Branches on the Tree of Life DVD Flashcards
Since fungi survive by digesting the molecules of live or decaying plants and animals, how do they avoid digesting their own tissues?
- cell walls of fungi made of polysaccharide, chitin
- chitin is a compound resistant to the enzymes secreted by fungi to digest organic material (cellulose and lignin)
What environmental factor limits the growth and survival of fungi
moisture
- water is necessary to fungus hypha to maintain its own cellular functions and to distribute and take up enzymes and nutrients from the environment
What evidence would biologists use to determine that ancestral chytrids were probably one of the -first groups of fungi to evolve-
- Fossil evidence (in Vendian rocks from Northern Russia) indicates their antiquity
- molecular phylogenies indicate they are near the base of the fungi line of evolution
What advantages do swimming spores provide for chytrids?
Advantages include:
- wide dispersal of asexual spores in aquatic environments
- possibility of ‘homing’ in on food source
- increased genetic mixing during sexual reproduction through wide dispersal of gametes
What are the disadvantages of swimming spores in chytrids?
is the need for water dispersal as a medium
true or false; Chytrids are far more successful in aquatic than terrestrial environments
true
How do fruits protect themselves from invasion of fungi that can start from spores?
- protective skins (banana peels, apple skin, grape peel, etc..)
- chemical growth retardants on the surface of the fruit (orange and grapefruit peels with volatile organics)
- rapid fruit development (strawberries, other berries)
- fruiting in dry, hot weather
- very high sugar content (dates)
- etc…
In terms of ecosystems function, why is it important to have a decomposer fungi
- Fungi (and bacteria) are efficient at recycling dead plant material than are bacteria
- they are key to continued growth and renewal of terrestrial ecosystems
- the energy balance and diversity of all ecosystems, but especially the world’s forests, is strongly influenced by the action of decomposer fungi
Describe the life cycle of Pilobolus. What causes the ejection of the Pilobolus spores, and how are they aimed?
- ) black sporangium; discharged onto plant substrate eg. grass
- ) herbivorous animal eats the substrate
- ) excretion
- ) sporangium germinates; grows mycelium within the excrement
- ) Later, the fungus fruits to produce more spores
- ) Asexual fruiting structure
- transparent stalk
- balloon like subsporangial vesicle - ) On top of this, a single black sporangium spore develops
- ) the sporangiophore has a remarkable ability to orient itself to point directly towards a light source
- ) subsporangial vesicles acts like lens, focusing light via cartenoid pigments deposited near the base of the vesicle
- ) the developing sporangiophore grows such that the maturing sporangium is aimed directly at light (enhances chances that it will attach to vegetation; be eaten by a new host)
- ) When turgor pressure within the subsporangial vesicle builds up to a sufficient level, the sporangium is launched
What is the role of antibiotic compounds in the survival and success of the species of fungi that make these compounds?
Exclusion of competing bacteria and fungi
Where does meiosis occur in an ascomycete fungus? What stage(s) of the ascomycete fungus has two sets of chromosomes?
- like basidiomycete fungi
- ascomycete fungi haploid hyphae unite in growth medium (underground etc) to produce dikaryotic hyphae (hyphae with two separate nuclei)
- Under correct conditions dikaryon eventually forms fruiting bodies
- inside the fruiting body, ascus cells begin to form
- where two separate nuclei of the dikaryon fuse together to form 2N nucleus
- meiosis, 4 daughter nuclei; division of 2N
- daughter nuclei/cells then divide again to produce 8 haploid spores
true or false; the ascus is only 2N for a short while; before meiosis
true
Lichens are often recognized as “pioneer” species in most ecosystems. What does this mean, and why are lichens well-suited to this roll?
- Plants cannot easily grow in the absence of readily available organic matter or soil
(eg. rocky slopes of high mountains, strip mined pits etc..) - Lichens are usually the first species to become established and proliferate- pioneer because:
+tolerant of drying conditions
+require little or no soil
+ low mineral requirements
+ can fix nitrogen from the atmosphere (those with cyanobacteria symbionts)
What is the most significant difference between lichens that harbor only green algae and those that harbor cyanobacteria
Nitrogen fixation in cyanobacteria symbionts
Why are most people very unlikely to see the largest organisms in a forest?
Massive mycorrhizal fungi , much larger than individual trees in terms of mass and occupied space, occur under the ground in many forests
