ENVS 200 CHAP 9 Flashcards
What is a metapopulation?
It is when a population consists of a collection of subpopulations where each one has a realistic chance both of going extinct and of reappearing again through colonization (connected by immigration/emigration). Metapopulations are stable while subpops are not, the smaller the patch, the smaller the subpop, meaning they are more vulnerable to extinction.
ex. butterflies occupying patches with larval food
What is a patch?
It is an area of land containing a desirable aspect for a species. Where a niche exists to support a species.
What are gaps?
They’re patches within which many species suffer local extinction simultaneously due to disturbance, which is good for colonization. (Sometimes called disturbance-initiated gap)
What are founder-controlled communities?
They have species that are all approximately equivalent in the ability to invade gaps and can hold gaps against all comers during their lifetime (priority effect). This occurs by chance because it’s about who ever can get there first (quick dispersal) and hold the place.
What is the priority effect?
It occurs between competing species in which the species that arrives first at the site is able to hold it against all competing invaders. Over time, other species outcompete founder species
What are dominance-controlled communities?
They have species that are competitively superior to others and an initial colonizer of a patch cannot necessarily maintain its presence there
What is community succession?
It is a sequence of recovery after a disturbance. The early species are good colonizers and fast growers, whereas laster species can tolerate lower resource levels and grow to maturity, eventually outcompeting early species (pioneer>early>mid-successional>climax)
What is is the successional climax stage?
It occurs long after a disturbance, and a community will reach this stage when the most efficient competitors drive out their neighbours
What is primary succession?
It is when an opened up gap has not been previously established or influenced by a community.
ex. glacial retreat, lava flows, etc.
What is secondary succession?
It is when the species of an area have been partially or completely removed, but seeds and spore remain. It’s a recovery after a disturbance.
ex. fire, clear cut, etc.
What is a chronosequence?
It is when a series of communities are used to infer what the succession must have been. Looks at several points to find out how long species have been there (community age).
ex. following the different stages of succession after and during a glacial retreat
What are food webs?
They are a complex web of interactions with other predators, parasites, food sources, and competitors that a pair experiences within its community. It is made up of trophic levels.
ex. predator-prey and grazer-plant
What is a trophic level?
It is a stage of a food chain/web.
ex. primary producer>herbivore>predator
What are direct effects in food webs?
They are very straightforward interactions (1), but can have indirect effects (2).
ex 1. predator eating prey
ex 2. the plant population, other predators and competitors, etc. can feel the effects of this interaction - when superpredator eats mesopredator, it indirectly affects prey
What is a superpredator?
They are predators introduced to an environment that prey on many species, but usually is not prey itself. It is a large secondary predator.
ex. feral cats are not natural, but they now help to keep bird and rat pops in check
