Plant Diversity PDF

Plant Diversity Ch. 26 Learning Goal & Outcomes Goal: Understand the origins and key evolutionary traits distinguishing the nonvascular plants (i.e., bryophytes), seedless vascular plants (e.g., ferns), and seed plants (e.g., gymnosperms and angiosperms). Outcomes:...

Plant Diversity Ch. 26 Learning Goal & Outcomes Goal: Understand the origins and key evolutionary traits distinguishing the nonvascular plants (i.e., bryophytes), seedless vascular plants (e.g., ferns), and seed plants (e.g., gymnosperms and angiosperms). Outcomes: Describe benefits/challenges for plants transitioning to life on land. Explain the major derived traits of land plants. Name the 3 types of bryophytes and describe their structures, their generalized life cycle, and their ecological and economic importance. Explain the distinguishing features of vascular plants. Name the 2 types of seedless vascular plants and describe their structures, generalized life cycle, and historical importance. Describe the key distinguishing features and structures of all seed plants. Explain the structural and life cycle differences between gymnosperms and angiosperms. Explain the key characteristics of monocots and dicots.  The Greening of Earth Cyanobacteria and protists likely existed on land 1.2 billion years ago. ~ 500 mya, small plants, fungi, and animals emerged on land. ~ 385 mya tall plants emerged. Land plants evolved from green algae Traits of land plants also found in algae: Multicellular Eukaryotic Photosynthetic autotroph Cell wall of cellulose Chloroplasts with chlorophyll a and b Green algae called charophytes are closest relatives of land plants (share a common ancestor) Adaptations Enabling the Move to Land Challenges: Water availability Lack of structural support Radiation Adaptations and advantages: Sporopollenin – zygotes and spores Sunlight More CO2 than water Nutrient-rich soil  1. Alternation of generations 2. Walled spores Derived produced in sporangia Traits of 3. Multicellular Plants: gametangia 4. Apical meristems 1. Alternation of Generations Reproductive cycle- alternate between two multicellular stages – gametophyte and sporophyte The gametophyte is haploid and produces haploid gametes by mitosis Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis The dominant generation is usually larger and lives longer Work with a partner to label the letters below Without looking at the last slide! 1. Ploidy of A- 2. B (process)- 3. C (process)- 4. D (structure)- 5. Ploidy of D- 6. E (structure)- 7. Ploidy of E- 8. F (process)- 2. Walled Spores Produced in Sporangia Sporophytes have multicellular organs called sporangia that produce spores Spore walls contain sporopollenin, which makes them resistant to harsh environments 3. Multicellular Gametangia Gametes are produced within organs called gametangia Archegonium and Antheridium 4. Apical Meristems Localized regions of cell division at tips of roots and shoots Can divide throughout plant’s life Enables root and shoot elongation Additional Derived Traits Cuticle- Waxy covering to prevent desiccation Stomata- Pores that allow CO2 and O2 exchange Mycorrhizae- symbiotic association with fungi Land Plant Classification Bryophytes Small, herbaceous (nonwoody) plants Liverworts, phylum Hepatophyta Mosses, phylum Bryophyta Hornworts, phylum Anthocerophyta Earliest lineages to diverge from common ancestor of land plants Gametophytes are larger and longer- living than sporophytes Sporophytes typically present only part of the time Seedless Vascular Plants Vascular tissue allowed these plants to grow tall Xylem- transports water & mineral nutrients Phloem- transports organic compounds (sugars & amino acids) Have flagellated sperm, restricted to moist environments Life cycle with dominant sporophytes Well-developed roots & leaves Roots absorb water & nutrients from soil Leaves- photosynthetic organ Role of Seedless Vascular Plants Seedless vascular plant ancestors grew to great heights during the Devonian and Carboniferous Formed the first forests Increased growth and photosynthesis removed CO2 from the atmosphere The decaying plants of these Carboniferous forests eventually became coal Horsetail Fern Land Plant Classification Seed Plants Seed plants originated about 360 mya A seed consists of …? Evolutionary advantages over spores? Seed plants also have: reduced gametophytes ovules pollen Ovules & Pollen Haploid megaspore develops into egg- producing female gametophyte inside ovule Ovule: megasporangium, megaspore, and protective integuments Haploid microspore develops into pollen grain, male gametophyte with protective wall What is pollination? Pollen is transferred by wind or on body of animals Long-distance transfer of sperm without water allowed seed plants to move to dry habitats Gymnosperms “Naked seed”- typically on cone Seeds are exposed on sporophylls (scales) that form cones Male cone Most are cone-bearing plants- conifers Female cone Four phla: Cycadophyta (cycads) Gingkophyto (Ginkgo biloba) Gnetophyta Coniferophyta (conifers) Angiosperms Seed plants that produce reproductive structures- flowers & fruit Flower- Specialized structure for sexual reproduction Fruit- Mature ovary; Protects seeds, dispersal, fleshy or dry Adapted for dispersal Angiosperm Flower Specialized shoot with leaves modified to form four types of floral organs: Sepals (sterile) enclose the unopened flower Petals (sterile) attract pollinators Stamens (fertile) produce pollen Filament & anther (with pollen) Carpels/pistil (fertile) produce ovules Ovary (with ovules), style, & stigma After fertilization, ovules develop into seeds and ovary wall thickens into a fruit Angiosperm Diversity Most widespread & diverse plants Over 290,000 species, ~90% of plant species Monocots- one cotyledon (seed leaf) Maize, rice, wheat, orchid, grasses, onions, etc. Dicots- two cotyledons Zucchini, squash, sunflower, rose, cacti, oaks, etc. Monocot & Dicot Characteristics