Early-bird Special The following terms refer to alternation of generation: Homosporous ( one type of spore. a single type of spore produces a single type of gametophyte which produces both male and female gametes) Heterosporous ( different spore types. one type of gametophyte produces male gametes while another type produces female gametes) Kingdom Plantae Unifying Characteristics Multicellular eukaryotes photosynthetic autotrophs Chlorophyll A & B cell walls of cellulose produce gametes w/in a gametangia Exhibit alternation of generation with sporic meiosis (figure 33.4)
Note: spores develop into gametophyte Gametophyte produces gametes Sporophyte produces spores! Zygote produced by fusion of gametes Kingdom Plantae Four Major Steps in Evolution of Land Plants Protection from desiccation waxy cuticle protected gametangia male = antheridia female = archegonium Vascular tissue Seeds Flowers
Characteristics Kingdom Plantae Non-Vascular Plants have waxy cuticles & jacketed gametes lack true vascular tissue retain flagellated sperm dominance of gametophyte (1N) generation sporophyte nutritionally dependent on gametophyte Three phyla of non-vascular plants Hepaticophyta (liverworts) Bryophyta (mosses) Anthocerotophyta (hornworts) Is this Liverwort homosporous or heterosporous? Male gametophyte Female gametophyte
Gemmae cups are a means of asexual reproduction in liverworts Life cycle of moss (fig 33.7) Sporophyte (2N) generation is not free-living Flagellated sperm swims to find egg Gametophyte (1N) generation dominates life history
Kingdom Plantae Vascular, Seedless Plants Need for vascular system Two-part vascular system Xylem- water transport Phloem- transport organic compounds Kingdom Plantae Vascular, Seedless Plants Characteristics of vascular, seedless plants have vascular tissue, but lack seed life cycle dominated by sporophyte generation retain free-living gametophyte generation retain flagellated sperm most groups are homosporous Geologic importance of seedless plants
Kingdom Plantae Vascular, Seedless Plants Four phyla of vascular, seedless plants Psilophyta (wisk ferns) simplest vascular plant lacks true roots or leaves Lycophyta (club mosses) resurrection plant of desert areas quillworts are simple aquatic plants Arthrophyta, the horsetails scouring rushes due to silica deposits in stems lack photosynthetic leaves branched photosynthetic stems resemble horse tail Pterophyta, the ferns Kingdom Plantae Vascular, Seedless Plants widely distributed and huge diversity of forms Giant Salvinia is a floating fern that will cause huge ecological problems in Texas
Homosporous, freeliving gametophyte Life cycle of fern (fig 33.13) Life cycle dominated by sporophyte
Kingdom Plantae - Seed Plants First developed some 360 mybp, but quickly dominated land environment Characteristics of seed plants dominance of sporophyte (2N) generation heterosporous alternation of generation gametophyte is parasitic on sporophyte pollen replaces flagellated sperm developing embryo is packaged into a seed Two categories of seed plants Gymnosperms (naked seed plants) Angiosperms (flowering plants) Kingdom Plantae - Gymnosperms Four phyla of gymnosperms Gnetophyta- weird group - no info! Ginkgophyta (Ginkgos)- single, very hardy species Cycadophyta (Cycads)- palm-like plants of tropical & subtropical areas Coniferophyta (Conifers)- cone bearing plants, by far dominant gymnosperm
Ginkgophyta (Ginkgos)- Cycadophyta (Cycads)- Kingdom Plantae - Gymnosperms Confiferophyta Many common trees (pines, redwoods, sequoias) Heterosporous- produce 2 types of cones ovulate cone (female) megaspore mother cell (2N) produces megaspore (1N) megaspore divides to produce multicellular megagametophyte one cell specializes as an egg cell pollen cone (male) produces hundreds of pollen grains (microgametophytes)
female cone Male cone pollination fertilization seed Female gametophyte not free-living Sporophyte dominant
Kingdom Plantae - Phylum Anthophyta Characterized by development of a flower By far the most successful modern plant Angiosperms are composed of two classes monocots (grasses, orchids, palms) dicots (broadleaf plants) Remainder of botany section will focus on angiosperms