Mader: Biology 8 th Ed. Evolution and Diversity of Plants.

Mader: Biology 8th Ed.

Evolution and Diversity of Plants


Outline

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

– Seedless– Seed– Angiosperms

Monocots and DicotsFlowers


Evolutionary History of Plants

• Plants are thought to have evolved from freshwater algae over 500 million years ago.

• Marked by four evolutionary events associated with four major groups of plants…..


Evolutionary History of Plants

– Nonvascular Plantsnourishment of a multicellular embryo

within the body of the female plant.– Seedless Vascular Plants

Advent of vascular tissue.– Gymnosperms and Angiosperms

Produce seeds.– Flowering Plants

Attract pollinators that give rise to fruits.


Alternation of Generations

• All plants have a life cycle that includes an alternation of generations.– Two multicellular individuals

alternate, each producing the other.Sporophyte = diploid generation.Gametophyte = haploid generation.



• 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.


Reduction in Size of Gametophyte



• 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.


Protection of Eggs and Embryos


Other Terrestrial Adaptations

• Vascular tissue transports water and nutrients to the body of the plant.

• Cuticle is an effective barrier to water loss.

• Stomata bordered by guard cells that regulate opening, and thus water loss.


Leaves of Vascular Plants


Nonvascular Plants

– Do not have true roots, stems, or leaves.– Gametophyte is dominant generation.

Produces eggs in archegonia and flagellated sperm in antheridia.

Sperm swim to egg in film of water.


Nonvascular Plants

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


Nonvascular Plants

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


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.


Moss Life Cycle


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.


Vascular Tissue


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.


Club Mosses


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.


Horsetail


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.


Whisk Ferns and Ferns


Fern Life Cycle


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.

– HeterosporousDrought-resistant pollen grains.Ovule develops into seed.


Gymnosperms (naked seeds)

Gymnosperms have ovules and

seeds exposed on the surface of

sporophylls.


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.


Conifers


Pine Life Cycle


Cycads• Cycads (phylum Cycadophyta) have large,

finely divided leaves that grow in clusters at the top of the stem. Oldest of the gymnosperms (about 320 million years ago)– Pollen and seed cones on separate plants


Ginkgoes

• Ginkgoes (phylum Ginkgophyta) – are dioecious (male and female plants)

with some trees producing seeds and others producing pollen.

– One surviving species =Gingko biloba


Gnetophytes

• Gnetophytes (phylum Gnetophyta)

believed to be closest to angiosperms because of similarity in xylem tissue and some even produce nectar for pollinators!


Angiosperms (covered seeds)

• Angiosperms (phylum Anthophyta) – are an exceptionally large and successful

group of plants.Produce flowersSeeds are enclosed in a fruit.Oldest fossils are 130 million years old


Monocots and Eudicots

• Two classes of flowering plants.– Monocotyledones (Monocots)

One cotyledon in seed.– Eudicotyledones (Dicots)

Two cotyledons in seed.


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).


The Flower

– Each stamen consists of an anther and a filament (stalk).

– Carpel has three major regions.Ovary - Swollen base.

FruitStyle - Elevates stigma.Stigma - Sticky receptor of pollen grains.


Flowering Plant Life Cycle


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. Evolution and Diversity of Plants.

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Transcript of Mader: Biology 8 th Ed. Evolution and Diversity of Plants.