BIOL 1030 – TOPIC 3 LECTURE NOTESTopic 3: Plant Diversity I (Ch. 29)I. Kingdom Plantae – general characteristicsA. eukaryotic, multicellular, with cell walls rich in celluloseB. most are photosynthetic, with chloroplasts containing chlorophylls a and b and carotenoidsC. all have alternation of generationsD. dominate nearly all terrestrial communities (exceptions in tundra); major producers in most of these habitatsE. source of food, shelter, clothing, much of the atmosphere’s oxygenF. ~300,000 described living species in 10 phylaG. two groups: 1. nonvascular plants (a grade) and vascular plants (a clade)2. vascular plants divided into those without seeds (a grade) and those with seeds (a clade)II. Evolutionary origin and adaptations to landA. related to green algae1. chloroplast similarity2. cellulose in cell walls3. starch as energy reserve4. formation of cell plate during division (found in plants and some green algae)5. genetic similarities (especially ribosomal RNA sequence); plant clade is ~500 million years old6. distinguished from green algae because diploid form always begins development within tissues of a haploid form, and always have heteromorphic (different-looking) haploid and diploid forms7. also distinguished by adaptations to survival on land, including protecting embryos B. revised classification: Kingdom Viridiplantae1. cladistic analysis shows no clear division between plants (traditional Kingdom Plantae) and green algae (traditional Phylum Chlorophyta)2. instead, traditional land plants together with some green algae apparently form a monophyletic group called Streptophyta1 of 10BIOL 1030 – TOPIC 3 LECTURE NOTES3. the Streptophyta together with the rest of the green algae apparently form a monophyletic group, the proposed (and increasingly accepted) Kingdom Viridiplantae (or Viridaeplantae)C. adaptations to land1. plants are primarily terrestrial – few aquatic species2. plants likely first terrestrial organisms3. cell wall helps prevent water loss (desiccation)4. embryos (young sporophyte plants) protected by some sort of covering to protect against things like desiccation5. most plants have a waxy cuticle – on exposed surfaces, relatively impermeable; prevents most water loss6. cuticle creates a problem with gas exchange, so most plants have stomata (singular: stoma)- pores that can be opened and closed for gas exchange- up to thousands per square centimeter on leaves- closing helps prevent water loss- must open to let carbon dioxide in, oxygen out7. mycorrhizal relationships with fungi- found in about 90% of plant species, some absolutely required- may help some with water uptake- help tremendously with nutrient uptake8. other adaptations in some plants- vascular tissue and related structures (roots, shoots, leaves)- seeds- flowers and fruitsIII. Plant Life Cycles Again you just have to know the life cyclesA. alternation of generations – mitosis in both haploid and diploid generations1. sporophyte = multicellular diploid organism; makes spores via meiosis2. gametophyte = multicellular haploid organism; makes gametes via mitosis3. plants make meiospores, but never mitospores4. meiosporangia in sporophyte produces diploid meiospore mother cells (meiosporocytes)5. meiosporocyte undergoes meiosis to produce four haploid meiospores 6. every “meio-” above is often left off since there are no mitospores; thus, sporangia, spore mother cells, sporocytes, and spores7. meiospores divide by mitosis, forming gametophyte2 of 10BIOL 1030 – TOPIC 3 LECTURE NOTES8. gametophyte produces haploid gametes in special gametangia structures in some plants- antheridium – male gametangia, make sperm- archegonium – female gametangia, make eggs9. sperm and egg fuse inside archegonium to form diploid zygote10. zygote grows into sporophyte; young sporophyte = embryo11. other activities occur in some groups, these will be discussed when those groups are covered12. evolutionary trend from “lower” to “higher” plants is a reduction of the gametophyte generation and an expansion of the sporophyte generation, with more protection of the embryo- nonvascular plants (mosses, liverworts, hornworts) – gametophyte is green, free-living, dominant generation- seedless vascular plants (ferns and fern allies) – gametophyte is usually green and free-living, but sporophyte is dominant generation- vascular seed plants (gymnosperms and angiosperms) – gametophyte is nutritionally dependent on sporophyte, or may be saprobic (deriving energy from nonliving organic matter); sporophyte is dominant generationIV. Nonvascular PlantsA. plants lacking specialized tubes for conducting water and nutrients (that is, lacking vascular tissue)B. gametophytes photosynthetic and free-living; dominant generationC. sporophytes are attached to and dependent on gametophytes D. primitive; likely the modern plants most similar to the “first plants”E. require external water for sperm to reach eggs for sexual reproduction (swimming sperm)F. no true leaves, stems, or roots (vascular tissue required for true leaves, stems, and roots)G. small; rarely more than 7 cm tallH. most common in and mostly limited to moist placesI. sometimes called bryophytesJ. three phyla:1. Phylum Hepatophyta – liverworts2. Phylum Anthocerophyta – hornworts3. Phylum Bryophyta – mosses3 of 10BIOL 1030 – TOPIC 3 LECTURE NOTESV. Phylum Hepatophyta – liverwortsA. some with flattened bodies (thalli) with lobes resembling liver; “wyrt” is old English for plant; thus, “liverwort” B. thalloid forms only 20% of phylum; rest look like mossesC. simpler than mosses1. gametophytes develop almost directly from spores (reduced protonema)2. gametophyte growth is prostrate (flat), not erect3. rhizoids are one-celledD. sexual reproduction similar to that in mosses; two small differences:1. antheridia on stalks called antheridiophores2. archegonia on stalks called archegoniophoresE. asexual reproduction occurs in thalloid forms from gemmae splashed out of gemma cups on “leaves”F. about 9,000 living speciesVI. Phylum Anthocerophyta – hornwortsA. thalloid gametophytes (look much like thalloid liverworts)B. cells typically have a single chloroplast, very much like the chloroplast of green algaeC. sporophyte partially independent from gametophyte1. green; photosynthetic2. functional stomata3. still embedded in gametophyte, gets some nutrition from itD. about 100 living species VII. Phylum Bryophyta - mossesA.