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Plant Diversity I How Plants Colonized Land (The Seedless Plants)

Plant Diversity I How Plants Colonized Land (The Seedless Plants). Packet #33 Chapter #29. Introduction. There are more than 290,000 species of plants that inhabit the earth. How, and why, based on the theory of evolution, did plants venture out of the sea and onto dry land? Charophyceans

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Plant Diversity I How Plants Colonized Land (The Seedless Plants)

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  1. Plant Diversity IHow Plants Colonized Land(The Seedless Plants) Packet #33 Chapter #29

  2. Introduction • There are more than 290,000 species of plants that inhabit the earth. • How, and why, based on the theory of evolution, did plants venture out of the sea and onto dry land? • Charophyceans • Green algae • Provides some of those answers

  3. Information About Plants • Multicellular • Eukaryotic • Photoautotrophs • Cell walls made of cellulose • Chlorophylls a & b are present in land plants

  4. Diversion of Algae and Land Plants • Embryophytes (plants with embryos) is the traditional scheme and equates with Kingdom Plante

  5. Similarities Between Charophyceans & Land Plants Evidence That Plants Moved to Land

  6. Morphological & Biochemical Evidence • It is thought that land plants evolved from green algae • Four Key Traits that “suggest” an evolutionary relationship between Charophyceans and Land Plants • Homologous peroxisomes • Both groups contain enzymes that minimize the loss of organic products due to photorespiration • Formation of phragomoplast • Synthesis of cell plates during cell division involves the formation of phragomoplast • Homologous Sperm • Many plants (gymnosperms) have flagellated sperm that match charophycean sperm • Homologous cellulose cell walls • Cell walls of both land plants and charophyceans contain 20-26% cellulose

  7. Genetic Evidence • Key nuclear genes • Ribosomal RNA • Cytoskeleton proteins • In agreement with the biochemical and morphological data • Homologous chloroplasts • Algal plastids, of green algae and algal groups such as euglenoids, are similar to those found in land plants • Chloroplast DNA found in charophyceans, green algae, is most closely related to that found in land plants.

  8. Adaptations Enabling the Move to Land • Charophyceans have a layer of a durable polymer called sporopollenin. • Prevents exposed zygotes from drying out. • May be the precursor to the tough sporopollenin walls that encase plant spores.

  9. “Evolutionary” Adaptations to Terrestrial Living/Derived Traits for Terrestrial Living

  10. Evolutionary Adaptations to Terrestrial Living • There are four main groups of land plants • Bryophytes • Pteridophytes • Gymnosperms • Angiosperms

  11. Adaptations II • The colonization of land by plants required the evolution of many anatomical, physiological and reproductive adaptations

  12. Adaptations III • Waxy Cuticle • Used to protect against water loss • Stomata • Gas exchange needed for photosynthesis

  13. Adaptations IV • Plant Life Cycles • Alternation of Generation • Part of the life cycle is in a haploid gametophyte generation and part in a diploid sporophyte generation. • The gametophyte plant produces gametes via mitosis • During fertilization the gametes fuse together to form the zygote • The zygote is the first stage of the sporophyte generation.

  14. Adaptations IV • Zygote develops into a multicellular embryo that the gametophyte protects and nourishes • Mature sporophyte plant develops from the embryo • Sporogenous cells (spore mother cells) are produced • Cells undergo meiosis to form spores • The spore is the first stage of the gametophyte generation.

  15. Adaptations V • Most plants produce multicellulargametangia • Protective jacket of sterile cells surrounding gametes. • Gametophyte generation (More to come later) all produce their gametes within multicellular structures • Gametangia • Male Gametangium • Antheridium • Many sperm released into the environment when mature

  16. Adaptations V • Female Gametangium • Archegonium • Produces a single egg cell and retains the egg within the organism

  17. Adaptations VI • Production of Secondary Compounds • Plants produce many unique compounds as byproducts of primary metabolic pathways. • Byproducts help plant defend itself against herbivores • Compounds have bitter tastes, strong odors or toxic effects. • Compounds include terpenes, alkaloids and tannins.

  18. Adaptations VII • Mosses and ferns, although adapted to life on land, have motile sperm cells that require water as a transport medium for fertilization. • Ferns, and vascular plants, that “evolved” at a later time, have xylem, to conduct water, and phloem, to conduct dissolved sugar.

