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Plant Life Cycles and Evolution - Coggle Diagram
Plant Life Cycles and Evolution
Flowers
radil symmetry
irregularity
ovary goes from being superior to inferior over evolutionary time
parts become mroe differentiated
Structure
perfect, complete flower
sepals
green structures on bottom of flower
Protective
all together called calyx
stamens
full of pollen
powdery
anther and filament
anther
4 pockets
microgametophytes here until release
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androceium
petals
located above
sepals
can be highly modified in shape
function is to attreact polinators
pollinator syndrome
wind
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is expens
expensive to produce
all together called corolla
together called a perianth
carpal
stigma
style
ovary
ovules inside locules
here you will findmegagametophyte
can have multiple fused together
highly varied
only in angiosperms do we get this additional protective covering of carpals
only true fruits have fruit flesh derived from a carpal
gymnocium
may have a peduncle
Life Cycle Evolution
Sporophyte Evolution
Algal Progenitor
Haplontic
Zygote automatically underwent meiosis to form 4 haploid cells
Undergo mitosis to form a multicellular haploid individual
specialization occurs within to produce gametes
these gametes fuse in syngamy to for diploid zygote again
Alternation of Generations
Current Land Plants
Haplodiplontic
Multicellular Diploid Sporophyte
Sporophyte Produces Haploid Spores
Spores undergo mitosis to produce haploid multicellular gametophyte
Within gametophyte gametes are produced
Gametes fuse to form diploid zygote
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Antithetic Theory (Interpolation Theory
suggests sporophyte of land plants was inserted into the haplontic life cycle of a green algae
Sporophyte arose when the zygote did not immediately undergo meiosis
This would result in a multicellular diploid stage not seen in the haplontic cycle
Sporophyte became physiologically independent of the gametophyte and eventually became the dominant form
Predictions
Earliest sporophyte and gametophyte generations would have been heteromorphic
Sporophyte relatively short lived and simple while gametophyte would be more complex
Gametophyte Dominant
Earliest Land Plants
Liverworts
Model is Marchantia
Dominant leafy gametophyte
Temporary Diploid Sporophyte
Zygote undergoes mitosis to form multicellular sporophyte
Sporophyte is located in the Archegoniophore
Sporophytes within sporangium of archegoniophore undergo meiosis to form and deploy spores
Spores undergo mitosis to form multicellular haploid stage of the female and male gametophytes
Archegoniophore
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Antheridiophore
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Another example of gametophyte dominant life cycle is
Bryophyta
modern day moss
sporophyte dominant, sporophyte and gametophyte independent
Lycophytes
Selaginella
heterosporous
spores retained inside spore walls
Sperm must still swim to egg
Life cycle
sporophyll grows to sporophyte
sporangia grow along sporophylls
microsporangia
microspores will be released
germination happens entirely within the spore walls of the gamertophyte
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megasporangia
megaspores will be released
gametophytes smalls and within spore wall
Monilophyta
Sporophyte dominant, gametophyte reduced
Gymnosperms
Pine life cycle
zygote undergoes mitosis to form multicellular diploid stage
grows into seeds and disperses
develops into sporophyte
within are strobili
microsporangia
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megasporangia
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Angiosperms
Reduced Gametophyte
Zygote mitotically divides into embryo of a seed
Carpals
within is ovule, containing two layers of integuments to protect the megasporangia
within, megasporocyte undergoes meiosis to form the megaspores
3 of them will be reabsorbed, leaving one behind
megaspore undergoes mitosis to form megagametophyte
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Stamens
has microsporangia (anthers)
within microsporangia, meiosis occurs to turn mircosporocytes into microspores
microspores develop into pollen grains
pollen grains disperse and hopefully reach female stigma
microgametophyte
male multicellular haploid stage
mitosis
dispersal
two sperm travel down pollen tube
megagametophyte
single megaspore undergoes 3 mitotic events
8 nuclei
Seeds (mature ovule containing an embryo)
Origins
ovule
integuments
micropyle
heterospory
differentiation of microspores and megaspores
protection mechanisms
formation of the megasporangium
the megasporangium, which contains the megasporocyte, is enclosed in integuments
megasporocyte unergoes meiosis to produce four megaspores
only one will survive
retained megaspore undergoes mitosis to produce the megagametophyte
develops within the megasporangium
endosporic development provides a protected environment for the gametophyte
fertilization occurs when sperm (microgametes) swims to the egg within the megagametophyte. this results in the formation of an embryo
integuments surrounding the megasporangium evolve into the seed coat, providing additional protection
megagametophyte also serves as a nutrient source for the developing embryo
microgametophyte
originally flagellated sperm
pollen grains
protective "exine"
air bladders for wind dispersal
germinates and grows pollen tube
this tube penetrates the megagamtophyte and delivers sperm to egg, with this sometimes taking an entire year
growth of pollen tube is directed by the synergids of the megagametophyte
generative cell undergoes mitosis to produce two sperm nuclei, while tube nucleus helps control growth of pollen tube
seed components
cotyledons
seeds leaves providing nutrients
gymnosperms have multiple, angiosperms ususally have two
seed coat
formed from integuments, protecting seed
endosperm
specialized nutritive tissue formed from the triploid tissue, providing nourishment to the embryo
types
gymnosperms
seeds often exposed and can have fleshy outer layer
angiosperms
seeds undergo a process called double fertilization
Seeds
Origins
Seed ferns
Gymnosperms
Protogymnosperms
Angiosperms
Earliest Seed
Elkinsia polymorpha
4-5 lobes, fused basal third
360mya
Pseudosporogonites quadrapartitus
Primitive Ovule
lobate integuments
Moresnetia zalesskyi
8-10 lobes fused at chalasa and widely separated
360mya
Enclosed Ovule
Complete enclosure of microsporangium within integument
Stamnostoma huttonense
Ovule evolution
evolved from shoot apex
gymnosperm nucellus apex similar to shoot apex
Innovations
heterospory
protection
integuments
Pollen capture
pollen chamber
micropyle
nucellus
Evolution of the ovule
Heterospory
Megasporangium enclosed in integuments
Retention of megaspores within megasporangium
Reduction of number of megasporocytes in megasporangium to 1
survival of 1 megaspore
Endosporic megagametophyte
Modification of megasporangium apex for microspores or microgametophytes
embryo develop within megagametophyte
Ovule evolution
Gymnosperm
megasporangium is nutritious tissue = nucellus
Nested Doll
Integument
nucellus
megaspore wall
megagametophyte
Archegonium
Egg
Gymnosperm vs. Angiosperm
both single megasporocyte
both single megaspore
1 integument vs. 2 integuments
unique to angiosperms
additional protection of ovary wall
double fertilization
Angiosperm Ovule
2 integuments
megasporangium = nucellus
megasporocyte reduced to one and retained
megagametophyte = egg sac
8 nucleate
3 antipodals
sometimes nutritive
2 polar
becomes endosperm
2 synergids
guide pollen tube
1 egg
Furniculum
