Exam 2
Photosynthesis
Orgins
Photosynthesis evolved later. 
-3.5 bya Stromatolites 
Layers of photosynthetic bacteria/cyanobacteria
Cyanobacteria 
-
2bya Rusting of the earth
Environment changes and iron formations disssapear.
waters, oceans, fossils
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Oxygen on early was less than now.
Pigments
Photosynthesis reverses respiration
Chlorophyll similar to hemoglobin and likely common ancestor
Absorbed light energy
Chlorophyll
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A and B 
wavelenths that photosynthesis would be limited to is 550.
Action Sprectrum 
: 
Resonance energy
Chlorophyll a is most likely to show
Photosytems
Photosystems I and II. Photosystem I compared to photosystem II has more chlorophyll a pigments,
Controlled Energy Release
Photosystems connected by ETS
Electron transport chain
Joins PSII to PSI
All in order to run ATP synthase
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Photophosphorylation 
Cyclic Photophosphorylation
Noncyclic Photophorylation
NADPH
Photolysis
Proton Pump
Photosystem I compared to Photosystem II has more chlorophyll a pigments.
Light provides the energy to drive the thylakoid reactions
Water provides electrons via photolysis
Oxygen is the a by-product
NADPH is the final electron acceptor
Produces some ATP
The fate of an electron boosted from the reaction center of photosystem II is to picked up by pheophytin next.
Stromal Reactions 
Photorespiration 
Gluconeogenesis 
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Products of the thylakoid reaction become reactants for the stromal reaction
Energy (ATP) from the thylakoid reactions run the stromal reactions
CO2 is fixed into G3P
Life On Land
Evidence for embryophyte emergence
Relatively more Co2
Terrestrialization
Evolved from algae
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Fossil Evidence
Liverwort Macrofossils ~390MA
First Macrofossils~425MA
Vascular Plants
Specialized conducting cells
Evidence from spores ~443 Ma
Tracheid fossils ~415 Ma
Diversity exploded in Devonian (415-360Ma)
Dominant sporophyte no longer restricted to damper areas
Land plants evolved under lower levels of oxygen compared to current to oxygen levels
Land Plants likely evolved from algae
Major evolutionary innovations
Major evolutionary innovations 
Sporophyte Generation
Vascular Tissue
Leaves and Stromata #
roots
Seed evolution
Flower evolution
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Many morphological changes as plants adapted to life on land
Further selection from competition
Diversification accommodate life cycle changes and coevolution
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Plant life cycles generally involve the following 2 stages gametophyte and sporophyte
Flagellated sperm is not considered an innovation to living life on land.
Life Cycle Evolution
Algal ancestor haplontic (Greek, haploos + einai = single being)
Alternation of Generations Current land plants
haplodiplontic (Greek, haploos + diploos + einai = single double being)
Antithetic Theory
Predictions
A haplontic life cycle would include multicellular haploid individual, gametes,zygote
The antithetic theory proposes that the evolution of the sporophyte was the result of the zygote dividing mitotically rather than meiotically.
Gametophyte dominant)
Marchantiophyta
Gametophyte
Sporophyte
Bryophyta
Sporophyte
Within the sporangium meiosis, spores take place resulting in meiosis spores.
The green leafy moss plant that you walk on is haploid.
Sporophyte dominant, gametophyte & sporophyte independent
Lycophyte
Gametophyte
#
Sporophyte
Sporophyte
Gametophyte
For a lycophyte such as Selaginnella, the female spores are contained in a megasporangium.
Within the antheridium of a fern, the sperm are produced.
Sporophyte dominant, gametophyte reduced
Gymnosperm
Sporophyte
#
Gametophyte
Angiosperm
Sporophyte
Microgametophyte
Megagametophyte
Stromata
Origins and Derivations
Early Evolution
Stomata
Shapes
Aid in desiccating sporophyte 
Lower Stomatal Frequency
Innercellular spaces 
Flower Plants
Stomata evolved prior to seeds,seeds,vascular tissue,and flowers
Stomata can be found in fern sporophytes
In Bryophyta such as mosses, the stomata mostly aid in desiccating the sporangium
Functional considerations
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Guard cell control 
Photosynthetic dependent 
#
water use efficiency
Indeterminate growth
Trait evolution
Apical Meristem
Mitosis
Bifurcating sporophyte #
Terminal sporophyte
Convergent Evolution
Shoot apical meristem
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Both Sporophyte
Stromata
Photosynthesis