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Mader: Biology 8 th Ed. Evolution and Diversity of Plants Chapter 24
Mader: Biology 8 th Ed. Outline Evolutionary History Alternation of Generations Nonvascular Plants Vascular Plants – Seedless – Seed – Angiosperms Monocots and Eudicots Flowers
Mader: Biology 8 th Ed. Evolutionary History of Plants Plants are 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.
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Alternation of Generations All plants have a life cycle that includes an alternation of generations. – Two multicellular individuals alternate, each producing the other. Sporophyte represents diploid generation. Gametophyte represents haploid generation.
Mader: Biology 8 th Ed. Alternation of Generations
Mader: Biology 8 th Ed. Alternation of Generations
Mader: Biology 8 th Ed. Alternation of Generations Sporophyte (2n) is named for its production of spores by meiosis. – Spore is haploid reproductive cell. Gametophyte (n) is named for its production of gametes.
Mader: Biology 8 th Ed. Reduction in Size of Gametophyte
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Protection of Eggs and Embryos
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Leaves of Vascular Plants
Mader: Biology 8 th Ed. Nonvascular Plants 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 and flagellated sperm in antheridia. Sperm swim to egg in film of water.
Mader: Biology 8 th Ed. Nonvascular Plants Hornworts (phlym Anthocerophyta) have small sporophytes that carry on photosynthesis.
Mader: Biology 8 th Ed. Nonvascular Plants Liverworts (phylum Hepatophyta) have either flattened thallus or leafy appearance.
Mader: Biology 8 th Ed. Nonvascular Plants 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.
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Vascular Plants 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.
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Seed Plants 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.
Mader: Biology 8 th Ed. Gymnosperms Gymnosperms have ovules and seeds exposed on the surface of sporophylls. – Confiers – Cycads – Ginkgoes – Gnetophytes
Mader: Biology 8 th Ed. Conifers 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.
Mader: Biology 8 th Ed. Cycads Cycads (phylum Cycadophyta) have large, finely divided leaves that grow in clusters at the top of the stem. – Pollen and seed cones on separate plants. Pollinated by insects.
Mader: Biology 8 th Ed. Ginkgoes Ginkgoes (phylum Ginkgophyta) are dioecious, with some trees producing seeds and others producing pollen. – One surviving species. (Gingko biloba)
Mader: Biology 8 th Ed. Gnetophytes Gnetophytes (phylum Gnetophyta) have similarly structured xylem, while none have archegonia, but strobili have similar construction.
Mader: Biology 8 th Ed. Angiosperms Angiosperms (phylum Anthophyta) are 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 Paleogene periods.
Mader: Biology 8 th Ed. Monocots and Eudicots Two classes of flowering plants. – Monocotyledones (Monocots) One cotyledon in seed. – Eudicotyledones (Dicots) Two cotyledons in seed.
Mader: Biology 8 th Ed. The Flower Penducle (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).
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Flowering Plant Life Cycle
Mader: Biology 8 th Ed. 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.
Mader: Biology 8 th Ed. Review Evolutionary History Alternation of Generations Nonvascular Plants Vascular Plants – Seedless – Seed – Angiosperms Monocots and Eudicots Flowers