evolutionary history of plants - welcome | oriental …¥ angiosperms (phylum anthophyta) are an...

Mader: Biology 8th Ed.

Evolution and Diversity of Plants

Chapter 24

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Outline

• Evolutionary History • Alternation of Generations• Nonvascular Plants• Vascular Plants

– Seedless– Seed– Angiosperms

!Monocots and Eudicots!Flowers

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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.

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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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Four Major Plant Groups

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Fig. 24.2

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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.

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Fig. 24.3

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Fig. 24.4

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• 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.

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Reduction in Size of Gametophyte

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• 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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Protection of Eggs and Embryos

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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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Leaves of Vascular Plants

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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.

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Nonvascular Plants

• Hornworts (phlym Anthocerophyta) have small sporophytes that carry on photosynthesis.

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Nonvascular Plants

• Liverworts (phylum Hepatophyta) have either flattened thallus or leafy appearance.

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Fig. 24.8

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Fig. 24.8b

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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.

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Moss Life Cycle

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Fig. 24.9

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Fig. 24.9a

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Fig. 24.9b

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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.

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Fig. 24.10

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Vascular Tissue

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Fig. 24.11a

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Fig. 24.11b

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Fig. 24.11c

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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.

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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 Mosses

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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

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Ferns

• 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 Ferns and Ferns

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Fern Life Cycle

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Fern Life Cycle

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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.

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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

• 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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Conifers

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Fig. 24.18

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Pine Life Cycle

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Pine Life Cycle

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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.

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Ginkgoes

• Ginkgoes (phylum Ginkgophyta) are dioecious, with some trees producing seeds and others producing pollen.

– One surviving species. (Gingko biloba)

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Gnetophytes

• Gnetophytes (phylum Gnetophyta) have similarly structured xylem, while none have archegonia, but strobili have similar construction.

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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.

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Monocots and Eudicots

• Two classes of flowering plants.

– Monocotyledones (Monocots)

!One cotyledon in seed.

– Eudicotyledones (Dicots)

!Two cotyledons in seed.

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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).

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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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Flowering Plant Life Cycle

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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

• Alternation of Generations

• Nonvascular Plants

• Vascular Plants

– Seedless

– Seed

– Angiosperms

!Monocots and Eudicots

!Flowers

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evolutionary history of plants - welcome | oriental …¥ angiosperms (phylum anthophyta) are an...

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