Plant Diversity

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Plant Diversity

• Chapter 29-30

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Evolution

• Evolved from green algae ancestor
• Charophytes (green algae)
• Closest plant relative
• Over 470 million years ago

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Evolution

• Similarities shared with algae
• Autotrophs
• Multicellular eukaryotes
• Cellulose in cell walls
• Chlorophyll a and b

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Fig. 29-4
Red algae
ANCESTRAL ALGA
Chlorophytes
Viridiplantae
Charophytes
Streptophyta
Plantae
Embryophytes
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Evolution

• Traits derived by plants
• 1. Embryophytes
• Embryos develop in maternal tissues
• 2. Sporangia
• Walled spores
• 3. Multicellular gametangia
• 4. Apical meristems

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Evolution

• Move to land-less water
• Cuticle
• Waxy substance - protects water loss
• Stomata (stoma-singular)
• Opening in leaf
• Gas exchange

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Evolution

• Leaves
• Yields greater photosynthesis surface
• Dominant diploid phase
• Shorter haploid stage
• Structural support of vascular tissue

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Fig. 29-6
(a) Fossilized spores
(b) Fossilized sporophyte tissue
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Fig. 29-5a
Gamete from another plant
Gametophyte (n)
Mitosis
Mitosis
n
n
n
n
Spore
Gamete
FERTILIZATION
MEIOSIS
Zygote
2n
Mitosis
Sporophyte (2n)
Alternation of generations
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Fig. 29-5e
Apical meristems
Developing leaves
Apical meristem of shoot
Apical meristem of root
Shoot
Root
100 µm
100 µm
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Life cycles

• Alteration of generations
• Multicellular haploid diploid
• Brown, green red algae have similar life cycle

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Life cycle

• Gametophyte
• gamete plant
• Haploid generation
• Produce haploid gametes through mitosis
• Fuse during fertilization (zygote)

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Life cycle

• Sporophyte
• spore plant
• Diploid generation
• Meiosis produces haploid spores
• Leads to multicellular haploid gametophyte

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Life cycle

• Sporangia
• Where meiosis takes place
• Diploid produces 4 haploid spores
• Multicellular haploid gametophyte

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Life cycle

• Gametangia
• Structures where gametes are produced
• Mosses
• Large part of life cycle is haploid
• Vascular plants gametophyte is much smaller

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Fig. 29-5a
Gamete from another plant
Gametophyte (n)
Mitosis
Mitosis
n
n
n
n
Spore
Gamete
FERTILIZATION
MEIOSIS
Zygote
2n
Mitosis
Sporophyte (2n)
Alternation of generations
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Life cycle

• Seed plants
• Gametophyte are nutritionally dependent on the
  sporophytes
• Gametophyte generation gets smaller
• More specialized for land

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Plant diversity

• Nonvascular plants
• Lack vascular tissue
• Vascular plants
• Contain water-conducting xylem
• Food-conducting phloem
• Stems, leaves and roots

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Groups

• 1. Nonvascular land plants
• Mosses, liverworts, hornworts
• 2. Seedless vascular plants
• Club mosses
• Ferns
• 3. Gymnosperms (naked seed)
• 4. Angiosperms (flowering plants)

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Fig. 29-7
Origin of land plants (about 475 mya)
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Origin of vascular plants (about 420 mya)
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3
Origin of extant seed plants (about 305 mya)
Liverworts
Nonvascular plants (bryophytes)
Land plants
Hornworts
1
ANCES- TRAL GREEN ALGA
Mosses
Lycophytes (club mosses, spike mosses, quillworts)
Seedless vascular plants
Vascular plants
2
Pterophytes (ferns, horsetails, whisk ferns)
Gymnosperms
3
Seed plants
Angiosperms
500
450
400
50
0
350
300
Millions of years ago (mya)
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Table 29-1
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Liverworts, hornworts
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Seedless vascular plants
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Gymnosperms
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Angiosperms
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Nonvascular land plants

• Usually small
• Lack vascular tissue to carry water to aerial
  parts of the plant
• Found in damp, shady habitats
• Need water to reproduce sexually
• Gametophytes are photosynthetic
• More visible (green)
• Sporophytes are attached to the gametophytes

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Nonvascular land plants

• Mosses (Bryophytes)
• Rhizoids roots
• Cells to absorb water
• leaves
• Green, haploid, single cell layer thick
• Most abundance in the tropics
• Very sensitive to air pollution

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Moss
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Seedless vascular plants

• Earliest form of vascular plants
• Need external water for fertilization
• No seeds
• Sporophyte more complex
• Both sporophyte gametophyte are photosynthetic
• Live independently

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Ferns
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Seed plants

• 425 million years ago
• Seeds gives the plant advantages
• 1. Protection of embryo by sporophyte
• 2. Easier to disperse
• 3. Dormant stage

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Seed plants

• 2 kinds of gametophytes
• Male (pollen grains)
• Female (ovule)
• No need for external water
• Sperm move to egg in a pollen tube

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Gymnosperms

• Gymnos Greek for naked
• Sperma with seed
• Lack flowers and fruit
• Ovules are naked at time of pollination
• Pines, firs, spruces, larches, yews, junipers,
  cedars, cypresses, and redwoods.

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Angiosperms

• Flowering plants
• Ovules are closed by diploid tissues at time of
  fertilization
• Angeion means vessel in Greek
• Sperma seed

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Flower structure

• Receptacle
• Where flower parts are attached
• Sepals
• Green leaf like
• Protect the immature flower

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Flower structure

• Petals
• Colored, attract pollinators
• Stamens (male gametophytes)
• Anther Pollen producing
• Filament a stalk
• Carpels (female gametophytes)
• Ovule(base), ovary, stigma and style (connects
  the stigma to the ovary)

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Flower structure
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Life cycle

• Pollination
• Pollen transfers to the stigma
• Self-pollination or from another plant
• Produce a germinating seed
• Young sporophyte (diploid)

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Life cycle
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Benefits

• Food
• Rice, wheat, potatoes
• Coffee, tea, cocoa
• Medicines
• Digitalis (heart med)
• Morphine (pain relief)
• Fuel
• Wood