final Flashcards
what is Hubbell’s Unified Theory of Biodiversity and Biogeography
that all species are functionally equivalent and have an equal chance of colonizing an open space
niches are functionally equivalent
offspring and immigrants all compete for open spaces
what is point mutation (v)
per capita speciation rate
how does the absence and presence of niche differences affect a species growth rate
when niche differences are present: growth rate declines with increased abundance
when absent: species abundance has no effect on growth rate
what is a metacommunity
set of communities linked by dispersal pf one or more of their constituent species
what is a regional species pool
set of species found in a region
what is a local species pool
sunset of regional pool found in local community
what are the results of neutral theory in a community
dominance increases are rarer species goes extinct
species diversity in a local community is maintained by immigration
regionally abundant species tend to be locally abundant
what is island biogeography theory
how big an island (or isolated part of mainland) and how far away it is determines the species richness there
what is facilitation (positive interactions)
encounters between organisms that benefit at least one of the individuals and harms neither
can be direct or indirect
what is mutualism
facilitative interaction where both species benefit
how does facilitation change the view of the niche
makes realized niche bigger than fundamental niche
when are positive interactions most common
under harsh environmental conditions
or extreme stress
what is the stress gradient hypothesis
about relative importance of competitive or facilitative interactions changes along a gradient of environmental harshness
competitive interactions should dominate in benign environments
facilitative interactions should become more important in stressful environments
how does relative neighbour effect change with changing environmental effects
increased environmental severity: positive (facilitation)
decreased environmental severity : negative (competitive)
what is the Hairston smith slobidkin hypothesis (HSS)
top down approach
carnivores, having no predators, are limited by food
herbivores are held below carrying capacity by by predators
plants aren’t controlled by herbivores and are abundant
what did Oksanen propose about atrophic levels
biomass at each trophic level should change as potential productivity increases
as potential primary productivity increases the number of possible trophic levels increases
biomass at each trophic level changed depending on number of trophic levels
bottom up approach
what does oksanen predict in a 3 trophic level community
As potential primary productivity increases :
producer biomass increase
herbivore biomass remains constant
carnivore biomass increases
what is a trophic cascade
indirect/direct effects a predator has on the density or behaviour of species in lower trophic levels
how do cascades differ in terrestrial and aquatic systems
weak in terrestrial
variable in aquatic systems
when do cascades only occur
- cascades/top down effects occur only when :
- direct effects are strong
- producer densities are not limited from bottom up
what make strength of predator-prey interactions vary
predator functional response
body size
energetic requirements
herbivore vulnerability
primary producer palatability
what do food chains represent
transfer of energy between trophic levels in a community
what is a trophic level
identifies a species position in the food chain
what trophic level is the base of the food chain
primary producers