Major Sections of Chapter
Lower Plants
Gymnosperm
Angiosperms: flowering plants

Lower Plants

Topics

Reminders

• Brown chp 27, pp 559-580
• Emphasis: class outline
• Study Outline: pp 580-581
• Self Quiz: 581-582

1. An Introduction to the Plant Kingdom

• Generalized view of reproduction and life cycles
• fig. 27.2 and 27.3
• General Characteristic of Plants
  • multicellular
  • photoautotroph
  • primarily terrestrial
  • roots, stems and leaves
  • waxy cuticle
  • stomata
  • chloroplasts: chlorophyll a, chlorophyll b
  • altenation of generations
    • sporophyte generation - diploid
    • gametophyte generation - haploid
  • sporangium - spores
  • gametangia
    • antheridium - spermatozoa
    • archeogonium - eggs
  • nonvascular or vascular
    • xylem
    • phloem

2. Some highlights of Plant Evolution

• (fig.27.3)
• aquatic ancestors (green algae)
• origin of plants
  • multicellular algae
  • mosses
• The Move Onto Land
  • green algae as ancestors
    • 1) similar chlorophyll
    • 2) chloroplasts similar, grana and thylacoid membrane
    • 3) cell wall cellulose
    • 4) starch
    • 5) cell plate from Golgi bodies
• Characteristics of first terrestrial plant
  • early vascular tissue
  • cuticle
  • gametangia
  • new frontier
    • sunlight
    • rich soil
    • no herbivores
  • fig. 21.7
• origin of seeds
  • pollination
  • gymnosperm
  • angiosperm - radiation of flowering plants

Other Major Steps in Plant Evolution

• vascular tissue
• origin of seeds
• pollination
• gymnosperm
• angiosperm - radiation of flowering plants
• fig 27.3

3. Classification of Plants

• Table 27.1
• nonvascular plants
• seedless vascular plants
• seed plants

4. Nonvascular Plants

• Bryophytes
  • Mosses (Division Bryophyta)
  • Liverworts (Division Hepatophyta)
  • Hornwarts (Division Anthocerophyta)
• Bryophytes - Characteristics
  • aquatic environment, need water
  • no vascular tissue, diffusion
  • rhizoids
  • live in damp shady places
  • no woody tissue
  • tightly packed together
  • stem-like and leaf-like structures are not homologous to stems and leaves
  • alternation of generation - haploid and diploid
  • flagellated spermatozoa
  • 1-2 cm in height, maximum 20 cm
• not totally liberated from an aquatic environment

5. Seedless Vascular Plant

• Terrestrial Adaptations of Vascular Plants
  • Division Psilophyta
  • Division Lycophyta
  • Division Sphenophyta
  • Division Pterophyta
  • The Coal Forests

6. Terrestrial Adaptations of Vascular Plants

• cuticle and jacketed gametangia
• do not need immediate aquatic environment
• roots - no cuticle
• woody material - cellulose and lignin
• vascular tissue
  • xylem - dead, capillary action
  • phloem - transport by diffusion, active transport
• dominance of sporophyte

Division Sphenophyta

• Equisetum
  • damp locations
  • homosporus
  • bisexual gametophyte
  • 15 species

Division Pterophyta

• ferns
  • Devonian origin
  • tropical and temperate forests
  • megaphyll - frond
  • sporophyll
  • sori
  • flagellated spermatozoa
  • 12,000 species
  • most are homosporus

Gymnosperm

Topics

Seed Plants

• General characteristics
  • terrestrial adaptation
  • gametophytes of seed plants become more reduced and dependent on sporophyte
  • heterosporous (mega- and microspores)
  • pollination replaces swimmimg as the mechanism for delivering sperm to egg, spores no longer dispersed
  • The seed evolved

Gymnosperms

• Classification
  • Division Coniferophyta (conifers)
  • Division Cycadophyta (cycads)
  • Division Ginkophyta (ginko)
  • Division Gnetophyta (gnetae)

The History of Gymnosperms

• Devonian period - progymnosperm
• seeds
• adaptive radiation lead to four groups by the Permian Period
• conifers and cycads dominated the Mesozoic Era, a drier climate
• conifers persisted into Cenozoic Era, a cooler time

