Presentation on theme: "Chapter 29 Plant Diversity I: The Colonization of Land AP Biology."— Presentation transcript:
Chapter 29 Plant Diversity I: The Colonization of Land AP Biology
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
General Characteristics of Plants Includes mosses, ferns, conifers, flowering plants Multicellular, eukaryotic, photosynthetic autotroph Chlorophyll a, b, and carotenoids Cellulose Starch
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.
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)
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.
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
Classified Into 2 Major Groups 1. 1.Nonvascular plants (aka Bryophytes) Bryophyta: mosses Anthocrophyta: Hornworts Heptophyta: Liverworts
Nonvascular Plants: Bryophytes GGGGametophyte dominant form LLLLack vascular tissues LLLLimits size (can’t grow tall) RRRRely on diffusion RRhizoids – –– – analogous to roots; used for anchorage MMMMale flagellated sperm produced by the gametangium (antheridium) FFFFemale egg produced by the gametangium (archegonium) SSSSporophyte produces haploid spores within sporangium 3333 Divisions: BBBBryophyta (mosses); ex: Sphagnum (peat moss) HHHHeptophyta (Liverworts); sexual and asexual reproduction AAAAnthocerophyta (hornworts)
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
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
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
DDDDivision Pterophyta FFFFerns – dominant seedless vascular plant LLLLarge leaves (fronds) – compound with smaller leaflets LLLLeaves are megaphylls – leaves with branched vascular tissues/veins HHHHomosporous SSSSporangia develop on specialized sporophylls SSSSporangia grow in clusters (sori) on underside FFFFlagellated sperm – require water & fertilization of egg in archegonium SSSSporophyte protected in archogonium and emerges from ground as fiddlehead