Plant Diversity Chapter 29-30

Evolution Evolved from green algae ancestor Charophytes (green algae) Closest plant relative Over 470 million years ago

Evolution Similarities shared with algae Autotrophs Multicellular eukaryotes Cellulose in cell walls Chlorophyll a and b

Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes Fig. 29-4 Red algae ANCESTRAL ALGA Chlorophytes Viridiplantae Charophytes Figure 29.4 Three possible “plant” kingdoms Streptophyta Embryophytes Plantae

Evolution Traits derived by plants 1. Embryophytes Embryos develop in maternal tissues 2. Sporangia Walled spores 3. Multicellular gametangia 4. Apical meristems

Evolution Move to land-less water Cuticle: Waxy substance - protects water loss Stomata (stoma-singular): Opening in leaf Gas exchange

Evolution Leaves Dominant diploid phase Shorter haploid stage Yields greater photosynthesis surface Dominant diploid phase Shorter haploid stage Structural support of vascular tissue

(a) Fossilized spores (b) Fossilized sporophyte tissue Fig. 29-6 Figure 29.6 Ancient plant spores and tissue (colorized SEMs) (b) Fossilized sporophyte tissue

Alternation of generations Fig. 29-5a Gamete from another plant Gametophyte (n) Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote 2n Figure 29.5 Derived traits of land plants Mitosis Sporophyte (2n) Alternation of generations

Apical meristem of shoot Developing leaves Apical meristems Fig. 29-5e Apical meristem of shoot Developing leaves Apical meristems Figure 29.5 Derived traits of land plants Apical meristem of root Shoot Root 100 µm 100 µm

Life cycles Alteration of generations Multicellular haploid & diploid Brown, green & red algae have similar life cycle

Life cycle Gametophyte: “gamete plant” Haploid generation Produce haploid gametes through mitosis Fuse during fertilization (zygote)

Life cycle Sporophyte: ”spore plant” Diploid generation Meiosis produces haploid spores Leads to multicellular haploid gametophyte

Life cycle Sporangia Where meiosis takes place Diploid produces 4 haploid spores Multicellular haploid gametophyte

Life cycle Gametangia: Structures where gametes are produced Mosses Large part of life cycle is haploid Vascular plants gametophyte is much smaller

Alternation of generations Fig. 29-5a Gamete from another plant Gametophyte (n) Mitosis Mitosis n n n n Spore Gamete MEIOSIS FERTILIZATION Zygote 2n Figure 29.5 Derived traits of land plants Mitosis Sporophyte (2n) Alternation of generations

Life cycle Seed plants Gametophyte are nutritionally dependent on the sporophytes Gametophyte generation gets smaller More specialized for land

Plant diversity Nonvascular plants: Lack vascular tissue Contain water-conducting xylem Food-conducting phloem Stems, leaves and roots

Groups 1. Nonvascular land plants 2. Seedless vascular plants Mosses, liverworts, hornworts 2. Seedless vascular plants Club mosses Ferns 3. Gymnosperms (naked seed) 4. Angiosperms (flowering plants)

Figure 29.7 Highlights of plant evolution 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) Liverworts Nonvascular plants (bryophytes) Land plants ANCES- TRAL GREEN ALGA 1 Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants 2 Vascular plants Pterophytes (ferns, horsetails, whisk ferns) Figure 29.7 Highlights of plant evolution Gymnosperms 3 Seed plants Angiosperms 500 450 400 350 300 50 Millions of years ago (mya)

Table 29-1 Table 29.1

Liverworts, hornworts

Seedless vascular plants

Gymnosperms

Angiosperms

Nonvascular land plants Usually small Lack vascular tissue to carry water to aerial parts of the plant Found in damp, shady habitats Need water to reproduce sexually Gametophytes are photosynthetic More visible (green) Sporophytes are attached to the gametophytes

Nonvascular land plants Mosses (Bryophytes) Rhizoids: “roots” Cells to absorb water “leaves” Green, haploid, single cell layer thick Most abundance in the tropics Very sensitive to air pollution

Moss

Seedless vascular plants Earliest form of vascular plants Need external water for fertilization No seeds Sporophyte more complex Both sporophyte & gametophyte are photosynthetic Live independently

Ferns

Seed plants 425 million years ago Seeds gives the plant advantages 1. Protection of embryo by sporophyte 2. Easier to disperse 3. Dormant stage

Seed plants 2 kinds of gametophytes Male (pollen grains) Female (ovule) No need for external water Sperm move to egg in a pollen tube

Gymnosperms Gymnos Greek for “naked” Sperma “with seed” Lack flowers and fruit Ovules are naked at time of pollination Pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods.

Angiosperms Flowering plants Ovules are closed by diploid tissues at time of fertilization Angeion means “vessel” in Greek Sperma “seed”

Flower structure Receptacle: Where flower parts are attached Sepals: Green leaf like Protect the immature flower

Flower structure Petals: Colored, attract pollinators Stamens (male gametophytes) Anther: Pollen producing Filament: a stalk Carpels (female gametophytes) Ovule(base), ovary, stigma and style (connects the stigma to the ovary)

Flower structure

Life cycle Pollination Pollen transfers to the stigma Self-pollination or from another plant Produce a germinating seed Young sporophyte (diploid)

Life cycle

Benefits Food Rice, wheat, potatoes Coffee, tea, cocoa Medicines Digitalis (heart med) Morphine (pain relief) Fuel Wood