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
What are trophic cascades?
They are indirect effects that occur when a predator reduced the abundance of its prey, so it cascades down to the lower trophic levels.
ex. causes a prey’s own resources to increase because there are less prey decreasing them
ex 2. wolf>deer>trees/grass - if the wolf is removed, the deer pop increases and the resources decrease
What is top-down control?
It is when predators control the abundance of herbivores.
ex. by adding a predator, it controls other species as herbivores decrease but has positive impact on plants - explains “why the world is green”
What is bottom-up control?
It is when a predator’s abundance is controlled by their resources.
ex. if plants are fertilized, they grow more but there is no increase in herbivores - could perhaps provide more food though
What are meta-analyses?
They are structured analyses of large numbers of data sets that has a goal to discern consistent trends. It uses many different studies and statistically analyzes them together.
ex. is a predator’s effect negative or positive?
Disturbance
It is a physical force, agent, or process, either abiotic or biotic, causing a perturbation or stress, to an ecological component or system. For example, fires, storms, diseases, volcanic eruptions, earthquakes etc.
Disturbances are also responsible for opening up gaps in many kinds of community.
Indirect Effect
Indirect effects are brought especially into focus when the initial removal is carried out for some managerial reason, since the deliberate aim is to solve a problem, not create further, unexpected problems.