Division Ginkgophyta

• deciduous
• ornamental cutivation
• native to China
• flourished in Mesozoic Era
• living fossil
• maidenhair tree
• stone "fruit"

General comments on Gymnosperms -Division Coniferophyta

• (many more extinct species in the Mesozoic era)
• evergreens
• largest living organisms - redwoods (Sequoia sempervirens) 300 x 30 ft
• oldest living organisms - bristlecone pine, 4,600 years old
• ecologically, gymnosperms dominate vast regions of northern temperate forests
• most important forest resource; about 80% of forest products such as lumber, poles, paper, resins, Christmas trees
• very important for wildlife in food and shelter

Characteristics of Gymnosperms

• sporophyte dominant: gametophyte very reduced
• multicellular female gametangium (archegonium) but no male gametangium (male gametophyte reduced to a few cells and a pollen tube)
• ovules (modified megasporangium) contain the female gametophyte; after fertilization and formation of zygote, then embryo becomes a seed.
• no external water required for fertilization
• vascular cambium leads to secondary growth (wood)

Life cycle of a pine fig. 27.17

• sporophyte
• ovule
• mother megaspore
• megaspore
• female gametophyte
• archegonium
• egg
• zygote
• seed
• sporophyte
• pollen cone
• microspore
• male gametophyte = pollen
• zygote
• embryo
• seed

Angiosperms: flowering plants

Topics

Classification

• Division Anthophyta
  • Class Monocotyledones (monocots)
  • Class Dicotyledones (dicots)

The Rise of Angiosperms

• Early Cretaceous
• 120 million years
• sudden appearance
• may have evolved from seed ferns, an aberrant gymnosperm
• demise of dinosaurs

General Features of Angiosperms

• photoautotrophs, saprobes, parasitic
• 235,000 species
• one division and two classes
• monocots - lilies, grasses, corn, wheat, palms
• dicots - roses, maples, oaks, peas, beans
• most pollination by insects, birds, and other animals, some by wind
• vascular specialization - vessel elements
• flower - increase the efficiency of reproduction
• fruit

The Flower

• modified leaves
• sepals - usually green
• petals - brightly colored - insect pollination
• petals - drab - wind pollination
• carpel - female reproductive organ
  • stigma
  • style
  • ovary
• stamen - male reproductive organ
  • anther
  • filament

The Fruit

• protects dormant seeds
• mature ovary
• simple fruit - single ovary in one flower
  • pea pod, apple
• aggregate fruit - several ovaries in one flower
  • raspberries
• multiple fruit - from separate flowers
  • pineapple
• modifications for dispersal
  • attractive food
  • dispersal by wind
  • burrs

The Life Cycle of an Angiosperm

• sporophyte sporophyte
• flower flower
• ovary anther
• ovule
• megaspore microspore
• female gametophyte male gametophyte
• embryo sac pollen
• egg sperm nucleus
• zygote
• seed
• fruit

Some Features of Angiosperm Life Cycle

• cross-pollination
• embryo sac - 8 haploid nuclei and then 7 cells
• double fertilization
• cotyledons
• endosperm (3N or more)

Relationships between Angiosperms and Animals

• pollination
• bee pollination - ultraviolet
• attractive fruits
• coevolution of angiosperm and animals
  • bees and flowers
  • flies and carrion plant
  • humminng birds and red flowers (no odor)
  • bats and baobab - bloom at night
  • orchids and male wasps
  • yucca and moth

Economic Importance

• 80% of world's food: wheat, corn, rice, potatoes, barley, manioc, sweet potatoes
  • roots - carrot, radish, turnip
  • fruits - oranges, banadas, tomatoes, apples, pineapples, mangoes
  • seeds - peanuts, peas, soybeans, coconut (endoderm)
  • stems or leaves - onions, asparagus, artichokes, lettuce, spinach
• corn plants: tremendous decrease in genetic diversity, however, great potential for genetic engineering
• diversity
  • pesticides
  • medicines - taxol, Pacific Yew Tree, breast cancer: perwinkle - vinblastine, treatment for leukemia: willow bark - acetylsalicylic acid
  • perfumes
  • spices