  19. Features That Distinguish Bryophytes From Green Algae and Other Plants The Bryophytes

  20. Bryophytes • Have several adaptations that green algae lack • Cuticle • Stomata • Multi cellular gametangia

  21. Bryophytes II • Non-vascular plants • Lack xylem • Lack pholem • Only plants with a dominant gametophyte generation. • Sporophytes remain permanently attached and nutritionally dependent on the gametophyte.

  22. Phyla of Pryophytes Bryophytes

  23. Bryophyte Diversity

  24. Phylum BryophytaThe Mosses • Have gametophytes that are green plants that grow from a filamentous protonema. • Green filamentous growth that arises from spore germination in liverworts and mosses and eventually gives rise to a mature gametophyte.

  25. Phylum BryophytaThe Mosses • Gametophyte bears archegonia and/or antheridia at the top of the plant. • During fertilization, sperm cell fuses with an egg cell in the archegonium • Zygote grows into an embryo that develops into a moss sporophyte which is attached to the gametophyte. • Meiosis occurs within the capsule if the sporophyte to produce spores. • Spores are dispersed by wind. • Spore germinates. Grows into a protonema that forms a bud.

  26. Gametophyte Sporangium Life Cycle of the Mosses

  27. Sporangium Mature Sporangium Life Cycle of the Mosses

  28. Germination Gametophyte Life Cycle of the Mosses

  29. Phylum BryophytaThe Mosses • Bryophytes have been distributed around the world from the tropics to the arctic. • They can exist in dry or cold habitats • They can practically desiccate • Rehydrates following rain events. • One wetland moss, Sphagnum, forms extensive deposits of peat.

  30. Phylum HepaticophytaThe Liverworts • Have gametophytes that are flattened, lobelikethalli. • Plant body, not differentiated into roots, stems and leaves, of some algae, fungi and similar simple plantlike organisms. • Others are leafy

  31. Phylum AnthocerotophytaHornworts • Have thalloid gametophytes

  32. Features That Distinguish Ferns and Other Seedless Vascular Plants From Algae and Bryophytes. Ferns

  33. Ferns I • Comparison to Bryophytes • Ferns have vascular tissue • Ferns have a dominant sporophyte generation. • As in bryophytes, reproduction in ferns depends on water as a transport medium for their motile sperm cells.

  34. Seedless Vascular Plants

  35. Introduction I • Represent the modern groups that formed the forest during the evolutionary time period—The Carboniferous Period. • Organisms left relics, fossils and coals • Seed plants were present during this evolutionary time period but were not dominant. • Became important as the swamps dried up and the global climate cooled.

  36. Introduction II • There are four phyla of seedless vascular plants. • Phylum Polypodiophyta • Ferns • Phylum Psilotophyta • Whisk ferns • Phylum Equisetophyta • Horsetail • Phylum Lycophyta • Club Mosses

  37. Phylum PterophytaSubphylum PolypoiophytaThe Ferns • Largest and most diverse group of seedless vascular plants. • More than 12,000 species have been described. • Almost all species are homosporous (details to come) • All have megaphylls.

  38. Phylum PterophytaSubphylum PolypoiophytaThe Ferns • Sprophytes have roots, rhizomes and leaves that are megaphylls. • Leaves, or fronds, bear sporangia in clusters called sori. • Meiosis of sporangia produces haploid spores. • Fern gametophyte, called a prothallus, develops from a haploid spore and bears both archegonia and antheridia.

  39. Keywords • Homospory • The production of one kind of spore • Bryophytes • Whisk ferns • Horsetails • Most club mosses • Most ferns • Spore gives rise to gametophyte plants that produce both egg and sperm cells.

  40. Keywords II • Heterospory • Production of two kinds of spores • Microspores • Give rise to male gametophytes that produce sperm cells • Megaspores • Give rise to female gametophytes that produce eggs. • Occurs in • Certain club mosses • Certain ferns • ALL SEED PLANTS. • The “evolution” of heterospory was an essential step in the evolution of seeds.

  41. Phylum PterophytaSubphylum PsilotophytaThe Whisk Ferns • Lack true roots and leaves • Consists of dichotomously branching rhizomes • Have erect stems. • Homosporous sporophylls.

  42. Phylum PterophytaSubphylum EquisetophytaThe Horsetails • Sporophytes have roots • Rhizomes • Aerial stems • Hollow and jointed • Leaves that are reduced megaphylls

  43. Phylum LycophytaThe Club Mosses • Consist of roots • Rhizomes • Erect branches • Leaves that are microphylls.

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