extra notes Flashcards
how is symbiosis evolutionarily dynamic?
it can shift between functional types
- e.g. evolution of mycoheterotrophy
what are the 3 main key themes of symbiosis?
- interspecific communication and coevolution
- evolutionary adaptations to a symbiotic lifestyle
- wider implications of symbiosis, such as host communities
what is involved within the theme of interspecific communication and coevolution?(6)
- mycorrhizas symbiosis
- rhizobia symbiosis
- parasitic plants
- pollinators
- sanctions in symbiosis (punishment)
- red queen hypothesis
in myc AM fungus what signals are produced by the host and after the fungus has received these signals and germinated what does it produce?
- strigolactones
- MYC-factors
what signals from the host plant does rhizobia receive and what does it do?
- what does the rhizobia signal back and what does this cause?
alkaloids
induce +ve chemotaxis causing bacteria to move to host roots
- NOD factors causing morphological changes in the root system, particularly root hairs
how long before legumes did AM fungal symbioses evolve?
over 100 million years
what is the underlying important function of the signalling molecule produced by host plants: strigolactones?
allows parasitic plants to eavesdrop in on communication between plant and AM fungi
which plant responds to signals above ground rather than in the soil?
cuscuta detects volatiles from host plant
what do volatile signals do to parasitic plants interactions such as cuscuta?
- cause parasite to grow towards host plant
- help parasite determine quality of host such as its N status
which parasitic plant does not use chemical cues?
Rhinanthus
what can leghaemoglobin do?
move O2 around the plants tissues
what is involved within the theme of evolutionary adaptations to a symbiotic lifestyle? (3)
- specialized structures and physiology: haustoria, arbuscules, domatia
- loss of redundant features
- endosymbiotic theory
what are 3 examples of loss of redundant features?
- chlorophyll from myc heterotrophic orchids + parasitic plants
- leaves from myc heterotrophic orchids + parasitic plants
- genes for free living in Buchnera
what is involved within the theme of wider implications of symbiosis? (6)
- symbionts restructure competitive hierarchy
- parasites steal resources from host
- Rhinanthus minor
- whole communities restructured
- cuscuta
- mutualists: myc can antagonize non myc plant to suppress root hair production
when answering a question on how symbionts influence host community structure what points would you cover? (8)
- define symbiont and host community
- mutualists vs parasites
- active vs passive
- rhinanthus
- behaviour vs nutritional
- endo vs ecto
- competitive hierarchies
- how symbionts restructure
