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Introduction to Plant Diversity
Lecture 6
Spring 2014
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What is a plant??
What is a plant??
• Land plants
• Embryophytes
– Embryo
Fig. 29.4
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Evolution of plants
Plant traits shared with green algae
• Chloroplast structure
• Chlorophyll b
• Store food as starch
• Cell walls of cellulose
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Evolution of plants
Charophyceans
Plant traits shared only with
Charophyceans
• Rosette shaped celluosesynthesizing complexes
• Peroxisome enzymes
• Structure of flagellated
sperm
• Formation of a
phragmoplast
• Molecular analysis
Fig. 29.3
Fig. 29.2
The Move to Land
Why move to land at all?
Benefits from living on land
• Sun
• Abundant CO2
• Soil
• Few herbivores or pathogens
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Problems with moving to land
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4 problems to solve
1. Preventing water loss from cells
2. Protection from ultraviolet radiation
3. Transporting water from tissues with
access to water to tissues without access
to water
4. Reproducing in dry conditions
Problem #1: Preventing water loss
Solution
Evolution of cuticle
• Problems w/cuticle?
Solution
• Evolution of stomata
• Stomata trait of all land plants except liverworts
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Problem #2: UV Radiation
• Secondary compounds
• Flavanoids
Problem #3: Transporting water
• Tissues needed to be in contact with water
– Lack of rigidity
Solution
• Evolution of vascular tissue
• Rigidity
– Water pressure
– Lignin rings
Fig 35.10
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Problem #3: Transporting water
Problem #4: Reproducing in dry conditions
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Alternation of generations
• Alternation of multicellular haploid and diploid forms
Fig. 29.13
Problem #4: Reproducing in dry conditions
Changes in alternation of generation
Fig. 30.2
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Problem #4: Reproducing in dry conditions
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Walled spores produced
in sporangia
• Sporopollenin
• Transport in dry air
Fig. 29.5
Problem #4: Reproducing in dry conditions
Transporting gametes
Bryophytes and seedless vascular plants
• sperm swims to egg
Solution
• Pollen grain
• Trait found in gymnosperms, angiosperms
Pollen grain
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Problem #4: Reproducing in dry conditions
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Multicellular gametangia
• Contained on
gametophytes
• Archegonium
• Antheridium
• Protection
Fig. 29.5
Problem #4: Reproducing in dry conditions
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Multicellular, dependent
embryos
• Embryophytes
• Within gametophyte
• Placental transfer cells
Fig. 29.5
Derived traits of the Kingdom Plantae
Traits present in plants but not in charophyceans
• Alternation of generations
• Walled spores produced in sporangia
• Multicellular gametangia
• Multicellular, dependent embryos
• Apical meristems
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Derived traits of the Kingdom Plantae
Apical meristems
• Localized regions of cell
division
• Cells differentiate
Fig. 29.5
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Evolution of plants
• Nonvascular
plants
– Bryophytes
• Vascular plants
See Fig. 29.7
Evolution of plants
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• Seedless
vascular plants
• Seed plants
– Vascular tissue
– Seeds
See Fig. 29.7
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Evolution of plants
Gymnosperms
Exposed seed
Angiosperms
Enclosed seed
Diversity of plants
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Diversity of plants
Table 29.1
Major events in plant evolution
First evidence of land plants
475 million years ago
• Fossils
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Major events in plant evolution
Silurian-Devonian Explosion
410-360 million years ago
• Fossils from most of major plant lineages
• Adaptive radiation
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Major events in plant evolution
Carboniferous period - “age of the ferns”
320-290 million years ago
Major events in plant evolution
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• ~360 mya first seed plants (gymnosperms) appear
• Climate change at end of Carboniferous period
(320-290 mya)
– gymnosperms (250 to 120 mya)
Major events in plant evolution
“Age of angiosperms”
• 140-125 mya angiosperms appear
• 65 mya major diversification
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