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Evolution of Terrestrial Plants, Molecules that absorb particular…
Evolution of Terrestrial Plants
Life on Land
Evidence for embyrophyte emergence:
Terrestrialization
multicellular sporophye
embryo retained in female gametophyte
Fossil Evidence
liverworts macrofossils
cooksonia sporophytes
Stomata
conducting elements
Vascular Plants
Tracheid fossils
evidence from spores
special conducting cells
GREEN ALGAL ANSCESTOR
Charophycean green algae
haploid, gamete-producing generation
Major Evolutionary Innovations:
Stomata
surface:
often aerial covered in cuticle
Guard cells
balance gas exchange necessary for photosynthesis
actions can open/close stomatal pore
control water loss
all land plant sporophytes
EXCEPT LIVERWORTS
Surrounded by:
Vascular Tissue
Water conducting cells
conduct water and nutrients
Food conducting cells
conduct carbs and amino acids
Sporophyte Generation
Sporophyte Origins
antithetic theory:
suggests sporophyte originated by mitotic division of the zygote before meiosis
results in a diploid embryo
supported by:
dominance of gametophytes over sporophytes:
bryophytes
absence of sporophytes:
charophyte algae
Alternation of Generations
Roots
Evolution:
evolved root cap
evolved newy way to branch
Lineages:
some may have evolved from leaves
evolved a cuticle early on
downward growing rhizomes
Positive Gravitropism
growing according to gravity
Negative phototropism
growing away from sunlight
Seed Evolution
Gametophyte
Completely dependent on Sporophyte
egg protected by special layers of tissue
Angiosperm
ancestors:
Unknown
Gymnosperm
extinct groups:
seed ferns
Carboniferous--Permian Medullosans
Groups:
Bennettitales
Glossopteridales
Gigantopteridales
Gnetopsida
monocots
caryophyllids
Flower Evolution
Stem specialization
Attraction
Dispersal
co-evolution
Photosynthesis
Concepts
Origins
Evidence
Stromatolites
layers
Photosynthetic bacteria
Cyanobacteria
Close to LUCA
Iron Earth
++ photosynthesizers
Iron enriched environment
Iron formations
Iron oceans
Iron loving microbes in fossil record
Archaea Present
Bacteria Present
CHANGING ENVIRONMENT!
Iron rich oceans gone
Oxygen enriched oceans precipitated iron
Eucarya
Iron formations disappeared
Iron loving microbes dropped out of fossil record
Little Oxygen in atmosphere
Pigments
Early Usage
Sunscreen
Cyanobacteria with scytonemin in sheath
Photosystems
Consist of:
Antennal Complex
ANTENNA COMPLEX
Absorbed energy is moved around via resonance energy
Funneled to REACTION CENTER
Energy absorption (light) and excitation occurs in organized complexes of:
Accessory Pigments
Chlorophyll pigments
Reaction Center
PSII
P680
Absorb shorter wavelengths
Chl B >> Chl A
Hydrolysis
PSI
P700
Absorb longer wavelengths
Chl a >> Chl b
Embedded in Thylakoid Membrane
Thylakoids
protons trapped inside
CONNECTED By:
Electron Transport System
Non Cyclic Photophosphorylation
Involves:
PSII
Plastoquinone
Cytochrome b6f
plastocyanin
PSI
-E moves:
Ferredoxin-
ferredoxin-NADP reductase
Final electron acceptor:
NADP+
NADPH
1 more item...
