed plants (about 305 mya) () (bryophytes) plants Nonvascular • Based on the presence or Land plants Liverworts absence of vascular ANCES- 1 TRAL GREEN ssue ALGA Vascular plants (club mosses, plants vascular Seedless • Vascular plants spike mosses, quillworts) 2 Pterophytes (, horsetails, whisk ferns) Seed Seed plants • Have vascular 3 ssue Angiosperms

500 450 400 350 300 50 0 • Most plants Millions of years ago (mya)

• Bryophytes

• Nonvascular plants

The Origin and Diversificaon of Plants • Seedless vascular plants

• Can be divided into clades

– Lycophytes

– club mosses and their relaves

– Pterophytes

– ferns and their 1 Origin of land plants (about 475 mya) 2 Origin of vascular plants (about 420 mya) (bryophytes) (bryophytes) plants Nonvascular relaves 3 Origin of extant seed plants (about 305 mya) Land plants Liverworts

ANCES- 1 Hornworts TRAL – Seedless vascular plants are GREEN ALGA Mosses Vascular plants paraphylec Lycophytes (club mosses, plants vascular Seedless spike mosses, quillworts) 2 Pterophytes (ferns, horsetails, whisk ferns)

– And are of the same level of Seed plants Gymnosperms 3 biological organizaon Angiosperms

500 450 400 350 300 50 0 Millions of years ago (mya)

The Origin and Diversificaon of Plants • Seed

• an embryo and nutrients surrounded by a protecve coat

• Seed plants form a clade

• and can be divided into further clades:

1 Origin of land plants (about 475 mya) – Gymnosperms 2 Origin of vascular plants (about 420 mya) (bryophytes) (bryophytes) plants Nonvascular 3 Origin of extant seed plants (about 305 mya) Land plants Liverworts

“ ” ANCES- 1 Hornworts – naked seed plants, TRAL GREEN including the ALGA Mosses Vascular plants Lycophytes (club mosses, plants vascular Seedless spike mosses, quillworts) 2 Pterophytes (ferns, horsetails, whisk ferns)

– Angiosperms Seed plants Gymnosperms 3 Angiosperms

– flowering plants 500 450 400 350 300 50 0 Millions of years ago (mya)

5 life cycles dominated by gametophytes • Bryophytes

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

– Liverworts, phylum Hepatophyta

– Hornworts, phylum Anthocerophyta

– Mosses, phylum Bryophyta

• Mosses are most closely related to vascular plants

Bryophyte Gametophytes

• In all three bryophyte phyla

• gametophytes are larger and longer-living than sporophytes

• Sporophytes

• typically present only part of the me

Fig. 29-8-1

“Bud” Male Key gametophyte Haploid (n) (n) Diploid (2n) Protonemata (n) “Bud”

Spores Gametophore Spore Female dispersal gametophyte (n)

Rhizoid Peristome

Sporangium MEIOSIS Seta Mature Capsule sporophytes (sporangium) Foot 2 mm Capsule with Female peristome (SEM) gametophytes

6 Fig. 29-8-2 Raindrop

Sperm

“Bud” Antheridia Male Key gametophyte Haploid (n) (n) Diploid (2n) Protonemata (n) “Bud”

Egg

Spores Gametophore Archegonia Spore Female dispersal gametophyte (n)

Rhizoid Peristome

Sporangium FERTILIZATION MEIOSIS Seta (within archegonium) Mature Capsule sporophytes (sporangium) Foot 2 mm Capsule with Female peristome (SEM) gametophytes

Fig. 29-8-3 Raindrop

Sperm

“Bud” Antheridia Male Key gametophyte Haploid (n) (n) Diploid (2n) Protonemata (n) “Bud”

Egg

Spores Gametophore Archegonia Spore Female dispersal gametophyte (n)

Rhizoid Peristome

Sporangium FERTILIZATION MEIOSIS Seta (within archegonium) Zygote Capsule Mature (2n) sporophytes (sporangium) Foot Embryo

