6 - Reach for the Sky Flashcards
Limitations of Bryophytes?
- limited to dry/damp locations near water
- dependant on water for sexual reproduction + poor water transport
Advantages of Sporophytes?
- have vascular tissue so they can get water + nutrients from parent gametophyte
What is parasite theory, in regards to the sporophyte & gametophyte?
-sporophyte “parasitic” on gametophyte
-the capsule of sporophyte (moss) is non-photosynthetic -> but has stomata —> “parasite theory” states that it has stomata to create a flow of water –> ∴ sugars, minerals, etc travel/pulled up seta –> water evaporates & leaves cells –> negative pressure created –> water pulled out of gametophyte —-> via transpiration –> sucks nutrients from gametophytes
-The gametophyte also benefits as its spores success rate is increased by extra height of sporophytes ——> increasing dev. of larger/dominant sporophyte –> which is important in plant evo.
- The conflict between gametophytes & sporophytes may have driven evo. of stomata & xylem
What is the Rhynie Chert?
- a sediment deposit
- containing very well preserved sections of plants
- provided info on their structure & internal anatomy
- resulted in identification of earliest known vascular plants
What is an example of a fungal association & why is it important?
- Mycorrhiza: a fungus closely associated with plant roots
- It has a symbiotic relationship with the plant – fungus gives nutrients – plant gives sugars
- Very important for plant growth – allows nutrient capture over large areas
What is an example of a fungal association & why is it important?
- Mycorrhiza: a fungus closely associated with plant roots
- It has a symbiotic relationship with the plant – fungus gives nutrients – plant gives sugars
- Very important for plant growth – allows nutrient capture over large areas
What are Lycopodiophyta, what are their important features and why are they important?
- One of the oldest known VASCULAR plants
- reproduce by spores -alternation of gens. -leaf-like structures (microphylls)
-sporophyte dominant & photosynthetic -vascular system (Xylem)
-evolved thick stems w/ lignin (using secondary growth) - They evolved into large tree-like structures (due to secondary thickening & roots)
What is primary growth?
(Length) – cell division at a tip (apical meristem) resulting in elongation of tissues
What is secondary growth?
(Thickness) – cell division at cambia (lateral meristem) results in structures becoming thicker
How did the characteristics of Lycopods allow them to become dominant?
-well developed vascular tissue + root systems
–> allowed them to draw water up from soil to great heights, up to 30m tall.
—> great height -> need to support themselves –> resulting in extensive secondary thickening, with production of lignin to strengthen tissues –> this resulted in bark like tissue
-However the vascular tissue was confined to centre of stem, limiting potential for water uptake.
-presence of leaves -> simple in structure -> only possessed single strand of vascular material-> classified as microphylls (=small leaves).
What are the Megaphylls?
“Large Leaf” classification
What are the characteristics of megaphylls?
-branched veins/vascular bundles
–> allows for wider flatter surface (capture more light + more stomata)
–>Better light capture = more photosynthesis -> but hotter (more water loss)
-Low CO2 = need more stomata –> More stomata = cooler leaves –> but more water needed
How did selection pressures counteract water loss and drive the evolution of megaphylls?
-to counteract water loss -> evo. pressure to improve water supply to leaves -> resulting in more vascular tissues
- large quantities of carbon were captured and locked up -> in the form of coal and oil -> so atmospheric CO2 levels fell
Falling CO2 drove evolution of megaphylls —-> into FERNS
What is the scientific name for ferns and what plants are classified as such?
- Ferns = Pteridophyta/Polypodiopsida
- Horsetails, Lycophytes, Shuttlecock, Sori, Rhizomes
What were the important characteristics of ferns and their limitations?
- Megaphylls - Better vascular systems than lycopods
- Herbaceous (can die down & survive as roots for parts of year -> adv. in seasonal climates)
- Shuttlecock morphology -> all leaves grow from central point -> can also spread by producing rhizomes (underground stems) allowing them to spread laterally
- Sori- cluster of sporangia (produce & contain spores on underside of leaf)
Limitations: -still have sensitive gametophyte gen. -don’t have secondary thickening
