17 Flashcards
(28 cards)
what envr challenges do lichens face?
light
cold
fire
what is an effect of developing in regions where light is strong?
heat must be dissipated
how do lichens survive living in an envr where light is strong?
dry out to withstand heat & therefore, the heat won’t negatively affect the algal cell
fungi are resistant to heat
what effect does permafrost have on lichens?
top is dry & bottom is moist b/c permafrost dries out & provides enough moisture so the algal cell can remain living
enter a cryptobiotic state
cryptobiotic state
all measurable metabolic processes stop (reproduction, development & repair) until envr conditions return to being suitable
what effect does fire have on lichens?
permafrost melts
exposes envr to the loss of water
destroys vegetation
eliminates food sources
destroys animal habitats
changes nutrient composition
when do lichens burn?
when substrate or soil is set on fire
what component has a larger dependence on the other?
algal cells have a larger dependence on the lichen than the fungal cells do
what process occurs in the algal component of the lichen?
nitrogen-fixing
describe the formation of a lichen?
fungal hyphae penetrate algal cell wall
clusters of algae meshed within fungal hyphae
what are the thallus components of a fruticose lichen?
algal layer
solid central strand
medulla
cortex
medulla in fruticose lichens
composed of fungal hyphae in assoc with algal cells
what are the thallus components of a foliose lichen?
medulla
Gonidial layer (algal layer)
upper cortex
lower cortex
where do the agal & fungal cells interact?
algal layer
medulla in foliose lichens
fungal layer assoc with upper cortex
how do lichens survive a cold state?
maintain the same moisture as the atm around them through poikilohydric nature
poikilohydric nature
connect water tissue level with that of the envr, coupled with the ability to survive dehydration without physiological damage
how do lichens survive on permanently frozen ground without roots or a cuticle?
acquire nutrients from the atm
secondary compounds
protect against light, excess moisture or parasitism
formed by fungal cells
describe Peltigera
contain green algae & cyanobacteria
what are the mechanisms that lichens use to gain nutrients from the envr?
atm uptake
uptake from below (soil, substrate)
use incoming light
what feature of a lichen enable them to survive in a cold & dry envr?
poikilohydric nature
what feature of apothecia are useful in the survival of lichens?
apothecia are ornamented with cilia which function to maintain an atm of higher humidity, hold moisture in the air
how do the sexual propagules of lichens disperse?
wind
