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•  Seedless Plants and transition to land –  Origin of plants –  Alternation of generations

•  Spores and gametes

•  Bryophytes –  Mosses, liverworts, hornworts –  General Life cycle

•  Vascular system allows plants to get tall –  Lycophytes –  Ferns etc –  Life cycle

26 June 2019

Silurian

Seedless Plants Eukaryotes Diplomonads

Parabasalids

Euglenozoans

Stramenopiles

Alveolates

Rhizarians

algae G

reen

Am

oebozoans Opisthokonts

Excavata

Diatoms

Golden algae

Brown algae

Dinoflagellates SAR

Apicomplexans

Ciliates

Radiolarians

Forams

Cercozoans

Red algae

Chlorophytes

Charophytes

Plants

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Choanoflagellates

Animals

Unikonta

Archaeplastida

Ch 29-30 Plants, etc è

Green Algae Red Algae

Glaucophytes (unicellular)

Red Algae

“Green Algae”

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Derived Traits of Land Plants Some key traits appear in nearly all land plants but

are absent in the charophytes: •  Alternation of generations •  Walled spores produced in sporangia •  Multicellular gametangia •  Waxy cuticle

Alternation of Generations

Gametophyte (n)

Gamete from another plant

n

n

Mitosis

Gamete

FERTILIZATION MEIOSIS

Mitosis

Spore n

n

2n Zygote

Mitosis

Sporophyte (2n)

Water-borne spores → protected spores

475-million year old

spore fossils!

Trilete spores of Lycopodium

475-million year old

spore fossils!

Protective organs for gamete production

Archegonium – eggs Antheridium - sperm

Fig. 29-5e

Apical meristem of shoot

Developing leaves

Apical meristems

Apical meristem of root Root 100 µm 100 µm Shoot

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cuticle

The first land plants were probably moss-like

(bryophytes) plants N

onvascular

Plants

Liverworts

Origin of land plants (about 470 mya) ANCESTRAL GREEN ALGA

Mosses

Hornworts

plants vascular Seedless

Vascular plants

Lycophytes

Origin of vascular plants (about 425 mya) Ferns, etc

Gymnosperms Origin of seed plants (about 360 mya)

Angiosperms

500

Seed plants

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

1

2

3

Seedless Plants Silurian

Bryophytes

•  Liverworts •  Hornworts •  Mosses

Mosses Haploid (n) Diploid (2n)

Sperm Antheridia

Male gametophyte (n)

Egg

Spores

Embryo

2 m

m

Zygote (2n)

Archegonia Female gametophyte (n)

Sporangium

MEIOSIS Mature sporophytes

Female gametophytes

Young sporophyte (2n)

Moss Life Cycle

Fertilization

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The empty niche – vertical growth

•  Key innovation – vascular tissue for movement of nutrients against gravity

xylem

phloem

Fossil vascular plant (420 million years ago)

Branching, independent sporophyte

Vascular system allowed the evolution of wood and leaves

(bryophytes) plants N

onvascular

Plants

Liverworts

Origin of plants ANCESTRAL GREEN ALGA

Mosses

Hornworts

plants vascular Seedless

Vascular plants

Lycophytes

Origin of vascular plants Ferns, etc.

Gymnosperms Origin of seed plants

Angiosperms

500

Seed plants

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

1

2

3

Vascular systems permitted evolution of new specialized plant organs

Roots

Leaves

Lycophytes

Ferns

Horsetails

Three main groups: The Geologic Timetable

<Carboniferous

Seedless Vascular Plants became dominant in the Carboniferous period, about 350 mya

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Early vascular plant forest, carboniferous period (300 million years ago) Carboniferous

Figure 29.15

Horsetail Fern

Vascular Plants

The Lycophytes: spore-dispersed plants with microphylls

Lycophytes Ferns etc Seed Plants

microphylls

Here are two Lycophytes you can find in Vermont

Ground cedar Shining clubmoss

Lepidodendron - the scale tree of the Carboniferous coal swamp

The remains of the Carboniferous scale trees form the great coal deposits of the world

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Vascular Plants

The Ferns and friends: spore-dispersed plants with true leaves (megaphylls)

megaphylls

Lycophytes Ferns etc Seed Plants Figure 21.10 Evolution of Leaves

Ferns - the second-most diverse group of vascular plants

ca. 12,500 species

Homospory and Heterospory

Clumps of sporangia (sori) on the underside of a fern leaf

Fig. 29-13-3

Key

Haploid (n) Diploid (2n)

MEIOSIS Spore dispersal

Sporangium

Sporangium Mature sporophyte (2n)

Sorus

Fiddlehead

Spore (n)

Young gametophyte

Mature gametophyte (n) Archegonium

Egg

Antheridium

Sperm

FERTILIZATION New sporophyte

Gametophyte

Zygote (2n)

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Bryophyte Pteridophytes Gymnosperm Angiosperm

All land plants alternate generations, although the gametophyte became less and less prominent

Fern gametophyte with new sporophyte

ca. 5 mm

Horsetails

Scouring rush

Field horsetail

Moss

Fern

The green part of the moss is _______ and the green part of the fern is ________.

A.  Haploid; Haploid B.  Haploid; Diploid C.  Diploid; Haploid D.  Diploid; Diploid E.  I don’t know

The Geologic Timetable

<Permian Climate was warming and drying … not a great time to be a spore-dispersed plant!

Vascular Plants

Clubmosses and friends

Ferns and Friends

Seed Plants

megaphylls

seeds

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Jurassic