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Plant Diversity Chapter 22
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What is a Plant? Does it have leaves? Does the leaf have veins?
Where is the plant growing? What is the approximate size of the plant? Is the plant moss-like, or does it have a green or woody stem?
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22 – 1 Introduction to Plants
Characteristics Multicellular Eukaryotic Cell wall made of cellulose Develop from embryos Carry out photosynthesis using chlorophyll a and b
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What plants need to survive
Plant life cycle Two alternating phases Diploid phase Fertilization Sporophyte plant (2N) Meiosis produces spores (N) Haploid phase Gametophyte plant (N) Produce egg (N) and sperm (N) What plants need to survive Sunlight Water and minerals Gas exchange Movement of water and nutrients
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Early Plants Origins in the water The first plants
Evolved from organisms like multicellular green algae The first plants 450 million years ago (mya) first fossil Similar to today’s mosses Grew in damp conditions Adaptations led to life cycles on dry land
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Overview of the plant kingdom
Grouping based on Water conducting tissue Seeds Flowers Mosses and their relatives 15,600 species Ferns and their relatives 11,000 species Cone bearing plants 760 species Flowering plants 235,000 species
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22 – 2 Bryophytes Nonvascular plants – no water conducting tissues
Can only draw up a few cm of water by osmosis Relatively small size Reproduction requires water Sperm cells swim through water to fertilize eggs
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Liverworts Hornworts Flat “liver” shaped leaves attached to the ground
Rhizoids Root – like structures attaching leaf to ground Gametophyte Broad “leaf” Male and female “umbrella” structures grow from “leaf” Live in water/moist conditions full time Sporophyte Grow under the female reproductive structures Gemmae Asexual reproductive structures Hornworts Gametophytes similar to liverworts Sporophytes Tiny green horn structures
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Mosses Can tolerate Rhizoids Gametophyte Sporophyte
Temporary dry conditions Nutrient poor soils Low temperatures Rhizoids “Root like” Absorb water and minerals Anchor plant to ground Gametophyte “stem” and “leaf” like structures Sporophyte Stalk Capsule Produces spores
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Life cycle of bryophytes
Stages Spore lands in moist environment Forms protonema Mass of green filaments Rhizoids form Gametophyte shoots grow Antheridia (male gametophyte) Archegonia (female gametophyte) Fertilization occurs Sporophyte grows out of archegonia
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22 – 3 Seedless Vascular Plants
Tracheids Water conductive cells 420 mya Xylem Conduct water upward Hollow tracheid cell resists pressure More effective than diffusion Phloem Secondary transport system Transports nutrient solutions
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Anatomy of seedless vascular plants
Roots absorb water and minerals from ground Anchor plant to ground Leaves Photosynthetic organs Conductive tissue is gathered into veins Stems Support structures Connect leaves and roots Transport liquids between leaves and roots
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Club mosses Horsetails Ancient species Modern species
Grew up to 35 m Formed large forests Fossilized remains are large coal beds Modern species Small plants Moist woodland habitat Resemble miniature pine trees Horsetails Photosynthetic leaves Non-photosynthetic leaves Arranged in joints along the stem Scale-like leaves Used to scour pots and pans
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Ferns Life cycle of ferns 350 mya True vascular tissue Strong roots
Rhizomes Fronds (large leaf structure) Life cycle of ferns Diploid sporophyte (dominant stage) Sori Sporangia – clusters of spores Gametophyte Grow rhizoids Grows tiny heart shaped structure Antheridium (male) Archegonium (female) Fertilization
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22 – 4 Seed Plants Reproduction free from water
Fertilization doesn’t require water Adaptations Flowers or cones Pollination Protection of embryos in seeds Pollen grain Male gametophyte Produces sperm
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Gymnosperms Seed Seeds are exposed Gnetophytes Cycades Plant embryo
Seed coat Protective casing Provides food Increases survival Gymnosperms Seeds are exposed Gnetophytes Reproductive scales clustered into cones Cycades Palm like plants Large reproductive cones
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Ginkgoes Conifers Common during dinosaur times
Only one species remains Ginkgo biloba Resistant to harsh conditions and air pollution Conifers Pines paired long needles Spruce short sharp Firs flat friendly Cedars, sequoias, redwoods, junipers, yews Can live more than 4000 years Can grow more than 100 meters high
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Gymnosperm life cycle Pollen lands near ovule
Pollen tube grows and releases 2 sperm Fertilization Zygote formation Embryo development Seed Contains embryo Surrounded by female gametophyte Seed coat is old sporophyte Germination Sporophyte Seed cone Ovule Meiosis Female gametophyte Pollen cone Pollen (male gametophyte)
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Angiosperms Seeds are covered by flowers Fruit Monocots
Contain ovaries Protect seeds Fruit Develops after fertilization Protects seed Aids in seed dispersal Monocots One cotyledon (seed leaf) Parallel veins Floral parts multiples of three Scattered vascular bundles Fibrous roots
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Dicots Woody Herbaceous Two cotyledons Branched veins on leaves
Floral parts multiples of 4 or 5 Vascular bundles arranged in ring Taproot Woody Stems with thick cell walls Trees, shrubs, and vines Herbaceous Stems are smooth and non-woody
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Annuals Biennials Perennials Life cycle in a single year
Snapdragons, petunias Biennials 2 year life cycle 1st year roots and stems grow 2nd year flower and reproduce Foxglove, strawberries Perennials Life cycle is more than two years Flowers and reproduces year after year Day-lilies, mums, irises
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Angiosperm life cycle Pollination Fertilization Zygote
Pollen lands on stigma Pollen travels through pollen tubes Fertilization Zygote Seed development Sporophyte Anther Produce male gametophyte (pollen) Ovary Produce female gametophyte (embryo sac) Egg cell (becomes embryo) Polar nuclei (becomes endosperm)
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