The Green Revolution Flashcards
What did the evolution of photosynthesis result in?
Oxidation of the atmosphere
Where did photosynthesis evolve?
Under the sea
Which clade of organisms first evolved photosynthesis? Then what happened?
- green algae
- land plants evolved
- movement of land to fresh water
What are land plants called?
Embryophytes
What are the two types of seed plants:
- Gymnosperms
- Angiosperms
What are the three types of spore plants?
1) bryophytes
2) lycophytes
3) pterophytes
Which came first, seed plants or spore plants?
Spore plants
Gymnosperms
- produce cones
- are unisexual (both male and female)
Angiosperms
- are floral
- are either male or female
Which kingdom is the green plants?
Viridiplantae
List some of the multicellular green algal ancestors of land plants
- Charales (Chara)
- Coleochaetales (Coleochaetae)
- Zygnematales
List some Zygnematales
- Micrasterias
- Spirogyra
- Zygnema
Which multicellular algae is the most likely phylogenetic ancestor of Viridiplantae?
Zygnematales
What are the bryophytes?
The earliest plants
Traceophytes
Vascular plants (with xyla and phloems)
Lycophytes
- small single veined leaves
- microfils
Pterophytes
Megafils
What is the problem associated with moving from aquatic to terrestrial landscapes?
Need to protect gametes from dessiccation
Describe the key innovations of Viridiplantae
- Archegonia (lost in Gnetales and angiosperms)
- Cuticle (cutin)
- Stomata (not Liverworts)
- Thick-walled ‘trilete’ spores (sporopollenin)
- Vascular tissue (lignified xylem, and phloem)
- Roots and leaves
- Seeds
What are seed plants known as?
Spermatophytes
What percentage of Viridiplantae are angiosperms, how many species is that roughly, and what can we conclude from this?
- 95%
- ~400,000
- angiosperms are highly successful
What is the archegonia?
A flask that protects the egg from desiccation
What is the function of the cutin biopolymer?
It waterproofs the plant
Why are stomata innovative?
They overcome airtight cutin
What is sporopollenin?
Three scars of sporopollenin protect spores from desiccation
What is the largest angiosperm family and what percentage does it represent?
- Orchidaesae
- 10%
Angiosperm haploidy
occurs in just a few cells
Haplontic life cycle meaning
- Mitosis takes place in the haploid generation
- e.g. Coleochaetales/Zygnematales
Diplontic life cycle meaning
- mitosis takes place in the diploid generation
- e.g. humans
Haplo-diplontic life cycle meaning
- mitosis takes place in alternating haploid and diploid generations (‘alternation of generations’)
- as such, the life cycle has two forms
What happens in the haplo- phase on haplo-diplontic life cycle?
- Produces gametes by mitosis
- at this point, the organism is called a gametophyte
What happens in the diplontic phase of the haplo-diplontic life cycle?
- diploid forms of gametophytes fuse
- produces spores (from a sporophyte) by meiosis
Which parts of bryophytes fossilise well?
- cutin
- sporopollen
- lignin
- not the other stuff
Advantages of haplo-diplontic life cycles:
- meiosis is delayed when egg is fertilised, producing an oosphore
- allows survival if condition is not favourable for the release of the next haploid generation
Why is spore production advantageous?
Released into higher levels of air above others - provides competitive advantage
Why is establishment of plant origins tricky?
Early fossil record is very incomplete - only microfossils really exist
What is the classification of the first plant form?
Sporophyte Cooksonia
Of which classification are there no early fossils?
Gametophytes
Describe the sexual reproduction in Chara
1) multicellular megagametangia births large egg cell
2) multicellular microgametangia births small sperm cells
3) fertilisation - zygote becomes a resting ‘oospore’
4) dispersal
5) meiosis - protonema emerges to become new haploid body
What are the egg and sperm cells produced in Chara surrounded by?
Sterile protective cells
What is the ‘oospore’ surrounded by in Chara and what do they do?
- Layer of sterile cells
- Thicken to form a protective layer
Microgametangium aka
Antheridium
Megametangium aka
Archegonium
What is the n number of the oospore
2n
Protonema
- thread-like chain of cells
- earliest stage of gametophyte development
Evolution of the sporophyte
- following fertilisation, zygote undergoes mitosis
- 2n sporophyte is ‘interpolated’ into life cycle
Heterospory
Individuals produce two types of gametophyte (and therefore, spore)
Who exhibits heterospory?
- spermatophores
- some extant Lycophytes and Monilophytes
- many extinct lineages
- a polyphyletic group
Describe the big words associated with egg formation in sporophytes
Megaspores produced in the megasporangia create megagametophytes which produce the egg
Describe the big words associated with sperm formation in sporophytes
Microspores produced in the microsporangia create microgametophytes that produce sperm
Hypothetical first stage in seed evolution
- a line of heterosporous monilophyte ancestors retained their megaspores on the sporophyte
- each megasporangium produces one megaspore (other 3 degenerate)
- after fertilisation, ovule becomes a seed
In seed evolution, the megasporangium becomes the
Ovule
In seed evolution, the microspore, with microgametophyte inside, becomes the
Pollen
Give an example of a seed plant
Pinus sylvestris
In sporophytes, where does fusion occur?
Argegioniophore
What is the sporophyte takeover?
The rise to dominance of the diploid phase
Homospory
Spores produced are all the same - not differentiated into male and female
What type of evolution did heterospory experience?
Convergent
What is endosporic development and why is it advantageous?
- megagametophyte develops partially within the spore coat
- more protection from dessiccation
What does the antheridium need for survival?
Water
What needed to evolve first to facilitate seed evolution?
Heterospory
What does the gametophyte depend on?
The sporophyte for nutrition
What does the sporangium do?
Protects spore
What is the pollination droplet?
The droplet of water that catches the microgametophyte
