Plantschapter 29

APBiology: overview

Key Concepts:

The plant kingdom consists mostly of multicelled photoautotrophs

Almost all plants live on land

Plants have structural adaptations that allow them to photosynthesize, absorb water and ions, and conserve water

Land plants are reproductively adapted to withstand dry periods

Key Concepts:

Seed producers were more successful in radiating into drier environments based on an evolutionary scale

Gymnosperms and angiosperms are vascular plants

Angiosperms include two classes of flowering plants Dicots and Monocots

Evolutionary Trends Among Plants

Photoautotrophs

Vascular plants Roots, stems,

leaves

Gymnosperms

Seed bearing

Gingko

Cycads

Conifers

Angiosperms Flowers and seeds

Dicots and Monocots

Non-vascular plants Bryophytes

Liverworts

Hornworts

Mosses

Evolution of Roots, Stems, and Leaves

Roots and Stems Below ground

Shoot systems Stems and leaves

Above Ground

Sunlight and CO2

Support of cell wall

Lignin

Vascular tissue Xylem

Phloem

Water conservation Cuticle

Stomata

Evolutionary Trend Among Plants

Alternation of generations

Evolution of Pollen and Seeds

HomosporyHeterospory

Pollen grainsSperm-bearing gametophytesFemale gametophytes

Spread by air, insects, birds

Seeds Embryo of gametophytes Nutritive tissues Protective coat

Bryophytes

Mosses

Liverworts

Hornworts Nonvascular

Moist habitats mostly

Small

< 20 cm tall

Simplest plants

Bryophytes

Moss Life Cycle

Moss Life Cycle

Existing Seedless Vascular Plants

Whisk ferns, Lycophytes, Horsetails, Ferns 3 Differences from Bryophytes

Sporophyte not attached to a gametophyte

Has vascular tissuesLonger phase in life cycle

Habitat Moist places

Gametophytes lack vascular tissueSperm needs water to reach egg

Life Cycle of a Fern

Life Cycle of a Fern

The Rise of the Seed-Bearing Plants

Seed ferns, gymnosperms, angiosperms Pollen grains

Male gametophytes

Ovules

Egg producing gametophytes

Pollination

Pollen grains arrive on female reproductive structures

Independent of water for fertilization

Note the decrease in size of Gametophyte generation

Important Adaptations for land plants

Vascular tissue transports water and Vascular tissue transports water and nutrients to the body of the plantnutrients to the body of the plant

Cuticle provides an effective barrier to Cuticle provides an effective barrier to water losswater loss

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

Ferns

Spore of A Lycophyte

Seed-Bearing Plants

Depend on

Pollen grains

Ovules that mature into seeds

Tissue changes adapted to dry conditions

Gymnosperms- Plants with “Naked” Seeds

Conifers, Cycads, Ginkgos, Gnetophytes Conifers - cones

Pines, cypress, firs, spruces, redwoods

Lesser Known Gymnosperms

Cycads Tropical

Subtropical areas Largest seed-

bearing cones Zamia in Florida

Gingko Gingko biloba Diverse in

dinosaur times

Gnetophytes Gneton

Tropics

Ephedra

California

Welwitschia mirabilis

Deserts in Africa

Pines

AngiospermsThe Flowering Seed-Bearing Plants

Flowers

Coevolution with pollinators Insects

Bats Birds

Seed

Ovary

Dicots and Monocots

Almost 180,000 Dicots are herbaceous Cabbage and Daisies

Flowering shrubs and trees

Water lilies

Cacti

About 80,000 Monocots Orchids, palms, grasses, crop plants, rice

In Conclusion

Plants probably arose from green algae

Trends in evolution can be identified by comparing structural adaptations to dry conditions, shifts to diploid dominance, and the shift to heterospory

Bryophytes are nonvascular plants and require free water for fertilization

Vascular plants are adapted to life on land

In Conclusion

Gymnosperms are vascular plants that produce pollen grains and seeds

Ovules contain the egg-producing female gametophytes

Evolution of pollen grains freed these plants from dependence on water for fertilization

Angiosperms produce flowers and coevolved with pollinators