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Transcript
Plant Diversity Overview: The Greening of Earth • Imagine all land without life. Completely barren. Overview: The Greening of Earth • Land surface WAS lifeless for >3 billion years! • Now there’re about 290,000 plant species on land. Seriously. Wow. • Plants supply oxygen and are the ultimate source of most food eaten by land animals Land plants evolved from green algae • Green algae called charophytes are the closest relatives of land plants Green Algae Mosses Ferns Conifers (Gymnosperms) Flowering Plants (Angiosperms) *Some biologists think the plant kingdom should be expanded to include some or all green algae! What do plants need to survive? Water Carbon Dioxide Sunlight Nutrients. . . Not much! The Move to Land. . . • Benefits of moving to land: • • • • • unfiltered sun more CO2 nutrient-rich soil (yes!) few herbivores or pathogens Challenges: • • scarcity of water lack of structural support Plant Traits Enabling the Move to Land • • • Roots – suck up water and minerals in soil, anchor Leaves – produce energy/sugar through photosynthesis Vascular tissue • Xylem – pumps water & minerals from roots to rest of plant • • Phloem – pumps sugar/food/energy from leaves to rest of plant Cuticle • • Water and gas-tight; reduces water loss Stomata – pores in leaf cuticle; open to allow gas flow and close to reduces water loss Fig. 29-UN7 Green Algae vs. Plants: SIMILARITIES Traits of Green Algae Traits of Plants Eukaryotic – have a nucleus Eukaryotic – have a nucleus Multicellular – more than one cell Multicellular – more than one cell sexual and asexual reproduction sexual and asexual reproduction Photosynthetic – autotrophs that use chlorophyll Photosynthetic – autotrophs that use chlorophyll Extra energy stored as starches Extra energy stored as starches Cells have cell walls made of cellulose Cells have cell walls made of cellulose Green Algae vs. Plants: DIFFERENCES • Universal plant traits: – – – – – 1) Alternation of generations 2) Sporangia - make walled spores 3) Gametangia (multicelled) 4) Apical meristems Common plant traits: – – – Roots Vascular tissue Seeds -Leaves/Fronds -Cuticles -Flowers -Stems -Stomata. . . Universal Plant Trait #1: Alternation of Generations • Reproductive cycle: alternation of generations. • Sporophytes (2n) produce spores (n). Spores grow into gametophytes (n). Gametophytes make gametes (n), which fuse to become a fertilized zygote (2n). Zygotes grow into sporophytes. • • • Fig. 29-5a Gametophyte (n) Mitosis n n Spore MEIOSIS Gamete from another plant Mitosis n n Gamete FERTILIZATION 2n Mitosis Sporophyte (2n) Zygote Universal Plant Traits #2 and #3: 2) Sporophytes use sporangia to make spores. 3) Gametophytes use gametangia to make gametes. • • archegonia are female gametangia • Remember: archeEGGonia produce EGGS! antheridia are male gametangia • site of sperm production and release Fig. 29-5c Spores Sporangium Sphagnum sporangium (LM) Sporophyte Gametophyte Universal Plant Trait #4: Apical Meristems • at tips of roots and stems • Cells from apical meristems can become almost ANY type of plant tissue! (exciting) Fig. 29-5e Apical meristem of shoot Shoot Developing leaves 100 µm Apical meristems Apical meristem of root Root 100 µm Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms (conifers) Angiosperms (flowering) • • Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms (conifers) Angiosperms (flowering) • • Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms (conifers) Angiosperms (flowering) • • } Vascular Plants Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) } Gymnosperms Angiosperms • • Seed Plants } Vascular Plants Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) } Gymnosperms Angiosperms • • Seed Plants } Vascular Plants Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Table 29-1 Table 29-1 Table 29-1 Table 29-1 Table 29-1 * * Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms (conifers) Angiosperms (flowering) • • Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Nonvascular plants (Mosses and worts!) • • • • • Past: many GIANT mosses Now: small herbaceous plants No vascular system Absorb water all over Dominant gametophyte, small dependent sporophyte Fig. 29-9b Nonvascular plants Plagiochila deltoidea, a “leafy” liverwort Fig. 29-9c An Anthoceros hornwort species Sporophyte Gametophyte Fig. 29-9d Polytrichum commune, hairy-cap moss Sporophyte Gametophyte Fig. 29-5c Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Sporophyte Gametophyte Sporophytes and sporangia of Sphagnum (a moss) Nonvascular plants (mosses) Fig. 29-8-3 “Bud” Key Haploid (n) Diploid (2n) Protonemata (n) Raindrop Sperm Antheridia Male gametophyte (n) •Sperm swim through a film of water to reach and fertilize the egg! “Bud” Egg Spores Gametophore Female Archegonia gametophyte (n) Spore dispersal Rhizoid Peristome FERTILIZATION Sporangium