How Plants Colonized Land

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3

Apical

meristem

of shoot

Developing

leaves

Apical meristems

Apical meristem

of root

Root

100 µm

100 µm

Shoot

Derived Traits of Land Plants

Slide 16

A Vast Diversity of Modern Plants

Ancestral species gave rise to land plants which can be informally grouped based on the presence or absence of vascular tissue.

Nonvascular plants are commonly called bryophytes.

Most plants have vascular tissue; these constitute the vascular plants: seedless vascular and seed plants.

Slide 17

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.

Slide 18

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 / cone = sex organ

Angiosperms, the flowering plants including monocots and dicots / flower = sex organ

Slide 19

NonVascular and Vascular Plants

Slide 20

Highlights of Plant Evolution

Origin of land plants (about 475 mya)

1

2

3

1

2

3

Origin of vascular plants (about 420 mya)

Origin of extant seed plants (about 305 mya)

ANCES-

TRAL

GREEN

ALGA

Liverworts

Hornworts

Mosses

Lycophytes (club mosses,

spike mosses, quillworts)

Pterophytes (ferns,

horsetails, whisk ferns)

Gymnosperms

Angiosperms

Seed plants

Seedless

vascular

plants

Nonvascular

plants

(bryophytes)

Land plants

Vascular plants

Millions of years ago (mya)

500

450

400

350

300

50

0

Slide 21

NonVascular plants have life cycles dominated by gametophytes

Bryophytes are nonvascular and 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.

Gametophytes are dominant: larger and longer-living than sporophytes. Sporophytes are present only part of the time and dependent on the gametophytes.

Slide 22