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Biology, 9th ed, Sylvia Mader
Chapter 24 Chapter 24 Evolution and Diversity of Plants Evolution and Diversity of Plants
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Outline Evolutionary History Nonvascular Plants Vascular Plants
Alternation of Generations Nonvascular Plants Vascular Plants Seedless Seed Angiosperms Monocots and Eudicots Flowers
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Evolutionary History of Plants
More than 98% of all biomass is plants Multicellular photosynthetic eukaryotes 280,000 known species Thought to have evolved from freshwater algae over 500 mya Evolution of plants marked by four evolutionary events associated with four major groups of plants Nonvascular Plants Advent of nourishment of a multicellular embryo within the body of the female plant
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Representatives of the Four Major Groups of Plants
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Evolutionary History of Plants
Seedless vascular plants Advent of vascular tissue Gymnosperms and angiosperms Produce seeds Flowering Plants Attract pollinators that give rise to fruits
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Evolutionary History of Plants
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Alternation of Generations
Life cycle involves alternation of generations Multicellular 1n individuals (gametophytes) produce multicellular 2n individuals (sporophytes) Multicellular 2n individuals (sporophytes) produce multicellular 1n individuals (gametophytes) Sporophyte (2n): Multicellular individual that produces spores by meiosis Spore is haploid cell that will become the gametophyte Gametophyte (1n): Multicellular individual that produces gametes Gametes fuse in fertilization to form zygote Zygote is a diploid cell that will become the sporophyte
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Alternation of Generations
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Alternation of Generations
Appearance of generations varies widely In ferns, female portions are archegonia and are fertilized by flagellated sperm In angiosperm, female gametophyte (embryo sac), consists of an ovule Following fertilization, ovule becomes seed In seed plants, pollen grains are mature sperm- bearing male gametophytes
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Reduction in the Size of the Gametophyte
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Other Terrestrial Adaptations
Vascular tissue transports water and nutrients to the body of the plant Cuticle provides an effective barrier to water loss Stomata bordered by guard cells that regulate opening, and thus water loss
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Protection of Eggs and Embryos
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Leaves of Vascular Plants
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Nonvascular plants (bryophytes)
Lack specialized means of transporting water and organic nutrients Do not have true roots, stems, and leaves Gametophyte is dominant generation Produces eggs in archegonia Produces flagellated sperm in antheridia Sperm swim to egg in film of water to make zygote
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Nonvascular Plants Hornworts (phlym Anthocerophyta) have small sporophytes that carry on photosynthesis Liverworts (phylum Hepatophyta) have either flattened thallus or leafy appearance Mosses (phylum Bryophyta) usually have a leafy shoot, although some are secondarily flattened Can reproduce asexually by fragmentation Dependent sporophyte consists of foot, stalk, and sporangium
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Hornwort
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Liverwort, Marchantia
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Moss (Polytrichum) Life Cycle
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Xylem conducts water and dissolved minerals up from roots
Vascular Plants Xylem conducts water and dissolved minerals up from roots Phloem conducts sucrose and other organic compounds throughout the plant Lignin strengthens walls of conducting cells in xylem Most seedless vascular plants are homosporous Windblown spores are dispersal agents All seed plants are heterosporous and have male and female gametophytes Seeds disperse offspring
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Cooksonian Fossil
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Vascular Tissue
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Seedless Vascular Plants
Club Mosses (phylum Lycophyta) Typically, branching rhizome sends up short aerial stems Leaves are microphylls (have only one strand of vascular tissue) Sporangia occur on surfaces of sporophylls Grouped into club-shaped strobili
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Club Moss, Lycopodium
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Seedless Vascular Plants
Ferns and Allies Horsetails (phylum Sphenophyta) Rhizome produces tall aerial stems Contains whorls of slender, green branches Small, scalelike leaves also form whorls at the joints
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Horsetail, Equisetum
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Whisk Ferns (phylum Psilotophyta)
Branched rhizome has rhizoids Mutualistic mycorrhizal fungus helps gather nutrients Ferns (phylum Pterophyta) Large conspicuous fronds Divided into leaflets Dominant sporophyte produces windblown spores
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Whisk fern, Psilotum
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Diversity of ferns
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Fern Life Cycle
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Seed plants are the most plentiful plants in the biosphere
Seed coat and stored food allow an embryo to survive harsh conditions during long period of dormancy Heterosporous Drought-resistant pollen grains Ovule develops into seed
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Seed Plants
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Gymnosperms Gymnosperms have ovules and seeds exposed on the surface of sporophylls Confiers Cycads Ginkgoes Gnetophytes
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Conifers, as well as other gymnosperm phyla, bear cones
Tough, needlelike leaves of pines conserve water with a thick cuticle and recessed stomata Considered a “soft” wood because it consists primarily of xylem tissue
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Pine Life Cycle
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Cycads (phylum Cycadophyta)
Large, finely divided leaves that grow in clusters at the top of the stem Pollen and seed cones on separate plants Pollinated by insects
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Cycad Cones Figure 24.19
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Ginkgoes (phylum Ginkgophyta) Dioecious
Some trees producing seeds Others producing pollen One surviving species (Gingko biloba)
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The Ginkgo Tree
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Ephedra Figure 24.21
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Welwitschia miribilis
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Gnetophytes (phylum Gnetophyta)
Have similarly structured xylem None have archegonia Strobili have similar construction
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Angiosperms Angiosperms (phylum Anthophyta) An exceptionally large and successful group of plants Ovules are always enclosed within diploid tissues Became dominant group of plants in the late Cretaceous and early Paleocene periods
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Amborella trichopoda
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Two classes of flowering plants
Monocots and Eudicots Two classes of flowering plants Monocotyledones (Monocots) One cotyledon in seed Eudicotyledones (Dicots) Two cotyledons in seed
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Flower Diversity
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Peduncle (flower stalk) expands at tip into a receptacle
The Flower Peduncle (flower stalk) expands at tip into a receptacle Bears sepals, petals, stamens, and carpels, all attached to receptacle in whorls Calyx (collection of sepals) protect flower bud before it opens Corolla (collection of petals)
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Each stamen consists of an anther and a filament (stalk)
The Flower Each stamen consists of an anther and a filament (stalk) Carpel has three major regions Ovary - Swollen base Fruit Style - Elevates stigma Stigma - Sticky receptor of pollen grains
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Generalized Flower
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Flowering plant life cycle
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Flowers and Diversification
Wind-pollinated flowers are usually not showy Bird-pollinated flowers are often colorful Night-blooming flowers attract nocturnal mammals or insects Usually white or cream-colored Fruits of flowers protect and aid in dispersal Utilize wind, gravity, water, and animals for dispersal
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Review Evolutionary History Nonvascular Plants Vascular Plants
Alternation of Generations Nonvascular Plants Vascular Plants Seedless Seed Angiosperms Monocots and Eudicots Flowers
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Biology, 9th ed, Sylvia Mader
Chapter 24 Ending Slide Chapter 24 Evolution and Diversity of Plants Evolution and Diversity of Plants
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