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Early Life and Evolution of Plants - Coggle Diagram
Early Life and Evolution of Plants
Life on Land
Challenges
Vegetative
Survival
Sexual Union
Stebbins 1974
Relatively more CO2
Relatively more CO2 during appearance of land plants
4% O2
Kept tissues thin as internal environment quickly anoxic
Weak Ozone
8-15x higher CO2
Dispersal
Terrestrialization
Occurred 470 Million years ago
Multicellular sporophyte
Retain the zygote & embryo within the female gametophyte
Apical cells with 3 cutting faces allow for 3-dimensional parenchymatous tissue
Embryophytes evolved from algae
Earliest pieces of evidence of Life on land
evidence of spores
Tetrahedral tetrad of spores
Crytospores: likely liverwort
First Macro fossils
Cooksonia Sporophytes
Mid-Late Silurian
425 Ma
Gametophytes Complex:
Conducting elements
Similar to extant liverworts
Stomata
Vascular Plants
Evidence from spores ~443Ma
Diversity exploded in Devonian period (415-360Ma)
Dominant Sporophyte no longer restricted to damper areas
Specialized conducting cells
Evolved from Algae
Charophycean green algae
Streptophyta
This group includes: Embryophyta and Charophytes
Sometimes grow as flat disc very similar to present day liveworts
Major Evolutionary Innovations
Key Innovations
Sporophytes
Evolution of Leaves
Vascular Tissue
Seeds
Stomata
Life Cycle
Sporophyte Generation
#
Gametophyte dominant in early land plants
Sporophyte evolves dominance
Alternation of Generations
Leaves and Stomata
#
Ordovician, many seen by Silurian
Often aerial surface covered with cuticle
All land plants have sporophytes except Liverworts
Vascular Tissue
#
Specialization of Water conducting cells and Food conducting cells
Without these tissues plants are confined to being small and close to the soil
Allows plants to grow tall
Roots
grew a protective cap
Downward growing Rhizomes
Grows away from light
Grows downward
Seed Evolution
#
Gametophyte
Completely dependent on sporophyte
Egg protected by special layers of tissue
Seed Ferns (All are extinct)
Gymnosperm
Naked Seed
Angiosperm
Hidden Seed
Flower Evolution
#
Attraction
Dispersal
Stem Specialization
Coevolution
Life Cycle Evolution
Meiosis
Multicellular Haploid Organism (Gametophyte)
Gametes
Fertilization
Zygote-> Mitotic Divisions of zygote
Mass of Diploid Cells (Simple Sporophyte)
Meiosis of Diploid Cells
Haploid Cells (spores)
Sporophyte Evolution
Algal ancestor
Haplontic (Single Being)
Haplodiplontic (Single double being)
Antithetic Theory (aka Interpolation Theory)
The Interpolation Theory suggests that the sporophyte generation progenated from a haploid, green algal thallus in which repeated mitotic cell divisions of a zygote produced an embryo retained on the thallus and gave rise to the diploid phase (sporophyte)
Heteromorphic Generations
Sporophyte
Short lived
Simple
Gametophyte
Relatively Complex
Persistent
Gametophyte Dominant
Marchantiophyta
Dominant leafy Gametophyte
Temporary diploid Sporophyte
Gametophyte
Dominant Life Stage
Antheridiophore
Male
Antheridia: Contain Sperm
Archegoniophore
Female
Archegonia: Contain eggs
Bryophyta
Minimum Moss Example
Dominant Leafy Gametophyte
Temporary Diploid Sporophyte
Moss Archegonium
Microgametophytes
Antheridium
Male
Sperm
Megagametophytes
Archegonium
Egg
Female
Sporophyte
#
Small, temporary structure
Parasitic on Gametophyte
Meiosis occurs within the sporangium
Spores (1n)
Sporocytes (2n)
Sporophyte Dominant
Lycophyte
Sperm must still swim to egg
Retained within Spore
Heterosporous
Gametophyte
Both male and female develop within spore wall
Small
Microgametophyte
Pollen
Megagametophyte
Protected by integuments
Within an ovule
Becomes nutritive tissue
Sporophyte
Reduction in megasporocytes to 1 per megasporangium
Micro= Male
