Ch. 29 Plant Diversity I: The Colonization of Land
Plant evolution • A. Four main groups of extant plants: • bryophytes (mosses) • -Mosses • -Liverworts • -Hornworts
2. pteridophytes (ferns) -Lycophytes -Ferns -Horsetail
3. gymnosperms (pines and conifers) 4. angiosperms (flowering plants) Dicots Monocots
Plants are • 1. multicellular • 2. eukaryotic • 3. photosynthetic • 4. autotrophs • How did they colonize the land? • Vascular tissue: tubes that transport • water and food. • a. However, most bryophytes do not have • vascular tissue. • (What makes • them adapted • to land is their • reproductive • adaptations.)
The Seed (360 MYA): • Plant embryo packaged along with food • supply and a protective coat.
The Flower: (130 MYA) • a complex reproductive structure that holds • both male and female parts. The flower • holds the seeds in the ovaries.
Colonization on land overview: • Algae Bryophytes Vascular Plants • Seed Flowers • Charophyceans: Green • algae (closest plant • ancestor) • Similarities between • charophyceans and • land plants: • a. Produce cellulose • in a similar way • b. Peroxisomes • c. Flagellated sperm
Characteristics that separated land plants from • charophycean algae: • Apical meristem: region of cell division • at the tips of roots and shoots.
Multicelluar, Dependent Embryos • (Embryophytes): Parental tissue provides • developing embryo with nutrients Embryos
Alternation of Generations: • two multicellular body forms alternate, • each form producing the other. Sporophyte: diploid multicellular organism Gametophyte: haploid multicellular organism
Antheridium: male Archegonium: female
Walled Spores produced in Sporangia: • Spores: haploid cells that grow into • multicellular gametophyte by mitosis. • -made from sporopollenin • -made in the sporangia (singular = • sporangium) • -made from the “spore mother cells” • Multicellular Gametangia: gametophyte • a. produce the haploid gametes • b. Female: archegonia - egg • c. Male: antheridia – sperm with flagella
Other adaptations to land: • Water conservation: • Cuticle: waxy polymer protects the • plant from microbial attack and acts as • waterproofing, preventing excess water • losss. • Stomata: Open for exchange of CO2 • and oxygen; close to minimize water • loss in hot, dry weather.
Water transport: • Roots, stems, and leaves have vascular • tissues (tube system). -Xylem: tubes that carry water and minerals up from the roots. -Phloem: tubes that distribute sugars, amino acids, and other organic molecules throughout the plant.
Secondary Compounds: alkaloids, • terpenes, tannins, flavonoids. • -toxic to defend against hervibores • -flavonoids absorb UV radiation • -human use: alkaloid quinine is used to • help prevent malaria
II. The Origin of Land Plants • Land plants evolved from green algae • (probably charophycean) over 500 MYA. • Evidence: • Homologous chloroplast (DNA analysis) • Homologous cellulose walls (cellulose- • manufacturing rosettes) • Homologous peroxisomes (anti-photo- • respiration enzymes in peroxisomes) • Phragmoplasts (cell wall forms only • during cell division in charophyceans • and land plants) • Homologous sperm • Molecular systematics (rRNA, and • protein analysis)
Three versions of the plant kingdom: • 1. Kingdom Plantae • 2. Kingdom Streptophyta • 3. Kingdom Viridiplantae
III. Bryophytes: • Phylums: Mosses, Liverworts, and • Hornworts • Gametophyte is the dominant generation • Flagellated sperm • Most have no vascular tissue • Short stature (no lignin)
The Origin of Vascular Plants: Origin of • the pteridophytes, gymnosperms, and • angiosperms • Vascular plants differ from bryophytes: • 1. Vascular tissue • 2. Dominant sporophyte generation • 3. Independent sporophytes
Pteridophytes: Seedless vascular plants • Lycophyta: “club moss” (not a moss) • Ferns B.Pteridophytes provide clues to the evolution of roots and leaves • Lycophyta have small leaves with only • one unbranched vein.
Lycophyta: club “moss” have small leaves known as “microphylls.”
Ferns have megaphylls which are larger leaves, made possible because of the higher branched vascular system. Greater photosynthetic productivity