1. Chapter 29 Plant Diversity I: The Colonization of Land AP Biology

2. Requirements for Successful Life on Land  Supporting mechanism (vascular tissue, lignin)  Absorptive structures (above & below ground)  Conducting tissues (move fluids)  Anti-desiccation (drying out) adaptations for body of plant (cuticle) & gametes (pollen & spores)  Airborne gamete dispersal

3. General Characteristics of Plants  Includes mosses, ferns, conifers, flowering plants  Multicellular, eukaryotic, photosynthetic autotroph  Chlorophyll a, b, and carotenoids  Cellulose  Starch

4.  Alternation of generations (more next)  Most have stomata for gas exchange (Liverworts the exception)  Secrete cuticle to reduce desiccation  Most have vascular tissue for bulk transport of water and materials  Exchange of materials between adjacent cells through opening in cell walls (plasmodesmata)  Most have seeds (embryo with food & protective covering) General Characteristics of Plants, cont.

5. Alternation of Generations  Gametes produced & protected within (non- reproductive cells to prevent desiccation & for protection)  Gametes produced & protected within gametangia (non- reproductive cells to prevent desiccation & for protection)  Fertilization of egg takes place here (Female = archegonium; Male = antheridium)

6.  Sporophyte & gametophyte are structurally (look & develop) different ()  Sporophyte & gametophyte are structurally (look & develop) different (heteromorphic)  Both structures are multicellular (unlike animals)  Sporophyte dominant in most species  Meiosis in sporophyte produces haploid reproductive cells (spores)  Spores can develop into a new organism without fusing with another cell Alternation of Generations, cont.

8. Proposed Ancestors of Plants  Charophyceans are the green algae most related to land plants  Several lines of evidence support this including:  Homologous chloroplasts, cell walls, peroxisomes, sperm  Phragmoplasts – microtubules form perpendicular to cell plate and guide deposition of cellulose to form wall  Molecular systematics  Charophyceans had a layer of sporopollenin to prevent exposed zygotes from drying out until they are in water again

9. Classified Into 2 Major Groups 1. 1.Nonvascular plants (aka Bryophytes)  Bryophyta: mosses  Anthocrophyta: Hornworts  Heptophyta: Liverworts

10. 2. 2.Vascular Plants (aka Tracheophytes)   Seedless vascular plants (Pteridophytes)  Lycophyta: Lycophytes  Pterophyta: Ferns & Horsetails

11.   Seeded vascular plants  Naked seeded plants (Gymnosperms)  Coniferophyta: Conifers  Cycadophyda: Cycads  Gnetophyta: Gnetae  Ginkgophyta: Ginko

12.  Flowering plants and enclosed seeds (Angiophyta)  Flowering plants

14. Nonvascular Plants: Bryophytes GGGGametophyte dominant form LLLLack vascular tissues LLLLimits size (can’t grow tall) RRRRely on diffusion RRhizoids – –– – analogous to roots; used for anchorage MMMMale flagellated sperm produced by the gametangium (antheridium) FFFFemale egg produced by the gametangium (archegonium) SSSSporophyte produces haploid spores within sporangium 3333 Divisions: BBBBryophyta (mosses); ex: Sphagnum (peat moss) HHHHeptophyta (Liverworts); sexual and asexual reproduction AAAAnthocerophyta (hornworts)

15. Vascular Plants: Tracheophytes  Key adaptations to success on land:  Seeds – protect embryo & provide food for initial growth  Pollen – airborne dispersal; in walls of spores  Pollen – airborne dispersal; Sporopollenin in walls of spores  Sporophyte dominant  Vascular tissues – phloem & xylem; specialization of parts of plant for specific functions (true roots, stems, and leaves)  Ligninfied cell walls – supports plant in air

16. Seedless Vascular Plants  Division Lycophyta  Club mosses  Many are – grow on other plants but not parasitic  Many are epiphytes – grow on other plants but not parasitic  Sporangia produced on specialized leaves for reproduction called  Sporangia produced on specialized leaves for reproduction called sporophylls  Most species are – produce a single type of spore that can produce a gametophyte with antheridia and archegonia  Most species are homosporous – produce a single type of spore that can produce a gametophyte with antheridia and archegonia  species – have sporophytes that produce separate spores  Heterosporous species – have sporophytes that produce separate spores  Megaspores – produce female archegonia on female gametophyte  Microspores – produce male antherdia on male gametophyte

17.  Division Sphenophyta  Horsetail (Equisetum) – only extant genus  Homosporous  Silica in cell walls make stems abrasive  Gametophyte is free-living; can photosynthesize and not dependent on sporophyte for nutrients Seedless Vascular Plants

18. DDDDivision Pterophyta FFFFerns – dominant seedless vascular plant LLLLarge leaves (fronds) – compound with smaller leaflets LLLLeaves are megaphylls – leaves with branched vascular tissues/veins HHHHomosporous SSSSporangia develop on specialized sporophylls SSSSporangia grow in clusters (sori) on underside FFFFlagellated sperm – require water & fertilization of egg in archegonium SSSSporophyte protected in archogonium and emerges from ground as fiddlehead