Heterosporous
Mega= Female
Large dominant diploid stage
Gametophyte reduced to microscopic structures
Angiosperm
Selaginella can be found within Oklahoma
Monilophyta
Polypod Fern for example
Independent Gametophyte
Independent Sporophyte
Gymnosperm
Microgametophyte: No longer restricted to water
Megagametophyte: Protected by integuments
Large persistent diploid
Stomata
Early Evolution
One of the earliest features of land plants
All but liverworts have examples
Small pore bounded by specialized epidermal cells, guard cells
Permit rapid gas exchange in higher plants
Carbon dioxide in
Oxygen out
Control of water loss permit giants among plants
Sporophyte likely the origin of stomata
Aided in spore dispersal
No intercellular space
Lower stomatal frequency
Extant early lineages have stomata that only open
Intercellular Spaces
Pseudostomata
No space
Space filled with fluid with space by cells pulling apart
Stomata Canal (Small air space)
Aid in diffusion of minerals and nutrients
Cell death
Flowering Plants
Monocot (Grasses)
Same direction as epidermal cells
Dumbbell Shape
Eudicot
Kidney-shaped
Random Orietation
Function
Guard cell control
Active metabolic processes
Increase turgor pressure
The force within the cell that pushes the plasma membrane against the cell wall
Moves ions, water followed by osmosis
Hypotonic to hypertonic
Cytoskeleton microfibrils radially oriented
Photosynthetic dependent
Potassium are moved in
Ancestral condition filled chloroplasts
Independent of blue light
Protons are pumped out
Closure at night or under water stress
Provides ATP for potassium pump
Water use efficiency
Derived character
Reduce probability of cavitation
Close pore during water stress
Reduce Transpiration
Maintain hydration
ABA responsive in seed plants
Angiosperms additionally respond to VPD
VPD= Vapor Pressure Deficit
Amount of water loss to carbon gain
Interdeterminate Growth
Trait evolution
Autapomorphy
Character newer than
Homoplasy
Trait gained or lost independently in separate lineages during evolution
Convergent evolution leads to species independently sharing a trait that is different from the trait inferred to have been present in their common ancestor
Synapomorphy
apomorphy shared by two or more taxa
hypothesized to have evolved in their most recent common ancestor
synonymous with homology
Convergence
Independent evolution of a similar trait in two or more taxa
Apomorphy
Derived novel trait
Plesiomorphy
Character older than
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
2D to 3D
Linear growth such as filamentous algae
Only divide at tip
Cytokinesis in a single plane
Leafy Shoot growth in three dimensions
Bifurcate branching
Evolved prior to vascularization
Equal branching: Isotomous
Unequal Branching: Anisotomous
Indeterminacy
Grow continuously
Produce new organs
Produce new tissue
from shoot apex
Vascularization
Evolutionary perspective
Synapomorphy
Cell type varies
All have vascular tissue
Vascular architecturally diverse
Tracheophytes
Lycophytes
Early vascular group
Created towering forests during carboniferous
Xylem
No specialized cells
Poikilohydric
water content changes the moisture in surrounding environment
water-storage extend
They can equilibrate with the relative humidity of the air during drought periods, but then exhibit complete physiological recovery upon rehydration
Stayed small to reduce demand for water
Live in perennially wet substrates (stream sides)
More derived homoiohydric
Hydroids
Water conducting cell
Apomorphic trait to true vascular tissue
Bryophytes
No lignin
Lignin: water transport, mechanical support and resistance to various stresses
Tracheary elements
Dies at maturity
Thickened lignin walls
Phloem
Food conducting cells
Widespread in bryophytes
