mader: biology 8 th ed. evolution and diversity of plants chapter 24

Mader: Biology 8th Ed.

Evolution and Diversity of Plants

Chapter 24


Outline

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

– Seedless– Seed– Angiosperms

Monocots and EudicotsFlowers


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.


Evolutionary History of Plants

– Seedless vascular plants Advent of vascular tissue.

– Gymnosperms and angiospermsProduce seeds.

– Flowering PlantsAttract pollinators that give rise to fruits.


Four Major Plant Groups


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.



• 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 provides an effective barrier to water loss.

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


Leaves of Vascular Plants


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.


Nonvascular Plants

• Hornworts (phlym 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


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.


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

• Gymnosperms have ovules and seeds exposed on the surface of sporophylls.– Confiers– Cycads– Ginkgoes– Gnetophytes


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.– Pollen and seed cones on separate plants.

Pollinated by insects.


Ginkgoes

• Ginkgoes (phylum Ginkgophyta) are dioecious, with some trees producing seeds and others producing pollen.– One surviving species. (Gingko biloba)


Gnetophytes

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


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.


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.


Review

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

– Seedless– Seed– Angiosperms

Monocots and EudicotsFlowers

mader: biology 8 th ed. evolution and diversity of plants chapter 24

Documents

seed plants

evolution of plants

flowering plants

leaves of vascular plants

size of gametophyte

major groups of plants

diversity of plants

eudicots flowers slide