1. Intro to Plants

2. Evolution of Land Plants
Land plants evolved from green algae
The green algae called charophyceans are the closest relatives of land plants
Comparisons of both nuclear and chloroplast genes
Point to charophyceans as the closest living relatives of land plants
Chara,
a pond
organism
(a)
10 mm
Coleochaete orbicularis, a disk-
shaped charophycean (LM)
(b)
40 µm

3. Origin and Diversification of Plants
Fossil evidence indicates that plants were on land at least 475 million years ago
Whatever the age of the first land plants those ancestral species gave rise to a vast diversity of modern plants

4. Seedless vascular plants
Plant Evolution
Bryophytes
(nonvascular plants)
Seedless vascular plants
Seed plants
Vascular plants
Land plants
Origin of seed plants
(about 360 mya)
Origin of vascular
plants (about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga
Charophyceans
Liverworts
Hornworts
Mosses
Lycophytes(club mosses, spike mosses, quillworts)
Pterophyte (ferns, horsetails, whisk fern)
Gymnosperms
Angiosperms

5. Bryophytes
Life cycles of mosses and other bryophytes are dominated by the gametophyte stage
Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants
Liverworts, phylum Hepatophyta
Hornworts, phylum Anthocerophyta
Mosses, phylum Bryophyta

6. Bryophytes LIVERWORTS (PHYLUM HEPATOPHYTA) Gametophore of
HORNWORTS (PHYLUM ANTHOCEROPHYTA)
MOSSES (PHYLUM BRYOPHYTA)
Gametophore of
female gametophyte
Marchantia polymorpha,
a “thalloid” liverwort
Foot
Sporangium
Seta
500 µm
Marchantia sporophyte (LM)
Plagiochila
deltoidea,
a “leafy”
liverwort
An Anthoceros
hornwort species
Sporophyte
Gametophyte
Polytrichum commune,
hairy-cap moss

7. Liverworts Have no true roots or shoots Non- vascular
Require water to reproduce
Have no or very little leaf structure
Cannot live in sporophyte form

8. Hornworts Free-floating aquatic plant, or land plant
No vascular tissue
No true leaves or roots
Can live in both gametophyte and sporophyte forms

9. Mosses Land plant Most have no vascular tissue
Majority to life spent in gametophyte
Need water to breed
No leaves or roots
Sporophytes are capsules on stalks

10. Vascular Plants Vascular plants have two types of vascular tissue
Xylem and phloem
Xylem
Conducts most of the water and minerals
Includes dead cells called tracheids
Phloem
Distributes sugars, amino acids, and other organic products
Consists of living cells

11. Vascular Plants Vascular plants have roots Vascular plants have leaves
Are organs that anchor vascular plants
Enable vascular plants to absorb water and nutrients from the soil
May have evolved from subterranean stems
Vascular plants have leaves
Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy for photosynthesis

12. Vascular Plants Two types of vascular plants: seedless and seeded
Seedless vascular plants form two phyla
Lycophyta, including club mosses, spike mosses, and quillworts
Pterophyta, including ferns, horsetails, and whisk ferns and their relatives
Modern species of lycophytes are relics from a far more eminent past
Are small herbaceous plants
Ferns
Are the most diverse seedless vascular plants

13. Seedless Vascular Plants
LYCOPHYTES (PHYLUM LYCOPHYTA)
PTEROPHYTES (PHYLUM PTEROPHYTA)
WHISK FERNS AND RELATIVES
HORSETAILS
FERNS
Isoetes
gunnii,
a quillwort
Selaginella apoda,
a spike moss
Diphasiastrum tristachyum, a club moss
Strobili
(clusters of
sporophylls)
Psilotum
nudum,
a whisk
fern
Equisetum
arvense,
field
horsetail
Vegetative stem
Strobilus on
fertile stem
Athyrium
filix-femina,
lady fern

14. Ferns Seedless vascular plants but do not have seeds
Common in shady areas, diverse in the tropics
Have flagellated sperm that require water to reach the eggs

15. Alternation of Generations
The seed plant life cycle contains both haploid and diploid stages
Diploid individuals are called sporophytes
Haploid individuals are called gametophytes
Does not happen in algae
May have evolved as an adaptation to harsh environments
Haploid cells divide into a cluster of cells before meiosis

16. Alternation of Generations
HAPLOID
Meiosis
Spores n
Mitosis
Gametophytes (male and female) n
Gametes (sperm and eggs) n
Fertilization
Zygote 2n
DIPLOID
Sporophyte 2n

17. Sporophytes (growing from gametophytes)
Dominant Gametophyte
Mosses have a dominant gametophyte stage
Sperm (n) (released from their gametangium) 1 2 3 4
Gametangium containing the egg (n) (remains within gametophyte)
Egg
Fertilization
Zygote (2n)
Mitosis and development
Sporophytes (growing from gametophytes)
HAPLOID
DIPLOID
Gametophyte (n)
Sporangium
Stalk
Meiosis
Spores (n) 5
Gametophytes (n)
Stopped here section 45 tuesday

18. Dominant Sporophyte Most plants have a dominant sporophyte stage 5 12 3 4
Gametophyte (n) (underside)
Sperm (n)
Egg (n)
Fertilization
Zygote (2n)
Mitosis and development
New sporophyte growing out of gametophyte
Sporophyte (2n)
Meiosis
Sporangia 5
Spores (n)
HAPLOID
DIPLOID

19. Seeded Vascular Plants
Gymnosperms- conifers, cycads, and ginkgo
Angiosperms- flowering plants