MEIOSIS Mature sporophytes Seta Capsule (sporangium) Foot (within archegonium) Zygote (2n) Embryo 2 mm Archegonium Capsule with peristome (SEM) Young sporophyte (2n) Female gametophytes From nonvascular to vascular. . . • NONVASCULAR PLANTS owned Earth for 100 million years! • BUT they needed moist environments: • • • No vascular system to take water up from soil! Sperm have to SWIM to egg So later, VASCULAR PLANTS took over! • Vascular tissue pumped water up from soil AND allowed them to grow TALL! We just did: Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms Angiosperms • • Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Moving on to: Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms Angiosperms • • } Vascular Plants Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants Traits of Vascular Plants • Dominant sporophyte generation Vascular tissues True roots and leaves Can grow TALL! • So. . .they can live farther from water! • • • Dominant Gametophyte or Sporophyte? • In non-vascular plants, the gametophyte dominates • In vascular plants, the sporophyte dominates Sporophyte Sporophyte Gametophyte Gametophyte Ferns (seedless vasc. plants) • • vascular tissue spores, not seeds • • • • spores are sexual and haploid: not yet fertilized! Dominant sporophyte or gametophyte? Diverse - more than 12,000 species of ferns! Mostly tropical, some temperate Fig. 29-15a Ferns (seedless vasc. plants) Fig. 29-15b Ferns (seedless vasc. plants) Selaginella apoda, a spike “moss” Fig. 29-15c Seedless vascular plants Isoetes gunnii, a quillwort Fig. 29-15d Seedless vascular plants a club “moss” Fig. 29-15f Ferns (seedless vasc. plants) 25 cm Athyrium filix-femina, lady fern Fig. 29-13-1 FERN Alternation of Generations Key Haploid (n) Diploid (2n) MEIOSIS Spore dispersal Sporangium Sporangium Sorus Fiddlehead Mature sporophyte (2n) Fig. 29-13-2 FERN Alternation of Generations Key Haploid (n) Diploid (2n) MEIOSIS Spore dispersal Spore (n) Sporangium Sporangium Sorus Fiddlehead Antheridium Young gametophyte Mature gametophyte (n) Archegonium Egg Mature sporophyte (2n) FERTILIZATION Sperm Fig. 29-13-3 FERN Alternation of Generations Key Haploid (n) Diploid (2n) MEIOSIS Spore dispersal Spore (n) Sporangium Sporangium Antheridium Young gametophyte Mature gametophyte (n) Archegonium Egg Mature sporophyte (2n) New sporophyte Zygote (2n) Sorus Gametophyte Fiddlehead FERTILIZATION Sperm Fig. 29-13-3 Key Haploid (n) Diploid (2n) Where’s the dominant sporophyte? MEIOSIS Spore dispersal Spore (n) Antheridium Young gametophyte Sporangium Sporangium Fern Mature gametophyte (n) Archegonium Egg Mature sporophyte (2n) New sporophyte Zygote (2n) Sorus Gametophyte Fiddlehead FERTILIZATION Sperm Fig. 29-13-3 Key Haploid (n) Diploid (2n) MEIOSIS Spore dispersal Spore (n) Sporangium Sporangium Antheridium Young gametophyte Mature gametophyte (n) Archegonium Egg Mature sporophyte (2n) New sporophyte Zygote (2n) Sperm FERTILIZATION Sorus Gametophyte Fiddlehead DOMINANT sporophyte Review: Dominant Gametophyte or Sporophyte? • In non-vascular plants, the gametophyte dominates • In vascular plants, the sporophyte dominates Sporophyte Sporophyte Gametophyte Gametophyte You should now be able to: Tell whether the gametophyte generation or the sporophyte generation is dominant in each of the following major groups of plants: 1. 2. 3. In non-vascular plants? In seedless vascular plants? In seed plants? Classifying Land Plants Nonvascular plants (mosses) Seedless vascular plants (ferns) Gymnosperms Angiosperms • • } Seed Plants } Vascular Plants Most plants have vascular tissue; they’re vascular plants Mosses have no vascular tissue; they’re nonvascular plants And finally, seed plants! • A seed is an embryo and nutrients surrounded by a protective coat • Seed plants form a clade and can be divided into further clades: – – Gymnosperms, the “naked seed” plants, including the conifers Angiosperms, the flowering plants Parts of a Seed Cotyledon – “seed leaf” Purpose: reproduction - protects embryo, provides nutrients, may aid in dispersal Gymnosperms (mostly conifers) Basics: have vascular tissue, seeds, dominant sporophytes Gymnosperm - means “naked seed” Conifer - cone-bearing trees: pine, fir, spruce Cone - scaly structure produced by some seed plants; support either male or female reproductive structures; site of seedproduction Table 29-1 ! ! Angiosperms (flowering plants) WAY most common Produce flowers Seeds are enclosed in fruits Either monocots or dicots (1 seed leaf or 2) May be annuals, biennials, or perennials Annuals – only live one year, seeds survive winter Biennials – complex 2-year life cycle Perennials – “hibernate” through winter, come back year after year Parts of a Flower? Parts of a flower! -Pistil New terms (will be on next vocabulary sheet) Gymnosperm Conifer Cone Angiosperm Flower Cotyledon Monocot Dicot Annual Biennial Perennial Petal Sepal Stamen Pistil
