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Week 10 Study Questions
Terms in this set (13)
A symbiotic relationship between individuals of different species in which both individuals benefit from the association.
Are mutualisms more likely to occur between species that are closely related or distantly related, and why?
Most mutualisms are between species that are very evolutionarily different from one another. Both are specific niche activities, one species fills the need for another species. (amora eat algae off sharks, sharks need algae eaten to keep themselves clean). Most often something that the other species has no way of doing on it's own.
Describe, in terms of costs and benefits to both partners, why cheating is advantageous, as why partners will try to prevent cheating. Explain how the balance of costs and benefits changes if a partner prevents cheating v. tolerates some amount of cheating.
One species essentially controls the entire interaction and itself benefits from the other species fitness. Each species is able to control the interaction (stop it) and thereby exclude cheaters. Cheating can be tolerated, at least to some extent.
Mutualisms can break down if the benefits accorded to one partner are reduced or if the costs are increased. Give an example of how this does occur, or could occur, in the case of the ant- acacia mutualism discussed in class.
The acacia provides a home and nectar for the ants. The ants are scale insects and the acacia being castrated by the ants weirdly improves the fitness. From the ants, the acacia gets protection from elephants and giraffes eating it.
If ant species identity changed less frequently during a plants' lifetime, how might you expect the balance of this mutualism to shift? What if the order of ant species occupancy was completely random rather than (somewhat) predictable?
The tree would be less protected because it could less readily oust the ants if they aren't doing a good job protecting it. Right now there is a high turnover and the transitions among the ants depend on size and current ant occupant.
When we look at a graph of number of individuals per species v. number of species, why do we see fewer rare species than are actually present? Under what sampling regime do we find the number of rare species that are truly present?
We see fewer rare species than are actually present because if a species is rare it is harder to find and not accounted for on the graph
Ecologists think that Gleason was "right," and that species' geographic distributions are largely a product of individual tolerance. Give 2 reasons we might see strong associations between certain species' distributions.
Gleason and Clements used primarily plant distributions to test their hypothesis on community composition. How might their conclusions have differed if these researchers and their colleagues had mapped distributions of species from disparate trophic levels?
Draw a graph of number of individuals per species v. number of species for 2 communties, one with a low and one with a high Shannon's diversity index.
Would you expect average annual temperature or latitude to be a stronger predictor of global species' richness?
Latitude. Areas in the tropics have a lot more global specie richness rather than areas with a consistent warm annual temperature.
Draw three ways in which speciation and extinction rates might change in the tropics v. temperate region to result in higher species richness in the tropics. For all three ways, give a mechanism that would result in this change.
There is high productivity and energy in the tropics which allows more species to coexist. Predation and parastism rates are higher in tropics, so competitive exclusion is less common. Competitor densities are higher in the tropics, so you must specialize on certain resources. Stable climates mean niches can be narrower and more species can coexist in the tropics.
How would take data to test the intermediate disturbance hypothesis at a single geographic site? How would you take data to test this hypothesis if you could only collect data at one time period?
The intermediate disturbance hypothesis predicts that the highest diversity will occur at levels of moderate disturbance.
On a graph of time since disturbance, and species diversity, draw how the response of long- lived v. short-lived species might differ.
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