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Summary Course 9 Plant Biology term I
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Summary of all lectures of Course 9 Plant Biology term I with all accompanying chapters of Smith's Plant Biology book
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Plant biology course 9 term IWeek 1 Plant origins
Main stages of plant revolution
- 1st indication of life: first cells
- From prokaryotic to eukaryotic cells
- Evolution of eukaryotes (plants)
- Reproduction cycles
- Colonization of the land
- The first forests
- Emergence of seed plants
- Flowering plants
- Evolution of grasses
After big bang the earth needed to cool down
No ozone layer!
3,5 billion years ago first photosynthesis → cyanobacteria in Archean era
Origin of life – Archean era (3,5 BYA)
- Stromatolites: form of coral made by bacteria who form a layer of sediment
- Primitive form of photosynthesis = prokaryotes, cyanobacteria
o First production of oxygen
Prokaryotic cells
- No organelles
- Single cell
- Protection against radiation
• Living in water
• Layer to protect: mucilaginous sheath
• Biochemical DNA repair system
- Asexual reproduction
• No DNA shuffling
From prokaryotic to eukaryotic cells
- 1st endosymbiotic event:
• Host cell nature not known (maybe Archaea)
• Alpha-proteobacterium engulfed by host cell → origin of mitochondria
▪ Mitochondria today still have prokaryotic genome, nucleus genome eukaryotic
▪ Formation of heterotrophic eukaryotic cells
- 2nd endosymbiotic event:
• Some groups engulfed cyanobacterium → origin of plastids
▪ Formation of autotrophic eukaryotic cells
1
,Photosynthetic eukaryotic organisms
- 3 clades of protist
• Glaucophytes
• Red algae
▪ Rhodophyte = dried red algae, used for
sushi for example
• Green algae → origin of land plants
- Produces oxygen
Meiosis: shuffling of DNA
Mitosis: no shuffling of DNA
2
,570 million years ago Cambrian explosion
- Drastic changes, rising oxygen levels and formation ozone layer
• UV radiation absorbed
• Evolution rate accelerated
- Plants moving to land! (still needed another 100 million years to get there)
First life on land
- Bryophytes: mosses and liverworts
- Lichen
• Symbiosis between algae, cyanobacteria and fungi (and yeast)
Colonization on the land
- New features necessary against desiccation (uitdroging)
• Cuticle → wax layer on top of epidermis leaves
• Stomata
• Sporopollenin (protection of spores)
• Rhizoids
▪ Primitive roots
- Non-vascular plants
• Bryophytes → embryophytes class
▪ Gametophytes (gamete producing) are larger than the sporophytes (spore
producing)
▪ Mosses
▪ Liverworts
• Large gametophyte (the green you see of the moss)
• Haploid
• Hydroids (primitive vascular cells)
Female and male gametophytes → needs water to start fertilization (not fully adapted to living on land)
3
, Transition
- It went so well, no space left on the ground → plants needed to go up → trees and first forest
- Less CO2 = bigger leaves and more stomata to catch as much as possible
First forest
- New features needed → tracheophytes (tube/vascular plants)
• Xylem and phloem
• Roots
• Secondary growth (thickness)
▪ Lignin → many fossils as
lignin is not decayable
▪ Cambium
- Emergence of vascular plants as large as
trees nowadays
- Megaphylls: Telome theory
• The theory that the leaves
(megaphylls) of ferns and seed
plants evolved by the modification
of terminal branches (telomes) of
stems.
• Through evolution branches got
sterile (lost their spores) → flattened
→ connection between branches
with lamina (leaf tissue)
- Correlation leaf size to CO2 level = negative
• Less CO2 means larger leaves
- Still seedless, produces pollen
Difference micro- and megaphylls:
Size of leaves → micro small and mega large
Microphylls have 1 unbranched vein, whereas megaphylls have multiple veins
Ferns
- Sporophytes are the green leaves
- Fertilization needs water
- Plants are haploid
4
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