Breakdown of tonoplast
Mix vacuolar and cytoplasmic contents
Alignment along longitudinal arrays of endoplasmic microtubules
Plastids
Mitochondria
ER Vesicles
Rarely some species have nuclear breakdown
Specialized plasmodesmata in end walls
Features common to sieve cells
Sieve cells & Albuminous cells
Transport of the following:
Photosynthate
Hormones
Electric signals
AC aka: Strasburger cells
Gymnosperms: only earlier lineages with various types including transitional = sieve elements
Sieve area, pores are narrow
Uniform sieve areas
Mostly on ends
Lacks a sieve plate
Sieve tube element features and contents
Living protoplasts at maturity
Few organelles (ER)
Many sieve tube elements together = sieve tube
Callose & callose plugs
Sieve plate
Area with many sieve pores
Usually on end wall
Primary cell wall
Lateral sieve area
P Protein
May help in plugging pores in response to leakage
Plastids
Smooth Endoplasmic Reticulum
Lost ribosomes
Highly folded
Mitochondria
Very few
Forisomes
Legumes
Plugs pores
Companion cell
Branched plasmodesmata
Vacuole
Nucleus
Mitochondria
Plasmodesmata connections
Connected by large quantity of plasmodesmata
One pore in sieve tube area branched into many on companion cell side
Sieve tube and companion cell from same mother cell
Plasmodesmata
A narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication between them.
Phloem differentiation
Callose deposited around terminal of plasmodesmata
Nuclear break down
Cytoplasmic clearing
No ribosomes
Formation of sieve plate & pores
Cell wall thickened
Wood
Environmental Change
Amount of water loss per carbon gained increase after Silurian time period
Carboniferous period greatly drain atmosphere of CO2
Water demand is relatively high
Water transport system energetically efficient (don't starve)
Minimal maintenance = cell death
Transport energy: Minimal
Water filtration close to soil access
Selection pressure for wood
Increased competition
Taller plants
More developed tree canopies
Higher rates of transpiration
More xylem, wider & longer conduits
Likely evolved 5 times
Loss of secondary growth
Monocotyedonae
Arborescent
No secondary growth
First tree
Lepidondrids
Carboniferous
Vascular cambium only divided internally
Archaeopteris
Reproduced via spores
Extant lineages
Lycophytes
Euphyllophyte
Secondary growth
Complex plant development
Growth in girth
Produce secondary
Xylem (wood)
Phloem (inner bark)
Ground tissue (Rays)
Continuous circular ring growth
Annular rings
Xylem secondary cell walls are robust
Phloem is crushed
Ring width determined by season and environment
Alternation of Early and Late wood
Softwood
Tracheids only
Little room for fivers
Gymnosperms
Hardwoods
Vessel elements
Efficiency permits space for fibers
Angiosperms
Vascular Primary tissue arrangement in shoots
Arrangements within a plant
Monocot
Root with pith
Stem without pith
Eudicot
Root without pith
Stem with pith
Key features to Monocots and Eudicots
Root and shoot have different arrangements
Increasing complexity
Led to compartmentalization
Selected for a woody habitat
Plant height increased
Stem diameter increased
3 major stele types
Siphonostele
Ring of phloem, xylem, surrounding pith
Eustele
Strands of phloem & xylem separated by parenchyma
progymnosperms
Most complex
Protostele
Solid vascular strand
Phloem surrounds xylem or interspersed
Earliest
Archs
Based on Xylem maturation
Protoxylem
1st xylem to mature
Usually smaller in diameter
Metaxylem
Develops later
Usually larger in diameter cells
Exarch
Protoxylem outside metaxylem
eg protosteles
Lycophyte
Protostele
Most ancestral type of stem vasculature
Endarch
Protoxylem in middle
eg eustles, atactosteles
Ferns
Siphonostele
Xylem surrounded by phloem
Mesarch
Protoxylem surrounded by metaxylem
eg siphonosteles
