Symbiotic Relationships/ Biotic Interactions Flashcards
Describe the differences between ectomycorrhizal and endomycorrhizal fungi.
ectomycorrhizal fungi do not penetrate root cells, but grow in between outer root cortical cells. They grow a Hartig net and are primarily on woody plants and trees
endomycorrhizal fungi are far more common and penetrate root cells and attach to the membrane (but don’t enter the cytoplasm). They are vesicular and arbuscular meaning they have storage and nutrient exchange. They are primarily on herbs and grasses and some trees
Name three types of symbiotic relationships, provide an example of each.
mutualistic (rhizobacteria/ N fixing bacteria and pollinators), commensalism (an orchid on a tree –> does not harm the plant but benefits flower), and parasitic (mistletoe on a pine tree –> harms tree by taking nutrients and water)
Explain why a butterfly pollinating different species of flowers may not be considered a symbiotic relationship whereas a mycorrhizal fungus would be.
The butterfly benefits from the nectar it obtains from the flowers, and while it does benefit the flowers through pollination, there is no close, prolonged relationship between the pollinator and the many different flowers it pollinates. This interaction is therefore not considered a symbiotic relationship. Mycorrhizal fungi attach themselves to the roots of the plant, increasing the surface area for nutrient uptake and exchanging nutrients for carbohydrates produced by the plant. This interaction is a mutually beneficial, prolonged, and close relationship with both the fungus and the plant benefiting so it is considered symbiotic
Symbiotic relationships can be dynamic. Provide an example of how a mutualistic relationship can become parasitic.
when nutrients are plentiful, the once mutualistic relationship between a mycorrhizal fungus and a plant can become parasitic as the fungus no longer benefits the plant, but continues to take resources from it
Which type mycorrhizal fungi forms arbuscles on the cell membranes of roots cells?
endomycorrhiza (glomus spp)
What’s the evolutionary importance of plant/fungi interactions?
when nutrients are limiting, fungi improve growth by increasing surface area allowing them and therefore the plant to absorb more nutrients. Without these interactions, plants likely would not have survived the move from water to land and certain areas of nutrient poor soil
Prior to the Haber-Bosch process, where did most nitrogen available to ecosystems come from?
Rhizobacteria or nitrogen fixing bacteria
Why is the nitrogen in the atmosphere not available to plants directly?
because nitrogen in present in the atmosphere as N2, which is held together by three covalent bonds that require a lot of energy to break, making it unavailable to plants directly.
What is the purpose of leghemoglobin?
leghemoglobin regulates the O2 inside the root nodule of a plant , and by keeping the oxygen levels balanced, it allows nitrogen fixing to be maximized while also allowing aerobic respiration to occur.
Which type of plant is known for symbiotic relationships with Rhizobacter?
pea plants (legumes)
What’s the significance of the Haber-Bosch process?
this process has more than doubled the input of nitrogen to life. It is how we supply more than 200 million tons of ammonia per year, most of which gets converted into fertilizer which has greatly improved crop growth (allowed human population to expand rapidly too)
Describe the consequences of the Haber-Bosch process.
the higher amounts of nitrogen in our atmosphere due to this process is causing environmental problems, especially in aquatic environments because excess nitrogen leads to runoff into water systems, resulting in algae blooms and dead zones
Provide an example of a symbiotic relationship plants use for defense.
plants and parasitoids
some plants will release hormones that attract parasitoids (such as a wasp) that will eat whatever insect is attacking the plant