Archegonium

Young sporophyte

2 mm (2n) Capsule with Female peristome (SEM) gametophytes

Bryophyte Gametophytes • A spore germinates into a gametophyte

• composed of a protonema and gamete-producing gametophore

• Rhizoids

• Anchor gametophytes to substrate

• Lack of vascular ssues restricts the height of gametophytes

7 Bryophyte Gametophytes

Raindrop

• Mature gametophytes Sperm

“Bud” Antheridia Male Key gametophyte • produce flagellated Haploid (n) (n) Diploid (2n) Protonemata (n) sperm in antheridia and “Bud” Egg

Spores Gametophore Archegonia an egg in each Spore Female dispersal gametophyte (n)

Rhizoid archegonium Peristome

Sporangium FERTILIZATION MEIOSIS Seta (within archegonium) Zygote • Sperm swim through a film Capsule Mature (2n) sporophytes (sporangium) of water to reach and Foot Embryo Archegonium ferlize the egg Young sporophyte

2 mm (2n) Capsule with Female peristome (SEM) gametophytes

Bryophyte Sporophytes

Raindrop • Bryophyte sporophytes Sperm

“Bud” Antheridia Key Male gametophyte Haploid (n) (n) • grow out of archegonia Diploid (2n) Protonemata (n) “Bud” Egg Spores Gametophore • smallest and simplest Spore Female Archegonia dispersal gametophyte (n) Rhizoid sporophytes Peristome Sporangium FERTILIZATION MEIOSIS Seta (within archegonium) Capsule Zygote Mature (2n) sporophytes (sporangium) Foot Embryo • of all extant plant groups Archegonium Young sporophyte 2 mm Capsule with Female (2n) • consists of a foot, a seta (stalk), and peristome (SEM) gametophytes

a sporangium, Gametophore of Thallus female gametophyte

Sporophyte • also called a capsule

Foot • which discharges spores Seta through a peristome Capsule (sporangium) Marchantia polymorpha, a “thalloid” liverwort • and moss sporophytes have Marchantia sporophyte (LM) stomata for gas exchange 500 µ m

Plagiochila deltoidea, a “leafy” liverwort

An Anthoceros hornwort species

Sporophyte

Polytrichum commune, hairy-cap moss

Sporophyte Capsule (a sturdy plant that Gametophyte takes months Seta to grow)

Gametophyte

8 Ferns and other seedless vascular plants • Bryophytes and bryophyte-like plants • Dominated first 100 million years of plant evoluon

1 Origin of land plants (about 475 mya) • Vascular plants 2 Origin of vascular plants (about 420 mya) 3 Origin of extant seed plants (about 305 mya) (bryophytes) (bryophytes) plants Nonvascular Liverworts Land plants

• began to diversify during the ANCES- 1 Hornworts TRAL GREEN Devonian and Carboniferous ALGA Mosses Vascular plants periods Lycophytes (club mosses, plants vascular Seedless spike mosses, quillworts)

2 Pterophytes (ferns, • Vascular ssue horsetails, whisk ferns) Seed Seed plants Gymnosperms 3 • allowed these plants to grow Angiosperms

500 450 400 350 300 50 0 tall Millions of years ago (mya) • Seedless vascular plants • have flagellated sperm and are usually restricted to moist environments

Origins and Traits of Vascular Plants • Fossils of the forerunners of vascular plants

• date back about 420 million years

• These early ny plants had independent, branching sporophytes

• Living vascular plants are characterized by:

• Life cycles with dominant sporophytes

• Vascular ssues called xylem and phloem

• Well-developed roots and leaves

Life Cycles with Dominant Sporophytes • In contrast with bryophytes…

• sporophytes of seedless vascular plants are the larger generaon

• as in the

• …gametophytes

• are just ny plants that grow on or below the soil surface

9 Fig. 29-13-1

Key Haploid (n) Diploid (2n)

Spore MEIOSIS dispersal

Sporangium

Mature Sporangium sporophyte (2n) Sorus

Fiddlehead

Fig. 29-13-2

Key Haploid (n) Diploid (2n) Spore Young Antheridium Spore (n) gametophyte MEIOSIS dispersal

