Chapter 23: Plant Evolution

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Chapter 23: Plant Evolution Invading the Land Cyanobacteria were probably the first to spread into and up freshwater streams Later, green algae and fungi made the journey together Every plant is descended
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Chapter 23: Plant Evolution Invading the Land Cyanobacteria were probably the first to spread into and up freshwater streams Later, green algae and fungi made the journey together Every plant is descended from species of green algae Setting the Stage for Plants Earth s atmosphere was originally oxygen free Ultraviolet radiation bombarded the surface Photosynthetic cells produced oxygen and allowed formation of a protective ozone layer The Plant Kingdom Nearly all are multicelled Vast majority are photoautotrophs Energy from sun Carbon dioxide from air Minerals dissolved in water Fig. 23-2, p.372 Charophytes Fig. 23-3, p.372 Nonvascular Plants Bryophytes Fewer than 19,000 species Three groups Liverworts Hornworts Mosses Vascular Plants Majority of plants Have internal tissues that carry water and solutes Two groups Seedless vascular plants Seed-bearing vascular plants Seedless Vascular Plants Arose during the Devonian Produce spores but no seeds Four main groups Whisk ferns Lycophytes Horsetails Ferns Seedless Vascular Plants Fig. 23-4a, p.372 Seedless Vascular Plants Fig. 23-4b, p.372 Seedless Vascular Plants Fig. 23-4c, p.373 Seed-Bearing Vascular Plants Gymnosperms arose first Cycads Ginkgos Gnetophytes Conifers Angiosperms arose later Monocots Dicots Seed- Bearing Vascular Plants Archaeanthus linnenbergeri Fig. 23-4d, p.373 Plant Evolution Gondwana 420 mya 360 mya Bryophytes (liverworts) appear by 475 mya. Origin of earliest seedless vascular plants, in Silurian. Bryophytes diversify. Lycophytes, horsetails, ferns undergo early adaptive radiations. By 360 mya, seed plants evolve. Vast swamp forests; bryophytes, tree-size lycophytes, horsetails, ferns dominate. origin of conifers late in the Carboniferous. Ordovican Silurian Devonian Carboniferous Fig. 23-5a, p.373 Plant Evolution Pangea 240 mya 65 mya Origin of ginkgos, cycads. Conifers diversify. Extinction of most lucophytes and horsetails by end of Permian Ferns, cycads, conifers undergo adaptive radiations; by start of Cretaceous, conifers the dominant trees. Origin of flowering plants by the early Cretaceous. Rapid adaptive radiations and to dominance in nearly all habitats on land. Permian Triassic Jurassic Cretaceous present Fig. 23-5b, p.373 Evolutionary Trend mitosis multicelled sporophyte (2n) zygote (2n) fertilization Diploid Haploid meiosis gametes (2n) mitosis multicelled gametophytes (n) mitosis spores (2n) Fig. 23-6a, p.374 zygote only, no sporophyte green algae bryophytes ferns gymnosperms angiosperms Fig. 23-6b, p.374 Adaptations to Land Root systems Shoot systems Vascular tissues (xylem and phloem) Waxy cuticle Evolutionary Tree for Plants Nested monophyletic groups green algae zygophytes, related groups charophytes bryophytes lycophytes horsetails ferns cycads ginkgos conifers gnetophytes flowering plants seed plants euphyllophytes embryophytes (land plants) vascular plants (closely related groups) Fig. 23-7, p. 387 p.375 Bryophytes Small, nonvascular, nonwooody Gametophyte dominates life cycle; has leaflike, stemlike, and rootlike parts Usually live in wet habitats Flagellated sperm require water to reach eggs Types of Bryophytes Mosses (most common) Liverworts (simplest) Hornworts Moss Life Cycle zygote Fertilization Zygote grows, develops into a sporophyte while still attached to gametophyte. mature sporophyte Diploid Stage Haploid Stage Meiosis Spores germinate. spermproducing structure eggproducing structure male gametophyte female gametophyte Fig. 23-8a, p.376 Peat Mosses sporophyte gametophyte Fig. 23-9b, p.377 Marchantia: A Liverwort Reproduces asexually by gemmae Gametophytes are male or female Female gametophyte Marchantia: A Liverwort Fig a, p.377 Marchantia: A Liverwort Female gametophyte Male gametophyte Fig b, p.377 Seedless Vascular Plants Like bryophytes Live in wet, humid places Require water for fertilization Unlike bryophytes Sporophyte is free-living and has vascular tissues Seedless Vascular Plants Lycophytes (Lycophyta) Whisk ferns (Psilophyta) Horsetails (Sphenophyta) Ferns (Pterophyta) sporangium Seedless Vascular Plants Fig a, p.378 strobilus Seedless Vascular Plants Fig b, p.378 Seedless Vascular Plants Fig c, p.378 Seedless Vascular Plants Fig d, p.378 Ferns (Pterophyta) 12,000 species, mostly tropical Most common sporophyte structure Perennial underground stem (rhizome) Roots and fronds arise from rhizome Young fronds are coiled fiddleheads Mature fronds divided into leaflets Spores form on lower surface of some fronds Fern Life Cycle Sporophyte still attached to gametophyte zygote fertilization egg rhizome Diploid Stage meiosis Haploid Stage Spores develop sorus Spores are released sperm Fig