Ch. 29

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• Ch. 29
• Plant Diversity I
• The Colonization of Land

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• Plant evolution
• A. Four main groups of extant plants

• bryophytes (mosses)
• -Mosses
• -Liverworts
• -Hornworts

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2. pteridophytes (ferns) -Lycophytes
-Ferns -Horsetail
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3. gymnosperms (pines and conifers)
4. angiosperms (flowering plants)
Dicots Monocots
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• Plants are
• 1. multicellular
• 2. eukaryotic
• 3. photosynthetic
• 4. autotrophs

1. 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.)

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• The Seed (360 MYA)
• Plant embryo packaged along with food
• supply and a protective coat.

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• The Flower (130 MYA)
• a complex reproductive structure that holds
• both male and female parts. The flower
• holds the seeds in the ovaries.

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• 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

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• Characteristics that separated land plants from
• charophycean algae

• Apical meristem region of cell division
• at the tips of roots and shoots.

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• Multicelluar, Dependent Embryos
• (Embryophytes) Parental tissue provides
• developing embryo with nutrients

Embryos
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• Alternation of Generations
• two multicellular body forms alternate,
• each form producing the other.

Sporophyte diploid multicellular
organism Gametophyte haploid multicellular
organism
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Antheridium male Archegonium female
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Life Cycle of Fern
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1. 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

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1. Other adaptations to land

1. 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.

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1. 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.
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• 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

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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)

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• Three versions of the plant kingdom
• 1. Kingdom Plantae
• 2. Kingdom Streptophyta
• 3. Kingdom Viridiplantae

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III. Bryophytes

• Phylums Mosses, Liverworts, and
• Hornworts

1. Gametophyte is the dominant generation
2. Flagellated sperm
3. Most have no vascular tissue
4. Short stature (no lignin)

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• 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

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1. 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.

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Lycophyta club moss have small leaves known
as microphylls.
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Ferns have megaphylls which are larger leaves,
made possible because of the higher branched
vascular system. ? Greater photosynthetic
productivity