Plant Diversity. Definition of Plants. Plant Evolution 4 Main Groups of Land Plants

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1 Definition of Plants Plant Diversity Chapters 29 & 30 Multicellular Eukaryotic Photosynthetic Autotrophic Cell walls made of cellulose Chlorophylls a and b Plant Evolution 4 Main Groups of Land Plants Bryophytes non vascular plants Mosses, liverworts, hornworts Pteridophytes - seedless vascular plants Lycophytes, ferns, horsetails, whisk ferns Gymnosperms naked seed plants Ginko, cycads, gnete, conifers Angiosperms flowering plants

2 Land Plant Evolution Ancestral green algae Aquatic plants: Charophyceans Land plants: Development of vascular tissue Development of seeds Development of flowering plants Closest relative of land plants Algal group Charophyceans Similarities with land plants Rosette cellulosesynthesizing complexes Located in plasma membranes Peroxisomes Flagellated sperm (some land plants) Evidence of common ancestor with charophycean algae Homologous chloroplast Homologous cellulose walls Homologous peroxisomes Homologous sperm Molecular systematics Chloroplast DNA Ribosomal RNA Adaptations of Land Plants Apical meristems Roots and shoots growth Multicellular, dependent embryos embryophytes Transfer of nutrients from parent Alternation of generations Sporophyte (diploid) and gametophyte (haploid) Gametangia gametes are produced within multicellular organ Female archegonia Male - Antheridia Walled spores resist drying out Cuticle waxy covering, water conservation Stomata pores, water conservation Vascular tissue transport water and minerals

3 Apical meristems of plant shoots and roots Embryos of land plants Alternation of generations Gametangia: Gametes produced within multicellular gametangia Archegonium - female Antheridium - male egg sperm

4 Vascular Tissue: Xylem and Phloem Xylem (water) Development of Alternation of Generations Delay in meiosis until one or more mitotic divisions of the zygote occurred Result: multicellular, diploid sporophyte Increases number of spores produced per zygote Phloem (food) Bryophytes Bryophytes 3 phyla Hepatophyta: liverworts Anthocerophyta: hornworts Bryophyta: mosses Non-vascular Earliest land plants Gametophyte (haploid) is dominant form Anchored by rhizoids No true roots or leaves

5 Life cycle of a moss Moss life cycle gametophyte gametangia sporophyte sporophyte spores Protonemata (pre-gametophyte) Vascular Plants Vascular plants have Xylem transports water Phloem transports food Dominant sporophyte generation First vascular plants were seedless 3 Groups Seedless plants Gymnosperms Angiosperms Seedless Vascular Plants 2 phyla Lycophyta lycophytes Pterophyta ferns, whisk ferns, horsetails Most have true roots and leaves Still require water for fertilization

6 Hypothesis for the development of leaves Probably evolved from a flap of stem tissue Stem had vascular tissue Microphylls Macrophylls larger leaves with branched veins Life cycle of a fern Fern sporophyll, a leaf specialized for spore production & sori Fern gametophyte

7 Archegonia of fern Evolution of Seed Plants Flagellated sperm from antheridium fertilize eggs in archegonium zygote Reduction of gametophyte continued Seeds important means of dispersal Pollen eliminated water requirement for fertilization Pollination Two clades Gymnosperms Angiosperms Gametophyte/ Sporophyte Relationships Seed plants: further reduced gametophyte Female gametophyte and embryo protected by parental sporophyte Seed Development Fertilization initiates the transformation from ovule to seed

8 What is a seed? Seed Dispersal Sporophyte embryo Food supply Protective coat May remain dormant for years May be carried by wind, water or animals Seeds have adaptations for dispersal Wind Water Animal Gymnosperms Phylum Coniferophyta: Frasier Fir 4 phyla Ginko Cycads Gnetophytes Conifers Naked seed no fruit (ovary) Seeds develop on surface of sporophylls Evolved before angiosperms

9 Characteristics of Conifers Life cycle of a pine Cone: reproductive structure Cluster of sporophylls Female cones: produce ovules - pine cones Male cones: produce pollen Seed develops from fertilized ovule scale of cone Dominate in areas with short growing season High latitude or altitude Most are evergreens Some have needle-shaped leaves Adapted for dry conditions Thick cuticle Pine embryo Embryo (new sporophyte) Angiosperms: Flowering Plants Major Clades:

10 Phylum Anthophyta: Angiosperms Vascular seed plants Reproductive structures: flowers, fruits Most diverse group of plants today 2 groups # Petals # Cotyledons Vascular bundles Root Monocots Dicots Xylem cells in Angiosperms Trachids Support Water transport Fiber ** Support Vessel element ** More efficient ** Evolutionary adaptations of angiosperms Flower Structure: Reproductive Adaptation of Angiosperms Life cycle of an angiosperm

11 Fruit and Seed Dispersal Flower-pollinator relationships