all in order to run ATP Synthase
force Pi onto ADP to form ATP
Cyclic Photophosorylation
electron flow:
doesnt directly create ATP
coupled with flow of protons
when through cyt b6,f
electron energy: drops when flow through cyctochrome b6f complex
Involves:
PSI
Plastoquione
Cytochrome b6f
Plastocyanin
Stromal Reactions
Fixation
Co2 bound to RuBP (c5)
Immediately breaks into two C3
Reduction
Energy from ATP stored into C3 molecule
Energetic electrons reduce C3
NDPH-NADP+
Ends in a pool of G3p
Regeneration
Carbon Shuffling
RuBP back
uses more ATP
CYCLE REPEATS
Reactants= products from thylakoid reactions
Life Cycle Evolution
Alternation of Generations
completes full cycle:
land plant must pass through:
diploid sporophyte generation
hapliod gametophyte generation
Cell Division
Meiosis
halves # of sets of chromosomes per cell
one dipliod parent cell divides to yeild 4 hapliod daughter cells
Mitosis
Haploid
single body
1n
gametophyte
gamete producing
Diploid
2n
double body
sporophyte
spore producing
Zygote
fertilized sperm and egg cell
diploid cell
grows and divides
Interpolation Theory
Sporophyte:
in earliest/simple forms:
cells may have undergone meiosis to produce spores
heteromorphic
short lived
first arose:
zygote undergoes period of replication before meiosis
structural evolution:
speculative
Early Evolution:
consists of:
foot
seta/stalk
some early sporophytes lack
sporangium/spore capsule
attached to:
Gametophyte
photosynthetic
Gametophyte
in earliest forms:
complex
persistant organisms
Life Cycles:
Sporophyte Dominant
Lycophytes
Selaginella example
Heterosporous
Strobilus
Sporangia
Male
Microsporangia
microsporocytes
1 more item...
Female
Megasporangia
megasporocytes
1 more item...
Gametophye Dominant
Marchantiophyta
example: Liverwort life cycle
Dominant leafy Gametophyte
sporophyte diploid structure small and temporary
Dominant life stage
Male
Antheridiophore
Antheridia
contain sperm
Female
Archegoniophore
Archegonia
Contain eggs
Sporophyte
parasitic on gametophyte
sporangium:
meiosis occurs
sporocytes 2n
spores 1n
Bryophyta
Dominant Life Stage:
Male
Antheridial head
Antheridia
contain sperm
Female
Archegonial head
Archegonia
contain eggs
Mnium moss example
Dominant leafy Gametophyte
Sporophyte
Small
Temporary
Parasitic on Gametophyte
Meiosis
in sporangium
sporocytes 2n
Spores 1n
Sporophyte Dominant, Gametophyte Reduced
Gymnosperm
Pine example
Sporophyte
large dominant diploid stage
Gametophyte reduced
Gametophyte
Male
Microgametophyte
Pollen
Female
Megagametophyte
Becomes nutritive tissue
protected by integuments
within ovule
Angiosperm
Lily example
Sporophyte
annual
perennial
intermediate growth
Gametophyte
Male
Microgametophyte
multicellular haploid stage
Pollen grain
immature
matures germinating
Female
Megagametophyte
multicellular haploid individual
Egg one of nuclei cells 8
Independent Gametophyte and Independent Sporophyte
Monilophyta
Polypod Fern example
Gametophyte 1n
Male
Microgametophyte
Antheridium
Sperm
Female
Megagametophyte
Archegonium
Egg
Sporophyte 2n
sporangia
Indusia
Molecules that absorb particular wavelengths of light energy and reflect others
Chlorophyll A
Most abundant
Peak absorbance (nm)
430-660
CH3
Chlorophyll B
Second most abundant
Peak absorbance (nm)
450-650
CHO
Accessory Pigments
Contains:
Caroteniods
Beta Carotene
Benefits:
Broaden absorption spectrum
Sunscreen
Visibility:
Fall
Action Spectrum
shows evidence of accessory pigment
Embedded in Thylakoid membrane
Chloroplast Stroma
Thylakoid Lumen
Oxygen-evolving complex
Photolysis:
Uses light energy to split water
oxygens and protons released
oxygen diffuses out of stomata
protons left behind
THYLAKOID REACTIONS
Products:
Syngamy
Zygote undergoes mitosis
organisms require oxygen in high amounts
survives in extreme conditions lacking oxygen
PRE CHANGE
Many Morphological changes occur as plants adapted to life on land
Eventually becomes independent
venter