Sporangium Mature Sperm gametophyte (n) Archegonium Egg Mature Sporangium sporophyte (2n) FERTILIZATION Sorus

Fiddlehead

Fig. 29-13-3

Key Haploid (n) Diploid (2n) Spore Young Antheridium Spore (n) gametophyte MEIOSIS dispersal

Sporangium Mature Sperm gametophyte (n) Archegonium Egg Mature New Sporangium sporophyte Zygote sporophyte (2n) (2n) FERTILIZATION Sorus

Gametophyte

Fiddlehead

10 Transport in Xylem and Phloem

• Vascular plants have two types of vascular ssue:

• xylem and phloem

• Xylem

• conducts most of the water and minerals

• includes dead cells called tracheids

• strengthened by lignin and provide structural support

• Phloem

• Moves sugars, amino acids, and other organic products

• consists of living cells

Evoluon of Roots • Roots

• Organs that anchor vascular plants

• enable vascular plants to absorb water

• and nutrients from the soil

• And deliver those nutrients up a taller/larger plant

• May have evolved from subterranean stems

Evoluon of Leaves • Organs that increase the surface area for capturing light • Leaves are categorized by two types:

– Microphylls

– leaves with a single vein – Megaphylls

– leaves with a highly branched vascular system

• According to the fossil record • microphylls evolved first (410 vs. 370 mya)

• as outgrowths of stems

11 Sporophylls and Spore Variaons

• Sporophylls

• modified leaves with sporangia

• Sori

• clusters of sporangia on the undersides of sporophylls

• Strobili

• cone-like structures formed from groups of sporophylls

Sporophylls and Spore Variaons • homosporous

• produce one type of spore that develops into a bisexual gametophyte

• Most seedless vascular plants - ferns

• heterosporous

• produce megaspores that give rise to female gametophytes

• and microspores that give rise to male gametophytes

• All seed plants and some seedless vascular plants

Homosporous spore production

Typically a Sporangium Single Eggs on sporophyll type of spore bisexual gametophyte Sperm

Heterosporous spore production Megasporangium Megaspore Female Eggs on megasporophyll gametophyte

Microsporangium Microspore Male Sperm on microsporophyll gametophyte

Classificaon 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 relaves

Lycophytes (Phylum Lycophyta) 2.5 cm

Isoetes Strobili gunnii, (clusters of a quillwort sporophylls) apoda, a spike moss cm

Diphasiastrum tristachyum, a club moss 1

12 Fig. 29-15e

Pterophytes (Phylum Pterophyta)

Athyrium Psilotum filix-femina, arvense, nudum, lady fern field a whisk horsetail fern

Vegetative stem

Strobilus on fertile stem 25 cm 1.5 cm 2.5 cm

Phylum Lycophyta:

• Giant lycophytes

• thrived for millions of years in moist swamps

• Surviving species are small herbaceous plants

• Club mosses and spike mosses have vascular ssues

• and are not true mosses

Phylum Lycophyta: • Ferns • most diverse seedless vascular plants • more than 12,000 species • Horsetails • diverse during the Carboniferous period • now restricted to the genus Equisetum • Whisk ferns • resemble ancestral vascular plants • but are closely related to modern ferns

13 The Significance of Seedless Vascular Plants • Ancestors of modern lycophytes, horsetails, and ferns

• grew to great heights during the Devonian and Carboniferous

• forming the first forests

• Increased photosynthesis

• may have helped produce the global cooling

• at the end of the Carboniferous period

• The decaying plants of these Carboniferous forests eventually became coal

You should now be able to:

1. Describe four shared characteriscs and four disnct characteriscs between charophytes and land plants

2. Disnguish between the phylum Bryophyta and bryophytes

3. Diagram and label the life cycle of a bryophyte

4. Explain why most bryophytes grow close to the ground and are restricted to periodically moist environments 5. Describe three traits that characterize modern vascular plants and explain how these traits have contributed to success on land 6. Explain how vascular plants differ from bryophytes 7. Disnguish between the following pairs of terms: microphyll and megaphyll; homosporous and heterosporous 8. Diagram and label the life cycle of a seedless

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