Land plants:• origins• seedless plants

Biol 121, Fall 2010, Tom Buckley 22 Sep 10

Phylogeny of land plants Brown and golden algae

green algae

green algae

green algaeland plants

2n

embryo

Probable ancestor: algae at lake edges (periodic drying)

Plant evolution

aquaticancestors

land plants

nonvascularplants

seedlessvascularplants

vascularplants

seedplants

naked-seededplants

vessel-seededplants

greenalgae

mosses ferns conifers floweringplants

Diversification of land plants

# of spp

9,000

100

15,000

1,200

12,000

800

250,000Fig 29.7

seedless plants

seed plants

Diversification of land plants

gametophyte = dominant

sporophyte = dominant

Fig 29.7

Characters of land plants walled spores produced in sporangia

function of spores?

Characters of land plants apical meristems

function ofapicalmeristems?

Phylum Bryophyta (mosses)

Phylum Hepatophyta (liverworts)

Phylum Anthocerophyta (hornworts)

liverwort hornwort

bryophyte anatomy

hydroids leptoids

stem x.s.photosynthetic cells

leaf x.s.

bryophyte anatomy

photosynthetic cells

leaf x.s.

epidermis

hornwort stoma

Bryophyte life cycle

Fig 29.8

gametes produced in gametangia

male: antheridiafemale: archegonium

Bryophyte life cycle

Fig 29.8

Bryophyte life cycle

Fig 29.8

Bryophyte life cycle

Fig 29.8

Seedless vascular plants

Phylum Pterophyta (ferns, horsetails & relatives)

Phylum Lycophyta ("club mosses" & relatives)

Isoetes sp. ("quillwort") tree fern

Equisetum sp. ("horsetail")

Seedless vascular plants: new features

Vascular tissue

makes large plants possible

Sporophyte is dominant

Sporophylls: modified leaves that bear sporangia

permits complex reproductive structures

nonvascularvascular

Fern life cycle

Fern life cycle

Fern life cycle

Sporangium: spore container

Sorus (pl. sori) = cluster of sporangia indusium sorus

Sori

Horsetails (Equisetum) Strobilus (pl. strobili) = cluster of sporangia

sporophyll

sporangium

Horsetails (Equisetum)

Whisk fern (Psilotum) Synangium = cluster of 3 fused sporangia

Spike moss (Selaginella)

Phylum Lycophyta

Club moss (Lycopodium)

Q: What is the ploidy level of thetissues indicated by arrows?

(a) n n

(b) n 2n

(c) 2n n

(d) 2n 2n

A B

Moss (Phylum Bryophyta) A

B

Q: In which of the followingare gametes haploid?

(a) Phylum Bryophyta

(b) Phylum Pterophyta

(c) Phylum Lycophyta

(d) All of the above

Alternation of generations

meiosis

diploid

syngamy

haploid

diploid

haploid

meiosis

syngamy