p. 391 mature gametophyte Spore germinates p.379 Carboniferous Giant lycophytes and horsetails Sea level rose and fell repeatedly Remains of swamp forests were repeatedly submerged and compressed Formation of coal Carboniferous Lepidodendron a tree-sized club moss Fig a, p.380 Carboniferous Fig b, p.380 Carboniferous stem of a giant lycophyte (Lepidodendron) seed fern (Medullosa), one of the early seedbearing plants stem of giant horsetail (Calamites) Fig c, p.380 Rise of Seed-Bearing Plants Seeds appeared about 360 million years ago Seed ferns and gymnosperms were dominant at first Angiosperms arose later Seed-Bearing Plants Microspores that give rise to pollen grains Megaspores inside ovules More water-conserving than seedless vascular plants Pollen Pollen grains are sperm-bearing male gametophytes that develop from microspores Allows transfer of sperm to egg without water Can drift on air currents or be carried by pollinators Pollen pine pollen grains p.381 Ovules Female reproductive structures that become seeds Consist of: Female gametophyte with egg cell Nutrient-rich tissue Jacket of cell layers that will form seed coat Ovules Fig a, p.381 Gymnosperms Plants with naked seeds Seeds don t form inside an ovary Four groups Conifers Cycads Ginkgos Gnetophytes Conifer Characteristics Widest known, largest number of living species Woody trees or shrubs Most are evergreen Most produce woody cones Conifer Characteristics Fig a, p.382 Conifer Characteristics Fig b, p.382 Conifer Characteristics Fig c, p.382 Conifer Characteristics Fig d, p.382 Conifer Characteristics Fig e, p.382 Conifer Characteristics Fig f, p.382 Conifer Characteristics Fig g, p.382 Conifer Characteristics Fig h, p.382 Cycads Most diverse during age of dinosaurs Only 100 living species Palmlike appearance Pollen-bearing and seedbearing cones on different plants Strobilus of a female cycad section through one ovule (the red cut in the diagram to the left): mature sporophyte seed coat embryo surface view of a female cone scale (houses two ovules) surface view of a scale of a male strobilus (houses two pollen sacs) ovule section through a pollen sac (red cut) seedling nutritive tissue seed formation zygote fertilization Diploid Stage Haploid Stage meiosis meiosis spermproducing cell pollen tube (view inside an ovule) eggs pollination (wind deposits pollen grain near ovule) Microspores Megaspores form, develop form; one into pollen grains. develops into the female gametophyte. Germinating pollen grain (the male gametophyte). Sperm nuclei form as the pollen tube grows toward the egg. female gametophyte Fig , p.383 Ginkgos Diverse during age of dinosaurs One surviving species, Ginkgo biloba Deciduous trees are male or female 3 Genera of Gnetophytes Gnetum Welwitschia Ephedra Sporophyte of Ephedra surface view of one cone scale (houses a pollen-producing sac) section through one ovule Pine Life Cycle ovule surface view of one cone scale (houses two ovules) mature sporophyte seeding pollen tube sperm-producing cell seed coat embryo seed section through a pollenproducing sac fertilization eggs zygote Diploid Haploid pollination meiosis microspores form megaspores form female gametophyte Fig , p. 396 Conifer Distribution Reproduce more slowly than angiosperms; at competitive disadvantage in many habitats Still dominate in far north, at higher elevations, and in certain parts of southern hemisphere Angiosperms Flowering plants Dominant land plants (260,000 species) Ovules and (after fertilization) seeds are enclosed in an ovary Three main groups: magnoliids, monocots, and eudicots Angiosperms Fig a, p.384 250 Angiosperms angiosperms (flowering plants) 200 cycads ferns gymnosperms Number of genera ginkgo other genera Time (millions of years) Fig b, p.384 Angiosperm Evolutionary Tree Amborella water lilies star anise magnoliids monocots eudicots basal groups Fig , p. 385 petal stamen (microspores form here) sepal carpel (megaspores form here) ovule in an ovary Fig , p.384 Fig a, p.385 Fig b, p.385 Fig c, p.385 Fig d, p.385 Fig e, p.385 sporophyte Flowering Plant Life Cycle Diploid Double fertilization Haploid Meiosis Meiosis pollination microspores mitosis without cytoplasmic division two sperm enter ovule female gametophyte Fig , p. 399 People and Plants Plant domestication began about 11,000 years ago About 3,000 species have been used as food Now about 200 plants are major crops Nonfood Uses of Plants Lumber, paper, and fuel Furniture Rope Thatched roofing Natural insecticides Drugs Plants of Abuse Tobacco plants are Nicotiana sp. Cannabis sativa is source of marijuana Coca leaves are used to produce cocaine Toxic plant alkaloids, such as henbane and belladona, have been used as poisons and as medicine Deforestation Deforestation is the mass removal of all trees from large tracts for logging, agriculture, and grazing Greatest in Brazil, Indonesia, Colombia, and Mexico Sustainable development Deforestation Fig b, p.389
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