BIOL 112 1st Edition Lecture 14 Outline of Last Lecture I Phylogenetic Trees II Early Animal Evolution III Vendian Animal Fossils IV The Cambrian Explosion V What happened VI Hox Gene Clusters VII Patterning Genes VIII Phylum Chordata IX Disagreement of Schemes Outline of Current Lecture X The Crown Group XI Kingdom Plantae XII Plant Evolution XIII Cryptogams XIV Phylum Bryophyta XV Advances of Bryophytes from Algae XVI Tracheophytes XVII Phylum Pterophyta XVIII Advances of Ferns over Mosses XIX Seed Plants XX Gymnosperms These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute XXI Phylum Coniferophyta XXII Male Cone and Pollen XXIII Female Cone and Eggs XXIV Seed XXV Advances of Conifers over Ferns XXVI Angiosperms XXVII Phylum Anthophyta XXVIII Flower Anatomy XXIX The Ovule Current Lecture I The Crown Group Three multicellular kingdoms K Plantae K Fungi K Animalia All true multicellular organisms differentiated cells with multi tissue body plan All make use of eukaryotic alternation of generations sexual cycle II Kingdom Plantae Multicellular mostly macroscopic mostly autotrophic Cell walls made up of cellulose Multiple tissue cell types organized into stereotyped structures stems leaves roots Some members vascularized xylem and phloem Most species terrestrial or secondarily aquatic marine habitats At least 500 000 species III Plant Evolution Appear to have descended from green algae approx 475 million years ago Candidate ancestors are charophyceans advanced green algae DNA cell structure biochemistry and chlorophyll similarities to plants Plant kingdom especially interactive Comparison of primitive to advanced groups shows clear sequence of evolutionary trends This sequence is associated with increasing ability of the plants to live on dry lang free from need for water film From primitive ancient to advanced derived plant taxa evolutionary trends Increasing complexity of organization of body Increasing importance of the diploid phase of the life cycle and decreasing importance to the haploid phase This includes the appearance of embryo sporophyte plants Increasing independence from the need for free water film for fertilization and general life cycle We emphasize the progressive differences Comparisons and differences to discern to evolutionary trends from primitive to advanced phyla are as important as details of each representative life cycle IV Cryptogams Primitive phyla in K Plantae Do not produce seeds mystery to early botanists how these reproduced We now know that these organisms release microscopic spores which germinate into gametophytes Informal category of cryptogams still applies to seedless plants bryophytes ferns etc V Phylum Bryophyta Primitive phylum Life in moist marine environments need water film Haploid gametophyte dominant life cycle both gametophyte and sporophyte phases are multicellular Poor multicellular organization no vascularization of tissues Males produce sperm in antheridia females produce eggs in archegonia Sperm are poor swimmers and depend upon water splash to get to vicinity of archegonia Sporophyte is non photosynthetic and depends upon gametophyte for nourishment and support VI Advances of Bryophytes from Algae Multicellular haploid and diploid stages true alteration of generations One fertilization event leads to production of many haploid spores many mitoses Problem for land existence Depends upon free water film for fertilization sperm must swim Depends upon random physical event water splash to facilitate fertilization Sporophyte is parasitic on gametophyte VII Tracheophytes Plants with pipes Vascular Plants Have specialized tissues for transport of fluids throughout plant body xylem and phloem True xylem and phloem include the unique complex polymer lignin Advantage for living in drier environments and also for supporting plant body farther from surface of earth Specialized tissues for collecting water and nutrients roots Specialized tissues for connecting roots and leaves stems Sporophyte is only life cycle phase that is vascularized gametophyte is never vascularized VIII Phylum Pterophyta Ferns seedless vascular plants Mature fern is sporophyte dominant phase of life cycle Vascularized with true leaves and roots On the underside of leaves you can find the sori collected sporangia In each sporangium meiosis produces haploid spores Spore germinates into gametophyte antheridia and archegonia develop on opposite sides of gametophyte thallus After fertilization sporophyte plant grows in place and eventually overgrows parent gametophyte IX Advances of Ferns over Mosses Greater use of sporophyte phase and reduction of gametophyte phase Both phases photosynthetic independent Sporophyte is vascularized and larger can live in dryer environments But fertilization still requires a water film for sperm and gametophyte still needs very moist environment X Seed Plants First forms possibly appeared near the end of the Devonian Period 360 MYA Not common until after Permian Period 250 MYA Two evolutionary lineages Gymnosperms naked seeds conifers Seeds produced on sporophylls specialized leaf derived structures in cones Angiosperms enclosed seeds flowering plants Seeds produced inside ovaries which eventually develop into fruits XI Gymnosperms Naked Seeds no fruit ovary around seed 4 phyla pines gingkos cyads gnetophytes Most common phylum is the conifers pines junipers redwoods cypress firs All phyla produce cones strobili highly modified leaves containing sporangia sporophylls XII Phylum Coniferophyta Sporophyte dominant life cycle Sporophyte is pine tree vascularized form Many live in cold northern climates Needles true vascularized leaves specialized to live in dry climates Evergreen each needle lives 2 7 years but eventually dies Sporangia collected into a cluster on cone strobilus Unlike ferns separate kinds of spores heterosporous Microspores made in male strobilus Megaspores made in female strobilus XIII Male Cone and Pollen Sporophyll modified leaf holds microsporangium Sporangium Sterile jacket surrounding sporogenous tissue Meiosis followed by sporulation making microspores but sporangium does not release spores germinate in place germination at least 1 mitosis In conifers 2 mitoses 4 nuclei in spore cytoplasm 1 dies differentiates into a pollen grain male gametophyte Pollen grain non photosynthetic packed for long shelf life released from